Sample records for regulating ciita piv

  1. Roles of PU.1 in monocyte- and mast cell-specific gene regulation: PU.1 transactivates CIITA pIV in cooperation with IFN-gamma.

    Ito, Tomonobu; Nishiyama, Chiharu; Nakano, Nobuhiro; Nishiyama, Makoto; Usui, Yoshihiko; Takeda, Kazuyoshi; Kanada, Shunsuke; Fukuyama, Kanako; Akiba, Hisaya; Tokura, Tomoko; Hara, Mutsuko; Tsuboi, Ryoji; Ogawa, Hideoki; Okumura, Ko


    Over-expression of PU.1, a myeloid- and lymphoid-specific transcription factor belonging to the Ets family, induces monocyte-specific gene expression in mast cells. However, the effects of PU.1 on each target gene and the involvement of cytokine signaling in PU.1-mediated gene expression are largely unknown. In the present study, PU.1 was over-expressed in two different types of bone marrow-derived cultured mast cells (BMMCs): BMMCs cultured with IL-3 plus stem cell factor (SCF) and BMMCs cultured with pokeweed mitogen-stimulated spleen-conditioned medium (PWM-SCM). PU.1 over-expression induced expression of MHC class II, CD11b, CD11c and F4/80 on PWM-SCM-cultured BMMCs, whereas IL-3/SCF-cultured BMMCs expressed CD11b and F4/80, but not MHC class II or CD11c. When IFN-gamma was added to the IL-3/SCF-based medium, PU.1 transfectant acquired MHC class II expression, which was abolished by antibody neutralization or in Ifngr(-/-) BMMCs, through the induction of expression of the MHC class II transactivator, CIITA. Real-time PCR detected CIITA mRNA driven by the fourth promoter, pIV, and chromatin immunoprecipitation indicated direct binding of PU.1 to pIV in PU.1-over-expressing BMMCs. PU.1-over-expressing cells showed a marked increase in IL-6 production in response to LPS stimulation in both IL-3/SCF and PWM-SCM cultures. These results suggest that PU.1 overproduction alone is sufficient for both expression of CD11b and F4/80 and for amplification of LPS-induced IL-6 production. However, IFN-gamma stimulation is essential for PU.1-mediated transactivation of CIITA pIV. Reduced expression of mast cell-related molecules and transcription factors GATA-1/2 and up-regulation of C/EBPalpha in PU.1 transfectants indicate that enforced PU.1 suppresses mast cell-specific gene expression through these transcription factors.

  2. IRF-4-mediated CIITA transcription is blocked by KSHV encoded LANA to inhibit MHC II presentation.

    Qiliang Cai


    Full Text Available Peptides presentation to T cells by MHC class II molecules is of importance in initiation of immune response to a pathogen. The level of MHC II expression directly influences T lymphocyte activation and is often targeted by various viruses. Kaposi's sarcoma-associated herpesvirus (KSHV encoded LANA is known to evade MHC class I peptide processing, however, the effect of LANA on MHC class II remains unclear. Here, we report that LANA down-regulates MHC II expression and presentation by inhibiting the transcription of MHC II transactivator (CIITA promoter pIII and pIV in a dose-dependent manner. Strikingly, although LANA knockdown efficiently disrupts the inhibition of CIITA transcripts from its pIII and pIV promoter region, the expression of HLA-DQβ but no other MHC II molecules was significantly restored. Moreover, we revealed that the presentation of HLA-DQβ enhanced by LANA knockdown did not help LANA-specific CD4+ T cell recognition of PEL cells, and the inhibition of CIITA by LANA is independent of IL-4 or IFN-γ signaling but dependent on the direct interaction of LANA with IRF-4 (an activator of both the pIII and pIV CIITA promoters. This interaction dramatically blocked the DNA-binding ability of IRF-4 on both pIII and pIV promoters. Thus, our data implies that LANA can evade MHC II presentation and suppress CIITA transcription to provide a unique strategy of KSHV escape from immune surveillance by cytotoxic T cells.

  3. Transcriptional coactivator CIITA, a functional homolog of TAF1, has kinase activity.

    Soe, Katherine C; Devaiah, Ballachanda N; Singer, Dinah S


    The Major Histocompatibility Complex (MHC) class II transactivator (CIITA) mediates activated immune responses and its deficiency results in the Type II Bare Lymphocyte Syndrome. CIITA is a transcriptional co-activator that regulates γ-interferon-activated transcription of MHC class I and class II genes. It is also a functional homolog of TAF1, a component of the general transcription factor complex TFIID. TAF1 and CIITA both possess intrinsic acetyltransferase (AT) activity that is required for transcription initiation. In response to induction by γ-interferon, CIITA and it's AT activity bypass the requirement for TAF1 AT activity. TAF1 also has kinase activity that is essential for its function. However, no similar activity has been identified for CIITA thus far. Here we report that CIITA, like TAF1, is a serine-threonine kinase. Its substrate specificity parallels, but does not duplicate, that of TAF1 in phosphorylating the TFIID component TAF7, the RAP74 subunit of the general transcription factor TFIIF and histone H2B. Like TAF1, CIITA autophosphorylates, affecting its interaction with TAF7. Additionally, CIITA phosphorylates histone H2B at Ser36, a target of TAF1 that is required for transcription during cell cycle progression and stress response. However, unlike TAF1, CIITA also phosphorylates all the other histones. The identification of this novel kinase activity of CIITA further clarifies its role as a functional homolog of TAF1 which may operate during stress and γ-IFN activated MHC gene transcription.

  4. ZBTB32 is an early repressor of the CIITA and MHC class II gene expression during B cell differentiation to plasma cells.

    Yoon, Hye Suk; Scharer, Christopher D; Majumder, Parimal; Davis, Carl W; Butler, Royce; Zinzow-Kramer, Wendy; Skountzou, Ioanna; Koutsonanos, Dimitrios G; Ahmed, Rafi; Boss, Jeremy M


    CIITA and MHC class II expression is silenced during the differentiation of B cells to plasma cells. When B cell differentiation is carried out ex vivo, CIITA silencing occurs rapidly, but the factors contributing to this event are not known. ZBTB32, also known as repressor of GATA3, was identified as an early repressor of CIITA in an ex vivo plasma cell differentiation model. ZBTB32 activity occurred at a time when B lymphocyte-induced maturation protein-1 (Blimp-1), the regulator of plasma cell fate and suppressor of CIITA, was minimally induced. Ectopic expression of ZBTB32 suppressed CIITA and I-A gene expression in B cells. Short hairpin RNA depletion of ZBTB32 in a plasma cell line resulted in re-expression of CIITA and I-A. Compared with conditional Blimp-1 knockout and wild-type B cells, B cells from ZBTB32/ROG-knockout mice displayed delayed kinetics in silencing CIITA during ex vivo plasma cell differentiation. ZBTB32 was found to bind to the CIITA gene, suggesting that ZBTB32 directly regulates CIITA. Lastly, ZBTB32 and Blimp-1 coimmunoprecipitated, suggesting that the two repressors may ultimately function together to silence CIITA expression. These results introduce ZBTB32 as a novel regulator of MHC-II gene expression and a potential regulatory partner of Blimp-1 in repressing gene expression.

  5. Molecular Cloning, Characterization, and Anti-avian Pathogenic Escherichia coli Innate Immune Response of the Cherry Valley Duck CIITA Gene

    Rong Li


    Full Text Available Class II major histocompatibility complex (MHC-II transactivator (CIITA is a member of the pattern recognition receptor in cytoplasm, which is involved in host innate immune responses. In this study, the full-length cDNA of Cherry Valley duck CIITA (duCIITA was cloned from the spleen of healthy Cherry Valley ducks for the first time. The CDs of duCIITA have 3648 bp and encode 1215 amino acids. The homology analysis of CIITAs amino acid sequence showed that the duCIITA has the highest identity with the Anas platyrhynchos (94.9%, followed by Gallus gallus and Meleagris gallopavo. Quantitative real-time PCR analysis indicated that duCIITA mRNA has a broad expression level in healthy Cherry Valley duck tissues. It was highly expressed in the lung and cerebellum, and lowly expressed in the rectum and esophagus. After the avian pathogenic Escherichia coli (APEC O1K1 infection, the ducks exhibited the typical clinical symptoms, and a severe fibrinous exudate in the heart and liver surface was observed. Meanwhile, a significant up-regulation of duCIITA was detected in the infected liver. The inflammatory cytokines IL-1β, IL-6, and IL-8 have a significant up-regulation in the infected liver, spleen and brain. In addition, knockdown of the duCIITA reduces antibacterial activity and inflammatory cytokine production of the duck embryo fibroblast cells. Our research is the first study of the cloning, tissue distribution, and antibacterial immune responses of duCIITA, and these findings imply that duCIITA was an important receptor, which was involved in the early stage of the antibacterial innate immune response to APEC O1K1 infection of Cherry Valley duck.

  6. Repression of CIITA by the Epstein-Barr virus transcription factor Zta is independent of its dimerization and DNA binding.

    Balan, Nicolae; Osborn, Kay; Sinclair, Alison J


    Repression of the cellular CIITA gene is part of the immune evasion strategy of the γherpes virus Epstein-Barr virus (EBV) during its lytic replication cycle in B-cells. In part, this is mediated through downregulation of MHC class II gene expression via the targeted repression of CIITA, the cellular master regulator of MHC class II gene expression. This repression is achieved through a reduction in CIITA promoter activity, initiated by the EBV transcription and replication factor, Zta (BZLF1, EB1, ZEBRA). Zta is the earliest gene expressed during the lytic replication cycle. Zta interacts with sequence-specific elements in promoters, enhancers and the replication origin (ZREs), and also modulates gene expression through interaction with cellular transcription factors and co-activators. Here, we explore the requirements for Zta-mediated repression of the CIITA promoter. We find that repression by Zta is specific for the CIITA promoter and can be achieved in the absence of other EBV genes. Surprisingly, we find that the dimerization region of Zta is not required to mediate repression. This contrasts with an obligate requirement of this region to correctly orientate the DNA contact regions of Zta to mediate activation of gene expression through ZREs. Additional support for the model that Zta represses the CIITA promoter without direct DNA binding comes from promoter mapping that shows that repression does not require the presence of a ZRE in the CIITA promoter.

  7. Role of PU.1 in MHC Class II Expression via CIITA Transcription in Plasmacytoid Dendritic Cells.

    Miura, Ryosuke; Kasakura, Kazumi; Nakano, Nobuhiro; Hara, Mutsuko; Maeda, Keiko; Okumura, Ko; Ogawa, Hideoki; Yashiro, Takuya; Nishiyama, Chiharu


    The cofactor CIITA is a master regulator of MHC class II expression and several transcription factors regulating the cell type-specific expression of CIITA have been identified. Although the MHC class II expression in plasmacytoid dendritic cells (pDCs) is also mediated by CIITA, the transcription factors involved in the CIITA expression in pDCs are largely unknown. In the present study, we analyzed the role of a hematopoietic lineage-specific transcription factor, PU.1, in CIITA transcription in pDCs. The introduction of PU.1 siRNA into mouse pDCs and a human pDC cell line, CAL-1, reduced the mRNA levels of MHC class II and CIITA. When the binding of PU.1 to the 3rd promoter of CIITA (pIII) in CAL-1 and mouse pDCs was analyzed by a chromatin immunoprecipitation assay, a significant amount of PU.1 binding to the pIII was detected, which was definitely decreased in PU.1 siRNA-transfected cells. Reporter assays showed that PU.1 knockdown reduced the pIII promoter activity and that three Ets-motifs in the human pIII promoter were candidates of cis-enhancing elements. By electrophoretic mobility shift assays, it was confirmed that two Ets-motifs, GGAA (-181/-178) and AGAA (-114/-111), among three candidates, were directly bound with PU.1. When mouse pDCs and CAL-1 cells were stimulated by GM-CSF, mRNA levels of PU.1, pIII-driven CIITA, total CIITA, MHC class II, and the amount of PU.1 binding to pIII were significantly increased. The GM-CSF-mediated up-regulation of these mRNAs was canceled in PU.1 siRNA-introduced cells. Taking these results together, we conclude that PU.1 transactivates the pIII through direct binding to Ets-motifs in the promoter in pDCs.

  8. Degradation, Promoter Recruitment and Transactivation Mediated by the Extreme N-Terminus of MHC Class II Transactivator CIITA Isoform III.

    Yves B Beaulieu

    Full Text Available Multiple relationships between ubiquitin-proteasome mediated protein turnover and transcriptional activation have been well documented, but the underlying mechanisms are still poorly understood. One way to induce degradation is via ubiquitination of the N-terminal α-amino group of proteins. The major histocompatibility complex (MHC class II transactivator CIITA is the master regulator of MHC class II gene expression and we found earlier that CIITA is a short-lived protein. Using stable and transient transfections of different CIITA constructs into HEK-293 and HeLa cell lines, we show here that the extreme N-terminal end of CIITA isoform III induces both rapid degradation and transactivation. It is essential that this sequence resides at the N-terminal end of the protein since blocking of the N-terminal end with an epitope-tag stabilizes the protein and reduces transactivation potential. The first ten amino acids of CIITA isoform III act as a portable degron and transactivation sequence when transferred as N-terminal extension to truncated CIITA constructs and are also able to destabilize a heterologous protein. The same is observed with the N-terminal ends of several known N-terminal ubiquitination substrates, such as Id2, Cdt1 and MyoD. Arginine and proline residues within the N-terminal ends contribute to rapid turnover. The N-terminal end of CIITA isoform III is responsible for efficient in vivo recruitment to the HLA-DRA promoter and increased interaction with components of the transcription machinery, such as TBP, p300, p400/Domino, the 19S ATPase S8, and the MHC-II promoter binding complex RFX. These experiments reveal a novel function of free N-terminal ends of proteins in degradation-dependent transcriptional activation.

  9. Repression of allo-cell transplant rejection through CIITA ribonuclease P+ hepatocyte

    Rong Guo; Ping Zou; Hua-Hua Fan; Feng Gao; Qing-Xin Shang; Yi-Lin Cao; Hua-Zhong Lu


    AIM: Allo-cell transplant rejection and autoimmune responses were associated with the presence of class Ⅱmajor histocompatibility complex (MHC Ⅱ) molecules on cells.This paper studied the effect of Ribonuclease P (RNase P)against CIITA, which was a major regulator of MHCII molecules, on repressing the expression of MHCII molecules on hepatocyte.METHODS: M1-RNA is the catalytic RNA subunit of RNase P from Escherichia coli. It were constructed that M1-RNA with guide sequences (GS) recognizing the 452, 3408 site of CIITA by PCR from pTK117 plasmid, then were cloned into the EcoRI/Bg/II or EcoR//SalIsite of vector psNAV (osNAV-M1-452-GS, psNAV-M1-3408-GS) respectively. The target mould plate (3176-3560) of CIITA was obtained from Raji cell by RT-PCR, and then inserted into the XhoI/EcoRIof pGEM-7zf(+) plasmid (pGEM-3176). These recombinant plasmids were screened out by sequence analysis. psNAV-M 1-452-GS, psNAV-M1-3408-GS and its target RNA pGEM-3176 were transcribed and then mixed up and incubated in vitro. It showed that M1-3408-GS could exclusively cleave target RNA that formed a base pair with the GS. Stable transfectants of hepatocyte cell line with psNAVl-M1-3408-GS were tested for expression of class Ⅱ MHC through FCM, for mRNA abundance of MHCII, Ii and CIITA by RTPCR., for the level of IL-2 mRNA on T cell by mixed lymphocyte reaction.RESULTS: When induced with recombinant human interferon-gamma (IFN-γ), the expression of HLA-DR, -DP,-DQ on psNAV-M1-3408-GS+ hepatocyte was reduced 83.27 %, 88.93 %, 58.82 % respectively, the mRNA contents of CIITA, HLA-DR, -DP, -DQ and Ii decreased significantly.While T cell expressed less IL-2 mRNA in the case of psNAV-M1-3408-GS+ hepatocyte.CONCLUSION: The Ribonuclease P against CIITA-M1-3408-GS could effectively induce antigen-specific tolerance through cleaving CIITA. These results provided insight into the future application of M1-3408-GS as a new nucleic acid drug against allo-transplantation rejection and

  10. Downregulation of class II transactivator (CIITA) expression by synthetic cannabinoid CP55,940.

    Gongora, Celine; Hose, Stacey; O'Brien, Terrence P; Sinha, Debasish


    Cannabinoid receptors are known to be expressed in microglia; however, their involvement in specific aspects of microglial immune function has not been demonstrated. Many effects of cannabinoids are mediated by two G-protein coupled receptors, designated CB1 and CB2. We have shown that the CB1 receptor is expressed in microglia that also express MHC class II antigen (J. Neuroimmunol. 82 (1998) 13-21). In our present study, we have analyzed the effect of cannabinoid agonist CP55,940 on MHC class II expression on the surface of IFN-gamma induced microglial cells by flow cytometry. CP55,940 blocked the class II MHC expression induced by IFN-gamma. It has been shown that the regulation of class II MHC genes occurs primarily at the transcriptional level, and a non-DNA binding protein, class II transactivator (CIITA), has been shown to be the master activator for class II transcription. We find that mRNA levels of CIITA are increased in IFN-gamma induced EOC 20 microglial cells and that this increase is almost entirely eliminated by the cannabinoid agonist CP55,940. These data suggests that cannabinoids affect MHC class II expression through actions on CIITA at the transcriptional level.

  11. Interaction analysis between HLA-DRB1 shared epitope alleles and MHC class II transactivator CIITA gene with regard to risk of rheumatoid arthritis.

    Marcus Ronninger

    Full Text Available HLA-DRB1 shared epitope (SE alleles are the strongest genetic determinants for autoantibody positive rheumatoid arthritis (RA. One of the key regulators in expression of HLA class II receptors is MHC class II transactivator (CIITA. A variant of the CIITA gene has been found to associate with inflammatory diseases.We wanted to explore whether the risk variant rs3087456 in the CIITA gene interacts with the HLA-DRB1 SE alleles regarding the risk of developing RA. We tested this hypothesis in a case-control study with 11767 individuals from four European Caucasian populations (6649 RA cases and 5118 controls.We found no significant additive interaction for risk alleles among Swedish Caucasians with RA (n = 3869, attributable proportion due to interaction (AP = 0.2, 95%CI: -0.2-0.5 or when stratifying for anti-citrullinated protein antibodies (ACPA presence (ACPA positive disease: n = 2945, AP = 0.3, 95%CI: -0.05-0.6, ACPA negative: n = 2268, AP = -0.2, 95%CI: -1.0-0.6. We further found no significant interaction between the main subgroups of SE alleles (DRB1*01, DRB1*04 or DRB1*10 and CIITA. Similar analysis of three independent RA cohorts from British, Dutch and Norwegian populations also indicated an absence of significant interaction between genetic variants in CIITA and SE alleles with regard to RA risk.Our data suggest that risk from the CIITA locus is independent of the major risk for RA from HLA-DRB1 SE alleles, given that no significant interaction between rs3087456 and SE alleles was observed. Since a biological link between products of these genes is evident, the genetic contribution from CIITA and class II antigens in the autoimmune process may involve additional unidentified factors.

  12. Multiple sclerosis susceptibility in a Brazilian sample, HLA and CIITA genes

    Eduardo Ribeiro Paradela


    Full Text Available Introduction: The multiple sclerosis (MS is a chronic disease of the central nervous system that affects mainly young adults. This disease is characterized by the spread of demyelinating lesions in time and space. This condition may be influenced by genetic factors as heterogeneity, incomplete penetrance, polygenic inheritance and epigenetic factors, which makes this complex disease a challenge for geneticists. Objectives: The aim of this study was to investigate the association between HLA alleles from DQA1, DQB1 and DRB1 loci (6p21.3, genetic polymorphisms -168A/G (rs3087456 and +1614 G/C (rs4774 in the CIITA gene (16p13 and susceptibility to MS in a miscegenated sample from Rio de Janeiro state, RJ, Brazil. Method: DNA samples from 52 patients with relapsing remitting multiple sclerosis (MSRR [21 males (40.38% and 31 females (59.62%] and 116 healthy controls [46 males (39.65% and 70 females (60.35%] matched by race, sex and age were analyzed by techniques of PCR, SSP-PCR, electrophoresis and DNA sequencing. Results: A significant association between MS and HLA-DRB1*15:01 allele was observed [p value=.002; Odds Ratio (OR=3.2], especially in women (p=.001; OR=4.9, which remained statistically significant after Bonferroni correction. Furthermore, it was observed that the polymorphism +1614 G/C, “C/C” profile, in association with the allele DRB1*15:01 influences the increased susceptibility to MS in women (p=.029; OR=5.6. In addition, it was observed that the "G/G" profile in CIITA polymorphism +1614G/C may be associated with the resistance to MS (p=.02; OR=0.23, as well as HLA-DRB1*11:02 (p=.02, OR=0.5. The HLA-DQB1*06:02 allele also has been implicated as a possible susceptibility factor for MS (p=.02; OR=1.8, data not confirmed after Bonferronís correction. Conclusion: Together, these results reinforce the polygenic nature of MS, and proposed that the CIITA gene, which is the regulator of the expression of HLA-D, is an additive factor to

  13. Advances in tomographic PIV

    Novara, M.


    This research deals with advanced developments in 3D particle image velocimetry based on the tomographic PIV technique (Tomo-PIV). The latter is a relatively recent measurement technique introduced by Elsinga et al. in 2005, which is based on the tomographic reconstruction of particle tracers in thr

  14. Effects of CIITA antisense RNA on the expression of HLA class Ⅱ molecules


    To study the effect of the major histocompatibility complex class Ⅱ (MHCⅡ) transactivator (CIITA) antisense RNA on the expression of the human leukemia (HLA) class Ⅱ molecules, 5′ end cDNA sequence of CIITA gene was cloned, and antisense RNA expression vector pcDNA-Ⅱ was constructed. HeLa cells transfected with pcDNA-Ⅱ and pcDNA3 were induced by IFN-g for 3 d. The expression of HLA class Ⅱ molecules on HeLa/pcDNA-Ⅱ cells was significantly decreased, while it has no effect on the expression of HLA class Ⅰ molecules. This result suggests that the CIITA antisense RNA can inhibit the expression of HLA class Ⅱ molecules in HeLa cells. It also implies a promising approach to generate immune tolerance in graft transplantation.

  15. Class II transactivator (CIITA enhances cytoplasmic processing of HIV-1 Pr55Gag.

    Kristen A Porter

    Full Text Available BACKGROUND: The Pr55(gag (Gag polyprotein of HIV serves as a scaffold for virion assembly and is thus essential for progeny virion budding and maturation. Gag localizes to the plasma membrane (PM and membranes of late endosomes, allowing for release of infectious virus directly from the cell membrane and/or upon exocytosis. The host factors involved in Gag trafficking to these sites are largely unknown. Upon activation, CD4+ T cells, the primary target of HIV infection, express the class II transcriptional activator (CIITA and therefore the MHC class II isotype, HLA-DR. Similar to Gag, HLA-DR localizes to the PM and at the membranes of endosomes and specialized vesicular MHC class II compartments (MIICs. In HIV producer cells, transient HLA-DR expression induces intracellular Gag accumulation and impairs virus release. METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrate that both stable and transient expression of CIITA in HIV producer cells does not induce HLA-DR-associated intracellular retention of Gag, but does increase the infectivity of virions. However, neither of these phenomena is due to recapitulation of the class II antigen presentation pathway or CIITA-mediated transcriptional activation of virus genes. Interestingly, we demonstrate that CIITA, apart from its transcriptional effects, acts cytoplasmically to enhance Pr160(gag-pol (Gag-Pol levels and thereby the viral protease and Gag processing, accounting for the increased infectivity of virions from CIITA-expressing cells. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that CIITA enhances HIV Gag processing, and provides the first evidence of a novel, post-transcriptional, cytoplasmic function for a well-known transactivator.

  16. CIITA enhances HIV-1 attachment to CD4+ T cells leading to enhanced infection and cell depletion.

    Porter, Kristen A; Kelley, Lauren N; Nekorchuk, Michael D; Jones, James H; Hahn, Amy B; de Noronha, Carlos M C; Harton, Jonathan A; Duus, Karen M


    Activated CD4(+) T cells are more susceptible to HIV infection than resting T cells; the reason for this remains unresolved. Induction of CIITA and subsequent expression of the MHC class II isotype HLA-DR are hallmarks of CD4(+) T cell activation; therefore, we investigated the role of CIITA expression in T cells during HIV infection. CIITA-expressing SupT1 cells display enhanced virion attachment in a gp160/CD4-dependent manner, which results in increased HIV infection, virus release, and T cell depletion. Although increased attachment and infection of T cells correlated with HLA-DR surface expression, Ab blocking, transient expression of HLA-DR without CIITA, and short hairpin RNA knockdown demonstrate that HLA-DR does not directly enhance susceptibility of CIITA-expressing cells to HIV infection. Further analysis of the remaining MHC class II isotypes, HLA-DP and HLA-DQ, MHC class I isotypes, HLA-A, HLA-B, and HLA-C, and the class II Ag presentation genes, invariant chain and HLA-DM, demonstrate that these proteins likely do not contribute to CIITA enhancement of HIV infection. Finally, we demonstrate that in activated primary CD4(+) T cells as HLA-DR/CIITA expression increases there is a corresponding increase in virion attachment. Overall, this work suggests that induction of CIITA expression upon CD4(+) T cell activation contributes to enhanced attachment, infection, virus release, and cell death through an undefined CIITA transcription product that may serve as a new antiviral target.

  17. Regulation of levels of serum antibodies to ryegrass pollen allergen Lol pIV by an internal image anti-idiotypic monoclonal antibody.

    Zhou, E M; Kisil, F T


    A murine monoclonal anti-idiotypic antibody (anti-Id), designated B1/1, was produced against an idiotope of a murine antibody (mAb91), which recognizes the epitope, site A, of allergen Lol pIV, one of the major groups of allergens in ryegrass (Lolium perenne) pollen. The ability of B1/1 to modulate the antibody responses to Lol pIV was investigated in murine model systems. In the first system, B1/1-keyhole limpet haemocyanin (KLH) conjugate was administered to treat three different strains of mice (C57BL/6, BALB/c and C3H). In the second and third model systems, a solution of B1/1 in phosphate-buffered saline (PBS) was used to treat syngeneic BALB/c mice at various doses and time intervals, respectively. The treatment with either form of B1/1, administered at doses ranging from 100 ng to 100 micrograms mouse, resulted in a reduction of the levels of the antibodies to Lol pIV. In particular, the level of IgE antibodies to Lol pIV was greatly reduced. The administration of a single intravenous (i.v.) injection of a solution of B1/1 8 weeks prior to the challenge with Lol pIV was still effective in reducing the level of antibodies to the allergen. Moreover, the level of antibodies to Lol pIV that expressed the idiotope mAb91 was also markedly decreased. By contrast, it was observed that the level of antibodies to Lol pIV in mice pretreated with B1/1 in PBS at a dose of 10 ng/mouse increased (albeit slightly) compared to that in mice treated with control mAb. These experimental models lend themselves for investigating the mechanism(s) by which an anti-Id modulates antibody responses to a grass pollen allergen.

  18. PIV Logon Configuration Guidance

    Lee, Glen Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    This document details the configurations and enhancements implemented to support the usage of federal Personal Identity Verification (PIV) Card for logon on unclassified networks. The guidance is a reference implementation of the configurations and enhancements deployed at the Los Alamos National Laboratory (LANL) by Network and Infrastructure Engineering – Core Services (NIE-CS).

  19. PIV Measurements in Pumps


    8. Fachtagung, 12.-14. Sept. 2000, Freising/ Weihenstephan. [5] Chow, Y., Katz , J., Uzol, O., Meneveau, Ch. (2002): An Investigation of Axial...Skovlunde, Denmark. [7] Dantec Measurement Technology A/S (2002): FlowMap. 3D-PIV System. 5th ed., 2002 Skovlunde, Denmark. [8] Friedrichs , J...Laser-two-focus velocimetry. AGARD-CP-399, paper 7. [17] Uzol, O., Chow, Y.-C., Katz , J., Meneveau, C. (2002): Unobstracted particle image velocimetry

  20. PIV uncertainty propagation

    Sciacchitano, Andrea; Wieneke, Bernhard


    This paper discusses the propagation of the instantaneous uncertainty of PIV measurements to statistical and instantaneous quantities of interest derived from the velocity field. The expression of the uncertainty of vorticity, velocity divergence, mean value and Reynolds stresses is derived. It is shown that the uncertainty of vorticity and velocity divergence requires the knowledge of the spatial correlation between the error of the x and y particle image displacement, which depends upon the measurement spatial resolution. The uncertainty of statistical quantities is often dominated by the random uncertainty due to the finite sample size and decreases with the square root of the effective number of independent samples. Monte Carlo simulations are conducted to assess the accuracy of the uncertainty propagation formulae. Furthermore, three experimental assessments are carried out. In the first experiment, a turntable is used to simulate a rigid rotation flow field. The estimated uncertainty of the vorticity is compared with the actual vorticity error root-mean-square, with differences between the two quantities within 5-10% for different interrogation window sizes and overlap factors. A turbulent jet flow is investigated in the second experimental assessment. The reference velocity, which is used to compute the reference value of the instantaneous flow properties of interest, is obtained with an auxiliary PIV system, which features a higher dynamic range than the measurement system. Finally, the uncertainty quantification of statistical quantities is assessed via PIV measurements in a cavity flow. The comparison between estimated uncertainty and actual error demonstrates the accuracy of the proposed uncertainty propagation methodology.

  1. Association of EVI5 rs11808092, CD58 rs2300747, and CIITA rs3087456 polymorphisms with multiple sclerosis risk: A meta-analysis

    Jiahe Liu


    Conclusions: The mutant alleles of EVI5 rs11808092 polymorphism may increase the susceptibility to MS while those of CD58 rs2300747 polymorphism may decrease MS risk. In addition, CIITA rs3087456 polymorphism might not be associated with MS.

  2. Fuzzy Logic Enhanced Digital PIV Processing Software

    Wernet, Mark P.


    Digital Particle Image Velocimetry (DPIV) is an instantaneous, planar velocity measurement technique that is ideally suited for studying transient flow phenomena in high speed turbomachinery. DPIV is being actively used at the NASA Glenn Research Center to study both stable and unstable operating conditions in a high speed centrifugal compressor. Commercial PIV systems are readily available which provide near real time feedback of the PIV image data quality. These commercial systems are well designed to facilitate the expedient acquisition of PIV image data. However, as with any general purpose system, these commercial PIV systems do not meet all of the data processing needs required for PIV image data reduction in our compressor research program. An in-house PIV PROCessing (PIVPROC) code has been developed for reducing PIV data. The PIVPROC software incorporates fuzzy logic data validation for maximum information recovery from PIV image data. PIVPROC enables combined cross-correlation/particle tracking wherein the highest possible spatial resolution velocity measurements are obtained.

  3. Tomographic PIV: principles and practice

    Scarano, F.


    A survey is given of the major developments in three-dimensional velocity field measurements using the tomographic particle image velocimetry (PIV) technique. The appearance of tomo-PIV dates back seven years from the present review (Elsinga et al 2005a 6th Int. Symp. PIV (Pasadena, CA)) and this approach has rapidly spread as a versatile, robust and accurate technique to investigate three-dimensional flows (Arroyo and Hinsch 2008 Topics in Applied Physics vol 112 ed A Schröder and C E Willert (Berlin: Springer) pp 127-54) and turbulence physics in particular. A considerable number of applications have been achieved over a wide range of flow problems, which requires the current status and capabilities of tomographic PIV to be reviewed. The fundamental aspects of the technique are discussed beginning from hardware considerations for volume illumination, imaging systems, their configurations and system calibration. The data processing aspects are of uppermost importance: image pre-processing, 3D object reconstruction and particle motion analysis are presented with their fundamental aspects along with the most advanced approaches. Reconstruction and cross-correlation algorithms, attaining higher measurement precision, spatial resolution or higher computational efficiency, are also discussed. The exploitation of 3D and time-resolved (4D) tomographic PIV data includes the evaluation of flow field pressure on the basis of the flow governing equation. The discussion also covers a-posteriori error analysis techniques. The most relevant applications of tomo-PIV in fluid mechanics are surveyed, covering experiments in air and water flows. In measurements in flow regimes from low-speed to supersonic, most emphasis is given to the complex 3D organization of turbulent coherent structures.

  4. Tomographic PIV: particles versus blobs

    Champagnat, Frédéric; Cornic, Philippe; Cheminet, Adam; Leclaire, Benjamin; Le Besnerais, Guy; Plyer, Aurélien


    We present an alternative approach to tomographic particle image velocimetry (tomo-PIV) that seeks to recover nearly single voxel particles rather than blobs of extended size. The baseline of our approach is a particle-based representation of image data. An appropriate discretization of this representation yields an original linear forward model with a weight matrix built with specific samples of the system’s point spread function (PSF). Such an approach requires only a few voxels to explain the image appearance, therefore it favors much more sparsely reconstructed volumes than classic tomo-PIV. The proposed forward model is general and flexible and can be embedded in a classical multiplicative algebraic reconstruction technique (MART) or a simultaneous multiplicative algebraic reconstruction technique (SMART) inversion procedure. We show, using synthetic PIV images and by way of a large exploration of the generating conditions and a variety of performance metrics, that the model leads to better results than the classical tomo-PIV approach, in particular in the case of seeding densities greater than 0.06 particles per pixel and of PSFs characterized by a standard deviation larger than 0.8 pixels.

  5. Practical Considerations for Simultaneous LDV & PIV Measurements

    Pothos, Stamatios; Boomsma, Aaron; Troolin, Dan


    Simultaneous LDV and PIV measurements are useful for validation experiments and when correlating high temporal resolution measurements with large structures of the flow. Performing simultaneous LDV and PIV measurements can be a challenging task due to the differences in temporal and spatial resolution of each technique, as well as requirements for adequate signal. Even so, simultaneous hot-wire and PIV measurements is even more difficult. Unlike hot-wire, LDV is a non-intrusive technique that is unaffected by PIV laser light-sheet heating. Furthermore, hot-wire measurements are adversely affected by seeding particles in the flow required for PIV. In the present study, we discuss several practical considerations for performing simultaneous LDV and PIV measurements. We completed two separate experiments, each with different seeding densities, flow velocities, and working fluids. With these data sets, we studied the effects of temporal and spatial interpolation, up/down sampling, PIV window size and overlap on the simultaneous signals.

  6. Demonstration of PIV in a Transonic Compressor

    Wernet, Mark P.


    Particle Imaging Velocimetry (PIV) is a powerful measurement technique which can be used as an alternative or complementary approach to Laser Doppler Velocimetry (LDV) in a wide range of research applications. PIV data are measured simultaneously at multiple points in space, which enables the investigation of the non-stationary spatial structures typically encountered in turbomachinery. Many of the same issues encountered in the application of LDV techniques to rotating machinery apply in the application of PIV. Preliminary results from the successful application of the standard 2-D PIV technique to a transonic axial compressor are presented. The lessons learned from the application of the 2-D PIV technique will serve as the basis for applying 3-component PIV techniques to turbomachinery.


    Iwase, H; Ekser, B; Satyananda, V; Zhou, H; Hara, H; Bajona, P; Wijkstrom, M; Bhama, JK; Long, C; Veroux, M; Wang, Y; Dai, Y; Phelps, C; Ayares, D; Ezzelarab, MB; Cooper, DKC


    Background In the pig-to-nonimmunosuppressed baboon artery patch model, a graft from an α1,3-galactosyltransferase gene-knockout pig transgenic for human CD46 (GTKO/CD46) induces a significant adaptive immune response (elicited anti-pig antibody response, increase in T cell proliferation on MLR, cellular infiltration of the graft), which is effectively prevented by anti-CD154mAb-based therapy. Methods As anti-CD154mAb is currently not clinically applicable, we evaluated whether it could be replaced by CD28/B7 pathway blockade or by blockade of both pathways (using belatacept+anti-CD40mAb [2C10R4]). We further investigated whether a patch from a GTKO/CD46 pig with a mutant human MHC class II transactivator (CIITA-DN) gene would allow reduction in the immunosuppressive therapy administered. Results When grafts from GTKO/CD46 pigs were transplanted with blockade of both pathways, a minimal or insignificant adaptive response was documented. When a GTKO/CD46/CIITA-DN graft was transplanted, but no immunosuppressive therapy was administered, a marked adaptive response was documented. In the presence of CD28/B7 pathway blockade (abatacept or belatacept), there was a weak adaptive response that was diminished when compared with that to a GTKO/CD46 graft. Blockade of both pathways prevented an adaptive response. Conclusion Although expression of the mutant MHC CIITA-DN gene was associated with a reduced adaptive immune response when immunosuppressive therapy was inadequate, when blockade of both the CD40/CD154 and CD28/B7 pathways was present, the response even to a GTKO/CD46 graft was suppressed. This was confirmed after GTKO/CD46 heart transplantation in baboons. PMID:25687023

  8. Initial in vivo experience of pig artery patch transplantation in baboons using mutant MHC (CIITA-DN) pigs.

    Iwase, H; Ekser, B; Satyananda, V; Zhou, H; Hara, H; Bajona, P; Wijkstrom, M; Bhama, J K; Long, C; Veroux, M; Wang, Y; Dai, Y; Phelps, C; Ayares, D; Ezzelarab, M B; Cooper, D K C


    In the pig-to-nonimmunosuppressed baboon artery patch model, a graft from an α1,3-galactosyltransferase gene-knockout pig transgenic for human CD46 (GTKO/CD46) induces a significant adaptive immune response (elicited anti-pig antibody response, increase in T cell proliferation on MLR, cellular infiltration of the graft), which is effectively prevented by anti-CD154mAb-based therapy. As anti-CD154mAb is currently not clinically applicable, we evaluated whether it could be replaced by CD28/B7 pathway blockade or by blockade of both pathways (using belatacept + anti-CD40mAb [2C10R4]). We further investigated whether a patch from a GTKO/CD46 pig with a mutant human MHC class II transactivator (CIITA-DN) gene would allow reduction in the immunosuppressive therapy administered. When grafts from GTKO/CD46 pigs were transplanted with blockade of both pathways, a minimal or insignificant adaptive response was documented. When a GTKO/CD46/CIITA-DN graft was transplanted, but no immunosuppressive therapy was administered, a marked adaptive response was documented. In the presence of CD28/B7 pathway blockade (abatacept or belatacept), there was a weak adaptive response that was diminished when compared with that to a GTKO/CD46 graft. Blockade of both pathways prevented an adaptive response. Although expression of the mutant MHC CIITA-DN gene was associated with a reduced adaptive immune response when immunosuppressive therapy was inadequate, when blockade of both the CD40/CD154 and CD28/B7 pathways was present, the response even to a GTKO/CD46 graft was suppressed. This was confirmed after GTKO/CD46 heart transplantation in baboons. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Genomic Alterations in CIITA Are Frequent in Primary Mediastinal Large B Cell Lymphoma and Are Associated with Diminished MHC Class II Expression

    Anja Mottok


    Full Text Available Primary mediastinal large B cell lymphoma (PMBCL is an aggressive non-Hodgkin’s lymphoma, predominantly affecting young patients. We analyzed 45 primary PMBCL tumor biopsies and 3 PMBCL-derived cell lines for the presence of genetic alterations involving the major histocompatibility complex (MHC class II transactivator CIITA and found frequent aberrations consisting of structural genomic rearrangements, missense, nonsense, and frame-shift mutations (53% of primary tumor biopsies and all cell lines. We also detected intron 1 mutations in 47% of the cases, and detailed sequence analysis strongly suggests AID-mediated aberrant somatic hypermutation as the mutational mechanism. Furthermore, we demonstrate that genomic lesions in CIITA result in decreased protein expression and reduction of MHC class II surface expression, creating an immune privilege phenotype in PMBCL. In summary, we establish CIITA alterations as a common mechanism of immune escape through reduction of MHC class II expression in PMBCL, with potential implications for future treatments targeting microenvironment-related biology.

  10. On the universality of PIV uncertainty quantification by image matching

    Sciacchitano, A.; Scarano, F.; Wieneke, B.


    The topic of uncertainty quantification in particle image velocimetry (PIV) is recognized as very relevant in the experimental fluid mechanics community, especially when dealing with turbulent flows, where PIV plays a prime role as diagnostic tool. The issue is particularly important when PIV is use

  11. Novel Atlantic bottlenose dolphin parainfluenza virus TtPIV-1 clusters with bovine PIV-3 genotype B strains.

    Eberle, Kirsten C; Neill, John D; Venn-Watson, Stephanie K; McGill, Jodi L; Sacco, Randy E


    Parainfluenza virus 3 (PIV-3) is a common viral infection not only in humans, but also in many other species. Serological evidence suggests that nearly 100 % of children in the United States have been infected with PIV-3 by 5 years of age. Similarly, in cattle, PIV-3 is commonly associated with bovine respiratory disease complex. A novel dolphin PIV-3 (TtPIV-1) was described by Nollens et al. in 2008 from a dolphin that was diagnosed with an unknown respiratory illness. At that time, TtPIV-1 was found to be most similar to, but distinct from, bovine PIV-3 (BPIV-3). In the present study, similar viral growth kinetics and pro-inflammatory cytokine (IL-1β, IL-6, and CXCL8) production were seen between BPIV-3 and TtPIV-1 in BEAS-2B, MDBK, and Vero cell lines. Initial nomenclature of TtPIV-1 was based on partial sequence of the fusion and RNA polymerase genes. Based on the similarities we saw with the in vitro work, it was important to examine the TtPIV-1 genome in more detail. Full genome sequencing and subsequent phylogenetic analysis revealed that all six viral genes of TtPIV-1 clustered within the recently described BPIV-3 genotype B strains, and it is proposed that TtPIV-1 be re-classified with BPIV-3 genotype B strains.

  12. Novel Atlantic bottlenose dolphin parainfluenza virus TtPIV-1 clusters with bovine PIV-3 genotype B strains

    Parainfluenza virus 3 (PIV-3) is a common viral infection not only in humans, but many other species. Serological evidence suggests that nearly 100% of children in the United States have been infected with PIV-3 by five years of age. Similarly, in cattle PIV-3 is commonly associated with bovine re...

  13. 3D Flow reconstruction using ultrasound PIV

    Poelma, C.; Mari, J.M.; Foin, N.; Tang, M.-X.; Krams, R.; Caro, C.G.; Weinberg, P.D.; Westerweel, J.


    Ultrasound particle image velocimetry (PIV) can be used to obtain velocity fields in non-transparent geometries and/or fluids. In the current study, we use this technique to document the flow in a curved tube, using ultrasound contrast bubbles as flow tracer particles. The performance of the techniq

  14. Development of PIV for Microgravity Diffusion Flames

    Greenberg, Paul S.; Wernet, Mark P.; Yanis, William; Urban, David L.; Sunderland, Peter B.


    Results are presented from the application of Particle Image Velocimetry(PIV) to the overfire region of a laminar gas jet diffusion flame in normal gravity. A methane flame burning in air at 0.98 bar was considered. The apparatus demonstrated here is packaged in a drop rig designed for use in the 2.2 second drop tower.

  15. Software for Acquiring Image Data for PIV

    Wernet, Mark P.; Cheung, H. M.; Kressler, Brian


    PIV Acquisition (PIVACQ) is a computer program for acquisition of data for particle-image velocimetry (PIV). In the PIV system for which PIVACQ was developed, small particles entrained in a flow are illuminated with a sheet of light from a pulsed laser. The illuminated region is monitored by a charge-coupled-device camera that operates in conjunction with a data-acquisition system that includes a frame grabber and a counter-timer board, both installed in a single computer. The camera operates in "frame-straddle" mode where a pair of images can be obtained closely spaced in time (on the order of microseconds). The frame grabber acquires image data from the camera and stores the data in the computer memory. The counter/timer board triggers the camera and synchronizes the pulsing of the laser with acquisition of data from the camera. PIVPROC coordinates all of these functions and provides a graphical user interface, through which the user can control the PIV data-acquisition system. PIVACQ enables the user to acquire a sequence of single-exposure images, display the images, process the images, and then save the images to the computer hard drive. PIVACQ works in conjunction with the PIVPROC program which processes the images of particles into the velocity field in the illuminated plane.

  16. Rational solutions to d-PIV

    Hietarinta, Jarmo; Hietarinta, Jarmo; Kajiwara, Kenji


    We study the rational solutions of the discrete version of Painleve's fourth equation d-PIV. The solutions are generated by applying Schlesinger transformations on the seed solutions -2z and -1/z. After studying the structure of these solutions we are able to write them in a determinantal form that includes an interesting parameter shift that vanishes in the continuous limit.

  17. Isotropic-planar illumination for PIV experiments

    Atkins, Michael D.; Kim, Tongbeum


    A new method for laser illumination in particle image velocimetry (PIV) has been introduced: internal "isotropic-planar" illumination that provides laser light to regions of the flow field that were previously cast into shadow using the conventional external (laser light sheet) illumination method. To demonstrate the effectiveness of the isotropic-planar illumination method, a comparison of the measured velocity field around five side-by-side circular cylinders that are immersed in uniform flow is made against the conventional external illumination method. The new method is effective at eliminating the shadow region, allowing the velocity field of the upstream, gap and downstream regions around the five side-by-side circular cylinders to be measured simultaneously. These PIV measurements provide new insight into the behavior of the gap flow that passes between the cylinders.

  18. Replacement of the Ectodomains of the Hemagglutinin-Neuraminidase and Fusion Glycoproteins of Recombinant Parainfluenza Virus Type 3 (PIV3) with Their Counterparts from PIV2 Yields Attenuated PIV2 Vaccine Candidates

    Tao, Tao; Skiadopoulos, Mario H.; Davoodi, Fatemeh; Riggs, Jeffrey M.; Collins, Peter L.; Murphy, Brian R


    We sought to develop a live attenuated parainfluenza virus type 2 (PIV2) vaccine strain for use in infants and young children, using reverse genetic techniques that previously were used to rapidly produce a live attenuated PIV1 vaccine candidate. The PIV1 vaccine candidate, designated rPIV3-1cp45, was generated by substituting the full-length HN and F proteins of PIV1 for those of PIV3 in the attenuated cp45 PIV3 vaccine candidate (T. Tao et al., J. Virol. 72:2955–2961, 1998; M. H. Skiadopoul...

  19. TecPIV-A MATLAB-based application for PIV-analysis of experimental tectonics

    Boutelier, D.


    TecPIV is a MATLAB-based, open source application aiming to facilitate and accelerate the Particle Image Velocimetry (PIV) analysis of analogue tectonic models. Since tectonic modelling experiments are usually slow, low sensitivity but high resolution digital cameras can be employed to monitor displacements and calculate strain from PIV analysis. The presented work-flow package provides an integrated environment to import raw files, calibrate, enhance, undistort and rectify the views of the model, calculate the incremental displacements between successive images, the spatial derivatives, and the Eulerian cumulative displacements. The calibration procedure employs a combination of linear and polynomial functions allowing correction of both lens and parallax distortions. The cross-correlation uses a parallelized FFT-method to accelerate the processing of large images. The performance is tested using synthetic images designed to evaluate the precision of the produced velocity field for various settings as well as the ability to capture sharp features characteristic of experimental tectonics.

  20. Application of Stereoscopic and Tomographic PIV in a Transonic Cascade

    Klinner, Joachim; Willert, Christian


    The contribution demonstrates the applicability of volumetric PIV in a highly loaded compressor cascade at Ma_1 = 0.60. Under these operation conditions the secondary flow structures in the cascade are dominated by a passage vortex located at the base of the blade and near the suction side. The application of volume resolving thick-sheet PIV (or tomo-PIV) near the trailing edge of the cascades blades is intended to demonstrate the techniques potential of instantaneously resolving secondary fl...

  1. [PIV: a computer-aided portal image verification system].

    Fu, Weihua; Zhang, Hongzhi; Wu, Jing


    Portal image verification (PIV) is one of the key actions in QA procedure for sophisticated accurate radiotherapy. The purpose of this study was to develop a PIV software as a tool for improving the accuracy and visualization of portal field verification and computing field placement errors. PIV was developed in the visual C++ integrated environment under Windows 95 operating system. It can improve visualization by providing tools for image processing and multimode images display. Semi-automatic register methods make verification more accurate than view-box method. It can provide useful quantitative errors for regular fields. PIV is flexible and accurate. It is an effective tool for portal field verification.

  2. Human PIV-2 recombinant Sendai virus (rSeV) elicits durable immunity and combines with two additional rSeVs to protect against hPIV-1, hPIV-2, hPIV-3, and RSV.

    Jones, Bart; Zhan, Xiaoyan; Mishin, Vasiliy; Slobod, Karen S; Surman, Sherri; Russell, Charles J; Portner, Allen; Hurwitz, Julia L


    The human parainfluenza viruses (hPIVs) and respiratory syncytial viruses (RSVs) are the leading causes of hospitalizations due to respiratory viral disease in infants and young children, but no vaccines are yet available. Here we describe the use of recombinant Sendai viruses (rSeVs) as candidate vaccine vectors for these respiratory viruses in a cotton rat model. Two new Sendai virus (SeV)-based hPIV-2 vaccine constructs were generated by inserting the fusion (F) gene or the hemagglutinin-neuraminidase (HN) gene from hPIV-2 into the rSeV genome. The inoculation of either vaccine into cotton rats elicited neutralizing antibodies toward both homologous and heterologous hPIV-2 virus isolates. The vaccines elicited robust and durable antibodies toward hPIV-2, and cotton rats immunized with individual or mixed vaccines were fully protected against hPIV-2 infections of the lower respiratory tract. The immune responses toward a single inoculation with rSeV vaccines were long-lasting and cotton rats were protected against viral challenge for as long as 11 months after vaccination. One inoculation with a mixture of the hPIV-2-HN-expressing construct and two additional rSeVs (expressing the F protein of RSV and the HN protein of hPIV-3) resulted in protection against challenge viruses hPIV-1, hPIV-2, hPIV-3, and RSV. Results identify SeV vectors as promising vaccine candidates for four different paramyxoviruses, each responsible for serious respiratory infections in children.

  3. Open source PIV software applied to streaming, time-resolved PIV data

    Taylor, Zachary; Gurka, Roi; Liberzon, Alex; Kopp, Gregory


    The data handling requirements for time resolved PIV data have increased substantially in recent years as the advent in high speed imaging and real time streaming. Therefore, there is a need for new hardware and software solutions for data storage and analysis. The presented solution is based on open source software (OSS) which has proven to be a successful means of development. This includes the PIV algorithms and flow analysis software. The solution, based on OSS known as ``URAPIV,'' originally was developed in Matlab and recently available in Python. The advantage of these scripting languages lies within their highly customizable platform; however, their routines cannot compete with commercially available software for computational speed. Thus, an effort has been undertaken to develop URAPIV-C++, a GUI based on the Qt 4 cross-platform open source library. This provides users with features commonly found in commercial packages and is comparable in processing speed to the commercial packages. The uniqueness of this package is in its complete handling of PIV experiments from the algorithms to post analysis under OSS license for large data sets. The package and its features are utilized in the recent STR-PIV system, which will be operable at the Advanced Facility for Avian Research at UWO. The wake flow behind an elongated body will be presented as a demonstration.

  4. PIV anisotropic denoising using uncertainty quantification

    Wieneke, B.


    Recently, progress has been made to reliably compute uncertainty estimates for each velocity vector in planar flow fields measured with 2D-or stereo-PIV. This information can be used for a post-processing denoising scheme to reduce errors by a spatial averaging scheme preserving true flow fluctuations. Starting with a 5 × 5 vector kernel, a second-order 2D-polynomial function is fitted to the flow field. Vectors just outside will be included in the filter kernel if they lie within the uncertainty band around the fitted function. Repeating this procedure, vectors are added in all directions until the true flow field can no longer be approximated by the second-order polynomial function. The center vector is then replaced by the value of the fitted function. The final shape and size of the filter kernel automatically adjusts to local flow gradients in an optimal way preserving true velocity fluctuations above the noise level. This anisotropic denoising scheme is validated first on synthetic vector fields varying spatial wavelengths of the flow field and noise levels relative to the fluctuation amplitude. For wavelengths larger than 5-7 times the spatial resolution, a noise reduction factor of 2-4 is achieved significantly increasing the velocity dynamic range. For large noise levels above 50% of the flow fluctuation, the denoising scheme can no longer distinguish between true flow fluctuations and noise. Finally, it is shown that the procedure performs well for typical experimental PIV vector fields. It provides an effective alternative to more complicated adaptive PIV algorithms optimizing interrogation window sizes and shapes based on seeding density, local flow gradients, and other criteria.

  5. 3D Reconstruction Technique for Tomographic PIV

    姜楠; 包全; 杨绍琼


    Tomographic particle image velocimetry(Tomo-PIV) is a state-of-the-art experimental technique based on a method of optical tomography to achieve the three-dimensional(3D) reconstruction for three-dimensional three-component(3D-3C) flow velocity measurements. 3D reconstruction for Tomo-PIV is carried out herein. Meanwhile, a 3D simplified tomographic reconstruction model reduced from a 3D volume light inten-sity field with 2D projection images into a 2D Tomo-slice plane with 1D projecting lines, i.e., simplifying this 3D reconstruction into a problem of 2D Tomo-slice plane reconstruction, is applied thereafter. Two kinds of the most well-known algebraic reconstruction techniques, algebraic reconstruction technique(ART) and multiple algebraic reconstruction technique(MART), are compared as well. The principles of the two reconstruction algorithms are discussed in detail, which has been performed by a series of simulation images, yielding the corresponding recon-struction images that show different features between the ART and MART algorithm, and then their advantages and disadvantages are discussed. Further discussions are made for the standard particle image reconstruction when the background noise of the pre-initial particle image has been removed. Results show that the particle image recon-struction has been greatly improved. The MART algorithm is much better than the ART. Furthermore, the computa-tional analyses of two parameters(the particle density and the number of cameras), are performed to study their effects on the reconstruction. Lastly, the 3D volume particle field is reconstructed by using the improved algorithm based on the simplified 3D tomographic reconstruction model, which proves that the algorithm simplification is feasible and it can be applied to the reconstruction of 3D volume particle field in a Tomo-PIV system.

  6. Main results of the 4th International PIV Challenge

    Kähler, Christian J.; Astarita, Tommaso; Vlachos, Pavlos P.; Sakakibara, Jun; Hain, Rainer; Discetti, Stefano; La Foy, Roderick; Cierpka, Christian


    In the last decade, worldwide PIV development efforts have resulted in significant improvements in terms of accuracy, resolution, dynamic range and extension to higher dimensions. To assess the achievements and to guide future development efforts, an International PIV Challenge was performed in Lisbon (Portugal) on July 5, 2014. Twenty leading participants, including the major system providers, i.e., Dantec (Denmark), LaVision (Germany), MicroVec (China), PIVTEC (Germany), TSI (USA), have analyzed 5 cases. The cases and analysis explore challenges specific to 2D microscopic PIV (case A), 2D time-resolved PIV (case B), 3D tomographic PIV (cases C and D) and stereoscopic PIV (case E). During the event, 2D macroscopic PIV images (case F) were provided to all 80 attendees of the workshop in Lisbon, with the aim to assess the impact of the user's experience on the evaluation result. This paper describes the cases and specific algorithms and evaluation parameters applied by the participants and reviews the main results. For future analysis and comparison, the full image database will be accessible at URL"/> .

  7. Main results of the third international PIV Challenge

    Stanislas, M.; Okamoto, K.; Kähler, C.J.; Westerweel, J.; Scarano, F.


    This paper presents the main results of the third international PIV Challenge which took place in Pasadena (USA) on the 19th and 20th of September 2005. This workshop was linked to the PIV05 International Symposium held at the same place the same week. The present contribution states the objectives

  8. Collaborative framework for PIV uncertainty quantification: the experimental database

    Neal, Douglas R.; Sciacchitano, Andrea; Smith, Barton L.; Scarano, Fulvio


    The uncertainty quantification of particle image velocimetry (PIV) measurements has recently become a topic of great interest as shown by the recent appearance of several different methods within the past few years. These approaches have different working principles, merits and limitations, which have been speculated upon in subsequent studies. This paper reports a unique experiment that has been performed specifically to test the efficacy of PIV uncertainty methods. The case of a rectangular jet, as previously studied by Timmins et al (2012) and Wilson and Smith (2013b), is used. The novel aspect of the experiment is simultaneous velocity measurements using two different time-resolved PIV systems and a hot-wire anemometry (HWA) system. The first PIV system, called the PIV measurement system (‘PIV-MS’), is intended for nominal measurements of which the uncertainty is to be evaluated. It is based on a single camera and features a dynamic velocity range (DVR) representative of typical PIV experiments. The second PIV system, called the ‘PIV-HDR’ (high dynamic range) system, features a significantly higher DVR obtained with a higher digital imaging resolution. The hot-wire is placed in close proximity to the PIV measurement domain. The three measurement systems were carefully set to simultaneously measure the flow velocity at the same time and location. The comparison between the PIV-HDR system and the HWA provides an estimate of the measurement precision of the reference velocity for evaluation of the instantaneous error in the measurement system. The discrepancy between the PIV-MS and the reference data provides the measurement error, which is later used to assess the different uncertainty quantification methods proposed in the literature. A detailed comparison of the uncertainty estimation methods based on the present datasets is presented in a second paper from Sciacchitano et al (2015). Furthermore, this database offers the potential to be used for

  9. Smartphone based Tomographic PIV using colored shadows

    Aguirre-Pablo, Andres A.; Alarfaj, Meshal K.; Li, Er Qiang; Thoroddsen, Sigurdur T.


    We use low-cost smartphones and Tomo-PIV, to reconstruct the 3D-3C velocity field of a vortex ring. The experiment is carried out in an octagonal tank of water with a vortex ring generator consisting of a flexible membrane enclosed by a cylindrical chamber. This chamber is pre-seeded with black polyethylene microparticles. The membrane is driven by an adjustable impulsive air-pressure to produce the vortex ring. Four synchronized smartphone cameras, of 40 Mpx each, are used to capture the location of particles from different viewing angles. We use red, green and blue LED's as backlighting sources, to capture particle locations at different times. The exposure time on the smartphone cameras are set to 2 seconds, while exposing each LED color for about 80 μs with different time steps that can go below 300 μs. The timing of these light pulses is controlled with a digital delay generator. The backlight is blocked by the instantaneous location of the particles in motion, leaving a shadow of the corresponding color for each time step. The image then is preprocessed to separate the 3 different color fields, before using the MART reconstruction and cross-correlation of the time steps to obtain the 3D-3C velocity field. This proof of concept experiment represents a possible low-cost Tomo-PIV setup.

  10. Adaptive interrogation for 3D-PIV

    Novara, Matteo; Ianiro, Andrea; Scarano, Fulvio


    A method to adapt the shape and orientation of interrogation volumes for 3D-PIV motion analysis is introduced, aimed to increase the local spatial resolution. The main application of this approach is the detailed analysis of complex 3D and vortex-dominated flows that exhibit high vorticity in confined regions like shear layers and vortex filaments. The adaptive criterion is based on the analysis of the components of the local velocity gradient tensor, which returns the level of anisotropy of velocity spatial fluctuations. The principle to increase the local spatial resolution is based on the deformation of spherical isotropic interrogation regions, obtained by means of Gaussian weighting, into ellipsoids, with free choice of the principal axes and their directions. The interrogation region is contracted in the direction of the maximum velocity variation and elongated in the minimum one in order to maintain a constant interrogation volume. The adaptivity technique for three-dimensional PIV data takes advantage of the 3D topology of the flow, allowing increasing the spatial resolution not only in the case of shear layers, but also for vortex filaments, which is not possible for two-dimensional measurement in the plane normal to the vortex axis. The definition of the ellipsoidal interrogation region semi-axes is based on the singular values and singular directions of the local velocity gradient tensor as obtained by the singular values decomposition technique (SVD). The working principle is verified making use of numerical simulations of a shear layer and of a vortex filament. The application of the technique to data from a Tomo-PIV experiment conducted on a round jet, shows that the resolution of the shear layer at the jet exit can be considerably improved and an increase of about 25% in the vorticity peak is attained when the adaptive approach is applied. On the other hand, the peak vorticity description in the core of vortex rings is only slightly improved with

  11. Uncertainty Quantification and Statistical Convergence Guidelines for PIV Data

    Stegmeir, Matthew; Kassen, Dan


    As Particle Image Velocimetry has continued to mature, it has developed into a robust and flexible technique for velocimetry used by expert and non-expert users. While historical estimates of PIV accuracy have typically relied heavily on "rules of thumb" and analysis of idealized synthetic images, recently increased emphasis has been placed on better quantifying real-world PIV measurement uncertainty. Multiple techniques have been developed to provide per-vector instantaneous uncertainty estimates for PIV measurements. Often real-world experimental conditions introduce complications in collecting "optimal" data, and the effect of these conditions is important to consider when planning an experimental campaign. The current work utilizes the results of PIV Uncertainty Quantification techniques to develop a framework for PIV users to utilize estimated PIV confidence intervals to compute reliable data convergence criteria for optimal sampling of flow statistics. Results are compared using experimental and synthetic data, and recommended guidelines and procedures leveraging estimated PIV confidence intervals for efficient sampling for converged statistics are provided.

  12. CITA/NLRC5: A critical transcriptional regulator of MHC class I gene expression.

    Downs, Isaac; Vijayan, Saptha; Sidiq, Tabasum; Kobayashi, Koichi S


    Major histocompatibility complex (MHC) class I and class II molecules play essential roles in the development and activation of the human adaptive immune system. An NLR protein, CIITA (MHC class II transactivator) has been recognized as a master regulator of MHC class II gene expression, albeit knowledge about the regulatory mechanism of MHC class I gene expression had been limited. Recently identified MHC class I transactivator (CITA), or NLRC5, also belongs to the NLR protein family and constitutes a critical regulator for the transcriptional activation of MHC class I genes. In addition to MHC class I genes, CITA/NLRC5 induces the expression of β2 -microglobulin, TAP1 and LMP2, essential components of the MHC class I antigen presentation pathway. Therefore, CITA/NLRC5 and CIITA are transcriptional regulators that orchestrate the concerted expression of critical components in the MHC class I and class II pathways, respectively. © 2016 BioFactors, 42(4):349-357, 2016.

  13. An Experimental Demonstration of Accelerated Tomo-PIV

    Worth, N. A.; Nickels, T. B.

    Tomographic Particle Image Velocimetry (Tomo-PIV) is a promising new PIV technique. However, its high computational costs often make time-resolved measurements impractical. In this paper, a new preprocesseing technique is tested experimentally for the first time on a simple vortex ring. The new method produces very similar velocity and vorticity distributions to the standard iterated solution, at a fraction of the computational cost. Therefore, through this new technique, the processing of thousands of vector fields required for turbulent statistics can be made significantly more affordable; an important step in the development of Tomo-PIV.

  14. PIV-validated numerical modeling of pulsatile flows in distal coronary end-to-side anastomoses.

    Xiong, F L; Chong, C K


    This study employed particle image velocimetry (PIV) to validate a numerical model in a complementary approach to quantify hemodynamic factors in distal coronary anastomoses and to gain more insights on their relationship with anastomotic geometry. Instantaneous flow fields and wall shear stresses (WSS) were obtained from PIV measurement in a modified life-size silastic anastomosis model adapted from a conventional geometry by incorporating a smooth graft-artery transition. The results were compared with those predicted by a concurrent numerical model. The numerical method was then used to calculate cycle-averaged WSS (WSS(cyc)) and spatial wall shear stress gradient (SWSSG), two critical hemodynamic factors in the pathogenesis of intimal thickening (IT), to compare the conventional and modified geometries. Excellent qualitative agreement and satisfactory quantitative agreement with averaged normalized error in WSS between 0.8% and 8.9% were achieved between the PIV experiment and numerical model. Compared to the conventional geometry, the modified geometry produces a more uniform WSS(cyc) distribution eliminating both high and low WSS(cyc) around the toe, critical in avoiding IT. Peak SWSSG on the artery floor of the modified model is less than one-half that in the conventional case, and high SWSSG at the toe is eliminated. The validated numerical model is useful for modeling unsteady coronary anastomotic flows and elucidating the significance of geometry regulated hemodynamics. The results suggest the clinical relevance of constructing smooth graft-artery transition in distal coronary anastomoses to improve their hemodynamic performance.

  15. POD Mode Robustness for the Turbulent Jet Sampled with PIV

    Hodzic, Azur; Meyer, Knud Erik; Velte, Clara Marika


    , direct numerical simulations and in certain cases large eddy simulations tend to agree fairly well with experiments, their practical implementation introduces the problem of data storage. The experimentalist, however, experiences the same problem, using highspeed particle image velocimetry (PIV) systems...

  16. PIV Analysis of Ludwig Prandtl's Historic Flow Visualization Films

    Willert, Christian


    Around 1930 Ludwig Prandtl and his colleagues O. Tietjens and W. M\\"uller published two films with visualizations of flows around surface piercing obstacles to illustrate the unsteady process of flow separation. These visualizations were achieved by recording the motion of fine particles sprinkled onto the water surface in water channels. The resulting images meet the relevant criteria of properly seeded recordings for particle image velocimetry (PIV). Processing these image sequences with modern PIV algorithms allows the visualization of flow quantities (e.g. vorticity) that were unavailable prior to the development of the PIV technique. The accompanying fluid dynamics video consists of selected original film sequences overlaid with visualizations obtained through PIV processing.

  17. PIV Measurements on a Blowing Flap

    Hutcheson, Florence V.; Stead, Daniel J.


    PIV measurements of the flow in the region of a flap side edge are presented for several blowing flap configurations. The test model is a NACA 63(sub 2)-215 Hicks Mod-B main-element airfoil with a half-span Fowler flap. Air is blown from small slots located along the flap side edge on either the top, bottom or side surfaces. The test set up is described and flow measurements for a baseline and three blowing flap configurations are presented. The effects that the flap tip jets have on the structure of the flap side edge flow are discussed for each of the flap configurations tested. The results indicate that blowing air from a slot located along the top surface of the flap greatly weakened the top vortex system and pushed it further off the top surface. Blowing from the bottom flap surface kept the strong side vortex further outboard while blowing from the side surface only strengthened the vortex system or accelerated the merging of the side vortex to the flap top surface. It is concluded that blowing from the top or bottom surfaces of the flap may lead to a reduction of flap side edge noise.

  18. Conserved amino acid motifs from the novel Piv/MooV family of transposases and site-specific recombinases are required for catalysis of DNA inversion by Piv.

    Tobiason, D M; Buchner, J M; Thiel, W H; Gernert, K M; Karls, A C


    Piv, a site-specific invertase from Moraxella lacunata, exhibits amino acid homology with the transposases of the IS110/IS492 family of insertion elements. The functions of conserved amino acid motifs that define this novel family of both transposases and site-specific recombinases (Piv/MooV family) were examined by mutagenesis of fully conserved amino acids within each motif in Piv. All Piv mutants altered in conserved residues were defective for in vivo inversion of the M. lacunata invertible DNA segment, but competent for in vivo binding to Piv DNA recognition sequences. Although the primary amino acid sequences of the Piv/MooV recombinases do not contain a conserved DDE motif, which defines the retroviral integrase/transposase (IN/Tnps) family, the predicted secondary structural elements of Piv align well with those of the IN/Tnps for which crystal structures have been determined. Molecular modelling of Piv based on these alignments predicts that E59, conserved as either E or D in the Piv/MooV family, forms a catalytic pocket with the conserved D9 and D101 residues. Analysis of Piv E59G confirms a role for E59 in catalysis of inversion. These results suggest that Piv and the related IS110/IS492 transposases mediate DNA recombination by a common mechanism involving a catalytic DED or DDD motif.

  19. Assembling filamentous phage occlude pIV channels.

    Marciano, D K; Russel, M; Simon, S M


    Filamentous phage f1 is exported from its Escherichia coli host without killing the bacterial cell. Phage-encoded protein pIV, which is required for phage assembly and secretion, forms large highly conductive channels in the outer membrane of E. coli. It has been proposed that the phage are extruded across the bacterial outer membrane through pIV channels. To test this prediction, we developed an in vivo assay by using a mutant pIV that functions in phage export but whose channel opens in the absence of phage extrusion. In E. coli lacking its native maltooligosacharride transporter LamB, this pIV variant allowed oligosaccharide transport across the outer membrane. This entry of oligosaccharide was decreased by phage production and still further decreased by production of phage that cannot be released from the cell surface. Thus, exiting phage block the pIV-dependent entry of oligosaccharide, suggesting that phage occupy the lumen of pIV channels. This study provides the first evidence, to our knowledge, for viral exit through a large aqueous channel.

  20. Veiligheidsrapport voor de PIV-goot in het Laboratorium voor Vloeistofmechanica

    Hofland, B.


    Bevat een veiligheidsvoorschrift voor de PIV (particle-image velocimetry) goot. Het rapport is vooral gericht op het gebruik van de krachtige Nd: YAG laser (veiligheidsklasse 4) die gebruikt wordt voor de PIV techniek.

  1. PIV-based pressure fluctuations in the turbulent boundary layer

    Ghaemi, Sina; Ragni, Daniele; Scarano, Fulvio


    The unsteady pressure field is obtained from time-resolved tomographic particle image velocimetry (Tomo-PIV) measurement within a fully developed turbulent boundary layer at free stream velocity of U ∞ = 9.3 m/s and Reθ = 2,400. The pressure field is evaluated from the velocity fields measured by Tomo-PIV at 10 kHz invoking the momentum equation for unsteady incompressible flows. The spatial integration of the pressure gradient is conducted by solving the Poisson pressure equation with fixed boundary conditions at the outer edge of the boundary layer. The PIV-based evaluation of the pressure field is validated against simultaneous surface pressure measurement using calibrated condenser microphones mounted behind a pinhole orifice. The comparison shows agreement between the two pressure signals obtained from the Tomo-PIV and the microphones with a cross-correlation coefficient of 0.6 while their power spectral densities (PSD) overlap up to 3 kHz. The impact of several parameters governing the pressure evaluation from the PIV data is evaluated. The use of the Tomo-PIV system with the application of three-dimensional momentum equation shows higher accuracy compared to the planar version of the technique. The results show that the evaluation of the wall pressure can be conducted using a domain as small as half the boundary layer thickness (0.5δ99) in both the streamwise and the wall normal directions. The combination of a correlation sliding-average technique, the Lagrangian approach to the evaluation of the material derivative and the planar integration of the Poisson pressure equation results in the best agreement with the pressure measurement of the surface microphones.

  2. Enhancing Tomo-PIV reconstruction quality by reducing ghost particles

    de Silva, C. M.; Baidya, R.; Marusic, I.


    A technique to enhance the reconstruction quality and consequently the accuracy of the velocity vector field obtained in Tomo-PIV experiments is presented here. The methodology involves detecting and eliminating spurious outliers in the reconstructed intensity field (ghost particles). A simulacrum matching-based reconstruction enhancement (SMRE) technique is proposed, which utilizes the characteristic shape and size of actual particles to remove ghost particles in the reconstructed intensity field. An assessment of SMRE is performed by a quantitative comparison of Tomo-PIV simulation results and DNS data, together with a comparison to Tomo-PIV experimental data measured in a turbulent channel flow at a matched Reynolds number (Reτ = 937) to the DNS study. For the simulation data, a comparative study is performed on the reconstruction quality based on an ideal reconstruction determined from known particle positions. The results suggest that a significant improvement in the reconstruction quality and flow statistics is achievable at typical seeding densities used in Tomo-PIV experiments. This improvement is further amplified at higher seeding densities, enabling the use of up to twice the typical seeding densities currently used in Tomo-PIV experiments. A reduction of spurious vectors present in the velocity field is also observed based on a median outlier detection criterion. The application of SMRE to Tomo-PIV experimental data shows an improvement in flow statistics, comparable to the improvement seen in simulations. Finally, due to the non-iterative nature of SMRE, the increase in processing time is marginal since only a single pass of the reconstruction algorithm is required.


    Shah, Louise Jivan; Morrison, G.L.; Behnia, Masud


    Characteristics of vertical mantle heat exchanger tanks for SDHW systems have been investigated experimentally and theoretically using particle image velocimetry (PIV) and CFD modelling. A glass model of a mantle heat exchanger tank was constructed so that the flow distribution in the mantle could...... be studied using the PIV test facility. Two transient three-dimensional CFD-models of the glass model mantle tank were developed using the CFD-programmes CFX and FLUENT.The experimental results illustrate that the mantle flow structure in the mantle is complicated and the distribution of flow in the mantle...

  4. PIV measurements of flow structures in a spray dryer

    Meyer, Knud Erik; Velte, Clara Marika; Ullum, Thorvald


    Stereoscopic Particle Image Velocimetry (PIV) measurements are made in horizontal planes in a simplified scale model of a spray dryer using water as fluid. The sample rate was sufficient to resolve phenomena at lower frequencies. Data reveal asymmetric velocity fields in both mean fields and dyna......Stereoscopic Particle Image Velocimetry (PIV) measurements are made in horizontal planes in a simplified scale model of a spray dryer using water as fluid. The sample rate was sufficient to resolve phenomena at lower frequencies. Data reveal asymmetric velocity fields in both mean fields...

  5. POD as tool for comparison of PIV and LES data

    Meyer, Knud Erik; Cavar, Dalibor; Pedersen, Jakob Martin


    Both Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES) provides instantaneous velocity fields which can contain dynamical flow structures that occur systematically. Turbulent flows also contain random flow structures, and therefore there is a need for tools that can identify...... the systematic dynamic flow structures. We show how Proper Orthogonal Decomposition (POD) based on snapshots (instantaneous flow realizations) can be used for this purpose. As a test case, we use PIV measurements and LES calculations on the same turbulent jet in cross flow. The Reynolds number based...

  6. PIV in a model wind turbine rotor wake

    Meyer, Knud Erik; Naumov, Igor; Karbadin, Ivan


    Stereoscopic particle image velocimetry (PIV) measurements of the flow in the wake of scale model of a horizontal axis wind turbine is presented Near the rotor, measurements are made in vertical planes intersecting the rotor axis These planes capture flow effect from the tip and root vortices...

  7. PIV Measurements in Weakly Buoyant Gas Jet Flames

    Sunderland, Peter B.; Greenbberg, Paul S.; Urban, David L.; Wernet, Mark P.; Yanis, William


    Despite numerous experimental investigations, the characterization of microgravity laminar jet diffusion flames remains incomplete. Measurements to date have included shapes, temperatures, soot properties, radiative emissions and compositions, but full-field quantitative measurements of velocity are lacking. Since the differences between normal-gravity and microgravity diffusion flames are fundamentally influenced by changes in velocities, it is imperative that the associated velocity fields be measured in microgravity flames. Velocity measurements in nonbuoyant flames will be helpful both in validating numerical models and in interpreting past microgravity combustion experiments. Pointwise velocity techniques are inadequate for full-field velocity measurements in microgravity facilities. In contrast, Particle Image Velocimetry (PIV) can capture the entire flow field in less than 1% of the time required with Laser Doppler Velocimetry (LDV). Although PIV is a mature diagnostic for normal-gravity flames , restrictions on size, power and data storage complicate these measurements in microgravity. Results from the application of PIV to gas jet flames in normal gravity are presented here. Ethane flames burning at 13, 25 and 50 kPa are considered. These results are presented in more detail in Wernet et al. (2000). The PIV system developed for these measurements recently has been adapted for on-rig use in the NASA Glenn 2.2-second drop tower.

  8. Extraction of airfoil data using PIV and pressure measurements

    Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær


    Velocimetry (PIV) flow fields at different rotor azimuth positions are examined for determining sectional airfoil data. The AOA is derived locally by determining the local circulation on the blade from pressure data and subtracting the induction of the bound circulation from the local velocity. The derived...

  9. Endoscopic PIV measurements in a low pressure turbine rig

    Kegalj, Martin; Schiffer, Heinz-Peter [Technische Universitaet Darmstadt (Germany). Department of Gas Turbines and Aerospace Propulsion


    Particle-Image-Velocimetry (PIV) is a useful way to acquire information about the flow in turbomachinery. Several premises have to be fulfilled to achieve high-quality data, for example, optical access, low vibrations and low reflections. However, not all test facilities comply with these requirements. If there is no optical access to the test area, measurements cannot be performed. The use of borescopic optics is a possible solution to this issue, as the access required is very small. Several different techniques can be used to measure the three components of the velocity vector, one of which is Stereo-PIV. These techniques require either large optical access from several viewing angles or highly complex setups. Orthogonal light sheet orientations in combination with borescopic optics using Planar-PIV can deliver sufficient information about the flow. This study will show the feasibility of such an approach in an enclosed test area, such as the interblade space in a Low-Pressure-Turbine-Rig. The results from PIV will be compared with data collected with conventional techniques, such as the Five-Hole-Probe and the 2-component Hot-Wire-Anemometry. An analysis of time- and phase-averaged data will be performed. (orig.)

  10. PIV-based load determination in aircraft propellers

    Ragni, D.


    The thesis describes the application of particle image velocimetry (PIV) to study the aerodynamic loads of airfoils and aircraft propellers. The experimental work focuses on the development of a measurement procedure to infer the pressure of the flow field from the velocity distribution obtained by

  11. PIV-based load determination in aircraft propellers

    Ragni, D.


    The thesis describes the application of particle image velocimetry (PIV) to study the aerodynamic loads of airfoils and aircraft propellers. The experimental work focuses on the development of a measurement procedure to infer the pressure of the flow field from the velocity distribution obtained by

  12. PIV measurement at the blowdown pipe outlet. [Particle Image Velocimetry

    Puustinen, M.; Laine, J.; Raesaenen, A.; Pyy, L.; Telkkae, J. [Lappeenranta Univ. of Technology, Lappeenranta (Finland)


    This report summarizes the findings of the PIV measurement tests carried out in January - February 2013 with the scaled down PPOOLEX test facility at LUT. The main objective of the tests was to find out the operational limits of the PIV system regarding suitable test conditions and correct values of different adjustable PIV parameters. An additional objective was to gather CFD grade data for verification/validation of numerical models. Both water and steam injection tests were carried out. PIV measurements with cold water injection succeeded well. Raw images were of high quality, averaging over the whole measurement period could be done and flow fields close to the blowdown pipe outlet could be determined. In the warm water injection cases the obtained averaged velocity field images were harder to interpret, especially if the blowdown pipe was also filled with warm water in the beginning of the measurement period. The absolute values of the velocity vectors seemed to be smaller than in the cold water injection cases. With very small steam flow rates the steam/water interface was inside the blowdown pipe and quite stable in nature. The raw images were of good quality but due to some fluctuation in the velocity field averaging of the velocity images over the whole measured period couldn't be done. Condensation of steam in the vicinity of the pipe exit probably caused these fluctuations. A constant outflow was usually followed by a constant inflow towards the pipe exit. Vector field images corresponding to a certain phase of the test could be extracted and averaged but this would require a very careful analysis so that the images could be correctly categorized. With higher steam flow rates rapid condensation of large steam bubbles created small gas bubbles which were in front of the measurement area of the PIV system. They disturbed the measurements by reflecting laser light like seeding particles and therefore the raw images were of poor quality and they couldn

  13. Limitations of estimating turbulent convection velocities from PIV

    de Kat, Roeland; Dawson, James R; Ganapathisubramani, Bharathram


    This paper deals with determination of turbulent convection velocities from particle image velocimetry (PIV). Turbulent convection velocities are of interest because they can be used to map temporal information into space. Convection velocity can be defined in several different ways. One approach is to use the phase-spectrum of two signals with a time-separation. Obtaining convection velocity per wavenumber involves determining a spatial spectrum. PIV data is limited in spatial resolution and sample length. The influence of truncation of both spatial resolution and frequency resolution is investigated, as well as the influences of spatial filtering and measurement noise. These issues are investigated by using a synthetic data set obtained by creating velocity-time data with an imposed spectrum. Results from the validation show that, when applying a Hamming window before determining the phase spectrum, there is a usable range of wavenumbers for which convection velocities can be determined. Simulation of flow ...

  14. Development of refractively matched hydrogels for PIV applications

    Byron, Margaret; Variano, Evan


    We present a technique for fabricating models whose refractive indices are close to that of water, using two hydrogel polymers. The models' transparency and matched refractive index makes them useful for experiments in Refractive-Index-Matched Particle Image Velocimetry (RIM-PIV). The materials used - polyacrylamide and agarose hydrogel - are inexpensive and can be cast into a variety of desired shapes using injection molding. The models' utility is demonstrated with sets of vector fields, calculated with standard PIV algorithms; vectors can be obtained from the surrounding flowfield and from interior points within the model. Using these data, we calculate solid-body rotation and translation in combination with fluid-phase velocities, and investigate coupling between the two.

  15. A study of EWOD-driven droplets by PIV investigation.

    Lu, Hsiang-Wei; Bottausci, Frederic; Fowler, Jesse D; Bertozzi, Andrea L; Meinhart, Carl; Kim, Chang-Jin C J


    Despite the recent interest in droplet-based microfluidics using electrowetting-on-dielectric (EWOD), fundamental understanding of the fluid dynamics remains limited to two-dimensional (2D) reduction of the Navier-Stokes equation. Experimental data are in dire need to verify the predictions and advance the field. We report an investigation of the flow inside droplets actuated by EWOD in air using micro particle image velocimetry (micro-PIV). Using the continuity equation, we reconstruct the 3D velocity field from the 2D PIV experimental data. We present some fundamental findings and build valuable insights that will help design sophisticated EWOD microfluidic devices. For example, the results confirm that efficient mixing in a droplet may be achieved by moving the droplet along an irreversible pattern that breaks the symmetry of the two circulating inner flows.

  16. Development and application of animation technique by using PIV database

    Lee, Y.H. [Korea Maritime University, Pusan (Korea); Choi, J.W. [IIT, Pusan (Korea); Seo, M.S.; Ahn, K.H.; Kim, M.Y. [Graduate School, Korea Maritime University, Pusan (Korea)


    Animation technique from the PIV database is particularly emphasized to give macroscopic and quantitative description of complex flow fields. As an example, a Karman vortex street(Re=2x10{sup 4}) from the two-dimensional cylinder immersed in a circular water tank is visualized and processed by PIV. Cross correlation algorithm to estimate the peak coefficients is adopted for the identification and its performance is compared to that of the FFT routine. All animation jobs are implemented completely on single personal computer. Compressed digital images are obtained by Motion-JPEG board and various AVI files are finally obtained through graphic processes. As results, continuous pictures of the spatial distribution of the instant vectors, turbulent intensity, turbulent kinetic energy, kinetic energy, vorticity and three Reynolds stress components are animated dynamically on PC monitor. And streak lines, trajectories and streamlines are also displayed in real-time sense. (author). 10 refs., 18 figs.

  17. Dynamic analysis of granite rockburst based on the PIV technique

    Wang Hongjian; Liu Da’an; Gong Weili; Li Liyun


    This paper describes the deep rockburst simulation system to reproduce the granite instantaneous rock-burst process. Based on the PIV (Particle Image Velocimetry) technique, quantitative analysis of a rock-burst, the images of tracer particle, displacement and strain fields can be obtained, and the debris trajectory described. According to the observation of on-site tests, the dynamic rockburst is actually a gas–solid high speed flow process, which is caused by the interaction of rock fragments and surrounding air. With the help of analysis on high speed video and PIV images, the granite rockburst failure process is composed of six stages of platey fragment spalling and debris ejection. Meanwhile, the elastic energy for these six stages has been calculated to study the energy variation. The results indicate that the rockburst process can be summarized as:an initiating stage, intensive developing stage and gradual decay stage. This research will be helpful for our further understanding of the rockburst mechanism.

  18. PIV measurements of hydrodynamic interactions between biofilms and flow

    Christensen, Kenneth T.; Kazemifar, Farzan; Aybar, Marcelo; Perez-Calleja, Patricia; Nerenberg, Robert; Sinha, Sumit; Hardy, Richard J.; Best, Jim L.; Sambrook Smith, Greg H.


    Biofilms constitute an important form of bacterial life in aquatic environments and are present at the interface of fluids and solid such as riverbeds or bridge columns. They are also utilized in bioreactors for bioremediation and water treatment purposes. They are permeable, heterogeneous, and deformable structures that can influence the flow and mass/momentum transport, yet their interaction with flow is not fully understood in part due to technical obstacles impeding quantitative experimental investigations. We have attempted to address these challenges using the PIV technique and fluorescence imaging to investigate the flow field around cylinders covered with biofilms at different growth stages. These measurements are meant to uncover the coupled dynamics of turbulence and the biofilm development. Preliminary results of PIV measurements of flow-biofilm interactions in channel flow will be presented.

  19. Lucas-Kanade fluid trajectories for time-resolved PIV

    Yegavian, Robin; Leclaire, Benjamin; Champagnat, Frédéric; Illoul, Cédric; Losfeld, Gilles


    We introduce a new method for estimating fluid trajectories in time-resolved PIV. It relies on a Lucas-Kanade paradigm and consists in a simple and direct extension of a two-frame estimation with FOLKI-PIV (Champagnat et al 2011 Exp. Fluids 50 1169-82). The so-called Lucas-Kanade Fluid Trajectories (LKFT) are assumed to be polynomial in time, and are found as the minimizer of a global functional, in which displacements are sought so as to match the intensities of a series of images pairs in the sequence, in the least-squares sense. All pairs involve the central image, similar to other recent time-resolved approaches (FTC (Lynch and Scarano 2013 Meas. Sci. Technol. 24 035305) and FTEE (Jeon et al 2014 Exp. Fluids 55 1-16)). As switching from a two-frame to a time-resolved objective simply amounts to adding terms in a functional, no significant additional algorithmic element is required. Similar to FOLKI-PIV the method is very well suited for GPU acceleration, which is an important feature as computational complexity increases with the image sequence size. Tests on synthetic data exhibiting peak-locking show that increasing the image sequence size strongly reduces both associated bias and random error, and that LKFT has a remaining total error comparable to that of FTEE on this case. Results on case B of the third PIV challenge (Stanislas et al 2008 Exp. Fluids 45 27-71) also show its ability to drastically reduce the error in situations with low signal-to-noise ratio. These results are finally confirmed on experimental images acquired in the near-field of a low Reynolds number jet. Strong reductions in peak-locking, spatial and temporal noise compared to two-frame estimation are also observed, on the displacement components themselves, as well as on spatial or temporal derivatives, such as vorticity and material acceleration.

  20. Comparison of Stereo-PIV and Plenoptic-PIV Measurements on the Wake of a Cylinder in NASA Ground Test Facilities.

    Fahringer, Timothy W.; Thurow, Brian S.; Humphreys, William M., Jr.; Bartram, Scott M.


    A series of comparison experiments have been performed using a single-camera plenoptic PIV measurement system to ascertain the systems performance capabilities in terms of suitability for use in NASA ground test facilities. A proof-of-concept demonstration was performed in the Langley Advanced Measurements and Data Systems Branch 13-inch (33- cm) Subsonic Tunnel to examine the wake of a series of cylinders at a Reynolds number of 2500. Accompanying the plenoptic-PIV measurements were an ensemble of complementary stereo-PIV measurements. The stereo-PIV measurements were used as a truth measurement to assess the ability of the plenoptic-PIV system to capture relevant 3D/3C flow field features in the cylinder wake. Six individual tests were conducted as part of the test campaign using three different cylinder diameters mounted in two orientations in the tunnel test section. This work presents a comparison of measurements with the cylinders mounted horizontally (generating a 2D flow field in the x-y plane). Results show that in general the plenoptic-PIV measurements match those produced by the stereo-PIV system. However, discrepancies were observed in extracted pro les of the fuctuating velocity components. It is speculated that spatial smoothing of the vector fields in the stereo-PIV system could account for the observed differences. Nevertheless, the plenoptic-PIV system performed extremely well at capturing the flow field features of interest and can be considered a viable alternative to traditional PIV systems in smaller NASA ground test facilities with limited optical access.

  1. Characteristics of seeding particles for PIV/PTV analysis

    Hadad, Tal; Liberzon, Alexander; Bernhaim, Anne; Gurka, Roi


    PIV and PTV are non-intrusive state-of-the-art techniques widely used for flow measurements. Seeding particles are required to be used as tracers to the flow. The accuracy of the velocity measurements is limited by the ability of the tracer particles to adequately follow the instantaneous motion of the continuous phase. In order to follow the flow effectively, the particles should satisfy numerous requirements: size, sphericity, density, high refractive index, concentration and chemical inert. Since seeding particles for liquids are commonly polymer-based particles we probe the influence of their surface coating on the results obtained from optical measurements. Using a canonical lid-driven cavity flow we measured the velocity field using PIV and PTV and compared the results (velocity and acceleration) obtained with the same particles with and without chemical treatment of surfactants. Probability density functions of the results using particles before and after treatment are compared statistically utilizing the two-sample Kolmogorov-Smirnov tests. Although the mean values exhibit similar trends, fluctuations and velocity derivatives show some discrepancy in respect to the chemical treatment. The obtained results show a variance of up to 5% between the values obtained for using washed and un-washed particles, for both PIV and PTV experiments with some influence related to the size of the particles.

  2. PIV validation of blood-heart valve leaflet interaction modelling.

    Kaminsky, R; Dumont, K; Weber, H; Schroll, M; Verdonck, P


    The aim of this study was to validate the 2D computational fluid dynamics (CFD) results of a moving heart valve based on a fluid-structure interaction (FSI) algorithm with experimental measurements. Firstly, a pulsatile laminar flow through a monoleaflet valve model with a stiff leaflet was visualized by means of Particle Image Velocimetry (PIV). The inflow data sets were applied to a CFD simulation including blood-leaflet interaction. The measurement section with a fixed leaflet was enclosed into a standard mock loop in series with a Harvard Apparatus Pulsatile Blood Pump, a compliance chamber and a reservoir. Standard 2D PIV measurements were made at a frequency of 60 bpm. Average velocity magnitude results of 36 phase-locked measurements were evaluated at every 10 degrees of the pump cycle. For the CFD flow simulation, a commercially available package from Fluent Inc. was used in combination with inhouse developed FSI code based on the Arbitrary Lagrangian-Eulerian (ALE) method. Then the CFD code was applied to the leaflet to quantify the shear stress on it. Generally, the CFD results are in agreement with the PIV evaluated data in major flow regions, thereby validating the FSI simulation of a monoleaflet valve with a flexible leaflet. The applicability of the new CFD code for quantifying the shear stress on a flexible leaflet is thus demonstrated.

  3. Robust 4 Camera 3D Synthetic Aperture PIV

    Bajpayee, Abhishek; Techet, Alexandra


    We present novel processing techniques which allow for robust 4 camera 3D synthetic aperture (SA) PIV. These pre and post processing techniques, applied to raw images and reconstructed volumes, significantly improve SA reconstruction SNR values and consequently allow for accurate SAPIV velocity fields. SA, or light field, PIV has typically required 8 or 9 cameras in order to achieve high reconstruction quality and velocity field reconstruction quality values, Q and Qv respectively. This is primarily because the effective signal to noise ratio (SNR) of refocused images, when using traditional multiplicative or additive refocusing techniques, increases with the number of cameras being used. However, tomographic reconstruction (used with TomoPIV), is able to achieve relatively high SNR reconstructions using 4 or 5 cameras owing to its iterative but significantly more computationally expensive algorithm. Our processing techniques facilitate better recovery of relevant information in SA reconstructions using only 4 views. As a result, we no longer have to trade setup cost and complexity (number of cameras) for computational speed of the reconstruction algorithm.

  4. On the Feasibility of Multi-kHz Acquisition Rate Tomographic-PIV in Turbulent Flames


    AFRL-AFOSR-UK-TR-2013-0044 On the Feasibility of multi-kHz Acquisition Rate Tomographic- PIV in Turbulent Flames Isaac Boxx...Tomographic- PIV in Turbulent Flames 5a. CONTRACT NUMBER FA8655-12-1-2092 5b. GRANT NUMBER Grant 12-2092 5c. PROGRAM ELEMENT NUMBER 61102F 6...distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Tomographic particle image velocimetry (tomographic- PIV ) is a recently

  5. Pediatric blood sample collection from a pre-existing peripheral intravenous (PIV) catheter.

    Braniff, Heather; DeCarlo, Ann; Haskamp, Amy Corey; Broome, Marion E


    Aiming to minimize pain in a hospitalized child, the purpose of this observational study was to describe characteristics of blood samples collected from pre-existing peripheral intravenous (PIV) catheters in pediatric patients. One hundred and fifty blood samples were reviewed for number of unusable samples requiring a specimen to be re-drawn. Success of the blood draw and prevalence of the loss of the PIV following blood collection was also measured. Findings included one clotted specimen, success rate of 91.3%, and 1.3% of PIVs becoming non-functional after collection. Obtaining blood specimens from a pre-existing PIV should be considered in a pediatric patient.

  6. Application of Stereo PIV on a Supersonic Parachute Model

    Wernet, Mark P.; Locke, Randy J.; Wroblewski, Adam; Sengupta, Anita


    The Mars Science Laboratory (MSL) is the next step in NASA's Mars Exploration Program, currently scheduled for 2011. The spacecraft's descent into the Martian atmosphere will be slowed from Mach 2 to subsonic speeds via a large parachute system with final landing under propulsive control. A Disk-Band-Gap (DBG) parachute will be used on MSL similar to the designs that have been used on previous missions, however; the DBG parachute used by MSL will be larger (21.5 m) than in any of the previous missions due to the weight of the payload and landing site requirements. The MSL parachute will also deploy at higher Mach number (M 2) than previous parachutes, which can lead to instabilities in canopy performance. Both the increased size of the DBG above previous demonstrated configurations and deployment at higher Mach numbers add uncertainty to the deployment, structural integrity and performance of the parachute. In order to verify the performance of the DBG on MSL, experimental testing, including acquisition of Stereo Particle Imaging Velocimetry (PIV) measurements were required for validating CFD predictions of the parachute performance. A rigid model of the DBG parachute was tested in the 10x10 foot wind tunnel at GRC. Prior to the MSL tests, a PIV system had never been used in the 10x10 wind tunnel. In this paper we discuss some of the technical challenges overcome in implementing a Stereo PIV system with a 750x400 mm field-of-view in the 10x10 wind tunnel facility and results from the MSL hardshell canopy tests.

  7. Flow Mapping of a Jet in Crossflow with Stereoscopic PIV

    Meyer, Knud Erik; Özcan, Oktay; Westergaard, C. H.


    Stereoscopic Particle Image Velocimetry (PIV) has been used to make a three-dimensional flow mapping of a jet in crossflow. The Reynolds number based on the free stream velocity and the jet diameter was nominally 2400. A jet-to-crossflow velocity ratio of 3.3 was used. Details of the formation...... of the counter rotating vortex pair found behind the jet are shown. The vortex pair results in two regions with strong reversed velocities behind the jet trajectory. Regions of high turbulent kinetic energy are identified. The signature of the unsteady shear layer vortices is found in the mean vorticity field....

  8. PIV Measurements and Mechanisms of Adjacent Synthetic Jets Interactions

    LUO Zhen-Bing; XIA Zhi-Xun


    Interactions of adjacent synthetic jet actuators with varying relative amplitude and the relative phase of driving voltage are measured using a particle image velocimetry(PIV).Varying relative amplitude or relative phase of driving voltage of the adjacent actuators vectors the direction of the ensuing merged jet of the adjacent synthetic jets.The vectoring mechanism of the adjacent vortex pairs,attract-impact causing deflection(AICD),is provided to explain why the merged jet is generally vectored to the side of the phase-leading synthetic jet or the synthetic jet with higher driving voltage.

  9. Coeficiente de descarga em emissores de pivô central

    SILVA,RENATO M. DA; Rubens D. Coelho; Lucas do A. Faria; Maschio,Rafael


    Este trabalho foi desenvolvido com o objetivo de determinar, em condições laboratoriais, o coeficiente de descarga (Cd) dos emissores fixos tipo “spray” (Senninger, Nelson e Fabrimar) utilizados em equipamentos pivô central no Brasil. Foram avaliados 45 bocais Senninger, 42 bocais Nelson e 36 bocais Fabrimar, com três repetições, totalizando 369 bocais ensaiados. As pressões de funcionamento variaram entre 6 e 30 PSI (41,37 a 206,84 kPa), com intervalo de leitura a cada 2 PSI (13,...

  10. Technological advances in the study of HLA-DRA promoter regulation: Extending the functions of CIITA, Oct-1, Rb, and RFX

    Melissa I.Niesen; Aaron R.Osborne; William R.Lagor; Harry Zhang; Kristy Kazemfar; Gene C.Ness; George Blanck


    Several advances were established in examining the interaction of transcriptional factors with the HLA-DRA promoter. First, hydrodynamic injection was used to demonstrate the activation of the promoter by class II transactivator in a live mouse. Second, the Oct-1 DNA-binding site in the HLA-DRA promoter is a negative element in many cells, but here we show that Oct-1 activates the promoter independently of the Oct-1-binding site. Third, the retinoblastoma (Rb) protein is required for the induction of the endogenous HLA-DRA gene, due to a poorly understood, pleiotropic effect on the Oct-1 and YY1 repressive functions at the HLA-DRA promoter. There has never been an indication that direct promoter activation, by Rb, is possible. Here, we report that the first HLA-DRA intron has an Rb-responsive element, as indicated by a transient transfection/promoter reporter assay. Finally, RFX activates a methylated version of an HLA-DRA promoter reporter construct, consistent with the role of RFX in rescuing the expression of the methylated, endogenous HLA-DRA gene. Here, we report that this RFX function is not limited to a specific RFX-binding sequence or to the HLA-DRA promoter. These advances provide bases for novel investigations into the function of the major histocompatibility class II promoter.

  11. Measurement of rotation and strain-rate tensors by using stereoscopic PIV

    Özcan, O.; Meyer, Knud Erik; Larsen, Poul Scheel


    A simple technique is described for measuring the mean rate-of-displacement (velocity gradient) tensor in a plane by using a conventional stereoscopic PIV system. The technique involves taking PIV data in two or three closely-spaced parallel planes at different times. All components of the mean...

  12. Overlap of PIV syndrome, VACTERL and Pallister-Hall syndrome: clinical and molecular analysis.

    Killoran, C E; Abbott, M; McKusick, V A; Biesecker, L G


    The polydactyly, imperforate anus, vertebral anomalies syndrome (PIV, OMIM 174100) was determined as a distinct syndrome by Say and Gerald in 1968 (Say B, Gerald PS. Lancet 1968: 2: 688). We noted that the features of PIV overlap with the VATER association and Pallister-Hall syndrome (PHS, OMIM 146510), which includes polydactyly, (central or postaxial), shortened fingers, hypoplastic nails, renal anomalies, imperforate anus, and hypothalamic hamartoma. Truncation mutations in GL13, a zinc finger transcription factor gene, have been shown to cause PHS. We performed a molecular evaluation on a patient diagnosed with PIV, whose mother, grandfather, and maternal aunt had similar malformations. We sequenced the GLI3 gene in the patient to determine if she had a mutation. The patient was found to have a deletion in nucleotides 2188-2207 causing a frameshift mutation that predicts a truncated protein product of the gene. Later clinical studies demonstrated that the patient also has a hypothalamic hamartoma, a finding in PHS. We concluded that this family had atypical PHS and not PIV. This result has prompted us to re-evaluate the PIV literature to see if PIV is a valid entity. Based on these data and our examination of the literature, we conclude that PIV is not a valid diagnostic entity. We conclude that patients diagnosed with PIV should be reclassified as having VACTERL, or PHS, or another syndrome with overlapping malformations.

  13. Time-Resolved PIV for Space-Time Correlations in Hot Jets

    Wernet, Mark P.


    Temporally Resolved Particle Image Velocimetry (TR-PIV) is being used to characterize the decay of turbulence in jet flows a critical element for understanding the acoustic properties of the flow. A TR-PIV system, developed in-house at the NASA Glenn Research Center, is capable of acquiring planar PIV image frame pairs at up to 10 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number.

  14. High-resolution PIV analysis of compressibility effects in turbulent jets

    Ceglia, G.; Violato, D.; Tuinstra, M.; Scarano, F.

    An investigation on the compressibility effects arising into the near field of turbulent jets operated at high Reynolds number at Mach numbers M=0.3, 0.9 and 1.1 (under-expanded regime) is carried out with two-components planar PIV experiments with high resolution cameras. The arrangement of the PIV

  15. Efficacy of parainfluenza virus 5 (PIV5)-based tuberculosis vaccines in mice.

    Chen, Zhenhai; Gupta, Tuhina; Xu, Pei; Phan, Shannon; Pickar, Adrian; Yau, Wilson; Karls, Russell K; Quinn, Frederick D; Sakamoto, Kaori; He, Biao


    Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), is an important human pathogen. Bacillus Calmette-Guérin (BCG), a live, attenuated variant of Mycobacterium bovis, is currently the only available TB vaccine despite its low efficacy against the infectious pulmonary form of the disease in adults. Thus, a more-effective TB vaccine is needed. Parainfluenza virus 5 (PIV5), a paramyxovirus, has several characteristics that make it an attractive vaccine vector. It is safe, inexpensive to produce, and has been previously shown to be efficacious as the backbone of vaccines for influenza, rabies, and respiratory syncytial virus. In this work, recombinant PIV5 expressing M. tuberculosis antigens 85A (PIV5-85A) and 85B (PIV5-85B) have been generated and their immunogenicity and protective efficacy evaluated in a mouse aerosol infection model. In a long-term protection study, a single dose of PIV5-85A was found to be most effective in reducing M. tuberculosis colony forming units (CFU) in lungs when compared to unvaccinated, whereas the BCG vaccinated animals had similar numbers of CFUs to unvaccinated animals. BCG-prime followed by a PIV5-85A or PIV5-85B boost produced better outcomes highlighted by close to three-log units lower lung CFUs compared to PBS. The results indicate that PIV5-based M. tuberculosis vaccines are promising candidates for further development.

  16. Determination of instantaneous pressure in a transonic base flow using four-pulse tomographic PIV

    Blinde, P.L.; Lynch, K.P.; Schrijer, F.F.J.; Van Oudheusden, B.W.


    A tomographic four-pulse PIV system is used in a transonic axisymmetric base flow experiment at a nominal free stream Mach number of 0.7, with the objective to obtain flow acceleration and pressure data. The PIV system, consisting of two double-pulse lasers and twelve cameras, allows acquiring two v

  17. Application of Tomo-PIV in a large-scale supersonic jet flow facility

    Wernet, Mark P.


    Particle imaging velocimetry (PIV) has been used extensively at NASA GRC over the last 15 years to build a benchmark data set of hot and cold jet flow measurements in an effort to understand acoustic noise sources in high-speed jets. Identifying the noise sources in high-speed jets is critical for ultimately modifying the nozzle hardware design/operation and therefore reducing the jet noise. Tomographic PIV (Tomo-PIV) is an innovative approach for acquiring and extracting velocity information across extended volumes of a flow field, enabling the computation of additional fluid mechanical properties not typically available using traditional PIV techniques. The objective of this work was to develop and implement the Tomo-PIV measurement capability and apply it in a large-scale outdoor test facility, where seeding multiple flow streams and operating in the presence of daylight presents formidable challenges. The newly developed Tomo-PIV measurement capability was applied in both a subsonic M 0.9 flow and an under-expanded M 1.4 heated jet flow field. Measurements were also obtained using traditional two-component (2C) PIV and stereo PIV in the M 0.9 flow field for comparison and validation of the Tomo-PIV results. In the case of the M 1.4 flow, only the 2C PIV was applied to allow a comparison with the Tomo-PIV measurement. The Tomo-PIV fields-of-view covered 180 × 180 × 10 mm, and the reconstruction domains were 3500 × 3500 × 200 voxels. These Tomo-PIV measurements yielded all three components of vorticity across entire planes for the first time in heated supersonic jet flows and provided the first full 3D reconstruction of the Mach disk and oblique shock intersections inside of the barrel shocks. Measuring all three components of vorticity across multiple planes in the flow, potentially reduces the number of measurement configurations (streamwise and cross-stream PIV) required to fully characterize the mixing-enhanced nozzle flows routinely studied in

  18. The NASA Subsonic Jet Particle Image Velocimetry (PIV) Dataset

    Bridges, James; Wernet, Mark P.


    Many tasks in fluids engineering require prediction of turbulence of jet flows. The present document documents the single-point statistics of velocity, mean and variance, of cold and hot jet flows. The jet velocities ranged from 0.5 to 1.4 times the ambient speed of sound, and temperatures ranged from unheated to static temperature ratio 2.7. Further, the report assesses the accuracies of the data, e.g., establish uncertainties for the data. This paper covers the following five tasks: (1) Document acquisition and processing procedures used to create the particle image velocimetry (PIV) datasets. (2) Compare PIV data with hotwire and laser Doppler velocimetry (LDV) data published in the open literature. (3) Compare different datasets acquired at the same flow conditions in multiple tests to establish uncertainties. (4) Create a consensus dataset for a range of hot jet flows, including uncertainty bands. (5) Analyze this consensus dataset for self-consistency and compare jet characteristics to those of the open literature. The final objective was fulfilled by using the potential core length and the spread rate of the half-velocity radius to collapse of the mean and turbulent velocity fields over the first 20 jet diameters.

  19. High resolution PIV of flow over biofilm covered walls

    Hartenberger, Joel; Perlin, Marc; Ceccio, Steven


    Microbial, 'slime' biofilms detrimentally affect the performance of engineered systems used every day from heat exchangers to large ocean-going vessels. The presence of a slime layer on a pipe wall or external boundary often leads to a significant increase in drag and may alter the nature of the turbulence in the adjacent flow. Despite these consequences, relatively few efforts have been undertaken to understand the underlying physical processes which couple biofilm characteristics with increased drag and other alterations to the flow. Experiments performed in a 1:14 scale replica of the US Navy's Large Cavitation Channel (LCC) at the University of Michigan investigate the effect of biofilm composition, coverage and thickness on the development of an external turbulent boundary layer (TBL) through the use of conventional and micro PIV. A range of fields of view (FOVs) were used to capture both the inner and outer regions of the boundary layer. The fine resolution of micro PIV gives an in-depth look at the near-wall region of the flow and may provide evidence linking specific biofilm features with flow characteristics while the less resolved, larger FOVs capture flow behavior to the freestream. Measurement techniques used to characterize the biofilm will be presented along with a description of the mean flow and turbulent fluctuations in the TBL.

  20. PIV measurement of internal structure of diesel fuel spray

    Cao, Z.M. [Ecotechnology System Lab., Yokohama National Univ. (Japan); Nishino, K. [Div. of Artificial Environment and Systems, Yokohama National Univ. (Japan); Mizuno, S. [Yokohama National Univ. (Japan); Torii, K. [Dept. of Mechanical Engineering and Materials Science, Yokohama National Univ. (Japan)


    This paper reports particle image velocimetry (PIV) measurements of diesel fuel spray injected from a single-hole nozzle at injection pressures ranging from 30 to 70 MPa, which are comparable to partial-load operating conditions of commercial diesel engines. The fuel is injected into a non-combusting environment pressurized up to 2.0 MPa. A laser-induced fluorescent (LIF) technique is utilized to visualize internal structures of fuel sprays formed by densely-distributing droplets. A specially designed synchronization system is developed to acquire double-frame spray images at an arbitrary time delay after injection. A direct cross-correlation PIV technique is applied to measure instantaneous droplet velocity distribution. Unique large-scale structures in droplet concentration, called 'branch-like structures' by Azetsu et al. (1990), are observed and shown to be associated with active vortical motions, which appear to be responsible for the mixing between droplets and the surrounding gas. It is found that the droplets tend to move out of the vortical structures and accumulate in the regions of low vorticity. Some other interesting features concerning droplet velocity fields are also presented. (orig.)

  1. Experimental analysis of particle sizes for PIV measurements

    van Overbrüggen, Timo; Klaas, Michael; Soria, Julio; Schröder, Wolfgang


    The right choice of seeding particles strongly influences the outcome of a particle-image velocimetry (PIV) measurement. Particles have to scatter enough light to be seen by cameras and follow the flow faithfully. As the flow following behavior depends on the inertia and therefore the size of the particle, smaller particles are desirable. Unfortunately, larger particles possess better light scattering behavior, which is especially important for volumetric PIV measurements. In this paper, the particle response of two exemplary solid particles to an oscillatory air flow created by a piston movement is analyzed and compared to analytic results by Hjelmfelt and Mockros (1966 Appl. Sci. Res. 16 149-61) concerning phase lag and amplitude ratio between particle movement and flow field. To achieve realistic experimental boundary conditions, polydispersed particles are used for the analysis. The analytic results show a strong dependence on the diameter. That is, using the volumetric mean diameter an overestimation of the phase lag of the particles is determined, whereas an underestimation of phase lag is computed for the number mean diameter. Hence, for polydispersed particles a more general analysis than that based on the particle mean diameter is required to determine in detail the particle following behavior.

  2. 75 FR 28771 - Federal Acquisition Regulation; FAR Case 2009-027, Personal Identity Verification of Contractor...


    ...: 9000-AL60 Federal Acquisition Regulation; FAR Case 2009-027, Personal Identity Verification of..., company name (if any), and ``FAR Case 2009-027'' on your attached document. Fax: 202-501-4067. Mail... over contractor CACs. A CAC is the DoD term for a Personal Identity Verification (PIV) card. A PIV...

  3. Rheometry-PIV of shear-thickening wormlike micelles.

    Marín-Santibañez, Benjamín M; Pérez-Gonzalez, José; de Vargas, Lourdes; Rodríguez-Gonzalez, Francisco; Huelsz, Guadalupe


    The shear-thickening behavior of an equimolar semidilute aqueous solution of 40 mM/L cetylpyridinium chloride and sodium salicylate was studied in this work by using a combined method of rheometry and particle image velocimetry (PIV). Experiments were conducted at 27.5 degrees C with Couette, vane-bob, and capillary rheometers in order to explore a wide shear stress range as well as the effect of boundary conditions and time of flow on the creation and destruction of shear-induced structures (SIS). The use of the combined method of capillary rheometry with PIV allowed the detection of fast spatial and temporal variations in the flow kinematics, which are related to the shear-thickening behavior and the dynamics of the SIS but are not distinguished by pure rheometrical measurements. A rich-in-details flow curve was found for this solution, which includes five different regimes. Namely, at very low shear rates a Newtonian behavior was found, followed by a shear thinning one in the second regime. In the third, shear banding was observed, which served as a precursor of the SIS and shear-thickening. The fourth and fifth regimes in the flow curve were separated by a spurtlike behavior, and they clearly evidenced the existence of shear-thickening accompanied by stick-slip oscillations at the wall of the rheometer, which subsequently produced variations in the shear rate under shear stress controlled flow. Such a stick-slip phenomenon prevailed up to the highest shear stresses used in this work and was reflected in asymmetric velocity profiles with spatial and temporal variations linked to the dynamics of creation and breakage of the SIS. The presence of apparent slip at the wall of the rheometer provides an energy release mechanism which leads to breakage of the SIS, followed by their further reformation during the stick part of the cycles. In addition, PIV measurements allowed the detection of apparent slip at the wall, as well as mechanical failures in the bulk of the


    Zhengliang Liu; Jinyu Jiao; Ying Zheng


    The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle image velocimetry (2D-PIV) and three-dimensional particle image velocimetry (3D-PIV) experiments in this study. Due to the limitation of 2D-PIV configuration, the contamination generated by the strong tangential velocity in the cyclone can be registered in the axial velocity detected by 2D-PIV. Efficient methods are proposed in this work to remove this contamination. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity are also computed by the Reynolds stress model (RSM) and verified using the PIV experimental results. Reasonable agreements are obtained.

  5. Stereoscopic PIV measurement of boundary layer affected by DBD actuator

    Procházka Pavel


    Full Text Available The effect of ionic wind generated by plasma actuator on developed boundary layer inside a narrow channel was investigated recently. Since the main investigated plane was parallel to the channel axis, the description of flow field was not evaluated credibly. This paper is dealing with cross-section planes downstream the actuator measured via 3D time-resolved PIV. The actuator position is in spanwise or in streamwise orientation so that ionic wind is blown in the same direction as the main flow or in opposite direction or perpendicularly. The interaction between boundary layer and ionic wind is evaluated for three different velocities of main flow and several parameters of plasma actuation (steady and unsteady regime, frequency etc.. Statistical properties of the flow are shown as well as dynamical behaviour of arising longitudinal vortices are discussed via phase-locked measurement and decomposition method.


    RUAN Xiaodong; WU Feng; F.YAMAMOTO


    Particle Image Velocimetry (PIV) techniques were developed to measure the convective N2-air flow under gradient magnetic fields. The velocity fields were calculated by the Minimum Quadratic Difference (MQD) algorithm and spurious vectors were eliminated by Delaunay Tessellation.The N2-air flow was measured as the magnetic flux density varying from 0 ~ 1.5 T. A strengthened vortex flow of air was observed under the condition that the magnetic field was applied, and the velocity of N2 jet rose with the increase of the magnetic density. The experimental results show that the magnetic force will induce a vortex flow and cause a convection flow of the air mixture when both gradients of the O2 concentration and the magnetic field intensity exist.

  7. Parainfluenza virus type 5 (PIV-5) morphology revealed by cryo-electron microscopy.

    Terrier, Olivier; Rolland, Jean-Paul; Rosa-Calatrava, Manuel; Lina, Bruno; Thomas, Daniel; Moules, Vincent


    The knowledge of parainfluenza type 5 (PIV-5) virion morphology is essentially based on the observation of negatively stained preparations in conventional transmission electron microscopy (CTEM). In this study, the ultrastructure of frozen-hydrated intact PIV-5 was examined by cryo-electron microscopy (cryo-EM). Cryo-EM revealed a majority of spherical virions (70%), with a lower pleiomorphy than originally observed in CTEM. Phospholipid bilayer thickness, spike length and glycoprotein spikes density were measured. About 2000 glycoprotein spikes were present in an average-sized spherical virion. Altogether, these data depict a more precise view of PIV-5 morphology.

  8. A study of plunging breaker mechanics by PIV measurements and a Navier-Stokes solver

    Emarat, Narumon; Forehand, David I. M.; Christensen, Erik Damgaard


    The mechanics of a surf-zone plunging breaker are studied from Particle Image Velocimetry (PIV) measurements and a numerical model based on the Navier-Stokes equations, using a Volume of Fluid (VOF) method. An additional numerical model using a Boundary-Integral Method (BIM) is also used in order...... to generate input conditions for the main numerical model. The PIV measurements were performed at the University of Edinburgh and then compared against the results found by the numerical model developed at DHI Water and Environment. Good agreement is found, throughout the breaking process, between...... the velocity fields of the plunging breaker measured using PIV and those predicted by the numerical model....

  9. Material acceleration estimation by four-pulse tomo-PIV

    Lynch, K. P.; Scarano, F.


    A tomographic PIV system is introduced for the instantaneous measurement of the material acceleration (material derivative of velocity). The system is conceived to operate with short temporal separation (microseconds) and is therefore suitable for applications up to the high-speed flow regimes. The method of operation consists of tomographic imaging of a measurement volume using three arrays of four CCD cameras and two double-pulse laser systems. Advantages and shortcomings of the approach with respect to the most commonly used method based on light polarization are discussed. Various approaches are compared to determine the optimal utilization of four-pulse data to measure the material acceleration: Eulerian and Lagrangian schemes are compared to the recently introduced fluid trajectory correlation (FTC) technique from the authors. A synthetic image test case of a translating vortex is used to compare the schemes with and without the presence of noise. The truncation errors and sensitivity to random noise for each scheme are highlighted. A discussion is also given on the dynamic range of the schemes. The four-pulse tomographic system is used to measure the separated wake of an axisymmetric truncated base with afterbody at a Reynolds number of 68 000. The system calibration accuracy and the baseline measurement uncertainty of the velocity are evaluated with a zero-time delay test. A novel criterion is introduced to establish the relative accuracy of the material derivative measurement, based on the curl of the material acceleration field. The results indicate that the four-pulse tomo-PIV approach suits the measurement of the material acceleration using a variety of estimation schemes. In particular, the FTC technique gives the lowest error levels and is well-suited to perform accurate material acceleration measurements.

  10. Functionalised alginate flow seeding microparticles for use in Particle Image Velocimetry (PIV).

    Varela, Sylvana; Balagué, Isaac; Sancho, Irene; Ertürk, Nihal; Ferrando, Montserrat; Vernet, Anton


    Alginate microparticles as flow seeding fulfil all the requirements that are recommended for the velocity measurements in Particle Image Velocimetry (PIV). These spherical microparticles offer the advantage of being environmentally friendly, having excellent seeding properties and they can be produced via a very simple process. In the present study, the performances of alginate microparticles functionalised with a fluorescent dye, Rhodamine B (RhB), for PIV have been studied. The efficacy of fluorescence is appreciated in a number of PIV applications since it can boost the signal-to-noise ratio. Alginate microparticles functionalised with RhB have high emission efficiency, desirable match with fluid density and controlled size. The study of the particles behaviour in strong acid and basic solutions and ammonia is also included. This type of particles can be used for measurements with PIV and Planar Laser Induced Fluorescence (PLIF) simultaneously, including acid-base reactions.


    Shi Hui-xian; Wang Qin-hui; Wang Can-xing; Luo Zhong-yang; Cen Ke-fa


    Particle Imaging Velocimetry (PIV) is a valuable measuring tool for studying multiphase flows, such as liquid-gas and gas-solid flow. It can be used to carry out many hydrodynamic studies, in particular, to determine accurately the gas-solid flow structure in CFB (Circulating Fluidized Beds). In this paper, the technique characteristics was described in applying the PIV to measure the gas-solid flow in circulating fluidized beds. A primary experiment was completed on a CFB unit with the PIV, yielding the velocity vector fields of high-density particles for different gas-solid superficial velocities and solid recycle rates. Velocities of the transported particles were calculated with cross-correlation method. The major factors influencing the successful measurement of particle velocity with the PIV technique were also described.

  12. Estimation of turbulence dissipation rate by Large eddy PIV method in an agitated vessel

    Kysela Bohuš


    Full Text Available The distribution of turbulent kinetic energy dissipation rate is important for design of mixing apparatuses in chemical industry. Generally used experimental methods of velocity measurements for measurement in complex geometries of an agitated vessel disallow measurement in resolution of small scales close to turbulence dissipation ones. Therefore, Particle image velocity (PIV measurement method improved by large eddy Ply approach was used. Large eddy PIV method is based on modeling of smallest eddies by a sub grid scale (SGS model. This method is similar to numerical calculations using Large Eddy Simulation (LES and the same SGS models are used. In this work the basic Smagorinsky model was employed and compared with power law approximation. Time resolved PIV data were processed by Large Eddy PIV approach and the obtained results of turbulent kinetic dissipation rate were compared in selected points for several operating conditions (impeller speed, operating liquid viscosity.

  13. Animation construction and application example by the post-processing of PIV data

    Kim, M.Y.; Lee, H. [Korea Maritime University Graduate School, Seoul (Korea); Choi, J.W. [Irae Infomation Technology, Seoul (Korea); Lee, Y.H. [Korea Maritime University, Seoul (Korea)


    Animation technique from the PIV database is particularly emphasized to give macroscopic and quantitative description of complex flow fields. This paper shows animation construction and application example for the post-processing of PIV data. As examples, first case is a pitching airfoil immersed in free surface water circulating tunnel. Second case is a wake of a model-ship. Third case of PIV data is a large scale surface flow field. Obtained images are processed in time sequence by PIV exclusive routines where an efficient and reliable cross correlation algorithm is included for vector identification. All animation jobs are implemented completely on single personal computer environment. Compressed digital images are obtained initially by Motion-JPEG board and various AVI files are finally obtained through graphic processes. (author). 4 refs., 22 figs.

  14. Combined PIV and DGV applied to a pressurized gas turbine combustion facility

    Willert, C.; Hassa, C.; Stockhausen, G.; Jarius, M.; Voges, M.; Klinner, J.


    This paper provides an overview of flow field measurements on a pressurized generic combustor that shares typical features of realistic gas turbine combustors. Both Doppler global velocimetry (DGV) and particle image velocimetry (PIV) were applied in parallel to achieve volumetric, three-component velocity data sets of the reacting flow field at pressures of 2 and 10 bar with 700 K pre-heating. Limited optical access to the mixing zone required a combination of PIV and DGV to obtain averaged three-component velocity data from a single viewing direction. The acquired volume data sets of the time-averaged flow in the mixing zone contain about 40 parallel planes spaced at 2 mm with a spatial resolution of 1.2 × 1.2 mm2 each. Difficulties encountered in the application of stereoscopic PIV to a simple atmospheric generic combustor illustrate the advantage of the combined PIV-DGV technique.

  15. Flow mapping by PIV in microstructures with three-dimensional flow behavior

    Westergaard, C.; Klank, Henning; Kutter, Jörg Peter


    fortement tridimensionnels. Ceci offre un challenge à la technique de la PIV appliquée à la micro-fluidique (souvent appelée Micro PIV). Le papier donne un exemple de mesures réalisées dans un micro-système pour illustrer les possibilités et discuter l'application du principe de stéréoscopie, permettant...

  16. Time Resolved PIV for Space-Time Correlations in Hot Jets

    Wernet, Mark P.


    Temporally Resolved Particle Image Velocimetry (TR-PIV) is the newest and most exciting tool recently developed to support our continuing efforts to characterize and improve our understanding of the decay of turbulence in jet flows -- a critical element for understanding the acoustic properties of the flow. A new TR-PIV system has been developed at the NASA Glenn Research Center which is capable of acquiring planar PIV image frame pairs at up to 25 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number

  17. PIV as a method for quantifying root cell growth and particle displacement in confocal images.

    Bengough, A Glyn; Hans, Joachim; Bransby, M Fraser; Valentine, Tracy A


    Particle image velocimetry (PIV) quantifies displacement of patches of pixels between successive images. We evaluated PIV as a tool for microscopists by measuring displacements of cells and of a surrounding granular medium in confocal laser scanning microscopy images of Arabidopsis thaliana roots labeled with cell-membrane targeted green fluorescent protein. Excellent accuracy (e.g., displacement standard deviation PIV-predicted and actual displacements (r(2) > 0.83). Root mean squared error for these distorted images was 0.4-1.1 pixels, increasing at higher magnification factors. Cell growth and rhizosphere deformation were tracked with good temporal (e.g., 1-min interval) and spatial resolution, with PIV patches located on recognizable cell features being tracked more successfully. Appropriate choice of GFP-label was important to decrease small-scale biological noise due to intracellular motion. PIV of roots grown in stiff 2% versus 0.7% agar showed patterns of cell expansion consistent with physically impeded roots of other species. Roots in glass ballotini underwent rapid changes in growth direction on a timescale of minutes, associated with localized arching of ballotini. By tracking cell vertices, we monitored automatically cell length, width, and area every minute for 0.5 h for cells in different stages of development. In conclusion, PIV measured displacements successfully in images of living root cells and the external granular medium, revealing much potential for use by microscopists.

  18. Investigation of a corrugated channel flow with an open source PIV software

    Sivas Deniz


    Full Text Available In this study, the corrugated channel flow was investigated by using an open-source particle image velocimetry (PIV software. The open-source software called OpenPIV was first verified by using images of an earlier experimental work of a vortex ring formation. The corrugated channel flow images were taken with 200 W power LED light source and a high speed camera and those images were analysed with these spatial and temporal tools of OpenPIV. Laminar, transient and turbulent flow regimes were identified when Reynolds number was below 1100, in between 1100 and 2000 and higher than 2000, respectively. The velocity vectors were found to be about 20% lower than the previous study results. The flow inside the grooves was also investigated with OpenPIV and flow characteristics at the grooves were captured when interrogation window size was lowered. The visualization of the flow was presented for different Reynolds numbers with the relative scale values. As a result of this study, OpenPIV software was determined as promising open source PIV analysis software.

  19. Comparison of Tomo-PIV and 3D-PTV for microfluidic flows

    Kim, Hyoungsoo; Westerweel, Jerry; Elsinga, Gerrit E.


    Two 3D-3C velocimetry techniques for micro-scale measurements are compared: tomographic particle image velocimetry (Tomo-PIV) and 3D particle-tracking velocimetry (3D-PTV). Both methods are applied to experimental data from a confined shear-driven liquid droplet over a moving surface. The droplet has 200 μm height and 2 mm diameter. Micro 3D-PTV and Tomo-PIV are used to obtain the tracer particle distribution and the flow velocity field for the same set of images. It is shown that the reconstructed particle distributions are distinctly different, where Tomo-PIV returns a nearly uniform distribution over the height of the volume, as expected, and PTV reveals a clear peak in the particle distribution near the plane of focus. In Tomo-PIV, however, the reconstructed particle peak intensity decreases in proportion to the distance from the plane of focus. Due to the differences in particle distributions, the measured flow velocities are also different. In particular, we observe Tomo-PIV to be in closer agreement with mass conservation. Furthermore, the random noise level is found to increase with distance to the plane of focus at a higher rate for 3D-PTV as compared to Tomo-PIV. Thus, for a given noise threshold value, the latter method can measure reliably over a thicker volume.

  20. Automated and temperature-controlled micro-PIV measurements enabling long-term-stable microchannel acoustophoresis characterization

    Augustsson, Per; Barnkob, Rune; Wereley, Steven T.


    We present a platform for micro particle image velocimetry (μPIV), capable of carrying out full-channel, temperature-controlled, long-term-stable, and automated μPIV-measurement of microchannel acoustophoresis with uncertainties below 5% and a spatial resolution in the order of 20 μm. A method...... to determine optimal μPIV-settings for obtaining high-quality results of the spatially inhomogeneous acoustophoretic velocity fields of large dynamical range is presented. In particular we study the dependence of the results on the μPIV interrogation window size and the number of repeated experiments. The μPIV......-method was further verified by comparing it with our previously published particle tracking method. Using the μPIV platform we present a series of high-resolution measurements of the acoustophoretic velocity field as a function of the driving frequency, the driving voltage, and the resonator temperature. Finally, we...

  1. Flow in a Low Specific Speed Centrifugal Pump Using PIV

    Cui Dai


    Full Text Available The interflow plays important roles in centrifugal pump design. In order to study the effect of rotation and z-axis on internal flow, two-dimensional particle image velocimetry (PIV measurements have been performed to measure the steady velocity field on three planes in all impeller passages of a low specific-speed centrifugal pump. The results show that the relative velocity flows in blade passages are obviously different in terms of the positions of the blade relative to the tongue. The interaction between the impeller and tongue changes the occurrence and development of low velocity region with time. From shroud to hub, the relative velocity gradually increases, and the minimum value moves toward the suction surface. On the midplane, the magnitude increases with increased flow rate from pressure surface to suction surface, while at the shroud and hub, the measured velocity first increases with decreased flow rate from the blade pressure surface to nearly ζ = 0.5 to 0.6.

  2. PIV measurements and flow characteristics downstream of mangrove root models

    Kazemi, Amirkhosro; Curet, Oscar


    Mangrove forests attracted attentions as a solution to protect coastal areas exposed to sea-level rising, frequent storms, and tsunamis. Mangrove forests found in tide-dominated flow regions are characterized by their massive and complex root systems, which play a prominent role in the structure of tidal flow currents. To understand the role of mangrove roots in flow structure, we modeled mangrove roots with rigid and flexible arrays of cylinders with different spacing between them as well as different configurations. In this work, we investigate the fluid dynamics downstream of the models using a 2-D time-resolved particle image velocimetry (PIV) and flow visualization. We carried out experiments for four different Reynolds number based on cylinder diameters ranges from 2200 to 12000. We present time-averaged and time-resolved flow parameters including velocity distribution, vorticity, streamline, Reynolds shear stress and turbulent kinetic energy. The results show that the flow structure has different vortex shedding downstream of the cylinders due to interactions of shear layers separating from cylinders surface. The spectral analysis of the measured velocity data is also performed to obtain Strouhal number of the unsteady flow in the cylinder wake.

  3. Accurate measurement of streamwise vortices using dual-plane PIV

    Waldman, Rye M.; Breuer, Kenneth S.


    Low Reynolds number aerodynamic experiments with flapping animals (such as bats and small birds) are of particular interest due to their application to micro air vehicles which operate in a similar parameter space. Previous PIV wake measurements described the structures left by bats and birds and provided insight into the time history of their aerodynamic force generation; however, these studies have faced difficulty drawing quantitative conclusions based on said measurements. The highly three-dimensional and unsteady nature of the flows associated with flapping flight are major challenges for accurate measurements. The challenge of animal flight measurements is finding small flow features in a large field of view at high speed with limited laser energy and camera resolution. Cross-stream measurement is further complicated by the predominately out-of-plane flow that requires thick laser sheets and short inter-frame times, which increase noise and measurement uncertainty. Choosing appropriate experimental parameters requires compromise between the spatial and temporal resolution and the dynamic range of the measurement. To explore these challenges, we do a case study on the wake of a fixed wing. The fixed model simplifies the experiment and allows direct measurements of the aerodynamic forces via load cell. We present a detailed analysis of the wake measurements, discuss the criteria for making accurate measurements, and present a solution for making quantitative aerodynamic load measurements behind free-flyers.

  4. See Through the Static: 3D Synthetic Aperture PIV

    Belden, Jesse; Truscott, Tadd T.; Techet, Alexandra H.


    A new method for resolving three-dimensional (3D) fluid velocity fields using a technique called synthetic aperture particle image velocimetry (PIV) is presented. The method makes use of the lightfield imaging and synthetic aperture refocusing techniques that are emerging in the imaging community. Images are captured using an array of cameras positioned on one plane such that the fields of view of the cameras overlap and images can be easily recombined in software using a warp-shift-average algorithm to digitally refocus on different planes. The result is sharply focused particles in the plane of interest, whereas particles out-of-plane appear blurred. The 3D intensity field of particle-laden flows can be reconstructed by refocusing throughout the entire volume and filtering out the blurred particles. 3DPIV techniques can then be applied to these intensity fields to extract velocity data. This technique shows the potential of enabling larger volumes to be resolved with more particles, yielding higher spatial resolution than existing methods. A simulated vortex ring flow field demonstrates the capability of the technique for resolving vector fields in 3D.

  5. Atmospheric flow measurements using the PIV and HWA techniques

    Luciana Bassi Marinho Pires


    Full Text Available Alcântara Space Center (ASC is the Brazilian gate to the space where rockets of different sizes are launched. At ASC there is a relative topographical variation, coastal cliff, which modifies the atmospheric boundary layer characteristics and can cause interference for operations of rockets. In the present work, a simplified model (mock-up was studied in a wind tunnel. A scale factor of 1:1000 was used and the atmospheric flow was measured using the hot wire anemometer (HWA and particle image velocimetry (PIV techniques. Using of HWA it was possible to calculate values of average wind speed and fluctuations in a set of points of the section of tests that representing the region of the ASC. Through these measures, other meteorological parameters that represent the atmospheric flow, such as the friction velocity (u*, the roughness length (z0 from the logarithmic profile and the alpha exponent (ɑ of the power law were calculated. With the use of the PIV´s technique, the streamlines and the vorticity fields were obtained and it was noticed that the vorticity generated downwind of the coastal cliff has a strong turbulence (vorticities around 2000 sˉ¹. A rectangular building (simulating the mobile integration tower was inserted at the mock-up and the downwind turbulence was similar to the one generated by the coastal cliff.

  6. A fast multi-resolution approach to tomographic PIV

    Discetti, Stefano; Astarita, Tommaso [University of Naples Federico II, Department of Aerospace Engineering (DIAS), Naples (Italy)


    Tomographic particle image velocimetry (Tomo-PIV) is a recently developed three-component, three-dimensional anemometric non-intrusive measurement technique, based on an optical tomographic reconstruction applied to simultaneously recorded images of the distribution of light intensity scattered by seeding particles immersed into the flow. Nowadays, the reconstruction process is carried out mainly by iterative algebraic reconstruction techniques, well suited to handle the problem of limited number of views, but computationally intensive and memory demanding. The adoption of the multiplicative algebraic reconstruction technique (MART) has become more and more accepted. In the present work, a novel multi-resolution approach is proposed, relying on the adoption of a coarser grid in the first step of the reconstruction to obtain a fast estimation of a reliable and accurate first guess. A performance assessment, carried out on three-dimensional computer-generated distributions of particles, shows a substantial acceleration of the reconstruction process for all the tested seeding densities with respect to the standard method based on 5 MART iterations; a relevant reduction in the memory storage is also achieved. Furthermore, a slight accuracy improvement is noticed. A modified version, improved by a multiplicative line of sight estimation of the first guess on the compressed configuration, is also tested, exhibiting a further remarkable decrease in both memory storage and computational effort, mostly at the lowest tested seeding densities, while retaining the same performances in terms of accuracy. (orig.)

  7. Aeroacoustic source analysis using time-resolved PIV in a free jet

    Breakey, David E. S.; Fitzpatrick, John A.; Meskell, Craig


    Time-resolved particle image velocimetry (TR-PIV) has become a valuable tool for spatio-temporally resolved flow measurements. Current camera and laser technology has advanced such that time-domain events leading to sound generation can now be resolved over a reasonable spatial extent. This paper reports on the application of TR-PIV for the analysis of aeroacoustic sources in a free jet using the direct correlation between in-flow velocity fluctuations on the jet center-line and near-field pressure fluctuations. This correlation is considered both in the time domain and in the frequency domain (coherence), and the effect of TR-PIV errors on these estimates is considered by comparison to hot-wire anemometer measurements. In addition, a recently developed wavelet filtering technique is used to separate the acoustic and hydrodynamic components of recorded near-field pressure signals, enabling a gain in the signal-to-noise ratio. The results show that TR-PIV can recover the same time-domain correlation available from hot-wire and traditional PIV measurements, but that the frequency-domain estimates are corrupted by error, particularly at high frequencies. This result negates the principal benefit of using TR-PIV over PIV (the availability of coherence estimates). Despite this result, an analysis of the correlation signature gives evidence that large-scale, convecting, wave-like structures are associated with sound production, a result consistent with observations by many recent investigators. The analysis shows that in the presence of such large-scale structures, noise source localization based on the traditional correlation technique is ambiguous.

  8. A PIV-Guided Large-Eddy Simulation of In-Cylinder Flows

    Nicollet Franck


    Full Text Available A combination of Large-Eddy Simulation (LES and Particle Image Velocimetry (PIV was utilized to investigate the three-dimensional in-cylinder flow within an optically accessible Direct Injection Spark Ignition (DISI engine at motored engine operation. The PIV measurements were used to guide the meshing procedure by identifying the regions were refinements and improvements were needed. From the iteratively optimized meshes LES results are shown from two selected meshes, an intermediate coarse mesh and the final optimized mesh, and compared to PIV measurements. The evolution of the intake flow and the tumble in the central tumble plane during compression are presented and discussed. Exploitation of the LES results allowed showing the influence of out-of-plane velocities along the cylinder liner impacting the formation of the tumble flow. The optimized mesh was then used to investigate the influence of the spark plug on the in-cylinder flow. For the studied engine the spark plug had a significant impact on the evolution of the tumble flow during compression. Finally 35 engine cycles were simulated using the optimized mesh with the spark plug in place. Velocity distributions in a region below the spark plug are shown and compared with PIV results. The two-sample Kolmogorov-Smirnov test revealed a strong similarity between the velocity distributions obtained by PIV and LES, thus validating the potential of LES for investigating cycle-to-cycle variability.

  9. Portable tomographic PIV measurements of swimming shelled Antarctic pteropods

    Adhikari, Deepak; Webster, Donald R.; Yen, Jeannette


    A portable tomographic particle image velocimetry (tomographic PIV) system is described. The system was successfully deployed in Antarctica to study shelled Antarctic pteropods ( Limacina helicina antarctica)—a delicate organism with an unusual propulsion mechanism. The experimental setup consists of a free-standing frame assembled with optical rails, thus avoiding the need for heavy and bulky equipment (e.g. an optical table). The cameras, lasers, optics, and tanks are all rigidly supported within the frame assembly. The results indicate that the pteropods flap their parapodia (or "wings") downward during both power and recovery strokes, which is facilitated by the pitching of their shell. Shell pitching significantly alters the flapping trajectory, allowing the pteropod to move vertically and/or horizontally. The pronation and supination of the parapodia, together with the figure-eight motion during flapping, suggest similarities with insect flight. The volumetric velocity field surrounding the freely swimming pteropod reveals the generation of an attached vortex ring connecting the leading-edge vortex to the trailing-edge vortex during power stroke and a presence of a leading-edge vortex during recovery stroke. These vortex structures play a major role in accelerating the organism vertically and indicate that forces generated on the parapodia during flapping constitute both lift and drag. After completing each stroke, two vortex rings are shed into the wake of the pteropod. The complex combination of body kinematics (parapodia flapping, shell pitch, sawtooth trajectory), flow structures, and resulting force balance may be significantly altered by thinning of the pteropod shell, thus making pteropods an indicator of the detrimental effects of ocean acidification.

  10. PIV Application to Fluid Dynamics of Bass Reflex Ports

    Rossi, Massimiliano; Esposito, Enrico; Tomasini, Enrico Primo

    A bass reflex (or vented or ported) loudspeaker system (BRS) is a particular type of loudspeaker enclosure that makes use of the combination of two second-order mechanic/acoustic devices, i.e., the driver and a Helmotz resonator, in order to create a new system with reinforced emission in the low frequency region. The resonator is composed by the box itself in which one or more ports are present with suitable shapes and dimensions. This category of loudspeaker presents several advantages compared to closed-box systems such as higher efficiency and power, smaller dimensions and reduced distortion at lower frequencies. Notwithstanding these advantages, they present some drawbacks like more complexity and unloading of the cone below the tuning frequency. Moreover, at high power levels the airflow in the port(s) may generate unwanted noises due to turbulence as well as distortion and acoustic compression. In this work we will present and compare a series of experiments conducted on two different bass reflex ports designs to assess their performance in terms of flow turbulence and sound-level compression at high input power levels. These issues are quite important in professional sound systems, where increasing power levels and sound clarity require exponentially growing cost and weight. For these reasons it is vital to optimize port design. To the knowledge of the authors there does not exist an accurate, nonintrusive experimental full-field study of air flows emitting from reflex ports in operating conditions. In this work, the experimental fluid dynamic investigation has been conducted by means of PIV and LDA techniques.

  11. Kinematics and flow fields in 3D around swimming lamprey using light field PIV

    Lehn, Andrea M.; Techet, Alexandra H.


    The fully time-resolved 3D kinematics and flow field velocities around freely swimming sea lamprey are derived using 3D light field imaging PIV. Lighthill's Elongated Body Theory (EBT) predicts that swimmers with anguilliform kinematics likened to lamprey, and similarly eels, will exhibit relatively poor propulsive efficiency. However, previous experimental studies of eel locomotion utilizing 2D PIV suggest disagreement with EBT estimates of wake properties; although, the thrust force generated by such swimmers has yet to be fully resolved using 3D measurements. A light field imaging array of multiple high-speed cameras is used to perform 3D synthetic aperture PIV around ammocoete sea lamprey (Petromyzon marinus). Fluid mechanics equations are used to determine thrust force generation, leading experimental studies closer to underpinning the physical mechanisms that enable aquatic locomotion of long, slender undulatory swimmers.

  12. An overview of CFD and PIV application in investigation of solar thermal systems

    Ai, Ning; Fan, Jianhua; Ji, Jianbing


    Abstract:Solar thermal system is one of the most widely used technologies of renewable energy ipresently. In order to further improve the system design and to increase its performance,a deep understanding of the complicated fluid flow and heat transfer in the system components is necessary....... The most promising solution to this challenge is the use of computational fluid dynamics (CFD) in combination with particle image velocimetry (PIV),which will be the future trend in the investigation of solar thermal systems. The aim of this work is to give an overview of the status of the CFD......-PIV application in solar thermal systems. Key words: Solar thermal system,CFD,PIV...

  13. Errors in mean and fluctuating velocity due to PIV bias and precision uncertainties

    Wilson, B.; Smith, B.L. [Utah State Univ., Utah (United States)


    Particle Image Velocimetry is a powerful fluid velocity measurement tool that has recently become important for CFD validation experiments. Knowledge of experimental uncertainty is important to CFD validation, but the uncertainty of PIV is very complex and not well understood. Previous work has shown that PIV measurements can become 'noisy' in regions of high shear as well as regions of small displacement. This paper aims to demonstrate the impact of these effects on validation data by comparing PIV data to data acquired using hot-wire anemometry, which does not suffer from the same issues. It is confirmed that shear and insufficient particle displacements can result in elevated measurements of turbulence levels. (author)

  14. Investigation of a turbulent spot and a tripped turbulent boundary layer flow using time-resolved tomographic PIV

    Schröder, A.; Geisler, R.; Elsinga, G.E.; Scarano, F.; Dierksheide, U.


    In this feasibility study the tomographic PIV technique has been applied to time resolved PIV recordings for the study of the growth of a turbulent spot in a laminar flat plate boundary layer and to visualize the topology of coherent flow structures within a tripped turbulent flat plate boundary lay

  15. Direct calculation of depth of correlation and weighting function in μPIV from experimental particle images

    Hein, M.; Wieneke, B.; Seemann, R.


    Micro-PIVPIV) uses volume-illumination and imaging of fluorescent tracer particles through a single microscope objective. Displacement fields measured by image correlation depend on all imaged particles, including defocused particles. The measured in-plane displacement is a weighted average of th

  16. On the loss-of-correlation due to PIV image noise

    Scharnowski, Sven; Kähler, Christian J.


    The effect of image noise on the uncertainty of velocity fields measured with particle image velocimetry (PIV) is still an unsolved problem. Image noise reduces the correlation signal and thus affects the estimation of the particle image displacement. However, a systematic quantification of the effect of the noise level on the loss-of-correlation is missing. In this work, a new method is proposed to estimate the loss-of-correlation due to image noise F_{σ } from the autocorrelation function of PIV images. Furthermore, a new definition of the signal-to-noise ratio (SNR) for PIV images is suggested, which results in a bijective relation between F_{σ } and SNR. Based on the newly defined SNR, it becomes possible to estimate the signal level and the noise level itself. The presented method is very general because the estimation of F_{σ } and SNR works independently of various parameters, including the particle image intensity, the particle image density, the particle image size, the image noise distributions and the laser light-sheet profile. The findings lead to an extension of the fundamental PIV equation N=NI FI FO F_{Δ } and enable PIV users to optimize their measurement setup with respect to the image noise and not only based on the loss-of-correlation due to in-plane motion, out-of-plane motion and displacement gradients. Furthermore, the new definition of SNR allows for a characterization and comparison of PIV images. The new approaches are validated by using synthetic images, and the predictions are confirmed by using experimental data.

  17. High-resolution flying-PIV with optical fiber laser delivery

    Weichselbaum, Noah A.; André, Matthieu A.; Rahimi-Abkenar, Morteza; Manzari, Majid T.; Bardet, Philippe M.


    Implementation of non-intrusive optical measurement techniques, such as particle image velocimetry (PIV), in harsh environments requires specialized techniques for introducing controlled laser sheets to the region of interest. Large earthquake shake tables are a particularly challenging environment. Lasers must be mounted away from the table, and the laser sheet has to be delivered precisely and stably to the measurement station. Here, high-power multi-mode step-index fiber optics enable introduction of light from an Nd:YLF pulsed laser to a remote test section. Such lasers are suitable for coupling to optical fibers, which presents a portable, flexible, and safe manner to deliver a PIV light sheet. Best practices for their implementation are reviewed. Particular attention is focused on obtaining a collimated beam of acceptable quality at the output of the fiber. To achieve high spatial resolution, the PIV camera is directly mounted on the moving shake table with care to minimize its vibrations. A special arrangement of PIV planes is deployed for precise in-situ PIV alignment and to monitor and account for residual structure vibrations and beam wandering. The design of the instruments is detailed. Here, an experimental facility for the study of nuclear fuel bundle response to seismic forcing near prototypical conditions is instrumented. Only through integration of a high-resolution flying-PIV system can velocity fields be acquired. Data indicate that in the presence of a mean axial flow, a secondary oscillatory flow develops as the bundle oscillates. Instantaneous, phase-averaged, and fluctuating velocity fields illustrate this phenomenon.

  18. Automatic dynamic mask extraction for PIV images containing an unsteady interface, bubbles, and a moving structure

    Dussol, David; Druault, Philippe; Mallat, Bachar; Delacroix, Sylvain; Germain, Grégory


    When performing Particle Image Velocimetry (PIV) measurements in complex fluid flows with moving interfaces and a two-phase flow, it is necessary to develop a mask to remove non-physical measurements. This is the case when studying, for example, the complex bubble sweep-down phenomenon observed in oceanographic research vessels. Indeed, in such a configuration, the presence of an unsteady free surface, of a solid-liquid interface and of bubbles in the PIV frame, leads to generate numerous laser reflections and therefore spurious velocity vectors. In this note, an image masking process is developed to successively identify the boundaries of the ship and the free surface interface. As the presence of the solid hull surface induces laser reflections, the hull edge contours are simply detected in the first PIV frame and dynamically estimated for consecutive ones. As for the unsteady surface determination, a specific process is implemented like the following: i) the edge detection of the gradient magnitude in the PIV frame, ii) the extraction of the particles by filtering high-intensity large areas related to the bubbles and/or hull reflections, iii) the extraction of the rough region containing these particles and their reflections, iv) the removal of these reflections. The unsteady surface is finally obtained with a fifth-order polynomial interpolation. The resulted free surface is successfully validated from the Fourier analysis and by visualizing selected PIV images containing numerous spurious high intensity areas. This paper demonstrates how this data analysis process leads to PIV images database without reflections and an automatic detection of both the free surface and the rigid body. An application of this new mask is finally detailed, allowing a preliminary analysis of the hydrodynamic flow.

  19. PIV and LDA measurements of the wake behind a wind turbine model

    Naumov, I. V.; Mikkelsen, Robert Flemming; Okulov, Valery


    diameters downstream from the rotor. The initial flume flow was subject to a very low turbulence level with a uniform velocity profile, limiting the influence of external disturbances on the development of the inherent vortex instability. Using PIV measurements and visualizations, special attention was paid...... to detect and categorize different types of wake instabilities and the development of the flow in the near and the far wake. In parallel to PIV, LDA measurements provided data for various rotor regimes, revealing the existence of three main regular frequencies governing the development of different...

  20. PIV-measured versus CFD-predicted flow dynamics in anatomically realistic cerebral aneurysm models.

    Ford, Matthew D; Nikolov, Hristo N; Milner, Jaques S; Lownie, Stephen P; Demont, Edwin M; Kalata, Wojciech; Loth, Francis; Holdsworth, David W; Steinman, David A


    Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement

  1. Investigations on LED illumination for micro-PIV including a novel front-lit configuration

    Hagsäter, Melker; Bruus, Henrik; Kutter, Jörg Peter


    In this study, we provide a general investigation on micro-PIV with LED illumination. A number of improvements over previous LED-based systems are suggested, in particular, we present a novel front-lit configuration. As a demonstration of its versatility we have used this front-lit configuration...... to perform micro-PIV measurements around a 50 mu m squared pillar in a micro-channel with rectangular cross section, in both fluorescent mode and scattered mode. A comparison between the two modes is supplied, showing very good agreement between the respective velocity field results....

  2. Analysis on cold air circulation of a domestic refrigerator freezer by PIV animation

    Kim, J.Y.; Yang, C.J.; Kim, J.H. [Korea Maritime University Graduate School, Pusan (Korea); Lee, Y.H. [Korea Maritime University, Pusan (Korea)


    Animation technique from the PIV database is particularly emphasized to give macroscopic and quantitative description of complex flow fields. As an example, an experimental study was carried out investigate the fundamental flow characteristics of the freezer within the domestic refrigerator. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. Image intensifier CCD camera to cope with illumination problem is arranged for the accurate PIV measurement of large flow field. As a results, continuous pictures of the spatial distribution of the instantaneous and time-mean velocity distribution are displayed in real-time sense. (author). 5 refs., 5 figs., 1 tab.

  3. Stereoscopic reconstruction of 3D PIV data in T-junction with circular profile

    Jašíková D.


    Full Text Available In this paper experimental study of flow in T-junction using 3D PIV method is presented. Motion of seeding particles was recorded by a pair of suitably located cameras in precisely defined cross sections of the junction. Based on this information, three-dimensional model of flow in different sections of junction was reconstructed. The reconstruction results from the projection matrixes of each camera, which are obtained from positions of objects in the scene and their projection positions in the image plane. Standard 3D PIV reconstruction was rejected, because of optical distortion in T-Junction.

  4. Acceleration of Tomo-PIV by estimating the initial volume intensity distribution

    Worth, N. A.; Nickels, T. B.


    Tomographic particle image velocimetry (Tomo-PIV) is a promising new PIV technique. However, its high computational costs often make time-resolved measurements impractical. In this paper, a new preprocessing method is proposed to estimate the initial volume intensity distribution. This relatively inexpensive “first guess” procedure significantly reduces the computational costs, accelerates solution convergence, and can be used directly to obtain results up to 35 times faster than an iterative reconstruction algorithm (with only a slight accuracy penalty). Reconstruction accuracy is also assessed by examining the errors in recovering velocity fields from artificial data (rather than errors in the particle reconstructions themselves).

  5. Determine of velocity field with PIV and CFD during the flow around of bridge piers

    Picka D.


    Full Text Available The article describes the processing of specific junior research FAST-J-11-51/1456 which dealt with physical and CFD of the velocity field during the flow around of bridge piers. Physical modelling has been carried out in Laboratory of water management research in Institute of Water Structures in Brno University of Technology – Faculty of Civil Engineering. To measure of the velocity field in profile of bridge piers were used laser measuring method PIV (Particle Image Velocimetry. The results of PIV served as a basis for comparing experimental data with CFD results of this type of flow in the commercial software ANSYS CFX.

  6. Measurements of cylinder’s wake by Tomo-PIV%圆柱尾流场的 Tomo-PIV 测量

    许相辉; 蒋甲利; 牛中国; 宁继鹏; 刘捷


    Tomographic particle image velocimetry (Tomo-PIV)is an advanced optical meas-urement technology,which can acquire three-dimensional three-components (3D3C)flow field structure quantitatively in a complete volume,and can be used as an effective method on turbu-lence,vortex interference and other complex three-dimensional flow field measurement.In order to achieve the measurement application of Tomo-PIV in the FL-5 wind tunnel with 1.5m diame-ter test section of AVIC Aerodynamics Research Institute,the wake of a cylinder with 12mm di-ameter is investigated by means of Tomo-PIV.The flow speed is 15m/s,the measurement vol-ume is illuminated by a 2 ×200 mJ laser,and four 2048 ×2048 pixels CCD cameras with 85mm lens are used to record particles images from different directions.By solving a series of engineer-ing problems,such as diffusion of particles and optical path design,we successfully obtained the Karman rollers flow structure of the cylinder’s wake.Then,we studied the method of the data processing.The measurement volume extends approximately over a region of 95mm×70mm× 8.5mm with the shortest side in the direction of the depth of field,and the particle image spatial resolution is about 20 pixels/mm.There are tens of thousands of vectors recorded at every snap-shot.We can obtain a lot of information about the flow field by Tomo-PIV,much more than that obtained by 2D PIV or stereo-PIV measurement.%层析粒子图像测速(Tomo-PIV)是一种先进的光学测量技术,能够定量获取三维体视流场结构,可作为诸如湍流、多涡系干扰等三维复杂流场的有效测量手段。为了实现该技术在风洞模型测量中的应用,研究了工程应用和数据处理方法。在中航工业气动院 FL-5风洞,选取12mm 直径的圆柱体作为试验模型,应用 Tomo-PIV 技术测量了圆柱三维尾流场,通过解决体光源引入、示踪粒子投放和现场标定等关键技术以及对数据处理方法的研究,成

  7. Entwicklung und lmplementierung von Analysemethoden zum Erfassen vonGeschwindigkeitsfeldem mit dem PIV Verfahren (Development and Implementation of Analytical Methods for Detecting Velocity Fields using PIV- Method)


    German, Particle-Image-Yelocimetry (PIV), flow fields, Linear Programming, velocities, cross coiTelation 17. SECURITY CLASSI FICATION 18. SECURITY ...CLASS IFICATION 19, SECURITY CLASS IFICATION OF REPORT OF THIS PAGE OF ABSTRACT UNCLASS IFIED UNCLASS IFIED UNCLASS IFI ED NSN 7540-01-280-5500 15...ikel mittels Kreuzkorrelationsfunkt ion der Bilddat en. Hierzu muss das Bild gerastert werden . Die neu entwickelten Verfahren weisen den Partikeln

  8. Effect of random errors in planar PIV data on pressure estimation in vortex dominated flows

    McClure, Jeffrey; Yarusevych, Serhiy


    The sensitivity of pressure estimation techniques from Particle Image Velocimetry (PIV) measurements to random errors in measured velocity data is investigated using the flow over a circular cylinder as a test case. Direct numerical simulations are performed for ReD = 100, 300 and 1575, spanning laminar, transitional, and turbulent wake regimes, respectively. A range of random errors typical for PIV measurements is applied to synthetic PIV data extracted from numerical results. A parametric study is then performed using a number of common pressure estimation techniques. Optimal temporal and spatial resolutions are derived based on the sensitivity of the estimated pressure fields to the simulated random error in velocity measurements, and the results are compared to an optimization model derived from error propagation theory. It is shown that the reductions in spatial and temporal scales at higher Reynolds numbers leads to notable changes in the optimal pressure evaluation parameters. The effect of smaller scale wake structures is also quantified. The errors in the estimated pressure fields are shown to depend significantly on the pressure estimation technique employed. The results are used to provide recommendations for the use of pressure and force estimation techniques from experimental PIV measurements in vortex dominated laminar and turbulent wake flows.

  9. Geometry effect of isolated roughness on boundary layer transition investigated by tomographic PIV

    Ye, Q.; Schrijer, F.F.J.; Scarano, F.


    Transitional flow over isolated roughness elements is investigated in the incompressible flow regime using Tomographic PIV. Three different geometries are considered (micro-ramp, cylinder and square) with same height and span. Their effect on accelerating boundary layer transition is compared and di

  10. A super-resolution approach for uncertainty estimation of PIV measurements

    Sciacchitano, A.; Wieneke , B.; Scarano, F.


    A super-resolution approach is proposed for the a posteriori uncertainty estimation of PIV measurements. The measured velocity field is employed to determine the displacement of individual particle images. A disparity set is built from the residual distance between paired particle images of

  11. Distributed Processing of PIV images with a low power cluster supercomputer

    Smith, Barton; Horne, Kyle; Hauser, Thomas


    Recent advances in digital photography and solid-state lasers make it possible to acquire images at up to 3000 frames per second. However, as the ability to acquire large samples very quickly has been realized, processing speed has not kept pace. A 2-D Particle Image Velocimetry (PIV) acquisition computer would require over five hours to process the data that can be acquired in one second with a Time-resolved Stereo PIV (TRSPIV) system. To decrease the computational time, parallel processing using a Beowulf cluster has been applied. At USU we have developed a low-power Beowulf cluster integrated with the data acquisition system of a TRSPIV system. This approach of integrating the PIV system and the Beowulf cluster eliminates the communication time, thus speeding up the process. In addition to improving the practicality of TRSPIV, this system will also be useful to researchers performing any PIV measurement where a large number of samples are required. Our presentation will describe the hardware and software implementation of our approach.

  12. Flow Generated by an Aerated Rushton Impeller: Two-phase PIV Experiments and Numerical Simulations

    Deen, Niels G.; Solberg, Tron; Hjertager, H.


    A two-camera PIV technique was used to obtain angle resolved velocity and turbulence data of the flow in a lab-scale stirred tank, equipped with a Rushton turbine. Two cases were investigated: a single-phase flow and a gas-liquid flow. In the former case, the classical radial jet flow pattern accomp

  13. Comparison between PIV measurements and computations of the near-wake of an actuator disc

    Andersen, Søren Juhl; Lignarolo, L. E. M.; Ragni, D.


    Experimental stereoscopic PIV measurements in the wake of a two-bladed rotor and a porous actuator disc are compared to numerical simulation of an actuator disc. Compared to previous literature, the focus of the present analysis is on the near wake, where the actuator discs fail to represent...

  14. Flow structures in large-angle conical diffusers measured by PIV

    Meyer, Knud Erik; Nielsen, L.; Nielsen, N.F.


    Flow in two different conical diffusers with large opening angles (30° and 18°) have been measured with stereoscopic Particle Image Velocimetry (PIV). The measurements were done in a cross section just after the exit of the diffuser. The Reynolds number was 100000 based on upstream diameter...

  15. Hybrid PIV-PTV technique for measuring blood flow in rat mesenteric vessels.

    Ha, Hojin; Nam, Kweon-Ho; Lee, Sang Joon


    The micro-particle tracking velocimetry (μ-PTV) technique is used to obtain the velocity fields of blood flow in the microvasculature under in vivo conditions because it can provide the blood velocity distribution in microvessels with high spatial resolution. The in vivo μ-PTV technique usually requires a few to tens of seconds to obtain a whole velocity profile across the vessel diameter because of the limited number density of tracer particles under in vivo conditions. Thus, the μ-PTV technique alone is limited in measuring unsteady blood flows that fluctuate irregularly due to the heart beating and muscle movement in surrounding tissues. In this study, a new hybrid PIV-PTV technique was established by combining PTV and particle image velocimetry (PIV) techniques to resolve the drawbacks of the μ-PTV method in measuring blood flow in microvessels under in vivo conditions. Images of red blood cells (RBCs) and fluorescent particles in rat mesenteric vessels were obtained simultaneously. Temporal variations of the centerline blood velocity were monitored using a fast Fourier transform-based cross-correlation PIV method. The fluorescence particle images were analyzed using the μ-PTV technique to extract the spatial distribution of the velocity vectors. Data from the μ-PTV and PIV methods were combined to obtain a better estimate of the velocity profile in actual blood flow. This technique will be useful in investigating hemodynamics in microcirculation by measuring unsteady irregular blood flows more accurately.

  16. Investigation of airflow patterns in a microclimate by particle image velocimetry (PIV)

    Mortensen, Lone Hedegaard; Rode, Carsten; Peuhkuri, Ruut


    moisture production. The lack of air circulation decreases the surface temperature, which can cause problems. A particle image velocimetry (PIV) investigation was performed of the airflow patterns in such a microclimate. This paper describes the experimental set-up and the results. The results indicate...

  17. A fast all-in-one method for automated post-processing of PIV data.

    Garcia, Damien


    Post-processing of PIV (particle image velocimetry) data typically contains three following stages: validation of the raw data, replacement of spurious and missing vectors, and some smoothing. A robust post-processing technique that carries out these steps simultaneously is proposed. The new all-in-one method (DCT-PLS), based on a penalized least squares approach (PLS), combines the use of the discrete cosine transform (DCT) and the generalized cross-validation, thus allowing fast unsupervised smoothing of PIV data. The DCT-PLS was compared with conventional methods, including the normalized median test, for post-processing of simulated and experimental raw PIV velocity fields. The DCT-PLS was shown to be more efficient than the usual methods, especially in the presence of clustered outliers. It was also demonstrated that the DCT-PLS can easily deal with a large amount of missing data. Because the proposed algorithm works in any dimension, the DCT-PLS is also suitable for post-processing of volumetric three-component PIV data.

  18. Cross-Stream PIV Measurements of Jets With Internal Lobed Mixers

    Bridges, James; Wernet, Mark P.


    With emphasis being placed on enhanced mixing of jet plumes for noise reduction and on predictions of jet noise based upon turbulent kinetic energy, unsteady measurements of jet plumes are a very important part of jet noise studies. Given that hot flows are of most practical interest, optical techniques such as Particle Image Velocimetry (PIV) are applicable. When the flow has strong azimuthal features, such as those generated by chevrons or lobed mixers, traditional PIV, which aligns the measurement plane parallel to the dominant flow direction is very inefficient, requiring many planes of data to be acquired and stacked up to produce the desired flow cross-sections. This paper presents PIV data acquired in a plane normal to the jet axis, directly measuring the cross-stream gradients and features of an internally mixed nozzle operating at aircraft engine flow conditions. These nozzle systems included variations in lobed mixer penetration, lobe count, lobe scalloping, and nozzle length. Several cases validating the accuracy of the PIV data are examined along with examples of its use in answering questions about the jet noise generation processes in these nozzles. Of most interest is the relationship of low frequency aft-directed noise with turbulence kinetic energy and mean velocity.

  19. PIV Measurements of Full-Scale UH-60A Tip Vortices

    Yamauchi, Gloria K.


    The following presentation will give a description on experiments like installation, PIV measurements, and test conditions. It will also be giving the status of data processing, as well as, preliminary results. In addition, plans and present papers will also be discussed.

  20. PIV for the characterization of focused field induced acoustic streaming: seeding particle choice evaluation.

    Ben Haj Slama, Rafika; Gilles, Bruno; Ben Chiekh, Maher; Béra, Jean-Christophe


    This research evaluates the use of Particle Image Velocimetry (PIV) technique for characterizing acoustic streaming flow generated by High Intensity Focused Ultrasound (HIFU). PIV qualification tests, focusing on the seeding particle size (diameter of 5, 20 and 50μm) were carried out in degassed water subjected to a focused field of 550kHz-frequency with an acoustic pressure amplitude of 5.2, 10.5 and 15.7bar at the focus. This study shows that the ultrasonic field, especially the radiation force, can strongly affect seeding particle behavior. Large particles (50μm-diameter) are repelled from the focal zone and gathered at radiation pressure convergence lines on either side of the focus. The calculation of the acoustic radiation pressure applied on these particles explains the observed phenomenon. PIV measurements do not, therefore, properly characterize the streaming flow in this case. On the contrary, small particles (5μm-diameter) velocity measurements were in good agreement with the Computational Fluid Dynamics (CFD) simulations of the water velocity field. A simple criterion approximating the diameter threshold below which seeding particles are qualified for PIV in presence of focused ultrasound is then proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Flow investigation in sidewall aneurysm model using a novel PIV multi-time-lag method

    Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Lovblad, Karl-Olof; Mendes Pereira, Vitor; Farhat, Mohamed


    The intracranial aneurysm (IA) lesion is one of the main causes of intracranial hemorrhage in productive population. It is well known that the hemodynamic factors have large impact on both the IAs rupture and treatment efficacy based on flow diverter stents. Precise experimental investigations of blood flow in IAs using particle imaging velocimetry (PIV) are therefore strongly required in order to validate clinical treatments based on computational and clinical flow assessment tools. Due to the large variations of flow velocities in IAs, a single PIV measurement with a unique time lag between two consecutive images cannot provide a good level of precision in all the measured volume. In this work, we implement an error analysis based on several PIV measurements with different time lags to ensure an optimal precision in the entire measurement volume. This PIV multi-time-lag method is applied on a sidewall IA model to investigate the effect of the inflow pulsatility. By comparing the flow patterns resulting from steady and unsteady inflows we point out important differences which could be involved in the IAs evolution. In particular, the blood transfer in the IA and the vortical structure are significantly modified when increasing the pulsatility compared to quasi-steady conditions.

  2. A study on the application of two different acoustic analogies to experimental PIV data

    Koschatzky, V.; Westerweel, J.; Boersma, B.J.


    The aim of the present study is to compare two different acoustic analogies applied to time-resolved particle image velocimetry (PIV) data for the prediction of the acoustic far-field generated by the flow over a rectangular cavity. We consider the model problem of sound radiating from an open, two-

  3. Flow generated by an aerated rushton impeller: two-phase PIV experiments and numerical simulations

    Deen, N.G.; Solberg, Tron; Hjertager, H.


    A two-camera PIV technique was used to obtain angle resolved velocity and turbulence data of the flow in a lab-scale stirred tank, equipped with a Rushton turbine. Two cases were investigated: a single-phase flow and a gas-liquid flow. In the former case, the classical radial jet flow pattern accomp

  4. 3D organization of high-speed compressible jets by tomographic PIV

    Violato, D.; Ceglia, G.; Tuinstra, M.; Scarano, F.


    This work investigates the three dimensional organization of compressible jets at high-speed regime by tomographic particle image velocimetry (TOMO PIV). Experiments are conducted at Mach numbers 0.3, 0.9 and 1.1 (underexpanded regime) across the end of the potential core within a large cylindrica

  5. An experimental study of reconstruction accuracy using a 12-Camera Tomo-PIV system

    Lynch, K.; Scarano, F.


    A tomographic PIV system composed of a large number of cameras is used to experimentally investigate the relation between image particle density, number of cameras and the reconstruction quality. The large number of cameras allows to determine an asymptotic behavior for the object reconstruction ove

  6. Performances of motion tracking enhanced Tomo-PIV on turbulent shear flows

    Novara, M.; Scarano, F.


    The motion tracking enhancement technique (MTE) is a recently introduced method to improve the accuracy of tomographic PIV measurements at seeding density higher than currently practiced. The working principle is based on the fact that the particle field and its projections are correlated between th

  7. Volume reconstruction optimization for tomo-PIV algorithms applied to experimental data

    Martins, Fabio J. W. A.; Foucaut, Jean-Marc; Thomas, Lionel; Azevedo, Luis F. A.; Stanislas, Michel


    Tomographic PIV is a three-component volumetric velocity measurement technique based on the tomographic reconstruction of a particle distribution imaged by multiple camera views. In essence, the performance and accuracy of this technique is highly dependent on the parametric adjustment and the reconstruction algorithm used. Although synthetic data have been widely employed to optimize experiments, the resulting reconstructed volumes might not have optimal quality. The purpose of the present study is to offer quality indicators that can be applied to data samples in order to improve the quality of velocity results obtained by the tomo-PIV technique. The methodology proposed can potentially lead to significantly reduction in the time required to optimize a tomo-PIV reconstruction, also leading to better quality velocity results. Tomo-PIV data provided by a six-camera turbulent boundary-layer experiment were used to optimize the reconstruction algorithms according to this methodology. Velocity statistics measurements obtained by optimized BIMART, SMART and MART algorithms were compared with hot-wire anemometer data and velocity measurement uncertainties were computed. Results indicated that BIMART and SMART algorithms produced reconstructed volumes with equivalent quality as the standard MART with the benefit of reduced computational time.

  8. Large-scale tomo-PIV for on-site drag analysis in speed sports

    Terra, W.; Sciacchitano, A.; Scarano, F.


    Large-scale tomographic Particle Image Velocimetry is proposed as a tool for the on-site aerodynamic investigation in speed sports. The ring-of-fire concept is presented, which relies upon a tomographic PIV system used during the training of athletes in speed sports. The system consists of a short t

  9. On the velocity of ghost particles and the bias errors in Tomographic-PIV

    Elsinga, G.E.; Westerweel, J.; Scarano, F.; Novara, M.


    The paper discusses bias errors introduced in Tomographic-PIV velocity measurements by the coherent motion of ghost particles under some circumstances. It occurs when a ghost particle is formed from the same set of actual particles in both reconstructed volumes used in the cross-correlation analysis

  10. Rotor Wake Vortex Definition Using 3C-PIV Measurements: Corrected for Vortex Orientation

    Burley, Casey L.; Brooks, Thomas F.; vanderWall, Berend; Richard, Hughues Richard; Raffel, Markus; Beaumier, Philippe; Delrieux, Yves; Lim, Joon W.; Yu, Yung H.; Tung, Chee


    Three-component (3-C) particle image velocimetry (PIV) measurements, within the wake across a rotor disk plane, are used to determine wake vortex definitions important for BVI (Blade Vortex Interaction) and broadband noise prediction. This study is part of the HART II test program conducted using a 40 percent scale BO-105 helicopter main rotor in the German-Dutch Wind Tunnel (DNW). In this paper, measurements are presented of the wake vortex field over the advancing side of the rotor operating at a typical descent landing condition. The orientations of the vortex (tube) axes are found to have non-zero tilt angles with respect to the chosen PIV measurement cut planes, often on the order of 45 degrees. Methods for determining the orientation of the vortex axis and reorienting the measured PIV velocity maps (by rotation/projection) are presented. One method utilizes the vortex core axial velocity component, the other utilizes the swirl velocity components. Key vortex parameters such as vortex core size, strength, and core velocity distribution characteristics are determined from the reoriented PIV velocity maps. The results are compared with those determined from velocity maps that are not corrected for orientation. Knowledge of magnitudes and directions of the vortex axial and swirl velocity components as a function of streamwise location provide a basis for insight into the vortex evolution.

  11. PIV and pressure measurements on two high-rise models in tandem arrangement

    Bronkhorst, A.J.; Bentum, C.A. van; Geurts, C.P.W.; Jong, A. de


    Particle Image Velocimetry (PIV) and pressure measurements were performed on a highrise model with a height (H) of 0.48 m and a width (B) of 0.12 m in a turbulent atmospheric boundary layer. Experiments were carried out for an isolated model and four tandem configurations with varying separation dis

  12. Effect of predictor-corrector filtering on the stability and spatial resolution of iterative PIV interrogation

    Schrijer, F.F.J.; Scarano, F.


    The stability and resolution of iterative PIV image analysis methods is investigated. The study focuses on the effects of stabilization by means of spatial filtering when implemented into the iterative process. Two filtering approaches are studied: predictor and corrector filtering respectively. A

  13. Tomographic-PIV measurement of the flow around a zigzag boundary layer trip

    Elsinga, G.E.; Westerweel, J.


    Tomographic-PIV was used to measure the boundary layer transition forced by a zigzag trip. The resulting instantaneous three-dimensional velocity distributions are used to quantitatively visualize the flow structures. They reveal undulating spanwise vortices directly behind the trip, which break up

  14. PIV pictures of stream field predict haemolysis index of centrifugal pump with streamlined impeller.

    Qian, K X; Feng, Z G; Ru, W M; Zeng, P; Yuan, H Y


    Previously it has been found by pump haemolysis testing that the flow rate has a remarkable effect on index of haemolysis (IH), while pressure head does not affect IH. Recent investigation with particle image velocimetry (PIV) technology has demonstrated that IH is directly related to the flow pattern of stream field in impeller vane channels. PIV is a visible approach showing the real flow status in the pump. The different positions of a tracer particle in two PIV pictures taken at 20 micros intervals decide the velocity value and direction. The velocity vectors of many particles draw the flow pattern of the stream field. The same pictures are taken at 2, 4 and 6 l min(-1) flow rates while the pressure head is kept unchanged at 100 mmHg; then the pictures are taken at 4 l min(-1) flow with different pressure heads of 80, 100 and 120 mmHg. Results reveal that the flow rate of 4 l min(-1) (IH = 0.030) has the best stream field, and neither turbulence nor separation can be seen. In other flow rates (IH: 0.048 - 0.082), there is obviously second flow. Meanwhile, no significant difference can be seen among the PIV pictures of different pressure heads pumped, which agrees with the results of haemolysis testing showing that pressure has no effect on pump haemolysis. It may be concluded that the haemolysis property of a centrifugal pump can be assessed approximately by PIV pictures, which are much easier to take than haemolysis tests.

  15. Investigation of Unsteady Flow Behavior in Transonic Compressor Rotors with LES and PIV Measurements

    Hah, Chunill; Voges, Melanie; Mueller, Martin; Schiffer, Heinz-Peter


    In the present study, unsteady flow behavior in a modern transonic axial compressor rotor is studied in detail with large eddy simulation (LES) and particle image velocimetry (PIV). The main purpose of the study is to advance the current understanding of the flow field near the blade tip in an axial transonic compressor rotor near the stall and peak-efficiency conditions. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. Casing-mounted unsteady pressure transducers have been widely applied to investigate steady and unsteady flow behavior near the casing. Although many aspects of flow have been revealed, flow structures below the casing cannot be studied with casing-mounted pressure transducers. In the present study, unsteady velocity fields are measured with a PIV system and the measured unsteady flow fields are compared with LES simulations. The currently applied PIV measurements indicate that the flow near the tip region is not steady even at the design condition. This self-induced unsteadiness increases significantly as the compressor rotor operates near the stall condition. Measured data from PIV show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics of the flow from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The present study indicates that stall inception is heavily dependent on unsteady behavior of the flow field near the leading edge of the blade tip section for the present transonic compressor rotor.

  16. PIV measurements of near wake behind a U-grooved cylinder

    Lim, H.-C.; Lee, S.-J.


    The flow structure around a circular cylinder with U-grooved surfaces has been investigated experimentally. The results were compared with that of a smooth cylinder having the same diameter. Drag force and turbulence statistics of wake behind each cylinder were measured for Reynolds numbers based on the cylinder diameter (/D=60mm) in the range ReD=8×103-1.4×105. At ReD=1.4×105, the U-type grooves reduce the drag coefficient acting on the cylinder by 18.6%, compared with that of smooth cylinder. The flow characteristics of wake behind the U-grooved cylinder have been analyzed using two kinds of particle image velocimetry (PIV) velocity measurement techniques, cinematic PIV and high-resolution PIV. Consecutive instantaneous velocity fields were measured using the cinematic PIV technique at time interval of 5ms, corresponding to about 1% of the vortex shedding frequency of the wake. The instantaneous velocity fields measured with the high-resolution PIV technique were ensemble-averaged to get the spatial distributions of turbulent statistics including turbulent intensities and turbulent kinetic energy. For the case of smooth cylinder, large-scale vortices formed behind the cylinder maintain round shape and do not spread out noticeably in the near wake. However, for the case of U-grooved cylinder, the vortices are largely distorted and spread out significantly as they go downstream. The longitudinal grooves seem to shift the location of spanwise vortices toward the cylinder, reducing the vortex formation region, compared with the smooth cylinder. The sharp peaks of longitudinal U-shaped grooves also suppress the formation of large-scale secondary streamwise vortices. The secondary vortices are broken into smaller eddies, reducing turbulent kinetic energy in the near-wake region.

  17. Three-dimensional measurement and visualization of internal flow of a moving droplet using confocal micro-PIV.

    Kinoshita, Haruyuki; Kaneda, Shohei; Fujii, Teruo; Oshima, Marie


    This paper presents a micro-flow diagnostic technique, 'high-speed confocal micro-particle image velocimetry (PIV)', and its application to the internal flow measurement of a droplet passing through a microchannel. A confocal micro-PIV system has been successfully constructed wherein a high-speed confocal scanner is combined with the conventional micro-PIV technique. The confocal micro-PIV system enables us to obtain a sequence of sharp and high-contrast cross-sectional particle images at 2000 frames s(-1). This study investigates the confocal depth, which is a significant parameter to determine the out-of-plane measurement resolution in confocal micro-PIV. Using the present confocal micro-PIV system, we can measure velocity distributions of micro-flows in a 228 microm x 171 microm region with a confocal depth of 1.88 microm. We also propose a three-dimensional velocity measurement method based on the confocal micro-PIV and the equation of continuity. This method enables us to measure three velocity components in a three-dimensional domain of micro flows. The confocal micro-PIV system is applied to the internal flow measurement of a droplet. We have measured three-dimensional distributions of three-component velocities of a droplet traveling in a 100 microm (width) x 58 microm (depth) channel. A volumetric velocity distribution inside a droplet is obtained by the confocal micro-PIV and the three-dimensional flow structure inside the droplet is investigated. The measurement results suggest that a three-dimensional and complex circulating flow is formed inside the droplet.

  18. 基于 PIV 速度场测量重构压强场的研究进展%Bevelopment of PIV-based instantaneous pressure determination

    王勇; 陈鹏; 耿子海; 王万波; 李士伟


    Instantaneous planar pressure field calculation based on the velocity fields obtained from partical image velocimetry (PIV)measurement data is a new technique for the measurement of pressure field.Recent research results acquired in computation fluid dynamics and wind tunnel tests abroad have demonstrated the feasibility and significance of PIV-based instantaneous pres-sure determination.This paper presents a description of the fundamental operation principles of the methods addressing the different procedures for obtaining the local pressure gradient by local-ly applying the incompressible momentum equation (Lagrangian form and Eulerian form)and for the subsequent spatial integration to evaluate the planar pressure field from these pressure gradi-ents (an in-plane Poisson formulation and direct spatial integration).The influence of the viscous term in the incompressible momentum equation is discussed,with the conclusion that its effect on the local pressure gradient determination can generally be neglected and will therefore be omitted safely.In the second part of the present paper,some key technologies and current developments of the PIV-based instantaneous pressure determination are reported.It is revealed that the overall uncertainty in determining the error in pressure is dominated by errors in velocity measurement and thus the first key point to the success of determining the instantaneous planar pressure field is to obtain faithful velocity field from PIV as soon as possible.A comparative assessment of the Lagrangian approach and the Euleiran approach to determine the local pressure gradient is consid-ered,which would promote the use of the Lagrangian approach though they are found to have dif-ferent merits and demerits.For the two different methods to evaluate the pressure in a plane from the estimated pressure gradient,it is illustrated that the Poisson approach is clearly better than the direct spatial integration approach since the latter introduces a

  19. A comparative experimental evaluation of uncertainty estimation methods for two-component PIV

    Boomsma, Aaron; Bhattacharya, Sayantan; Troolin, Dan; Pothos, Stamatios; Vlachos, Pavlos


    Uncertainty quantification in planar particle image velocimetry (PIV) measurement is critical for proper assessment of the quality and significance of reported results. New uncertainty estimation methods have been recently introduced generating interest about their applicability and utility. The present study compares and contrasts current methods, across two separate experiments and three software packages in order to provide a diversified assessment of the methods. We evaluated the performance of four uncertainty estimation methods, primary peak ratio (PPR), mutual information (MI), image matching (IM) and correlation statistics (CS). The PPR method was implemented and tested in two processing codes, using in-house open source PIV processing software (PRANA, Purdue University) and Insight4G (TSI, Inc.). The MI method was evaluated in PRANA, as was the IM method. The CS method was evaluated using DaVis (LaVision, GmbH). Utilizing two PIV systems for high and low-resolution measurements and a laser doppler velocimetry (LDV) system, data were acquired in a total of three cases: a jet flow and a cylinder in cross flow at two Reynolds numbers. LDV measurements were used to establish a point validation against which the high-resolution PIV measurements were validated. Subsequently, the high-resolution PIV measurements were used as a reference against which the low-resolution PIV data were assessed for error and uncertainty. We compared error and uncertainty distributions, spatially varying RMS error and RMS uncertainty, and standard uncertainty coverages. We observed that qualitatively, each method responded to spatially varying error (i.e. higher error regions resulted in higher uncertainty predictions in that region). However, the PPR and MI methods demonstrated reduced uncertainty dynamic range response. In contrast, the IM and CS methods showed better response, but under-predicted the uncertainty ranges. The standard coverages (68% confidence interval) ranged from

  20. Error Propagation Dynamics of PIV-based Pressure Field Calculations: How well does the pressure Poisson solver perform inherently?

    Pan, Zhao; Whitehead, Jared; Thomson, Scott; Truscott, Tadd


    Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.

  1. Error Propagation Dynamics of PIV-based Pressure Field Calculations: How well does the pressure Poisson solver perform inherently?

    Pan, Zhao; Thomson, Scott; Truscott, Tadd


    Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.

  2. Error propagation dynamics of PIV-based pressure field calculations: How well does the pressure Poisson solver perform inherently?

    Pan, Zhao; Whitehead, Jared; Thomson, Scott; Truscott, Tadd


    Obtaining pressure field data from particle image velocimetry (PIV) is an attractive technique in fluid dynamics due to its noninvasive nature. The application of this technique generally involves integrating the pressure gradient or solving the pressure Poisson equation using a velocity field measured with PIV. However, very little research has been done to investigate the dynamics of error propagation from PIV-based velocity measurements to the pressure field calculation. Rather than measure the error through experiment, we investigate the dynamics of the error propagation by examining the Poisson equation directly. We analytically quantify the error bound in the pressure field, and are able to illustrate the mathematical roots of why and how the Poisson equation based pressure calculation propagates error from the PIV data. The results show that the error depends on the shape and type of boundary conditions, the dimensions of the flow domain, and the flow type.

  3. Automated and temperature-controlled micro-PIV measurements enabling long-term-stable microchannel acoustophoresis characterization.

    Augustsson, Per; Barnkob, Rune; Wereley, Steven T; Bruus, Henrik; Laurell, Thomas


    We present a platform for micro particle image velocimetry (μPIV), capable of carrying out full-channel, temperature-controlled, long-term-stable, and automated μPIV-measurement of microchannel acoustophoresis with uncertainties below 5% and a spatial resolution in the order of 20 μm. A method to determine optimal μPIV-settings for obtaining high-quality results of the spatially inhomogeneous acoustophoretic velocity fields of large dynamical range is presented. In particular we study the dependence of the results on the μPIV interrogation window size and the number of repeated experiments. The μPIV-method was further verified by comparing it with our previously published particle tracking method. Using the μPIV platform we present a series of high-resolution measurements of the acoustophoretic velocity field as a function of the driving frequency, the driving voltage, and the resonator temperature. Finally, we establish a direct and consistent connection between the obtained acoustophoretic velocity fields, and continuous flow mode acoustophoresis, commonly used in applications.

  4. Studying Vortex Dynamics of Rotating Convection with High-resolution PIV Measurement

    Fu, Hao; Sun, Shiwei; Wang, Yu; Zhou, Bowen; Wang, Yuan


    A novel experimental setup for studying vortex dynamics in rotating Rayleigh-Benard convection has been made in School of Atmospheric Sciences, Nanjing University. With water as the working fluid, three lasers with different frequencies and the corresponding three CCDs have been placed to complete 2D2C (two dimensions, two components) PIV measurement. The lasers are fixed on two crossing guiding ways and can move up and down to scan the flow field. An algorithm has been made to reconstruct 3D velocity field based on multiple 2D2C PIV data. This time, we are going to present the details of this new machine and algorithm, as well as some scientific understanding of vortex dynamics owing to this high-resolution velocity measurement system. This work was supported by "LMSWE Lab Funding No. 14380001".

  5. PIV and LIF study of slot continuous jet at low Reynolds number

    Broučková Zuzana


    Full Text Available This study deals with a continuous jet issuing from a small narrow slot with a width of 0.36 mm. The experimental arrangement is based on the piezoelectric synthetic jet actuator studied previously for easy comparisons. The working fluid is water at room temperature. The experiments were performed using methods of particle image velocimetry (PIV and flow visualization (laser induced fluorescence, LIF. The time-mean volume flux through the exit nozzle was quantified using precise scales. The mean velocity and the Reynolds number were evaluated as Um = 0.12 m/s and Re = 90, respectively. The results of LIF and PIV techniques revealed the three-dimensional character of the flow field, namely the saddle-shape velocity profiles. This behavior is typical for steady jets from a rectangular nozzle. The obtained results were compared with previous measurements of the synthetic jet issuing from the same cavity and the slot nozzle.

  6. Micro-PIV quantification of capillary blood flow redistribution caused by laser-assisted vascular occlusion

    Kurochkin, Maxim A.; Stiukhina, Elena S.; Fedosov, Ivan V.; Postnov, Dmitry E.; Tuchin, Valery V.


    We propose μPIV-based technique for quantitative assessment of blood flow redistribution in microcirculatory networks. Our approach is based on per-segment averaging of measured quantities so we can avoid most of problems that are typical for point-wise measurements. The key point of our technique is the digital processing algorithms of recorded data that include: capillary network axial line construction; interrogation regions centering; blood flow velocity local estimate using PIV approach; blood flow velocity calculation by means of averaging over entire vessel segment; the calculation of blood volume flow rate map. We illustrate the application of developed technique with in vivo measurements and blood flow velocity map reconstruction for chorioallantoic membrane (CAM) of chicken embryo, in which the local vascular occlusion was produced using continuous wave laser light irradiation..

  7. PIV measurements of coolant flow field in a diesel engine cylinder head

    Ma, Hongwei; Zhang, Zhenyang; Xue, Cheng; Huang, Yunlong


    This paper presents experimental measurements of coolant flow field in the water jacket of a diesel engine cylinder head. The test was conducted at three different flow rates using a 2-D PIV system. Appropriate tracing particles were selected and delivery device was designed and manufactured before the test. The flow parameters, such as velocity, vorticity and turbulence, were used to analyze the flow field. The effects of vortex which was located between the intake valve and the exhaust valve were discussed. The experimental results showed an asymmetric distribution of velocity in the water jacket. This led to an asymmetric thermal distribution, which would shorten the service life of the cylinder head. The structure optimization to the water jacket of cylinder head was proposed in this paper. The experimental system, especially the 2-D PIV system, is a great help to study the coolant flow structure and analyze cooling mechanism in the diesel engine cylinder head.

  8. Double large field stereoscopic PIV in a high Reynolds number turbulent boundary layer

    Coudert, S.; Foucaut, J. M.; Kostas, J.; Stanislas, M.; Braud, P.; Fourment, C.; Delville, J.; Tutkun, M.; Mehdi, F.; Johansson, P.; George, W. K.


    An experiment on a flat plate turbulent boundary layer at high Reynolds number has been carried out in the Laboratoire de Mecanique de Lille (LML, UMR CNRS 8107) wind tunnel. This experiment was performed jointly with LEA (UMR CNRS 6609) in Poitiers (France) and Chalmers University of Technology (Sweden), in the frame of the WALLTURB European project. The simultaneous recording of 143 hot wires in one transverse plane and of two perpendicular stereoscopic PIV fields was performed successfully. The first SPIV plane is 1 cm upstream of the hot wire rake and the second is both orthogonal to the first one and to the wall. The first PIV results show a blockage effect which based on both statistical results (i.e. mean, RMS and spatial correlation) and a potential model does not seem to affect the turbulence organization.

  9. Note on the POD-based time interpolation from successive PIV images

    Bouhoubeiny, Elkhadim; Druault, Philippe


    To enhance the temporal resolution of the PIV measurements of pseudo-periodic turbulent flows, Proper Orthogonal Decomposition (POD) has been previously used to time interpolate PIV database. In this note, it is demonstrated that such POD interpolation is equivalent to the classical mathematical interpolation when dealing with the whole POD eigenfunctions, since POD is a linear transform. In fact, the POD-based time interpolation is only valid for the large scale structures of the flow. The advantage of using POD procedure resides in its efficiency in extracting the dominant flow structures. In this sense, other interpolation methods such as turbulent filtering procedures could provide similar results. To cite this article: E. Bouhoubeiny, P. Druault, C. R. Mecanique 337 (2009).

  10. Validation of a CFD methodology for positive displacement LVAD analysis using PIV data.

    Medvitz, Richard B; Reddy, Varun; Deutsch, Steve; Manning, Keefe B; Paterson, Eric G


    Computational fluid dynamics (CFD) is used to asses the hydrodynamic performance of a positive displacement left ventricular assist device. The computational model uses implicit large eddy simulation direct resolution of the chamber compression and modeled valve closure to reproduce the in vitro results. The computations are validated through comparisons with experimental particle image velocimetry (PIV) data. Qualitative comparisons of flow patterns, velocity fields, and wall-shear rates demonstrate a high level of agreement between the computations and experiments. Quantitatively, the PIV and CFD show similar probed velocity histories, closely matching jet velocities and comparable wall-strain rates. Overall, it has been shown that CFD can provide detailed flow field and wall-strain rate data, which is important in evaluating blood pump performance.

  11. In vivo μPIV measurements of blood velocity in small vessels of a rat model

    Leong, Chia Min; Russell, John; Connor, Nadine; Honkanen, Markus; Wei, Timothy


    Aging-related muscular changes have been shown to affect voice production. There is correlation between muscular changes and changes in capillary hemodynamics and structure with aging. Alterations in oxygen transport to cells and tissues at the capillary level has been hypothesized as one of the key factors that causes muscular changes thus voice production. Since oxygen transport is related to hemodynamics, we start by measuring blood velocity in capillaries of cremaster muscle of a living rat. The μPIV technique is adapted for measuring blood velocity where red blood cells are used as `seeding particles'. The accuracy of the μPIV measurements are determined by comparison with results obtained using other techniques such as particle tracking velocimetry (PTV). Finally, challenges in measuring flow through three-dimensional larynx geometry will be discussed.

  12. Investigation of Internal Flow in Ultra—Highly Loaded Turbine Cascade by PIV Method

    A.Senoo; S.MizukiandH.Tsujita; 等


    The highly loaded turbine blades are able to reduce both the number of blades and the stages of turbojet-engines.In this study,PIV(Particle Image Velocimetry)method is used for the measuremts of the secondary flow in ultra-highly loaded tubine blade casecades.The results obtained by the PIV method clearly show the complicated behavior of the secondary flow in the cascade.The horseshoe vortex and the passage vortex are observed inside the cascade,Moreover.the wake generated by the accumulation of the low energy fluid by the passage vortex near the suction side and that discharged toward downstream of the trailing edge has been recognized.

  13. Simultaneous PIV and pulsed shadow technique in slug flow: a solution for optical problems

    Nogueira, S. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium); Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Sousa, R.G.; Pinto, A.M.F.R.; Campos, J.B.L.M. [Centro de Estudos de Fenomenos de Transporte, Departamento de Eng. Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto (Portugal); Riethmuller, M.L. [Karman Institute for Fluid Dynamics, Chaussee de Waterloo 72, B-1640, Rhode Saint Genese (Belgium)


    A recent technique of simultaneous particle image velocimetry (PIV) and pulsed shadow technique (PST) measurements, using only one black and white CCD camera, is successfully applied to the study of slug flow. The experimental facility and the operating principle are described. The technique is applied to study the liquid flow pattern around individual Taylor bubbles rising in an aqueous solution of glycerol with a dynamic viscosity of 113 x 10{sup -3} Pa s. With this technique the optical perturbations found in PIV measurements at the bubble interface are completely solved in the nose and in annular liquid film regions as well as in the rear of the bubble for cases in which the bottom is flat. However, for Taylor bubbles with concave oblate bottoms, some optical distortions appear and are discussed. The measurements achieved a spatial resolution of 0.0022 tube diameters. The results reported show high precision and are in agreement with theoretical and experimental published data. (orig.)

  14. Post-processing methods of PIV instantaneous flow fields for unsteady flows in turbomachines

    Cavazzini, G.; A. Dazin; Pavesi, G; Dupont, P; G. Bois


    The Particle Image Velocimetry is undoubtedly one of the most important technique in Fluid-dynamics since it allows to obtain a direct and instantaneous visualization of the flow field in a non-intrusive way. This innovative technique spreads in a wide number of research fields, from aerodynamics to medicine, from biology to turbulence researches, from aerodynamics to combustion processes. The book is aimed at presenting the PIV technique and its wide range of possible applications so as to p...

  15. PIV Uncertainty Methodologies for CFD Code Validation at the MIR Facility

    Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States); Skifton, Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States); Stoots, Carl [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kim, Eung Soo [Idaho National Lab. (INL), Idaho Falls, ID (United States); Conder, Thomas [Idaho National Lab. (INL), Idaho Falls, ID (United States)


    Currently, computational fluid dynamics (CFD) is widely used in the nuclear thermal hydraulics field for design and safety analyses. To validate CFD codes, high quality multi dimensional flow field data are essential. The Matched Index of Refraction (MIR) Flow Facility at Idaho National Laboratory has a unique capability to contribute to the development of validated CFD codes through the use of Particle Image Velocimetry (PIV). The significance of the MIR facility is that it permits non intrusive velocity measurement techniques, such as PIV, through complex models without requiring probes and other instrumentation that disturb the flow. At the heart of any PIV calculation is the cross-correlation, which is used to estimate the displacement of particles in some small part of the image over the time span between two images. This image displacement is indicated by the location of the largest peak. In the MIR facility, uncertainty quantification is a challenging task due to the use of optical measurement techniques. Currently, this study is developing a reliable method to analyze uncertainty and sensitivity of the measured data and develop a computer code to automatically analyze the uncertainty/sensitivity of the measured data. The main objective of this study is to develop a well established uncertainty quantification method for the MIR Flow Facility, which consists of many complicated uncertainty factors. In this study, the uncertainty sources are resolved in depth by categorizing them into uncertainties from the MIR flow loop and PIV system (including particle motion, image distortion, and data processing). Then, each uncertainty source is mathematically modeled or adequately defined. Finally, this study will provide a method and procedure to quantify the experimental uncertainty in the MIR Flow Facility with sample test results.

  16. Application of PIV to the Measurement of High Speed Jet Flows

    Lourenco, L.


    The Particle Image Velocimetry, PIV, has been implemented for the investigation of high-speed jet flows at the NASA Langley Research Center. In this approach the velocity (displacement) is found as the location of a peak in the correlation map of particle images acquired in quick succession. In the study, the technique for the correct seeding of the flow field were developed and implemented and the operational parameters influencing the accuracy of the measurement have been optimized.

  17. Comparison of Simultaneous PIV and Hydroxyl Tagging Velocimetry in Low Velocity Flows

    Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.


    Hydroxyl tagging velocimetry (HTV) is a molecular tagging velocimetry (MTV) technique that relies on the photo- dissociation of water vapor into OH radicals and their subsequent tracking using laser-induced fluorescence. At ambient temperature in air, the OH species lifetime is about 50 micro-s. The feasibility of using HTV for probing low- speed flows (a few m/s) is investigated by using an inert, heated gas as a means to increase the OH species lifetime. Unlike particle-based techniques, MTV does not suffer from tracer settling, which is particularly problematic at low speeds. Furthermore, the flow needs to be seeded with only a small mole fraction of water vapor, making it safer for both the user and facilities than other MTV techniques based on corrosive or toxic chemical tracers. HTV is demonstrated on a steam-seeded nitrogen jet at approximately 75 C in the laminar (Umean=3.31 m/s, Re=1,540), transitional (Umean=4.48 m/s, Re=2,039), and turbulent (Umean=6.91 m/s, Re=3,016) regimes at atmospheric pressure. The measured velocity profiles are compared with particle image velocimetry (PIV) measurements performed simultaneously with a second imager. Seeding for the PIV is achieved by introducing micron-sized water droplets into the flow with the steam; the same laser sheet is used for PIV and HTV to guarantee spatial and temporal overlap of the data. Optimizing each of these methods, however, requires conflicting operating conditions: higher temperatures benefit the HTV signals but reduce the available seed density for the PIV through evaporation. Nevertheless, data are found to agree within 10% for the instantaneous velocity profiles and within 5% for the mean profiles and demonstrate the feasibility of HTV for low-speed flows at moderate to high temperatures.

  18. Outbreak of Piv-3 in a Neonatal Intensive Care Unit in England.

    Dunn, Gemma Louise; Tapson, Helen; Davis, Jonathan; Gobin, Maya


    An outbreak of PIV-3 in a neonatal ICU was investigated using a retrospective cohort study. Risk of infection increased with lower birth weight and gestational age. Contact with sick visitor(s)/staff was not associated with infection (P = 0.212, P = 0.299). Transmission routes are difficult to identify, and the importance of visiting restrictions and sickness absence during outbreaks is recommended.

  19. An advection-based model to increase the temporal resolution of PIV time series.

    Scarano, Fulvio; Moore, Peter

    A numerical implementation of the advection equation is proposed to increase the temporal resolution of PIV time series. The method is based on the principle that velocity fluctuations are transported passively, similar to Taylor's hypothesis of frozen turbulence. In the present work, the advection model is extended to unsteady three-dimensional flows. The main objective of the method is that of lowering the requirement on the PIV repetition rate from the Eulerian frequency toward the Lagrangian one. The local trajectory of the fluid parcel is obtained by forward projection of the instantaneous velocity at the preceding time instant and backward projection from the subsequent time step. The trajectories are approximated by the instantaneous streamlines, which yields accurate results when the amplitude of velocity fluctuations is small with respect to the convective motion. The verification is performed with two experiments conducted at temporal resolutions significantly higher than that dictated by Nyquist criterion. The flow past the trailing edge of a NACA0012 airfoil closely approximates frozen turbulence, where the largest ratio between the Lagrangian and Eulerian temporal scales is expected. An order of magnitude reduction of the needed acquisition frequency is demonstrated by the velocity spectra of super-sampled series. The application to three-dimensional data is made with time-resolved tomographic PIV measurements of a transitional jet. Here, the 3D advection equation is implemented to estimate the fluid trajectories. The reduction in the minimum sampling rate by the use of super-sampling in this case is less, due to the fact that vortices occurring in the jet shear layer are not well approximated by sole advection at large time separation. Both cases reveal that the current requirements for time-resolved PIV experiments can be revised when information is poured from space to time. An additional favorable effect is observed by the analysis in the frequency

  20. Convection Study by PIV Method Within Horizontal Liquid Layer Evaporating Into Inert Gas Flow

    Kreta Aleksei


    Full Text Available The paper is devoted to the experimental study of convection in a horizontal evaporating liquid layer (ethanol of limited size under the action of gas flow (air. The two-dimensional velocity field in the liquid layer is obtained using the PIV method. The existence of a vortex convective flow within a liquid layer directed towards the gas flow has been revealed.

  1. Validating under-resolved turbulence intensities for PIV experiments in canonical wall-bounded turbulence

    Lee, J. H.; Kevin; Monty, J. P.; Hutchins, N.


    The discrepancy between measured turbulence intensity obtained from experiments in wall-bounded turbulence and the fully resolved reference results (usually from DNS datasets) are often attributed to spatial resolution issues, especially in PIV measurements due to the presence of spatial averaging within the interrogation region/volume. In many cases, in particular at high Reynolds numbers (where there is a lack of DNS data), there is no attempt to verify that this is the case. There is a risk that attributing unexpected PIV statistics to spatial resolution, without careful checks, could mask wider problems with the experimental setup or test facility. Here, we propose a robust technique to validate the under-resolved PIV obtained turbulence intensity profiles for canonical wall-bounded turbulence. This validation scheme is independent of Reynolds number and does not rely on empirical functions. It is based on arguments that (1) the viscous-scaled small-scale turbulence energy is invariant with Reynolds number and that (2) the spatially under-resolved measurement is sufficient to capture the large-scale energy. This then suggests that we can estimate the missing energy from volume-filtered DNS data at much lower Reynolds numbers. Good agreement is found between the experimental results and estimation profiles for all three velocity components, demonstrating that the estimation tool successfully computes the missing energy for given spatial resolutions over a wide range of Reynolds numbers. A database for a canonical turbulent boundary layer and associated MATLAB function are provided that enable this missing energy to be calculated across a range of interrogation volume sizes, so that users do not require access to raw DNS data. This methodology and tool will provide PIV practitioners, investigating canonical wall-bounded turbulent flow with a convenient check of the effects of spatial resolution on a given experiment.

  2. An Assessment of 3-C PIV Analysis Methodology for HART II Measured Data


    and Onera , with special thanks to Casey L. Burley, NASA Langley Research Center and Dr. Chee Tung, Emeritus Scientist of AFDD. The authors to thank Joelle Zibi, Onera for the Onera results presented in this report. We also would like to express our appreciation to Mr. Thomas Maier...and Space Administration ONERA Office National d‘Etudes et de Recherches Aerospatiales PIV Particle Image Velocimetry Pos Position SA Simple

  3. Design and CFD Simulation of the Drift Eliminators in Comparison with PIV Results

    Stodůlka Jiří


    Full Text Available Drift eliminators are the essential part of all modern cooling towers preventing significant losses of liquid water escaping to the enviroment. These eliminators need to be effective in terms of water capture but on the other hand causing only minimal pressure loss as well. A new type of such eliminator was designed and numerically simulated using CFD tools. Results of the simulation are compared with PIV visulisation on the prototype model.

  4. Flow field study in a bulb turbine runner using LDV and endoscopic S-PIV measurements

    Lemay, S.; Fraser, R.; Ciocan, G. D.; Aeschlimann, V.; Deschênes, C.


    The flow in the inter-blade channels of a bulb turbine was measured using two different techniques. The first involved a classical laser Doppler velocimetry (LDV) setup whereas the second integrated endoscopic cameras to a stereoscopic particle image velocimetry (S-PIV) system. This paper presents results from both measurement campaigns and also provides some key conclusions based on the two datasets. Before getting into the thick of the data though, the technical aspect of both measurement configurations is addressed. A quick overview of the LDV setup is presented, but the main focus is on the novelties and challenges brought by the use of endoscopic cameras to achieve S-PIV measurements between the runner blades. Endoscopic PIV systems have already led to successful measurements of flow fields in a few studies concerning turbomachinery, especially in aerodynamics. However, to the author's knowledge, the realisation of such measurements in a hydraulic turbine is a first. After this outline of the techniques used, the results and conclusions are shown. First, the influence of the guide vanes wakes on the runner flow is described. The size, localisation, strength and dissipation of those structures are inferred from the information coming from both measurement techniques. Then, a flow imbalance is assessed circumferentially. On another subject, the blade tip vortices are identified and characterized using the LDV data. The size, position and direction of rotation of those structures are all extracted from the measured flow field. Finally, the PIV data allows the identification of yet another vortex located near the suction side of the blades and originating from the corner between the leading edge and the hub when operating the bulb turbine at part load.

  5. 3D velocity measurements in a premixed flame by tomographic PIV

    Tokarev, M. P.; Sharaborin, D. K.; Lobasov, A. S.; Chikishev, L. M.; Dulin, V. M.; Markovich, D. M.


    Tomographic particle image velocimetry (PIV) has become a standard tool for 3D velocity measurements in non-reacting flows. However, the majority of the measurements in flows with combustion are limited to small resolved depth compared to the size of the field of view (typically 1 : 10). The limitations are associated with inhomogeneity of the volume illumination and the non-uniform flow seeding, the optical distortions and errors in the 3D calibration, and the unwanted flame luminosity. In the present work, the above constraints were overcome for the tomographic PIV experiment in a laminar axisymmetric premixed flame. The measurements were conducted for a 1 : 1 depth-to-size ratio using a system of eight CCD cameras and a 200 mJ pulsed laser. The results show that camera calibration based on the triangulation of the tracer particles in the non-reacting conditions provided reliable accuracy for the 3D image reconstruction in the flame. The modification of the tomographic reconstruction allowed a posteriori removal of unwanted bright objects, which were located outside of the region of interest but affected the reconstruction quality. This study reports on a novel experience for the instantaneous 3D velocimetry in laboratory-scale flames by using tomographic PIV.

  6. Time resolved PIV and flow visualization of 3D sheet cavitation

    Foeth, E.J.; Doorne, C.W.H. van; Terwisga, T. van [Delft University of Technology, Laboratory of Ship Hydromechanics, Delft (Netherlands); Wieneke, B. [LaVision GmbH, Goettingen (Germany)


    Time-resolved PIV was applied to study fully developed sheet cavitation on a hydrofoil with a spanwise varying angle of attack. The hydrofoil was designed to have a three-dimensional cavitation pattern closely related to propeller cavitation, studied for its adverse effects as vibration, noise, and erosion production. For the PIV measurements, fluorescent tracer particles were applied in combination with an optical filter, in order to remove the reflections of the laser lightsheet by the cavitation. An adaptive mask was developed to find the interface between the vapor and liquid phase. The velocity at the interface of the cavity was found to be very close to the velocity predicted by a simple streamline model. For a visualization of the global flow dynamics, the laser beam was expanded and used to illuminate the entire hydrofoil and cavitation structure. The time-resolved recordings reveal the growth of the attached cavity and the cloud shedding. Our investigation proves the viability of accurate PIV measurements around developed sheet cavitation. The presented results will further be made available as a benchmark for the validation of numerical simulations of this complicated flow. (orig.)


    Yang Hua; Gu Chuangang; Wang Tong


    A special transparent centrifugal pump is designed. Detailed optical measurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pump impeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow is surveyed at three load conditions qv/qνd = 0.4, qν/qνd = 1.0, qν/qνd = 1.5, respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub and shroud of the impeller are presented. At design load, the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow without separation. The distributions of the relative velocity on different plane along the pump shaft are very different and there is always a low velocity zone near the pressure-side of the blade at both low and design flow rate, but the low-velocity-zone at the low flow rate is much larger than that at the design one. The study demonstrates that the PIV technique is efficient in providing reliable and detailed velocity data over a full impeller passage.

  8. CFD and PIV analysis of hemodynamics in a growing intracranial aneurysm.

    Raschi, Marcelo; Mut, Fernando; Byrne, Greg; Putman, Christopher M; Tateshima, Satoshi; Viñuela, Fernando; Tanoue, Tetsuya; Tanishita, Kazuo; Cebral, Juan R


    Hemodynamics is thought to be a fundamental factor in the formation, progression, and rupture of cerebral aneurysms. Understanding these mechanisms is important to improve their rupture risk assessment and treatment. In this study, we analyze the blood flow field in a growing cerebral aneurysm using experimental particle image velocimetry (PIV) and computational fluid dynamics (CFD) techniques. Patient-specific models were constructed from longitudinal 3D computed tomography angiography images acquired at 1-y intervals. Physical silicone models were constructed from the computed tomography angiography images using rapid prototyping techniques, and pulsatile flow fields were measured with PIV. Corresponding CFD models were created and run under matching flow conditions. Both flow fields were aligned, interpolated, and compared qualitatively by inspection and quantitatively by defining similarity measures between the PIV and CFD vector fields. Results showed that both flow fields were in good agreement. Specifically, both techniques provided consistent representations of the main intra-aneurysmal flow structures and their change during the geometric evolution of the aneurysm. Despite differences observed mainly in the near wall region, and the inherent limitations of each technique, the information derived is consistent and can be used to study the role of hemodynamics in the natural history of intracranial aneurysms.

  9. Simultaneous measurements of jellyfish bell kinematics and flow fields using PTV and PIV

    Xu, Nicole; Dabiri, John


    A better understanding of jellyfish swimming can potentially improve the energy efficiency of aquatic vehicles or create biomimetic robots for ocean monitoring. Aurelia aurita is a simple oblate invertebrate composed of a flexible bell and coronal muscle, which contracts to eject water from the subumbrellar volume. Jellyfish locomotion can be studied by obtaining body kinematics or by examining the resulting fluid velocity fields using particle image velocimetry (PIV). Typically, swim kinematics are obtained by semi-manually tracking points of interest (POI) along the bell in video post-processing; simultaneous measurements of kinematics and flows involve using this semi-manual tracking method on PIV videos. However, we show that both the kinematics and flow fields can be directly visualized in 3D space by embedding phosphorescent particles in animals free-swimming in seeded environments. Particle tracking velocimetry (PTV) can then be used to calculate bell kinematics, such as pulse frequency, bell deformation, swim trajectories, and propulsive efficiency. By simultaneously tracking POI within the bell and collecting PIV data, we can further study the jellyfish's natural locomotive control mechanisms in conjunction with flow measurements. NSF GRFP.



    The instantaneous flow characteristics of circular orifice synthetic jet was experimentally studied by a phase-locked Particle Image Velocimetry (PIV) system. The instantaneous flowfields, including the forming, developing and breaking down of the vortex for the jet were clearly shown by the PIV experimental results. As the basis of the study of the instantaneous flow, 36 images were taken and phase-averaged for each condition. The PIV experiment was mainly focused on the time evolution of the vortex pairs formed in the push cycle, the saddle point existing in the suck cycle, the variation of the centerline velocity in the whole cycle and the cross-stream velocity profiles and their self-similarity. Finally, the orifice depth was changed from 1.5 mm to 2 mm and 3.5 mm in order to study the effect of different orifice depths on the flow structure, which shows that at all stream wise sections, the peak of the mass flux and momentum flux increases as the orifice depth increases. Furthermore, the nondimensional distance of the mass flux from the exit is the maximum, while the nondimensional distance of the centerline velocity peak from the exit is the minimum, and nondimensional distance of the momentum flux from the exit section is between them.

  11. Measurement of high-speed water column inside a Steam Injector using Dynamic PIV

    Okamoto, Koji; Narabayashi, Sunao; Mori, Michitsugu


    The Steam Injector is the superior system to pump the fluid without rotating machine. Because the water column is surrounded by the saturated steam, very high heat transfer is also expected with direct condensation. The inside of the Steam Injector is very complicated. To improve the efficiency of the Steam Injector, the water column behavior inside the Injector is visualized using the Dynamic PIV system. Dynamic PIV system consists of the high-speed camera and lasers. In this study, 384x180 pixel resolution with 30,000fps camera is used to visualize the flow. For the illumination CW green laser with 300mW is applied. To view inside the Injector, relay lens system is set at the Injector wall. Very high speed water column during the starting up of Steam Injector had been clearly visualized with 30,000fps. The wave velocity on the water column had been analyzed using PIV technique. The instability of the water column is also detected.

  12. A robust vector field correction method via a mixture statistical model of PIV signal

    Lee, Yong; Yang, Hua; Yin, Zhouping


    Outlier (spurious vector) is a common problem in practical velocity field measurement using particle image velocimetry technology (PIV), and it should be validated and replaced by a reliable value. One of the most challenging problems is to correctly label the outliers under the circumstance that measurement noise exists or the flow becomes turbulent. Moreover, the outlier's cluster occurrence makes it difficult to pick out all the outliers. Most of current methods validate and correct the outliers using local statistical models in a single pass. In this work, a vector field correction (VFC) method is proposed directly from a mixture statistical model of PIV signal. Actually, this problem is formulated as a maximum a posteriori (MAP) estimation of a Bayesian model with hidden/latent variables, labeling the outliers in the original field. The solution of this MAP estimation, i.e., the outlier set and the restored flow field, is optimized iteratively using an expectation-maximization algorithm. We illustrated this VFC method on two kinds of synthetic velocity fields and two kinds of experimental data and demonstrated that it is robust to a very large number of outliers (even up to 60 %). Besides, the proposed VFC method has high accuracy and excellent compatibility for clustered outliers, compared with the state-of-the-art methods. Our VFC algorithm is computationally efficient, and corresponding Matlab code is provided for others to use it. In addition, our approach is general and can be seamlessly extended to three-dimensional-three-component (3D3C) PIV data.

  13. A topological evaluation procedure to assess the integrity of a PIV vector field

    Foss, J. F.; Hedden, M.; Barros, J. M.; Christensen, K. T.


    Particle image velocimetry (PIV) provides a field of discrete vectors to represent a continuum velocity field. Various methods have been adopted to evaluate the integrity of the discrete vectors. In contrast, the present communication provides a systematic technique whereby the integrity of the measured field can be assessed using basic topological principles. Starting with the recognition that PIV provides a vector field overlaid on a planar surface, the analyst can identify the holes (to be punched through the surface of a sphere) and the handles (to be added to the sphere’s surface) that will represent the appropriate surface for the topological analysis. These operations define the a priori Euler characteristic (χ A ) for the subject PIV image. The experimental Euler characteristic (χ E ) will be known from the properties of the measured vector field: nodes, saddles, etc. A necessary condition for the integrity of the measured vector field is that χ E   =  χ A . The topological bases for the integrity evaluation, including the important constraint of ensuring a smooth collapsed sphere, are carefully explained and described with examples.

  14. Uncertainty Estimation for 2D PIV: An In-Depth Comparative Analysis

    Boomsma, Aaron; Bhattacharya, Syantan; Troolin, Dan; Vlachos, Pavlos; Pothos, Stamatios


    Uncertainty quantification methods have recently made great strides in accurately predicting uncertainties for planar PIV, and several different approaches are now documented. In the present study, we provide an analysis of these methods across different experiments and different PIV processing codes. To assess the performance of said methods, we follow the approach of Sciacchitano et al. (2015) and utilize two PIV measurement systems with overlapping fields of view-one acting as a reference (which is validated using simultaneous LDV measurements) and the other as a measurement system, paying close attention to the effects of interrogation window overlap and bias errors on the analysis. A total of three experiments were performed: a jet flow and a cylinder in cross flow at two Reynolds numbers. In brief, the standard coverages (68% confidence interval) ranged from approximately 65%-77% for PPR and MI methods, 40%-50% for image matching methods. We present an in-depth survey of both global (e.g., coverage and error histograms) and local (e.g., spatially varying statistics) parameters to examine the strengths and weaknesses of each method in monitor their responses to different regions of the experimental flows.

  15. Velocity field investigation inside a bulb turbine runner using endoscopic PIV measurements

    Lemay, S.; Aeschlimann, V.; Fraser, R.; Ciocan, G. D.; Deschênes, C.


    The flow in the inter-blade channels of a bulb turbine was measured using endoscopic cameras integrated to a stereoscopic particle image velocimetry (S-PIV) system. This paper presents results from the measurement campaign and also provides some key conclusions based on the dataset. The technical aspect of the measurement configuration is addressed. The main focus is on the novelties and challenges brought by the use of endoscopic cameras to achieve S-PIV measurements between the runner blades. For the first time in hydraulic rotating machinery, velocity measurements covered 62 % of a rotor inter-blade flow. After outlining the techniques used, comparison with laser Doppler velocimetry measurements allows assessing the intrusiveness of the endoscopes. Then, some velocity field analyses are shown. First, the rotor-stator interaction is outlined as the influence of the guide vane wakes on the runner flow. The size, localization, strength and dissipation of those structures are inferred from the information coming from measurements. Finally, the PIV data allow the identification of a vortex located near the suction side of the blades and originating from the corner between the leading edge and the hub when operating the bulb turbine at part-load.

  16. Fiber tracking algorithm in combined PIV/PTV measurement of fiber suspension flow

    Hoseini, Afshin Abbasi; Zavareh, Zahra; Lundell, Fredrik; Anderson, Helge I.


    A new algorithm for fiber tracking in combined PIV/PTV measurement of fiber suspension flow is proposed based on SOM neural network and is examined by synthetic images of fibers showing 2D suspension flows. There is a new idea in the algorithm to take the orientation of fibers into account for matching as well as their position. In two-phase PIV measurements of fiber-laded suspension flows, fiber tracking has a key role together with PIV measurement of fluid phase. The essential parts of fiber tracking are to correctly identify and match fibers in successive images. The development of a method in order to determine the position and orientation of fibers using steerable filter with a reasonable accuracy have already been done, [3]. The present study is concentrated in the development of an algorithm for pairing fibers in consecutive images. The method used is based on the SOM neural network that finds most likely matching link in images on the basis of feature extraction and clustering. The fundamental concept is finding the corresponding fibers with the nearest characteristics, position and angle in images. It improves not only the robustness against loss-of-pair fibers between two image frames but also reliable matching at large numbers of dispersed fibers image using one more characteristics of fibers in image, namely their orientation, in addition to their coordinate vector.

  17. 3D analysis of vortical structures in an abdominal aortic aneurysm by stereoscopic PIV

    Deplano, Valérie; Guivier-Curien, Carine; Bertrand, Eric


    The present work presents an experimental in vitro three-dimensional analysis of the flow dynamics in an abdominal aortic aneurysm (AAA) through stereoscopic particle image velocimetry (SPIV) measurements. The experimental set-up mimics the pathophysiological context involving a shear thinning blood analogue fluid, compliant AAA and aorto-iliac bifurcation walls and controlled inlet and outlet flow rate and pressure waveforms as well as working fluid temperature. SPIV was carefully calibrated and conducted to assess the three velocity components in the AAA volume. For the first time in the literature, the 3D vortex ring genesis, propagation, and vanishing in the AAA bulge are experimentally described and quantified. In comparison with classical 2-component PIV measurements (2C PIV), the third component of the velocity vector was shown to be of importance in such a geometry, especially, during the deceleration phase of the flow rate. The 3D velocity magnitude reached up more than 20 % of the 2D one showing that 2C PIV are definitively not accurate enough to provide a complete description of flow behaviour in an AAA. In addition to potential clinical implications of a full 3D vortex ring description in AAA evolution, the 3D in vitro experimental quantification of the flow dynamics carried out in the present study offers an interesting tool for the validation of fluid-structure interaction numerical studies dealing with AAA.

  18. A Comparison of Flow Field Characteristics from PIV Experiment Measurement to Numerical Simulation behind a Spacer in a Vertical Pipe

    Lávička D.


    Full Text Available This paper describes the topic of measurement using a modern laser method (PIV in an annular channel of very small dimensions. The annular channel simulates the flow area around a model of a fuel rod in the VVER nuclear reactor. The annular channel holds spacers which create obstacles to fluid flow. The spacers serve a number of important purposes. In the real nuclear reactor, the spacer holds a fuel rod in the fuel rod bundle. Another important function of the spacer is to influence the flow field characteristics, especially turbulence size, by the shape of the spacer. The value of the turbulence regulates the intensity of heat transfer between the fuel rod and the fluid. Therefore, it is very important to provide a correct description and analysis of the flow field behind the obstacle the spacer generates. The paper further looks into the solution of the same task using numerical simulation. The solution of this task consisted of setting the suitable boundary conditions and of setting the turbulence model for the numerical simulation. The result is a comparison of the flow field characteristics from the experimental measurement and the findings of the numerical simulation. The numerical simulation was carried out using commercial CFD software package, FLUENT.

  19. PIV Measurements of Atmospheric Turbulence and Pollen Dispersal Above a Corn Canopy

    Zhu, W.; van Hout, R.; Luznik, L.; Katz, J.


    Dispersal of pollen grains by wind and gravity (Anemophilous) is one of the oldest means of plant fertilization available in nature. Recently, the growth of genetically modified foods has raised questions on the range of pollen dispersal in order to limit cross-fertilization between organically grown and transgenic crops. The distance that a pollen grain can travel once released from the anther is determined, among others, by the aerodynamic parameters of the pollen and the characteristics of turbulence in the atmosphere in which it is released. Turbulence characteristics of the flow above a pollinating corn field were measured using Particle Image Velocimetry (PIV). The measurements were performed on the eastern shore of the Chesapeake Bay, in Maryland, during July 2003. Two PIV systems were used simultaneously, each with an overall sample area of 18x18 cm. The spacing between samples was about equal to the field of view. The PIV instrumentation, including CCD cameras, power supply and laser sheets forming optics were mounted on a measurement platform, consisting of a hydraulic telescopic arm that could be extended up to 10m. The whole system could be rotated in order to align it with the flow. The flow was seeded with smoke generated about 30m upstream of the sample areas. Measurements were carried out at several elevations, from just below canopy height up to 1m above canopy. The local meteorological conditions around the test site were monitored by other sensors including sonic anemometers, Rotorod pollen counters and temperature sensors. Each processed PIV image provides an instantaneous velocity distribution containing 64x64 vectors with a vector spacing of ~3mm. The pollen grains (~100mm) can be clearly distinguished from the smoke particles (~1mm) based on their size difference. The acquired PIV data enables calculation of the mean flow and turbulence characteristics including Reynolds stresses, spectra, turbulent kinetic energy and dissipation rate. Data

  20. Piv site-specific invertase requires a DEDD motif analogous to the catalytic center of the RuvC Holliday junction resolvases.

    Buchner, John M; Robertson, Anne E; Poynter, David J; Denniston, Shelby S; Karls, Anna C


    Piv, a unique prokaryotic site-specific DNA invertase, is related to transposases of the insertion elements from the IS110/IS492 family and shows no similarity to the site-specific recombinases of the tyrosine- or serine-recombinase families. Piv tertiary structure is predicted to include the RNase H-like fold that typically encompasses the catalytic site of the recombinases or nucleases of the retroviral integrase superfamily, including transposases and RuvC-like Holliday junction resolvases. Analogous to the DDE and DEDD catalytic motifs of transposases and RuvC, respectively, four Piv acidic residues D9, E59, D101, and D104 appear to be positioned appropriately within the RNase H fold to coordinate two divalent metal cations. This suggests mechanistic similarity between site-specific inversion mediated by Piv and transposition or endonucleolytic reactions catalyzed by enzymes of the retroviral integrase superfamily. The role of the DEDD motif in Piv catalytic activity was addressed using Piv variants that are substituted individually or multiply at these acidic residues and assaying for in vivo inversion, intermolecular recombination, and DNA binding activities. The results indicate that all four residues of the DEDD motif are required for Piv catalytic activity. The DEDD residues are not essential for inv recombination site recognition and binding, but this acidic tetrad does appear to contribute to the stability of Piv-inv interactions. On the basis of these results, a working model for Piv-mediated inversion that includes resolution of a Holliday junction is presented.

  1. [Effect of extracted ZG from gardenia on Hep-2 cell membrane post infected with parainfluenza virus type 1 (PIV-1)].

    Guo, Shan-Shan; Huang, Yang; Zhao, Ye; Gao, Ying-Jie; Gong, Wen-Feng; Cui, Xiao-Lan


    In order to study the anti-viral mechanism of extracted ZG from Gardenia, the effect of extracted ZG on Hep-2 cell membrane potential, Na -K+-ATPase activity and membrane fluidity post infected with parainfluenza virus type 1 (PIV-1) was observed. Acetylcholine which was fluorescent labeled with DiBAC4 (3) was taken as positive control to observe the changes of membrane potential and was measured by flow cytometer. The phosphorus determination method and spectrophotometer were used to measure the Na+-K+-ATPase activity of Hep-2 cell membrane post PIV-1 infection. Hep-2 cell membrane phospholipids was labeled with fluorescent NBD-C6-HPC and membrane fluidity was measured by confocal laser scanning microscope. The results demonstated that after PIV-1 infection the Hep-2 cell membrane potential decreased significantly and the membrane was in the state of hyperpolarization, Na+-K+-ATPase activity increased and membrane fluidity decreased significantly. There was no apparent interferring effect of extracted ZG on the changes of membrane potential and Na+-K+-ATPase activity post PIV-1 infection, while membrane fluidity was improved significantly. Acetylcholine improved the state of hyperpolarization. The changes of membrane potential, Na -K+-ATPase activity and membrane fluidity might be the biomechanism of PIV-1 infectoin. The extracted ZG improved membrane fluidity to prevent from PIV-1 infection by protecting the cell membrane, which was probably the mechanism of anti-PIV-1 activity of the extracted ZG, but ZG probably had nothing to do with membrane potential and Na+-K+-ATPase activity.

  2. PIV Experimental Research in Compressor Cascade Flow Field%压气机平面叶栅内流场 PIV 试验研究

    薄相峰; 刘波


    Using PIV technique,the flow field of compressor cascade was measured,the related technology of measuring high speed flow field was investigated.In the experiment,PIV is used in compressor cascade flow field measurement.Through the ex-periment,results were acquired that include flow velocity structure images of the tested cascade passage at 50%span,at the high-er inlet Mach number.Preliminary analysis into the experimental data shows that the experimental results agree with predicted flow characteristics under tested flow conditions.Improved the experiment method, results were acquired that compressor cascade boundary layer characteristic.The results indicate that the PIV measurment can provide credible data for numerical research and supervise the optimize design of compressor cascade.%应用PIV内流测试技术对某高亚音速叶栅速度场进行了测量,得到了叶栅内流通道的流场结构。试验得到了多种来流工况下试验叶栅槽道50%叶高处的速度流场结构图像,对试验数据的初步分析可以看出试验结果符合所测工况下的流动规律。通过对实验方案的改进,应用PIV测试技术测量了平面叶栅附面层流场,捕捉到了叶片吸力面尾缘附面层分离随来流工况变化,。结果表明:PIV测量结果可以为验证数值模拟叶栅通道流场提供可靠的数据,并为叶栅设计的改进优化提供指导和依据。

  3. MacCormack's technique-based pressure reconstruction approach for PIV data in compressible flows with shocks

    Liu, Shun; Xu, Jinglei; Yu, Kaikai


    This paper proposes an improved approach for extraction of pressure fields from velocity data, such as obtained by particle image velocimetry (PIV), especially for steady compressible flows with strong shocks. The principle of this approach is derived from Navier-Stokes equations, assuming adiabatic condition and neglecting viscosity of flow field boundaries measured by PIV. The computing method is based on MacCormack's technique in computational fluid dynamics. Thus, this approach is called the MacCormack method. Moreover, the MacCormack method is compared with several approaches proposed in previous literature, including the isentropic method, the spatial integration and the Poisson method. The effects of velocity error level and PIV spatial resolution on these approaches are also quantified by using artificial velocity data containing shock waves. The results demonstrate that the MacCormack method has higher reconstruction accuracy than other approaches, and its advantages become more remarkable with shock strengthening. Furthermore, the performance of the MacCormack method is also validated by using synthetic PIV images with an oblique shock wave, confirming the feasibility and advantage of this approach in real PIV experiments. This work is highly significant for the studies on aerospace engineering, especially the outer flow fields of supersonic aircraft and the internal flow fields of ramjets.

  4. A particle-tracking approach for accurate material derivative measurements with tomographic PIV

    Novara, Matteo; Scarano, Fulvio


    The evaluation of the instantaneous 3D pressure field from tomographic PIV data relies on the accurate estimate of the fluid velocity material derivative, i.e., the velocity time rate of change following a given fluid element. To date, techniques that reconstruct the fluid parcel trajectory from a time sequence of 3D velocity fields obtained with Tomo-PIV have already been introduced. However, an accurate evaluation of the fluid element acceleration requires trajectory reconstruction over a relatively long observation time, which reduces random errors. On the other hand, simple integration and finite difference techniques suffer from increasing truncation errors when complex trajectories need to be reconstructed over a long time interval. In principle, particle-tracking velocimetry techniques (3D-PTV) enable the accurate reconstruction of single particle trajectories over a long observation time. Nevertheless, PTV can be reliably performed only at limited particle image number density due to errors caused by overlapping particles. The particle image density can be substantially increased by use of tomographic PIV. In the present study, a technique to combine the higher information density of tomographic PIV and the accurate trajectory reconstruction of PTV is proposed (Tomo-3D-PTV). The particle-tracking algorithm is applied to the tracers detected in the 3D domain obtained by tomographic reconstruction. The 3D particle information is highly sparse and intersection of trajectories is virtually impossible. As a result, ambiguities in the particle path identification over subsequent recordings are easily avoided. Polynomial fitting functions are introduced that describe the particle position in time with sequences based on several recordings, leading to the reduction in truncation errors for complex trajectories. Moreover, the polynomial regression approach provides a reduction in the random errors due to the particle position measurement. Finally, the acceleration

  5. PIV study on a shock-induced separation in a transonic flow

    Sartor, Fulvio; Losfeld, Gilles; Bur, Reynald [ONERA, Meudon (France)


    A transonic interaction between a steady shock wave and a turbulent boundary layer in a Mach 1.4 channel flow is experimentally investigated by means of particle image velocimetry (PIV). In the test section, the lower wall is equipped with a contour profile shaped as a bump allowing flow separation. The transonic interaction, characterized by the existence in the outer flow of a lambda shock pattern, causes the separation of the boundary layer, and a low-speed recirculating bubble is observed downstream of the shock foot. Two-component PIV velocity measurements have been performed using an iterative gradient-based cross-correlation algorithm, providing high-speed and flexible calculations, instead of the classic multi-pass processing with FFT-based cross-correlation. The experiments are performed discussing all the hypotheses linked to the experimental set-up and the technique of investigation such as the two-dimensionality assumption of the flow, the particle response assessment, the seeding system, and the PIV correlation uncertainty. Mean velocity fields are presented for the whole interaction with particular attention for the recirculating bubble downstream of the detachment, especially in the mixing layer zone where the effects of the shear stress are most relevant. Turbulence is discussed in details, the results are compared to previous study, and new results are given for the turbulent production term and the return to isotropy mechanism. Finally, using different camera lens, a zoom in the vicinity of the wall presents mean and turbulent velocity fields for the incoming boundary layer. (orig.)

  6. Velocity Fields of Axisymmetric Hydrogen-Air Counterflow Diffusion Flames from LDV, PIV, and Numerical Computation

    Pellett, Gerald L.; Wilson, Lloyd G.; Humphreys, William M., Jr.; Bartram, Scott M.; Gartrell, Luther R.; Isaac, K. M.


    Laminar fuel-air counterflow diffusion flames (CFDFs) were studied using axisymmetric convergent-nozzle and straight-tube opposed jet burners (OJBs). The subject diagnostics were used to probe a systematic set of H2/N2-air CFDFs over wide ranges of fuel input (22 to 100% Ha), and input axial strain rate (130 to 1700 Us) just upstream of the airside edge, for both plug-flow and parabolic input velocity profiles. Laser Doppler Velocimetry (LDV) was applied along the centerline of seeded air flows from a convergent nozzle OJB (7.2 mm i.d.), and Particle Imaging Velocimetry (PIV) was applied on the entire airside of both nozzle and tube OJBs (7 and 5 mm i.d.) to characterize global velocity structure. Data are compared to numerical results from a one-dimensional (1-D) CFDF code based on a stream function solution for a potential flow input boundary condition. Axial strain rate inputs at the airside edge of nozzle-OJB flows, using LDV and PIV, were consistent with 1-D impingement theory, and supported earlier diagnostic studies. The LDV results also characterized a heat-release hump. Radial strain rates in the flame substantially exceeded 1-D numerical predictions. Whereas the 1-D model closely predicted the max I min axial velocity ratio in the hot layer, it overpredicted its thickness. The results also support previously measured effects of plug-flow and parabolic input strain rates on CFDF extinction limits. Finally, the submillimeter-scale LDV and PIV diagnostics were tested under severe conditions, which reinforced their use with subcentimeter OJB tools to assess effects of aerodynamic strain, and fueVair composition, on laminar CFDF properties, including extinction.

  7. Finite Element Numerical Simulation and PIV Measurement of Flow Field inside Metering-in Spool Valve

    GAO Dianrong; QIAO Haijun; LU Xianghui


    The finite element method (FEM) and particle image velocimetry (PIV) technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at three different valve openings. For FEM numerical simulation, the stream function ψ -vorticity ω forms of continuity and Navier-Stokes equations are employed and FEM is applied to discrete the equations. Homemade simulation codes are executed to compute the values of stream function and vorticity at each node in the flow domain, then according to the correlation between stream function and velocity components, the velocity vectors of the whole field are calculated. For PIV experiment, pulse Nd: YAG laser is exploited to generate laser beam, cylindrical and spherical lenses are combined each other to produce 1.0 mm thickness laser sheet to illuminate the object plane, Polystyrene spherical particle with diameter of 30-50 μm is seeded in the fluid as a tracing particles, Kodak ES1.0 CCD camera is employed to capture the images of interested, the images are processed with fast Fourier transform (FFT) cross-correlation algorithm and the processing results is displayed. Both results of numerical simulation and PIV experimental show that there are three main areas in the spool valve where vortex is formed.Numerical results also indicate that the valve opening have some effects on the flow structure of the valve. The investigation is helpful for qualitatively analyzing the energy loss, noise generating, steady state flow forces and even designing the geometry structure and flow passage.

  8. Gas- liquid experimentation in a rectangular bubble column using PIV and Shadow techniques

    Diana Isabel Sánchez Forero


    Resumo: Colunas de bolhas são dispositivos de contato multifásico para transferência de massa e calor, intensamente utilizados em diferentes áreas industriais. O escoamento e a turbulência destes equipamentos são induzidos pelo movimento ascendente das bolhas. A hidrodinâmica e o comportamento das bolhas em regime homogêneo foram analisados em uma coluna de bolhas retangular em escala de laboratório (50 cm x 20 cm x 220 cm), utilizando as técnicas de velocimetria por imagem de partícula (PIV)...

  9. Detecting coherent patterns in a flume by using PIV and IR imaging techniques

    Gurka, Roi [Multiphase Flow Laboratory, Mechanical Engineering Department, Technion-IIT, 32000, Haifa (Israel); Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD (United States); Liberzon, Alex [Multiphase Flow Laboratory, Mechanical Engineering Department, Technion-IIT, 32000, Haifa (Israel); Institute of Hydromechanics and Water Resources Management, ETH Zuerich (Switzerland); Hetsroni, Gad [Multiphase Flow Laboratory, Mechanical Engineering Department, Technion-IIT, 32000, Haifa (Israel)


    We investigated the flow field in a turbulent boundary layer in a flume, by using Particle Image Velocimetry (PIV) and Hot-Foil Infrared Imaging (HFIRI) techniques. Coherent patterns in the flow were identified and characterized by using instantaneous velocity and temperature fields. The velocity fields in the streamwise-spanwise plane were measured in parallel to the temperature distribution of the flume bottom. The identified patterns are represented by means of their spatial characteristics - a non-dimensional spatial separation between streamwise patterns, {lambda}{sup +}. (orig.)

  10. PIV Experimental Investigation on the Flow in a Model of Closed Pump Sump

    MANSA Kante; ZHANG Botao(张波涛); LI Xiaoming(李小明); LI Yong(李永); WU Yulin(吴玉林)


    Vortices in the flow of a pump sump present an important problem in pump station operation. In the present study, the flow patterns in two model pump sumps with specially designed structures are analyzed using the particle image velocimetry (PIV) technique. The data is analyzed to reveal a number of parameters including the internal flow field with velocity distribution, the streamline distribution, and the turbulent kinetic energy. The analysis certifies that a modified pump with added T-type baffle below the sump exhibits good performance for realistic working conditions.

  11. The Application of EIS and PIV Methods to the Measurement of Aerated Flow

    Fejfarová M.


    Full Text Available The paper describes measurements in the aerated water medium using modern methods PIV (Particle Image Velocimetry and EIS (Electrical Impedance Spectrometry, which are applied in the Laboratory of Water Management Research (LVV of the Department of Water Structures (UVST at the Faculty of Civil Engineering (FAST of Brno University of Technology (VUT. Measurements of the water medium were carried out for three different aeration intensities at special experimental workplaces. The experiment was focused on the capability of the methods to monitor the air content in the water.

  12. PIV measurements in a microfluidic 3D-sheathing structure with three-dimensional flow behaviour

    Klank, Henning; Goranovic, Goran; Kutter, Jörg Peter


    The design and production time for complex microfluidic systems is considerable, often up to several months. It is therefore important to be able to understand and predict the flow phenomena prior to design and fabrication of the microdevice in order to save costly fabrication resources. The stru......, a stereoscopic principle was applied to obtain all three velocity components, showing the feasibility of obtaining full volume mapping (x, y, z, U, V, W) from micro-PIV measurements. The results are compared with computational fluid dynamics (CFD) simulations....

  13. Determination of complete velocity gradient tensor by using cinematographic stereoscopic PIV in a turbulent jet

    Ganapathisubramani, B. [The University of Texas at Austin, Center for Aeromechanics Research, Austin, TX (United States); Imperial College London, Department of Aeronautics, London (United Kingdom); Lakshminarasimhan, K. [The University of Texas at Austin, Center for Aeromechanics Research, Austin, TX (United States); Sandia National Laboratories, Combustion Research Facility, Livermore, CA (United States); Clemens, N.T. [The University of Texas at Austin, Center for Aeromechanics Research, Austin, TX (United States)


    Cinematographic stereoscopic PIV measurements were performed in the far field of an axisymmetric co-flowing turbulent round jet (Re{sub T}{approx}150, where Re{sub T} is the Reynolds number based on Taylor micro scale) to resolve small and intermediate scales of turbulence. The time-resolved three-component PIV measurements were performed in a plane normal to the axis of the jet and the data were converted to quasi-instantaneous three-dimensional (volumetric) data by using Taylor's hypothesis. The availability of the quasi-three-dimensional data enabled the computation of all nine components of the velocity gradient tensor over a volume. The use of Taylor's hypothesis was validated by performing a separate set of time-resolved two component ''side-view'' PIV measurements in a plane along the jet axis. Probability density distributions of the velocity gradients computed using Taylor's hypothesis show good agreement with those computed directly with the spatially resolved data. The overall spatial structure of the gradients computed directly exhibits excellent similarity with that computed using Taylor's hypothesis. The accuracy of the velocity gradients computed from the pseudo-volume was assessed by computing the divergence error in the flow field. The root mean square (rms) of the divergence error relative to the magnitude of the velocity gradient tensor was found to be 0.25, which is consistent with results based on other gradient measurement techniques. The velocity gradients, vorticity components and mean dissipation in the self-similar far field of the jet were found to satisfy the axisymmetric isotropy conditions. The divergence error present in the data is attributed to the intrinsic uncertainty associated with performing stereoscopic PIV measurements and not to the use of Taylor's hypothesis. The divergence error in the data is found to affect areas of low gradient values and manifests as nonphysical values for

  14. Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations.

    Hagsäter, S M; Jensen, T Glasdam; Bruus, H; Kutter, J P


    We show that full-image micro-PIV analysis in combination with images of transient particle motion is a powerful tool for experimental studies of acoustic radiation forces and acoustic streaming in microfluidic chambers under piezo-actuation in the MHz range. The measured steady-state motion of both large 5 microm and small 1 microm particles can be understood in terms of the acoustic eigenmodes or standing ultra-sound waves in the given experimental microsystems. This interpretation is supported by numerical solutions of the corresponding acoustic wave equation.

  15. PIV的原理与应用%Theory and Application of PIV




  16. PIV Measurements in the 14 x 22 Low Speed Tunnel: Recommendations for Future Testing

    Watson, Ralph D.; Jenkins, Luther N.; Yao, Chung-Sheng; McGinley, Catherine B.; Paschal, Keith B.; Neuhart, Dan H.


    During the period from February 4 to March 21, 2003 stereo digital particle imaging velocimetry measurements were made on a generic high lift model, the Trap Wing, as part of the High Lift Flow Physics Experiment. These measurements were the first PIV measurements made in the NASA, Langley Research Center 14 x 22 Foot Low Speed Tunnel, and several problems were encountered and solved in the acquisition of the data. It is the purpose of this paper to document the solutions to these problems and to make recommendations for further improvements to the tunnel/setup in order to facilitate future measurements of this type.

  17. Study of aerodynamic structure of flow in a model of vortex furnace using Stereo PIV method

    Anufriev, I. S.; Kuibin, P. A.; Shadrin, E. Yu.; Sharaborin, D. K.; Sharypov, O. V.


    The aerodynamic structure of flow in a lab model of a perspective design of vortex furnace was studied. The chamber has a horizontal rotation axis, tangential inlet for fuel-air jets and vertical orientation of secondary injection nozzles. The Stereo PIV method was used for visualization of 3D velocity field for selected cross sections of the vortex combustion chamber. The experimental data along with "total pressure minimum" criterion were used for reconstruction of the vortex core of the flow. Results fit the available data from LDA and simulation.

  18. F2DPR: a fast and robust cross-correlation technique for volumetric PIV

    Earl, Thomas; Jeon, Young Jin; Lecordier, Bertrand; David, Laurent


    The current state-of-the-art in cross-correlation based time-resolved particle image velocimetry (PIV) techniques are the fluid trajectory correlation, FTC (Lynch and Scarano 2013) and the fluid trajectory evaluation based on an ensemble-averaged cross-correlation, FTEE (Jeon et al 2014a). These techniques compute the velocity vector as a polynomial trajectory Γ in space and time, enabling the extraction of beneficial quantities such as material acceleration whilst significantly increasing the accuracy of the particle displacement prediction achieved by standard two-frame PIV. In the context of time-resolved volumetric PIV, the drawback of trajectory computation is the computational expense of the three-dimensional (3D) cross-correlation, exacerbated by the requirement to perform N  -  1 cross-correlations, where N (for typically 5≤slant N≤slant 9 ) is the number of sequential particle volumes, for each velocity field. Therefore, the acceleration of this calculation is highly desirable. This paper re-examines the application of two-dimensional (2D) cross-correlation methods to three-dimensional (3D) datasets by Bilsky et al (2011) and the binning techniques of Discetti and Astarita (2012). A new and robust version of the 2D methods is proposed and described, called fast 2D projection—re-projection (f2dpr). Performance tests based on computational time and accuracy for both two-frame and multi-frame PIV are carried out on synthetically generated data. The cases presented herein include uniaxial uniform linear displacements and shear, and simulated turbulence data. The proposed algorithm is shown to be in the order of 10 times faster than a standard 3D FFT without loss of precision for a wide range of synthetic test cases, while combining with the binning technique can yield 50 times faster computation. The algorithm is also applied to reconstructed synthetic turbulent particle fields to investigate reconstruction noise on its performance and no

  19. Time-resolved scanning tomography PIV measurements around a flapping wing

    David, L.; Jardin, T.; Braud, P.; Farcy, A. [Institut Prime, CNRS-Universite de Poitiers-ENSMA, UPR3346, Departement Fluides, Thermiques, Combustion, SP2MI, Futuroscope, Chasseneuil (France)


    The three-dimensional flow that develops around a finite flapping wing is investigated using a tomographic scanning PIV technique. The acquisition and correlation processes employed to achieve such measurements have been carefully validated. Issues regarding the relevant timescales of the flow and the spanwise space-resolution are addressed. Results obtained on a hovering flapping wing whose plunging phase is described by a rectilinear motion highlight the influence of the free end condition and the formation of the tip vortex on the leading edge vortices behavior, wing/wake interactions, and wake stabilization. (orig.)

  20. Temperature and velocity fields in natural convection by PIV and LIF

    Meyer, Knud Erik; Larsen, Poul Scheel; Westergaard, C. H.


    Natural convection in a cubical cavity (L = 250 mm) filled with water is created by heating a square plate (0.5 L) centred in the bottom wall and by cooling the sidewalls, while the remaining walls are insulated. The Rayleigh number based on cavity side length and temperature difference between...... plate and cooled walls is 1.4×10^10. The flow is turbulent and is similar to some indoor room flows. Combined Particle Image Velocimetry (PIV) and Planar Light Induced Fluorescence (LIF) are used to measure local velocities and temperatures. Data measured in a symmetry plane parallel to a sidewall...

  1. Decomposition Methods For a Piv Data Analysis with Application to a Boundary Layer Separation Dynamics

    Václav URUBA


    Full Text Available Separation of the turbulent boundary layer (BL on a flat plate under adverse pressure gradient was studied experimentally using Time-Resolved PIV technique. The results of spatio-temporal analysis of flow-field in the separation zone are presented. For this purpose, the POD (Proper Orthogonal Decomposition and its extension BOD (Bi-Orthogonal Decomposition techniques are applied as well as dynamical approach based on POPs (Principal Oscillation Patterns method. The study contributes to understanding physical mechanisms of a boundary layer separation process. The acquired information could be used to improve strategies of a boundary layer separation control.

  2. Using PIV to determine relative pressures in a stenotic phantom under steady flow based on the pressure-poisson equation.

    Khodarahmi, Iman; Shakeri, Mostafa; Sharp, M; Amini, Amir A


    Pressure gradient across a Gaussian-shaped 87% area stenosis phantom was estimated by solving the pressure Poisson equation (PPE) for a steady flow mimicking the blood flow through the human iliac artery. The velocity field needed to solve the pressure equation was obtained using particle image velocimetry (PIV). A steady flow rate of 46.9 ml/s was used, which corresponds to a Reynolds number of 188 and 595 at the inlet and stenosis throat, respectively (in the range of mean Reynolds number encountered in-vivo). In addition, computational fluid dynamics (CFD) simulation of the same flow was performed. Pressure drops across the stenosis predicted by PPE/PIV and CFD were compared with those measured by a pressure catheter transducer. RMS errors relative to the measurements were 17% and 10% for PPE/PIV and CFD, respectively.

  3. A Monte Carlo study comparing PIV, ULS and DWLS in the estimation of dichotomous confirmatory factor analysis.

    Nestler, Steffen


    We conducted a Monte Carlo study to investigate the performance of the polychoric instrumental variable estimator (PIV) in comparison to unweighted least squares (ULS) and diagonally weighted least squares (DWLS) in the estimation of a confirmatory factor analysis model with dichotomous indicators. The simulation involved 144 conditions (1,000 replications per condition) that were defined by a combination of (a) two types of latent factor models, (b) four sample sizes (100, 250, 500, 1,000), (c) three factor loadings (low, moderate, strong), (d) three levels of non-normality (normal, moderately, and extremely non-normal), and (e) whether the factor model was correctly specified or misspecified. The results showed that when the model was correctly specified, PIV produced estimates that were as accurate as ULS and DWLS. Furthermore, the simulation showed that PIV was more robust to structural misspecifications than ULS and DWLS.

  4. Visualizing the transient electroosmotic flow and measuring the zeta potential of microchannels with a micro-PIV technique.

    Yan, Deguang; Nguyen, Nam-Trung; Yang, Chun; Huang, Xiaoyang


    We have demonstrated a transient micro particle image velocimetry (micro-PIV) technique to measure the temporal development of electroosmotic flow in microchannels. Synchronization of different trigger signals for the laser, the CCD camera, and the high-voltage switch makes this measurement possible with a conventional micro-PIV setup. Using the transient micro-PIV technique, we have further proposed a method on the basis of inertial decoupling between the particle electrophoretic motion and the fluid electroosmotic flow to determine the electrophoretic component in the particle velocity and the zeta potential of the channel wall. It is shown that using the measured zeta potentials, the theoretical predictions agree well with the transient response of the electroosmotic velocities measured in this work.

  5. A new approach for volume reconstruction in TomoPIV with the alternating direction method of multipliers

    Barbu, Ioana; Herzet, Cédric


    We adapt and import into the TomoPIV scenery a fast algorithm for solving the volume reconstruction problem. Our approach is based on the reformulation of the volume reconstruction task as a constrained optimization problem and the resort to the ‘alternating directions method of multipliers’ (ADMM). The inherent primal-dual algorithm is summarized in this article to solve the optimization problem related to the TomoPIV. In particular, the general formulation of the volume reconstruction problem considered in this paper allows one to: (i) take explicitly into account the level of the noise affecting the data; (ii) account for both the nonnegativity and the sparsity of the solution. Experiments on a numerical TomoPIV benchmark show that the proposed framework is a serious contender for the state-of-the-art.

  6. Stereoscopic PIV on multiple color-coded light sheets and its application to axial flow in flapping robotic insect wings

    Pick, Simon; Lehmann, Fritz-Olaf


    Non-scanning volume flow measurement techniques such as 3D-PTV, holographic and tomographic particle image velocimetry (PIV) permit reconstructions of all three components (3C) of velocity and vorticity vectors in a fluid volume (3D). In this study, we present a novel 3D3C technique termed Multiple-Color-Plane Stereo Particle-Image-Velocimetry (color PIV), which allows instantaneous measurements of 3C velocity vectors in six parallel, colored light sheets. We generated the light sheets by passing white light of two strobes through dichroic color filters and imaged the slices by two 3CCD color cameras in Stereo-PIV configuration. The stereo-color images were processed by custom software routines that sorted each colored fluid particle into one of six gray-scale images according to its hue, saturation, and luminance. We used conventional Stereo PIV cross-correlation algorithms to compute a 3D planar vector field for each light sheet and subsequently interpolated a volume flow map from the six vector fields. As a first application, we quantified the wake and axial flow in the vortical structures of a robotic insect (fruit fly) model wing. In contrast to previous findings, the measured data indicate strong axial flow components on the upper wing surface, including axial flow in the leading-edge vortex core. Collectively, color PIV is robust against mechanical misalignments, avoids laser safety issues, and computes instantaneous 3D vector fields in a fraction of the time typical for other 3D systems. Color PIV might thus be of value for volume measurements of highly unsteady flows.

  7. Activation of ERα signaling differentially modulates IFN-γ induced HLA-class II expression in breast cancer cells.

    Ahmed A Mostafa

    Full Text Available The coordinate regulation of HLA class II (HLA-II is controlled by the class II transactivator, CIITA, and is crucial for the development of anti-tumor immunity. HLA-II in breast carcinoma is associated with increased IFN-γ levels, reduced expression of the estrogen receptor (ER and reduced age at diagnosis. Here, we tested the hypothesis that estradiol (E₂ and ERα signaling contribute to the regulation of IFN-γ inducible HLA-II in breast cancer cells. Using a panel of established ER⁻ and ER⁺ breast cancer cell lines, we showed that E₂ attenuated HLA-DR in two ER⁺ lines (MCF-7 and BT-474, but not in T47D, while it augmented expression in ER⁻ lines, SK-BR-3 and MDA-MB-231. To further study the mechanism(s, we used paired transfectants: ERα⁺ MC2 (MDA-MB-231 c10A transfected with the wild type ERα gene and ERα⁻ VC5 (MDA-MB-231 c10A transfected with the empty vector, treated or not with E₂ and IFN-γ. HLA-II and CIITA were severely reduced in MC2 compared to VC5 and were further exacerbated by E₂ treatment. Reduced expression occurred at the level of the IFN-γ inducible CIITA promoter IV. The anti-estrogen ICI 182,780 and gene silencing with ESR1 siRNA reversed the E2 inhibitory effects, signifying an antagonistic role for activated ERα on CIITA pIV activity. Moreover, STAT1 signaling, necessary for CIITA pIV activation, and selected STAT1 regulated genes were variably downregulated by E₂ in transfected and endogenous ERα positive breast cancer cells, whereas STAT1 signaling was noticeably augmented in ERα⁻ breast cancer cells. Collectively, these results imply immune escape mechanisms in ERα⁺ breast cancer may be facilitated through an ERα suppressive mechanism on IFN-γ signaling.

  8. 3D synthetic aperture PIV measurements from artificial vibrating vocal folds

    Daily, Jesse; Belden, Jesse; Thomson, Scott; Truscott, Tadd


    During speech, air from the lungs is forced past the vocal folds which vibrate, producing sound. A pulsatile jet of air is formed downstream of the vibrating folds which interacts with the various structures in the airway. Currently, it is postulated that the way this jet interacts with the downstream structures in the airway directly affects the quality of human speech. In order to better understand this jet, it is desirable to visualize the jet in three dimensions. We present the results of a method that reconstructs the three dimensional velocity field using Synthetic aperture PIV (SAPIV) \\cite{Belden:2010}. SAPIV uses an array of high-speed cameras to artificially create a single camera with a variable focal length. This is accomplished by overlapping the images from the array to create a "focal stack". As the images are increasingly overlapped, more distant image planes come into focus. 3D PIV is then performed on the "refocused" focal stack to reconstruct the flow field in three dimensions. SAPIV has th...

  9. DeepPIV: Particle image velocimetry measurements using deep-sea, remotely operated vehicles

    Katija, Kakani; Sherman, Alana; Graves, Dale; Klimov, Denis; Kecy, Chad; Robison, Bruce


    The midwater region of the ocean (below the euphotic zone and above the benthos) is one of the largest ecosystems on our planet, yet remains one of the least explored. Little-known marine organisms that inhabit midwater have developed life strategies that contribute to their evolutionary success, and may inspire engineering solutions for societally relevant challenges. Although significant advances in underwater vehicle technologies have improved access to midwater, small-scale, in situ fluid mechanics measurement methods that seek to quantify the interactions that midwater organisms have with their physical environment are lacking. Here we present DeepPIV, an instrumentation package affixed to remotely operated vehicles that quantifies fluid motions from the surface of the ocean down to 4000 m depths. Utilizing ambient suspended particulate, fluid-structure interactions are evaluated on a range of marine organisms in midwater. Initial science targets include larvaceans, biological equivalents of flapping flexible foils, that create mucus houses to filter food. Little is known about the structure of these mucus houses and the function they play in selectively filtering particles, and these dynamics can serve as particle-mucus models for human health. Using DeepPIV, we reveal the complex structures and flows generated within larvacean mucus houses, and elucidate how these structures function. Funding is gratefully acknowledged from the Packard Foundation.

  10. Comparison of PIV with 4D-Flow in a physiological accurate flow phantom

    Sansom, Kurt; Balu, Niranjan; Liu, Haining; Aliseda, Alberto; Yuan, Chun; Canton, Maria De Gador


    Validation of 4D MRI flow sequences with planar particle image velocimetry (PIV) is performed in a physiologically-accurate flow phantom. A patient-specific phantom of a carotid artery is connected to a pulsatile flow loop to simulate the 3D unsteady flow in the cardiovascular anatomy. Cardiac-cycle synchronized MRI provides time-resolved 3D blood velocity measurements in clinical tool that is promising but lacks a robust validation framework. PIV at three different Reynolds numbers (540, 680, and 815, chosen based on +/- 20 % of the average velocity from the patient-specific CCA waveform) and four different Womersley numbers (3.30, 3.68, 4.03, and 4.35, chosen to reflect a physiological range of heart rates) are compared to 4D-MRI measurements. An accuracy assessment of raw velocity measurements and a comparison of estimated and measureable flow parameters such as wall shear stress, fluctuating velocity rms, and Lagrangian particle residence time, will be presented, with justification for their biomechanics relevance to the pathophysiology of arterial disease: atherosclerosis and intimal hyperplasia. Lastly, the framework is applied to a new 4D-Flow MRI sequence and post processing techniques to provide a quantitative assessment with the benchmarked data. Department of Education GAANN Fellowship.

  11. Identification of the gate regions in the primary structure of the secretin pIV.

    Spagnuolo, Julian; Opalka, Natacha; Wen, Wesley X; Gagic, Dragana; Chabaud, Elodie; Bellini, Pierdomenico; Bennett, Matthew D; Norris, Gillian E; Darst, Seth A; Russel, Marjorie; Rakonjac, Jasna


    Secretins are a family of large bacterial outer membrane channels that serve as exit ports for folded proteins, filamentous phage and surface structures. Despite the large size of their substrates, secretins do not compromise the barrier function of the outer membrane, implying a gating mechanism. The region in the primary structure that forms the putative gate has not previously been determined for any secretin. To identify residues involved in gating the pIV secretin of filamentous bacteriophage f1, we used random mutagenesis of the gene followed by positive selection for mutants with compromised barrier function ('leaky' mutants). We identified mutations in 34 residues, 30 of which were clustered into two regions located in the centre of the conserved C-terminal secretin family domain: GATE1 (that spanned 39 residues) and GATE2 (that spanned 14 residues). An internal deletion constructed in the GATE2 region resulted in a severely leaky phenotype. Three of the four remaining mutations are located in the region that encodes the N-terminal, periplasmic portion of pIV and could be involved in triggering gate opening. Two missense mutations in the 24-residue region that separates GATE1 and GATE2 were also constructed. These mutant proteins were unstable, defective in multimerization and non-functional.

  12. PIV Investigations of the Flow Field in the Volute of a Rotary Blood Pump

    Sankovic, John M.; Kadambi, Jaikrishnan R.; Smith, William A.; Wernet, Mark P.


    A full-size acrylic model of a rotary blood pump was developed in order to utilize Particle Image Velocimetry (PIV) to make measurements of the fluid velocities and turbulent stresses throughout the device. The development of an understanding of the hemodynamics within the blood pump is critical to the development and validation of computational models. A blood analog solution, consisting of sodium iodide solution and glycerin, was developed to match physiological kinematic viscosity. The refractive indices of the fluid, the pump casing, and the impeller were matched to facilitate the use of PIV to make velocity measurements. Velocity measurements made in the volute exit/diffuser region are presented for pumps speeds of 3000-3850 rpm. At each speed data were obtained at a physiological pressure of 12 kPa and at a maximum flow condition. Four hundred data pairs were used for each resultant mean velocity vector value, representing greater than an order of magnitude more data pairs than reported previously in the literature on similar devices and resulting in velocity uncertainty levels of approximately 22.9%.

  13. Characterization of Unsteady Flow Structures Near Leading-Edge Slat. Part 1; PIV Measurements

    Jenkins, Luther N.; Khorrami, Mehdi R.; Choudhari, Meelan


    A comprehensive computational and experimental study has been performed at the NASA Langley Research Center as part of the Quiet Aircraft Technology (QAT) Program to investigate the unsteady flow near a leading-edge slat of a two-dimensional, high-lift system. This paper focuses on the experimental effort conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART) where Particle Image Velocimetry (PIV) data was acquired in the slat cove and at the slat trailing edge of a three-element, high-lift model at 4, 6, and 8 degrees angle of attack and a freestream Mach Number of 0.17. Instantaneous velocities obtained from PIV images are used to obtain mean and fluctuating components of velocity and vorticity. The data show the recirculation in the cove, reattachment of the shear layer on the slat lower surface, and discrete vortical structures within the shear layer emanating from the slat cusp and slat trailing edge. Detailed measurements are used to examine the shear layer formation at the slat cusp, vortex shedding at the slat trailing edge, and convection of vortical structures through the slat gap. Selected results are discussed and compared with unsteady, Reynolds-Averaged Navier-Stokes (URANS) computations for the same configuration in a companion paper by Khorrami, Choudhari, and Jenkins (2004). The experimental dataset provides essential flow-field information for the validation of near-field inputs to noise prediction tools.

  14. Sub-piexl methods for improving vector quality in echo PIV flow, imaging technology.

    Niu, Lili; Wang, Jing; Qian, Ming; Zheng, Hairong


    Developments of many cardiovascular problems have been shown to have a close relationship with arterial flow conditions. An ultrasound-based particle image velocimetry technique(Echo PIV) was recently developed to measure multi-component velocity vectors and local shear rates in arteries and opaque fluid flows by identifying and tracking flow tracers (ultrasound contrast microbubbles) within these flow fields. To improve the measurement accuracy, sub-pixel calculation method was adopted in this paper to maximize the ultrasound RF signal and B mode image correlation accuracy and increase the image spatial resolution. This algorithm is employed in processing both computer-generated particle image patterns and the B-mode images of microbubbles in rotating flows obtained by a high frame rate (up to 1000 frames per second) ultrasound imaging system. The results show the correlation of particle patterns and individual flow vector quality are improved and the overall flow mappings are also improved significantly. This would help the Echo PIV system to provide better multi-component velocity accuracy.

  15. A Dual-Plane PIV Study of Turbulent Heat Transfer Flows

    Wernet, Mark P.; Wroblewski, Adam C.; Locke, Randy J.


    Thin film cooling is a widely used technique in turbomachinery and rocket propulsion applications, where cool injection air protects a surface from hot combustion gases. The injected air typically has a different velocity and temperature from the free stream combustion flow, yielding a flow field with high turbulence and large temperature differences. These thin film cooling flows provide a good test case for evaluating computational model prediction capabilities. The goal of this work is to provide a database of flow field measurements for validating computational flow prediction models applied to turbulent heat transfer flows. In this work we describe the application of a Dual-Plane Particle Image Velocimetry (PIV) technique in a thin film cooling wind tunnel facility where the injection air stream velocity and temperatures are varied in order to provide benchmark turbulent heat transfer flow field measurements. The Dual-Plane PIV data collected include all three components of velocity and all three components of vorticity, spanning the width of the tunnel at multiple axial measurement planes.

  16. Tomographic Aperture-Encoded Particle Tracking Velocimetry: A New Approach to Volumetric PIV

    Troolin, Dan; Boomsma, Aaron; Lai, Wing; Pothos, Stamatios; Fluid Mechanics Research Instruments Team


    Volumetric velocity fields are useful in a wide variety of fluid mechanics applications. Several types of three-dimensional imaging methods have been used in the past to varying degrees of success, for example, 3D PTV (Maas et al., 1993), DDPIV (Peireira et al., 2006), Tomographic PIV (Elsinga, 2006), and V3V (Troolin and Longmire, 2009), among others. Each of these techniques has shown advantages and disadvantages in different areas. With the advent of higher resolution and lower noise cameras with higher stability levels, new techniques are emerging that combine the advantages of the existing techniques. This talk describes a new technique called Tomographic Aperture-Encoded Particle Tracking Velocimetry (TAPTV), in which segmented triangulation and diameter tolerance are used to achieve three-dimensional particle tracking with extremely high particle densities (on the order of ppp = 0.2 or higher) without the drawbacks normally associated with ghost particles (for example in TomoPIV). The results are highly spatially-resolved data with very fast processing times. A detailed explanation of the technique as well as plots, movies, and experimental considerations will be discussed.

  17. Evaluating the accuracy performance of Lucas-Kanade algorithm in the circumstance of PIV application

    Pan, Chong; Xue, Dong; Xu, Yang; Wang, JinJun; Wei, RunJie


    Lucas-Kanade (LK) algorithm, usually used in optical flow filed, has recently received increasing attention from PIV community due to its advanced calculation efficiency by GPU acceleration. Although applications of this algorithm are continuously emerging, a systematic performance evaluation is still lacking. This forms the primary aim of the present work. Three warping schemes in the family of LK algorithm: forward/inverse/symmetric warping, are evaluated in a prototype flow of a hierarchy of multiple two-dimensional vortices. Second-order Newton descent is also considered here. The accuracy & efficiency of all these LK variants are investigated under a large domain of various influential parameters. It is found that the constant displacement constraint, which is a necessary building block for GPU acceleration, is the most critical issue in affecting LK algorithm's accuracy, which can be somehow ameliorated by using second-order Newton descent. Moreover, symmetric warping outbids the other two warping schemes in accuracy level, robustness to noise, convergence speed and tolerance to displacement gradient, and might be the first choice when applying LK algorithm to PIV measurement.

  18. Characteristics of Embedded-Shock-Free Compressible Vortex Rings: A Detailed Study Using PIV

    C. Lakshmana Dora


    Full Text Available The present study focus on evolution of compressible vortex ring generated at the open end of a shock tube through accurate measurement of velocity field using Particle Image Velocimetry (PIV. To investigate the unsteady characteristics of embedded shock-free, low Mach number vortex rings, two cases (shock Mach numbers, M=1.27 and M=1.37 are considered for PIV measurements. Time-dependent variations of circulation, core and ring diameters, and ring velocity are calculated from the measured velocity field. Pinching-off process is investigated in detail for both cases. Formation time and the time of complete detachment of the vortex ring from the trailing jet are identified from the velocity and vorticity field. The ring formation is complete at about t*(=tUb/D=1.75 and 1.65 for M=1.27 and 1.37, respectively, where t is time, Ub is fluid velocity behind the shock at exit, and D is tube diameter. Complete detachment of the vortex ring from the trailing jet is observed at t∗=2 and 2.9 for M=1.27 and 1.37, respectively.

  19. Hydrodynamics and PIV study in the impingement zone formed by a droplet train

    Kanjirakat, Anoop; Sadr, Reza; Zhang, Taolue; Muthusamy, Jayaveera; Alvarado, Jorge; Texas A; M University at Qatar Collaboration; Texas A; M University College Station Collaboration


    Droplet impingement is encountered in numerous technical applications, such as ink jet printing, spray cooling, and fuel injection in internal combustion engines. Even though many studies in droplet impingement were conducted in past, not many have measured the near-wall velocities in the droplet impingement zone. With the goal of gaining a better understanding of the hydrodynamics in the impingement zone, well-controlled experiments are performed in combination with micro-PIV measurements and numerical simulations. Hydrodynamics of HFE-7100 droplets generated using a piezoelectric droplet generator, impinging on a pre-wetted surface is investigated. Micro-PIV studies in the high-velocity impingement zone are performed using one-micron meter fluorescent particles dispersed in HFE-7100 along with the double exposed images. Three-dimensional and 2D-axisymmetric numerical modeling for a transient droplet crown development is performed. The interface between the gas and the liquid is modeled using a Volume of Fluid (VOF) method. Numerical simulation results obtained are observed to be in good agreement with that of the experimental observations. Supported by National Priority Research Program (NPRP) of Qatar National Research Fund (QNRF), Grant No.: NPRP 6-1304-2-525.

  20. PIV Measurement of Wall Shear Stress and Flow Structures within an Intracranial Aneurysm Model

    Chow, Ricky; Sparrow, Eph; Campbell, Gary; Divani, Afshin; Sheng, Jian


    The formation and rupture of an intracranial aneurysm (IA) is a debilitating and often lethal event. Geometric features of the aneurysm bulb and upstream artery, such as bulb size, bulb shape, and curvature of the artery, are two groups of factors that define the flow and stresses within an IA. Abnormal flow stresses are related to rupture. This presentation discusses the development of a quasi-3D PIV technique and its application in various glass models at Re = 275 and 550 to experimentally assess at a preliminary level the impact of geometry and flow rate. Some conclusions are to be drawn linking geometry of the flow domain to rupture risk. The extracted results also serve as the baseline case and as a precursor to a companion presentation by the authors discussing the impact of flow diverters, a new class of medical devices. The PIV experiments were performed in a fully index-matched flow facility, allowing for unobstructed observations over complex geometry. A reconstruction and analysis method was devised to obtain 3D mean wall stress distributions and flow fields. The quasi 3D measurements were reconstructed from orthogonal planes encompassing the entire glass model, spaced 0.4mm apart. Wall shear stresses were evaluated from the near-wall flow viscous stresses.

  1. In vivo measurement of hemodynamic information in stenosed rat blood vessels using X-ray PIV

    Park, Hanwook; Park, Jun Hong; Lee, Sang Joon


    Measurements of the hemodynamic information of blood flows, especially wall shear stress (WSS), in animal models with circulatory vascular diseases (CVDs) are important to understand the pathological mechanism of CVDs. In this study, X-ray particle image velocimetry (PIV) with high spatial resolution was applied to obtain velocity field information in stenosed blood vessels with high WSS. 3D clips fabricated with a 3D printer were applied to the abdominal aorta of a rat cadaver to induce artificial stenosis in the real blood vessel of an animal model. The velocity and WSS information of blood flows in the stenosed vessel were obtained and compared at various stenosis severities. In vivo measurement was also conducted by fastening a stenotic clip on a live rat model through surgical intervention to reduce the flow rate to match the limited temporal resolution of the present X-ray PIV system. Further improvement of the temporal resolution of the system might be able to provide in vivo measurements of hemodynamic information from animal disease models under physiological conditions. The present results would be helpful for understanding the relation between hemodynamic characteristics and the pathological mechanism in animal CVD models.

  2. Two-phase PIV measurements of particle suspension in a forced impinging jet

    Mulinti, Rahul; Kiger, Ken


    The condition of rotorcraft brownout is characterized by intense dust suspension that is uplifted during landing and takeoff operations in regions covered with loose sediment. To predict particle suspension and sedimentation within coupled particle-laden flows, detailed characterization of the micro-scale mechanics is needed within a prototypical flow that captures the essence of the rotorcraft/ground wake interactions. Two-phase PIV has been used to study the interaction of a sediment bed made of glass spheres with characteristic flow structures reminiscent from flow within a rotor wake. In order to make reliable simultaneous two-phase PIV measurements, a phase discrimination algorithm from a single two-phase image has been implemented. The validity of the separation is checked by processing images that consisted only of the very small tracer particles, or only the dispersed phase particles, and examining how much "cross-talk" was present between the phases. The mobilization and wall-normal flux of particulates by the vortex-wall interaction will be reported for several different operational conditions, and correlated to the local vortex conditions.

  3. Neural network approaches to tracer identification as related to PIV research

    Seeley, C.H. Jr.


    Neural networks have become very powerful tools in many fields of interest. This thesis examines the application of neural networks to another rapidly growing field flow visualization. Flow visualization research is used to experimentally determine how fluids behave and to verify computational results obtained analytically. A form of flow visualization, particle image velocimetry (PIV). determines the flow movement by tracking neutrally buoyant particles suspended in the fluid. PIV research has begun to improve rapidly with the advent of digital imagers, which can quickly digitize an image into arrays of grey levels. These grey level arrays are analyzed to determine the location of the tracer particles. Once the particles positions have been determined across multiple image frames, it is possible to track their movements, and hence, the flow of the fluid. This thesis explores the potential of several different neural networks to identify the positions of the tracer particles. Among these networks are Backpropagation, Kohonen (counter-propagation), and Cellular. Each of these algorithms were employed in their basic form, and training and testing were performed on a synthetic grey level array. Modifications were then made to them in attempts to improve the results.

  4. Time-resolved X-ray PIV measurements of hemodynamic information of real pulsatile blood flows

    Park, Hanwook; Yeom, Eunseop; Lee, Sang Joon


    X-ray imaging technique has been used to visualize various bio-fluid flow phenomena as a nondestructive manner. To obtain hemodynamic information related with circulatory vascular diseases, a time-resolved X-ray PIV technique with high temporal resolution was developed. In this study, to embody actual pulsatile blood flows in a circular conduit without changes in hemorheological properties, a bypass loop is established by connecting a microtube between the jugular vein and femoral artery of a rat. Biocompatible CO2 microbubbles are used as tracer particles. After mixing with whole blood, CO2 microbubbles are injected into the bypass loop. Particle images of the pulsatile blood flows in the bypass loop are consecutively captured by the time-resolved X-ray PIV system. The velocity field information are obtained with varying flow rate and pulsataility. To verify the feasibility of the use of CO2 microbubbles under in vivo conditions, the effects of the surrounding-tissues are also investigated, because these effects are crucial for deteriorating the image contrast of CO2 microbubbles. Therefore, the velocity information of blood flows in the abdominal aorta are obtained to demonstrate the visibility and usefulness of CO2 microbubbles under ex vivo conditions. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2008-0061991).

  5. A Micro-PIV Study of the Pulsed Micro-Flows Driven by an Insulin Pump

    Wang, Bing; Demuren, Ayodeji; Gyuricsko, Eric; Hu, Hui


    In recent years, there is a surge in the popularity of using insulin pump or continuous subcutaneous insulin infusion therapy, as opposed to multiple daily injections by insulin syringe or an insulin pen. Some case studies have suggested that insulin delivery failure may be caused by precipitation of insulin within the infusion set. Speculation also exists that the flow of insulin through an insulin infusion set may be reduced or inhibited by air bubbles entrained into the micro-sized tubing system since there are chances that air be introduced into the insulin reservoir during the filling process. In the present study, a microscopic Particle Image Velocimtry (micro-PIV) system was used to characterize the transient behavior of the pulsed micro-flows inside the micro-sized tubing system of an insulin infusion set with insulin pump operating in basal mode (i.e., pulsed insulin pumping). The effects of the air bubbles entrained into the micro-sized tubing system on the insulin delivery process were assessed based on the micro-PIV measurements.

  6. Tomo-PIV measurement of flow around an arbitrarily moving body with surface reconstruction

    Im, Sunghyuk; Jeon, Young Jin; Sung, Hyung Jin


    A three-dimensional surface of an arbitrarily moving body in a flow field was reconstructed using the DAISY descriptor and epipolar geometry constraints. The surface shape of a moving body was reconstructed with tomographic PIV flow measurement. Experimental images were captured using the tomographic PIV system, which consisted of four high-speed cameras and a laser. The originally captured images, which contained the shape of the arbitrary moving body and the tracer particles, were separated into the particle and surface images using a Gaussian smoothing filter. The weak contrast of the surface images was enhanced using a local histogram equalization method. The histogram-equalized surface images were used to reconstruct the surface shape of the moving body. The surface reconstruction method required a sufficiently detailed surface pattern to obtain the intensity gradient profile of the local descriptor. The separated particle images were used to reconstruct the particle volume intensity via tomographic reconstruction approaches. Voxels behind the reconstructed body surface were neglected during the tomographic reconstruction and velocity calculation. The three-dimensional three-component flow vectors were calculated based on the cross-correlation functions between the reconstructed particle volumes. Three-dimensional experiments that modeled the flows around a flapping flag, a rotating cylinder, and a flapping robot fish tail were conducted to validate the present technique.

  7. DHMPIV and Tomo-PIV measurements of three-dimensional structures in a turbulent boundary layer

    Amili, O.; Atkinson, C.; Soria, J.

    In turbulent boundary layers, a large portion of total turbulence production happens in the near wall region, y/δ Tomo-PIV) was used to extract the 3C-3D velocity field using a rapid and less memory intensive reconstruction algorithm. It is based on a multiplicative line-of-sight (MLOS) estimation that determines possible particle locations in the volume, followed by simultaneous iterative correction. Application of MLOS-SART and MART to a turbulent boundary layer at Refθ=2200 using a 4 camera Tomo-PIV system with a volume of 1000×1000×160 voxels is discussed. In addition, near wall velocity measurement attempt made by digital holographic microscopic particle image velocimetry (DHMPIV). The technique provides a solution to overcome the poor axial accuracy and the low spatial resolution which are common problems in digital holography [5]. By reducing the depth of focus by at least one order of magnitude as well as increasing the lateral spatial resolution, DHMPIV provides the opportunity to resolve the small-scale structures existing in near wall layers.

  8. PIV study of near-field tip vortex behind perforated Gurney flaps

    Lee, T.


    The impact of Gurney flaps, of different heights and perforations, on the growth and development of a tip vortex, both along the tip and in the near field of a finite NACA 0012 wing, at Re = 1.05 × 105 was investigated by using particle image velocimetry (PIV). Wind-tunnel force balance measurements were also made to supplement the PIV results. This study is a continuation of the work of Lee and Ko (Exp Fluids 46(6):1005-1019, 2009) on the near-wake measurements behind perforated Gurney flaps. The present results show that along the tip, the overall behavior of the secondary vortices and their interaction with the primary, or tip, vortex remained basically unchanged, regardless of flap height and perforation. The peak vorticity of the tip vortex, however, increased with flap height and always exhibited a local maximum at x/ c = 0.8 (from the leading edge). In the near field, the strength and structure of the near-field tip vortex were found to vary greatly with the flap height and perforation. The small flaps produced a more concentrated tip vortex with an increased circulation, while the large Gurney flaps caused a disruption of the tip vortex. The disrupted vortex can, however, be re-established by the addition of flap perforation. The larger the flap perforation the more organized the tip vortex. The Gurney flaps have the potential to serve as an alternative off-design wake vortex control device.

  9. Mixing by internal waves quantified using combined PIV/PLIF technique

    Dossmann, Y.; Bourget, B.; Brouzet, C.; Dauxois, T.; Joubaud, S.; Odier, P.


    We present a novel characterization of mixing events associated with the propagation and overturning of internal waves studied, thanks to the simultaneous use of particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques. This combination of techniques had been developed earlier to provide an access to simultaneous velocity and density fields in two-layer stratified flows with interfacial gravity waves. Here, for the first time, we show how it is possible to implement it quantitatively in the case of a continuously stratified fluid where internal waves propagate in the bulk. We explain in details how the calibration of the PLIF data is performed by an iterative procedure, and we describe the precise spatial and temporal synchronizations of the PIV and PLIF measurements. We then validate the whole procedure by characterizing the triadic resonance instability (TRI) of an internal wave mode. Very interestingly, the combined technique is then applied to a precise measurement of the turbulent diffusivity K t associated with mixing events induced by an internal wave mode. Values up to K t = 15 mm2 s-1 are reached when TRI is present (well above the noise of our measurement, typically 1 mm2 s-1), unambiguously confirming that TRI is a potential pathway to turbulent mixing in stratified flows. This work therefore provides a step on the path to new measurements for internal waves.

  10. PIV study of the wake of a model wind turbine transitioning between operating set points

    Houck, Dan; Cowen, Edwin (Todd)


    Wind turbines are ideally operated at their most efficient tip speed ratio for a given wind speed. There is increasing interest, however, in operating turbines at other set points to increase the overall power production of a wind farm. Specifically, Goit and Meyers (2015) used LES to examine a wind farm optimized by unsteady operation of its turbines. In this study, the wake of a model wind turbine is measured in a water channel using PIV. We measure the wake response to a change in operational set point of the model turbine, e.g., from low to high tip speed ratio or vice versa, to examine how it might influence a downwind turbine. A modified torque transducer after Kang et al. (2010) is used to calibrate in situ voltage measurements of the model turbine's generator operating across a resistance to the torque on the generator. Changes in operational set point are made by changing the resistance or the flow speed, which change the rotation rate measured by an encoder. Single camera PIV on vertical planes reveals statistics of the wake at various distances downstream as the turbine transitions from one set point to another. From these measurements, we infer how the unsteady operation of a turbine may affect the performance of a downwind turbine as its incoming flow. National Science Foundation and the Atkinson Center for a Sustainable Future.

  11. Investigations on controlled transition development in a laminar separation bubble by means of LDA and PIV

    Lang, M.; Rist, U.; Wagner, S. [Institut fuer Aerodynamik und Gasdynamik, Universitaet Stuttgart, Pfaffenwaldring 21, 70550, Stuttgart (Germany)


    When a laminar boundary layer separates because of an adverse streamwise pressure gradient, the flow is subject to increased instability with respect to small-amplitude disturbances. Laminar-turbulent transition occurs under a rapid three-dimensional (3D) development within the separated shear layer. When the following turbulent boundary layer reattaches, a laminar separation bubble is formed. To allow controlled measurements, a small-amplitude Tollmien-Schlichting wave (TS wave) was introduced into the boundary layer without (case I) and with (case II) spanwise forcing of steady 3D disturbances. Combined application of laser-Doppler anemometry (LDA) and particle image velocimetry (PIV) demonstrates the suitability of both measurement techniques to capture the development of unsteady, periodic phenomena. The transition mechanism occurring in the flow field under consideration is discussed, and results obtained by controlled measurements are compared to direct numerical simulations (DNS) and predictions from linear stability theory (LST). Flow visualizations and stereoscopic PIV measurements give better insight into the 3D breakdown of the separated shear layer. (orig.)

  12. Quantitative flow characteristics for side-by-side square cylinders via PIV

    Dogan Sercan


    Full Text Available In this study, instantaneous and time-averaged flow structures downstream of the sharp-edged single and two and three side-by-side square cylinders (SCs immersed in a uniform open channel water flow were studied by a technique of particle image velocimetry (PIV. Experimental results of wake flow structures were presented for gap ratios (G/D in the range of 1.0”G/D”3.0 for Reynolds number values of 1050, 2450 and 3400. Flow structures depending on the square cylinder (SC configurations and Reynolds number were discussed. It has been found that the development of the vortex shedding as well as the flow structure were substantially altered for side-by-side SCs comparing to the single SC. Asymmetrical and biased wake structures were observed because of the jetlike flow between the SCs for two SCs cases for the gap ratio less than 2.0. Depending on the gap spacing between the SCs, the interaction results of time2 averaged vorticity, velocity vector field, Reynolds stress correlations and streamline patterns in the wake region form a distinguished flow structure. Strouhal numbers for the single square cylinder for 1050≤Re≤3400 are found in the range of 0.12-0.13. The present results have supported the previous works by providing detailed quantitative experimental information with PIV in the wake region of the SC and might be helpful for validation of numerical studies and designers.

  13. Flow characteristics in free impinging jet reactor by particle image velocimetry (PIV) investigation

    Zhang, Jun; Liu, Youzhi; Qi, Guisheng; Jiao, Weizhou; Yuan, Zhiguo


    The flow characteristics in free impinging jet reactors (FIJRs) were investigated using particle image velocimetry (PIV). The effects of the Reynolds number (Re) and the ratio of jet distance to jet diameter (w/d) on flow behavior were discussed for equal volumetric flow rates of the two jets. The impingement plane, instantaneous velocity, mean velocity, and turbulent kinetic energy (TKE) distribution of FIJRs are measured from captured images using the PIV technique. As Re increases, the average diameter of the impingement plane linearly increases. The instability of the liquid is closely related to the jet velocity or the Re. However, the stagnation point is insensitive to the variation of the Re. The droplets break up from the turbulent liquid in the ‘wall-free’ environment of FIJRs, so that the liquid back-flow found in confined impinging jet reactors (CIJRs) is not observed. Increasing the Re from 1800-4100 or decreasing the w/d from 20-6 plays a similar role in increasing the TKE values and intensifying turbulence, which promotes the momentum transfer and mixing efficiency in FIJRs.

  14. Isothermal flow measurement using planar PIV in the 1/4 scaled model of CANDU reactor

    Im, Sunghyuk; Sung, Hyung Jin [KAIST, Daejeon (Korea, Republic of); Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of); Kim, Hyoung Tae [KAERI, Daejeon (Korea, Republic of)


    The local temperature of the moderator is a key parameter in determining the available subcooling. To predict the flow field and local temperature distribution in the calandria, Korea Atomic Energy Research Institute (KAERI) started the experimental research on moderator circulation as one of a national R and D research programs from 2012. This research program includes the construction of the Moderator Circulation Test (MCT) facility, production of the validation data for self-reliant CFD tools, and development of optical measurement system using the Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) techniques. Small-scale 1/40 and 1/8 small-scale model tests were performed prior to installation of the main MCT facility to identify the potential problems of the flow visualization and measurement expected in the 1/4 scale MCT facility. In the 1/40 scale test, a flow field was measured with a PIV measurement technique under an iso-thermal state, and the temperature field was visualized using a LIF technique. In this experiment, the key point was to illuminate the region of interest as uniformly as possible since the velocity and temperature fields in the shadow regions were distorted and unphysical. In the 1/8 scale test, the flow patterns from the inlet nozzles to the top region of the tank were investigated using PIV measurement at two different positions of the inlet nozzle. For each position of laser beam exposure the measurement sections were divided to 7 groups to overcome the limitation of the laser power to cover the relatively large test section. The MCT facility is the large-scale facility designed to reproduce the important characteristics of moderator circulation in a CANDU6 calandria under a range of operating conditions. It is reduced in a 1/4 scale and a moderator test vessel is built to the specifications of the CANDU6 reactor design, where a working fluid is sub-cooled water with atmospheric pressure. Previous studies were

  15. Evaluation of the Performance of Vortex Generators on the DU 91-W2-250 Profile using Stereoscopic PIV

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik


    Stereoscopic PIV measurements investigating the effect of Vortex Generators on the lift force near stall and on glide ratio at best aerodynamic performance have been carried out in the LM Glasfiber wind tunnel on a DU 91-W2-250 profile. Measurements at two Reynolds numbers were analyzed; Re=0...

  16. Evaluation of the Performance of Vortex Generators on the DU 91-W2-250 Profile using Stereoscopic PIV

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik


    Stereoscopic PIV measurements investigating the effect of Vortex Generators on the lift force near stall and on glide ratio at best aerodynamic performance have been carried out in the LM Glasfiber wind tunnel on a DU 91-W2-250 profile. Measurements at two Reynolds numbers were analyzed; Re=0...

  17. X-ray PIV measurement of blood flow in deep vessels of a rat: An in vivo feasibility study.

    Park, Hanwook; Yeom, Eunseop; Lee, Sang Joon


    X-ray PIV measurement is a noninvasive approach to measure opaque blood flows. However, it is not easy to measure real pulsatile blood flows in the blood vessels located at deep position of the body, because the surrounding tissues significantly attenuate the contrast of X-ray images. This study investigated the effect of surrounding tissues on X-ray beam attenuation by measuring the velocity fields of blood flows in deep vessels of a live rat. The decrease in image contrast was minimized by employing biocompatible CO2 microbubbles as tracer particles. The maximum measurable velocity of blood flows in the abdominal aorta of a rat model was found through comparative examination between the PIV measurement accuracy and the level of image contrast according to the input flow rate. Furthermore, the feasibility of using X-ray PIV to accurately measure in vivo blood flows was demonstrated by determining the velocity field of blood flows in the inferior vena cava of a rat. This study may serve as a reference in conducting in vivo X-ray PIV measurements of pulsatile blood flows in animal disease models and investigating hemodynamic characteristics and circulatory vascular diseases.

  18. Reconstruction of 3D flow structures in a cylindrical cavity with a rotating lid using time-resolved stereo PIV

    Meyer, Knud Erik; Sørensen, Jens Nørkær; Naumov, Igor


    Time-resolved Particle Image Velocimetry (PIV) measurements in two perpendicular planes are used to reconstruct a flow in an axisymmetric facility in both time and space. The reconstruction is based on Proper Orthogonal Decomposition (POD) and is used to distinguish between spatial and temporal...

  19. X-ray PIV measurement of blood flow in deep vessels of a rat: An in vivo feasibility study

    Park, Hanwook; Yeom, Eunseop; Lee, Sang Joon


    X-ray PIV measurement is a noninvasive approach to measure opaque blood flows. However, it is not easy to measure real pulsatile blood flows in the blood vessels located at deep position of the body, because the surrounding tissues significantly attenuate the contrast of X-ray images. This study investigated the effect of surrounding tissues on X-ray beam attenuation by measuring the velocity fields of blood flows in deep vessels of a live rat. The decrease in image contrast was minimized by employing biocompatible CO2 microbubbles as tracer particles. The maximum measurable velocity of blood flows in the abdominal aorta of a rat model was found through comparative examination between the PIV measurement accuracy and the level of image contrast according to the input flow rate. Furthermore, the feasibility of using X-ray PIV to accurately measure in vivo blood flows was demonstrated by determining the velocity field of blood flows in the inferior vena cava of a rat. This study may serve as a reference in conducting in vivo X-ray PIV measurements of pulsatile blood flows in animal disease models and investigating hemodynamic characteristics and circulatory vascular diseases.

  20. A dual-beam dual-camera method for a battery-powered underwater miniature PIV (UWMPIV) system

    Wang, Binbin; Liao, Qian [University of Wisconsin-Milwaukee, Department of Civil Engineering and Mechanics, Milwaukee, WI (United States); Bootsma, Harvey A. [University of Wisconsin-Milwaukee, School of Freshwater Sciences, Milwaukee, WI (United States); Wang, Pei-Fang [Space and Naval Warfare Systems Center, Advanced Systems and Applied Sciences, Envrionmental Sciences, San Diego, CA (United States)


    A battery-powered in situ Underwater Miniature PIV (UWMPIV) has been developed and deployed for field studies. Instead of generating high-energy laser pulses as in a conventional PIV system, the UWMPIV employs a low-power Continuous Wave (CW) laser (class IIIb) and an oscillating mirror (galvanometer) to generate laser sheets. In a previous version of the UWMPIV, the time between exposures of a pair of particle images, {delta}t, could not be reduced without loss of illumination strength. This limitation makes it unsuitable for high-speed flows. In this paper, we present a technique to solve this problem by adopting two CW lasers with different wavelength and two CCD cameras in a second-generation UWMPIV system. Several issues including optical alignment, non-uniform distribution of {delta}t due to the varying speed of the scanning beam and local flow velocities are discussed. The timing issue is solved through a simple calibration procedure that involves the reconstruction of maps of laser beam arrival time. Comparison of the performance between the new method and a conventional PIV system is presented. Measurements were performed in a laboratory open-channel flume. Excellent agreement was found between the new method and the standard PIV measurement in terms of the extracted vertical profiles of mean velocity, RMS fluctuation, Reynolds stress and dissipation rate of turbulent kinetic energy. (orig.)

  1. LDA-PIV Diagnostics and 3D Simulation of Oscillating Swirl Flow in a Closed Cylindrical Container

    Naumov, Igor; Okulov, V. L.; Meyer, Knud Erik


    Results on unsteady vortex breakdown are obained simultaneously using two diagnostics methods: a) determination of velocity fields by particle tracks (Particle Image Velocimeter - PIV), b) determination of velocity fields by Laser Doppler Anemometry (LDA), are presented.The experiments data are i...

  2. Lagrangian and Eulerian pressure field evaluation of rod-airfoil flow from time-resolved tomographic PIV

    Violato, D.; Moore, P.; Scarano, F.


    This work investigates the rod-airfoil air flow by time-resolved Tomographic Particle Image Velocimetry (TR-TOMO PIV) in thin-light volume configuration. Experiments are performed at the region close to the leading edge of a NACA0012 airfoil embedded in the von Karman wake of a cylindrical rod. The

  3. Fluid trajectory evaluation based on an ensemble-averaged cross-correlation in time-resolved PIV

    Jeon, Young Jin; Chatellier, Ludovic; David, Laurent


    A novel multi-frame particle image velocimetry (PIV) method, able to evaluate a fluid trajectory by means of an ensemble-averaged cross-correlation, is introduced. The method integrates the advantages of the state-of-art time-resolved PIV (TR-PIV) methods to further enhance both robustness and dynamic range. The fluid trajectory follows a polynomial model with a prescribed order. A set of polynomial coefficients, which maximizes the ensemble-averaged cross-correlation value across the frames, is regarded as the most appropriate solution. To achieve a convergence of the trajectory in terms of polynomial coefficients, an ensemble-averaged cross-correlation map is constructed by sampling cross-correlation values near the predictor trajectory with respect to an imposed change of each polynomial coefficient. A relation between the given change and corresponding cross-correlation maps, which could be calculated from the ordinary cross-correlation, is derived. A disagreement between computational domain and corresponding physical domain is compensated by introducing the Jacobian matrix based on the image deformation scheme in accordance with the trajectory. An increased cost of the convergence calculation, associated with the nonlinearity of the fluid trajectory, is moderated by means of a V-cycle iteration. To validate enhancements of the present method, quantitative comparisons with the state-of-arts TR-PIV methods, e.g., the adaptive temporal interval, the multi-frame pyramid correlation and the fluid trajectory correlation, were carried out by using synthetically generated particle image sequences. The performances of the tested methods are discussed in algorithmic terms. A high-rate TR-PIV experiment of a flow over an airfoil demonstrates the effectiveness of the present method. It is shown that the present method is capable of reducing random errors in both velocity and material acceleration while suppressing spurious temporal fluctuations due to measurement noise.

  4. Towards 3C-3D digital holographic fluid velocity vector field measurement—tomographic digital holographic PIV (Tomo-HPIV)

    Soria, J.; Atkinson, C.


    Most unsteady and/or turbulent flows of geophysical and engineering interest have a highly three-dimensional (3D) complex topology and their experimental investigation is in pressing need of quantitative velocity measurement methods that are robust and can provide instantaneous 3C-3D velocity field data over a significant volumetric domain of the flow. This paper introduces and demonstrates a new method that uses multiple digital CCD array cameras to record in-line digital holograms of the same volume of seed particles from multiple orientations. This technique uses the same basic equipment as Tomo-PIV minus the camera lenses, it overcomes the depth-of-field problem of digital in-line holography and does not require the complex optical calibration of Tomo-PIV. The digital sensors can be oriented in an optimal manner to overcome the depth-of-field limitation of in-line holograms recorded using digital CCD or CMOS array cameras, resulting in a 3D reconstruction of the seed particles within the volume of interest, which can subsequently be analysed using 3D cross-correlation PIV analysis to yield a 3C-3D velocity field. A demonstration experiment of Tomo-HPIV using uniform translation with nominally 11 µm diameter seed particles shows that the 3D displacement derived from 3D cross-correlation Tomo-HPIV analysis can be measured within 5% of the imposed uniform translation, where the imposed uniform translation has an estimated standard uncertainty of 4.3%. So this paper proposes a multi-camera digital holographic imaging 3C-3D PIV method, which is identified as tomographic digital holographic PIV or Tomo-HPIV.

  5. Resuspension of particles in an oscillating grid turbulent flow using PIV and 3D-PTV

    Traugott, H; Liberzon, A [Turbulence Structure Laboratory, School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Hayse, T, E-mail: [Department of Civil Engineering, Massachusetts Institute of Technology, MA (United States)


    Description of the mechanisms responsible for the initiation of particle motion from a surface and re-entrainment of particles into suspension remains a challenge, partially due to the technical difficulties to quantify the forces applied on the particles and the collection of high resolution data of particle displacements simultaneously. In this study we explore the process of initial entrainment of spherical particles from smooth beds into zero-mean-shear turbulent flow in an oscillating grid chamber. Particle image velocimetry (PIV) and three-dimensional particle tracking velocimetry (3D-PTV) are used to correlate in a quantitative manner the turbulent flow properties responsible for pick-up, detachment and re-entrainment of particles. The results are compared to the existing models of critical shear velocity and provide further insight into the resuspension process of spherical particles in the transitional range of particle size Reynolds numbers 2 {<=} Re{sub p} {<=} 500.

  6. A further assessment of interpolation schemes for window deformation in PIV

    Kim, Byoung Jae; Sung, Hyung Jin


    We have evaluated the performances of the following seven interpolation schemes used for window deformation in particle image velocimetry (PIV): the linear, quadratic, B-spline, cubic, sinc, Lagrange, and Gaussian interpolations. Artificially generated images comprised particles of diameter in a range 1.1 ≤ d p ≤ 10.0 pixel were investigated. Three particle diameters were selected for detailed evaluation: d p = 2.2, 3.3, and 4.4 pixel with a constant particle concentration 0.02 particle/pixel2. Two flow patterns were considered: uniform and shear flow. The mean and random errors, and the computation times of the interpolation schemes were determined and compared.


    Liu Ying-zheng; Koyama Hide S.; Chen Han-ping


    The whole field measurements of swirling flow in spin-up and spin-down processes via PIV are presented in the paper. Investigation of the flow patterns at H/R=1.50 was experimentally carried out for the first time in both processes. By means of symmetry analysis, it is found that the overall flow structure in the spin-up process still keep axisymmetric to a great extent, but deteriorated very fast in the spin-down process. The time to settle to the state of rest in the spin-down process is found to be greatly shorter than the time to achieve the steady state in the spin-up process. Temporarily oscillatory vortex breakdown was discovered during the spin-up process, although no breakdown in the steady state at the same Reynolds number is found in precious researches.

  8. PIV measurement technique and its application%PIV测试技术及其应用

    徐玉明; 迟卫; 莫立新



  9. PIV Measurements of Chevrons on F400 Tactical Aircraft Nozzle Model

    Bridges, James; Wernet, Mark; Frate, Franco


    Previous talks at this meeting have covered our collaborative work on high-energy jets such as present in tactical aircraft (those with supersonic plumes). The emphasis of this work is improving our understanding of flow physics and our prediction tools. In this presentation we will discuss recent flow diagnostics acquired using Particle Image Velocimetry (PIV) made on an underexpanded shocked jet plume from a tactical aircraft nozzle. In this presentation we show cross-sectional and streamwise cuts of both mean and turbulent velocities of an F404 engine nozzle with various chevron designs applied. The impact of chevron penetration, length, and width are documented. The impact of the parameters is generally nonlinear in measures considered here, a surprising result given the relatively smooth behavior of the noise to variations in these chevron parameters.

  10. Investigation of a transonic separating/reattaching shear layer by means of PIV

    S. Scharnowski


    Full Text Available The separating/reattaching flow over an axisymmetric backward-facing step is analyzed experimentally by means of particle image velocimetry (PIV. The main purpose of the measurements is the investigation of the mean flow field as well as of the Reynolds stress distributions at a Mach number of 0.7 and at a Reynolds number of 3.3×105 based on the step height. Due to the strong progress of optical flow measurements in the last years it was possible to resolve all flow scales down to 180μm (≈1% of the step height with high precision. Thanks to the high spatial resolution it was found for the first time that the Reynolds stress distribution features a local minimum between the first part of the shear layer and a region inside the recirculation region. This implies a more complex wake dynamics than assumed before.

  11. Landing Gear Components Noise Study - PIV and Hot-Wire Measurements

    Hutcheson, Florence V.; Burley, Casey L.; Stead, Daniel J.; Becker, Lawrence E.; Price, Jennifer L.


    PIV and hot-wire measurements of the wake flow from rods and bars are presented. The test models include rods of different diameters and cross sections and a rod juxtaposed to a plate. The latter is representative of the latch door that is attached to an aircraft landing gear when the gear is deployed, while the single and multiple rod configurations tested are representative of some of the various struts and cables configuration present on an aircraft landing gear. The test set up is described and the flow measurements are presented. The effect of model surface treatment and freestream turbulence on the spanwise coherence of the vortex shedding is studied for several rod and bar configurations.

  12. Simultaneous, Unsteady PIV and Photogrammetry Measurements of a Tension-Cone Decelerator in Subsonic Flow

    Schairer, Edward T.; Heineck, James T.; Walker, Louise Ann; Kushner, Laura Kathryn; Zilliac, Gregory


    This paper describes simultaneous, synchronized, high-frequency measurements of both unsteady flow in the wake of a tension-cone decelerator in subsonic flow (by PIV) and the unsteady shape of the decelerator (by photogrammetry). The purpose of these measurements was to develop the test techniques necessary to validate numerical methods for computing fluid-structure interactions of flexible decelerators. A critical need for this effort is to map fabric surfaces that have buckled or wrinkled so that code developers can accurately represent them. This paper describes a new photogrammetric technique that performs this measurement. The work was done in support of the Entry, Descent, and Landing discipline within the Supersonics Project of NASA s Fundamental Aeronautics Program.

  13. Domain architecture and oligomerization properties of the paramyxovirus PIV 5 hemagglutinin-neuraminidase (HN) protein.

    Yuan, Ping; Leser, George P; Demeler, Borries; Lamb, Robert A; Jardetzky, Theodore S


    The mechanism by which the paramyxovirus hemagglutinin-neuraminidase (HN) protein couples receptor binding to activation of virus entry remains to be fully understood, but the HN stalk is thought to play an important role in the process. We have characterized ectodomain constructs of the parainfluenza virus 5 HN to understand better the underlying architecture and oligomerization properties that may influence HN functions. The PIV 5 neuraminidase (NA) domain is monomeric whereas the ectodomain forms a well-defined tetramer. The HN stalk also forms tetramers and higher order oligomers with high alpha-helical content. Together, the data indicate that the globular NA domains form weak intersubunit interactions at the end of the HN stalk tetramer, while stabilizing the stalk and overall oligomeric state of the ectodomain. Electron microscopy of the HN ectodomain reveals flexible arrangements of the NA and stalk domains, which may be important for understanding how these two HN domains impact virus entry.

  14. Validation of a numerical FSI simulation of an aortic BMHV by in vitro PIV experiments.

    Annerel, S; Claessens, T; Degroote, J; Segers, P; Vierendeels, J


    In this paper, a validation of a recently developed fluid-structure interaction (FSI) coupling algorithm to simulate numerically the dynamics of an aortic bileaflet mechanical heart valve (BMHV) is performed. This validation is done by comparing the numerical simulation results with in vitro experiments. For the in vitro experiments, the leaflet kinematics and flow fields are obtained via the particle image velocimetry (PIV) technique. Subsequently, the same case is numerically simulated by the coupling algorithm and the resulting leaflet kinematics and flow fields are obtained. Finally, the results are compared, revealing great similarity in leaflet motion and flow fields between the numerical simulation and the experimental test. Therefore, it is concluded that the developed algorithm is able to capture very accurately all the major leaflet kinematics and dynamics and can be used to study and optimize the design of BMHVs.

  15. Measurement of real pulsatile blood flow using X-ray PIV technique with CO2 microbubbles.

    Park, Hanwook; Yeom, Eunseop; Seo, Seung-Jun; Lim, Jae-Hong; Lee, Sang-Joon


    Synchrotron X-ray imaging technique has been used to investigate biofluid flows in a non-destructive manner. This study aims to investigate the feasibility of the X-ray PIV technique with CO2 microbubbles as flow tracer for measurement of pulsatile blood flows under in vivo conditions. The traceability of CO2 microbubbles in a pulsatile flow was demonstrated through in vitro experiment. A rat extracorporeal bypass loop was used by connecting a tube between the abdominal aorta and jugular vein of a rat to obtain hemodynamic information of actual pulsatile blood flows without changing the hemorheological properties. The decrease in image contrast of the surrounding tissue was also investigated for in vivo applications of the proposed technique. This technique could be used to accurately measure whole velocity field information of real pulsatile blood flows and has strong potential for hemodynamic diagnosis of cardiovascular diseases.

  16. PIV measurement of a droplet impact on a thin fluid layer

    Ninomiya, Nao; Iwamoto, Kazuya


    Upon the impact of a droplet onto a thin fluid layer, the fluid is pushed away around the impact point until it reaches a certain radius to go upward to form a thin liquid wall. At the tip of the liquid wall, the circumferential instability creates a several droplets, which is commonly known as "milk crown". The size and the height of the crown and the number of the tip droplets are affected by the conditions of a droplet and of a fluid layer. Presently, the fundamental characteristics of the milk crown have been extensively investigated based on the flow visualization by the high-speed camera. Moreover, the motions of the fluid layer and the liquid film have been measured with the aid of PIV. The result reveals several interesting features of the formation of a milk crown.

  17. Temperature and velocity fields in natural convection by PIV and LIF

    Meyer, Knud Erik; Larsen, Poul Scheel; Westergaard, C. H.


    plate and cooled walls is 1.4×10^10. The flow is turbulent and is similar to some indoor room flows. Combined Particle Image Velocimetry (PIV) and Planar Light Induced Fluorescence (LIF) are used to measure local velocities and temperatures. Data measured in a symmetry plane parallel to a sidewall......Natural convection in a cubical cavity (L = 250 mm) filled with water is created by heating a square plate (0.5 L) centred in the bottom wall and by cooling the sidewalls, while the remaining walls are insulated. The Rayleigh number based on cavity side length and temperature difference between...... are presented in terms of mean velocities and temperature and in terms turbulent quantities including Reynolds fluxes. The flow consists a plume rising above the heated plate into an almost stagnant fluid with a weakly stratified temperature field, as well as thin buoyancy driven boundary layers down...

  18. Effects Of Ignition on Premixed Vortex Rings: A Simultaneous PLIF and PIV Investigation

    Meyer, T. R.; Gord, J. R.; Katta, V. R.; Gogineni, S. P.


    Preliminary studies of reacting, premixed vortex rings have shown that flame propagation is highly sensitive to ignition timing, equivalence ratio, and vortex strength. A variety of divergent phenomena have been observed, such as interior/exterior flame propagation, vortex-induced flame bridging across the jet column, and the formation of unburned pockets. In the current work, planar laser-induced fluorescence (PLIF) of acetone and OH is performed to study the non-reacting and reacting regions, respectively, and particle image velocimetry (PIV) is used to study the effects of reaction on the flow field. The flow field consists of well-characterized vortex rings of premixed methane and air generated at the exit of an axisymmetric nozzle using a solenoid-driven piston. Ignition is initiated at various phases of vortex development and propagation. Results are compared with corresponding numerical simulations from a time-dependent computational fluid dynamics code with chemistry.

  19. In Vivo μPIV Measurements of Blood Flow in Small Vessels of a Rat Model.

    Wei, Timothy; Conner, Nadine; Russell, John; Legac, Paul


    Ongoing research at the University of Wisconsin Medical School is addressing the effects of perfusion of glottal tissue on voice production. Building on the approach developed by Gharib's group at CalTech for embryonic zebra fish, we have modified μPIV to measure flow in capillaries and small blood vessels in a live rat model. In lieu of seeding particles, the DPIV correlation algorithm tracks the motion of red blood cells moving through these vessels. The methodology will be presented along with a video sequence showing measurements made from muscle tissue laid nominally flat on a microscope stage. Challenges of measurements in three-dimensional geometries, i.e. the throat, will be discussed.

  20. Velocity Measurements in Nasal Cavities by Means of Stereoscopic Piv - Preliminary Tests

    Cozzi, Fabio; Felisati, Giovanni; Quadrio, Maurizio


    The prediction of detailed flow patterns in human nasal cavities using computational fluid dynamics (CFD) can provide essential information on the potential relationship between patient-specific geometrical characteristics of the nasal anatomy and health problems, and ultimately led to improved surgery. The complex flow structure and the intricate geometry of the nasal cavities make achieving such goals a challenge for CFD specialists. The need for experimental data to validate and improve the numerical simulations is particularly crucial. To this aim an experimental set-up based on Stereo PIV and a silicon phantom of nasal cavities have been designed and realized at Politecnico di Milano. This work describes the main features and challenges of the set-up along with some preliminary results.

  1. Micro-PIV Study of Supercritical CO2-Water Interactions in Porous Micromodels

    Kazemifar, Farzan; Blois, Gianluca; Christensen, Kenneth T.


    Multiphase flow of immiscible fluids in porous media is encountered in numerous natural systems and engineering applications such as enhanced oil recovery (EOR), and CO2 sequestration among others. Geological sequestration of CO2 in saline aquifers has emerged as a viable option for reducing CO2 emissions, and thus it has been the subject of numerous studies in recent years. A key objective is improving the accuracy of numerical models used for field-scale simulations by incorporation/better representation of the pore-scale flow physics. This necessitates experimental data for developing, testing and validating such models. We have studied drainage and imbibition processes in a homogeneous, two-dimensional porous micromodel with CO2 and water at reservoir-relevant conditions. Microscopic particle image velocimetry (micro-PIV) technique was applied to obtain spatially- and temporally-resolved velocity vector fields in the aqueous phase. The results provide new insight into the flow processes at the pore scale.

  2. PIV Measurements of flow downstream of polyurethane heart valve prosthesis for artificial heart: steady flow experiment

    Kim, J.K.; Sung, J.Y. [Seoul National University Graduate School, Seoul (Korea); Chang, J.K.; Yoo, J.Y.; Min, B.G. [Seoul National University, Seoul (Korea)


    Hemodynamic performance of a polyurethane heart valve prosthesis was evaluated in comparison with that of Bjork-Shiley Monostrut mechanical valve in steady flow representing the systolic peak flow phase. Pressure losses through the valves were obtained from the streamwise pressure distributions downstream of the valves. Unsteady and turbulent flow field distal to the heart valve prostheses were investigated using PIV(Particle Image Velocimetry) which can measure the full-field velocity instantaneously and noninvasively. By examining the velocity and Reynolds shear stress fields downstream of the polyurethane heart valve, it is known that there is a large recirculation region near the valve and high shear stress regions exist at the interface between strong axial jet flows along the wall and vortical flows in the central area. The possibilities of vascular complications, such as the thrombus formation and red blood cell damage, could be predicted from the overall view of the velocity and stress fields. (author). 22 refs., 9 figs., 1 tab.

  3. Stereoscopic PIV and POD applied to the far turbulent axisymmetric jet

    Wähnström, Maja; George, William K.; Meyer, Knud Erik


    Recent experiments on asymptotic high Reynolds number turbulent jet have shown a difference between results from the slice POD applied to the full velocity vector and to the streamwise component of velocity only. In particular, the evolution of the peak in the energy toward azimuthal mode-2...... in the streamwise velocity component decomposition noted in earlier experiments, shifted to mode-1 if all three components of velocity were considered. This is in contrast to what appears to be the case for the jet mixing layer and the axisymmetric wake6 where no such differences were observed. The work reported...... here applies stereoscopic PIV to the far field of the same jet in which the mode-2 phenomenon was first noticed. Indeed azimuthal mode-1 is maximal if all three velocity components are considered, so the new findings are confirmed. This work also addresses a number of outstanding issues from all...

  4. High-Resolution Digital Two-Color PIV for Turbomachinery Flows

    Copenhaver, W.; Gogineni, S.; Goss, L.


    Turbomachinery flows are inherently unsteady. However, steady design methods are currently used to develop turbomachinery, with the lack of basic understanding of unsteady effects being compensated by use of extensive empirical correlations. Conventional laser anemometry provides quantitative evidence of unsteady effects in turbomachinery but is limited in fully exploring this phenomenon. The PIV technique holds great promise for elucidating unsteady flow mechanisms in turbomachinery if obstacles to its application in a transonic turbomachine can be overcome. Implementation involves critical issues such as tracer seeding and optical access for transmitter and receiver. Initially, an 18-in.-dia. axial fan is used to explore these issues. One optical configuration considered is the fiber-optic fanning light sheet in conjunction with high-power pulsed lasers. Instantaneous velocity measurements are made between blades at different spanwise locations.

  5. Optical PIV and LDV Comparisons of Internal Flow Investigations in SHF Impeller

    G. Wuibaut


    Full Text Available The paper presents a comparison between two sets of experimental results in a centrifugal flow pump. The tested impeller is the so-called SHF impeller for which many experimental data have been continuously produced to built databases for CFD code validations with various levels of approximation. Measurements have been performed using optical techniques: 2D particle image velocimetry (PIV technique on an air test model and 2D laser doppler velocimetry (LDV technique on a water model, both for different flow rates. For the present study, results obtained by these optical techniques are compared together in terms of phase averaged velocity and velocity fluctuations inside the impeller flow passage for design flow rate.

  6. Pressure estimation from PIV like data of compressible flows by boundary driven adjoint data assimilation

    Lemke, Mathias; Reiss, Julius; Sesterhenn, Jörn


    Particle image velocimetry (PIV) is one of the major tools to measure velocity fields in experiments. However, other flow properties like density or pressure are often of vital interest, but usually cannot be measured non-intrusively. There are many approaches to overcome this problem, but none is fully satisfactory. Here the computational method of an adjoint based data assimilation for this purpose is discussed. A numerical simulation of a flow is adapted to given velocity data. After successful adaption, previously unknown quantities can be taken from the - necessarily complete - simulation data. The main focus of this work is the efficient implementation of this approach by boundary driven optimisation. Synthetic test cases are presented to allow an assessment of the method.



    The near-wake flow of a NACA0012 airfoils mounted above a water surface were experimentally studied in a wind/wave tunnel. The main objective of this study is to investigate the influence of the free surface on the structure of the airfoil trailing wake. The flow structure was measured with different ride heights between the airfoil and free surface using a Particle Image Velocimetry (PIV) system. The Reynolds number based on the chord length of the airfoil was about 3.5×103. For each experimental condition, large amount of instantaneous velocity fields were captured and ensemble-averaged to get the spatial distributions of mean velocity and mean vorticity, as well as turbulence statistics. The results show that the flow structures of the airfoil wake varies remarkably with the change in the ride height.

  8. DeepPIV: Measuring in situ Biological-Fluid Interactions from the Surface to Benthos

    Katija, K.; Sherman, A.; Graves, D.; Kecy, C. D.; Klimov, D.; Robison, B. H.


    The midwater region of the ocean (below the euphotic zone and above the benthos) is one of the largest ecosystems on our planet, yet it remains one of the least explored. Little known marine organisms that inhabit midwater have developed strategies for swimming and feeding that ultimately contributes to their evolutionary success, and may inspire engineering solutions for societally relevant challenges. Fluid mechanics governs the interactions that midwater organisms have with their physical environment, but limited access to midwater depths and lack of non-invasive methods to measure in situ small-scale fluid motions prevent these interactions from being better understood. Significant advances in underwater vehicle technologies have only recently improved access to midwater. Unfortunately, in situ small-scale fluid mechanics measurement methods are still lacking in the oceanographic community. Here we present DeepPIV, an instrumentation package that can be affixed to remotely operated underwater vehicles that quantifies small-scale fluid motions from the surface of the ocean down to 4000 m depths. Utilizing ambient, suspended particulate in the coastal regions of Monterey Bay, fluid-structure interactions are evaluated on a range of marine organisms in midwater. Initial science targets include larvaceans, biological equivalents of flapping flexible foils, that create mucus houses to filter food. Little is known about the structure of these mucus houses and the function they play in selectively filtering particles, and these dynamics can serve as particle-mucus models for human health. Using DeepPIV, we reveal the complex structures and flows generated within larvacean mucus houses, and elucidate how these structures function.

  9. Stereoscopic multi-planar PIV measurements of in-cylinder tumbling flow

    Buecker, I.; Karhoff, D.C.; Klaas, M.; Schroeder, W. [RWTH Aachen University, Institute of Aerodynamics, Aachen (Germany)


    The non-reacting flow field within the combustion chamber of a motored direct-injection spark-ignition engine with tumble intake port is measured. The three-dimensionality of the flow necessitates the measurement of all three velocity components via stereoscopic particle-image velocimetry in multiple planes. Phase-locked stereoscopic PIV is applied at 15 crank angles during the intake and compression strokes, showing the temporal evolution of the flow field. The flow fields are obtained within a set of 14 axial planes, covering nearly the complete cylinder volume. The stereoscopic PIV setup applied to engine in-cylinder flow and the arising problems and solutions are discussed in detail. The three-dimensional flow field is reconstructed and analyzed using vortex criteria. The tumble vortex is the dominant flow structure, and this vortex varies significantly regarding shape, strength, and position throughout the two strokes. The tumble vortex center moves clockwise through the combustion chamber. At first, the tumble has a c-shape which turns into an almost straight tube at the end of the compression. Small-scale structures are analyzed by the distribution of the turbulent kinetic energy. It is evident that the symmetry plane only represents the 3D flow field after 100 CAD. For earlier crank angles, both kinetic energy (KE) and turbulent kinetic energy (TKE) in the combustion chamber are well below the KE and TKE in the symmetry plane. This should be taken into account when the injection and breakup of the three-dimensional fuel jet are studied. The mean kinetic energy is conserved until late compression by the tumble motion. This conservation ensures through the excited air motion an enhancement of the initial air-fuel mixture which is of interest for direct-injection gasoline engines. (orig.)

  10. Investigation of an IC Engine Intake Flow Based on Highly Resolved LES and PIV

    Buhl Stefan


    Full Text Available To reduce emissions and fuel consumption, the current generation of gasoline engines uses technologies such as direct injection, downsizing and supercharging. All of them require a strong vortical in-cylinder charge motion, usually described as “tumble”, to improve fuel-air mixing and enhance flame propagation. The tumble development strongly depends on the flow field during the intake stroke. This flow field is dominated by the intake jet, which has to be captured well in the simulation. This work investigates the intake jet on a steady-state flow bench, especially in the vicinity of the intake valve. At first, the general flow dynamics of the intake jet for three different valve lifts and three different mass flows were investigated experimentally. For the smallest valve lift (3 mm, flow-field measurements using Particle Image Velocimetry (PIV show that the orientation of the intake jet significantly depends on the air flow rate, attaching to the pent roof for low flow rates. This phenomenon is less pronounced for higher valve lifts. An intermediate valve lift and flow rate were chosen for further investigations by scale-resolving simulations. Three different meshes (coarse, medium and fine and two turbulence models (Sigma and Detached Eddy Simulation-Shear Stress Transport (DES-SST are applied to consider their effect on the numerical results. An ad-hoc post-processing methodology based on the ensemble-averaged velocity field is presented capturing the jet centerline’s mean velocity and velocity fluctuations as well as its orientation, curvature and penetration depth. The simulation results are compared to each other as well as to measurements by PIV.

  11. A wavelet-based intermittency detection technique from PIV investigations in transitional boundary layers

    Simoni, Daniele; Lengani, Davide; Guida, Roberto


    The transition process of the boundary layer growing over a flat plate with pressure gradient simulating the suction side of a low-pressure turbine blade and elevated free-stream turbulence intensity level has been analyzed by means of PIV and hot-wire measurements. A detailed view of the instantaneous flow field in the wall-normal plane highlights the physics characterizing the complex process leading to the formation of large-scale coherent structures during breaking down of the ordered motion of the flow, thus generating randomized oscillations (i.e., turbulent spots). This analysis gives the basis for the development of a new procedure aimed at determining the intermittency function describing (statistically) the transition process. To this end, a wavelet-based method has been employed for the identification of the large-scale structures created during the transition process. Successively, a probability density function of these events has been defined so that an intermittency function is deduced. This latter strictly corresponds to the intermittency function of the transitional flow computed trough a classic procedure based on hot-wire data. The agreement between the two procedures in the intermittency shape and spot production rate proves the capability of the method in providing the statistical representation of the transition process. The main advantages of the procedure here proposed concern with its applicability to PIV data; it does not require a threshold level to discriminate first- and/or second-order time-derivative of hot-wire time traces (that makes the method not influenced by the operator); and it provides a clear evidence of the connection between the flow physics and the statistical representation of transition based on theory of turbulent spot propagation.

  12. PIV Measurements of Flows around the Wind Turbines with a Flanged-Diffuser Shroud

    Kazuhiko Toshimitsu; Koutarou Nishikawa; Wataru Haruki; Shinichi Oono; Manabu Takao; Yuji Ohya


    The wind turbines with a flanged-diffuser shroud -so called "wind lens turbine"- are developed as one of high performance wind turbines by Ohya et al. In order to investigate the flow characteristics and flow acceleration, the paper presents the flow velocity measurements of a long-type and a compact-type wind turbines with a flanged-diffuser shroud by particle image velocimetry. In the case of the long type wind turbine, the velocity vec-tors of the inner flow field of the diffuser for turbine blades rotating and no blades rotating are presented at Rey-nolds number, 0.9x105. Furthermore the flow fields between with and without rotating are compared. Through the PIV measurement results, one can realize that the turbine blades rotating affects as suppress the disturbance and the flow separation near the inner wall of the diffuser. The time average velocity vectors are made on the av-erage of the instantaneous velocity data. There are two large vortices in downstream region of the diffuser. One vortex behind the flange acts as suck in wind to the diffuser and raise the inlet flow velocity. Another large vortex appears in downstream. It might be act as blockage vortex of main flow. The large blockage vortex is not clear in the instantaneous velocity vectors, however it exists clearly in the time average flow field. The flow field around the wind turbine with a compact-type flanged-diffuser shroud is also investigated. The flow pattern behind the flange of the compact-type turbine is the same as the long-type one. It means that the effect of flow acceleration is caused by the unsteady vortices behind the flange. The comparison with CFD and PIV results of meridional time-average streamlines after the compact-type diffuser is also presented.

  13. Image pre-processing method for near-wall PIV measurements over moving curved interfaces

    Jia, L. C.; Zhu, Y. D.; Jia, Y. X.; Yuan, H. J.; Lee, C. B.


    PIV measurements near a moving interface are always difficult. This paper presents a PIV image pre-processing method that returns high spatial resolution velocity profiles near the interface. Instead of re-shaping or re-orientating the interrogation windows, interface tracking and an image transformation are used to stretch the particle image strips near a curved interface into rectangles. Then the adaptive structured interrogation windows can be arranged at specified distances from the interface. Synthetic particles are also added into the solid region to minimize interfacial effects and to restrict particles on both sides of the interface. Since a high spatial resolution is only required in high velocity gradient region, adaptive meshing and stretching of the image strips in the normal direction is used to improve the cross-correlation signal-to-noise ratio (SN) by reducing the velocity difference and the particle image distortion within the interrogation window. A two dimensional Gaussian fit is used to compensate for the effects of stretching particle images. The working hypothesis is that fluid motion near the interface is ‘quasi-tangential flow’, which is reasonable in most fluid-structure interaction scenarios. The method was validated against the window deformation iterative multi-grid scheme (WIDIM) using synthetic image pairs with different velocity profiles. The method was tested for boundary layer measurements of a supersonic turbulent boundary layer on a flat plate, near a rotating blade and near a flexible flapping flag. This image pre-processing method provides higher spatial resolution than conventional WIDIM and good robustness for measuring velocity profiles near moving interfaces.

  14. PIV and LDA measurements of the wake behind a wind turbine model

    Naumov, I. V.; Mikkelsen, R. F.; Okulov, V. L.; Sørensen, J. N.


    In the present work we review the results of a series of measurements of the flow behind a model scale of a horizontal axis wind turbine rotor carried out at the water flume at Technical University of Denmark (DTU). The rotor is three-bladed and designed using Glauert theory for tip speed ratio λ =5 with a constant design lift coefficient along the span, CLdesign= 0.8. The measurements include dye visualization, Particle Image Velocimetry and Laser Doppler Anemometry. The wake instability has been studied in the range λ =3 - 9 at different cross-sections from the very near wake up to 10 rotor diameters downstream from the rotor. The initial flume flow was subject to a very low turbulence level with a uniform velocity profile, limiting the influence of external disturbances on the development of the inherent vortex instability. Using PIV measurements and visualizations, special attention was paid to detect and categorize different types of wake instabilities and the development of the flow in the near and the far wake. In parallel to PIV, LDA measurements provided data for various rotor regimes, revealing the existence of three main regular frequencies governing the development of different processes and instabilities in the rotor wake. In the far wake a constant frequency corresponding to the Strouhal number was found for the long-scale instabilities. This Strouhal number is in good agreement with the well-known constant that usually characterizes the oscillation in wakes behind bluff bodies. From associated visualizations and reconstructions of the flow field, it was found that the dynamics of the far wake is associated with the precession (rotation) of a helical vortex core. The data indicate that Strouhal number of this precession is independent of the rotor angular speed.

  15. Quantification and correction of the error due to limited PIV resolution on the accuracy of non-intrusive spatial pressure measurement using a DNS channel flow database

    Liu, Xiaofeng; Siddle-Mitchell, Seth


    The effect of the subgrid-scale (SGS) stress due to limited PIV resolution on pressure measurement accuracy is quantified using data from a direct numerical simulation database of turbulent channel flow (JHTDB). A series of 2000 consecutive realizations of sample block data with 512x512x49 grid nodal points were selected and spatially filtered with a coarse 17x17x17 and a fine 5x5x5 box averaging, respectively, giving rise to corresponding PIV resolutions of roughly 62.6 and 18.4 times of the viscous length scale. Comparison of the reconstructed pressure at different levels of pressure gradient approximation with the filtered pressure shows that the neglect of the viscous term leads to a small but noticeable change in the reconstructed pressure, especially in regions near the channel walls. As a contrast, the neglect of the SGS stress results in a more significant increase in both the bias and the random errors, indicating the SGS term must be accounted for in PIV pressure measurement. Correction using similarity SGS modeling reduces the random error due to the omission of SGS stress from 114.5% of the filtered pressure r.m.s. fluctuation to 89.1% for the coarse PIV resolution, and from 66.5% to 35.9% for the fine PIV resolution, respectively, confirming the benefit of the error compensation method and the positive influence of increasing PIV resolution on pressure measurement accuracy improvement.


    ZHONG Qiang; LI Dan-xun; CHEN Qi-gang; WANG Xing-kui


    The shading method is a simple but effective way of reducing image blooming in the measurement of open channel flows with the Particle Image Veloeimetry (PIV).The current paper proposes a simplified analytical model for light attenuation using this method.The model is verified against experimental data,and the influence of several parameters is illustrated numerically.The possible adverse effect due to the light attenuation is shown to be limited when the parameters in the shading method are in an adequate range,as shown by processing standard images of Case B in PIV Challenge 03.A simple criterion for setting the shade in experiment is given for controlling the errors caused by the shading technique within an acceptable range.

  17. On image pre-processing for PIV of single- and two-phase flows over reflecting objects

    Deen, Niels G.; Willems, Paul; Sint Annaland, Martin van; Kuipers, J.A.M.; Lammertink, Rob G.H.; Kemperman, Antoine J.B.; Wessling, Matthias; Meer, Walter G.J. van der [University of Twente, Faculty of Science and Technology, Institute of Mechanics, Processes and Control Twente (IMPACT), Enschede (Netherlands)


    A novel image pre-processing scheme for PIV of single- and two-phase flows over reflecting objects which does not require the use of additional hardware is discussed. The approach for single-phase flow consists of image normalization and intensity stretching followed by background subtraction. For two-phase flow, an additional masking step is added after the background subtraction. The effectiveness of the pre-processing scheme is shown for two examples: PIV of single-phase flow in spacer-filled channels and two-phase flow in these channels. The pre-processing scheme increased the displacement peak detectability significantly and produced high quality vector fields, without the use of additional hardware. (orig.)

  18. 粒子图像测速(PIV)技术的发展%The Development of Particle Image Velocimetry

    冯旺聪; 郑士琴



  19. In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system.

    Lima, Rui; Wada, Shigeo; Tanaka, Shuji; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, Takami


    Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 microm wide, 45 microm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability

  20. Time-resolved PIV technique for high temporal resolution measurement of mechanical prosthetic aortic valve fluid dynamics.

    Kaminsky, R; Morbiducci, U; Rossi, M; Scalise, L; Verdonck, P; Grigioni, M


    Prosthetic heart valves (PHVs) have been used to replace diseased native valves for more than five decades. Among these, mechanical PHVs are the most frequently implanted. Unfortunately, these devices still do not achieve ideal behavior and lead to many complications, many of which are related to fluid mechanics. The fluid dynamics of mechanical PHVs are particularly complex and the fine-scale characteristics of such flows call for very accurate experimental techniques. Adequate temporal resolution can be reached by applying time-resolved PIV, a high-resolution dynamic technique which is able to capture detailed chronological changes in the velocity field. The aim of this experimental study is to investigate the evolution of the flow field in a detailed time domain of a commercial bileaflet PHV in a mock-loop mimicking unsteady conditions, by means of time-resolved 2D Particle Image Velocimetry (PIV). The investigated flow field corresponded to the region immediately downstream of the valve plane. Spatial resolution as in "standard" PIV analysis of prosthetic valve fluid dynamics was used. The combination of a Nd:YLF high-repetition-rate double-cavity laser with a high frame rate CMOS camera allowed a detailed, highly temporally resolved acquisition (up to 10000 fps depending on the resolution) of the flow downstream of the PHV. Features that were observed include the non-homogeneity and unsteadiness of the phenomenon and the presence of large-scale vortices within the field, especially in the wake of the valve leaflets. Furthermore, we observed that highly temporally cycle-resolved analysis allowed the different behaviors exhibited by the bileaflet valve at closure to be captured in different acquired cardiac cycles. By accurately capturing hemodynamically relevant time scales of motion, time-resolved PIV characterization can realistically be expected to help designers in improving PHV performance and in furnishing comprehensive validation with experimental data

  1. On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments

    Scarano, Fulvio; Ghaemi, Sina; Caridi, Giuseppe Carlo Alp; Bosbach, Johannes; Dierksheide, Uwe; Sciacchitano, Andrea


    The flow-tracing fidelity of sub-millimetre diameter helium-filled soap bubbles (HFSB) for low-speed aerodynamics is studied. The main interest of using HFSB in relation to micron-size droplets is the large amount of scattered light, enabling larger-scale three-dimensional experiments by tomographic PIV. The assessment of aerodynamic behaviour closely follows the method proposed in the early work of Kerho and Bragg (Exp Fluids 50:929-948, 1994) who evaluated the tracer trajectories around the stagnation region at the leading edge of an airfoil. The conclusions of the latter investigation differ from the present work, which concludes sub-millimetre HFSB do represent a valid alternative for quantitative velocimetry in wind tunnel aerodynamic experiments. The flow stagnating ahead of a circular cylinder of 25 mm diameter is considered at speeds up to 30 m/s. The tracers are injected in the free-stream and high-speed PIV, and PTV are used to obtain the velocity field distribution. A qualitative assessment based on streamlines is followed by acceleration and slip velocity measurements using PIV experiments with fog droplets as a term of reference. The tracing fidelity is controlled by the flow rates of helium, liquid soap and air in HFSB production. A characteristic time response, defined as the ratio of slip velocity and the fluid acceleration, is obtained. The feasibility of performing time-resolved tomographic PIV measurements over large volumes in aerodynamic wind tunnels is also studied. The flow past a 5-cm-diameter cylinder is measured over a volume of 20 × 20 × 12 cm3 at a rate of 2 kHz. The achieved seeding density of <0.01 ppp enables resolving the Kármán vortices, whereas turbulent sub-structures cannot be captured.

  2. 50 kHz PIV of a Swept-Ramp Shock-Wave Boundary-Layer Interaction at Mach 2

    Vanstone, Leon; Musta, Mustafa Nail; Seckin, Serdar; Saleem, Mohammad; Clemens, Noel


    The interaction from a 30° sweep, 22.5° compression ramp in a Mach 2 flow is examined using wide-field 5Hz and 50 kHz PIV. The high-speed PIV is fast enough to resolve the large-scale unsteady motions of the SWBLI and can be band-pass filtered to investigate the driving mechanisms of unsteadiness and the widefield PIV allows comparisons with mean flow-fields. Preliminary investigation looked at three distinct frequency bands: 10-50 kHz (0.025-0.25 U∞ /δ99), 1-10 kHz (0.025-0.25 U∞ /δ99), and 0-1 kHz (0-0.025 U∞ /δ99). The unsteadiness associated with 10-50 kHz shows no correlation with the upstream boundary layer and accounts for 40% of the amplitude. The unsteadiness associated with 1-10 kHz is correlated with the upstream boundary-layer and also accounts for 40% of unsteadiness. This frequency is similar to those of boundary-layer superstructures. The unsteadiness associated with 0-1 kHz shows the strongest correlation with the upstream boundary-layer but accounts for only 20% of the amplitude. Clearly a range of unsteadiness mechanisms are present, with significant amplitude associated with higher frequencies. Future work will focus on expanding these findings with surface pressure and additional PIV. This work is sponsored by the AFOSR under Grant FA9550-14-1-0167 with Ivett Leyva as the program manager. This source of support is gratefully acknowledged. Further, Mustafa Musta thanks the Scientific and Technological research Council of Turkey.

  3. Optimization of the volume reconstruction for classical Tomo-PIV algorithms (MART, BIMART and SMART): synthetic and experimental studies

    Thomas, L.; Tremblais, B.; David, L.


    Optimization of multiplicative algebraic reconstruction technique (MART), simultaneous MART and block iterative MART reconstruction techniques was carried out on synthetic and experimental data. Different criteria were defined to improve the preprocessing of the initial images. Knowledge of how each reconstruction parameter influences the quality of particle volume reconstruction and computing time is the key in Tomo-PIV. These criteria were applied to a real case, a jet in cross flow, and were validated.

  4. Tollip-induced down-regulation of MARCH1.

    Bourgeois-Daigneault, Marie-Claude; Pezeshki, Abdul Mohammad; Galbas, Tristan; Houde, Mathieu; Baril, Martin; Früh, Klaus; Amrani, Abdelaziz; Ishido, Satoshi; Lamarre, Daniel; Thibodeau, Jacques


    In addition to their classical antigen presenting functions, MHC class II molecules potentiate the TLR-triggered production of pro-inflammatory cytokines. Here, we have addressed the effect of Tollip and MARCH1 on the regulation of MHC II trafficking and TLR signaling. Our results show that MARCH1-deficient mice splenocytes are impaired in their capacity to produce pro-inflammatory cytokines in response to poly(I:C) and that TLR3 and MHC II molecules interact in the endocytic pathway. Knocking down Tollip expression in human CIITA(+) HeLa cells increased expression of HLA-DR but reduced the proportion of MHC II molecules associated with the CLIP peptide. Truncation of the HLA-DR cytoplasmic tails abrogated the effect of Tollip on MHC class II expression. While overexpression of Tollip did not affect HLA-DR levels, it antagonized the function of co-transfected MARCH1. We found that Tollip strongly reduced MARCH1 protein levels and that the two molecules appear to compete for binding to MHC II molecules. Altogether, our results demonstrate that Tollip regulates MHC class II trafficking and that MARCH1 may represent a new Tollip target.

  5. Performances of motion tracking enhanced Tomo-PIV on turbulent shear flows.

    Novara, Matteo; Scarano, Fulvio

    The motion tracking enhancement technique (MTE) is a recently introduced method to improve the accuracy of tomographic PIV measurements at seeding density higher than currently practiced. The working principle is based on the fact that the particle field and its projections are correlated between the two exposures. Therefore, information from subsequent exposures can be shared within the tomographic reconstruction process of a single object, which largely reduces the energy lost into ghost particles. The study follows a previous work based on synthetic particle images, showing that the MTE technique has an effect similar to that of increasing the number of cameras. In the present analysis, MTE is applied to Tomographic PIV data from two time-resolved experiments on turbulent shear flows: a round jet at Re = 5,000 (facq = 1,000 Hz) and a turbulent boundary layer at the trailing edge of an airfoil (Rec = 370,000) measured at 12,000 Hz. The application of MTE is extended to the case of more than two recordings. The performance is assessed comparing the results from a lowered number of cameras with respect to the full tomographic imaging system. The analysis of the jet flow agrees with the findings of numerical simulations provided the results are scaled taking into account the concept of MTE efficiency based on the volume fraction where ghost-pairs (Elsinga et al. 2010a) are produced. When a large fraction of fluid has uniform motion (stagnant fluid surrounding the jet), only a moderate reduction in ghost intensity is expected by MTE. Nevertheless, a visible recovery of reconstruction quality is observed for the 3-cameras system when MTE is applied making use of 3 recordings. In the turbulent boundary layer, the objective is set to increase the seeding density beyond current practice, and the experiments are performed at approximately 200,000 particles/megapixel. The measurement robustness is monitored with the signal-to-noise ratio S/N for the cross

  6. Performances of motion tracking enhanced Tomo-PIV on turbulent shear flows

    Novara, Matteo; Scarano, Fulvio


    The motion tracking enhancement technique (MTE) is a recently introduced method to improve the accuracy of tomographic PIV measurements at seeding density higher than currently practiced. The working principle is based on the fact that the particle field and its projections are correlated between the two exposures. Therefore, information from subsequent exposures can be shared within the tomographic reconstruction process of a single object, which largely reduces the energy lost into ghost particles. The study follows a previous work based on synthetic particle images, showing that the MTE technique has an effect similar to that of increasing the number of cameras. In the present analysis, MTE is applied to Tomographic PIV data from two time-resolved experiments on turbulent shear flows: a round jet at Re = 5,000 ( f acq = 1,000 Hz) and a turbulent boundary layer at the trailing edge of an airfoil ( Re c = 370,000) measured at 12,000 Hz. The application of MTE is extended to the case of more than two recordings. The performance is assessed comparing the results from a lowered number of cameras with respect to the full tomographic imaging system. The analysis of the jet flow agrees with the findings of numerical simulations provided the results are scaled taking into account the concept of MTE efficiency based on the volume fraction where ghost- pairs (Elsinga et al. 2010a) are produced. When a large fraction of fluid has uniform motion (stagnant fluid surrounding the jet), only a moderate reduction in ghost intensity is expected by MTE. Nevertheless, a visible recovery of reconstruction quality is observed for the 3-cameras system when MTE is applied making use of 3 recordings. In the turbulent boundary layer, the objective is set to increase the seeding density beyond current practice, and the experiments are performed at approximately 200,000 particles/megapixel. The measurement robustness is monitored with the signal-to-noise ratio S/N for the cross

  7. PIV Visualization of Bubble Induced Flow Circulation in 2-D Rectangular Pool for Ex-Vessel Debris Bed Coolability

    Han, Teayang; Kim, Eunho; Park, Hyun Sun; Moriyama, Kiyofumi [POSTECH, Pohang (Korea, Republic of)


    The previous research works demonstrated the debris bed formation on the flooded cavity floor in experiments. Even in the cases the core melt is once solidified, the debris bed can be re-melted due to the decay heat. If the debris bed is not cooled enough by the coolant, the re-melted debris bed will react with the concrete base mat. This situation is called the molten core-concrete interaction (MCCI) which threatens the integrity of the containment by generated gases which pressurize the containment. Therefore securing the long term coolability of the debris bed in the cavity is crucial. According to the previous research works, the natural convection driven by the rising bubbles affects the coolability and the formation of the debris bed. Therefore, clarification of the natural convection characteristics in and around the debris bed is important for evaluation of the coolability of the debris bed. In this study, two-phase flow around the debris bed in a 2D slice geometry is visualized by PIV method to obtain the velocity map of the flow. The DAVINCI-PIV was developed to investigate the flow around the debris bed. In order to simulate the boiling phenomena induced by the decay heat of the debris bed, the air was injected separately by the air chamber system which consists of the 14 air-flowmeters. The circulation flow developed by the rising bubbles was visualized by PIV method.

  8. Time-resolved X-ray PIV technique for diagnosing opaque biofluid flow with insufficient X-ray fluxes.

    Jung, Sung Yong; Park, Han Wook; Kim, Bo Heum; Lee, Sang Joon


    X-ray imaging is used to visualize the biofluid flow phenomena in a nondestructive manner. A technique currently used for quantitative visualization is X-ray particle image velocimetry (PIV). Although this technique provides a high spatial resolution (less than 10 µm), significant hemodynamic parameters are difficult to obtain under actual physiological conditions because of the limited temporal resolution of the technique, which in turn is due to the relatively long exposure time (~10 ms) involved in X-ray imaging. This study combines an image intensifier with a high-speed camera to reduce exposure time, thereby improving temporal resolution. The image intensifier amplifies light flux by emitting secondary electrons in the micro-channel plate. The increased incident light flux greatly reduces the exposure time (below 200 µs). The proposed X-ray PIV system was applied to high-speed blood flows in a tube, and the velocity field information was successfully obtained. The time-resolved X-ray PIV system can be employed to investigate blood flows at beamlines with insufficient X-ray fluxes under specific physiological conditions. This method facilitates understanding of the basic hemodynamic characteristics and pathological mechanism of cardiovascular diseases.

  9. Cellular-level near-wall unsteadiness of high-hematocrit erythrocyte flow using confocal {mu}PIV

    Patrick, Michael J. [Carnegie Mellon University, Molecular Biosensor and Imaging Center (MBIC), Pittsburgh, PA (United States); Chen, Chia-Yuan; Dur, Onur; Pekkan, Kerem [Carnegie Mellon University, Department of Biomedical and Mechanical Engineering, Pittsburgh, PA (United States); Frakes, David H. [Arizona State University, School of Biological and Health Systems Engineering and School of Electrical, Computer, and Energy Engineering, Tempe, AZ (United States)


    In hemodynamics, the inherent intermittency of two-phase cellular-level flow has received little attention. Unsteadiness is reported and quantified for the first time in the literature using a combination of fluorescent dye labeling, time-resolved scanning confocal microscopy, and micro-particle image velocimetry ({mu}PIV). The near-wall red blood cell (RBC) motion of physiologic high-hematocrit blood in a rectangular microchannel was investigated under pressure-driven flow. Intermittent flow was associated with (1) the stretching of RBCs as they passed through RBC clusters with twisting motions; (2) external flow through local obstacles; and (3) transitionary rouleaux formations. Velocity profiles are presented for these cases. Unsteady flow clustered in local regions. Extra-cellular fluid flow generated by individual RBCs was examined using submicron fluorescent microspheres. The capabilities of confocal {mu}PIV post-processing were verified using synthetic raw PIV data for validation. Cellular interactions and oscillating velocity profiles are presented, and 3D data are made available for computational model validation. (orig.)

  10. A general approach for time-supersampling of 3D-PIV data by the vortex-in-cell method

    Scarano, Fulvio; Schneiders, Jan; Dwight, Richard; Aerospace Engineering/Aerodynamics Team


    Advancements of tomographic PIV [1] have led into 3D time-resolved experiments to study the dynamical evolution of 3D turbulent flows [2]. The known bottleneck of Tomo-PIV is the high laser power required to illuminate large volumes in airflows, which becomes critical beyond 10 kHz. Time-super-sampling is an approach to reduce the sampling rate, proven for frozen turbulence where the advection model yields a significant increase of temporal resolution [3]. Instead, in separated flows, the advection principle yields unacceptable distortions. The use of Navier-Stokes numerical calculations with the vortex-in-cell (VIC) method is proposed herein. The assumption is made of inviscid incompressible flow [4]. The spatial-resolution of the data is exploited to increase the temporal resolution. The dynamical evolution of the vorticity and velocity field between subsequent snapshots in the 3D domain is numerically evaluated. The verification with fully time resolved data of a circular jet indicates a substantial increase of temporal resolution. Interestingly, data sampled below the Nyquist limit could be reconstructed faithfully, indicating the potential of VIC in alleviating requirements on PIV measurement rate. Work supported by the European Research Council grant 202887.

  11. Calculation of the weighting function and determination of the depth of correlation in micro-PIV from experimental particle images

    Hein, M.; Wieneke, B.; Seemann, R.


    Micro-particle image velocimetry (µPIV) uses volume-illumination and imaging of particles through a single microscope objective. Displacement fields are obtained by image correlation and depend on all imaged particles, including defocused particles. The measured in-plane displacement is a weighted spatial average of the true displacement, with a weighting function W(z) that depends on the optical system and flow-gradients. The characteristic width of the weighting function W(z) is also referred to as depth of correlation (DOC) and is a measure up to which distance from the focal plane particles influence the measurement, which is crucial for the interpretation of measured flow fields. We present procedures to determine the W(z) from which the DOC can be derived and to directly determine the DOC from PIV double images, generated from experimentally recorded particle images. Both procedures provide comparable DOC results. Our approach allows determination of the DOC and W(z)as a function of out of plane gradients, optical setup parameters and PIV-analysis parameters. Experimental results for different objectives and particle sizes are discussed, revealing substantial deviations from theoretical predictions for high NA air-objectives. Moreover, using the determined weighting function W(z), the correction of measured flow profiles for errors introduced by the spatial averaging is demonstrated.

  12. Development and evaluation of gappy-POD as a data reconstruction technique for noisy PIV measurements in gas turbine combustors

    Saini, Pankaj; Arndt, Christoph M.; Steinberg, Adam M.


    Low signal-to-noise in particle image velocimetry (PIV) measurements in systems such as high pressure gas turbine combustors can result in significant data gaps that negatively affect subsequent analysis. Here, gappy proper orthogonal decomposition (GPOD) is evaluated as a method of filling such missing data. Four GPOD methods are studied, including a new method that utilizes a median filter (MF) to adaptively select whether a local missing data point is updated after each iteration. These methods also are compared against local Kriging interpolation. The GPOD methods are tested using PIV data without missing vectors that were obtained in atmospheric pressure swirl flames. Parameters studied include the turbulence intensity, amount of missing data, and the amount of noise in the valid data. Two criteria to check for GPOD convergence also were investigated. The MF method filled in the missing data with the lowest error across all parameters tested, with approximately one-third the computational cost of Kriging. Furthermore, the accuracy of MF GPOD was relatively insensitive to the quality of the convergence criterion. Therefore, compared to the three other GPOD methods and Kriging interpolation, the MF GPOD method is an effective method for filling missing data in PIV measurements in the studied gas turbine combustor flows.

  13. Three-dimensional temporally resolved measurements of turbulence-flame interactions using orthogonal-plane cinema-stereoscopic PIV

    Steinberg, Adam Michael; Driscoll, James F. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, MI (United States); Ceccio, Steven L. [University of Michigan, Department of Mechanical Engineering, Ann Arbor, MI (United States)


    A new orthogonal-plane cinema-stereoscopic particle image velocimetry (OPCS-PIV) diagnostic has been used to measure the dynamics of three-dimensional turbulence-flame interactions. The diagnostic employed two orthogonal PIV planes, with one aligned perpendicular and one aligned parallel to the streamwise flow direction. In the plane normal to the flow, temporally resolved slices of the nine-component velocity gradient tensor were determined using Taylor's hypothesis. Volumetric reconstruction of the 3D turbulence was performed using these slices. The PIV plane parallel to the streamwise flow direction was then used to measure the evolution of the turbulence; the path and strength of 3D turbulent structures as they interacted with the flame were determined from their image in this second plane. Structures of both vorticity and strain-rate magnitude were extracted from the flow. The geometry of these structures agreed well with predictions from direct numerical simulations. The interaction of turbulent structures with the flame also was observed. In three dimensions, these interactions had complex geometries that could not be reflected in either planar measurements or simple flame-vortex configurations. (orig.)

  14. PIV Validation of 3D Multicomponent Model for Cold Spray Within Nitrogen and Helium Supersonic Flow Field

    Faizan-Ur-Rab, M.; Zahiri, S. H.; Masood, S. H.; Jahedi, M.; Nagarajah, R.


    This study presents the validation of a developed three-dimensional multicomponent model for cold spray process using two particle image velocimetry (PIV) experiments. The k- ɛ type 3D model developed for spherical titanium particles was validated with the measured titanium particle velocity within a nitrogen and helium supersonic jet. The 3D model predicted lower values of particle velocity than the PIV experimental study that used irregularly shaped titanium particles. The results of the 3D model were consistent with the PIV experiment that used spherical titanium powder. The 3D model simulation of particle velocity within the helium and nitrogen jet was coupled with an estimation of titanium particle temperature. This was achieved with the consideration of the fact that cold spray particle temperature is difficult and expensive to measure due to considerably lower temperature of particles than thermal spray. The model predicted an interesting pattern of particle size distribution with respect to the location of impact with a concentration of finer particles close to the jet center. It is believed that the 3D model outcomes for particle velocity, temperature and location could be a useful tool to optimize system design, deposition process and mechanical properties of the additively manufactured cold spray structures.

  15. Evaluating Large-Eddy Simulation (LES and High-Speed Particle Image Velocimetry (PIV with Phase-Invariant Proper Orthogonal Decomposition (POD

    Abraham P.


    Full Text Available This study is part of a program to understand the stochastic variations in IC engine flows; in particular, it is a comparison of measured (PIV and computed (LES velocity from multiple cycles of the same motored engine. Comparison procedures included traditional RANS (Reynolds Averaged Navier-Stokes decomposition (ensemble-averaged and RMS (Root Mean Square velocity, phase-dependent, and phase- invariant POD. Phase-dependent POD was performed on the PIV and LES samples separately and on the combined samples, thus creating separate or a single POD mode sets, respectively. The phase- invariant POD was performed both on normalized snapshots and on snapshots where the original energy was conserved. Initial comparisons of the mass-specific kinetic energies of the ensemble average and RMS velocities revealed that the PIV and LES data sets differed significantly during most of the intake stroke. This discrepancy was quantifiedfirst by comparing the relevance indices calculated between ensemble average velocity fields and, second, using phase-dependent POD, which quantified cycle-to-cycle flow variations of the RANS average and turbulence. Phase-dependent POD was applied separately to the PIV and LES data sets during the intake stroke (76° ATDCE, After Top Dead Center Exhaust, where the intake-valve jet is strong and the PIV and LES data were earlier found to be significantly different. The cyclic variability of the LES ensemble average was estimated to be significantly higher than that of the PIV data set. POD was also applied to the combined sample of LES and PIV snapshots for quantitative comparison creating a single set of modes, so that comparison could be made with POD coefficients alone. Example comparisons were made at again for data at 76° and also 330° ATDCE, which is a viable spark timing in a fired engine. The results at 76° ATDCE were similar to those obtained with the POD analysis of the separate samples. At 330° ATDCE, the PIV

  16. PIV-based investigation of the skin friction of the flow over random fibrous media

    Mirbod, Parisa; Gheisari, Reza


    Finite Reynolds number (Reflow over fibrous medium inside a rectangular duct was studied using a planar 2D PIV system. Three different fibrous materials with different porosities were used. Fibrous material lined the bottom wall of the duct along the length of the duct. The flow regime for all tests was laminar, and measurements were all done when the flow reached a steady state. Error and uncertainty sources in the experiments were also discussed. Shear rates were estimated at the surface of the fibrous media. As a conclusion to this study skin friction factor were calculated at the interface of all fibrous media at selected Reynolds number. Then using power function, curve fits with the Cf = a/Re form were found which could closely correlate skin friction and Reynolds number. To weaken the effect of near-wall errors in estimated shear rates and consequently skin friction, an average of shear rate estimation in a layer with thickness of 5 mm was calculated which was used to calculate an average skin friction. Correlations of average skin friction with average Reynolds number were also presented.

  17. Ghost Particle Velocimetry implementation in millimeters devices and comparison with μPIV

    Riccomi, Marco; Alberini, Federico; Brunazzi, Elisabetta; Vigolo, Daniele


    Micro/milli-fluidic devices are becoming an important reference for several disciplines and are quickly increasing their applications in scientific, as well as industrial, environment. As a consequence, the development of techniques able to analyse these kinds of systems is required to allow their progress. Here we show the implementation of the Ghost Particle Velocimetry (GPV) for the flow velocity field investigation in milli-fluidic devices. This innovative technique has been recently introduced, and has been already proven to be useful in describing rapid phenomenon at a small scale. In this work, the GPV has been used to characterize the trapping of light suspended material in a branching junction. Experiments have been performed to identify the flow velocity field close to a millimeters scale T-junction, at different Reynolds numbers. Particularly interesting are the complex structures, such as vortices and recirculation zones, induced by the vortex breakdown phenomenon. The results obtained have been deeply validated and compared with the well-established μPIV, highlighting the differences in terms of qualitative and quantitative parameters. A performance comparison has been designed to underline the strengths and weaknesses of the two experimental techniques.

  18. Effect of cohesion on granular-fluid flows in spouted beds: PIV measurement and DEM simulations

    Zhu, Runru; LI, Shuiqing; Yao, Qiang


    In contrast to wet granular flows, the effect of cohesion on complex granular-fluid flows is intriguing but much challenging. The liquid bridges, forming between binary particles with the addition of a small amount of liquids, might significantly change the granular-fluid system due to both cohesion and lubrication effects. In this paper, a spouted bed, among various fluidization technologies, is particularly selected as a prototypical system for studying granular-fluid flows, since it can provide a quasi-steady flow pattern of granular particles, i.e., a core of upward granular-fluid flow called the "spout" and a surrounding region of downward quasi-static granular flow called the "annulus". Firstly, using self-developed particle image velocimetery (PIV) technique, the effects of cohesion on the spout-annulus interface (namely the spout width) and on the particle velocity profiles in distinct zones are examined. Further, the discrete element method (DEM), by incorporating liquid bridge adhesion into soft-sphere model, is established and used to predict the microdynamic behavior of particles in spouted beds. Finally, based on both experiments and DEM validation, the effects on the granular patterns in these two zones are comparatively discussed.

  19. PIV-based study of the gliding osprey aerodynamics in a wind tunnel

    Gurka, Roi; Liberzon, Alex; Kopp, Gregory; Kirchhefer, Adam; Weihs, Daniel


    The hunting flight of an osprey consists of periods where the bird glides while foraging for prey. High quality measurements of aerodynamics in this flight mode are needed in order to estimate the daily energy expenditure of the bird accurately. An experimental study of an osprey model in a wind tunnel (BLWTL, UWO) was performed in order to characterize the aerodynamic forces using particle image velocimetry (PIV). The model was a stuffed osprey with mechanical joints allowing control of the the wing (angle of attack, tilt) and tail orientation. Two-dimensional velocity realizations in the streamwise-normal plane were obtained simultaneously in the two fields of view: above the wing and in the wake of the wing. Mean and turbulent flow characteristics are presented as function of angle of attack based on measurements taken at 4 different angles of attack at three different locations over the wingspan. The main outcome is the accurate estimate of the drag from the measurements of momentum thickness in the turbulent boundary layer of the osprey wing. Moreover, the gradient of the momentum thickness method was applied to identify the separation point in the boundary layer. This estimate has been compared to the total drag calculated from measurements in the wake of the wing and with a theoretical prediction.

  20. PIV measurements of isothermal plane turbulent impinging jets at moderate Reynolds numbers

    Khayrullina, A.; van Hooff, T.; Blocken, B.; van Heijst, G. J. F.


    This paper contains a detailed experimental analysis of an isothermal plane turbulent impinging jet (PTIJ) for two jet widths at moderate Reynolds numbers (7200-13,500) issued on a horizontal plane at fixed relative distances equal to 22.5 and 45 jet widths. The available literature on such flows is scarce. Previous studies on plane turbulent jets mainly focused on free jets, while most studies on impinging jets focused on the heat transfer between the jet and an impingement plane, disregarding jet development. The present study focuses on isothermal PTIJs at moderate Reynolds numbers characteristic of air curtains. Flow visualisations with fluorescent dye and 2D particle image velocimetry (PIV) measurements have been performed. A comparison is made with previous studies of isothermal free turbulent jets at moderate Reynolds numbers. Mean and instantaneous velocity and vorticity, turbulence intensity, and Reynolds shear stress are analysed. The jet issued from the nozzle with higher aspect ratio shows more intensive entrainment and a faster decay of the centreline velocity compared to the jet of lower aspect ratio for the same value of jet Reynolds number. The profiles of centreline and cross-jet velocity and turbulence intensity show that the PTIJs behave as a free plane turbulent jet until 70-75% of the total jet height. Alongside the information obtained on the jet dynamics, the data will be useful for the validation of numerical simulations.

  1. Visualization of the Precessing Vortex Core in a Cyclone Separator by PIV

    吴小林; 时铭显


    The precessing vortex core (PVC) in a cyclone separator plays an important role in the separation performance and in further understanding of the general law of periodic unsteady flow therein. In this paper, the unsteady flow field is investigated with particle image velocimetry (PIV), and the instantaneous velocity, vorticity,tangential velocity, and radial velocity are acquired by analyzing the images of instantaneous flow. It is for the first time reported that there is a centrifugal flow region close to the dust discharge zone and its maximum value is higher than the mean radial velocity. This discovery is very important for understanding the principle of separation of particles in the area of dust discharge. Determination of the frequency and amplitude of PVC was conducted in the region where the phenomenon of PVC is remarkable. Results agree well with those obtained by hot wire anemometry. The observations of the center of "cortex core and the bimodal distribution of the amplitude of the PVC indicate the vortex core precesses around the geometric axis of the cvclone in its own way.

  2. Use of the Piv Method for Investigation of Motion Near a Cylinder in Transverse Flow

    Dobrosel'skii, K. G.


    Turbulent flow past a cylinder in a wind tunnel has been investigated experimentally. Averaged velocity fields near the cylinder have been obtained with the optical PIV method and comparative characteristics have been given for noncavitation and cavitation regimes. From the vector patterns of the averaged velocity fields, the author has determined the angles of separation of the boundary layer from the cylinder surface in the considered regimes of flow. It has been shown that cavitation causes the vortex zone behind the cylinder to increase, the separation angles to displace upstream, and the hydraulic resistance to grow. A comparative calculation of the separation angles and the coefficients of hydraulic resistance of cylinders manufactured from different materials has been given. It has been shown that the vortex zone of a Teflon cylinder in flow having a hydrophobic surface differs from the vortex zone of a steel cylinder, particularly for the cavitation regime in which the angles of separation, especially from the upper part, decrease appreciably and the resistance grows.

  3. Micro-PIV measurements of blood flow in extraembryonic blood vessels of chicken embryos.

    Lee, Jung Yeop; Ji, Ho Seong; Lee, Sang Joon


    The hemodynamic characteristics of blood flow are important in the diagnosis of circulatory diseases, since such diseases are related to wall shear stress of cardiovascular vessels. In chicken embryos at early stages of development, it is possible to directly visualize blood flow inside blood vessels. We therefore employed a micro-PIV technique to assess blood flow in extraembryonic venous and arterial blood vessels of chicken embryos, using red blood cells (RBCs) as tracers and obtaining flow images of RBCs using a high-speed CMOS camera. The mean velocity field showed non-Newtonian flow characteristics. The blood flow in two venous vessels merged smoothly into the Y-shaped downstream vein without any flow separation or secondary flow. Vorticity was high in the inner regions, where the radius of curvature varied greatly. A periodic variation of temporally resolved velocity signals, due to beating of the heart, was observed in arterial blood vessels. The pulsating frequency was obtained by fast Fourier transform analysis using the measured velocity data. The measurement technique used here was useful in analyzing the hemodynamic characteristics of in vivo blood flow in chicken embryos.

  4. A PIV Study of Slotted Air Injection for Jet Noise Reduction

    Henderson, Brenda S.; Wernet, Mark P.


    Results from acoustic and Particle Image Velocimetry (PIV) measurements are presented for single and dual-stream jets with fluidic injection on the core stream. The fluidic injection nozzles delivered air to the jet through slots on the interior of the nozzle at the nozzle trailing edge. The investigations include subsonic and supersonic jet conditions. Reductions in broadband shock noise and low frequency mixing noise were obtained with the introduction of fluidic injection on single stream jets. Fluidic injection was found to eliminate shock cells, increase jet mixing, and reduce turbulent kinetic energy levels near the end of the potential core. For dual-stream subsonic jets, the introduction of fluidic injection reduced low frequency noise in the peak jet noise direction and enhanced jet mixing. For dual-stream jets with supersonic fan streams and subsonic core streams, the introduction of fluidic injection in the core stream impacted the jet shock cell structure but had little effect on mixing between the core and fan streams.

  5. μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble.

    Yamaguchi, Eiichiro; Smith, Bradford J; Gaver, Donald P


    Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method.

  6. Time-resolved PIV investigation of flashback in stratified swirl flames of hydrogen-rich fuel

    Ranjan, Rakesh; Clemens, Noel


    Hydrogen is one of the promising alternative fuels to achieve greener power generation. However, susceptibility of flashback in swirl flames of hydrogen-rich fuels acts as a major barrier to its adoption in gas turbine combustors. The current study seeks to understand the flow-flame interaction during the flashback of the hydrogen-rich flame in stratified conditions. Flashback experiments are conducted with a model combustor equipped with an axial swirler and a center-body. Fuel is injected in the main swirl flow via the fuel ports on the swirler vanes. To achieve mean radial stratification, these fuel ports are located at a radial location closer to the outer wall of the mixing tube. Stratification in the flow is assessed by employing Anisole PLIF imaging. Flashback is triggered by a rapid increase in the global equivalence ratio. The upstream propagation of the flame is investigated by employing time-resolved stereoscopic PIV and chemiluminescence imaging. Stratification leads to substantially different flame propagation behavior as well as increased flame surface wrinkling. We gratefully acknowledge the sponsorship by the DOE NETL under Grant DEFC2611-FE0007107.

  7. PIV Measurements of the CEV Hot Abort Motor Plume for CFD Validation

    Wernet, Mark; Wolter, John D.; Locke, Randy; Wroblewski, Adam; Childs, Robert; Nelson, Andrea


    NASA s next manned launch platform for missions to the moon and Mars are the Orion and Ares systems. Many critical aspects of the launch system performance are being verified using computational fluid dynamics (CFD) predictions. The Orion Launch Abort Vehicle (LAV) consists of a tower mounted tractor rocket tasked with carrying the Crew Module (CM) safely away from the launch vehicle in the event of a catastrophic failure during the vehicle s ascent. Some of the predictions involving the launch abort system flow fields produced conflicting results, which required further investigation through ground test experiments. Ground tests were performed to acquire data from a hot supersonic jet in cross-flow for the purpose of validating CFD turbulence modeling relevant to the Orion Launch Abort Vehicle (LAV). Both 2-component axial plane Particle Image Velocimetry (PIV) and 3-component cross-stream Stereo Particle Image Velocimetry (SPIV) measurements were obtained on a model of an Abort Motor (AM). Actual flight conditions could not be simulated on the ground, so the highest temperature and pressure conditions that could be safely used in the test facility (nozzle pressure ratio 28.5 and a nozzle temperature ratio of 3) were used for the validation tests. These conditions are significantly different from those of the flight vehicle, but were sufficiently high enough to begin addressing turbulence modeling issues that predicated the need for the validation tests.

  8. Estimation of viscous dissipative stresses induced by a mechanical heart valve using PIV data.

    Li, Chi-Pei; Lo, Chi-Wen; Lu, Po-Chien


    Among the clinical complications of mechanical heart valves (MHVs), hemolysis was previously thought to result from Reynolds stresses in turbulent flows. A more recent hypothesis suggests viscous dissipative stresses at spatial scales similar in size to red blood cells may be related to hemolysis in MHVs, but the resolution of current instrumentation is insufficient to measure the smallest eddy sizes. We studied the St. Jude Medical (SJM) 27 mm valve in the aortic position of a pulsatile circulatory mock loop under physiologic conditions with particle image velocimetry (PIV). Assuming a dynamic equilibrium assumption between the resolved and sub-grid-scale (SGS) energy flux, the SGS energy flux was calculated from the strain rate tensor computed from the resolved velocity fields and the SGS stress was determined by the Smagorinsky model, from which the turbulence dissipation rate and then the viscous dissipative stresses were estimated. Our results showed Reynolds stresses up to 80 N/m2 throughout the cardiac cycle, and viscous dissipative stresses below 12 N/m2. The viscous dissipative stresses remain far below the threshold of red blood cell hemolysis, but could potentially damage platelets, implying the need for further study in the phenomenon of MHV hemolytic complications.

  9. 3D Reconstruction of the Vortex in a Human Right Ventricle Model using High Speed PIV

    Kheradvar, Arash; Falahatpisheh, Ahmad


    This work aims to characterize the formation process and translation of the vortex, which forms along with the trans-tricuspid jet in a realistic model of a human right ventricle (RV). A clear model of the RV made of silicone rubber was carefully casted in real size from echocardiographic data of an adult human heart. The RV model was used in our heart pulsed-flow simulator at KLAB at UCI to perform experiments. Bioprosthetic heart valves in appropriate sizes were used at tricuspid and pulmonary positions. Multi-planar high-speed PIV was performed to capture and reconstruct the 3D flow field with a 1-millisecond time gap between each two velocity frames. λ2 iso-surfaces were used to illustrate the evolution of vortex cores. The highly asymmetric shape of the RV chamber results in a complex 3D trans-tricuspid vortex that forms and translates toward right ventricular outflow tract, and finally departs RV from pulmonary valve. Through this study, -for the first time- the formation, evolution and pathway of the RV vortex have been characterized in vitro.

  10. Investigation of the hydrodynamic model test of forced rolling for a barge using PIV

    WANG Xiaoqiang


    Full Text Available In order to study the physical details of viscous flow in ship roll motions and improve the accuracy of ship roll damping numerical simulation, the application of the Particle Image Velocimetry (PIV technique is investigated in model tests of forced ship rolling in calm water. The hydrodynamic force and flow field at the bilge region are simultaneously measured for barges at different amplitudes and frequencies in which the self-made forced rolling facility was used. In the model test, the viscous flow variation with the time around the bilge region was studied during ship rolling motion. The changes in ship roll damping coefficients with the rolling amplitude and period were also investigated. A comparison of the model test results with the Computational Fluid Dynamics(CFDresults shows that the numerical ship roll damping coefficients agree well with the model test results, while the differences in the local flow details exist between the CFD results and model test results. Further research into the model test technique and CFD application is required.

  11. Dune formation in dilute phase pneumatic transport system: PIV & PTV based analysis

    Jhalani, Sumit; Patankar, Atharva; Makawana, Ajay; Bose, Manaswita


    Flow of gas-solid mixture through horizontal conveying section show a large variety of phenomena and is broadly classified into dilute and dense unstable regimes. Different types of instabilities are observed in the dense phase flow and are widely studied in literature; however, clustering instabilities are observed in the very dilute regime of flow with volume fraction 0.001. A recent study has shown that regular, stable dune shaped clusters are formed in a small regime of the dilute phase of conveying. The dunes become unstable as the superficial gas velocity is decreased before it finally leads to the dense mode of conveying. The motivation of the current work is to investigate the velocity distribution on the surface of the stable and unstable dunes and thereby understand the cause behind the formation of the dunes in the conveying section. To that end, particle image and tracking velocimetry techniques are employed with the specific objective to determine the volume fraction and the velocity profile of the solid phase on the stable dune surface. A drastic change in the solid fraction within a few particle diameters from the dune surface suggests that PTV is more appropriate in the bulk whereas PIV is suitable for near surface investigation.

  12. Time-resolved Tomographic PIV Measurements of Water Flea Hopping: Body Size Comparison

    Skipper, A. N.; Murphy, D. W.; Webster, D. R.; Yen, J.


    The flow field of the freshwater crustacean Daphnia magna is quantified with time-resolved tomographic PIV. In the current work, we compare body kinematics and flow disturbance between organisms of small (body length = 1.8 mm) versus medium (2.3 mm) versus large (2.65 mm) size. These plankters are equipped with a pair of antennae that are biramous such that the protopodite splits or branches into an exopodite and an endopodite. They beat the antennae pair synchronously to impulsively propel themselves, or `hop,' through the water. The stroke cycle of Daphnia magna is roughly 80 ms in duration and this period is evenly split between the power and recovery strokes. A typical hop carries the daphniid one body length forward and is followed by a period of sinking. Unlike copepod escape motion, no body vortex is observed in front of the animal. Rather, the flow induced by each antennae consists of a viscous vortex ring that demonstrates a slow decay. The time-record of velocity (peak of 40 mm/s for the medium specimen) and hop acceleration (1.8 m/s2 for the medium specimen) are compared, as well as the strength, size, and decay of the induced viscous vortex rings. The viscous vortex ring analysis will be presented in the context of a double Stokeslet model consisting of two impulsively applied point forces separated by the animal width.

  13. High-Speed Hopping: Time-Resolved Tomographic PIV Measurements of Water Flea Swimming

    Murphy, D. W.; Webster, D. R.; Yen, J.


    Daphniids, also known as water fleas, are small, freshwater crustaceans that live in a low-to-intermediate Reynolds number regime. These plankters are equipped with a pair of branched, setae-bearing antennae that they beat to impulsively propel themselves, or ``hop,'' through the water. A typical hop carries the daphniid one body length forward and is followed by a period of sinking. We present time-resolved tomographic PIV measurements of swimming by Daphnia magna. The body kinematics and flow physics of the daphniid hop are quantified. It is shown that the flow generated by each stroking antenna resembles an asymmetric viscous vortex ring. It is proposed that the flow produced by the daphniid hop can be modeled as a double Stokeslet consisting of two impulsively applied point forces separated by the animal width. The flow physics are discussed in the context of other species operating in the same Reynolds number range of 10 to 100: sea butterfly swimming and flight by the smallest flying insects.



    Particle Imaging Velocimetry (PIV) techniques were applied to investigate the particle motion and cluster properties in a gas-solid two-phase flow in a circulating fluidized bed riser. Visual images and micro-structure of various clusters were captured. After the boundary of clusters was determined by the gray level threshold method, clusters were classified by the distance between particles and the shape and position of clusters. In addition, the process of clusters forming and breaking up was described, and the sizes of clusters were also obtained. With the Minimum Quadric Difference (MQD) cross-correlation algorithm suitable for high-density particles, the axial velocities of the particles were obtained in the dilute phase section. The features of particle motion were revealed by investigating statistically the magnitude and distribution of particle axial velocity in the radial direction. At most radial cross-sections, there exists a parabola-shaped distribution of upward axial velocity of particles, namely, the magnitude of axial velocity in the core region is higher than that near the wall region of the riser.

  15. Simultaneous PIV and PTV measurements of wind and sand particle velocities

    Zhang, Wei; Wang, Yuan; Lee, Sang Joon


    Wind-blown sand is a typical example of two-phase particle-laden flows. Owing to lack of simultaneous measured data of the wind and wind-blown sand, interactions between them have not yet been fully understood. In this study, natural sand of 100-125 μm taken from Taklimakan Desert was tested at the freestream wind speed of 8.3 m/s in an atmospheric boundary layer wind tunnel. The captured flow images containing both saltating sand and small wind tracer particles, were separated by using a digital phase mask technique. The 2-D PIV (particle imaging velocimetry) and PTV (particle tracking velocimetry) techniques were employed to extract simultaneously the wind velocity field and the velocity field of dispersed sand particles, respectively. Comparison of the mean streamwise wind velocity profile and the turbulence statistics with and without sand transportation reveal a significant influence of sand movement on the wind field, especially in the dense saltating sand layer ( y/ δ < 0.1). The ensemble-averaged streamwise velocity profile of sand particles was also evaluated to investigate the velocity lag between the sand and the wind. This study would be helpful in improving the understanding of interactions between the wind and the wind-blown sand.

  16. Experimental study of porous media flow using hydro-gel beads and LED based PIV

    Harshani, H. M. D.; Galindo-Torres, S. A.; Scheuermann, A.; Muhlhaus, H. B.


    A novel experimental approach for measuring porous flow characteristics using spherical hydro-gel beads and particle image velocimetry (PIV) technique is presented. A transparent porous medium consisting of hydro-gel beads that are made of a super-absorbent polymer, allows using water as the fluid phase while simultaneously having the same refractive index. As a result, a more adaptable and cost effective refractive index matched (RIM) medium is created. The transparent nature of the porous medium allows optical systems to visualize the flow field by using poly-amide seeding particles (PSP). Low risk light emitting diode (LED) based light was used to illuminate the plane in order to track the seeding particles’ path for the characterization of the flow inside the porous medium. The system was calibrated using a manually measured flow by a flow meter. Velocity profiles were obtained and analysed qualitatively and quantitatively in order to characterise the flow. Results show that this adaptable, low risk experimental set-up can be used for flow measurements in porous medium under low Reynolds numbers. The limitations of using hydro-gel beads are also discussed.

  17. Experimental study by PIV of swirling flow induced by trapezoid-winglets

    车翠翠; 田茂诚; 张冠敏; 冷学礼


    The characteristics of the longitudinal vortex induced by trapezoid-winglets in a circular tube are investigated by the Particle Image Velocimetry (PIV) Technique with flow Reynolds number in the range of 500-13 000. In the experimental test section, four trapezoid-winglets are fixed symmetrically on the tube wall in two different ways: up-flow and down-flow. The results show that a counter-rotating vortex pair is formed behind each winglet and they distribute as a symmetrical vortex array in the transverse section. Between the two vortexes in a vortex pair the fluid flows towards the wall in the up-flow winglet case and away from the wall in the down-flow winglet case, corresponding also to the regions of peak values of the velocity components normal to the mainstream. Both of the flow patterns enhance the velocity in the near wall region, leading to the intensification of the transverse mixing and the mass transfer in the tube. With Reynolds number increasing, the flow maintains the vortex pattern in the case of the up-flow winglets, indicating better persistence of the longitudinal vortex, while the vortexes in the case of the down-flow winglets are more scattered and tend to breaking into small eddies. The trapezoid winglet shows the preferable turbulent disturbance characteristics in the tube and the experimental results provide benchmark data for further CFD studies.

  18. Non-invasive estimation of coral tentacle material properties using underwater PIV data

    Staples, Anne; Asher, Shai; Shavit, Uri


    With corals worldwide currently undergoing a third global bleaching event, understanding a detailed picture of local coral colony flow transport processes is more crucial than ever. Many coral species invest energy in extending flexible organs such as tentacles, that extrude from the coral's soft tissue surface and are used in either a passive or active manner for feeding, competitor sensing and even egg release. The significant role of these organs in transport and mixing processes is just beginning to be understood. For example, Xeniidea's rhythmic pulsation of its tentacles has recently been shown to intensify mixing and enhance photosynthesis (Kremien et al., 2013). A critical part of modeling these tentacle-induced flows is obtaining measurements of the tentacles' material properties. Obtaining such measurements, however, is challenging, since the tentacle is expected to have significantly different material properties than a harvested specimen. Here, we demonstrate a non-invasive, in situ approach for estimating these material properties forFavia favus tentacles using underwater particle image velocimetry (PIV) data and tentacle-tracking data, along with structural dynamics models of the tentacles. In this data, 2.7x2 [cm2] 1392x1024 pixel images were collected at a rate of 5 Hz 7mm above the crest of two separate Favia Favuscolonies in Eilat, Israel. Using the data and models, we are able to estimate the Young's modulus for the tentacles, which is found to be a function of the wave frequency. Partial funding by the Fulbright and Israel Science Foundations.

  19. Investigating droplet internal flow in concentrated emulsion when flowing in microchannel using micro-PIV

    Leong, Chia Min; Gai, Ya; Tang, Sindy K. Y.


    Droplet microfluidics has enabled a wide variety of high throughput applications through the use of monodisperse droplets. Previous fluid studies of droplet microfluidics have focused on single drops or emulsions at low volume fractions. The study of concentrated emulsions at high volume fractions is important for increasing the throughput, but the fluid dynamics of such emulsions in confined channels is not well understood. Here we describe two-dimensional, mid-height measurements of the flow inside individual drops within a concentrated emulsion using micro-PIV. The emulsion has 85% volume fraction and flows as a monolayer in a straight microfluidic channel. The effects of confinement and viscosity ratio on the internal flow patterns inside the drops were studied. The results show rotational structures inside the drops always exist, and are independent of viscosity ratio for the conditions tested. The structures depend on droplet mobility which in turn, depends on the confinement of the emulsion and the location of the drops in the channel. To our best knowledge, no work has probed the flow field inside droplets of concentrated emulsions at high volume fractions in confined channels. Current work is in progress to measure the three-dimensional flow field in such system.

  20. Unsteady characteristics of near-wall turbulence using high repetition stereoscopic particle image velocimetry (PIV)

    Foucaut, J. M.; Coudert, S.; Stanislas, M.


    This study is part of a project that is aimed at building dynamic boundary conditions near a solid wall, in order to reduce the large eddy simulation spatial resolution that is necessary in this region. The objective is to build a low-order dynamical system in a plane parallel to the wall, which will mimic the unsteady behaviour of turbulence. This dynamical system should be derived from a POD decomposition of the velocity field. The POD decomposition is to be applied on an experimental database of time-resolved velocity fields. In order to obtain the experimental database, a specific experiment of high-speed stereoscopic particle image velocimetry (PIV) has been performed. This experiment was carried out in the turbulent boundary layer of the LML wind tunnel. The plane under study was parallel to the wall located at 100 wall units. This database is validated via comparison with hot-wire anemometry (HWA). Despite some peak locking observed on the streamwise velocity component, the PDF and the power spectra are in very good agreement with the HWA results. The two-point spatial correlations are also in good agreement with the results from the literature. As the flow is time-resolved, space-time correlations are also computed. The convection of the flow structure is observed to be the most important effect at this wall distance. The next step is to compute the dynamical system and to couple it to a large eddy simulation.

  1. Assessment of tomographic PIV in wall-bounded turbulence using direct numerical simulation data

    Silva, C.M. de; Baidya, R.; Khashehchi, M.; Marusic, I. [University of Melbourne, Department of Mechanical Engineering, Melbourne, VIC (Australia)


    Simulations of tomographic particle image velocimetry (Tomo-PIV) are performed using direct numerical simulation data of a channel flow at Reynolds number of Re{sub {tau}} = 934, to investigate the influence of experimental parameters such as camera position, seeding density, interrogation volume size and spatial resolution. The simulations employ camera modelling, a Mie scattering illumination model, lens distortion effects and calibration to realistically model a tomographic experiment. Results are presented for camera position and orientation in three-dimensional space, to obtain an optimal reconstruction quality. Furthermore, a quantitative analysis is performed on the accuracy of first and second order flow statistics, at various voxel sizes normalised using the viscous inner length scale. This enables the result to be used as a general reference for wall-bounded turbulent experiments. In addition, a ratio relating seeding density and the interrogation volume size is proposed to obtain an optimal reference value that remains constant. This can be used to determine the required seeding density concentration for a certain interrogation volume size. (orig.)

  2. Tomo-PIV Measurement of High Reynolds Number Dissipation Scale Structures

    Worth, Nicholas; Nickels, Timothy


    Understanding the sources of dissipative intermittency in high Reynolds number turbulence is of significant interest, especially given the increasing affordability of LES. Coherent dissipation scale structures have been identified in numerous numerical and experiment investigations, although the latter are typically restricted by the need for accurate resolution of extremely small fast motions. These investigations are therefore often limited to one-dimensional measurements, making the study of these 3D structures and their relationship to the dissipation field difficult. The current investigation employs a very large water mixing tank (2m in diameter), which uses counter-rotating impellors to generate high Reynolds number turbulence (Rλ 1000) that is close to isotropic and homogeneous. The large scale of the tank brings the smallest scales within the resolution of Tomo-PIV, allowing full 3D realization of these structures. This unique experimental setup presents a number of challenges, which include: seeding density limitations imposed by optical attenuation through the tank; demanding light sheet intensity requirements; and the extremely high computational cost of Tomographic reconstruction for the thousands of velocity fields required for statistical analysis. Initial results will be presented along with future plans for measurement refinement.

  3. PIV measurement of the vertical cross-flow structure over tube bundles

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    Shell and tube heat exchangers are among the most commonly used types of heat exchangers. Shell-side cross-flow in tube bundles has received considerable attention and has been investigated extensively. However, the microscopic flow structure including velocity distribution, wake, and turbulent structure in the tube bundles needs to be determined for more effective designs. Therefore, in this study, in order to clarify the detailed structure of cross-flow in tube bundles with particle image velocimetry (PIV), experiments were conducted using two types of model; in-line and staggered bundles with a pitch-to-diameter ratio of 1.5, containing 20 rows of five 15 mm O.D. tubes in each row. The velocity data in the whole flow field were measured successfully by adjusting the refractive index of the working fluid to that of the tube material. The flow features were characterized in different tube bundles with regards to the velocity vector field, vortex structure, and turbulent intensity.

  4. Studies on Rheology of E-printing Inks by μ-PIV in Microchannels

    Jang, Young-Sik; Song, Simon


    Using printing technologies for electronic circuits, such as antennas for radio frequency identification (RFID) chips, has been paid attention to recently in order to reduce production costs. In general, E-printing inks used for printed electronics have non-Newtonian properties because they contain metallic particles. Thus, it is important to investigate rheological behaviors of E-printing inks and suggest proper rheological models for developing printing devices for printed electronics. Also, the rheological models are necessary to accurately predict ink behaviors using CFD. However, classic methods to study rheological models are somewhat irrelevant since they require the mass consumption of expensive E-printing inks. Thus, to study rheological models suitable for commercial E-printing inks, we use microfluidic chips that only requires nascent E-printing inks. We measured flow velocities using μPIV and pressure drops along the microchannel to determine a relationship between stress and strain rate of ink flows. We found that the E-printing inks exhibit shear-thinning behaviors. In the presentation, we will propose rheology models suitable for the E-printing inks.

  5. PIV Experiments to Measure Flow Phenomena in a Scaled Model of a VHTR Lower Plenum

    Hugh M. McIlroy, Jr.; Donald M. McEligot; Richard R. Schultz; Daniel Christensen; Robert J. Pink; Ryan C. Johnson


    A report of experimental data collected at the Matched-Index-of-Refraction (MIR) Laboratory in support of contract DE-AC07-05ID14517 and the INL Standard Problem on measurements of flow phenomena occurring in a lower plenum of a typical prismatic VHTR concept reactor to assess CFD code is presented. Background on the experimental setup and procedures is provided along with several samples of data obtained from the 3-D PIV system and an assessment of experimental uncertainty is provided. Data collected in this study include 3-dimensional velocity-field descriptions of the flow in all four inlet jets and the entire lower plenum with inlet jet Reynolds numbers (ReJet) of approximately 4300 and 12,400. These investigations have generated over 2 terabytes of data that has been processed to describe the various velocity components in formats suitable for external release and archived on removable hard disks. The processed data from both experimental studies are available in multi-column text format.

  6. Particle image velocimetry (PIV) study of rotating cylindrical filters for animal cell perfusion processes.

    Figueredo-Cardero, Alvio; Chico, Ernesto; Castilho, Leda; de Andrade Medronho, Ricardo


    In the present work, the main fluid flow features inside a rotating cylindrical filtration (RCF) system used as external cell retention device for animal cell perfusion processes were investigated using particle image velocimetry (PIV). The motivation behind this work was to provide experimental fluid dynamic data for such turbulent flow using a high-permeability filter, given the lack of information about this system in the literature. The results shown herein gave evidence that, at the boundary between the filter mesh and the fluid, a slip velocity condition in the tangential direction does exist, which had not been reported in the literature so far. In the RCF system tested, this accounted for a fluid velocity 10% lower than that of the filter tip, which could be important for the cake formation kinetics during filtration. Evidence confirming the existence of Taylor vortices under conditions of turbulent flow and high permeability, typical of animal cell perfusion RCF systems, was obtained. Second-order turbulence statistics were successfully calculated. The radial behavior of the second-order turbulent moments revealed that turbulence in this system is highly anisotropic, which is relevant for performing numerical simulations of this system.

  7. Time resolved, near wall PIV measurements in a high Reynolds number turbulent pipe flow

    Willert, C.; Soria, J.; Stanislas, M.; Amili, O.; Bellani, G.; Cuvier, C.; Eisfelder, M.; Fiorini, T.; Graf, N.; Klinner, J.


    We report on near wall measurements of a turbulent pipe flow at shear Reynolds numbers up to Reτ = 40000 acquired in the CICLoPE facility near Bologna, Italy. With 900 mm diameter and 110 m length the facility offers a well-established turbulent flow with viscous length scales ranging from y+ = 85 μ m at Reτ = 5000 to y+ = 11 μ m at Reτ = 40000 . These length scales can be resolved with a high-speed PIV camera at image magnification near unity. For the measurement the light of a high-speed, double-pulse laser is focused into a 300 μ m thin light sheet that is introduced radially into the pipe. The light scattered by 1 μ m water-glycerol droplet seeding is observed from the side by the camera via a thin high-aspect ratio mirror with a field of view covering 20mm in wall-normal and 5mm in stream-wise direction. Statistically converged velocity profiles could be achieved using 70000 samples per sequence acquired at low laser repetition rates (100Hz). Higher sampling rates of 10 kHz provide temporally coherent data from which frequency spectra can be derived. Preliminary analysis of the data shows a well resolved inner peak that grows with increasing Reynolds number. (Project funding through EuHIT -

  8. HFSB-seeding for large-scale tomographic PIV in wind tunnels

    Caridi, Giuseppe Carlo Alp; Ragni, Daniele; Sciacchitano, Andrea; Scarano, Fulvio


    A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator, the system increases the rate of bubbles emission by means of transient accumulation and rapid release. The governing parameters of the system are identified and discussed, namely the bubbles production rate, the accumulation and release times, the size of the bubble injector and its location with respect to the wind tunnel contraction. The relations between the above parameters, the resulting spatial concentration of tracers and measurement of dynamic spatial range are obtained and discussed. Large-scale experiments are carried out in a large low-speed wind tunnel with 2.85 × 2.85 m2 test section, where a vertical axis wind turbine of 1 m diameter is operated. Time-resolved tomographic PIV measurements are taken over a measurement volume of 40 × 20 × 15 cm3, allowing the quantitative analysis of the tip-vortex structure and dynamical evolution.

  9. Large eddy simulation and PIV experiments of air-water mixing tanks

    Zamankhan, Piroz


    The simulations and experiments of a turbulent bubbly flow are carried out in a cylindrical mixing vessel. Dynamics of the turbulent bubbly flow is visualized using a novel two-phase particle image velocimetry (PIV) with a combination of back lighting, digital masking and fluorescent tracer particles. Using an advanced technique, Mie's scattering at surfaces of bubbles is totally filtered out and, henceforth, images of tracer particles and of bubbles are obtained with high quality. In parallel to the comprehensive experimental studies, numerical results are obtained from large eddy simulations (LES) of the two-phase air-water mixer. The impeller-induced flow at the blade tip radius is modeled by using sliding mesh method. The results demonstrate the existence of large structures such as tip-vortex tips, and also some finer details. In addition, the stability of the jet is found to be connected with the fluctuations of the tip vortices whose dynamics are affected by the presence of bubbles. Numerical results are used to interpret the measurement data and to guide the refinement of consistent theoretical analyses. Such information is invaluable in the development of advanced theories capable of describing bubbly flows in the presence of complex liquid flow. This detailed information is of real significance in facilitating the design and scale-up of practical stirred tanks.


    Radek Šulc


    Full Text Available The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV. The experiments were carried out in a fully baffled cylindrical flat bottom vessel 300 mm in inner diameter. The tank was agitated by a Rushton turbine 100 mm in diameter. The velocity fields were measured for three impeller rotation speeds 300 rpm, 450 rpm and 600 rpm and the corresponding Reynolds numbers in the range 50 000 < Re < 100 000, which means that the fully-developed turbulent flow was reached. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller rotational speed. The velocity profiles were averaged, and were expressed by Chebyshev polynomials of the 1st order. Although the experimentally investigated area was relatively far from the impeller, and it was located in upward flow to the impeller, no state of local isotropy was found. The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768. The axial turbulence intensity was found to be in the range from 0.293 to 0.667, which corresponds to a high turbulence intensity.

  11. Measurements of the velocity fields by PIV method round about titling gate

    Mistrová Ivana


    Full Text Available The article deals with problems of using of measurement method Particle Image Velocimetry (PIV to measure velocity fields in the flowing water in front, above and behind drowned titling weir gate. The aim was to obtain information about the distribution of speed in the area of interest for the verification or calibration of the numerical model. Experiments were carried out in inclinable channel connected to the hydraulic circuit with a pump and storage tank at the Water Management Research Laboratory (LVV of Institute of Water Structures at the Faculty of Civil Engineering in Brno University of Technology. Hydraulic inclinable channel has cross-section with dimensions of 0.4×0.4m and length of 12.5m. The measured area has cross-section approximately 0.2m wide and 0.4m high and its length is 1m. The results of physical modelling allowed a comparison of experimental data with numerical simulation results of this type of flow in the commercial software ANSYS CFX-12.0.

  12. Stereoscopic PIV measurements of a turbulent boundary layer with a large spatial dynamic range

    Herpin, Sophie [MONASH University, Laboratory for Turbulence Research in Aerospace and Combustion, Department of Mechanical Engineering, Melbourne, VIC (Australia); Cite Scientifique, Laboratoire de Mecanique de Lille (UMR CNRS 8107), Ecole Centrale de Lille, Bd Paul Langevin, Villeneuve d' Ascq (France); Wong, Chong Yau [MONASH University, Laboratory for Turbulence Research in Aerospace and Combustion, Department of Mechanical Engineering, Melbourne, VIC (Australia); CSIRO Materials Science and Engineering, Commonwealth Science and Industrial Research Organisation (CSIRO) Thermal and Fluid Dynamics, Highett, VIC (Australia); Stanislas, Michel [Cite Scientifique, Laboratoire de Mecanique de Lille (UMR CNRS 8107), Ecole Centrale de Lille, Bd Paul Langevin, Villeneuve d' Ascq (France); Soria, Julio [MONASH University, Laboratory for Turbulence Research in Aerospace and Combustion, Department of Mechanical Engineering, Melbourne, VIC (Australia)


    The flow in a streamwise/wall-normal plane of a turbulent boundary layer at moderate Reynolds number (Re{sub {theta}}=2,200) is characterized using two stereo PIV systems just overlapping in the streamwise direction. The aim is to generate SPIV data for near-wall turbulence with enough spatial dynamic range to resolve most of the coherent structures present in the flow and to facilitate future comparisons with direct numerical simulations. This is made possibly through the use of four cameras with large CCD arrays (4,008 px x 2,672 px) and through a rigorous experimental procedure designed to minimize the impact of measurement noise on the resolution of the small scales. For the first time, both a large field of view [S{sub x}; S{sub y}]=[2.6{delta}; 0.75{delta}] and a high spatial resolution (with an interrogation window size of 13.6{sup +}) have been achieved. The quality of the data is assessed through an analysis of some of the statistical results such as the mean velocity profile, the rms and the PDF of the fluctuations, and the power spectra. (orig.)

  13. Stereo-PIV study of flow inside an eye under cataract surgery

    Sakakibara, Jun; Yamashita, Masaki; Kobayashi, Tatsuya; Kaji, Yuichi; Oshika, Tetsuro


    We measured velocity distributions in the anterior chamber of porcine eyes under simulated cataract surgery using stereoscopic particle image velocimetry (stereo-PIV). The surface of the cornea was detected based on the images of laser-induced fluorescent light emitted from fluorescent dye solution introduced in a posterior chamber. A coaxial phacoemulsification procedure was simulated with standard size (standard coaxial phacoemulsification) and smaller (micro coaxial phacoemulsification) surgical instruments. In both cases, an asymmetric flow rate of irrigation was observed, although both irrigation ports had the same dimensions prior to insertion into the eye. In cases where the tip of the handpiece was placed farther away from the top of the cornea, i.e., closer to the crystalline lens, direct impingement of irrigation flow onto the cornea surface was avoided and the flow turned back toward the handpiece along the surface of the corneal endothelium. Viscous shear stress on the corneal endothelium was computed based on the measured mean velocity distribution. The maximum shear stress for most cases exceeded 0.1 Pa, which is comparable to the shear stress that caused detachment of the corneal endothelial cells reported by Kaji et al. in Cornea 24:S55-S58, (2005). When direct impingement of the irrigation flow was avoided, the shear stress was reduced considerably.

  14. PIV experiments in rough-wall, laminar-to-turbulent, oscillatory boundary-layer flows

    Mujal-Colilles, Anna; Mier, Jose M.; Christensen, Kenneth T.; Bateman, Allen; Garcia, Marcelo H.


    Exploratory measurements of oscillatory boundary layers were conducted over a smooth and two different rough beds spanning the laminar, transitional and turbulent flow regimes using a multi-camera 2D-PIV system in a small oscillatory-flow tunnel (Admiraal et al. in J Hydraul Res 44(4):437-450, 2006). Results show how the phase lag between bed shear stress and free-stream velocity is better defined when the integral of the momentum equation is used to estimate the bed shear stress. Observed differences in bed shear stress and phase lag between bed shear stress and free-stream velocity are highly sensitive to the definition of the bed position ( y = b). The underestimation of turbulent stresses close to the wall is found to explain such differences when using the addition of Reynolds and viscous stresses to define both the bed shear stress and the phase lag. Regardless of the flow regime, in all experiments, boundary-layer thickness reached its maximum value at a phase near the flow reversal at the wall. Friction factors in smooth walls are better estimated using a theoretical equation first proposed by Batchelor (An introduction to fluid dynamics. Cambridge University Press, Cambridge, 1967) while the more recent empirical predictor of Pedocchi and Garcia (J Hydraul Res 47(4):438-444, 2009a) was found to be appropriate for estimating friction coefficients in the laminar-to-turbulent transition regime.

  15. Characterization of Microfluidic Devices by Measurements with μ-PIV and CLSM

    Schlter, Michael; Hoffmann, Marko; Rbiger, Norbert

    Microfluidic devices are successfully in use for several applications in chemical engineering and biotechnology. Nevertheless, there is still no breakthrough for microprocess engineering because of a huge lack in understanding of the mechanisms on microscales for momentum transfer, hydrodynamics and mass transfer. Some important questions concern the design of a junction to reach acceptable mixing qualities with minimum pressure drop and narrow residence time distribution even under laminar flow conditions. The micro-particle image velocimetry (μ-PIV) in conjunction with confocal laser scanning microscopy (CLSM) have been used for the characterization of momentum and mass transfer at the Institute of Environmental Process Engineering to evaluate microfluidic devices. The calculation of three-dimensional flow and concentration fields is possible with two-dimensional measurement data for common stationary cases. Streamlines out of velocity gradients and isosurfaces out of fields of the same concentration are providing a helpful impression of the performance of microdevices based on highly reliable measurement data. A quantitative analysis of the velocity and concentration fields allows the calculation of residence-time distribution and mixing quality, which enables the adjustment of microreactor geometries for the demands of chemical, and biochemical reactions.

  16. Efficacy of a parainfluenza virus 5 (PIV5-based H7N9 vaccine in mice and guinea pigs: antibody titer towards HA was not a good indicator for protection.

    Zhuo Li

    Full Text Available H7N9 has caused fatal infections in humans. A safe and effective vaccine is the best way to prevent large-scale outbreaks in the human population. Parainfluenza virus 5 (PIV5, an avirulent paramyxovirus, is a promising vaccine vector. In this work, we generated a recombinant PIV5 expressing the HA gene of H7N9 (PIV5-H7 and tested its efficacy against infection with influenza virus A/Anhui/1/2013 (H7N9 in mice and guinea pigs. PIV5-H7 protected the mice against lethal H7N9 challenge. Interestingly, the protection did not require antibody since PIV5-H7 protected JhD mice that do not produce antibody against lethal H7N9 challenge. Furthermore, transfer of anti-H7 serum did not protect mice against H7N9 challenge. PIV5-H7 generated high HAI titers in guinea pigs, however it did not protect against H7N9 infection or transmission. Intriguingly, immunization of guinea pigs with PIV5-H7 and PIV5 expressing NP of influenza A virus H5N1 (PIV5-NP conferred protection against H7N9 infection and transmission. Thus, we have obtained a H7N9 vaccine that protected both mice and guinea pigs against lethal H7N9 challenge and infection respectively.

  17. TR PIV Experimental Investigation on Bypass Transition Induced by a Cylinder Wake

    TANG Zhan-Qi; JIANG Nan


    @@ The process of laminar to turbulent transition induced by a cylinder wake is studied by time-resolved(TR)particle image velocimetry(PIV) in a water channel.The combination of multi-scale local-averaged structure function analysis with criteria is used to identify the generation of secondary transverse vortex structure andto track its evolution along the streamvise.At the beginning of transition,with the decent of cylinder wake vortex,the secondary vortex structure is induced near the vall.As the secondary vortex moves dovnstream,it is induced to lift up by the wake vortex,meanwhile they are diffused and dissipated.According to the method of spatial conditional average,a low-speedhump is found in the near-wallregion along the bypass transition zone,accompanied by a low-speed region in the free stream occupied by the vake vortex.With further downstream,the hump in the near-wall region becomes more and more obvious.At the later stage of transition zone,hairpin vortex can be seen by conditional-averaged low-pass filtered vorticity.The hairpin head is almost vertical to the wall with an inclination angle of about 90°,which is attributed to the additional lift-up behavior induced by wake vortex.It can be concluded that in the process of bypass transition,the wake vortex would not only induce the secondary vortex but also leaven its growth and evolution,resulting in the robust and rapidly growing hairpin vortex.%The process of laminar to turbulent transition induced by a cylinder wake is studied by time-resolved (TR)particle image velocimetry (PIV) in a water channel. The combination of multi-scale local-averaged structure function analysis with criteria is used to identify the generation of secondary transverse vortex structure and to track its evolution along the streamwise. At the beginning of transition, with the decent of cylinder wake vortex, the secondary vortex structure is induced near the wall. As the secondary vortex moves downstream, it is induced to lift

  18. Parâmetros de desempenho de dezesseis equipamentos de irrigação por pivô central Parameters of performance of sixteen center-pivot irrigation equipments

    Delvio Sandri


    Full Text Available O tempo de uso de sistemas de irrigação por pivô central pode resultar em alteração de suas características hidráulicas, necessitando de avaliações periódicas para manter a uniformidade de distribuição de água em níveis aceitáveis. Objetivou-se, neste trabalho, avaliar as condições de funcionamento e desempenho de dezesseis pivôs centrais, localizados em onze municípios de Goiás e no Distrito Federal. Estimou-se o coeficiente de uniformidade de Heermann & Hein - CUH e uniformidade de distribuição - CUD, variação da lâmina coletada em relação à projetada e os fatores que interferem no desempenho dos equipamentos. Dos pivôs avaliados, quatro (25% apresentaram CUH inadequado (The time of use of the center-pivot irrigation system may result in alteration of the hydraulic characteristics, frequent evaluations being needed to maintain the efficiency of water distribution at acceptable levels. The aim of this work was to evaluate the conditions of the use and the performance of sixteen center pivots, located in eleven municipal districts of Goiás State and Federal District, Brazil. The Heermann & Hein - CUH coefficient of uniformity and coefficient of distribution - CUD, variation between the collected and projected depth and verification of the main factors that influenced the performance were evaluated. Among the evaluated pivots, four (25% presented inadequate CUH (< 80% and three (18.75% presented inadequate CUD (< 70%. The average depth applied was higher than the projected in three and lower in thirteen pivots, with the difference higher than 10% in only one pivot. Most of the evaluated pivots need maintenance to solve the following problems: emitters with flow rate different from the flow considered appropriate for some intervals of the equipments; emitters totally or partially clogged or damaged; absence of suspension strings; damaged pressure regulators; leaks in several points and speed displacement different

  19. Validation of numerical simulation with PIV measurements for two anastomosis models.

    Zhang, Jun-Mei; Chua, Leok Poh; Ghista, Dhanjoo N; Zhou, Tong-Ming; Tan, Yong Seng


    Hemodynamics is widely believed to influence coronary artery bypass graft (CABG) stenosis. Although distal anastomosis has been extensively investigated, further studies on proximal anastomosis are still necessary, as the extent and initiation of the stenosis process may be influenced by the flow of the proximal anastomosis per se. Therefore, in this study, two models (i.e. 90 degrees and 135 degrees anastomotic models) were designed and constructed to simulate a proximal anastomosis of CABG for the left and right coronary arteries, respectively. Flow characteristics for these models were studied experimentally in order to validate the simulation results found earlier. PIV measurements were carried out on two Pyrex glass models, so that the disturbed flow (stagnation point, flow separation and vortex) found in both proximal anastomosis models using numerical simulation, could be verified. Consequently, a fair agreement between numerical and experimental data was observed in terms of flow characteristics, velocity profiles and wall shear stress (WSS) distributions under both steady and pulsatile flow conditions. The discrepancy was postulated to be due to the difference in detailed geometry of the physical and computational models, due to manufacturing limitations. It was not possible to reproduce the exact shape of the computational model when making the Pyrex glass model. The analysis of the hemodynamic parameters based on the numerical simulation study also suggested that the 135 degrees proximal anastomosis model would alleviate the potential of intimal thickening and/or atherosclerosis, more than that of a 90 degrees proximal anastomosis model, as it had a lower variation range of time-averaged WSS and the lower segmental average of WSSG.

  20. Experimental comparative study of doublet and triplet impinging atomization of gelled fuel based on PIV

    Yang, Jian-lu; Li, Ning; Weng, Chun-sheng


    Gelled propellant is promising for future aerospace application because of its combination of the advantages of solid propellants and liquid propellants. An effort was made to reveal the atomization properties of gelled fuel by particle image velocimetry (PIV) system. The gelled fuel which was formed by gasoline and Nano-silica was atomized using a like-doublet impingement injector and an axisymmetric like-triplet impingement injector. The orifice diameter and length of the nozzle used in this work were of 0.8mm, 4.8mm, respectively. In the impinging spray process, the impingement angles were set at 90° and 120°, and the injection pressures were of 0.50MPa and 1.00MPa. The distance from the exit of the orifice to the impingement point was fixed at 9.6mm. In this study, high-speed visualization and temporal resolution particle image velocimetry techniques were employed to investigate the impingement atomization characteristics. The experimental investigation demonstrated that a long narrow high speed droplets belt formed around the axis of symmetry in the like-doublet impinging atomization area. However, there was no obvious high-speed belt with impingement angle 2θ = 90° and two high-speed belts appeared with impingement angle 2θ = 120° in the like-doublet impingement spray field. The high droplet velocity zone of the like-doublet impingement atomization symmetrically distributed around the central axis, and that of the like-triplet impingement spray deflected to the left of the central axis - opposite of injector. Although the droplets velocity distribution was asymmetry of like-triplet impingement atomization, the injectors were arranged like axisymmetric conical shape, and the cross section of spray area was similar to a circle rather than a narrow rectangle like the like-doublet impingement atomization.

  1. Irrigant flow during photon-induced photoacoustic streaming (PIPS) using Particle Image Velocimetry (PIV).

    Koch, Jon D; Jaramillo, David E; DiVito, Enrico; Peters, Ove A


    This study aimed to compare fluid movements generated from photon-induced photoacoustic streaming (PIPS) and passive ultrasonic irrigation (PUI). Particle Image Velocimetry (PIV) was performed using 6-μm melamine spheres in water. Measurement areas were 3-mm-long sections of the canal in the coronal, midroot and apical regions for PIPS (erbium/yttrium-aluminium garnet (Er:YAG) laser set at 15 Hz with 20 mJ), or passive ultrasonic irrigation (PUI, non-cutting insert at 30% unit power) was performed in simulated root canals prepared to an apical size #30/0.04 taper. Fluid movement was analysed directly subjacent to the apical ends of ultrasonic insert or fiber optic tips as well as at midroot and apically. During PUI, measured average velocities were around 0.03 m/s in the immediate vicinity of the sides and tip of the ultrasonic file. Speeds decayed to non-measureable values at a distance of about 2 mm from the sides and tip. During PIPS, typical average speeds were about ten times higher than those measured for PUI, and they were measured throughout the length of the canal, at distances up to 20 mm away. PIPS caused higher average fluid speeds when compared to PUI, both close and distant from the instrument. The findings of this study could be relevant to the debriding and disinfecting stage of endodontic therapy. Irrigation enhancement beyond needle irrigation is relevant to more effectively eradicate microorganisms from root canal systems. PIPS may be an alternative approach due to its ability to create high streaming velocities further away from the activation source compared to ultrasonic activation.

  2. Aerodynamic drag of a transiting sphere by large-scale tomographic-PIV

    Terra, W.; Sciacchitano, A.; Scarano, F.


    A method is introduced to measure the aerodynamic drag of moving objects such as ground vehicles or athletes in speed sports. Experiments are conducted as proof-of-concept that yield the aerodynamic drag of a sphere towed through a square duct in stagnant air. The drag force is evaluated using large-scale tomographic PIV and invoking the time-average momentum equation within a control volume in a frame of reference moving with the object. The sphere with 0.1 m diameter moves at a velocity of 1.45 m/s, corresponding to a Reynolds number of 10,000. The measurements in the wake of the sphere are conducted at a rate of 500 Hz within a thin volume of approximately 3 × 40 × 40 cubic centimeters. Neutrally buoyant helium-filled soap bubbles are used as flow tracers. The terms composing the drag are related to the flow momentum, the pressure and the velocity fluctuations and they are separately evaluated. The momentum and pressure terms dominate the momentum budget in the near wake up to 1.3 diameters downstream of the model. The pressure term decays rapidly and vanishes within 5 diameters. The term due to velocity fluctuations contributes up to 10% to the drag. The measurements yield a relatively constant value of the drag coefficient starting from 2 diameters downstream of the sphere. At 7 diameters the measurement interval terminates due to the finite length of the duct. Error sources that need to be accounted for are the sphere support wake and blockage effects. The above findings can provide practical criteria for the drag evaluation of generic bluff objects with this measurement technique.

  3. Development and Preliminary Application of High-Resolution Endoscopic Piv for Quantification of Flow Structure Within a Pore Space

    Blois, G.; Sambrook Smith, G.; Best, J.; Hardy, R.; Lead, J.


    Most natural rivers have beds of loose, cohesionless sediment that form a porous bed, thus permitting significant interactions between the free flow above the bed and that within the pore spaces. Many unresolved problems in channel engineering and ecohydraulics are related to an incomplete understanding of this interstitial flow. For example, the mechanisms of pollutant transport and prediction of river bed morphodynamics may be strongly influenced by flow occurring within the pore spaces. While this lack of understanding has been widely acknowledged, the direct experimental investigation of flow within the pore spaces has been restricted by the practical difficulties in collecting such data. This has also created drawbacks in the numerical modeling of pore flow as there remains a dearth of robust experimental data with which to validate such models. In order to help address these issues, we present details of a new endoscopic PIV system designed to tackle some of the challenges highlighted above. The work presented in this paper is also being used to validate a numerical model that is being developed as part of this project. A fully endoscopic PIV system has been developed to collect velocity and turbulence data for flow within the pore space of a gravel bed. The system comprises a pulsed Nd:YAG laser that provides high intensity illumination for single exposure pairs of images on a high-resolution digital camera. The use of rigid endoscopes for both the laser light source and camera allows measurement of quasi-instantaneous flow fields by high-resolution PIV images (2352*1728 pixels). In the first instance, the endoscopic PIV system has been used to study flow within an artificial pore space model constructed from 38 and 51 mm diameter spheres, used to represent a simplified version of a natural gravel-bed river. Across-correlation processing approach has been applied to the PIV images and the processing parameters have been optimized for the experimental

  4. PIV基准流场的评估分析%An analysis on the development of PIV benchmark flowfield test

    程素斌; 翟树成; 张怀新


    The benchmark flowfield test of PIV is the general standard of the normal flowfield test technol-ogy and the validation of test data. This paper discusses the construction method of basic flowfield by ana-lyzing the measurement technology development for PIV flowfield and its basic measurement technique. The CFD method is applied to evaluate the HTA and ITTC models preliminarily, and the flowflied results around the banchmark model are given to compare with the SPIV test results provided by HTA. The scheme design and the uncertainty analysis of PIV benchmark test are discussed in further detail. The analysis results could provide the basis for construction of the model standard and test standard.%  PIV基准流场是规范PIV流场测试技术和校验流场测试数据的统一标准。文章通过分析PIV流场测试技术的发展及其基准流场技术的发展状况,对PIV基准流场建设方法进行初步研究。应用CFD方法初步评估了HTA及ITTC的建议模型,给出了基准模型周围流场结果,并与HTA提供的SPIV试验测试结果进行比较分析,对PIV基准流场的方案设计和不确定度分析进行了进一步思考。分析结果为模型标准与测试标准的建设提供了基础。

  5. Experimental approach to investigate the dynamics of mixing coolant flow in complex geometry using PIV and PLIF techniques

    Hutli Ezddin


    Full Text Available The aim of this work is to investigate experimentally the increase of mixing phenomenon in a coolant flow in order to improve the heat transfer, the economical operation and the structural integrity of Light Water Reactors-Pressurized Water Reactors (LWRs-PWRs. Thus the parameters related to the heat transfer process in the system will be investigated. Data from a set of experiments, obtained by using high precision measurement techniques, Particle Image Velocimetry and Planar Laser-Induced Fluorescence (PIV and PLIF, respectively are to improve the basic understanding of turbulent mixing phenomenon and to provide data for CFD code validation. The coolant mixing phenomenon in the head part of a fuel assembly which includes spacer grids has been investigated (the fuel simulator has half-length of a VVER 440 reactor fuel. The two-dimensional velocity vector and temperature fields in the area of interest are obtained by PIV and PLIF technique, respectively. The measurements of the turbulent flow in the regular tube channel around the thermocouple proved that there is rotation and asymmetry in the coolant flow caused by the mixing grid and the geometrical asymmetry of the fuel bundle. Both PIV and PLIF results showed that at the level of the core exit thermocouple the coolant is homogeneous. The discrepancies that could exist between the outlet average temperature of the coolant and the temperature at in-core thermocouple were clarified. Results of the applied techniques showed that both of them can be used as good provider for data base and to validate CFD results.

  6. Influence of the velocity vector base relocation to the center of mass of the interrogation area on PIV accuracy

    Kouba Jan


    Full Text Available This paper is aimed at modification of calculation algorithm used in data processing from PIV (Particle Image Velocimetry method. The modification of standard Multi-step correlation algorithm is based on imaging the centre of mass of the interrogation area to define the initial point of the respective vector, instead of the geometrical centre. This paper describes the principle of initial point-vector assignment, the corresponding data processing methodology including the test track analysis. Both approaches are compared within the framework of accuracy in the conclusion. The accuracy test is performed using synthetic and real data.

  7. Engineering of a parainfluenza virus type 5 fusion protein (PIV-5 F): development of an autonomous and hyperfusogenic protein by a combinational mutagenesis approach.

    Terrier, O; Durupt, F; Cartet, G; Thomas, L; Lina, B; Rosa-Calatrava, M


    The entry of enveloped viruses into host cells is accomplished by fusion of the viral envelope with the target cell membrane. For the paramyxovirus parainfluenza virus type 5 (PIV-5), this fusion involves an attachment protein (HN) and a class I viral fusion protein (F). We investigated the effect of 20 different combinations of 12 amino-acid substitutions within functional domains of the PIV-5 F glycoprotein, by performing cell surface expression measurements, quantitative fusion and syncytia assays. We found that combinations of mutations conferring an autonomous phenotype with mutations leading to an increased fusion activity were compatible and generated functional PIV-5 F proteins. The addition of mutations in the heptad-repeat domains led to both autonomous and hyperfusogenic phenotypes, despite the low cell surface expression of the corresponding mutants. Such engineering approach may prove useful not only for deciphering the fundamental mechanism behind viral-mediated membrane fusion but also in the development of potential therapeutic applications.

  8. Antibody responses to allergen Lol pIV are suppressed following adoptive transfer of B lymphocytes from the internal image anti-idiotypic antibody-treated mice.

    Zhou, E M; Kisil, F T


    An internal image anti-idiotypic antibody, designated B1/1, was generated against an idiotope (Id91) of the monoclonal antibody (mAb91) specific for Lol pIV. The administration of B1/1 in PBS, at doses ranging from 100 ng to 100 micrograms/mouse, to syngeneic Balb/c mice resulted in the suppression of the formation of anti-Lol pIV antibodies that possessed the Id91. Spleen cells obtained from the mice 2 weeks after the treatment with B1/1 (25 micrograms/mouse) were adoptively transferred intravenously into the syngeneic recipients which were challenged intraperitoneally with Lol pIV in alum 2 hr after the transfer. The recipients were boosted with Lol pIV 14 days later. It was demonstrated that the transfer of splenic B cells (but not of T cells) from B1/1-treated donors induced a significant suppression of not only the level of IgE and IgG antibodies to Lol pIV, but also the level of antibodies possessing the Id91. Treatment of the B cells with mAb91 plus complement abrogated their ability to transfer the suppression. This study indicates that the treatment with the anti-Id B1/1 generated B cells that were characterized, serologically, as possessing the anti-Id-like antibodies on their surface and were responsible for transferring the suppression of the formation of antibodies to allergen Lol pIV and the expression of Id91.

  9. TR-PIV measurement of the wake behind a grooved cylinder at low Reynolds number

    Liu, Ying Zheng; Shi, Liu Liu; Yu, Jun


    A comparative study of the wakes behind cylinders with grooved and smooth surfaces was performed with a view to understand the wake characteristics associated with the adult Saguaro cacti. A low-speed recirculation water channel was established for the experiment; the Reynolds number, based on the free-stream velocity and cylinder diameter (D), was kept at ReD=1500. State-of-the-art time-resolved particle image velocimetry (TR-PIV) was employed to measure a total of 20 480 realizations of the wake field at a frame rate of 250 Hz, enabling a comprehensive view of the time- and phase-averaged wake pattern. In comparison to the wake behind the smooth cylinder, the length of the recirculation zone behind the grooved cylinder was extended by nearly 18.2%, yet the longitudinal velocity fluctuation intensity was considerably weakened. A global view of the peaked spectrum of the longitudinal velocity component revealed that the intermediate region for the grooved cylinder, which approximately corresponds to the transition region where the shear layer vortices interact, merge and shed before the formation of the Karman-like vortex street, was much wider than that for the smooth one. The unsteady events near St=0.3-0.4 were detected in the intermediate region behind the grooved cylinder, but no such events were found in the smooth cylinder system. Although the formation of the Karman-like vortex street was delayed by about 0.6D downstream for the grooved cylinder, no prominent difference in the vortex street region was found in the far wake for both cylinders. The Proper Orthogonal Decomposition (POD) method was used extensively to decompose the vector and swirling strength fields, which gave a close-up view of the vortices in the near wake. The first two POD modes of the swirling strength clarified the spatio-temporal characteristics of the shear layer vortices behind the grooved cylinder. The small-scale vortices superimposed on the shear layers behind the grooved cylinder

  10. The measurements of water flow rates in the straight microchannel based on the scanning micro-PIV technique

    Wang, H. L.; Han, W.; Xu, M.


    Measurement of the water flow rate in microchannel has been one of the hottest points in the applications of microfluidics, medical, biological, chemical analyses and so on. In this study, the scanning microscale particle image velocimetry (scanning micro-PIV) technique is used for the measurements of water flow rates in a straight microchannel of 200μm width and 60μm depth under the standard flow rates ranging from 2.481μL/min to 8.269μL/min. The main effort of this measurement technique is to obtain three-dimensional velocity distribution on the cross sections of microchannel by measuring velocities of the different fluid layers along the out-of-plane direction in the microchannel, so the water flow rates can be evaluated from the discrete surface integral of velocities on the cross section. At the same time, the three-dimensional velocity fields in the measured microchannel are simulated numerically using the FLUENT software in order to verify the velocity accuracy of measurement results. The results show that the experimental values of flow rates are well consistent to the standard flow rates input by the syringe pump and the compared results between numerical simulation and experiment are consistent fundamentally. This study indicates that the micro-flow rate evaluated from three-dimensional velocity by the scanning micro-PIV technique is a promising method for the micro-flow rate research.

  11. A translating stage system for µ-PIV measurements surrounding the tip of a migrating semi-infinite bubble.

    Smith, B J; Yamaguchi, E; Gaver, D P


    We have designed, fabricated and evaluated a novel translating stage system (TSS) that augments a conventional micro particle image velocimetry (µ-PIV) system. The TSS has been used to enhance the ability to measure flow fields surrounding the tip of a migrating semi-infinite bubble in a glass capillary tube under both steady and pulsatile reopening conditions. With conventional µ-PIV systems, observations near the bubble tip are challenging because the forward progress of the bubble rapidly sweeps the air-liquid interface across the microscopic field of view. The translating stage mechanically cancels the mean bubble tip velocity, keeping the interface within the microscope field of view and providing a tenfold increase in data collection efficiency compared to fixed-stage techniques. This dramatic improvement allows nearly continuous observation of the flow field over long propagation distances. A large (136-frame) ensemble-averaged velocity field recorded with the TSS near the tip of a steadily migrating bubble is shown to compare well with fixed-stage results under identical flow conditions. Use of the TSS allows the ensemble-averaged measurement of pulsatile bubble propagation flow fields, which would be practically impossible using conventional fixed-stage techniques. We demonstrate our ability to analyze these time-dependent two-phase flows using the ensemble-averaged flow field at four points in the oscillatory cycle.

  12. Planar Pressure Field Determination in the Initial Merging Zone of an Annular Swirling Jet Based on Stereo-PIV Measurements.

    Vanierschot, Maarten; Van den Bulck, Eric


    In this paper the static pressure field of an annular swirling jet is measured indirectly using stereo-PIV measurements. The pressure field is obtained from numerically solving the Poisson equation, taken into account the axisymmetry of the flow. At the boundaries no assumptions are made and the exact boundary conditions are applied. Since all source terms can be measured using stereo-PIV and the boundary conditions are exact, no assumptions other than axisymmetry had to be made in the calculation of the pressure field. The advantage of this method of indirect pressure measurement is its high spatial resolution compared to the traditional pitot probes. Moreover this method is non-intrusive while the insertion of a pitot tube disturbs the flow. It is shown that the annular swirling flow can be divided into three regimes: a low, an intermediate and a high swirling regime. The pressure field of the low swirling regime is the superposition of the pressure field of the non-swirling jet and a swirl induced pressure field due to the centrifugal forces of the rotating jet. As the swirl increases, the swirl induced pressure field becomes dominant and for the intermediate and high swirling regimes, the simple radial equilibrium equation holds.

  13. A hybrid experimental-numerical technique for determining 3D velocity fields from planar 2D PIV data

    Eden, A.; Sigurdson, M.; Mezić, I.; Meinhart, C. D.


    Knowledge of 3D, three component velocity fields is central to the understanding and development of effective microfluidic devices for lab-on-chip mixing applications. In this paper we present a hybrid experimental-numerical method for the generation of 3D flow information from 2D particle image velocimetry (PIV) experimental data and finite element simulations of an alternating current electrothermal (ACET) micromixer. A numerical least-squares optimization algorithm is applied to a theory-based 3D multiphysics simulation in conjunction with 2D PIV data to generate an improved estimation of the steady state velocity field. This 3D velocity field can be used to assess mixing phenomena more accurately than would be possible through simulation alone. Our technique can also be used to estimate uncertain quantities in experimental situations by fitting the gathered field data to a simulated physical model. The optimization algorithm reduced the root-mean-squared difference between the experimental and simulated velocity fields in the target region by more than a factor of 4, resulting in an average error less than 12% of the average velocity magnitude.

  14. Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study

    Burley, Casey L.; Brooks, Thomas F.; vanderWall, Berend; Richard, Hughes; Raffel, Markus; Beaumier, Philippe; Delrieux, Yves; Lim, Joon W.; Yu, Yung H.; Tung, Chee


    An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.

  15. Vortex dynamics in the near-wake of tabs with various geometries using 2D and 3D PIV

    Pagan-Vazquez, Axy; Khovalyg, Dolaana; Marsh, Charles; Hamed, Ali M.; Chamorro, Leonardo P.


    The vortex dynamics and turbulence statistics in the near-wake of rectangular, trapezoidal, triangular, and ellipsoidal tabs were studied in a refractive-index-matching channel at Re = 2000 and 13000, based on the tab height. The tabs share the same bulk dimensions including a 17 mm height, a 28 mm base width, and a 24.5o angle. 3D PIV was used to study the mean flow and dominant large-scale vortices, while high-spatial resolution planar PIV was used to quantify high-order statistics. The results show the coexistence of counter-rotating vortex pair (CVP) and hairpin structures. These vortices exhibit distinctive topology and strength across Re and tab geometry. The CVP is a steady structure that grows in strength over a significantly longer distance at the low Re due to the lower turbulence levels and the delayed shedding of the hairpin vortices. These features at the low Re are associated with the presence of K-H instability that develops over three tab heights. The interaction between the hairpins and CVP is measured in 3D for the first time and shows complex coexistence. Although the CVP suffers deformation and splitting at times, it maintains its presence and leads to significant spanwise and wall-normal flows.

  16. Quantitative analysis of surface deformation and ductile flow in complex analogue geodynamic models based on PIV method.

    Krýza, Ondřej; Lexa, Ondrej; Závada, Prokop; Schulmann, Karel; Gapais, Denis; Cosgrove, John


    Recently, a PIV (particle image velocimetry) analysis method is optical method abundantly used in many technical branches where material flow visualization and quantification is important. Typical examples are studies of liquid flow through complex channel system, gas spreading or combustion problematics. In our current research we used this method for investigation of two types of complex analogue geodynamic and tectonic experiments. First class of experiments is aimed to model large-scale oroclinal buckling as an analogue of late Paleozoic to early Mesozoic evolution of Central Asian Orogenic Belt (CAOB) resulting from nortward drift of the North-China craton towards the Siberian craton. Here we studied relationship between lower crustal and lithospheric mantle flows and upper crustal deformation respectively. A second class of experiments is focused to more general study of a lower crustal flow in indentation systems that represent a major component of some large hot orogens (e.g. Bohemian massif). The most of simulations in both cases shows a strong dependency of a brittle structures shape, that are situated in upper crust, on folding style of a middle and lower ductile layers which is influenced by rheological, geometrical and thermal conditions of different parts across shortened domain. The purpose of PIV application is to quantify material redistribution in critical domains of the model. The derivation of flow direction and calculation of strain-rate and total displacement field in analogue experiments is generally difficult and time-expensive or often performed only on a base of visual evaluations. PIV method operates with set of images, where small tracer particles are seeded within modeled domain and are assumed to faithfully follow the material flow. On base of pixel coordinates estimation the material displacement field, velocity field, strain-rate, vorticity, tortuosity etc. are calculated. In our experiments we used velocity field divergence to

  17. Planar time-resolved PIV for velocity and pressure retrieval in atmospheric boundary layer over surface waves.

    Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Bopp, Maximilian; Caulliez, Guillemette


    Air-sea coupling in general is important for weather, climate, fluxes. Wind wave source is crucially important for surface waves' modeling. But the wind-wave growth rate is strongly uncertain. Using direct measurements of pressure by wave-following Elliott probe [1] showed, weak and indefinite dependence of wind-wave growth rate on the wave steepness, while Grare [2] discuss the limitations of direct measurements of pressure associated with the inability to measure the pressure close to the surface by contact methods. Recently non-invasive methods for determining the pressure on the basis of technology of time-resolved PIV are actively developed [3]. Retrieving air flow velocities by 2D PIV techniques was started from Reul et al [4]. The first attempt for retrieving wind pressure field of waves in the laboratory tank from the time-resolved PIV measurements was done in [5]. The experiments were performed at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m). For 18 regimes with wind speed up to 14 m/s including presence of puddle waves, a combination of time resolved PIV technique and optical measurements of water surface form was applied to detailed investigation of the characteristics of the wind flow over the water surface. Ammonium chloride smoke was used for flow visualization illuminated by two 6 Wt blue diode lasers combined into a vertical laser plane. Particle movement was captured with high-speed camera using Scheimpflug technique (up to 20 kHz frame rate with 4-frame bursts, spatial resolution about 190 μm, field of view 314x12 mm). Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave form. The resulting time resolved instantaneous velocity fields on regular grid allowed us to obtain momentum fluxes directly from measured air velocity fluctuations. The average wind velocity patterns were

  18. Application of Powell's analogy for the prediction of vortex-pairing sound in a low-Mach number jet based on time-resolved planar and tomographic PIV

    Violato, D.; Bryon, K.; Moore, P.; Scarano, F.


    This paper describes an experimental investigation by time-resolved planar and tomographic PIV on the sound production mechanism of vortex pairing of a transitional water-jet flow at Re=5000. The shear layer is characterized by axisymmetric vortex rings which undergo pairing with a varicose mode.

  19. PIV Study of the Effect of Piston Motion on the Confined Swirling Flow in the Scavenging Process in 2-Stroke Marine Diesel Engines

    Haider, Sajjad; Meyer, Knud Erik; Schramm, Jesper


    The effect of piston motion on the incylinder swirling flow for a low speed, large two-stroke marine diesel engine is studies using the stereoscopic PIV technique. The measuremenrs are conducted at 5 cross sectional planes along the cylinder length and at piston positions covering the air intake...

  20. Application of Powell's analogy for the prediction of vortex-pairing sound in a low-Mach number jet based on time-resolved planar and tomographic PIV

    Violato, D.; Bryon, K.; Moore, P.; Scarano, F.


    This paper describes an experimental investigation by time-resolved planar and tomographic PIV on the sound production mechanism of vortex pairing of a transitional water-jet flow at Re=5000. The shear layer is characterized by axisymmetric vortex rings which undergo pairing with a varicose mode. Th

  1. Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV

    Elbaz, Ayman M.


    Most previous work on inverse diffusion flames (IDFs) has focused on laminar IDF emissions and the soot formation characteristics. Here, we investigate the characteristics and structure of methane IDFs using high speed planar laser-induced fluorescence (PLIF) images of OH, particle image velocimetry (PIV), and acetone PLIF imaging for non-reacting cases. First, the flame appearance was investigated with fixed methane loading (mass flux) but with varying airflow rates, yielding a central air jet Reynolds number (Re) of 1,000 to 6,000 (when blow-off occurs). Next, it was investigated a fixed central air jet Re of 4500, but with varied methane mass flux such that the global equivalence ratio spanned 0.5 to 4. It was observed that at Re smaller than 2000, the inner air jet promotes the establishment of an inverse diffusion flame surrounded by a normal diffusion flame. However, when the Re was increased to 2500, two distinct zones became apparent in the flame, a lower entrainment zone and an upper mixing and combustion zone. 10 kHz OH-PLIF images, and 2D PIV allow the identification of the fate and spatial flame structure. Many flame features were identified and further analyzed using simple but effective image processing methods, where three types of structure in all the flames investigated here: flame holes or breaks; closures; and growing kernels. Insights about the rate of evolution of these features, the dynamics of local extinction, and the sequence of events that lead to re-ignition are reported here. In the lower entrainment zone, the occurrence of the flame break events is counterbalanced by closure events, and the edge propagation appears to control the rate at which the flame holes and closures propagate. The rate of propagation of holes was found to be statistically faster than the rate of closure. As the flames approach blow-off, flame kernels become the main mechanism for flame re-ignition further downstream. The simultaneous OH-PLIF/Stereo PIV

  2. 3-D flow characterization and shear stress in a stenosed carotid artery bifurcation model using stereoscopic PIV technique.

    Kefayati, Sarah; Poepping, Tamie L


    The carotid artery bifurcation is a common site of atherosclerosis which is a major leading cause of ischemic stroke. The impact of stenosis in the atherosclerotic carotid artery is to disturb the flow pattern and produce regions with high shear rate, turbulence, and recirculation, which are key hemodynamic factors associated with plaque rupture, clot formation, and embolism. In order to characterize the disturbed flow in the stenosed carotid artery, stereoscopic PIV measurements were performed in a transparent model with 50% stenosis under pulsatile flow conditions. Simulated ECG gating of the flowrate waveform provides external triggering required for volumetric reconstruction of the complex flow patterns. Based on the three-component velocity data in the lumen region, volumetric shear-stress patterns were derived.

  3. Acoustic radiation- and streaming-induced microparticle velocities determined by micro-PIV in an ultrasound symmetry plane

    Barnkob, Rune; Laurell, Thomas; Bruus, Henrik


    We present micro-PIV measurements of suspended microparticles of diameters from 0.6 um to 10 um undergoing acoustophoresis in an ultrasound symmetry plane in a microchannel. The motion of the smallest particles are dominated by the Stokes drag from the induced acoustic streaming flow, while the motion of the largest particles are dominated by the acoustic radiation force. For all particle sizes we predict theoretically how much of the particle velocity is due to radiation and streaming, respectively. These predictions include corrections for particle-wall interactions and ultrasonic thermoviscous effects, and they match our measurements within the experimental uncertainty. Finally, we predict theoretically and confirm experimentally that the ratio between the acoustic radiation- and streaming-induced particle velocities is proportional to the square of the particle size, the actuation frequency and the acoustic contrast factor, while it is inversely proportional to the kinematic viscosity.

  4. PIV quantification of the flow induced by an ultrasonic horn and numerical modeling of the flow and related processing times.

    Schenker, M C; Pourquié, M J B M; Eskin, D G; Boersma, B J


    The flow in a confined container induced by an ultrasonic horn is measured by Particle Image Velocimetry (PIV). This flow is caused by acoustic streaming and highly influenced by the presence of cavitation. The jet-like experimentally observed flow is compared with the available theoretical solution for a turbulent free round jet. The similarity between both flows enables a simplified numerical model to be made, whilst the phenomenon is very difficult to simulate otherwise. The numerical model requires only two parameters, i.e. the flow momentum and turbulent kinetic energy at the position of the horn tip. The simulated flow is used as a basis for the calculation of the time required for the entire liquid volume to pass through the active cavitation region.

  5. Selection of DC voltage magnitude using Fibonacci series for new hybrid asymmetrical multilevel inverter with minimum PIV

    M.R. Banaei


    Full Text Available Multilevel inverters are suggested to obtain high quality output voltage. In this paper, a new hybrid configuration is proposed, obtained by cascading one four switches H-bridge cell with a family of multilevel inverters. In addition, by the use of specific sequence for value of DC sources named Fibonacci series, asymmetrical topology of proposed inverter is introduced. Main advantages are that proposed inverter has least Peak Inverse Voltage (PIV than other conventional multilevel converters in both symmetric and asymmetric modes. Also, this topology doubles the number of output levels using only one cascaded four switches H-bridge cell. The PCI-1716 DAQ using PC has been used to generate switching pulses in experimental results. For presenting valid performance of proposed configuration, simulation results carried out by MATLAB/SIMULINK software and the validity of the proposed multilevel inverter is verified by experimental results.

  6. 三维PIV原理及其实现方法%Principle and technology of three-dimensional PIV

    陈钊; 郭永彩; 高潮



  7. Validation of a numerical 3-D fluid-structure interaction model for a prosthetic valve based on experimental PIV measurements.

    Guivier-Curien, Carine; Deplano, Valérie; Bertrand, Eric


    A numerical 3-D fluid-structure interaction (FSI) model of a prosthetic aortic valve was developed, based on a commercial computational fluid dynamics (CFD) software program using an Arbitrary Eulerian Lagrangian (ALE) formulation. To make sure of the validity of this numerical model, an equivalent experimental model accounting for both the geometrical features and the hydrodynamic conditions was also developed. The leaflet and the flow behaviours around the bileaflet valve were investigated numerically and experimentally by performing particle image velocimetry (PIV) measurements. Through quantitative and qualitative comparisons, it was shown that the leaflet behaviour and the velocity fields were similar in both models. The present study allows the validation of a fully coupled 3-D FSI numerical model. The promising numerical tool could be therefore used to investigate clinical issues involving the aortic valve.

  8. Simultaneous PIV/PLIF measurements of Richtmyer-Meshkov Instabilities from single- and multi-mode perturbed interfaces

    Mejia-Alvarez, Ricardo; Wilson, Brandon; Prestridge, Kathy; Extreme Fluids Team


    To support validation of RANS and LES codes for single-interface Richtmyer-Meshkov mixing, the Extreme Fluids Team at Los Alamos National Laboratory commissioned a Vertical Shock Tube. This facility has the capability of generating statistically stationary single- and multi-mode spatial perturbations on the fluid interface prior to shock-interface interaction. The present study focuses on comparing the evolution of shock-driven mixing under two different spatial perturbation conditions after interacting with a M = 1.2 shock wave. High resolution simultaneous PIV and PLIF are used for capturing 2D instantaneous realizations of velocity and density at different stages of the evolving interface. Multiple realizations of the flow at each one of these evolution stages are obtained to characterize the flow statistically. Also, a modal analysis via Singular Value Decomposition is performed on the density and velocity fields to elucidate the role of initial flow scales content on the transition to turbulent mixing.

  9. Velocity field measurement in gas-liquid metal two-phase flow with use of PIV and neutron radiography techniques

    Saito, Y.; Mishima, K. [Kyoto Univ. Kumatori, Research Reactor Institute, Osaka (Japan); Tobita, Y.; Suzuki, T. [O-arai Engineering Center, Power Reactor and Nuclear Fuel Development Corporation (Japan); Matsubayashi, M. [Japan Atomic Energy Institute, Tokai Research Establishment (Japan)


    Neutron radiography and PIV (Particle Image Velocimetry) techniques were applied to measurements of velocity field in gas-liquid metal two-phase flow. Visualization and measurements of two-phase flow were conducted using molten lead bismuth and nitrogen gas as working fluids and particles made of gold-cadmium (AuCd{sub 3}) inter-metallic alloy were employed as the tracer. Discrimination method between bubble and tracer images in two-phase flow was developed based on the {sigma}-scaling method. Time-averaged liquid velocity fields, gas velocity fields and void profile were calculated from discriminated images, respectively. From these measurements, the basic characteristics of gas-liquid metal two-phase mixture were clarified. (author)

  10. Turbulent kinetic energy budget in the boundary layer developing over an urban-like rough wall using PIV

    Blackman, Karin; Perret, Laurent; Calmet, Isabelle; Rivet, Cédric


    In the present work, a boundary layer developing over a rough-wall consisting of staggered cubes with a plan area packing density λp = 25% is studied within the wind tunnel using Particle Image Velocimetry (PIV) to investigate the Turbulent Kinetic Energy (TKE) budget. To access the full TKE budget, an estimation of the dissipation (ɛ) using both the transport equation of the resolved-scale kinetic energy and Large-Eddy (LE) PIV models based on the use of a subgrid-scale model following the methodology used in large-eddy simulations is employed. A low-pass filter, larger than the Taylor microscale, is applied to the data prior to the computation of the velocity gradients ensuring a clear cutoff in the inertial range where the models are valid. The presence of the cube roughness elements has a significant influence on the TKE budget due to the region of strong shear that develops over the cubes. The shear layer is shown to produce and dissipate energy, as well as transport energy through advection, turbulent transport, and pressure transport. The recirculation region that forms through the interaction of the shear layer and the canopy layer, which is the region below the height of the cube roughness, creates rapid longitudinal evolution of the mean flow thereby inducing weak production. Finally, through stochastic estimation of the conditional average, it is shown that localized regions of backscatter (energy transfer from unresolved to resolved scales) and forward scatter (energy transfer from resolved to unresolved scales) occur as a result of coherent vortical structures.

  11. Combination of CFD and PIV in Flow Field Study%PIV与BEM相结合的流场研究法

    洪方文; 赵峰; 周连第


    Combined computational fluid dynamics (CFD) and the fluid field measurement for flow field understanding is a new approach in hydrodynamics.In this paper,a combination of the boundary element method (BEM,one of CFD) and the particle image measure velocity (PIV) technique was presented.The flow field could be understood better by this way.An uniform flow field was calculated using this method,and proved its feasibility.Simultaneously,an example of angelfish water entry experiment was studied.A good result was obtained.%本文介绍一种PIV与BEM相结合的流场研究方法.PIV(ParticleImageVelocimetry)是一种现代流场测试技术,BEM(BoundaryElementMethod)是一种流行的CFD方法,所谓PIV和BEM相结合的方法,是利用流域内PIV测量的结果和BEM法的反过程估计出边界上流场相关量的值,进而估计出流域内其它点的速度值.这种方法可以很好地修正PIV的测量结果,减小它们的误差,同时还可以对测量失效区域的流场进行估计,增加流场信息,在文中它被应用到楔形体入水的PIV测量后处理中,取得了很好的效果.

  12. PIV and CFD studies on analyzing intragastric flow phenomena induced by peristalsis using a human gastric flow simulator.

    Kozu, Hiroyuki; Kobayashi, Isao; Neves, Marcos A; Nakajima, Mitsutoshi; Uemura, Kunihiko; Sato, Seigo; Ichikawa, Sosaku


    This study quantitatively analyzed the flow phenomena in model gastric contents induced by peristalsis using a human gastric flow simulator (GFS). Major functions of the GFS include gastric peristalsis simulation by controlled deformation of rubber walls and direct observation of inner flow through parallel transparent windows. For liquid gastric contents (water and starch syrup solutions), retropulsive flow against the direction of peristalsis was observed using both particle image velocimetry (PIV) and computational fluid dynamics (CFD). The maximum flow velocity was obtained in the region occluded by peristalsis. The maximum value was 9 mm s(-1) when the standard value of peristalsis speed in healthy adults (UACW = 2.5 mm s(-1)) was applied. The intragastric flow-field was laminar with the maximum Reynolds number (Re = 125). The viscosity of liquid gastric contents hardly affected the maximum flow velocity in the applied range of this study (1 to 100 mPa s). These PIV results agreed well with the CFD results. The maximum shear rate in the liquid gastric contents was below 20 s(-1) at UACW = 2.5 mm s(-1). We also measured the flow-field in solid-liquid gastric contents containing model solid food particles (plastic beads). The direction of velocity vectors was influenced by the presence of the model solid food particle surface. The maximum flow velocity near the model solid food particles ranged from 8 to 10 mm s(-1) at UACW = 2.5 mm s(-1). The maximum shear rate around the model solid food particles was low, with a value of up to 20 s(-1).

  13. Effect of burner geometry on swirl stabilized methane/air flames: A joint LES/OH-PLIF/PIV study

    Liu, X.


    Large eddy simulation (LES) using a transported PDF model and OH-PLIF/PIV experiments were carried out to investigate the quarl effects on the structures of swirl stabilized methane/air flames. Two different quarls were investigated, one straight cylindrical quarl and one diverging conical quarl. The experiments show that the flames are significantly different with the two quarls. With the straight cylindrical quarl a compact blue flame is observed while with the diverging conical quarl the flame appears to be long and yellow indicating a sooty flame structure. The PIV results show the formation of a stronger flow recirculation inside the diverging conical quarl than that in the straight quarl. LES results reveal further details of the flow and mixing process inside the quarl. The results show that with the diverging quarl vortex breakdown occurs much earlier towards the upstream of the quarl. As a result the fuel is convected into the air flow tube and a diffusion flame is stabilized inside the air flow tube upstream the quarl. With the straight quarl, vortex breakdown occurs at a downstream location in the quarl. The scalar dissipation rate in the shear layer of the fuel jet is high, which prevents the stabilization of a diffusion flame in the proximity of the fuel nozzle; instead, a compact partially premixed flame with two distinct heat release layers is stablized in a downstream region in the quarl, which allows for the fuel and air to mix in the quarl before combustion and a lower formation rate of soot. The results showed that the Eulerian Stochastic Fields transported PDF method can well predict the details of the swirl flame dynamics.

  14. Time-resolved Tomo-PIV measurements of the interaction between a stationary held sphere and a turbulent boundary layer.

    van Hout, Rene; Eisma, Jerke; Overmars, Edwin; Elsinga, Gerrit; Westerweel, Jerry


    Time resolved tomographic PIV measurements (acquisition rate 250Hz) were performed in a turbulent boundary layer (TBL) on the side wall of an open channel, water flow facility (cross section 60x60cm, Wx H) , 3.5m downstream of the inlet at a bulk flow velocity of Ub = 0.17m/s (Reb =Ub H / ν = 102x103, δ0 . 99 = 5 . 0 cm, Reθ = 891). The measurement volume was a horizontal slab (6x1.5x6cm3, lx wx h) extending from the side wall, 30cm above the bottom. The Tomo-PIV setup comprised four high-speed ImagerPro HS cameras (2016x2016pixels), a high-speed laser (Nd:YLF, Darwin Duo 80M, Quantronix), optics/prisms and data acquisition/processing software (LaVision, DaVis8.2). A sphere with diameter, D = 6mm (D+ = 51, ``+'' denotes inner wall scaling), was positioned at y = 37.5 and 5.4mm (y+ = 319 and 46) from the wall (measured from the sphere's center). The latter position covers most of the buffer layer while the former is well in the outer layer. Sphere Reynolds numbers based on D and the average streamwise velocity at the sphere's center were 984 (y+ = 319) and 684 (y+ = 46). Results show the interaction between the coherent turbulence structures in the TBL and those generated in the sphere's wake. Total and partial destruction of the log-law layer is observed when the sphere is positioned in the buffer and outer layer, respectively.

  15. 不同工作原理的PIV在紊流测量中的适应性分析%Adaptability of PIV based on different working principle to turbulence measurements

    胡江; 王兴奎; 杨胜发; 兰艳萍


    基于单脉冲和双脉冲两种PIV系统的不同工作原理和高精度水槽试验数据分析了其在紊流测量中的适应性、数据的统计分析方法以及对样本容量的要求.双脉冲PIV系统和频率高于100Hz的单脉冲PIV系统均适合于紊流的测量,频率低于50Hz的单脉冲PIV系统只适合于平均流速的测量.传统的三种紊流数据统计分析方法中,双脉冲PIV只适合于统计平均法,高频单脉冲PIV可采用时间平均和统计平均两种方法.在进行平均流速的测量时,两种PIV系统的样本容量在500以上即能满足要求.在进行均匀紊流紊动特性的研究时,单脉冲PIV样本容量在30000时已经足够;而双脉冲PIV采用3000个采样数据不能保证所获得成果均满足要求,需要3000个以上的样本才能获得较好的结果.%Adaptability of monopulse PIV and double-pulse PIV to turbulent flow measurements are analyzed in this paper, using experimental data of flows in a chute and considering the difference in PIV working principles, statistical methods of data processing, and their requirements for data sample size. Both double-pulse PIV and high-frequency monopulse PIV (higher than 100Hz) are fit for turbulence measurement. If its frequency is lower than 50Hz, monopulse PIV is fit for time-average velocity only. Among the three traditional methods for data processing, time-average method and statistical average method can be used for monopulse PIV data, while only the latter method can be used for double-pulse PIV data. In measurement of time-average velocity, both PIV systems perform well if sample size is over 500, while in measurement of turbulence characteristics, the size must be increased to at least 3,000 and 5,000 for monopulse PIV and double-pulse PIV, respectively.

  16. Series of isostructural planar lanthanide complexes [Ln(III)4(mu3-OH)2(mdeaH)2(piv)8] with single molecule magnet behavior for the Dy4 analogue.

    Abbas, Ghulam; Lan, Yanhua; Kostakis, George E; Wernsdorfer, Wolfgang; Anson, Christopher E; Powell, Annie K


    A series of five isostructural tetranuclear lanthanide complexes of formula [Ln(4)(mu(3)-OH)(2)(mdeaH)(2)(piv)(8)], (mdeaH(2) = N-methyldiethanolamine; piv = pivalate; Ln = Tb (1), Dy (2), Ho (3), Er (4), and Tm (5)) have been synthesized and characterized. These clusters have a planar "butterfly" Ln(4) core. Magnetically, the Ln(III) ions are weakly coupled in all cases; the Dy(4) compound 2 shows Single Molecule Magnet (SMM) behavior.

  17. In vitro confocal micro-PIV measurements of blood flow in a square microchannel: the effect of the haematocrit on instantaneous velocity profiles.

    Lima, Rui; Wada, Shigeo; Takeda, Motohiro; Tsubota, Ken-ichi; Yamaguchi, Takami


    A confocal microparticle image velocimetry (micro-PIV) system was used to obtain detailed information on the velocity profiles for the flow of pure water (PW) and in vitro blood (haematocrit up to 17%) in a 100-microm-square microchannel. All the measurements were made in the middle plane of the microchannel at a constant flow rate and low Reynolds number (Re=0.025). The averaged ensemble velocity profiles were found to be markedly parabolic for all the working fluids studied. When comparing the instantaneous velocity profiles of the three fluids, our results indicated that the profile shape depended on the haematocrit. Our confocal micro-PIV measurements demonstrate that the root mean square (RMS) values increase with the haematocrit implying that it is important to consider the information provided by the instantaneous velocity fields, even at low Re. The present study also examines the potential effect of the RBCs on the accuracy of the instantaneous velocity measurements.

  18. 3D PIV measurements of the EHD flow patterns in a narrow lectrostatic precipitator with wire-plate or wire-flocking electrodes

    Podliński, J.; Kocik, M.; Barbucha, R.; Niewulis, A.; Mizeraczyk, J.; Mizuno, A.


    The results of 3-dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) flow patterns in a narrow electrostatic precipitator (ESP) are presented in this paper. The ESP was an acrylic parallelepiped with a wire discharge electrode and two plane collecting electrodes. In contrary to typical ESPs the wire electrode was placed along the gas flow, in the ESP centre, in the halfway between collecting electrodes. Either two smooth stainless steel plates or two stainless steel meshes with nylon flocks were used as the collecting electrodes. They were placed on the top and bottom of the ESP. The PIV measurements were carried out in two parallel planes, placed perpendicularly to the collecting electrodes and parallel to the wire electrode. The obtained results showed some similarities and differences of a 3D particle flow in the ESP with plate or flocking electrodes.

  19. Phase-locked stereoscopic PIV measurements of the turbulent swirling flow in a dynamic model of a uniflow-scavenged two-stroke engine cylinder

    Ingvorsen, Kristian Mark; Meyer, Knud Erik; Walther, Jens Honore


    turbulence models. In the present work, the flow in a dynamic scale model of a uniflow-scavenged cylinder is investigated experimentally. The model has a transparent cylinder and a movable piston driven by a linear motor. The flow is investigated using phase-locked stereoscopic particle image velocimetry......It is desirable to use computational fluid dynamics for the optimization of in-cylinder processes in large two-stroke low-speed uniflowscavenged marine diesel engines. However, the complex nature of the turbulent swirling in-cylinder flow necessitates experimental data for validation of the used...... (PIV) and time resolved laser Doppler anemometry (LDA). Radial profiles of the phase-averaged mean velocities are computed from the velocity fields recorded with PIV and the validity of the obtained profiles is demonstrated by comparison with reference LDA measurements. Radial profiles are measured...


    QU Jian-wu; MURAI Yuichi; YAMAMOTO Fujio


    A Particle Image Velocimetry (PIV) method based on the image separation and reconstruction with the median filter and triangular Bézier patch was proposed to measure multiple velocity fields from single-camera images in the present study. The method was examined on synthetic PIV images with the Green-Taylor two-phase vortex flows and the test results showed high accuracy and highly correct tracking percent compared with the exact solution. An experiment of the bubbly jet flow was also conducted as a practical demonstration of the present method. As a result, it is confirmed from the simulation image examination and the experimental measurement that the proposed method shows a good performance in the measurement of bubble and particle phases.

  1. 3D flow organization and dynamics in subsonic jets: Aeroacoustic source analysis by tomographic PIV

    Violato, D.V.


    To meet the increasingly stringent noise regulation, aircraft manufacturers are searching for solutions to jet noise. This, which constitutes a significant amount of the total noise emitted by civil aircrafts, is generated by the mixing processes between the exhaust flow leaving the engine and the a

  2. PIV系统CCD相机位移调整机构的设计%Design of CCD Camera Displacement Adjusting Mechanism for PIV System

    王成军; 江平


    In order to have a higher reliability,accuracy and stability in flow field test for 2D Particle Image Velocimetry (PIV) system,the CCD camera displacement adjusting mechanism was designed,according to the PIV system requirements and the function of flow field test working environment,then the structural design thought,composition,and capable functions achieved and its charac-teristics were expounded.Through the use of the mechanism for the flow field test,the result shows that using of the CCD camera dis-placement adjusting mechanism,can very well satisfy the job needs of PIV system in flow field test,while makes the whole system more simple,stable and efficient,and further makes flow field test results more reliable and accurate.%为使PIV (Particle Image Velocimetry)系统在流场测试中具有更高的可靠性、准确性和稳定性,根据PIV流场试验对CCD相机安装要求和工作环境的需求,设计了CCD相机位移调整机构,并阐述了该机构的设计思路、组成、能实现的功能及其特点。通过使用该机构进行流场试验,结果表明:采用该CCD相机位移调整机构,能很好地满足PIV系统在流场测试试验中的工作需要,使整个系统更加简单、稳定、高效,进而使流场测试结果更加可靠、准确。

  3. PIV Application in Flow Measurement within Chemical Stirred Tank%PIV在化工搅拌釜内流动测量中的应用

    杨斌; 高凯; 淡勇


    着重探讨了新一代全场光学测速技术——粒子图像速度场仪(PIV)在搅拌混合实验中的应用,指出PIV及其衍生的测速技术在搅拌混合实验研究中具有广泛应用前景.PIV流场测量结果兼具很高的空间分辨率和时间解析度,可以得到搅拌釜中混合流体的瞬时2D或3D速度场以及浓度场等信息,进行非定常湍流特性研究,有助于建立搅拌釜内多相流动模型,揭示搅拌混合作用机理,优化搅拌桨型设计,促进搅拌混合技术的进一步发展.%Particle image velocimetry (PIV) was introduced, which has great application in the experimental study on mixing flow in a stirred tank. PIV has higher space-resolution and time-resolution. Based on PIV, 2D or 3D instant velocity fields and the mixing flow' s density field can be obtained to benefit the research of unsteady turbulent characteristics, the building of multi-phase flow model, the revealing of stirred autoclave' s mixing mechanism and the optimization of mixing paddle design as well as the promotion of further development of the mixing technology.

  4. Characterization of the activity of ultrasound emitted in a perpendicular liquid flow using Particle Image Velocimetry (PIV) and electrochemical mass transfer measurements.

    Barthès, Magali; Mazue, Gerald; Bonnet, Dimitri; Viennet, Remy; Hihn, Jean-Yves; Bailly, Yannick


    The present work is dedicated to the study of the interactions between a liquid circulation and a perpendicular acoustic wave propagation. A specific experimental setup was designed to study one transducer operating at 20 kHz, with the help of electrochemical mass transfer measurements combined with Particle Image Velocimetry (PIV) determination. Electrodes were located on the wall opposite to the acoustic emission. Experiments were performed for various Reynolds numbers: from 0 to 21700 (different liquid flow rates and viscosities). Both PIV and electrochemical measurements methods were found to be relevant, and had delivered complementary information. Even if PIV showed that the plume due to streaming was highly deflected by the additional flow, electrochemical measurements showed that there was still an activity, higher than in silent conditions, on the wall facing the transducer. Thus the ultrasound contribution remained noticeable on the surface opposite to the transducer even for a disturbed hydrodynamic environment due to the presence of a liquid circulation perpendicular to the wave propagation.

  5. An experimental method for evaluating the PIV measurement error and its application in optimizing PIV experiment parameters%PIV系统测量误差的实验评价方法以及实验参数的优化

    董明哲; 汪洋; 蒋宁涛


    提出了一种PIV(Particle Image Velocimetry)测量误差的实验评价方法:利用匀速转动圆盘上粒子的反射光模拟流场中示踪粒子散射光解决基准速度场.建立了一套二维PIV系统的测量误差评价系统,利用该系统对PIV测量误差和测量精度进行了实验评价,得到了结果误差在空间及时间上的概率分布特性,并对两个关键PIV实验参数进行了优化.实验表明该误差评价方法装置简单,方法可靠,可方便灵活地对PIV系统测量误差和测量精度进行实验评价和参数优化研究.

  6. Comparative study of PIV and LDV measurements in the wake of a propeller%PIV, LDV在螺旋桨尾流测试中的比对应用

    李广年; 张军; 陆林章; 张国平



  7. Time-resolved and time-averaged stereo-PIV measurements of a unit-ratio cavity

    Immer, Marc; Allegrini, Jonas; Carmeliet, Jan


    An experimental setup was developed to perform wind tunnel measurements on a unit-ratio, 2D open cavity under perpendicular incident flow. The open cavity is characterized by a mixing layer at the cavity top, that divides the flow field into a boundary layer flow and a cavity flow. Instead of precisely replicating a specific type of inflow, such as a turbulent flat plate boundary layer or an atmospheric boundary layer, the setup is capable of simulating a wide range of inflow profiles. This is achieved by using triangular spires as upstream turbulence generators, which can modify the otherwise laminar inflow boundary layer to be moderately turbulent and stationary, or heavily turbulent and intermittent. Measurements were performed by means of time-resolved stereo PIV. The cavity shear layer is analyzed in detail using flow statistics, spectral analysis, and space-time plots. The ability of the setup to generate typical cavity flow cases is demonstrated for characteristic inflow boundary layers, laminar and turbulent. Each case is associated with a distinct shear layer flow phenomena, self-sustained oscillations for the former and Kelvin-Helmholtz instabilities for the latter. Additionally, large spires generate a highly turbulent wake flow, resulting in a significantly different cavity flow. Large turbulent sweep and ejection events in the wake flow suppress the typical shear layer and sporadic near wall sweep events generate coherent vortices at the upstream edge.

  8. PIV measurements of in-cylinder, large-scale structures in a water-analogue Diesel engine

    Kalpakli Vester, A.; Nishio, Y.; Alfredsson, P. H.


    Swirl and tumble are large-scale structures that develop in an engine cylinder during the intake stroke. Their structure and strength depend on the design of the inlet ports and valves, but also on the valve lift history. Engine manufacturers make their design to obtain a specific flow structure that is assumed to give the best engine performance. Despite many efforts, there are still open questions, such as how swirl and tumble depend on the dynamics of the valves/piston as well as how cycle-to-cycle variations should be minimized. In collaboration with Swedish vehicle industry we perform PIV measurements of the flow dynamics during the intake stroke inside a cylinder of a water-analogue engine model having the same geometrical characteristics as a typical truck Diesel engine. Water can be used since during the intake stroke the flow is nearly incompressible. The flow from the valves moves radially outwards, hits the vertical walls of the cylinder, entrains surrounding fluid, moves along the cylinder walls and creates a central backflow, i.e. a tumble motion. Depending on the port and valve design and orientation none, low, or high swirl can be established. For the first time, the effect of the dynamic motion of the piston/valves on the large-scale structures is captured. Supported by the Swedish Energy Agency, Scania CV AB and Volvo GTT, through the FFI program.

  9. Comparison between two and three-dimensional POD in a turbulent boundary layer using multi-plane stereoscopic PIV

    Liberzon, Alex; Gurka, Roi; Hetsroni, Gad


    A comparison between two- and three-dimensional analyses using proper orthogonal decomposition (POD) is performed. The investigated flow field is a turbulent boundary layer in a flume. The decomposition is applied to the vorticity fields measured using a multi-plane stereoscopic particle image velocimetry (PIV) measurement system. The decomposition was applied using two methods: A) two-dimensional slices of the data that were used separately in a so-called slice-POD, and B) as a volumetric dataset that provides 3D-POD modes. Linear combination of the first three modes, energy distribution and reconstruction of snapshots are compared. Both decompositions capture most of the turbulent flow patterns; yet, the lower order modes show significant discrepancies between the slice-POD and 3D-POD. Therefore, in order to characterize coherent structures in turbulent flows, it is essential to perform both two- and three-dimensional decompositions. These two methods complement each other and can provide an improved interpretation of various flow features.

  10. Comparison between two and three-dimensional POD in a turbulent boundary layer using multi-plane stereoscopic PIV

    Liberzon, Alex [School of Mechanical Engineering, Tel Aviv University, Ramat Aviv 69978 (Israel); Gurka, Roi [Department of Chemical Engineering, Ben Gurion University of the Negev, Beer Sheva (Israel); Hetsroni, Gad, E-mail: [Faculty of Mechanical Engineering, Technion, Haifa 32000 (Israel)


    A comparison between two- and three-dimensional analyses using proper orthogonal decomposition (POD) is performed. The investigated flow field is a turbulent boundary layer in a flume. The decomposition is applied to the vorticity fields measured using a multi-plane stereoscopic particle image velocimetry (PIV) measurement system. The decomposition was applied using two methods: A) two-dimensional slices of the data that were used separately in a so-called slice-POD, and B) as a volumetric dataset that provides 3D-POD modes. Linear combination of the first three modes, energy distribution and reconstruction of snapshots are compared. Both decompositions capture most of the turbulent flow patterns; yet, the lower order modes show significant discrepancies between the slice-POD and 3D-POD. Therefore, in order to characterize coherent structures in turbulent flows, it is essential to perform both two- and three-dimensional decompositions. These two methods complement each other and can provide an improved interpretation of various flow features.

  11. PIV measurements of the turbulence integral length scale on cold combustion flow field of tangential firing boiler

    Wu, Wen-fei; Xie, Jing-xing; Gong, Zhi-jun; Li, Bao-wei [Inner Mongolia Univ. of Science and Technology, Baotou (China). Inner Mongolia Key Lab. for Utilization of Bayan Obo Multi-Metallic Resources: Elected State Key Lab.


    The process of the pulverized coal combustion in tangential firing boiler has prominent significance on improving boiler operation efficiency and reducing NO{sub X} emission. This paper aims at researching complex turbulent vortex coherent structure formed by the four corners jets in the burner zone, a cold experimental model of tangential firing boiler has been built. And by employing spatial correlation analysis method and PIV (Particle Image Velocimetry) technique, the law of Vortex scale distribution on the three typical horizontal layers of the model based on the turbulent Integral Length Scale (ILS) has been researched. According to the correlation analysis of ILS and the temporal average velocity, it can be seen that the turbulent vortex scale distribution in the burner zone of the model is affected by both jet velocity and the position of wind layers, and is not linear with the variation of jet velocity. The vortex scale distribution of the upper primary air is significantly different from the others. Therefore, studying the ILS of turbulent vortex integral scale is instructive to high efficiency cleaning combustion of pulverized coal in theory.

  12. Development of a towing tank PIV system and a wake survey of a marine current turbine under steady conditions

    Lust, Ethan; Luznik, Luksa; Flack, Karen


    A submersible particle image velocimetry (PIV) system was designed and built at the U.S. Naval Academy. The system was used to study the wake of a scale-independent horizontal axis marine current turbine. The turbine is a 1/25th scale model of the U.S. National Renewable Energy Laboratory's Reference Model 1 (RM1) tidal turbine. It is a two-bladed turbine measuring 0.8 m in diameter and featuring a NACA 63-618 airfoil cross-section. The wake survey was conducted over an area extending 0.25D forward of the turbine tip path to 2.0D aft to a depth of 1.0D beneath the turbine output shaft in the streamwise plane. Each field of view was approximately 30 cm by 30 cm, and each overlapped the adjacent fields of view by 5 cm. The entire flow field was then reconstructed by registering the resultant vector fields together into a single field of investigation. Results include the field of investigation from a representative case, for the mean velocity field averaged over approximately 1,000 realizations, and turbulent statistics including turbulence intensities, Reynolds shear stresses, and turbulent kinetic energy. This research was funded by the Office of Naval Research.

  13. Cavitation on a scaled-down model of a Francis turbine guide vane: high-speed imaging and PIV measurements

    Pervunin, K. S.; Timoshevskiy, M. V.; Churkin, S. A.; Kravtsova, A. Yu; Markovich, D. M.; Hanjalić, K.


    Cavitation on two symmetric foils, a NACA0015 hydrofoil and a scaled-down model of a Francis turbine guide vane (GV), was investigated by high-speed visualization and PIV. At small attack angles the differences between the profiles of the mean and fluctuating velocities for both hydrofoils were shown to be insignificant. However, at the higher angle of incidence, flow separation from the GV surface was discovered for quasi-steady regimes including cavitation-free and cavitation inception cases. The flow separation leads to the appearance of a second maximum in velocity fluctuations distributions downstream far from the GV surface. When the transition to unsteady regimes occurred, the velocity distributions became quite similar for both foils. Additionally, for the GV an unsteady regime characterized by asymmetric spanwise variations of the sheet cavity length along with alternating periodic detachments of clouds between the sidewalls of the test channel was for the first time visualized. This asymmetric behaviour is very likely to be governed by the cross instability that was recently described by Decaix and Goncalvès [8]. Moreover, it was concluded that the existence of the cross instability is independent on the test body shape and its aspect ratio.

  14. Flow visualization of a monoleaflet and bileaflet mechanical heart valve in a pneumatic ventricular assist device using a PIV system.

    Lee, Hwansung; Tatsumi, Eisuke; Taenaka, Yoshiyuki


    Our group is developing a new type of pulsatile pneumatic ventricular assist device (PVAD) that uses the Medtronic Hall tilting disc valve (M-H valve). Although tilting disc valves have good washout effect inside the blood pump, they are no longer in common clinical use and may be difficult to obtain in the future. To investigate the stability of the Sorin Bicarbon valve (S-B valve) in our PVAD, we constructed a model pump made of an acrylic resin with the same configuration as our PVAD and attempted to compare the flow visualization upstream and downstream of the outlet position valve between the M-H valve and the S-B valve using a particle image velocimetry (PIV) method. The outlet S-B valve had faster closure than the M-H valve. The maximum flow velocity was greater than with the M-H valve. The maximum Reynolds shear stress (RSS) of the M-H valve reached 150 N/m(2) and that of the S-B valve reached 300 N/m(2) upstream during the end-systolic and early-diastolic phases. In both valves, the maximum RSS upstream of the valve was higher than downstream of the valve because of the regurgitation flow during valve closure. In addition, the maximum viscous shear stress reached above 2 N/m(2), which occupied only about 1%-1.5% of the maximum RSS.

  15. 3D flow study in a mildly stenotic coronary artery phantom using a whole volume PIV method.

    Brunette, J; Mongrain, R; Laurier, J; Galaz, R; Tardif, J C


    Blood flow dynamics has an important role in atherosclerosis initiation, progression, plaque rupture and thrombosis eventually causing myocardial infarction. In particular, shear stress is involved in platelet activation, endothelium function and secondary flows have been proposed as possible variables in plaque erosion. In order to investigate these three-dimensional flow characteristics in the context of a mild stenotic coronary artery, a whole volume PIV method has been developed and applied to a scaled-up transparent phantom. Experimental three-dimensional velocity data was processed to estimate the 3D shear stress distributions and secondary flows within the flow volume. The results show that shear stress reaches values out of the normal and atheroprotective range at an early stage of the obstructive pathology and that important secondary flows are also initiated at an early stage of the disease. The results also support the concept of a vena contracta associated with the jet in the context of a coronary artery stenosis with the consequence of higher shear stresses in the post-stenotic region in the blood domain than at the vascular wall.

  16. A PIV Approach Based on Nonlinear Filtering%基于非线性滤波方法的PIV计算

    卢宗庆; 廖庆敏; 裴继红



  17. PIV测量舰船空气尾流场%PIV measurements of the warship air-wake




  18. Time Resolved PIV Investigation on the Skin Friction Reduction Mechanism of Outer-Layer Vertical Blades Array

    Seong Hyeon Park


    Full Text Available The drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins (2003, have been demonstrated by the recent towing tank measurements. From the drag measurement of flat plate with various vertical blades arrays by Park et al. (2011, a maximum 9.6% of reduction of total drag was achieved. The scale of blade geometry is found to be weakly correlated with outer variable of boundary layer. The drag reduction of 2.8% has been also confirmed by the model ship test by An et al. (2014. With a view to enabling the identification of drag reduction mechanism of the outer-layer vertical blades, detailed flow field measurements have been performed using 2D time resolved PIV in this study. It is found that the skin friction reduction effect is varied according to the spanwise position, with 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. The influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by POD method. It is observed that the vortical structures are cut and deformed by blades array and the skin frictional reduction is closely associated with the subsequent evolution of turbulent structures.

  19. Aero-acoustics in a tangential blower: validation of the CFD flow distribution using advanced PIV techniques

    Jean-Yves Noël


    Full Text Available Noise reduction is of increasing importance in the community. Consequently, the development of aero-acoustics is gaining special focus within industry. Computational Aero-Acoustics (CAA, the coupling of Computational Fluid Dynamics (CFD and Computational Acoustics (CA, is being used in the design and assessment of a range of products from HVAC ducts to domestic appliances. The process for carrying out an Aero-Acoustic simulation begins with the solution of the transient flow dynamics in order to compute accurately the pressure fluctuations at a number of points in the computational domain. These fluctuations are passed to the acoustic code to propagate the acoustic waves through the system and determine its acoustic signature. To minimize errors in the acoustic propagation analysis it is thus essential that accurate predictions of the noise sources be obtained. This paper concentrates on the CFD part of the aero-acoustic simulation. The case considered has been taken from the European project DESTINY:3 and comprises a tangential blower located inside a complex duct system. Air is drawn into the fan through two inlets and exits through a single duct. The computational methodology and flow field predictions are presented and compared to experimental PIV data. The numerical predictions were found to be in good agreement with the experimental data, reproducing the asymmetries in the flow field.

  20. Application of photogrammetry to transforming PIV-acquired velocity fields to a moving-body coordinate system

    Nikoueeyan, Pourya; Naughton, Jonathan


    Particle Image Velocimetry is a common choice for qualitative and quantitative characterization of unsteady flows associated with moving bodies (e.g. pitching and plunging airfoils). Characterizing the separated flow behavior is of great importance in understanding the flow physics and developing predictive reduced-order models. In most studies, the model under investigation moves within a fixed camera field-of-view, and vector fields are calculated based on this fixed coordinate system. To better characterize the genesis and evolution of vortical structures in these unsteady flows, the velocity fields need to be transformed into the moving-body frame of reference. Data converted to this coordinate system allow for a more detailed analysis of the flow field using advanced statistical tools. In this work, a pitching NACA0015 airfoil has been used to demonstrate the capability of photogrammetry for such an analysis. Photogrammetry has been used first to locate the airfoil within the image and then to determine an appropriate mask for processing the PIV data. The photogrammetry results are then further used to determine the rotation matrix that transforms the velocity fields to airfoil coordinates. Examples of the important capabilities such a process enables are discussed. P. Nikoueeyan is supported by a fellowship from the University of Wyoming's Engineering Initiative.

  1. The Measurements of Water Flow Rate in the T-shape Microchannels Based on the Scanning Micro-PIV Technique

    Han, W.; Wang, H. L.; Xu, M.


    In this study, the scanning microfluidic particle image velocimetry (scanning micro-PIV) technique is used to measure the water flow rate in a T-shape microchannel with the inlet and outlet width being 300 μm and 200 μm, respectively. The standard flow rates controlled by the syringe pump are ranging from 3.508 to 11.693 μL/min. The quasi-three-dimensional velocities at the branch point of the T-shape microchannel are constructed by measuring the two-dimensional velocities on 11 fluid layers from the bottom of microchannel to the top. Based on this, the flow rates are calculated by the discrete integration of velocity distributions on the cross-section of microchannel. The relative errors of the flow rates of the inlet and outlet are all within 3%, and we conclude that the main factors affecting the measurement precision of flow rate include the wall roughness of the microchannel, the spatial resolution of microscopic system and the algorithm of velocity evaluation.

  2. Structure of Wall-Eddies at Very Large Reynolds Number--A Large-Scale PIV Study

    Hommema, S. E.; Adrian, R. J.


    The results of an experiment performed in the first 5 m of the neutral atmospheric boundary layer are presented. Large-scale PIV measurements (up to 2 m × 2 m field-of-view) were obtained in the streamwise / wall-normal plane of a very-large Reynolds number (Re_θ > 10^6, based on momentum thickness and freestream velocity), flat-plate, zero-pressure-gradient boundary layer. Measurements were obtained at the SLTEST facility in the U.S. Army's Dugway Proving Grounds. Coherent packets of ramp-like structures with downstream inclination are observed and show a remarkable resemblance to those observed in typical laboratory-scale experiments at far lower Reynolds number. The results are interpreted in terms of a vortex packet paradigm(Adrian, R.J., C.D. Meinhart, and C.D. Tomkins, Vortex organization in the outer region of the turbulent boundary layer, to appear in J. Fluid Mech., 2000.) and begin to extend the model to high Reynolds numbers of technological importance. Additional results obtained during periods of non-neutral atmospheric stability are contrasted with those of the canonical neutral boundary layer. Sample smoke visualization images (3 m × 15 m field-of-view) are available online from the author.

  3. Experimental Study of Natural Convective Flow over a Hot Horizontal Rhombus Cylinder Immersed in Water via PIV Technique

    M. Karbasi pour


    Full Text Available Natural convective flow over a horizontal cylinder is a phenomenon used in many industries such as heat transfer from an electrical wire, heat exchanger, pipe heat transfer, etc. In this research, fluid dynamics of natural convective flow over a horizontal rhombus cylinder, with uniform heat flux, is investigated by using two-dimensional Particle Image Velocimetry (PIV Technique. Experiments are carried out in a cubical tank full of water having an interface with air and the cylinder is placed horizontally inside the tank. The heater is turned on for 40s and the effects of heater's power and the height of water above the cylinder are surveyed. The experiments are carried out in three different heights of water and two different heater’s powers in which Rayleigh number changes from 1.33×107 to 1.76×107. The emitted heat flux causes the buoyancy force to be made and the main branch of flow to be formed. Then, moving up the main branch flow through the stationary water generates two equal anti-direction vortexes. These vortexes are developed when they reach the free surface. The results indicate that the flow pattern changes for different values of water height and heater’s power.

  4. Fabrication of artificial arteriovenous fistula and analysis of flow field and shear stress by using μ-PIV technology

    Park, Sun Cheol; Kim, Hyun Kyu [Div. of Vascular Surgery, Dept. of Surgery, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of); Song, Ryun Geun; Kim, Sun Ho; Lee, Jin Kee [School of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kim, Seung Hyun [School of Engineering, Brown University, Providence (United States)


    Radio-cephalic arteriovenous fistula (RC-AVF) is an operation performed to achieve vascular access for hemodialysis. Although RC-AVF is a reliable and well-known method, this technique presents high rates of early failure depending on the vessel condition. These failures are due to blood shear stress around the anastomosis site and the vascular access failure caused by thrombosis secondary to stenosis formation, as well as vascular access reocclusion after percutaneous interventions. In this work, we fabricate in vitro 3D RC-AVF by using polydimethylsiloxane and 3D printing technology to understand the underlying mechanism and predict AVF failure. Micro- Particle image velocimetry (μ-PIV) focusing on the cardiac pulse cycle is used to measure the velocity field within the artificial blood vessel. Results are confirmed by numerical simulation. Accordingly, the in vitro AVF model agrees well with the simulations. Overall, this research would provide the future possibility of using the proposed method to reduce in vivo AVF failure for various conditions.

  5. Interactions of Copepods with Fractal-Grid Generated Turbulence based on Tomo-PIV and 3D-PTV

    Sun, Zhengzhong; Krizan, Daniel; Longmire, Ellen


    A copepod escapes from predation by sensing fluid motion caused by the predator. It is thought that the escape reaction is elicited by a threshold value of the maximum principal strain rate (MPSR) in the flow. The present experimental work attempts to investigate and quantify the MPSR threshold value. In the experiment, copepods interact with turbulence generated by a fractal grid in a recirculating channel. The turbulent flow is measured by time-resolved Tomo-PIV, while the copepod motion is tracked simultaneously through 3D-PTV. Escape reactions are detected based on copepod trajectories and velocity vectors, while the surrounding hydrodynamic information is retrieved from the corresponding location in the 3D instantaneous flow field. Measurements are performed at three locations downstream of the fractal grid, such that various turbulence levels can be achieved. Preliminary results show that the number of escape reactions decreases at locations with reduced turbulence levels, where shorter jump distances and smaller change of swimming orientation are exhibited. Detailed quantitative results of MPSR threshold values and the dynamics of copepod escape will be presented. Supported by NSF-IDBR Grant #0852875.

  6. Monitoring of surface velocity of hyper-concentrated flow in a laboratory flume by means of fully-digital PIV

    Termini, Donatella; Di Leonardo, Alice


    High flow conditions, which are generally characterized by high sediment concentrations, do not permit the use of traditional measurement equipment. Traditional techniques usually are based on the intrusive measure of the vertical profile of flow velocity and on the linking of water depth with the discharge through the rating curve. The major disadvantage of these measurement techniques is that they are difficult to use and not safe for operators especially in high flow conditions. The point is that, as literature shows (see as an example Moramarco and Termini, 2015), especially in such conditions, the measurement of surface velocity distribution is important to evaluate the mean flow velocity and, thus, the flow discharge. In the last decade, image-based techniques have been increasingly used for surface velocity measurements (among others Joeau et al., 2008). Experimental program has been recently conducted at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Materials Engineering (DICAM) - University of Palermo (Italy) in order to analyze the propagation phenomenon of hyper-concentrated flow in a defense channel. The experimental apparatus includes a high-precision camera and a system allowing the images recording. This paper investigates the utility and the efficiency of the digital image-technique for remote monitoring of surface velocity in hyper-concentrated flow by the aid of data collected during experiments conducted in the laboratory flume. In particular the present paper attention is focused on the estimation procedure of the velocity vectors and on their sensitivity with parameters (number of images, spatial resolution of interrogation area,) of the images processing procedure. References Jodeau M., A. Hauet, A. Paquier, Le Coz J., Dramais G., Application and evaluation of LS-PIV technique for the monitoring of river surface in high flow conditions, Flow Measurements and Instrumentation, Vol.19, No.2, 2008, pp.117

  7. Space and time reconstruction of the precessing vortex core in Francis turbine draft tube by 2D-PIV

    Favrel, A.; Müller, A.; Landry, C.; Yamamoto, K.; Avellan, F.


    Francis turbines operating at part load conditions experience the development of a high swirling flow at the runner outlet, giving rise to the development of a cavitation precessing vortex rope in the draft tube. The latter acts as an excitation source for the hydro-mechanical system and may jeopardize the system stability if resonance conditions are met. Although many aspects of the part load issue have been widely studied in the past, the accurate stability analysis of hydro-power plants remains challenging. A better understanding of the vortex rope dynamics in a wide range of operating conditions is an important step towards the prediction and the transposition of the pressure fluctuations from reduced to prototype scale. For this purpose, an investigation of the flow velocity fields at the outlet of a Francis turbine reduced scale physical model operating at part load conditions is performed by means of 2D-PIV in three different horizontal cross-sections of the draft tube cone. The measurements are performed in cavitation-free conditions for three values of discharge factor, comprised between 60% and 81% of the value at the Best Efficiency Point. The present article describes a detailed methodology to properly recover the evolution of the velocity fields during one precession cycle by means of phase averaging. The vortex circulation is computed and the vortex trajectory over one typical precession period is finally recovered for each operating point. It is notably shown that below a given value of the discharge factor, the vortex dynamics abruptly change and loose its periodicity and coherence.

  8. Instability of outer tip vortices for a 2.5 MW wind turbine: integrating snow PIV with LES

    Sotiropoulos, Fotis; Yang, Xiaolei; Hong, Jiarong; Barone, Matthew


    Recent field experiments conducted around a 2.5 MW wind turbine using super-large-scale PIV (SLPIV) using natural snow particles have revealed tip vortex cores (visualized as areas devoid of snowflakes) of complex shape, consisting of both round and elongated void patterns. Here we employ large-eddy simulation to elucidate the structure and dynamics of the complex tip vortices identified experimentally. The LES is shown to reproduce vortex cores in remarkable agreement with the SLPIV results, essentially capturing all vortex core patterns observed in the field in the tip shear layer. We show that the stretched elongated vortex cores observed in 2D planes are the footprints of a second set of counter-rotating spiral vortices that emanates along the tip shear layer immediately downwind of the blades and is intertwined with the tip vortices. We argue that this large-scale instability is of centrifugal type since the mean flow characteristics in the outer tip shear layer resemble those of the Taylor-Couette flow. This study highlights the feasibility of employing snow voids to visualize tip vortices and demonstrates the enormous potential of integrating SLPIV with LES as a powerful tool for gaining novel insights into the wakes of utility scale wind turbines. This work was supported by Department of Energy DOE (DE-EE0002980, DE-EE0005482 and DE-AC04-94AL85000), Sandia National Laboratories and NSF Career Award (NSF-CBET-1454259) for Jiarong Hong. Computational resources were provided by SNL and MSI.

  9. Numerical Investigation of Velocity Flow Field inside an Impeller Air Model of a Centrifugal Pump with Vaned Diffuser Interactions and Comparison with PIV Measurements

    Abdelmadjid Atif


    Full Text Available The paper refers to the analysis of interactions between the impeller and the vaned diffuser on the air model of a radial flow pump. The study deals with a numerical simulation of the flow for a full 360° entire impeller and diffuser. The task is carried out close to design operating conditions and for one particular position of the impeller blade with respect to diffuser frame. Among all the results, it has been decided to mainly focus on the flow pattern at the exit part inside the impeller coming from the diffuser vanes interactions. The results are compared to the available PIV measurements.

  10. 表面 PIV在潜航体兴波伴流场测量中的应用%The application of surface PIV in the measurement of wave making of underwater moving body

    周文进; 蒋小勤; 王建中; 方频捷


    This paper is mainly to introduce an experimental method for measuring wave making of underwater moving body by PIV. Apart from of analysing the principle of Surface-PIV, defining coordinate, and how to eliminate interference from background, the precision of Surface-PIV is also analysed in detail. Experiment show that 'V' type wave and source-sink effect are successfully detected. Comparing with the traditional PIV, Surface-PIV is not only economical and practicable under the laboratory conditions, but also accurate and reliable. Effective accuracy of Surface-PIV can reach 0.01pixel.%介绍潜航体兴波伴流场的表面 PIV测量方法,对表面 PIV的标定,示踪粒子的选择,背景干扰流场的消除方法以及表面 PIV测量精度等问题开展分析讨论。实验表明:运用表面 PIV技术可灵敏地探测到潜航体微弱的 V型兴波伴流场,该兴波伴流场可以用潜航体的‘源-汇’效应解释。本文采用普通 CCD数码摄像机以及普通光源摄取表面粒子图像,与传统的激光 PIV设备相比,不仅经济而且使用方便,测量结果精确可靠,运用表面 PIV技术测量表面微弱流场的精度可达0.01 pixel。

  11. 2D and 3D time-resolved PIV experiments on flow field around vertical and inclined water-exit body%垂直及斜出水流场的二维及三维TR-PIV试验

    张军; 李英浩; 金朋寿


    本文对钝头回转体垂直及斜出水流场采用TR-(Time-Resolved)PIV技术进行测量,并对斜出水流场进行3D-Stereo PIV(三维体视 PIV)测量.文中介绍了测试技术及测量结果,揭示了出水过程中流动结构及其演变,展示了TR-PIV技术对具有瞬态历程特征的出水流场研究的适应性.

  12. Influência do redimensionamento hidráulico de precisão na uniformidade de distribuição de água em sistemas de irrigação do tipo pivô central

    Santana, Renato de Castro [UNESP


    O objetivo deste trabalho foi avaliar as características de desempenho de dois equipamentos de irrigação do tipo pivô central, com áreas idênticas e condições hidráulicas diferenciadas quantificando o desgaste dos reguladores de pressão e difusores. A avaliação do desempenho do sistema foi efetuada com base no coeficiente de uniformidade de Christiansen (CUC), calculado pela metodologia de ensaios proposta pela ABTN/ASAE/A CAMPO. Os pivôs centrais foram ensaiados na velocidade de 100% da regu...

  13. Setting efficiency indicators for center pivots Ajuste de indicadores de eficiência para pivôs centrais

    Ricardo L. Schons


    Full Text Available In this study, it was discussed the efficiency criteria in each of the elements that compose a central pivot, and this analysis was applied to two sets of systems located in regions of Cruz Alta and Santo Augusto, state of Rio Grande do Sul, Brazil. The methodology used combines water and energy assessment through an indicator called Normalized Specific Consumption in Irrigation (C ENI, allowing thus a comparison between equipment and projects. The C ENI in Cruz Alta region showed 72% of the equipment above the standard (8.68 kWh mm-1 ha-1 100m-1, and in Santo Augusto region 64.28% with consumption above the standard. The mean irrigation efficiency for Cruz Alta region was 29.85%, with standard deviation of 5.41%, and for Santo Augusto region, it was 29.02%, with standard deviation of 5.15%.Neste trabalho, são discutidos critérios de eficiência em cada um dos elementos que compõem um pivô central, sendo esta análise aplicada a dois conjuntos de sistemas localizados, nas regiões de Cruz Alta e Santo Augusto, Rio Grande do Sul. A metodologia utilizada associa as avaliações hídrica e energética por meio de um indicador denominado Consumo Específico Normalizado na Irrigação (C ENI, possibilitando, desta forma, uma comparação entre equipamentos e entre projetos. O C ENI na região de Cruz Alta apresentou 72% dos equipamentos acima do padrão (8,68 kWh mm-1 ha-1 100m-1, e na região de Santo Augusto, 64,28% com o consumo acima do padrão. A eficiência de irrigação média para a região de Cruz Alta foi de 29,85%, com desvio-padrão de 5,41%; e para a Região de Santo Augusto foi de 29,02%, com desvio padrão de 5,15%.

  14. Analysis of vortical structure over sinusoidal riblet surface in turbulent channel flow by means of Dual-plane stereoscopic PIV measurement

    Mamori, Hiroya; Yamaguchi, Kyotaro; Sasamori, Monami; Iwamoto, Kaoru; Murata, Akira


    We perform a dual-plane stereoscopic particle image velocimetry (DPS-PIV) measurement to investigate vortical structure over a sinusoidal riblet surface in the turbulent channel flow. In the sinusoidal riblet surface, its lateral spacing of the adjacent walls varies in the streamwise direction and 12% of the drag reduction rate has been confirmed in the turbulent channel flow. The DPS-PIV measurement system consists of four high-speed CCD cameras and the two laser sheets. In the flat case, the profile of the velocity statistics shows a good agreement with previous data. In the ribet case, the velocity statistics decrease in the region close to the wall as compared with that of the flat case. Since all velocity components are measured on adjacent laser sheets simultaneously, vortical structures can be obtained by a second invariant of the tensor i.e. the Q value. According to an analysis for the Q value, we found that the vortical structure is shifted up and attenuated owing to the riblet. Moreover, the riblet prevents the approaching of the vortical structure: the upward and downward flows in the region near the wall are generated by the riblet; if the vortical structure approaches the wall, it is shifted away from the wall due to the upward flow.

  15. 利用Micro-PIV测量微管道内流量的研究%Study on the Flowrate Mesurement in Microtubes by Micro-PIV

    张永胜; 刘彦军; 王金华


    为了解决微管道(水力直径小于1 mm)内流量测量问题,采用Micro-PIV对水力直径为230 μm毛细玻璃管内流量进行测量.实验中对Re=480~2 260范围内流量进行测量,试验结果证明利用该技术完全可能实现微管道内流量精确测量.%In order to solve the problem of measuring the flow rate in microtubes (the hydraulic diameter is under lmm) ,the Micro-PIV is used to measure the fiowrate within the capillary tube,and its hydraulic diameter is 230μm.In the experiment,the fiowrate is measured in the reynolds number range of 480 ~ 2260,and the conclusion is that Micro-PIV technique can be used to measure the fiowrate in the microtubes with high precision.

  16. Direct calculation of the weighting function and depth of correlation in Micro-Particle Image Velocimetry (Micro-PIV) from particle images

    Hein, Michael; Wieneke, Bernhard; Seemann, Ralf


    Micro-PIV has become the most popular tool to measure flow profiles in microfluidics. When measuring in-plane velocities in a three dimensional flow the measured velocity depends on all particles in the images, even on defocused particles, and is given by a weighted average of the true velocity dx(z) with a weighting function W(z). W(z) depends on the optical setup as well as on the particle diameter and gradients of the flow-profile. The width of W(z) determines the height-extension of the plane in which particles can influence the measurement (Depth of Correlation, DOC). Thus the knowledge of the system dependent W(z) is crucial and can be used to reduce the errors introduced by depth-averaging the velocity field. We determine W(z) and thus the DOC using artificial double images for any given flow profile generated from particle images taken with the same optical setup as used for the PIV measurements. Experimental results for objectives with different numerical apertures (NA), different particle sizes and various out-of-plane gradients will be discussed. The resulting weighting function turns out to be quite asymmetric for air-objectives with high NAs, differing significantly in shape and width (DOC) from existing theoretical predictions.

  17. Desenvolvimento de um sistema de pulverização acoplável a pivô central Development of a spray system attached to center pivot

    Luis A. A. Vilela


    Full Text Available Com o objetivo de se aplicar produtos químicos às culturas, desenvolveu-se um sistema de pulverização acoplável a pivô central e também um protótipo do equipamento. Durante a aplicação, a estrutura aérea do pivô central se desloca sem irrigar, apenas transportando o sistema de pulverização sobre a área. O sistema é composto de duas barras de pulverização instaladas em cada vão do pivô. O regime intermitente da pulverização, responsável pela redução da calda aplicada, foi feito por meio de um circuito eletrônico, sincronizado ao acionamento dos motorredutores, que aciona uma válvula solenóide localizada na entrada da barra de pulverização. O sistema desenvolvido possibilita aplicar-se volume de pulverização de até 246 L ha-1. Os diâmetros de gotas atenderam às recomendações técnicas para aplicação de defensivos agrícolas. Tempos ligado-desligado da válvula solenóide de 0,4 - 2,5, 0,5 - 2,5, 0,3 - 3,5 e 0,4 - 3,5 s resultaram em valores de coeficiente de variação inferiores a 15%, aceitáveis para pulverizações por meio terrestre.For the application of chemical products a equipment attached to center pivots was developed. During application, the aerial structure of the center pivot system moves, without accomplishing irrigation, just transporting the spray system around the area. In order to compensate different speeds two spray bars were installed in each pivot span. Intermittent spraying was achieved by means of solenoid valves controlled by electronic circuit synchronized with electric motor gears. The system is able to apply a minimum volume of 246 L ha-1. Drop diameters obtained were compatible with the requirements of application of chemical products. On/off time sequences of 0.4 - 2.5, 0.5 - 2.5, 0.3 - 3.5 and 0.4 - 3.5 s resulted in coefficients of variation under 15%, that are acceptable for ground based applications.

  18. Investigation of Unsteady Tip Clearance Flow in a Low-Speed One and Half Stage Axial Compressor with LES And PIV

    Hah, Chunill; Hathaway, Michael; Katz, Joseph; Tan, David


    The primary focus of this paper is to investigate how a rotor's unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor when the rotor tip gap size is increased from 0.5 mm (0.49% of rotor tip blade chord, 2% of blade span) to 2.4 mm (2.34% chord, 4% span) at the design condition are investigated. The changes in unsteady tip clearance flow with the 0.62 % tip gap as the flow rate is reduced to near stall condition are also investigated. A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at these three flow conditions. Detailed Stereoscopic PIV (SPIV) measurements of the current flow fields were also performed at the Johns Hopkins University in a refractive index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. Unsteady tip clearance flow fields from LES are compared with the PIV measurements and both LES and PIV results are used to study changes in tip clearance flow structures. The current study shows that the tip clearance vortex is not a single structure as traditionally perceived. The tip clearance vortex is formed by multiple interlaced vorticities. Therefore, the tip clearance vortex is inherently unsteady. The multiple interlaced vortices never roll up to form a single structure. When phased-averaged, the tip clearance vortex appears as a single structure. When flow rate is reduced with the same tip gap, the tip clearance vortex rolls further upstream and the tip clearance vortex moves further radially inward and away from the suction side of the blade. When the tip gap size is increased at the design flow condition, the overall tip clearance vortex becomes stronger and it stays closer to the blade suction side and the vortex core extends all the way to the exit of the blade passage. Measured and calculated unsteady flow

  19. The image velocimetry of bubble in water based on PIV%基于PIV技术的水中气泡图像测速法

    宁辉; 唐远河; 邵建斌



  20. Influence of Tricuspid Bioprosthetic Mitral Valve Orientation Regarding the Flow Field Inside the Left Ventricle: In Vitro Hydrodynamic Characterization Based on 2D PIV Measurements.

    Bazan, Ovandir; Ortiz, Jayme P; Fukumasu, Newton K; Pacifico, Antonio L; Yanagihara, Jurandir I


    The flow patterns of a prosthetic heart valve in the aortic or mitral position can change according to its type and orientation. This work describes the use of 2D particle image velocimetry (PIV) applied to the in vitro flow fields characterization inside the upper part of a left ventricular model at various heart rates and as a function of two orientations of stented tricuspid mitral bioprostheses. In the ventricular model, each mitral bioprosthesis (27 and 31 mm diameter) was installed in two orientations, rotated by 180°, while the aortic bileaflet mechanical valve (27 mm diameter) remained in a fixed orientation. The results (N = 50) showed changes in the intraventricular flow fields according to the mitral bioprostheses positioning. Also, changes in the aortic upstream velocity profiles were noticed as a function of mitral orientations.

  1. Development of a Large Field-of-View PIV System for Rotorcraft Testing in the 14- x 22-Foot Subsonic Tunnel

    Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.; Harris, Jerome; Allan, Brian; Wong, Oliver; Mace, W. Derry


    A Large Field-of-View Particle Image Velocimetry (LFPIV) system has been developed for rotor wake diagnostics in the 14-by 22-Foot Subsonic Tunnel. The system has been used to measure three components of velocity in a plane as large as 1.524 meters by 0.914 meters in both forward flight and hover tests. Overall, the system performance has exceeded design expectations in terms of accuracy and efficiency. Measurements synchronized with the rotor position during forward flight and hover tests have shown that the system is able to capture the complex interaction of the body and rotor wakes as well as basic details of the blade tip vortex at several wake ages. Measurements obtained with traditional techniques such as multi-hole pressure probes, Laser Doppler Velocimetry (LDV), and 2D Particle Image Velocimetry (PIV) show good agreement with LFPIV measurements.

  2. 高速PIV布撒技术的改进研究%Research on Improving Technique of PIV Seeding in Hyper/supersonic Flow



    Based on the developed technique of Hypersonic Innovation Technique Laboratory of SJTU, the new PIV seeding system in hyper/supersonic flow is developed and improved.The new PIV seeding system is redesigned by im-proving the conduit,high pressure gas source and nozzle to overcome the instability of effective seeding of the old sys-tem. Flexibility of conduit,high press dry nitrogen and turbulence nozzle are used to reconstruct the system. The recon-struction was analyzed and experimentally tested, which shows that seeding effect is improved. At last, more directions to improve the system are offered.%基于上海交通大学高超创新实验室现有技术,为发展高速PIV技术而改进开发了高速PIV粒子布撒系统。针对原有系统经常无法有效布撒粒子的缺陷,从系统中的管道、高压气体、喷嘴等几个方向下手进行改造,设计了新的高速PIV粒子布撒系统。对管道进行了软管化设计,高压气体采用干燥的氮气,喷嘴则设计成能在罐体中产生旋流的结构。对于这些改造进行了分析和实验测试,证明了这些改造能加强布撒粒子的效果。最后提出了这套系统可以继续改进的一些方向。

  3. Examining flow-flame interaction and the characteristic stretch rate in vortex-driven combustion dynamics using PIV and numerical simulation

    Hong, Seunghyuck


    In this paper, we experimentally investigate the combustion dynamics in lean premixed flames in a laboratory scale backward-facing step combustor in which flame-vortex driven dynamics are observed. A series of tests was conducted using propane/hydrogen/air mixtures for various mixture compositions at the inlet temperature ranging from 300K to 500K and at atmospheric pressure. Pressure measurements and high speed particle image velocimetry (PIV) are used to generate pressure response curves and phase-averaged vorticity and streamlines as well as the instantaneous flame front, respectively, which describe unsteady flame and flow dynamics in each operating regime. This work was motivated in part by our earlier study where we showed that the strained flame consumption speed Sc can be used to collapse the pressure response curves over a wide range of operating conditions. In previous studies, the stretch rate at which Sc was computed was determined by trial and error. In this study, flame stretch is estimated using the instantaneous flame front and velocity field from the PIV measurement. Independently, we also use computed strained flame speed and the experimental data to determine the characteristic values of stretch rate near the mode transition points at which the flame configuration changes. We show that a common value of the characteristic stretch rate exists across all the flame configurations. The consumption speed computed at the characteristic stretch rate captures the impact of different operating parameters on the combustor dynamics. These results suggest that the unsteady interactions between the turbulent flow and the flame dynamics can be encapsulated in the characteristic stretch rate, which governs the critical flame speed at the mode transitions and thereby plays an important role in determining the stability characteristics of the combustor. © 2013 The Combustion Institute.

  4. 层流炉二维PIV自动控制系统%Design and Experiment of the Two-dimensional PIV Automatic Control System for Laminar Entrained Flow Reactor

    杨延强; 易维明; 李志合; 柏雪源; 李永军


    In the cold PIV (particle image velocimetry) system of the laminar entrained flow reactor, the relative position between the camera and the measuring tube was an important condition to ensure accurate test data. To make the PIV operation more convenient, accurate, and fast in the test, two-dimensional PIV automatic control system was designed. And the reliability of the system was tested in the cold simulation equipment of laminar flow furnace, compared with no using two-dimensional PIV automatic control system, the results showed that in different sections of the measuring tube, the particle speed of the axial center achieves a smooth transition, and eliminates the jump change; when collection distance is 350mm and main air flow rate is 1. 5 mVh, the relative error of particle residence time is 9. 218% ; and the operation saves time and effort in the test process. These suggested that the two-dimensional PIV automatic control system could satisfy the cold test of the laminar entrained flow reactor needs, achieve uniform and continuous test, reduce human error and improve the accuracy of test data.%在层流炉冷态粒子图像测速( PIV)系统中,相机与测量管的相对位置是保证试验数据精确的重要条件.为使试验过程中整个PIV系统操作起来更加方便、准确、快捷,设计了二维PIV自动控制系统,并在层流炉冷态模拟装置上对该系统的可靠性进行了试验验证.与没有使用二维PIV自动控制系统之前的试验结果相比:各测量段颗粒的轴向中心速度相互之间的衔接实现了平滑过渡,消除了跳跃性变化;收集距离为350 mm,主气流流量为1.5 m3/h时,层流炉内颗粒停留时间的相对误差为9.218%.说明该二维PIV自动控制系统能够满足层流炉冷态试验需要,实现了均匀、连续拍摄,减少了人为误差,提高了试验数据的准确性.

  5. Manejo da irrigação em pastagem irrigada por pivô-central Irrigated pasture: water management under center pivot irrigation

    Alexandre C. Xavier


    Full Text Available A aplicação de lâminas de irrigação em pastagem irrigada sob pivô-central é, de maneira geral, realizada sem um critério técnico pertinente ao sistema, pois se deve considerar que para um mesmo período a pastagem se encontra em diferentes estádios de desenvolvimento em cada parcela, apresentando taxas de evapotranspiração diferenciadas dentro da área irrigada; todavia, usualmente se aplica uma única lâmina para toda a área. Neste trabalho foi desenvolvido um modelo para aplicação de lâminas de irrigação distinta para cada parcela do pivô o qual, de modo geral, considera: i a capacidade do pivô-central de aplicar lâminas distintas na área; ii o nível de desenvolvimento da cultura em cada parcela; iii o período de retorno do gado a determinada parcela (ciclo de pastejo; e iv o potencial de desenvolvimento da pastagem de certa região. Para modelar o coeficiente de cultura (Kc foram utilizadas duas metodologias, a primeira com taxa de variação do Kc constante com o número de dias em que a parcela está em descanso (k, e a segunda, com taxa de variação do Kc na forma senoidal com k. O modelo foi aplicado para pastagens hipotéticas nas regiões de Piracicaba e Pereira Barreto, para avaliação e, como resultado, observou-se que o modelo se mostrou sensível ao nível de desenvolvimento de cada parcela e às condições de variação do clima de cada região.The application of irrigation depths in irrigated pasture under center pivot machines, in a general way, is accomplished without a pertinent technical criterion, because it should be considered that for any time period, the pasture plots are at different development stages (rotary pasture, presenting different evapotranspiration rates inside the irrigated area. Furthermore, farmers usually apply a single irrigation depth for the whole area. In this study a model was developed for the application of different irrigation depths in each portion of the pivot (pizza

  6. 使用PIV技术测量喷嘴附壁射流的冷态流场%Study of the Velocity Field of Nozzle Wall Jet with PIV Measurement Method

    陈向阳; 邹介棠



  7. PIV measurement of char powders motion in laminar entrained flow reactor%层流炉反应管内炭粉颗粒运动的PIV试验

    王娜娜; 易维明; 刘珠伟; 柏雪源


    In order to study the movements of char powders in laminar entrained flow reactor, a transparent experimental apparatus was designed for Particle Image Velocimetry(PIV) measurement of flow field.The velocities of char powders whose mesh size was between 100 to 120 were investigated by PIV at the different flow rates of 1.0-2.5 m3/h.The results indicated that the axial velocity of char powers in the pipe center was very small near the outlet, subsequently rapidly reached the maximum and then decreased.The axial velocity at the center of pipe reached a maximum in the region within 1.8-123.8 mm.The axial velocity distribution was a parabola-like curve along the radius.The relationship between Re and the dimensionless residential time of char powders was obtained finally.%为了研究炭粉颗粒在层流炉反应管内的运动规律,按照1:1比例设计制造了一套透明玻璃试验装置用于PIV流场测量.分别在4种不同的主气流量下,对粒径为100~120目的炭粉颗粒在反应管内的速度场进行了PIV无接触测量.结果表明,在反应管中心处,开始时,炭粉颗粒的轴向速度在下料口附近很小,然后迅速增加到最大值,而后以此速度运动一段距离后,速度开始减小.在约1.8~123.8 mm段,炭粉颗粒的轴向速度在管道中心处为最大.轴向速度沿径向成类似抛物线状分布;通过对测量数据的分析计算,获得了管内气流雷诺数与炭粉颗粒停留时间(无量纲处理后)的关联式.

  8. PIV experiment on flow characteristics between submerged double spur dikes%淹没双丁坝间水流结构特性PIV试验

    刘易庄; 蒋昌波; 邓斌; 王刚


    为探讨淹没双丁坝对坝间水流的影响,采用粒子图像测速( PIV)系统对坝间水平面流场进行了测量,并对坝间水流结构进行了分析。结果表明:丁坝间距与丁坝长度的比值d/B( B为定值)对坝间漩涡中心位置、坝间回流区及涡量分布有着显著影响;d/B越大,坝间“漩涡”中心越接近坝头线;坝间回流区宽度随d/B增大而增大,零速度线基本呈线性关系且其斜率随d/B增大而减小,同时回流区流速也随之发生很大变化;上游丁坝头附近出现最大负涡量而在下游丁坝头附近出现最大正涡量。%In order to study the influence of submerged double spur dikes on the flow characteristics between them, this study measured the horizontal flow field within the area between the spur dikes using a particle image velocimetry ( PIV) system, and analyzed the flow characteristics between the spur dikes. Results show that the ratio of the gap between the double spur dikes to the dike length d/B ( B is a constant) has a significant impact on the location of the eddy’ s core between the spur dikes, the recirculation flow between the spur dikes, and the vorticity distribution around the heads of the spur dikes. When the value of d/B increases, the eddy’ s core is closer to the line connecting the tips of the spur dikes, and the width of the recirculation zone increases. The zero velocity line changes linearly in the streamwise direction, and its slope decreases with the increase of d/B. The velocity in the recirculation zone changes significantly with the value of d/B. The maximum negative vorticity occurs near the head of the upstream spur dike, while the maximum positive vorticity occurs near the head of the downstream spur dike.

  9. SUMO: regulating the regulator

    Bossis Guillaume


    Full Text Available Abstract Post-translational modifiers of the SUMO (Small Ubiquitin-related Modifier family have emerged as key regulators of protein function and fate. While the past few years have seen an enormous increase in knowledge on SUMO enzymes, substrates, and consequences of modification, regulation of SUMO conjugation is far from being understood. This brief review will provide an overview on recent advances concerning (i the interplay between sumoylation and other post-translational modifications at the level of individual targets and (ii global regulation of SUMO conjugation and deconjugation.

  10. 复杂固体边界流场的三维 PIV 测试技术:任意三维边界识别算法%Three-dimensional PIV measurement technique for complex solid boundary:arbitrary three-dimensional boundary recognition algorithm

    陈建; 施圣贤; 刘应征


    A SURF based three-dimensional boundary recognition algorithm has been devel-oped for identifying and reconstructing three-dimensional geometry of arbitrary solid boundaries. This method is used in conjunction with MLOS-SMART three-dimensional particle image recon-struction and three-dimensional cross-correlation algorithms to simultaneously measure the veloc-ity field as well as the boundary geometry.The boundary recognition algorithm was firstly veri-fied by using a set of cylinder images where the exact curvatures were known.The three-dimen-sional velocity field of a cylinder wake was then calculated by CFD and used for generating syn-thetic particle image sets.Finally,the validity and accuracy of the algorithms were verified by processing the synthetic images and comparing the calculated velocity filed and boundary geome-try with CFD data and the exact cylinder dimensions.%针对复杂固体边界三维流场的 PIV 测试应用,以及流固耦合实验研究中流场和固体结构特征的瞬态同步测试需求,发展了一种基于双相机布置形式的任意三维边界识别算法以精确获取三维表面几何信息;并以基于MLOS-SMART 三维粒子场重构的 Tomo-PIV 算法计算三维速度矢量场,可同步获取三维表面结构运动/变形信息和三维瞬态速度场。这一边界识别算法基于 SURF(加速稳健特征)模式识别算法进行三维曲面重构,可以确定流场中三维物体结构的边界特征。论文采用双相机布置方式获取了三种不同曲率的圆柱曲面图像,验证了所发展的三维边界识别算法的准确性。最后以圆柱绕流 Tomo-PIV 数字合成粒子图像序列为验证对象,采用所发展的边界识别算法和 Tomo-PIV 算法分别高质量地计算出圆柱曲面信息和三维速度场。

  11. 副流感病毒3型感染肺炎患儿细胞免疫功能分析%Analysis of immune function in children with pneumonia of PIV3 infection

    赵显虹; 刘继贤; 李瑞; 贾文燕


    Objective To analyze the changes of T lymphocyte subsets, B lymphocyte and NK cells in pneumonia children infected by parainfluenza virus types 3( PIV3 ).Methods Multi-pathogen detection using direct fluorescence antibody test (DFA) ,clear etiology diagnosis.T lymphocyte subsets, B lymphocyte and NK cells in peripheral blood in part of patients were examined by flow cytometry.Results In,There was no significant difference in CD3 + T,CD4 +T, CD8 +T cells and CD19 + B cells between the patients with PIV3 pneumonia and the controls.But the ratio of NK cells were lower in group PIV3 than those in the controls ( P < 0.05 ).In contrast, the ratio of CD4 +/Cl8 + increase in group PIV3 than those in the controls ( P < 0.05 ).Conclusion Parainfluenza virus types 3 ( PIV3 ) cases of pneumonia children cellular immune disorders.%目的 分析副流感病毒3型感染肺炎患儿外周血T淋巴细胞亚群、B淋巴细胞及NK细胞的变化.方法 对入院儿童行痰病原学检测7种常见病毒抗原,明确病原学诊断,并用流式细胞仪检测副流感病毒3型感染患儿外周血T淋巴细胞亚群、B淋巴细胞及NK细胞值.结果 副流感病毒3型肺炎患儿外周血CD16+CD56+T细胞百分率较对照组减少,CD3+T细胞百分率、CD4+T细胞百分率、CD8+T细胞百分率、CD19+CD21+B细胞百分率和对照组相仿,CD4+/CD8+比值较对照组升高.结论 副流感病毒3型感染肺炎患儿细胞免疫功能紊乱.

  12. Visualization of the flow profile inside a thinning filament during capillary breakup of a polymer solution via particle image velocimetry (PIV) and particle tracking velocimetry (PTV)

    Gier, S


    We investigated the flow profile of a polymer solution in a thinning capillary bridge. Fluorescent tracer particles with a diameter of 3$\\mu$m were used to visualize the flow. The cylindrical shape of the filament introduced strong optical abberations that could be corrected for, and we were able to characterize the flow in filaments with a thickness ranging from 150 to 30 $\\mu$m. In the first regime when the filament was still sufficiently large, we used a PIV algorithm to deduce the flow field. At later stages when the number of particles in the observation plane decreased a PTV algorithm was used. The main two results of our measurements are as follows. First, the flow profile at the formation of the cylindrical filament is highly inhomogeneous and there is only flow in the outer parts of the filament. Second, we find that in most parts of the regime, where the temporal radius of the thinning filament can be fitted with an exponential law the flow indeed is purely extensional.

  13. 水平携带床的粒子图像测试技术测试方案%Application of PIV in entrained-bed

    张波涛; 易维明



  14. 旋风分离器内旋进涡核的PIV显示%Visualization of the Precessing Vortex Core in a Cyclone Separator by PIV

    吴小林; 时铭显


    The precessing vortex core (PVC) in a cyclone separator plays an important role in the separation performance and in further understanding of the general law of periodic unsteady flow therein. In this paper, theunsteady flow field is investigated with particle image velocimetry (PIV), and the instantaneous velocity, vorticity,tangential velocity, and radial velocity are acquired by analyzing the images of instantaneous flow. It is for the first time reported that there is a centrifugal flow region close to the dust discharge zone and its maximum value is higher than the mean radial velocity. This discovery is very important for understanding the principle of separation of particles in the area of dust discharge. Determination of the frequency and amplitude of PVC was conducted in the region where the phenomenon of PVC is remarkable. Results agree well with those obtained by hot wire anemometry. The observations of the center of vortex core and the bimodal distribution of the amplitude of the PVC indicate the vortex core precesses around the geometric axis of the cyclone in its own way.

  15. Capturing coherent structures and turbulent interfaces in wake flows by means of the Organised Eddy Simulation, OES and by Tomo-PIV

    Deri, E.; Ouvrard, H.; Braza, M.; Hunt, J.; Hoarau, Y.; Cazin, S.; Cid, E.; Harran, G.


    The present study aims at a physical analysis of the coherent and chaotic vortex dynamics in the near wake around a flat plate at incidence, to provide new elements in respect of the flow physics turbulence modelling for high-Reynolds number flows around bodies. This constitutes nowadays a challenge in the aeronautics design. A special attention is paid to capture the thin shear layer interfaces downstream of the separation, responsible for aeroacoustics phenomena related to noise reduction and directly linked to an accurate prediction of the aerodynamic forces. The experimental investigation is carried out by means of tomographic PIV. The interaction of the most energetic coherent structures with the random turbulence is discussed. Furthermore, the POD analysis allowed evaluation of 3D phase averaged dynamics as well as the influence of higher modes associated with the finer-scale turbulence. The numerical study by means of the Organised Eddy Simulation, OES approach ensured a reduced turbulence diffusion that allowed development of the von Karman instability and of capturing of the thin shear-layer interfaces, by using appropriate criteria based on vorticity and dissipation rate of kinetic energy. A comparison between the experiments and the simulations concerning the coherent vortex pattern is carried out.

  16. Experimental study of the application of micro-PIV on the flow characteristics detection of micro-gap rotational flow field

    Tang, Fei; Wang, Chunze; Shi, Yupeng; Wang, Xiaohao


    For a micro-gap rotational flow field with a large horizontal extent, tiny gap and fast flow velocity, the two-dimensional images shot by the micro-scale Particle ImageVelocimetry(Micro-PIV) technique are not sufficient for the study of local or whole flow characteristics. In this paper, by establishing a test bench of a rotational flow field with the functions of driving, positioning, adjustment and sensing, all the local states of the micro-gap rotational flow field can be obtained by horizontally moving the rotating axis to observe point by point. While measuring some local flow fields, two-dimensional pictures are taken by adjusting the focusing height of the objective lens, and then superposed and interpolated according to their shooting order to obtain a quasi-three-dimensional distribution image of the local flow fields, thus obtaining the flow condition of the vertical section of the flow field. The position of the focusing plane and mutual distance are adjusted to realize the measurement of wall shear force in the flow field, providing a feasible reference method for detecting the rheological property of the gap flow field and the effect of surface drag reduction.

  17. Experimental study of the application of micro-PIV on the flow characteristics detection of micro-gap rotational flow field

    Fei Tang


    Full Text Available For a micro-gap rotational flow field with a large horizontal extent, tiny gap and fast flow velocity, the two-dimensional images shot by the micro-scale Particle ImageVelocimetry(Micro-PIV technique are not sufficient for the study of local or whole flow characteristics. In this paper, by establishing a test bench of a rotational flow field with the functions of driving, positioning, adjustment and sensing, all the local states of the micro-gap rotational flow field can be obtained by horizontally moving the rotating axis to observe point by point. While measuring some local flow fields, two-dimensional pictures are taken by adjusting the focusing height of the objective lens, and then superposed and interpolated according to their shooting order to obtain a quasi-three-dimensional distribution image of the local flow fields, thus obtaining the flow condition of the vertical section of the flow field. The position of the focusing plane and mutual distance are adjusted to realize the measurement of wall shear force in the flow field, providing a feasible reference method for detecting the rheological property of the gap flow field and the effect of surface drag reduction.

  18. Influence of Rotation Rate of Sand Particles on Measurement Results by PIV in Wind Sand Flux%风沙流中沙粒旋转对PIV测量结果的影响

    严杰; 谢莉


    In this paper, based on the measurement principle of particle image velocimetry (PIV), we analyze the measurement error of PIV. For two frame images of a single sand.par tide taken by charge-coupled device (CCD) camera at an interval of a pulse time, we calculate the displacement of the mass center of the sand particle and the displacement of the center of image, and calculate the difference between the displacements of the two centers. Then we derive the error's formulas of sand particle velocity and sand particle diameter measurement used by PIV due to the sand particle rotation. It indicates that the velocity error measured by PIV relates to the velocity of sand particles, and the higher is the velocity of sand particles, the larger is the error. The maximum error of velocity measurement by PIV is not beyond 10%, and the measurement error can be decreased by increasing the pulse time. For a single irregular sand particle, the diameters measured by PIV at different moment are not same due to the rotation of sand particles, and the differences among the measurement errors of particle diameters depend on the sand shapes. For lager sand particle, it is pointed out that there is a long way to validate diameter measurement.%基于粒子图像测速仪(ParticleImageVelocimetry,简称PIV)测速度原理以及测量颗粒粒径原理,分析了经过一个激光脉冲时间前后CCD拍摄到的两帧沙粒二维图像,计算了沙粒因旋转而导致的沙粒质心位移与成像中点位移的差别以及不同时刻成像面的大小,导出PIV测量不规则旋转沙粒速度和粒径的测量误差公式.结果表明,PIV测速误差与沙粒速度有关,速度越大测速误差越小,最大测速误差不超过10%,可通过增大激光脉冲时间间隔以减小PIV的测速误差;由于沙粒旋转,使得不同时刻PIV测量到的同一个不规则沙粒的粒径也可能不同,其差别由沙粒形状的不规则程度决定,并指出PIV测量风沙流中不规

  19. Market, Regulation, Market, Regulation

    Frankel, Christian; Galland, Jean-Pierre


    This paper focuses on the European Regulatory system which was settled both for opening the Single Market for products and ensuring the consumers' safety. It claims that the New Approach and Standardization, and the Global Approach to conformity assessment, which suppressed the last technical...... barriers to trade in Europe, realized the free movement of products by organizing progressively several orders of markets and regulation. Based on historical and institutional documents, on technical publications, and on interviews, this article relates how the European Commission and the Member States had...... alternatively recourse to markets and to regulations, at the three main levels of the New Approach Directives implementation. The article focuses also more specifically on the Medical Devices sector, not only because this New Approach sector has long been controversial in Europe, and has recently been concerned...

  20. Market, Regulation, Market, Regulation

    Frankel, Christian; Galland, Jean-Pierre


    This paper focuses on the European Regulatory system which was settled both for opening the Single Market for products and ensuring the consumers' safety. It claims that the New Approach and Standardization, and the Global Approach to conformity assessment, which suppressed the last technical...... barriers to trade in Europe, realized the free movement of products by organizing progressively several orders of markets and regulation. Based on historical and institutional documents, on technical publications, and on interviews, this article relates how the European Commission and the Member States had...... alternatively recourse to markets and to regulations, at the three main levels of the New Approach Directives implementation. The article focuses also more specifically on the Medical Devices sector, not only because this New Approach sector has long been controversial in Europe, and has recently been concerned...

  1. Measurement of flow structures and heat transfer behind a wall-proximity square rib using TSP, PIV and split-fiber film

    He, Chuangxin; Liu, Yingzheng; Peng, Di; Yavuzkurt, Savas


    In the present study, complementary measurement techniques—temperature sensitive paint (TSP), planar particle image velocimetry (planar PIV) and a split-fiber film probe—were used to investigate the effects of a "wall-proximity square rib" on flow structure and surface heat transfer augmentation. TSP was used to measure the time-averaged wall temperature field at three different Reynolds numbers ( Red = 3800, 7600 and 11,400) based on the rib height d and the mainstream velocity Uo , and wall-proximity configurations with four different gap ratios (gap size G over rib height d), G/ d = 0, 0.25, 0.50 and 0.75. The two-dimensional distribution of the normalized Nusselt number convincingly demonstrated the existence of a hot spot immediately behind the rib in the attached rib configuration ( G/ d = 0) and surface heat transfer augmentation in the reattachment zone. Among the three wall-proximity configurations, G/ d = 0.25 resulted in maximum heat transfer augmentation immediately behind the rib and overall improvement in surface heat removal. However, no distinctly different spatial patterns of the normalized Nusselt number distribution were found at the three different Reynolds numbers. A subsequent experiment examined the flow pattern and flow structures at Red = 7600 and three wall-proximity configurations ( G/ d = 0, 0.25 and 0.50). Velocity field measurements using PIV, along with complementary measurements using split-fiber film, gave a clear view of the flow pattern behind the rib; a very slender separation bubble with highly unsteady flow reversal was found close to the surface when G/ d = 0.25. For configurations with G/ d = 0.25 and 0.50, the high-speed jet issuing from the gap had a complicated influence on the interaction between the upper free shear layer and lower strong shear layer, resulting in slanted movement of the coupled wake flow. Proper orthogonal decomposition was used to identify the spatial characteristics of the superimposed flow

  2. Avaliação dO DESEMPENHO de um Pivô Central de Grande Porte e Baixa Pressão



    Full Text Available O sistema de irrigação Pivô Central tem proporcionado um significativo avanço da agricultura irrigada no Brasil. A grande aceitação do equipamento se deve às suas características, que permitem a irrigação mecanizada de extensas áreas, mesmo de topografia irregular, facilidade de utilização de práticas de quimigação, estrutura que não interfere nas operações agrícolas, e em relação ao manejo, possibilidade de aplicação de pequenas lâminas a intervalos reduzidos, além da grande vantagem de após completar um ciclo de irrigação, está no lugar exato para reiniciar outro ciclo. Este trabalho teve como objetivo determinar e analisar as características operacionais de um sistema pivô central de baixa pressão e de grande porte e vazão. Foram estudadas a uniformidade de distribuição e taxa de aplicação de água, distribuição de pressão, o deslocamento das torres e o manejo do equipamento em um sistema instalado na Fazenda Canadá, pertencente à Samambaia Empreendimentos Agrícolas, município de Santa Fé de Goiás (GO. Os resultados permitiram concluir que: 1 o sistema apresenta adequada uniformidade de distribuição de água; 2 a capacidade de aplicação de água é elevada; 3 a tubulação de grande diâmetro da lateral reduz a perda de carga e permite uma distribuição de pressão com menor amplitude de variação, comparável a sistemas de menor porte; 4 o sistema de propulsão com relé percentual de ciclo reduzido e alta velocidade de deslocamento das torres minimiza os efeitos de redução da uniformidade, reduz o tempo de giro e a lâmina por volta.The Center Pivot sprinkler irrigation system is giving a large contribution to the irrigation development in Brazil. The success of the equipment is due to the following reasons: this mechanized equipment can be used in large areas even with irregular topography; the possibility of fertigation associated with the fact of not interfering on agricultural

  3. Quantifying the flow dynamics of supercritical CO2-water displacement in a 2D porous micromodel using fluorescent microscopy and microscopic PIV

    Kazemifar, Farzan; Blois, Gianluca; Kyritsis, Dimitrios C.; Christensen, Kenneth T.


    The multi-phase flow of liquid/supercritical CO2 and water (non-wetting and wetting phases, respectively) in a two-dimensional silicon micromodel was investigated at reservoir conditions (80 bar, 24 °C and 40 °C). The fluorescent microscopy and microscopic particle image velocimetry (micro-PIV) techniques were combined to quantify the flow dynamics associated with displacement of water by CO2 (drainage) in the porous matrix. To this end, water was seeded with fluorescent tracer particles, CO2 was tagged with a fluorescent dye and each phase was imaged independently using spectral separation in conjunction with microscopic imaging. This approach allowed simultaneous measurement of the spatially-resolved instantaneous velocity field in the water and quantification of the spatial configuration of the two fluid phases. The results, acquired with sufficient time resolution to follow the dynamic progression of both phases, provide a comprehensive picture of the flow physics during the migration of the CO2 front, the temporal evolution of individual menisci, and the growth of fingers within the porous microstructure. During that growth process, velocity jumps 20-25 times larger in magnitude than the bulk velocity were measured in the water phase and these bursts of water flow occurred both in-line with and against the bulk flow direction. These unsteady velocity events support the notion of pressure bursts and Haines jumps during pore drainage events as previously reported in the literature [1-3]. After passage of the CO2 front, shear-induced flow was detected in the trapped water ganglia in the form of circulation zones near the CO2-water interfaces as well as in the thin water films wetting the surfaces of the silicon micromodel. To our knowledge, the results presented herein represent the first quantitative spatially and temporally resolved velocity-field measurements at high pressure for water displacement by liquid/supercritical CO2 injection in a porous micromodel.

  4. Infiltration of CO2 into Water-Saturated Two-Dimensional Porous Micromodels: New Insight from Microscopic Particle Image Velocimetry (μPIV) Experiments

    Kazemifar, F.; Blois, G.; Kyritsis, D. C.; Christensen, K. T.


    A novel experimental apparatus has been developed to study the interaction between liquid/supercritical CO2 and water in a two-dimensional porous micro-model. This flow process is very similar to what is encountered in many engineering applications such as sequestration of CO2 in geological formations (Carbon Capture and Sequestration, CCS) as well as enhanced oil recovery operations (EOR). Saline aquifers have very high potential for geological sequestration of CO2 based on several factors, including high capacity, economics and minimum environmental impact. Several CO2 injection and sequestration projects are currently in operation (e.g. Sleipner project in Norway), and numerous other projects are planned for the near future. While several studies exist on the large temporal- and spatial- scale effects of CO2 injection, the fluid-dynamic mechanisms at the pore-scale are largely unknown. In fact, recent studies suggest that such processes may be far more complex than previously addressed. CO2 and water/brine are immiscible, thus during the injection process of CO2 into a liquid-saturated porous structure, CO2 must displace the resident fluid. The lower viscosity and density of CO2 compared to water results in complex mechanisms of water displacement. While early studies focused on qualitative observations of fluid-fluid interactions, in this study, the microscopic particle image velocimetry (μPIV) technique is employed to quantify the flow fields within each fluid phase. The interface dynamics, migration and trapping mechanisms are of particular interest. In such flows, viscosity and interfacial tension are known as the main controlling parameters. In this regard, a challenging aspect of this work is that, in the vicinity of the critical point, these properties become very sensitive to changes in pressure and temperature. Additionally, despite the low Reynolds number of the flow, inertial effects are found to control the dynamics of flow patterns at the fluid

  5. PIV measurements of the flow at the inlet of a turbocharger centrifugal compressor with recirculation casing treatment near the inducer

    Gancedo, Matthieu; Gutmark, Ephraim; Guillou, Erwann


    Turbocharging reciprocating engines is a viable solution in order to meet the new regulations for emissions and fuel efficiency in part because turbochargers allow to use smaller, more efficient engines (downsizing) while maintaining power. A major challenge is to match the flow range of a dynamic turbomachine (the centrifugal compressor in the turbocharger) with a positive displacement pump (the engine) as the flow range of the latter is typically higher. The operating range of the compressor is thus of prime interest. At low mass flow rate (MFR), the compressor range is limited by the occurrence of surge. To control and improve it, numerous and varied methods have been used. Yet, an automotive application requires that the solution remains relatively simple and preferably passive. A common feature that has been demonstrated to improve the surge line is the use of flow recirculation in the inducer region through a circumferential bleed slot around the shroud, also called "ported shroud", similar to what has been developed for axial compressors in the past. The compressor studied here features such a device. In order to better understand the effect of the recirculation slot on the compressor functioning, flow measurements were performed at the inlet using particle image velocimetry and the results were correlated with pressure measurements nearby. Measurements were taken on a compressor with and without recirculation and across the full range of normal operation and during surge using a phase-locking method to obtain average flow fields throughout the entire surge cycle. When the recirculation is blocked, it was found that strong backflow develops at low MFR perturbing the incoming flow and inducing significant preswirl. The slot eliminated most of the backflow in front of the inducer making the compressor operation more stable. The measurements performed during surge showed strong backflow occurring periodically during the outlet pressure drop and when the


    张玮; 王元; 徐忠



  7. Qualidade da irrigação controlada por tensiômetros em pivô central Quality of center pivot irrigation controlled by tensiometers

    A.M. Saad


    Full Text Available A qualidade da irrigação foi avaliada durante a safra de inverno do ano de 1988 na cultura do feijoeiro (Phaseolus vulgaris L., irrigado por pivô central, em área de ocorrência de Latossolo Roxo (A moderado, textura argilosa a muito argilosa, distrófico, em Guaíra, SP. Os critérios utilizados para esta avaliação foram a eficiência do uso da água pela cultura e a efetividade da irrigação, esta última representada pela eficiência de aplicação da água, a uniformidade de distribuição da água sobre o solo e a eficiência de armazenagem da água no solo. O monitoramento das irrigações foi realizado através da instalação de 20 baterias de tensiômetros e 60 coletores de água de chuva e irrigação ao longo de uma transeção de 300 metros na direção radial do pivô. Os tensiômetros de cada bateria foram instalados a 15 cm e 30 cm de profundidade e espaçados entre si de 15 metros. Os coletores foram instalados a uma altura de 50 cm da superfície do terreno e distanciados entre si de 5 metros. O controle da irrigação foi feito com base na média ponderada dos 20 valores diários de potencial mátrico a 15 cm de profundidade, tendo como fator de ponderação a área representativa de cada tensiômetro. O valor mínimo de potencial mátrico estabelecido para a definição do momento da irrigação foi -0,06 MPa à profundidade de 15 cm e o valor da lâmina de água a ser aplicada em cada irrigação, calculado tendo-se em conta o valor de -0,008 MPa para o potencial mátrico a capacidade de campo. Os resultados obtidos mostraram que as irrigações efetuadas foram de alta qualidade uma vez que foram elevados os valores da eficiência de aplicação (80% e dos coeficientes de uniformidade de distribuição (94 e 91% calculados a partir das 16 irrigações acumuladas, o mesmo ocorrendo com a eficiência de armazenagem (95% e a eficiência de uso da água (0,8 kg/m³.The irrigation quality was evaluated for a center pivot

  8. Estabilidade temporal da distribuição espacial da umidade do solo em área irrigada por pivô central

    A. C. A. Gonçalves


    Full Text Available A heterogeneidade do solo faz com que o armazenamento de água seja variável, sendo necessária uma amostragem intensa, para caracterizar a sua distribuição espacial em uma área irrigada. Para fins de manejo da irrigação, é importante o monitoramento da umidade do solo durante o processo de secagem entre duas irrigações sucessivas. O presente trabalho tem por objetivos avaliar a estabilidade temporal da distribuição espacial da umidade do solo, a correlação da umidade com conteúdo de argila e avaliar se há estrutura de dependência espacial dessas variáveis. Quanto mais estável for a distribuição espacial da umidade e mais estreita a correlação com a textura, menos intensas poderão ser as amostragens para fins de controle das irrigações. Em área irrigada por pivô central, no campus da ESALQ/USP, de solo Podzólico Vermelho-Escuro, a umidade foi medida em pontos espaçados de 2,83 m ao longo de uma transeção radial, nas profundidades de 0,15 e 0,30 m, por meio de uma sonda de nêutrons. O conteúdo de argila e a densidade global foram também medidos. As medidas foram feitas durante um período de secagem do solo. A estabilidade temporal das distribuições espaciais foi avaliada por meio do coeficiente de correlação e da técnica de diferenças relativas. Foi constatada a persistência no tempo das distribuições de umidade, sendo possível identificar pontos de amostragem cujos valores permitem estimar a média geral da umidade na área, a qualquer momento. A dependência espacial da umidade foi avaliada por meio de semivariogramas, os quais mostraram que mais de 50% da variação dos dados pode ser atribuída à variação estruturada no espaço, cujo padrão se mantém estável no tempo e varia com a profundidade. Na camada inferior, a correlação espacial entre umidade e conteúdo de argila é descrita por semivariograma cruzado com efeito pepita nulo. A estrutura de dependência espacial pode ser usada no

  9. 3-D PIV Test of Inner Flow in a Double-blade Pump under Zero Flow Rate Condition%零流量工况下双叶片泵内部流场三维PIV测量

    王凯; 刘厚林; 袁寿其; 谈明高; 杨东升


    Inner flow in a double-blade pump impeller, whose specific speed is 111, was measured under zero flow rate condition by using 3-D PIV test technology. In order to ensure the accuracy of 3-D PIV test, the external trigger synchronization system which was made with fiber optic and equivalent calibration method was applied. In Visual C+ + 2005 platform, according to the velocity triangle, 3-D PIV velocity synthetic procedure was compiled to obtain the relative velocity synthesized by the absolute velocity and the circular velocity. The results showed that volute tongue had greater impact on the absolute velocity field within the impeller. There were vortices regions at three measurement surfaces within impeller, but the sizes and locations of vortices were different. Moreover, there was a low velocity region at the volute diffuser, the absolute velocity values in the region were less than 0. 62 m/s, and there were vortices at the volute diffuser. The axial velocities values of impeller passage, volute diffuser and region near volute tongue were different at three measurement planes.%采用三维PIV测试技术对一比转数为111的双叶片泵零流量工况下的内部流动进行了测量.采用基于光纤制作的外触发同步系统和等效标定方法等关键技术来保证三维PIV测试精度.在Visual C++2005平台下,根据速度三角形,编写了三维PIV速度合成程序,将测量的绝对速度与圆周速度合成得到相对速度.结果表明:隔舌对叶轮内绝对速度场影响较大;叶轮流道内3个测量平面上都存在较大范围的漩涡区,但漩涡的大小、位置有所不同;蜗壳扩散段存在低速区域,该区域的绝对速度小于0.62 m/s,且存在漩涡现象;3个测量平面上,叶轮流道内、蜗壳扩散段及隔舌附近区域的轴向速度各不相同.

  10. Desempenho e uniformidade da distribuição de água de um pivô central Performance of a center pivot irrigation system and irrigation distribution uniformity

    Vitor Hugo Cainelli


    Full Text Available O objetivo deste experimento foi avaliar as características de desempenho de um equipamento de irrigação pivô central, de baixa pressão, bem como determinar a uniformidade de distribuição de água, tanto abaixo como acima da superfície do solo. Para a avaliação do desempenho do sistema utilizaram-se os coeficientes de uniformidade de Christiansen (CUC e de distribuição (CUD, calculados a partir de dados da precipitação dos aspersores. O pivô central foi ensaiado nas velocidades de 25%, 50%, 75% e 100% da velocidade máxima de deslocamento do equipamento. Utilizou-se quatro linhas de coletores, uniformemente espaçados. Os valores encontrados do CUC e o CUD foram superiores ao mínimo recomendado para a cultura do milho, confirmando o bom desempenho do pivô central. Em todas as profundidades do solo estudadas os coeficientes de uniformidade foram superiores aos obtidos acima do solo, ocorrendo um aumento nos valores dos coeficientes de uniformidade abaixo da superfície do solo com o tempo.The objective of this work was to evaluate some characteristics of a center pivot irrigation system equipament, as well as to determine the water distribuition uniformity, under and over the soil surface. The Christiansen uniformity coefficient (CUC and distribuition (CUD were used to evaluate the system. A low pressure center pivot was tested in four different speeds: 25%, 50%, 75% and 100% of the timer sensor, and in four collectors Unes spaced. Results indicated that both coeficients presented good performance. The values of CUC and CUD were above the minimum recommended for na irrigated corn field. The uniformity coefficients in all depths of the soil were higher than the above the soil surface. Howerer, the uniformity under soil surface increased with the time in all depths.

  11. Circadian transcription factor BMAL1 regulates innate immunity against select RNA viruses.

    Majumdar, Tanmay; Dhar, Jayeeta; Patel, Sonal; Kondratov, Roman; Barik, Sailen


    BMAL1 (brain and muscle ARNT-like protein 1, also known as MOP3 or ARNT3) belongs to the family of the basic helix-loop-helix (bHLH)-PAS domain-containing transcription factors, and is a key component of the molecular oscillator that generates circadian rhythms. Here, we report that BMAL1-deficient cells are significantly more susceptible to infection by two major respiratory viruses of the Paramyxoviridae family, namely RSV and PIV3. Embryonic fibroblasts from Bmal1(-/-) mice produced nearly 10-fold more progeny virus than their wild type controls. These results were supported by animal studies whereby pulmonary infection of RSV produced a more severe disease and morbidity in Bmal1(-/-)mice. These results show that BMAL1 can regulate cellular innate immunity against specific RNA viruses.

  12. Développement d'instabilités dans un écoulement subsonique se développant au-dessus d'une cavité mesures synchronisées PIV-LDV

    Faure, T; Pethieu, R; Debesse, P; Faure, Thierry; Pastur, Luc; Pethieu, Romain; Debesse, Philippe


    A boundary layer interacting with a cavity is a benchmark case that is present in environmental applications, aeronautics, automobile aerodynamics or industrial applications, where the velocity over a rectangular cavity is relatively low. In the present investigation, the interaction between a laminar boundary layer with external velocity Ue and an open cavity is investigated experimentally for medium range Reynolds numbers (between 4600 and 18500) with flow diagnostics optical methods, for a cavity aspect ratio (length over depth) of two. A shear layer induces a main vortex and a counter-rotating secondary vortex inside the cavity. The shear layer also develops instabilities interacting with the downstream cavity edge. Particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) measurements are synchronized in order to get global information of both spatial velocity fields and time-resolved signals in a particular position situated downstream of the development of the shear layer above the cavity. T...

  13. Experimental study on the evolution of heavy gas cylinder under reshock condition by PIV method%反射激波作用下重气柱界面演化的PIV研究

    张赋; 翟志刚; 司廷; 罗喜胜


    Evolution of a membrane-less heavy (SF6 )gas cylinder under reshock condition is experimentally investigated in a horizontal shock tube with particle image velocimetry (PIV ) method.As a fundamental interface configuration,gas cylinder evolution impinged by a single shock wave is extensively investigated while the related research under reshock condition is sel-dom performed.Illuminated by a continuous laser sheet,the interface morphology after the inci-dent shock and reshock impact is characterized by glycol droplets and captured by a high-speed camera.The generation and development of counter-rotating vortex pair after incident shock im-pact is observed and secondary vortex rings,which have opposite rotating directions with the o-riginal vortex rings,are generated after the reshock passage because of the opposite pressure gra-dient induced by reshock compared with the incident shock.Because the velocity of the flow field after reshock is very small,the PIV measurement based on the Matpiv procedure is employed to capture the flow field after reshock.The continuous velocity and vorticity fields are obtained with the help of the continuous light source and high speed camera.Compared with the PIV algorithm based on the double-exposure technique,continuous velocity field can be obtained in a single test run based on the high-speed technique in this experiment.The circulation derived from PIV measurements is compared with the existed analytical model and a good agreement is achieved, which validates the feasibility of the experimental method.%在水平激波管中采用PIV方法研究了反射激波作用下SF6重气柱界面的发展演化。采用射流方法形成SF6无膜气柱界面,并以乙二醇作为示踪粒子。利用连续激光片光源结合高速摄影相机对流场进行显示,得到了反射激波作用下SF6气柱界面的发展过程。结果表明,入射激波的冲击会在界面上产生反向旋转的涡环结构,而反射激波的作

  14. Application of PIV in Research of Internal Flow Field Measurement of Separation Machinery%PIV在分离机械内流场测量研究中的应用

    杨萍; 张总



  15. 内燃机燃烧室流场PIV测试中示踪粒子跟随性分析%Analyses of following behaviors as tracer particle by PIV in chamber of internal combustion engine

    梁桂华; 赵宇


    从紊流理论出发,对处于紊流流场中的示踪粒子进行受力分析,根据粒子图像测速(PIV)中的实际要求与BBO(Basset-Boussinesq-Oseen)方程的不同,建立了紊流流场中示踪粒子的模型;推导出适应内燃机燃烧室流场PIV测试的示踪粒子跟随性计算公式,得出在该实验条件下,示踪粒子直径小于19.2 μm时,PIV测试会取得较好结果.

  16. Regulating Transplants


    Legislation to determine brain death is viewed as essential in controlling the organ transplant industry Organ transplant represents a very sensitive and complicated issue. Experts say the temporary administrative regulations recently promulgated by the Central Government are an important step, but relevant laws and regulations must follow. Among these, the

  17. Tripartite Motif-Containing Protein 22 Interacts with Class II Transactivator and Orchestrates Its Recruitment in Nuclear Bodies Containing TRIM19/PML and Cyclin T1

    Greta Forlani


    Full Text Available Among interferon (IFN inducible antiviral factors both tripartite motif-containing protein 22 (TRIM22 and class II transactivator (CIITA share the capacity of repressing human immunodeficiency virus type 1 (HIV-1 proviral transcription. TRIM22 is constitutively expressed in a subset of U937 cell clones poorly permissive to HIV-1 replication, whereas CIITA has been shown to inhibit virus multiplication in both T lymphocytic and myeloid cells, including poorly HIV-1 permissive U937 cells, by suppressing Tat-mediated transactivation of HIV-1 transcription. Therefore, we tested whether TRIM22 and CIITA could form a nuclear complex potentially endowed with HIV-1 repressive functions. Indeed, we observed that TRIM22, independent of its E3 ubiquitin ligase domain, interacts with CIITA and promotes its recruitment into nuclear bodies. Importantly, TRIM19/promyelocytic leukemia (PML protein, another repressor of HIV-1 transcription also acting before proviral integration, colocalize in these nuclear bodies upon TRIM22 expression induced by IFN-γ. Finally, tTRIM22 nuclear bodies also contained CyclinT1, a crucial elongation factor of HIV-1 primary transcripts. These findings show that TRIM22 nuclear bodies are a site of recruitment of factors crucial for the regulation of HIV-1 transcription and highlight the potential existence of a concerted action between TRIM22, CIITA, and TRIM19/PML to maintain a state of proviral latency, at least in myeloid cells.

  18. NORM regulations

    Gray, P. [ed.


    The author reviews the question of regulation for naturally occuring radioactive material (NORM), and the factors that have made this a more prominent concern today. Past practices have been very relaxed, and have often involved very poor records, the involvment of contractors, and the disposition of contaminated equipment back into commercial service. The rationale behind the establishment of regulations is to provide worker protection, to exempt low risk materials, to aid in scrap recycling, to provide direction for remediation and to examine disposal options. The author reviews existing regulations at federal and state levels, impending legislation, and touches on the issue of site remediation and potential liabilities affecting the release of sites contaminated by NORM.

  19. 膜生物反应器内流场动力学特性的PIV实验研究%Research on dynamics characteristics of flow field in MBR by PIV technology

    李春丽; 田瑞; 陶中兰; 文佳龙


    The dynamic characteristic of gas-liquid two phase flow around membrane fibers have important effects on controlling concentration polarization and membrane pollution in submerged membrane bioreactor system. Particle image velocimetry (PIV) technology was used to measure the dynamic characteristic of liquid phase flow around membrane fibers. First, the gas-liquid two phase flow field image was gained by PIV technology, gray resolution method was developed and implemented to discriminate liquid phase velocity field from two phase flow field image, and vorticity field data of liquid flow was calculated around membrane fibers by Tecplot. We analyzed the liquid phase flow field and calculated vorticity field data around membrane fibers under the condition of aeration intensity of 2. 5,3. 0,3. 5,4. 5,5. 5 and 6. 5 m3 /h in bore diameter of 3 mm. It was shown that aeration intensity affected liquid phase flow field and vorticity field greatly, increasing aeration intensity in a certain range can make the liquid velocity and vorticity increase. Under the experimental conditions, the optimal aeration intensity identified as 6. 5 m3/h. At the same time, we also analyzed dynamics characteristics of bubble with bore diameter of 3 mm. The study provides experimental data and research experience for optimization design of membrane bio-reactor (MBR).%浸没式膜生物反应器系统内膜面附近的气液两相流动力学特性对控制浓差极化和膜污染具有重要影响.应用粒子图像测速(PIV)技术对浸没式膜生物反应器内近膜面的液相流场动力学特性进行了研究.采用相分离技术灰度分辨法将通过PIV技术得到的气液两相流场图像中的液相速度场进行辨别,得到膜面附近的液相流场数据,并应用Tecplot软件计算得出液相流的涡量特性.在3 mm曝气孔径,2.5、3.0、3.5、4.5、5.5和6.5 m3/h 6种曝气强度下分析了膜面附近的液相速度场和涡量场.结果表明,曝气强度对液

  20. Economic viability of retrofiting emitters in center pivot irrigation systems Viabilidade econômica da troca de emissores em sistemas de irrigação tipo pivô central

    Cornélio A. Zolin


    Full Text Available Although several studies have been conducted to evaluate the uniformity of water application under center pivot irrigation systems, there are few studies concerning the economic perspective of such coefficient. The aim of this study is to present a methodology to accomplish an economic analysis as support for the decision-making to retrofit emitters in center pivot irrigation systems, and to attribute an economic meaning to the uniformity coefficient of water application taking into account the response function productivity to the amount of water applied and the sale price of the crops. In the hypothetic calculation example considering the variation of revenue of potato crop under center pivot irrigation system, it was verified that the area with uniformity coefficient of water application of 90% brought an income increase of BR$ 1,992.00, considering an area about 1,0 ha. Thus, it can be concluded that the methodology presented has met the objectives proposed in the study and made it possible to attribute an economical meaning to the coefficient of water uniformity application.Embora vários estudos tenham sido conduzidos para a avaliação da uniformidade de aplicação de água por equipamentos de irrigação do tipo pivô central, são escassos os trabalhos que tenham analisado de um ponto de vista econômico o significado de tal coeficiente. Objetivou-se com o presente trabalho apresentar uma metodologia de análise econômica como auxílio na tomada de decisão para troca de emissores de sistemas de irrigação tipo pivô central e atribuir um significado econômico ao coeficiente de uniformidade de aplicação de água, levando-se em consideração a função de resposta da cultura à lâmina de água aplicada e o preço de venda dos produtos agrícolas. No exemplo hipotético de cálculo, considerando-se a diferença na renda obtida com a cultura da batata irrigada com coeficiente de uniformidade de 90% e 70%, respectivamente, verificou