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Sample records for surface-piercing hydrofoil strut

  1. Modified Contact Line Dynamics about a Surface-Piercing Hydrofoil

    Science.gov (United States)

    Grivel, Morgane; Jeon, David; Gharib, Morteza

    2016-11-01

    The contact line around a surface-piercing hydrofoil is modified by introducing alternating hydrophobic and hydrophilic bands along one side of the body. These bands are either aligned perpendicular or parallel to the flow direction. The other side of the hydrofoil is un-patterned and retains its original, uniformly hydrophilic properties. The hydrofoil is mounted onto air bearings, such that it can freely move side-to-side in the water tunnel. A force sensor is attached to the setup via a universal joint in order to measure the forces acting on the body for several Reynolds numbers (ranging from 104 to 105) and angles of attack (ranging from -10o to 10o) . Cameras are also used to record the resulting flow structures and free surface elevation. The generation of wave trains and an altered free-surface elevation (also associated with the generation of surface waves) are observed over a wide range flow conditions. Force measurements elucidate how introducing these flow features impacts the forces acting on the hydrofoil, specifically with regards to the generation of lateral forces due to the asymmetric wetting conditions on either side of the hydrofoil. Work is funded by ONR Grant N00014-11-1-0031 and NSF GRFP Grant DGE-1144469.

  2. Control of a flexible, surface-piercing hydrofoil for high-speed, small-scale applications

    Science.gov (United States)

    Bousquet, Gabriel; Triantafyllou, Michael; Slotine, Jean-Jacques

    2016-11-01

    In recent years, hydrofoils have become ubiquitous in the design of high performance surface vehicles such as sailboats. They have proven particularly useful at small scales: while the speed of displacement-hull sailboats of length L is limited by their hull speed √{ gL } , due to wave making resistance, such limitations do not apply to hydrofoil crafts and sailboats. Such crafts of length O(1 - 10 m) are capable of reaching speeds in excess of 45 kts, often far faster than the wind. Besides, in the quest for super-maneuverability, actuated hydrofoils enable the efficient generation and control of large forces. With the intent to ultimately enable the design of small-scale, high-speed, and super-maneuverable surface vehicles, we investigate the problem of controlling the lift force generated by a flexible, surface-piercing hydrofoil traveling at high speed through a random wave field. We design a test platform composed of a rudder-like vertical foil, which is actuated in pitch, and instrumented with velocity, force, and immersion sensors. We present a feedback linearization controller, designed to operate over a wide range of velocities and sea states. Validation experiments are carried out on-the-field at speeds ranging from 3 to 10+m/s.

  3. Analysis of Ventilation Regimes of the Oblique Wedge-Shaped Surface Piercing Hydrofoil During Initial Water Entry Process

    Directory of Open Access Journals (Sweden)

    Ghadimi Parviz

    2018-03-01

    Full Text Available The suction side of a surface piercing hydrofoil, as a section of a Surface Piercing Propeller (SPP, is usually exposed to three phases of flow consisting air, water, and vapour. Hence, ventilation and cavitation pattern of such section during the initial phase of water entry plays an essential role for the propeller’s operational curves. Accordingly, in the current paper a numerical simulation of a simple surface piercing hydrofoil in the form of an oblique wedge is conducted in three-phase environment by using the coupled URANS and VOF equations. The obtained results are validated against water entry experiments and super-cavitation tunnel test data. The resulting pressure curves and free surface profiles of the wedge water entry are presented for different velocity ratios ranging from 0.12 to 0.64. Non-dimensional forces and efficiency relations are defined in order to present the wedge water entry characteristics. Congruent patterns are observed between the performance curves of the propeller and the wedge in different fully ventilated or partially cavitated operation modes. The transition trend from fully ventilated to partially cavitated operation of the surface piercing section of a SPP is studied and analyzed through wedge’s performance during the transitional period.

  4. Design of a High Speed Planing Hull with a Cambered Step and Surface Piercing Hydrofoils

    Science.gov (United States)

    2014-06-01

    Knowing that the planing hull is symmetric, and accounting for the symmetry plane benefits, the inertial reference frame was cut in half, as...performing waterjet . a1=3.19e-1; %max = 3.81e-1 b=-2.25e-2; %max= -2.09e-2 c=-1.04e-3; %max = -3.84e-4 d=2.01e-4; %max = 2.05e-4

  5. An efficient domain decomposition strategy for wave loads on surface piercing circular cylinders

    DEFF Research Database (Denmark)

    Paulsen, Bo Terp; Bredmose, Henrik; Bingham, Harry B.

    2014-01-01

    A fully nonlinear domain decomposed solver is proposed for efficient computations of wave loads on surface piercing structures in the time domain. A fully nonlinear potential flow solver was combined with a fully nonlinear Navier–Stokes/VOF solver via generalized coupling zones of arbitrary shape....... Sensitivity tests of the extent of the inner Navier–Stokes/VOF domain were carried out. Numerical computations of wave loads on surface piercing circular cylinders at intermediate water depths are presented. Four different test cases of increasing complexity were considered; 1) weakly nonlinear regular waves...

  6. Comparative CFD Investigation on the Performance of a New Family of Super-Cavitating Hydrofoils

    Science.gov (United States)

    Brizzolara, S.; Bonfiglio, L.

    2015-12-01

    We present a CFD characterization of a new type of super-cavitating hydrofoil section designed to have optimal performance both in super-cavitating conditions and in sub-cavitating conditions (including transitional regime). The basic concepts of the new profile family are first introduced. Lift, drag and cavity shapes at different cavitation numbers are calculated for a new foil and compared with those of conventional sub-cavitating and super-cavitating profiles. Numerical calculations confirm the superior characteristics of the new hydrofoil family, which is able to attain high lift and efficiency both in sub-cavitating and super-cavitating conditions. Numerical calculations are based on a multi-phase fully turbulent URANSE solver with a bubble dynamic cavitation model to follow the generation and evaporation of the vapor phase. The new profile family, initially devised for ultra-high speed hydrofoil crafts, may result useful for diverse applications such as super-cavitating or surface-piercing propellers or high-speed sailing boats.

  7. Cavitation on hydrofoils with sinusoidal leading edge

    Science.gov (United States)

    Johari, H.

    2015-12-01

    Cavitation characteristics of hydrofoils with sinusoidal leading edge were examined experimentally at a Reynolds number of 7.2 × 105. The hydrofoils had an underlying NACA 634-021 profile and an aspect ratio of 4.3. The sinusoidal leading edge geometries included three amplitudes of 2.5%, 5%, and 12% and two wavelengths of 25% and 50% of the mean chord length. Results revealed that cavitation on the leading edge-modified hydrofoils existed in pockets behind the troughs whereas the baseline hydrofoil produced cavitation along its entire span. Moreover, cavitation on the modified hydrofoils appeared at consistently lower angles of attack than on the baseline hydrofoil.

  8. Theoretical motions of hydrofoil systems

    Science.gov (United States)

    Imlay, Frederick H

    1948-01-01

    Results are presented of an investigation that has been undertaken to develop theoretical methods of treating the motions of hydrofoil systems and to determine some of the important parameters. Variations of parameters include three distributions of area between the hydrofoils, two rates of change of downwash angle with angle of attack, three depths of immersion, two dihedral angles, two rates of change of lift with immersion, three longitudinal hydrofoil spacings, two radii of gyration in pitching, and various horizontal and vertical locations of the center of gravity. Graphs are presented to show locations of the center of gravity for stable motion, values of the stability roots, and motions following the sudden application of a vertical force or a pitching moment to the hydrofoil system for numerous sets of values of the parameters.

  9. Differences in Scour for Submerged and Surface Piercing Circular Cylinders in Tandem

    Science.gov (United States)

    Pulvino, N. T.; Riley, D.; Beninati, M. L.; Krane, M.; Fontaine, A.

    2012-12-01

    An experimental study was conducted to investigate how the scour hole of surface piercing and submerged cylinders in tandem is affected by the separation of the cylinders. The study was motivated by the need to predict the environmental effects of Marine Hydrokinetic (MHK) turbines arrays where the cylinders used represent the bluff bodies of MHK turbines. Small scale experiments were performed to find scour rate and scour statistics; including: scour size and deposition. The cases studied were tandem cylinders separated by 1, 2, 3, 4, 6, 8, 10, and 12 diameters (D = 2.54 cm). These studies were performed in a test section in the hydraulic flume facility (1.22-m-wide, 0.38-m-deep, and 9.75-m-long) at Bucknell University. The bottoms of each cylinder tested were taped in 0.318 cm color-coded increments and buried beneath the sediment. This allowed for visual determination of the scour rate by looking at how many strips had been uncovered at intervals over three hours of testing at live bed conditions. Subsequently, bed form topology was measured using an HR Wallingford 2D Sediment Bed Profiler with a low-powered laser distance sensor. Results show that surface piercing cylinders in tandem consistently have a wider scour hole than submerged cylinders. Furthermore, it is determined that the threshold for when the tandem cylinders have separate scour holes occurring at a separation of 10 diameters for both sets of cylinders.

  10. Cavitating Hydrofoils: A Perspective

    Science.gov (United States)

    Arndt, Roger E. A.; Kawakami, Damien T.; Qin, Qiao; Song, Charles C. S.

    2004-11-01

    This paper reviews our recent research that is aimed at gaining a better understanding of the problem of unsteady cavitating flows on lifting surfaces. We have explored this issue with extensive numerical and experimental investigations. This includes the development of new numerical models of cavitating flows including the effects of dissolved incondensable gas and ventilation. Our simulations are based on a virtual single-phase cavitation model, that incorporates the assumptions of fully compressible and barotropic flow coupled with a Large-Eddy Simulation (LES) approach. This approach has proven to be capable of capturing the complex dynamical features of highly unsteady cavitating flows. Experimental data are drawn from experiments carried out at two different scales in two different water tunnels; one in the US at the Saint Anthony Falls Laboratory (SAFL) and the other at the Versuchsanstalt fur Wasserbau (VFW) in Obernach, Germany. Several foils shapes have been examined. Examples are drawn from investigations of several different type hydrofoils. The tests were designed to complement each other and to capitalize on the special features of each facility. Suuported by the National Science Foundation.

  11. Dynamic Behaviour of Ventilated Hydrofoils.

    Science.gov (United States)

    Kjeldsen, Morten; Arndt, Roger; Wosnik, Martin

    2006-11-01

    In certain types of pumping applications oscillations are induced by operation with liquids containing a free gas load. In order to understand the physics of this process, a series of tests with a ventilated A 2D NACA 0015 hydrofoil were performed in the water tunnel at the St. Anthony Falls Laboratory of the University of Minnesota. The special bubble removal feature of the water tunnel allowed continuous ventilation without experiencing visible bubbles upstream the hydrofoil. These studies build on previous work on cavitation-induced oscillations. Gas injection studies were made over a range of gas flow rates and test section pressure. The results clearly show that lift oscillations increase in intensity when the gas load is increased. The point of maximum unsteadiness is also associated the rapid decline of the foil performance as measured as average lift. Further increase of the gas injection load gives a steady behaviour with almost no lift. These experiments are compared with traditional cavitation experiments. The similarities between gas injection- and cavitation induced unsteadiness on the hydrofoil are many, but the amplitude of lift oscillations found on the foil with gas injection corresponds to about 50% of that found for cavitating hydrofoils. The fact that the oscillations are periodic leads to the consideration of both passive and active control.

  12. Composite Struts Would Damp Vibrations

    Science.gov (United States)

    Dolgin, Benjamin P.

    1991-01-01

    New design of composite-material (fiber/matrix laminate) struts increases damping of longitudinal vibrations without decreasing longitudinal stiffness or increasing weight significantly. Plies with opposing chevron patterns of fibers convert longitudinal vibrational stresses into shear stresses in intermediate viscoelastic layer, which dissipate vibrational energy. Composite strut stronger than aluminum strut of same weight and stiffness.

  13. Applications of Hydrofoils with Leading Edge Protuberances

    Science.gov (United States)

    2012-03-30

    APPLICATIONS OF HYDROFOILS WITH LEADING EDGE PROTUBERANCES Final Technical Report for Office of Naval Research contract...To) 03/30/2012 Final Technical Report 01-08-2008 to 31-12-2011 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Applications of Hydrofoils with Leading...AVAILABILITY STATEMENT Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The leading edge modified hydrofoils

  14. Cavitating Flow over a Mini Hydrofoil

    International Nuclear Information System (INIS)

    Luo Xian-Wu; Ji Bin; Xu Hong-Yuan; Zhang Yao

    2012-01-01

    We consider a cavitating flow over a mini hydrofoil (foil profile: Clark-Y-11.7) having a 14 mm chord length in a cavitation tunnel at various cavitation numbers. Experimental observations show that cavitating flows over a miniature hydrofoil display several types of cavitation behavior, such as cavitation inception, sheet cavitation, cloud cavitation and super cavitation with the decreasing cavitation number. Under the same cavitation conditions, cavitation over a mini hydrofoil would be suppressed in comparison to cavitation over an ordinary hydrofoil. This cavitation scale effect is suspected to be caused by the Reynolds number. (condensed matter: structure, mechanical and thermal properties)

  15. Differences in scour around a single surface-piercing cylinder and a submerged cylinder

    Science.gov (United States)

    Beninati, M. L.; Volpe, M. A.; Riley, D. R.; Krane, M.

    2011-12-01

    The equilibrium state of scour for a single surface piercing cylinder and a submerged cylinder of specific aspect ratio are presented. The equilibrium state is defined by a scour depth and associated time interval for a given set of flow conditions. Control variables such as sediment coarseness (or grain size) and cylinder size are held constant, while the flow intensity is varied. Sediment bed form topology is characterized with a series of two-dimensional slices across the bed for both the surface-piercing and submerged cylinder cases. Test results will help identify the geometry and pattern of the scour around the cylinders to aid in the optimal design of marine hydrokinetic (MHK) support structures in an effort to help minimize the deleterious impact of these devices on the local substrate. This study is performed in the small-scale testing platform in the hydraulic flume facility (32 ft long, 4 ft wide and 1.25 ft deep) in the Environmental Fluid Mechanics and Hydraulics Laboratory (EFM&H) at Bucknell University. The cylinders, of the same material and diameter, are placed centrally in the sediment filled test section (2.5 ft long, 2 ft wide and 0.75 ft deep) of the platform. Flow field measurements are taken with a 16-MHz Micro Acoustic Doppler Velocimeter while water depth is acquired using an ultrasonic distance sensor. These devices are attached to a gantry system that can be accurately positioned anywhere in the test section. Clear-water conditions (in the absence of live-bed scour) are maintained to study the effect of the horseshoe and wake vortices on the displacement of sediment around the cylinder as well as downstream of the device. Bed form topology is measured using an HR Wallingford 2D Sediment Bed Profiler with a low-powered laser distance sensor to accurately characterize changes in bed form around the cylinders. Additionally, specifications for testing such as operational procedures for start-up and shut-down of the facility are given.

  16. Hydrofoils: optimum lift-off speed for sailboats.

    Science.gov (United States)

    Baker, R M

    1968-12-13

    For a hydrofoil sailboat there is a unique optimum lift-off speed. Before this speed is reached, if there are no parasitic vertical hydrofoil appendages, the submerged or partially submerged hydrofoils increase drag and degrade performance. As soon as this speed is reached and the hydrofoils are fully and promptly deployed, the performance of a hydrofoil-borne craft is significantly improved. At speeds exceeding optimum lift-off speed, partially submerged hydrofoils impair performance if there is no significant effect of loading on the hydrofoil lift-to-drag ratio.

  17. Analysis of user perception of hydrofoil service

    Science.gov (United States)

    1983-06-01

    This memorandum presents the findings from a survey of hydrofoil passengers in Southern Italy. This hydrofoil service links the ports of Palermo and Naples with a stop in Ustica, a resort island off the northern coast of Sicily. The vessel used in th...

  18. Water Surface Ripples Generated by the Turbulent Boundary Layer of a Surface-Piercing Moving Wall

    Science.gov (United States)

    Washuta, N.; Masnadi, N.; Duncan, J. H.

    2014-11-01

    Free surface ripples created by subsurface turbulence along a surface-piercing moving wall are studied experimentally. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. One of the two 7.5-m-long belt sections between the rollers is in contact with the water in a large open-surface water tank and the water level is adjusted so that the top of the belt pierces the water free surface. The belt is launched from rest with a 3 g acceleration in order to quickly reach a steady state velocity. This belt motion creates a temporally evolving boundary layer analogous to the spatially evolving boundary layer created along the side of a ship hull moving at the belt velocity, with a length equivalent to the length of belt that has passed the measurement region. The water surface ripples generated by the subsurface turbulence are measured in a plane normal to the belt using a cinematic LIF technique. It is found that the overall RMS surface fluctuations increase linearly with belt speed and that the spatial distributions of the fluctuations show a sharp increase near the wall. The support of the Office of Naval Research is gratefully acknowledged.

  19. Kajian Eksperimental Pengaruh Posisi Perletakan Hydrofoil Pendukung Terhadap Hambatan Kapal

    OpenAIRE

    Saputro, Slamet Agus; Suastika, Ketut

    2012-01-01

    Penggunaan hydrofoil merupakan salah satu cara untuk bisa mengurangi hambatan kapal pada kondisi kecepatan yang direncanakan. Gaya lift yang dimiliki hydrofoil dapat mengurangi WSA kapal pada kondisi foilborne sehingga hambatan yang diterima hanya akan dipengaruhi oleh sistem hydrofoil itu sendiri. Dalam perencanaan hydrofoil perlu dipertimbangkan gaya lift dan drag yang dihasilkan sehingga drag hydrofoil dapat lebih kecil daripada hambatan barehull planing pada kecepatan yang direncanakan. D...

  20. Lift and Drag Measurements of Superhydrophobic Hydrofoils

    Science.gov (United States)

    Sur, Samrat; Kim, Jeong-Hyun; Rothstein, Jonathan

    2015-11-01

    For several years, superhydrophobic surfaces which are chemically hydrophobic with micron or nanometer scale surface features have been considered for their ability to reduce drag and produce slip in microfluidic devices. More recently it has been demonstrated that superhydrophobic surfaces reduce friction coefficient in turbulent flows as well. In this talk, we will consider that modifying a hydrofoil's surface to make it superhydrophobic has on the resulting lift and drag measurements over a wide range of angles of attack. Experiments are conducted over the range of Reynolds numbers between 10,000hydrofoil is made superhydrophobic. The hydrofoils are coated Teflon that has been hot embossed with a 325grit stainless steel woven mesh to produce a regular pattern of microposts. In addition to fully superhydrophobic hydrofoils, selectively coated symmetrical hydrofoils will also be examined to study the effect that asymmetries in the surface properties can have on lift and drag. Partially funded by NSF CBET-1334962.

  1. Jakarta Struts Pocket Reference

    CERN Document Server

    Cavaness, Chuck

    2003-01-01

    Web tier frameworks have soared in popularity over the past year or so due to the increasing complexity of Java itself, and the need to get more work done with fewer resources. Developers who used to spend hours and hours writing low-level features can use a well-written framework to build the presentation tier so they start coding the "good stuff" sooner--the business logic at the core of the program. The Jakarta Struts Framework is one of the most popular presentation frameworks for building web applications with Java Servlet and JavaServer Pages (JSP) technologies. If you work with the St

  2. Harnessing Energy from Arrays of Oscillating Hydrofoils

    Science.gov (United States)

    Simeski, Filip; Spaulding, Arianne; Franck, Jennifer

    2016-11-01

    Computational Fluid Dynamics (CFD) simulations are performed on multiple-hydrofoil systems for the application of energy harvesting. Oscillating hydrofoils generate power through a coupled heaving and pitching motion. Various linear and staggered configurations consisting of three to four hydrofoils are simulated, and the system efficiency of the array is evaluated, as well as the energy density of the system. Of particular interest is the observation that regular vortices from the foils' leading and trailing edges develop into a well-structured wake affecting performance of downstream-located hydrofoils in the system, and leading to an optimal phase difference between foils. Simulations are performed at a Reynolds number of 1000, and utilize OpenFOAM with dynamic meshing libraries employed to handle the foil motion.

  3. Shape Optimization of an Hydrofoil by Isogeometric Analysis

    OpenAIRE

    Simeoni, Matthieu Martin Jean-Andre

    2014-01-01

    We use Isogeometric Analysis as a framework for NURBS-based shape optimization of hydrofoils. We present geometrical representations by NURBS and some of their properties to design an hydrofoil. Then, we consider an irrotational flow around an hydrofoil and solve the Laplace equation in the stream function formulation. Finally, we perform the shape optimization of the hydrofoil by considering the stream function formulation as the state problem and different objective functionals.

  4. Kajian Eksperimental Pengaruh Posisi Perletakan Hydrofoil Pendukung Terhadap Hambatan Kapal

    Directory of Open Access Journals (Sweden)

    Slamet Agus Saputro

    2012-09-01

    Full Text Available Penggunaan hydrofoil merupakan salah satu cara untuk bisa mengurangi hambatan kapal pada kondisi kecepatan yang direncanakan. Gaya lift yang dimiliki hydrofoil dapat mengurangi WSA kapal pada kondisi foilborne sehingga hambatan yang diterima hanya akan dipengaruhi oleh sistem hydrofoil itu sendiri. Dalam perencanaan hydrofoil perlu dipertimbangkan gaya lift dan drag yang dihasilkan sehingga drag hydrofoil dapat lebih kecil daripada hambatan barehull planing pada kecepatan yang direncanakan. Dalam penelitian ini mengkaji pengaruh dari posisi perletakan hydrofoil terhadap hambatan kapal. Penelitian ini dilakukan di towing tank dengan memvariasikan antara jarak hydrofoil depan dan belakang terhadap titik berat kapal variasi 1 la/lb = 0,3, variasi 2 la/lb = 1,15 dan variasi 3 la/lb = 2. Dari hasil pengujian towing tank terhadap hambatan total, dapat diketahui bahwa untuk variasi 2 memiliki nilai Rt = 22,46 KN lebih rendah dibandingkan dengan variasi lainnya variasi 1 Rt = 22,76 KN dan variasi 3 Rt = 30,31 KN. Penempatan hydrofoil pada variasi 3 la/lb = 2 terjadi perbedaan momen yang sangat besar sehingga mengakibatkan haluan kapal yang disangga oleh hydrofoil bagian depan lebih mudah terangkat daripada bagian buritan. Hal ini menyebabkan terjadinya hentakan pada hydrofoil bagian depan terhadap permukaan air secara  berkelanjutan pada Fn > 0,7.

  5. Numerical Investigation Cavitation Buckets for Hydrofoil Parametrically

    Directory of Open Access Journals (Sweden)

    Mehmet Salih KARAALİOĞLU

    2015-12-01

    Full Text Available Cavitation is a general fluid mechanics phenomenon that is appeared in system such as pumps, turbines, marine propellers and hydrofoils which induces pressure and velocity fluctuation in the fluid (Brennen, 2013. Cavitation can be defined as the formation of vapour regions due to a decrease in local pressure. Undesirable consequences which can cause a fall in the performance of a system, structural failure, production of noise and vibration, material damage, are encountered due to cavitation (Uşar, 2015. In this study, cavitation was analysed using a bucket diagram. Bucket diagram represents the cavitation behaviour of a wing, fin or propeller blade in a two dimensional sense. This diagram is plotted as a function of section (hydrofoil angle of attack (α versus section cavitation number (σ. Pressure distribution can be calculated on two dimensional geometry of hydrofoil by using BEM (Boundary Element Method and cavitation bucket diagram can be computed. The cavitation inception case and partial cavitation cases have been investigated and the results of the present BEM were successfully compared with those of given in literature in the past and each other. While a constant source-dipole panel method has been used to calculate the pressure distribution at cavitation inception case, PCPAN programme that solves the sheet type of cavity on the hydrofoil by potential based panel method, has been used to calculate pressure distribution for the cases of partial cavitation. Effects of maximum hydrofoil thickness, maximum camber and location of maximum camber on cavitation have been analyzed by means of cavitation bucklet diagrams. All results are discussed in a detailed manner.

  6. Recent Results from Analysis of Flow Structures and Energy Modes Induced by Viscous Wave around a Surface-Piercing Cylinder

    Directory of Open Access Journals (Sweden)

    Giancarlo Alfonsi

    2017-01-01

    Full Text Available Due to its relevance in ocean engineering, the subject of the flow field generated by water waves around a vertical circular cylinder piercing the free surface has recently started to be considered by several research groups. In particular, we studied this problem starting from the velocity-potential framework, then the implementation of the numerical solution of the Euler equations in their velocity-pressure formulation, and finally the performance of the integration of the Navier-Stokes equations in primitive variables. We also developed and applied methods of extraction of the flow coherent structures and most energetic modes. In this work, we present some new results of our research directed, in particular, toward the clarification of the main nonintuitive character of the phenomenon of interaction between a wave and a surface-piercing cylinder, namely, the fact that the wave exerts its maximum force and exhibits its maximum run-up on the cylindrical obstacle at different instants. The understanding of this phenomenon becomes of crucial importance in the perspective of governing the entity of the wave run-up on the obstacle by means of wave-flow-control techniques.

  7. Cavitation in liquid cryogens. 2: Hydrofoil

    Science.gov (United States)

    Hord, J.

    1973-01-01

    Boundary layer principles, along with two-phase concepts, are used to improve existing correlative theory for developed cavity data. Details concerning cavity instrumentation, data analysis, correlative techniques, and experimental and theoretical aspects of a cavitating hydrofoil are given. Both desinent and thermodynamic data, using liquid hydrogen and liquid nitrogen, are reported. The thermodynamic data indicated that stable thermodynamic equilibrium exists throughout the vaporous cryogen cavities. The improved correlative formulas were used to evaluate these data. A new correlating parameter based on consideration of mass limiting two-phase flow flux across the cavity interface, is proposed. This correlating parameter appears attractive for future correlative and predictive applications. Agreement between theory and experiment is discussed, and directions for future analysis are suggested. The front half of the cavities, developed on the hydrofoil, may be considered as parabolically shaped.

  8. Some Remarks on the Three Dimensionality of Hydrofoil Cavitation

    Directory of Open Access Journals (Sweden)

    Mehmet Salih KARAALİOĞLU

    2017-12-01

    Full Text Available As it is well-known that cavitation is a very important physical phenomenon that affects significantly the performance of three-dimensional hydrofoils. Prediction of cavitation on three-dimensional hydrofoils is very important in the design stage. In this study, some approaches have been verified for hydrofoil cavitation. The main aim of this paper is to compare the mid-section pressure distribution of three-dimensional cavitating rectangular hydrofoil for increasing aspect ratios, with the pressure distribution of two-dimensional cavitating hydrofoil having the same section geometry as in the three-dimensional hydrofoil. In this study, a boundary element (panel method (BEM has been applied to investigate the hydrofoil cavitation for both two- and three-dimensional cases. Two-dimensional analytical solution in case of cavitating flat-plate has also been applied for comparison. It has been shown that the pressure distributions on the mid-section of three-dimensional cavitating and non-cavitating hydrofoil for increasing aspect ratios have converged to the solutions in two-dimensional case.

  9. Hydrofoil controls outfall effluents in rivers and oceans

    Science.gov (United States)

    Costen, R. C.

    1977-01-01

    System, which consists of vertical semispan hydrofoil anchored in water bed and set at angle of attack with respect to ambient water flow, works by keeping pollutants concentrated within long trailing vortex generated by hydrofoil and either deflecting vortex away from sensitive regions or sweeping it from side to side for rapid dispersion.

  10. Modified Composite Struts Would Damp Vibrations

    Science.gov (United States)

    Chen, Gun-Shing; Dolgin, Benjamin P.

    1993-01-01

    Composite-material (fiber/matrix laminate) struts damping longitudinal vibrations fabricated more easily in proposed new design. Prior design described in "Composite Struts Would Damp Vibrations" (NPO-17914). New design similar except pattern of fibers includes rounded bends (instead of sharp bends) in fibers.

  11. Null-strut calculus. II. Dynamics

    International Nuclear Information System (INIS)

    Kheyfets, A.; LaFave, N.J.; Miller, W.A.

    1990-01-01

    In this paper, we continue from the preceding paper to develop a fully functional Regge calculus geometrodynamic algorithm from the null-strut-calculus construction. The developments discussed include (a) the identification of the Regge calculus analogue of the constraint and evolution equations on the null-strut lattice, (b) a description of the Minkowski solid geometry for the simplicial blocks of the null-strut lattice, (c) a description of the evolution algorithm for the geometrodynamic scheme and an analysis of its consistency, and (d) a presentation of the dynamical degrees of freedom for a simplicial hypersurface and the description of an initial-value prescription. To demonstrate qualitatively this new approach to geometrodynamics, we present the most simple application of null-strut calculus that we know of---the Friedmann cosmology using the three-boundary of a 600-cell simplicial polytope to model the simplicial hypersurface

  12. Drop Hammer Tests with Three Oleo Strut Models and Three Different Shock Strut Oils at Low Temperatures

    Science.gov (United States)

    Kranz, M

    1954-01-01

    Drop hammer tests with different shock strut models and shock strut oils were performed at temperatures ranging to -40 C. The various shock strut models do not differ essentially regarding their springing and damping properties at low temperatures; however, the influence of the different shock strut oils on the springing properties at low temperatures varies greatly.

  13. Variable volume combustor with aerodynamic support struts

    Science.gov (United States)

    Ostebee, Heath Michael; Johnson, Thomas Edward; Stewart, Jason Thurman; Keener, Christopher Paul

    2017-03-07

    The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and providing the flow of fuel therethrough. The support struts may include an aerodynamic contoured shape so as to distribute evenly a flow of air to the micro-mixer fuel nozzles.

  14. Null-strut calculus. I. Kinematics

    International Nuclear Information System (INIS)

    Kheyfets, A.; LaFave, N.J.; Miller, W.A.

    1990-01-01

    This paper describes the kinematics of null-strut calculus---a 3+1 Regge calculus approach to general relativity. We show how to model the geometry of spacetime with simplicial spacelike three-geometries (TET's) linked to ''earlier'' and ''later'' momentumlike lattice surfaces (TET * ) entirely by light rays or ''null struts.'' These three-layered lattice spacetime geometries are defined and analyzed using combinatorial formulas for the structure of polytopes. The following paper in this series describes how these three-layered spacetime lattices are used to model spacetimes in full conformity with Einstein's theory of gravity

  15. Numerical Study on Characteristics of 3D Cavitating Hydrofoil

    Directory of Open Access Journals (Sweden)

    Cao Wei

    2015-01-01

    Full Text Available The commercial software ANSYS CFX, APDL and Workbench are applied for modeling the hydrodynamic and structural interactions and characteristics of an elastic hydrofoil by means of a two-way FSI method. The SST (Shear Stress Transport turbulence model and the simplified Rayleigh-Plesset equations are employed for the cavitating flow simulation. Both CFX and APDL solvers are set to be transient. The fluid and solid computational domains are sequentially solved to simulate the interactions between the hydrofoil and the cavitating flow. The results show that the difference in stiffness of common metal materials has trifling effects on hydrofoil performance. But variations in cavitation number and angle of attack will dramatically affect the hydrodynamic and structural interactions and characteristics.

  16. Flow Modelling for partially Cavitating Two-dimensional Hydrofoils

    DEFF Research Database (Denmark)

    Krishnaswamy, Paddy

    2001-01-01

    The present work addresses te computational analysis of partial sheet hydrofoil cavitation in two dimensions. Particular attention is given to the method of simulating the flow at the end of the cavity. A fixed-length partially cavitating panel method is used to predict the height of the re...... of the model and comparing the present calculations with numerical results. The flow around the partially cavitating hydrofoil with a re-entrant jet has also been treated with a viscous/inviscid interactive method. The viscous flow model is based on boundary layer theory applied on the compound foil......, consisting of the union of the cavity and the hydrofoil surface. The change in the flow direction in the cavity closure region is seen to have a slightly adverse effect on the viscous pressure distribution. Otherwise, it is seen that the viscous re-entrant jet solution compares favourably with experimental...

  17. Approximate hydrodynamic design of a finite span hydrofoil

    Science.gov (United States)

    Vladimirov, A N

    1955-01-01

    Previous work on the motion of various bodies under the surface of a heavy fluid is discussed. The solution of the motion of a flat plate by Keldysh and Lavrentiev is applied to the motion of a hydrofoil, making possible the presentation of charts for determining the lift and resistance of an infinite span hydrofoil operating in a heavy frictionless fluid having infinite depth below the free water surface. Consideration is given to the effects of viscosity and a method is suggested to correct for the finite span. The effect of the water surface on the downwash behind the foil is also discussed. A comparison of theoretical results obtained from this work with experimental data indicates that a basis for the approximate hydrodynamic design of a finite span hydrofoil has been achieved.

  18. The Flow Field on Hydrofoils with Leading Edge Protuberances

    Science.gov (United States)

    Custodio, Derrick; Henoch, Charles; Johari, Hamid

    2009-11-01

    The exceptional mobility of the humpback whale has been linked to the use of its unique pectoral flippers. Biologists speculate that the flippers leading edge protuberances are a form of passive flow control. Force measurements on 2D hydrofoils with spanwise uniform leading edge protuberances, resembling those seen on the humpback whale flipper, were taken in a water tunnel and have revealed performance modifications when compared to a baseline NACA 63(4)-021 hydrofoil model. Qualitative flow visualization techniques and Particle Image Velocimetry (PIV) flow field measurements on the modified hydrofoils have shown that streamwise vortices originating from the shoulders of the protuberances are the likely cause of performance changes. Varying levels of interaction among adjacent streamwise vortices have been observed as a function of angle of attack and chord location. The circulation of these vortices as a function of angle of attack and spatial location was measured and an analysis of the vortex interactions will be presented.

  19. Foil system fatigue load environments for commercial hydrofoil operation

    Science.gov (United States)

    Graves, D. L.

    1979-01-01

    The hydrofoil fatigue loads environment in the open sea is examined. The random nature of wave orbital velocities, periods and heights plus boat heading, speed and control system design are considered in the assessment of structural fatigue requirements. Major nonlinear load events such as hull slamming and foil unwetting are included in the fatigue environment. Full scale rough water load tests, field experience plus analytical loads work on the model 929 Jetfoil commercial hydrofoil are discussed. The problem of developing an overall sea environment for design is defined. State of the art analytical approaches are examined.

  20. Set-Based Approach to Design under Uncertainty and Applications to Shaping a Hydrofoil

    Science.gov (United States)

    2016-01-01

    Set-Based Approach to Design under Uncertainty and Applications to Shaping a Hydrofoil Johannes O. Royset∗ Professor Operations Research Department...viability through a shape design case of an efficient super-cavitating hydrofoil for ultra-high speed maritime vehicles. Redirecting the effort away...consider s-risk in a real design case consisting of a new family of dual-operating mode super-cavitating hydrofoils [14] devised to ensure high ef

  1. Numerical and experimental investigation of the unsteady flow field over a simplified hydrofoil plate

    OpenAIRE

    Pislevikj, Jasmina

    2017-01-01

    In this thesis, the behavior of a simplified hydrofoil in an unsteady water flow field is tested. Due to frequent load variations in high head Francis turbines, the runner vanes happen to break. Rotor stator interaction causes vibrations on the runner vanes. To simulate those vibrations in laboratory conditions, the hydrofoil, mounted in a cascade test rig, is excited with piezo electric patches. The experiment in this thesis shows the behavior of the hydrofoil in different water flow velocit...

  2. Optimal Shape for Forces and Moments on a Multi-Element Hydrofoil

    Science.gov (United States)

    2007-10-01

    Hydrofoil DISTRIBUTION: Approved for public release; distribution is unlimited. This paper is part of the following report: TITLE: International...Michigan, 5-8 August 2007 Optimal Shape for Forces and Moments on a Multi-Element Hydrofoil Yu-Tai Lee1, Vineet Ahuja 2, Ashvin Hosangadi 2 and Michael...forces and The Tab Assisted Control (TAC) foil used for moments acting on the hydrofoil with adequate underwater control surfaces, shown in Fig. la, was

  3. The influence of surface roughness on cloud cavitation flow around hydrofoils

    Science.gov (United States)

    Hao, Jiafeng; Zhang, Mindi; Huang, Xu

    2017-08-01

    The aim of this study is to investigate experimentally the effect of surface roughness on cloud cavitation around Clark-Y hydrofoils. High-speed video and particle image velocimetry (PIV) were used to obtain cavitation patterns images (Prog. Aerosp. Sci. 37: 551-581, 2001), as well as velocity and vorticity fields. Results are presented for cloud cavitating conditions around a Clark-Y hydrofoil fixed at angle of attack of α =8{°} for moderate Reynolds number of Re=5.6 × 105 . The results show that roughness had a great influence on the pattern, velocity and vorticity distribution of cloud cavitation. For cavitating flow around a smooth hydrofoil (A) and a rough hydrofoil (B), cloud cavitation occurred in the form of finger-like cavities and attached subulate cavities, respectively. The period of cloud cavitation around hydrofoil A was shorter than for hydrofoil B. Surface roughness had a great influence on the process of cloud cavitation. The development of cloud cavitation around hydrofoil A consisted of two stages: (1) Attached cavities developed along the surface to the trailing edge; (2) A reentrant jet developed, resulting in shedding and collapse of cluster bubbles or vortex structure. Meanwhile, its development for hydrofoil B included three stages: (1) Attached cavities developed along the surface to the trailing edge, with accumulation and rotation of bubbles at the trailing edge of the hydrofoil affecting the flow field; (2) Development of a reentrant jet resulted in the first shedding of cavities. Interaction and movement of flows from the pressure side and suction side brought liquid water from the pressure side to the suction side of the hydrofoil, finally forming a reentrant jet. The jet kept moving along the surface to the leading edge of the hydrofoil, resulting in large-scale shedding of cloud bubbles. Several vortices appeared and dissipated during the process; (3) Cavities grew and shed again.

  4. The influence of surface roughness on cloud cavitation flow around hydrofoils

    Science.gov (United States)

    Hao, Jiafeng; Zhang, Mindi; Huang, Xu

    2018-02-01

    The aim of this study is to investigate experimentally the effect of surface roughness on cloud cavitation around Clark-Y hydrofoils. High-speed video and particle image velocimetry (PIV) were used to obtain cavitation patterns images (Prog. Aerosp. Sci. 37: 551-581, 2001), as well as velocity and vorticity fields. Results are presented for cloud cavitating conditions around a Clark-Y hydrofoil fixed at angle of attack of α =8{°} for moderate Reynolds number of Re=5.6 × 105. The results show that roughness had a great influence on the pattern, velocity and vorticity distribution of cloud cavitation. For cavitating flow around a smooth hydrofoil (A) and a rough hydrofoil (B), cloud cavitation occurred in the form of finger-like cavities and attached subulate cavities, respectively. The period of cloud cavitation around hydrofoil A was shorter than for hydrofoil B. Surface roughness had a great influence on the process of cloud cavitation. The development of cloud cavitation around hydrofoil A consisted of two stages: (1) Attached cavities developed along the surface to the trailing edge; (2) A reentrant jet developed, resulting in shedding and collapse of cluster bubbles or vortex structure. Meanwhile, its development for hydrofoil B included three stages: (1) Attached cavities developed along the surface to the trailing edge, with accumulation and rotation of bubbles at the trailing edge of the hydrofoil affecting the flow field; (2) Development of a reentrant jet resulted in the first shedding of cavities. Interaction and movement of flows from the pressure side and suction side brought liquid water from the pressure side to the suction side of the hydrofoil, finally forming a reentrant jet. The jet kept moving along the surface to the leading edge of the hydrofoil, resulting in large-scale shedding of cloud bubbles. Several vortices appeared and dissipated during the process; (3) Cavities grew and shed again.

  5. Experimental and numerical analysis of cavitating flow around a hydrofoil

    Directory of Open Access Journals (Sweden)

    Müller Miloš

    2012-04-01

    Full Text Available The paper describes experiments carried out in the cavitation tunnel with the rectangular test section of 150 × 150 × 500 mm and the maximum test section inlet velocity of 25 m/s. These experiments have been aimed to visualize the cavitation phenomena as well as to quantify the erosion potential using pitting tests evaluated during the incubation period for the cast-iron prismatic hydrofoil with the modified NACA profile. A bypass section installed in the tunnel has allowed to measure the nuclei content in the inlet flow to the test section using the acoustic spectrometer. The measured data have been compared with the CFD analysis of the cavitation phenomena on the hydrofoil as well as the numerically determined location and magnitude of the first calculated collapses of the cavitating bubbles with a good agreement.

  6. Investigation of longitudinal control system for a small hydrofoil boat

    Science.gov (United States)

    Phillips, W. H.; Shaughnessy, J. D.

    1976-01-01

    An analysis of a hydromechanical system for longitudinal control of a small hydrofoil boat is presented. The system incorporates height and acceleration sensors operating flaps on the foils through a mechanical linkage. Effects of some of the system parameters on the stability and response to waves are shown. The results indicate that the system is capable of providing adequate stability, but the response to stern waves at low frequencies is larger than desired.

  7. Accidents of surface effect ships and hydrofoil craft

    Energy Technology Data Exchange (ETDEWEB)

    Korotkin, I.M.

    1981-01-01

    The work describes 200 accidents and disasters of hovercraft and hydrofoil craft of the United States, Great Britain, France, and other fleets which occurred in the 1960s and 1970s as a result of capsizing, storm damage, collisions, fires, explosions, etc. The causes of the accidents, the functioning of various craft systems, and the actions of the crews are examined. Recommendations on the prevention of such accidents are discussed.

  8. Vortex Simulation of the Bubbly Flow around a Hydrofoil

    Directory of Open Access Journals (Sweden)

    Tomomi Uchiyama

    2007-01-01

    Full Text Available This study is concerned with the two-dimensional simulation for an air-water bubbly flow around a hydrofoil. The vortex method, proposed by the authors for gas-liquid two-phase free turbulent flow in a prior paper, is applied for the simulation. The liquid vorticity field is discrerized by vortex elements, and the behavior of vortex element and the bubble motion are simultaneously computed by the Lagrangian approach. The effect of bubble motion on the liquid flow is taken into account through the change in the strength of vortex element. The bubbly flow around a hydrofoil of NACA4412 with a chord length 100 mm is simulated. The Reynolds number is 2.5×105, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. It is confirmed that the simulated distributions of air volume fraction and pressure agree well with the trend of the measurement and that the effect of angle of attack on the flow is favorably analyzed. These demonstrate that the vortex method is applicable to the bubbly flow analysis around a hydrofoil.

  9. Vortex trajectory and wake structure behind an energy harvesting hydrofoil

    Science.gov (United States)

    Lee, Walker; de Zordo-Banliat, Maximilien; Su, Yunxing; Miller, Michael; Breuer, Kenneth

    2017-11-01

    Detailed knowledge regarding the wake structure behind a pitching and heaving hydrofoil is important for optimizing multi-foil energy harvesting systems. Here we report on measurements of the large vortices shed from the hydrofoil. An acoustic Doppler velocimeter is positioned in a water flume, downstream of a flapping hydrofoil (chord, c = 10 cm) and traversed across the wake, measuring three components of velocity at 25 Hz over at least 20 cycles. The phase-averaged velocities are used to identify the primary vortex structures and to assess their trajectory, intensity and coherence as functions of frequency, f, pitching amplitude, θ, and Reynolds number, Re . Different methods for identifying the vortex structures are developed and their utility and weakness are compared. It is found that the transverse distance between the shed vortices (i.e. the width of the wake) decreases as the reduced frequency (fc / U) rises, but is not sensitive to the pitching amplitude. The time at which a vortex arrives at a fixed downstream position is affected by both the time at the vortex separates from the foil and the vortex convection speed in the wake. These two quantities are assessed as functions of pitch amplitude, reduced frequency and Reynolds number. This work is funded by ARPA-e.

  10. Design of Bi-Directional Hydrofoils for Tidal Current Turbines

    Science.gov (United States)

    Nedyalkov, Ivaylo; Wosnik, Martin

    2015-11-01

    Tidal Current Turbines operate in flows which reverse direction. Bi-directional hydrofoils have rotational symmetry and allow such turbines to operate without the need for pitch or yaw control, decreasing the initial and maintenance costs. A numerical test-bed was developed to automate the simulations of hydrofoils in OpenFOAM and was utilized to simulate the flow over eleven classes of hydrofoils comprising a total of 700 foil shapes at different angles of attack. For promising candidate foil shapes physical models of 75 mm chord and 150 mm span were fabricated and tested in the University of New Hampshire High-Speed Cavitation Tunnel (HiCaT). The experimental results were compared to the simulations for model validation. The numerical test-bed successfully generated simulations for a wide range of foil shapes, although, as expected, the k - ω - SST turbulence model employed here was not adequate for some of the foils and for large angles of attack at which separation occurred. An optimization algorithm is currently being coupled with the numerical test-bed and additional turbulence models will be implemented in the future.

  11. A numerical parametric study on hydrofoil interaction in tandem

    Directory of Open Access Journals (Sweden)

    Omer Kemal Kinaci

    2015-01-01

    Full Text Available Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Method (BEM and RANSE. BEM allows a quick estimation of the flow around bodies and may be used for practical purposes to assess the interaction inside the fluid. The produced results are verified by conformal mapping and Finite Volume Method (FVM. RANSE is used for viscous flow conditions to assess the effects of viscosity compared to the inviscid solutions proposed by BEM. Six different parameters are investigated and they are the effects of distance, thickness, angle of attack, chord length, aspect ratio and tapered wings. A generalized 2-D code is developed implementing the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid.

  12. Hydrofoil near-wake sound sources at high Reynolds number

    Science.gov (United States)

    Bourgoyne, Dwayne A.; Hamel, Joshua M.; Judge, Carolyn Q.; Ceccio, Steve L.; Dowling, David R.

    2002-05-01

    An important hydroacoustic noise source from a fully submerged noncavitating hydrofoil is often the unsteady separated turbulent flow near its trailing edge. Here, hydroacoustic noise may be produced by boundary layer turbulence swept past and scattered from the foils trailing edge, and by coherent vortices formed in the foils near-wake. Such vortices may generate an energetic tonal component that rises above the broadband trailing-edge hydroacoustic noise. This presentation describes results of an experimental effort to identify and measure vortical flow features in the near-wake of a two-dimensional hydrofoil at chord-based Reynolds numbers ranging from 0.5 to 60 million. The experiments were conducted at the U.S. Navy's William B. Morgan Large Cavitation Channel with a test-section-spanning hydrofoil (2.1 m chord, 3.0 m span) at flow speeds from 0.25 to 18.3 m/s. Two trailing-edge shapes were investigated, and foil-internal accelerometers were used to monitor structural vibration. Velocity fluctuation spectra were measured in the foils near-wake with a two-component LDV system, and dynamic surface pressures were measured near the foils trailing edge with flush-mounted transducer arrays. Both indicate Reynolds number and trailing-edge shape-dependent vortex shedding. [Significant assistance provided by personnel from NSWC-CD. Work sponsored by Code 333 of ONR.

  13. In-line holography for flow and cavitation visualization on hydrofoils and for nuclei measurements

    NARCIS (Netherlands)

    Renesse, R.L. van; Meulen, J.H.J. van der

    1980-01-01

    The boundary layer flow about two hydrofoils and the appearance of cavitation are investigated by means of in-line holography. Practical details on the hologram resolution and data collection time for nuclei size analysis are given. It is shown that the appearance of cavitation on the hydrofoils is

  14. Numerical Analysis of Combustion around a Strut in Supersonic Airflow

    Science.gov (United States)

    Minato, Ryojiro; Ju, Yiguang; Niioka, Takashi

    Numerical simulation of combustion around a strut in supersonic airflow at Mach 1.5 was conducted. In previous papers, experimental results on flame-holding characteristics have been shown for the strut divided into two parts, indicating the effectiveness of the flame-holding characteristics of this strut. Stable flame-holding is due to a comparatively long residence time in the subsonic flow region between the two parts of the strut. The present study is analytical evidence of the stable flame-holding of this strut. The Stahl and Warnatz’s detailed chemistry of hydrogen/oxygen reactions and the Baldwin Lomax turbulence algebraic model were employed to simulate the chemical reaction and turbulent flow, respectively. Flame structures such as distributions of chemical species and temperature were obtained. For example, the predicted density distributions explicitly showed an attached shock wave, expansion fans and shear layers, and had good agreement with the shadowgraph of the experiment. The overall equivalence ratio in the space between two strut parts was calculated to evaluate the reaction time in the space between the struts and a particle trace analysis was performed to evaluate the residence time in the space. By obtaining the Damköhler number from two characteristic times, two flame-holding limits, namely the chemical kinetic limit at small interval between two struts and the dynamic limit at large interval, were discussed. The numerical results were qualitatively consistent with the previous experimental results.

  15. Optimization of hydrofoil for tidal current turbine based on particle swarm optimization and computational fluid dynamic method

    Directory of Open Access Journals (Sweden)

    Zhang De-Sheng

    2016-01-01

    Full Text Available Both efficiency and cavitation performance of the hydrofoil are the key technologies to design the tidal current turbine. In this paper, the hydrofoil efficiency and lift coefficient were improved based on particle swarm optimization method and XFoil codes. The cavitation performance of the optimized hydrofoil was also discussed by the computational fluid dynamic. Numerical results show the efficiency of the optimized hydrofoil was improved 11% ranging from the attack angle of 0-7° compared to the original NACA63-818 hydrofoil. The minimum pressure on leading edge of the optimized hydrofoil dropped above 15% at the high attack angle conditions of 10°, 15°, and 20°, respectively, which is benefit for the hydrofoil to avoiding the cavitation.

  16. Preparation of experimental and numerical research on unsteady cavitating flow around hydrofoil

    Science.gov (United States)

    Komárek, Martin; Sedlář, Milan; Vyroubal, Michal; Zima, Patrik; Müller, Miloš; Pálka, Tomáš

    2015-05-01

    This paper describes the preparation of the experimental setup and the results of the CFD analysis for the investigation of the unsteady cavitating flow around a prismatic NACA 2412 hydrofoil at different flow conditions. The experimental research is carried out in the cavitation water tunnel located in the Centre of Hydraulic Research in Lutín. The tunnel is integrated into the closed horizontal loop of the hydraulic test rig. The transparent test section provides a full view of the flow around the hydrofoil. The hydrofoil incidence angle is fully adjustable. Two variants of hydrofoil of the same geometry have been designed. One variant is equipped with pressure tap holes for the measurement of the static pressure, and the other variant is covered with a grid of five PVDF films, fully integrated in the hydrofoil. The PVDF films enable to measure the impact forces exerted on the hydrofoil surface by the collapsing cavitation structures. The high-frequency pressure oscillations downstream of the hydrofoil trailing edge are measured using the PVDF hydrophone. The cavitating flow is visualized using two simultaneously operating high-speed cameras providing the top and side views of the flow. A preliminary CFD analysis using the ANSYS CFX package helped to determine the flow regimes for the experimental study. The obtained CFD results agree well with the preliminary measurements.

  17. Preparation of experimental and numerical research on unsteady cavitating flow around hydrofoil

    Directory of Open Access Journals (Sweden)

    Komárek Martin

    2015-01-01

    Full Text Available This paper describes the preparation of the experimental setup and the results of the CFD analysis for the investigation of the unsteady cavitating flow around a prismatic NACA 2412 hydrofoil at different flow conditions. The experimental research is carried out in the cavitation water tunnel located in the Centre of Hydraulic Research in Lutín. The tunnel is integrated into the closed horizontal loop of the hydraulic test rig. The transparent test section provides a full view of the flow around the hydrofoil. The hydrofoil incidence angle is fully adjustable. Two variants of hydrofoil of the same geometry have been designed. One variant is equipped with pressure tap holes for the measurement of the static pressure, and the other variant is covered with a grid of five PVDF films, fully integrated in the hydrofoil. The PVDF films enable to measure the impact forces exerted on the hydrofoil surface by the collapsing cavitation structures. The high-frequency pressure oscillations downstream of the hydrofoil trailing edge are measured using the PVDF hydrophone. The cavitating flow is visualized using two simultaneously operating high-speed cameras providing the top and side views of the flow. A preliminary CFD analysis using the ANSYS CFX package helped to determine the flow regimes for the experimental study. The obtained CFD results agree well with the preliminary measurements.

  18. Optimization of the hydrofoil cascade and validation with quasi-analytical solution for hydraulic machinery

    Energy Technology Data Exchange (ETDEWEB)

    Frunza, T; Susan-Resiga, R [Department of Hydraulic Machinery, ' Politehnica' University of Timisoara Bv. Mihai Viteazu 1, RO-300222, Timisoara (Romania); Muntean, S; Bernad, S, E-mail: tfrunza@yahoo.co [Centre of Advanced Research in Engineering Sciences, Romanian Academy - Timisoara Branch, Bv. Mihai Viteazu 24, RO-300223, Timisoara (Romania)

    2010-08-15

    The paper presents the authors ongoing efforts to develop a robust and efficient numerical methodology, and the associated expert software, for analysis, design and optimization of hydrofoil cascades. We developed, so far, a Finite Element solver with streamfunction formulation for incompressible, inviscid and irrotational cascade flow, using a modern software infrastructure, and efficient implementation. Two test cases will be presented to evaluate the accuracy of our CASCADExpert code. In the first case, our code is tested for a thin hydrofoil cascade designed with the quasi-analytical approach. Second, the blade loading and thickness distributions obtain with our code from a given hydrofoil shape are used in an inverse design method. As a result, an optimized hydrofoil cascade is obtained. The pressure distribution on the original and optimized hydrofoil cascades is compared. We have applied the method in order to optimize the turbine and pump hydrofoil cascades, respectively. Consequently, a new method is developed in order to generate the optimized hydrofoil cascade geometry for hydraulic machinery.

  19. Strut Deformation in CFRP-Strengthened Reinforced Concrete Deep Beams

    Directory of Open Access Journals (Sweden)

    Mohammad Panjehpour

    2014-01-01

    Full Text Available Strut-and-tie model (STM method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions. It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level.

  20. Strut deformation in CFRP-strengthened reinforced concrete deep beams.

    Science.gov (United States)

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2014-01-01

    Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level.

  1. Fluid-Structure Interaction Analysis of Hydrofoils in a Pulsating Flow

    Directory of Open Access Journals (Sweden)

    Li Jiasheng

    2016-01-01

    Full Text Available The reduction of noise and vibration are very important in the design of hydrofoils. The current study focuses on establishing a theoretical and numerical model to investigate fluid-structure interaction caused by elastic hydrofoils in a pulsating flow. A fully coupled three dimensional boundary element method (BEM and finite element method (FEM code is applied to analyze the hydrodynamic performance. The numerical results show that the peak frequencies of the support reactions are related to the natural frequency of the hydrofoil. The natural frequencies and support reaction amplitudes are reduced significantly by including the fluid-structure coupling.

  2. Dynamic Schooling of a Tandem Pair of Heaving Hydrofoils

    Science.gov (United States)

    Newbolt, Joel; Ristroph, Leif; Zhang, Jun

    2016-11-01

    The reverse von Kármán wake generated by a heaving hydrofoil has recently been shown to provide stable positions to a second hydrofoil heaving in the wake (Ramananarivo et al. at NYU). Because a similar wake structure is seen for many swimming and flying animals this fluid-mediated interaction is suspected to play a role in schooling and flocking. A newly designed experimental apparatus allows us to study this interaction in the case where the two foils are powered independently so that each foil may take on a different flapping amplitude, phase and frequency. Measurements show that the stable positions of the following foil can be shifted to any arbitrary downstream position by varying only the relative flapping phase between the foils. At different relative frequencies and amplitudes the following foil exhibits several distinct trajectories. When the following foil has a lower frequency and higher amplitude than the leader the spacing between the foils can undergo a periodic trajectory. When driven at a common frequency the follower occupies stable positions in the wake of the leader. When the follower has a higher frequency the spacing between the foils is unstable, either increasing or decreasing in time, depending on the relative amplitudes and initial conditions.

  3. New approaches to the design optimization of hydrofoils

    Science.gov (United States)

    Beyhaghi, Pooriya; Meneghello, Gianluca; Bewley, Thomas

    2015-11-01

    Two simulation-based approaches are developed to optimize the design of hydrofoils for foiling catamarans, with the objective of maximizing efficiency (lift/drag). In the first, a simple hydrofoil model based on the vortex-lattice method is coupled with a hybrid global and local optimization algorithm that combines our Delaunay-based optimization algorithm with a Generalized Pattern Search. This optimization procedure is compared with the classical Newton-based optimization method. The accuracy of the vortex-lattice simulation of the optimized design is compared with a more accurate and computationally expensive LES-based simulation. In the second approach, the (expensive) LES model of the flow is used directly during the optimization. A modified Delaunay-based optimization algorithm is used to maximize the efficiency of the optimization, which measures a finite-time averaged approximation of the infinite-time averaged value of an ergodic and stationary process. Since the optimization algorithm takes into account the uncertainty of the finite-time averaged approximation of the infinite-time averaged statistic of interest, the total computational time of the optimization algorithm is significantly reduced. Results from the two different approaches are compared.

  4. Numerical Modeling of Unsteady Cavitating Flows around a Stationary Hydrofoil

    Directory of Open Access Journals (Sweden)

    Antoine Ducoin

    2012-01-01

    Full Text Available The objective of this paper is to evaluate the predictive capability of three popular transport equation-based cavitation models for the simulations of partial sheet cavitation and unsteady sheet/cloud cavitating flows around a stationary NACA66 hydrofoil. The 2D calculations are performed by solving the Reynolds-averaged Navier-Stokes equation using the CFD solver CFX with the k-ω SST turbulence model. The local compressibility effect is considered using a local density correction for the turbulent eddy viscosity. The calculations are validated with experiments conducted in a cavitation tunnel at the French Naval Academy. The hydrofoil has a fixed angle of attack of α=6° with a Reynolds number of Re = 750,000 at different cavitation numbers σ. Without the density modification, over-prediction of the turbulent viscosity near the cavity closure reduces the cavity length and modifies the cavity shedding characteristics. The results show that it is important to capture both the mean and fluctuating values of the hydrodynamic coefficients because (1 the high amplitude of the fluctuations is critical to capturing the extremes of the loads to ensure structural safety and (2 the need to capture the frequency of the fluctuations, to avoid unwanted noise, vibrations, and accelerated fatigue issues.

  5. Numerical investigation of time-dependent cloud cavitating flow around a hydrofoil

    Directory of Open Access Journals (Sweden)

    Zhang De-Sheng

    2016-01-01

    Full Text Available Time-dependent cloud cavitation around the 2-D Clark-Y hydrofoil was investigated in this paper based on an improved filter based model and a density correction method. The filter-scale in filter based model simulation was discussed and validated according to the grid size. Numerical results show that in the transition from sheet cavitation to cloud cavitation, the sheet cavity grows slowly to the maximum length during the re-entrant jet develops. The mild shedding bubble cluster convects downwards the hydrofoil and continues to grow up after detaching from the suction surface of hydrofoil, and a bubble cluster introduced at the rear part of hydrofoil. While the sheet cavity generates, the bubble cluster breakups.

  6. Marine Mammals as Models for Cost Efficient AUVs: Specifications of Oscillating Hydrofoils

    National Research Council Canada - National Science Library

    Williams, Terrie

    2004-01-01

    ...), California sea lions (Zalophus californianus), river otters (Lontra canadensis), and sea otters (Enhydra lutris) to assess the mechanical operation and energetic cost of oscillating hydrofoils performing in controlled environments...

  7. On the Changes in Lift of Hydrofoils Due to Surface Injections of Polymer Additives

    Science.gov (United States)

    1978-02-01

    no aIn thom ease of 0.l vox ’-trtd ing theo 110e- ativo I’votttro -paks . Also, thet~o eu dCt’tt.!o iva fe e on tlke t’oil’ .n e 00 I’蜳 ý .0k4 01...hydrofoil chord, c.. In -Equation 133 tho .posoitivo -ig applies to tho uipper surface ou, the hydrofoil Wh11i tho.1wk~ ativo pitgn applies to tho lower

  8. Detached eddy simulation of unsteady cavitation and pressure fluctuation around 3-D NACA66 hydrofoil

    Directory of Open Access Journals (Sweden)

    Zhang De-Sheng

    2015-01-01

    Full Text Available The unsteady cavitating flow and pressure fluctuation around the 3-D NACA66 hydrofoil were simulated and validated based on detached eddy simulation turbulence model and a homogeneous cavitation model. Numerical results show that detached eddy simulation can predict the evolution of cavity inception, sheet cavitation growth, cloud cavitation shedding, and breakup, as well as the pressure fluctuation on the surface of hydrofoil. The sheet cavitation growth, detachment, cloud cavitation shedding are responsible for the features of the pressure fluctuation.

  9. High-speed hydrofoils for the Russian Far East basin (review)

    OpenAIRE

    KONSTANTIN GRIBOV; GENNADIY FEDOREEV

    2017-01-01

    Abstract: In Russia, first in the world, there were made and came into wide practical use boats using hydrofoil technology, that is equipped with the wing that enables them to raise their hull out of the water: those are hydrofoils and ekranoplans. The boats of both types share the same principle of movement: the hull being raised out of the water greatly reduces hull dag, which correspondingly provides a considerable increase in speed. Sea conditions, however, add problems with ensuring thei...

  10. Design and implementation of a biomimetic turtle hydrofoil for an autonomous underwater vehicle.

    Science.gov (United States)

    Font, Davinia; Tresanchez, Marcel; Siegentahler, Cedric; Pallejà, Tomàs; Teixidó, Mercè; Pradalier, Cedric; Palacin, Jordi

    2011-01-01

    This paper presents the design and implementation of a turtle hydrofoil for an Autonomous Underwater Vehicle (AUV). The final design of the AUV must have navigation performance like a turtle, which has also been the biomimetic inspiration for the design of the hydrofoil and propulsion system. The hydrofoil design is based on a National Advisory Committee for Aeronautics (NACA) 0014 hydrodynamic profile. During the design stage, four different propulsion systems were compared in terms of propulsion path, compactness, sealing and required power. The final implementation is based on a ball-and-socket mechanism because it is very compact and provides three degrees of freedom (DoF) to the hydrofoil with very few restrictions on the propulsion path. The propulsion obtained with the final implementation of the hydrofoil has been empirically evaluated in a water channel comparing different motion strategies. The results obtained have confirmed that the proposed turtle hydrofoil controlled with a mechanism with three DoF generates can be used in the future implementation of the planned AUV.

  11. Design and Implementation of a Biomimetic Turtle Hydrofoil for an Autonomous Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Jordi Palacin

    2011-11-01

    Full Text Available This paper presents the design and implementation of a turtle hydrofoil for an Autonomous Underwater Vehicle (AUV. The final design of the AUV must have navigation performance like a turtle, which has also been the biomimetic inspiration for the design of the hydrofoil and propulsion system. The hydrofoil design is based on a National Advisory Committee for Aeronautics (NACA 0014 hydrodynamic profile. During the design stage, four different propulsion systems were compared in terms of propulsion path, compactness, sealing and required power. The final implementation is based on a ball-and-socket mechanism because it is very compact and provides three degrees of freedom (DoF to the hydrofoil with very few restrictions on the propulsion path. The propulsion obtained with the final implementation of the hydrofoil has been empirically evaluated in a water channel comparing different motion strategies. The results obtained have confirmed that the proposed turtle hydrofoil controlled with a mechanism with three DoF generates can be used in the future implementation of the planned AUV.

  12. The Performance of Finite-span Hydrofoils with Humpback Whale-like Leading Edge Protuberances

    Science.gov (United States)

    Custodio, Derrick; Henoch, Charles; Johari, Hamid

    2010-11-01

    The effects of leading edge protuberances on the lift and drag performance of finite-span hydrofoils were examined in a series of water tunnel experiments. The leading edge protuberances are analogous to the tubercles on humpback whale pectoral flippers. The hydrofoils have a rectangular planform and an aspect ratio of 4. The hydrofoil section profile is based on NACA 63(4)-021, and the leading edge has a sinusoidal geometry with constant amplitude and wavelength. The hydrofoil angle of attack was varied up to 30 , and the freestream velocity ranged from 1.8 to 5.4 m/s. Results indicate that the hydrofoils with leading edge protuberances do not stall in the traditional manner. Below 12 lift increased linearly with angle of attack. Beyond this angle, the lift either attained a nearly constant value or increased slowly up to 30 depending on the Reynolds number. Drag increased continuously with the angle of attack, and was not dependent on the Reynolds number. These observations are consistent with our previous infinite span hydrofoil data, and may be explained in terms of the flow modifications created by the leading edge protuberances.

  13. Strut analysis for osteoporosis detection model using dental panoramic radiography.

    Science.gov (United States)

    Hwang, Jae Joon; Lee, Jeong-Hee; Han, Sang-Sun; Kim, Young Hyun; Jeong, Ho-Gul; Choi, Yoon Jeong; Park, Wonse

    2017-10-01

    The aim of this study was to identify variables that can be used for osteoporosis detection using strut analysis, fractal dimension (FD) and the gray level co-occurrence matrix (GLCM) using multiple regions of interest and to develop an osteoporosis detection model based on panoramic radiography. A total of 454 panoramic radiographs from oral examinations in our dental hospital from 2012 to 2015 were randomly selected, equally distributed among osteoporotic and non-osteoporotic patients (n = 227 in each group). The radiographs were classified by bone mineral density (T-score). After 3 marrow regions and the endosteal margin area were selected, strut features, FD and GLCM were analysed using a customized image processing program. Image upsampling was used to obtain the optimal binarization for calculating strut features and FD. The independent-samples t-test was used to assess statistical differences between the 2 groups. A decision tree and support vector machine were used to create and verify an osteoporosis detection model. The endosteal margin area showed statistically significant differences in FD, GLCM and strut variables between the osteoporotic and non-osteoporotic patients, whereas the medullary portions showed few distinguishing features. The sensitivity, specificity, and accuracy of the strut variables in the endosteal margin area were 97.1%, 95.7 and 96.25 using the decision tree and 97.2%, 97.1 and 96.9% using support vector machine, and these were the best results obtained among the 3 methods. Strut variables with FD and/or GLCM did not increase the diagnostic accuracy. The analysis of strut features in the endosteal margin area showed potential for the development of an osteoporosis detection model based on panoramic radiography.

  14. Optimal Design and Numerical Simulation on Fish-Like Flexible Hydrofoil Propeller

    Directory of Open Access Journals (Sweden)

    Xue Gang

    2016-12-01

    Full Text Available Hydrofoil is widely used in underwater vehicle for the excellent hydrodynamic characteristics. Currently, researches are mostly about the rigid hydrofoil while the flexible hydrofoil, like the caudal fin, has not been studied adequately. In this paper, the fish was regarded as the bionic object. Then the kinematics model to describe the fish swimming was put forward. A fin-peduncle propulsion mechanism was designed based on the kinematics model to achieve the similar sine curve swimming model. The propulsion mechanism was optimized by Matlab to reduce the deviation between the output curve of the fin-peduncle propulsion mechanism and the ideal motion trajectory. Moreover, the motion phase angles among flexible articulations are optimized to reduce fluid resistance and improve propulsive efficiency. Finally, the fish-like hydrofoil oscillation is simulated by fluid-solid coupling method based on the Fluent. It was shown that the optimized flexible fish-like oscillation could generate the motion that follows the similar law of sine. The propulsive efficiency of oscillating hydrofoil propeller is much higher than that of the screw propeller, and the flexible oscillation has higher propulsive efficiency than the rigid oscillation without obvious fluid resistance increase.

  15. Aerodynamic Theory and Tests of Strut Forms-II

    Science.gov (United States)

    Smith, R H

    1930-01-01

    This report presents the second of two studies under the same title. In this part five theoretical struts are developed from distributed sources and sinks and constructed for pressure and resistance tests in a wind tunnel. The surface pressures for symmetrical inviscid flow are computed for each strut from theory and compared with those found by experiment. The theoretical and experimental pressures are found to agree quantitatively near the bow, only qualitatively over the suction range, the experimental suctions being uniformly a little low, and not at all near the stern. This study is the strut sequel to Fuhrmann's research on airship forms, the one being a study in two dimensions, the other in three. A comparison of results indicates that the agreement between theory and experiment is somewhat better for bodies of revolution than for cylinders when both are shaped for slight resistance. The consistent deficiency of the experimental suctions which is found in the case of struts was not found in the case of airships, for which the experimental suctions were sometimes above sometimes below their theoretical values.

  16. Long range node-strut analysis of trabecular bone microarchitecture

    DEFF Research Database (Denmark)

    Schmah, Tanya; Marwan, Norbert; Thomsen, Jesper Skovhus

    2011-01-01

    PURPOSE: We present a new morphometric measure of trabecular bone microarchitecture, called mean node strength (NdStr), which is part of a newly developed approach called long range node-strut analysis. Our general aim is to describe and quantify the apparent "latticelike" microarchitecture of th...

  17. 78 FR 73997 - Airworthiness Directives; Various Aircraft Equipped with Wing Lift Struts

    Science.gov (United States)

    2013-12-10

    ... to promote drilling holes into or otherwise unsealing a sealed strut. This AD retains all the actions... numbers) that were manufactured with rolled threads. Wing lift strut forks manufactured with machine (cut... Requirements for Ultrasonic Inspection of Piper Wing Lift Struts Equipment Requirements 1. A portable...

  18. 78 FR 3356 - Airworthiness Directives; Various Aircraft Equipped With Wing Lift Struts

    Science.gov (United States)

    2013-01-16

    ...) of this AD, inspect the wing lift strut forks for cracks using magnetic particle procedures, such as... Airworthiness Directives; Various Aircraft Equipped With Wing Lift Struts AGENCY: Federal Aviation... existing airworthiness directive (AD) that applies to certain aircraft equipped with wing lift struts. The...

  19. The numerical study of the cavitation-structure interaction around 3D flexible hydrofoil

    Science.gov (United States)

    Shi-liang, Hu; Ying, Chen; Chuan-jing, Lu

    2015-12-01

    The closely coupled approach combined the Finite Volume Method (FVM) solver and the Finite Element Method (FEM) solver is applied to simulation the cavitation-structure interaction of a 3D cantilevered flexible hydrofoil in water tunnel. In the cavitating flow, the elastic hydrofoil would deform or vibrate in bending and twisting mode. And the motion of the foil would affect the characteristics of the cavity and the hydrodynamic load on the foil in turn. With smaller cavitation numbers (σv=2.15), the frequency spectrum of the lift on the foil would contain two frequencies which are associated to the cavity shedding and the first bend frequency of the hydrofoil. With larger cavitation number (σv=2.55), the frequency of the lift is completely dominated by the natural frequency of the foil.

  20. Prediction and analysis of 3D hydrofoil and propeller under potential flow using panel method

    Directory of Open Access Journals (Sweden)

    Chen Chen-Wei

    2016-01-01

    Full Text Available Potential flow over an airfoil plays an important historical role in the theory of airfoil. The governing equation for potential flow is Laplace’s equation. One of Green’s identities can be used to write a solution to Laplace’s equation as a boundary integral. Using distributions of singularity solutions and determining their strength via the boundary conditions is the essence of panel method. This paper introduces a quick prediction method of three-dimensional hydrofoil and propeller performance based on panel method. The surface of hydrofoil and propeller is divided into numbers of quadrilateral panels. Combined sources with doublets singularities will be distributed on the corners of panels. Calculated blade pressure distributions of hydrofoil and propeller agree well with experimental data. Several sample calculations have been included using panel method.

  1. Effects of Boundary Layer Control Method on Hydrodynamic Characteristics and Tip Vortex Creation of a Hydrofoil

    Directory of Open Access Journals (Sweden)

    Ghadimi Parviz

    2017-06-01

    Full Text Available There is currently a significant focus on using boundary layer control (BLC approach for controlling the flow around bodies, especially the foil sections. In marine engineering this is done with the hope of increasing the lift - to - drag ratio and efficiency of the hydrofoils. In this paper, effects of the method on hydrodynamic characteristics and tip vortex formation of a hydrofoil are studied. Steady water injection at the tip of the hydrofoil is simulated in different conditions by using ANSYS-CFX commercial software. Validity of the proposed simulations is verified by comparing the obtained results against available experimental data. Effects of the injection on the lift, drag, and lift - to - drag ratio are studied and the ranges within which the injection has the most positive or negative effects, are determined. Furthermore, flow pattern and pressure variation are studied upon the water injection to determine the most positive and negative case and to ascertain the main reasons triggering these phenomena.

  2. Numerical research on unsteady cavitating flow over a hydrofoil

    Science.gov (United States)

    Homa, D.; Wróblewski, W.

    2016-10-01

    Cavitation is a widely known phenomenon in pumps and water turbines installations. It can lead to significant damage of blades and walls of the rotor therefore it is crucial during pump designing and exploitation to avoid working in flow conditions, that enabled cavitation to occur. Nowadays numerical simulations of flow can provide valuable information concerning pressure and velocity distribution and can indicate if there is a risk of cavitating flow appearance. There are a few mathematical models which describe cavitating flow. In the paper Schnerr & Sauer model was chosen for simulation. Aim of the paper is to verify its utility in case of different cavitating flow regimes over Clark-Y hydrofoil. After performing the grid independence study four different cavitation regimes were investigated. The vapour areas appearance, their shapes and changes in time were observed. The assumption of isothermal, two - phase flow was made. The calculations were performed using OpenFOAM and were compared to the available measurements data. The presented results concerned sheet and cloud cavitation regimes.

  3. Experimental and numerical FSI study of compliant hydrofoils

    Science.gov (United States)

    Augier, B.; Yan, J.; Korobenko, A.; Czarnowski, J.; Ketterman, G.; Bazilevs, Y.

    2015-06-01

    A propulsion system based on tandem hydrofoils is studied experimentally and numerically. An experimental measurement system is developed to extract hydrodynamic loads on the foils and capture their twisting deformation during operation. The measured data allowed us to assess the efficiency of the propulsion system as a function of travel speed and stroke frequency. The numerical simulation of the propulsion system is also presented and involves 3D, full-scale fluid-structure interaction (FSI) computation of a single (forward) foil. The foil is modeled as a combination of the isogeometric rotation-free Kirchhoff-Love shell and bending-stabilized cable, while the hydrodynamics makes use of the finite-element-based arbitrary Lagrangian-Eulerian variational multiscale formulation. The large added mass is handled through a quasi-direct FSI coupling technique. The measurement data collected is used in the validation of the FSI simulation, and excellent agreement is achieved between the predicted and measured hydrodynamic loads and foil twisting motion.

  4. Computational simulation of multi-strut central lobed injection of hydrogen in a scramjet combustor

    Directory of Open Access Journals (Sweden)

    Gautam Choubey

    2016-09-01

    Full Text Available Multi-strut injection is an approach to increase the overall performance of Scramjet while reducing the risk of thermal choking in a supersonic combustor. Hence computational simulation of Scramjet combustor at Mach 2.5 through multiple central lobed struts (three struts have been presented and discussed in the present research article. The geometry and model used here is slight modification of the DLR (German Aerospace Center scramjet model. Present results show that the presence of three struts injector improves the performance of scramjet combustor as compared to single strut injector. The combustion efficiency is also found to be highest in case of three strut fuel injection system. In order to validate the results, the numerical data for single strut injection is compared with experimental result which is taken from the literature.

  5. Improved Hypersonic Inlet Performance Using Validated Strut Compression Designs

    Science.gov (United States)

    Bulman, M. J.; Stout, P. W.; Fernandez, R.

    1997-01-01

    Aerojet is currently executing two Strutjet propulsion contracts: one a Rocket Based Combined Cycle (RBCC) engine for a NASA-Marshall Space Flight Center (MSFC) Advanced Reusable Transportation Technology (ARTT) program, the second a Dual Mode Ram/Scramjet engine for a USAF Wright Laboratories Storable Fuel Scramjet Flow Path Concepts program. The engines employed in both programs operate at supersonic and low hypersonic speeds and use inlets employing forebody external and sidewall compression. Aerojet has developed and validated a successful design methodology applicable to these inlet types. Design features include an integrated vehicle forebody, external side compression struts, strut sidewall and throat bleed, a throat shock trap, and variable geometry internal contraction. Computation Fluid Dynamic (CFD) predictions and test data show these inlets allow substantially increased flow turning angles over other designs. These increased flow turning angles allow shorter and lighter engines than current designs, which in turn enables higher performing vehicles with broad operating characteristics. This paper describes the designs of two different inlets evaluated by the NASA-MSFC and USAF programs, discusses the results of wind tunnel tests performed by NASA-Lewis Research Center, and provides correlations of test data with CFD predictions. Parameters of interest include low Mach number starting capability, start sensitivity as a function of back pressure at various contraction ratios, flow turning angles, strut and throat bleed effects, and pressure recovery at various Mach numbers.

  6. Repellence Effect of the New Sound for Underwater Speaker of Hydrofoil

    Directory of Open Access Journals (Sweden)

    Tatsunori Nakashima

    2015-06-01

    Full Text Available In order to prevent hydrofoil colliding with cetaceans, the underwater speaker (UWS has been installed to repel cetaceans. Yamada et al. (2012 analyzed and devised the UWS sound as it fits the cetaceans' acoustic properties to prevent the collision furthermore. The new UWS sound was devised and synthesized by Yamada et al. (2015 with expectation of avoiding collision with large cetaceans (Patent applied for, JP2014-171411. In this research project, the new UWS sound was investigated by the playback experiment on humpback whale (Megaptera novaeangliae and by sighting survey in the actual hydrofoil shipping service route. As a result, a physiological and behavioral change of the humpback whale was observed in the playback experiment of the new UWS sound, and the chance of hydrofoil encountering cetaceans of the new UWS sound was smaller than that of the previous UWS sound. Therefore, the improvement of the new UWS sound was confirmed. Lastly, we wish this research project would contribute toward the safer cruise of hydrofoil in the future.

  7. Nonlinear internal wave at the interface of two-layer liquid due to a moving hydrofoil

    Science.gov (United States)

    Wang, Zhen; Wu, Changhong; Zou, Li; Wang, Qianxi; Ding, Qi

    2017-07-01

    This paper is concerned with the internal wave at the interface of two layers of liquids due to a hydrofoil in the lower layer liquid. The two-layer fluid is assumed moving parallel to the interface at different velocities. The stratified flow is modeled based on the incompressible potential flow theory, with the nonlinear boundary conditions at the interface. Boundary integral equations are formulated for the fully nonlinear interfacial wave generated by the hydrofoil. The numerical model results in a set of nonlinear algebra equations, which are solved using the quasi-Newton method. We show that the quasi-Newton method is more efficient than Newton's method, which is often used for solving these types of equations in the literature. The wave profiles were analyzed in terms of the location and thickness of the hydrofoil, the Froude number, and the ratio of the densities of the two fluids. The computations show that the interfacial wave amplitude showed a trend first of increase and then of decrease with the distance between the hydrofoil and the still interface.

  8. The effect of wall proximity on energy harvesting using a pitching and heaving hydrofoil

    Science.gov (United States)

    Su, Yunxing; Miller, Michael; Mandre, Shreyas; Breuer, Kenneth

    2015-11-01

    Measurements of energy harvesting using a heaving and pitching hydrofoil with an aspect ratio 4.5 were taken in three different situations: unconfined, in close proximity to one wall and in close proximity to two walls. Measured lift and torque forces were used with the hydrofoil positions to calculate the efficiency of energy extracted from the flow. There was a modest increase in efficiency with one-wall proximity, while a pronounced increase in efficiency (up to 50%) was realized when the hydrofoil operated between two walls with strong confinement. The lift coefficient of the hydrofoil experienced a noticeable increase in two-wall proximity cases with the strong confinement, which directly contributed to the increase in efficiency of energy harvesting. In the case of two-wall confinement, we found that the optimal frequency and pitch amplitude were higher than those for both the free stream and the one-wall proximity cases. The power extracted from the heaving motion was greatly enhanced by two-wall proximity at high frequencies and high pitch amplitudes and these gains exceeded the additional power required to execute the pitching motion, resulting in the net increase in energy harvesting effectiveness. ARPA-e.

  9. Effect of wavelength of fish-like undulation of a hydrofoil in a free ...

    Indian Academy of Sciences (India)

    Thekkethil Namshad

    Effect of wavelength of fish-like undulation of a hydrofoil in a free-stream ... wavelength is shown to lead to the transition from the undulating motion to pitching motion. The effect of wavelength of undulation is studied numerically at a Reynolds number Re ¼ 4000, maximum amplitude of ..... The border grid points in the fluid.

  10. A numerical study of unsteady cavitation on a hydrofoil by les and URANS method

    NARCIS (Netherlands)

    Li, Zi Ru; Zhang, Guang Ming; He, Wei Dong; van Terwisga, T.J.C.; Farhat, M.; Müller, A.

    2015-01-01

    In this paper, the unsteady cavitation phenomena on a NACA0015 hydrofoil is numerically simulated by unsteady Reynolds-Averaged Navier-Stokes (URANS) method and Large Eddy Simulation (LES) in single-fluid approaches to multiphase modelling, respectively. It is observed that the large-scale

  11. Boundary layer effects on the vortex shedding in a Donaldson- type hydrofoil

    International Nuclear Information System (INIS)

    Fontanals, A; Guardo, A; Egusquiza, E; Zobeiri, A; Farhat, M; Avellan, F

    2014-01-01

    Fluid - Structure Interaction (FSI) phenomena is becoming a relevant study field for the design or revamping of hydropower plants. The generalized trend of increasing flow rates and reducing rotor blades/stay vanes thickness in order to improve the efficiency of the machine together with a major push from plant owners/operators for production flexibility (partial load operation is more common nowadays) make the FSI between the vortex shedding phenomenon and the vanes/blades of the machine an area of interest. From a design point of view, the machine structure has to resist all the hydrodynamic forces generated and maintain tension stresses under the fatigue limit to ensure a machine lifetime of several decades. To accomplish that goal, designers have to assure there is no presence of strong coupling phenomena (lock-in) between the vortex shedding frequency and the eigenfrequencies of the structure. As the vortex street is directly related to the state of the boundary layer along the hydrofoil, in this paper the effect of the boundary layer on the vortex shedding in a Donaldson-type hydrofoil is studied using Computational Fluid Dynamics (CFD). The development of the boundary layer along the Donaldson trailing edge hydrofoil chord is presented under lock-off conditions. The results are validated against previously obtained experimental results. Since the Donaldson trailing edge is non-symmetric, the boundary layer velocity profiles are reported for the suction and pressure side of the hydrofoil. In addition, the effect of the Donaldson trailing edge on laminar-to-turbulent transition on both sides of the hydrofoil is studied

  12. Results from the field test of two 1 kW oscillating hydrofoil generators in a tidal canal

    Science.gov (United States)

    Miller, Michael; Cardona, Jennifer; Block, Leanne; Kondo, Kenta; Lee, Michael; Lorick, Rebecca; Manning, Michael; Scherl, Isabel; Simeski, Filip; Spaulding, Arriane; Su, Yunxing; Ellerby, David; Sudderth, Erika; Lewis, Kristen; Kidd, James; Hubbard, William; Pham, Hung Tom; Derecktor, Tom; Winckler, Steve; Fawzi, Alice; Franck, Jennifer; Breuer, Kenneth; Mandre, Shreyas

    2016-11-01

    We present results from field tests of two 1 kW hydrokinetic energy capture devices operating in the Cape Cod Canal, in Bourne, MA. Each device consists of two oscillating hydrofoils with a chord of 0.24 m and span of 1.35 m, operating 90° out of phase with each other and driving a single generator. The pitch of each hydrofoil is mechanically coupled to the heave, also with a 90° phase difference. The two devices are arranged in tandem with a stream-wise separation of 1 span. We find that depending on the operating conditions, the hydrofoil oscillations may synchronize with each other through hydrodynamic interactions. Furthermore, in their optimized operation, the trailing device generates 60-80% of the power generated by the leading device, despite being directly in the wake of the hydrofoils of the upstream device. ARPA-e DE AR0000318.

  13. Effects of a sweptback hydrofoil on the force and longitudinal stability characteristics of a typical high-speed airplane

    Science.gov (United States)

    Wood, Raymond B

    1948-01-01

    An investigation was conducted in the Langley 8-foot high-speed tunnel to determine the effects of a sweptback hydrofoil on the force and longitudinal stability characteristics of a typical high-speed airplane. The Mach number range for this investigation was from 0.60 to 0.95 and at M = 1.20. The effects of the hydrofoil on the lift, drag, and pitching-moment characteristics are presented.

  14. Numerical simulation for submerged body fitted with hydrofoil by boundary element method; Kyokai yosoho ni yoru yokutsuki bossuitai mawari no nagare keisan

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, S.; Kasahara, Y.; Ashidate, I. [NKK Corp., Tokyo (Japan)

    1996-12-31

    In a high-speed boat of a type using hydrofoils, lifting force increases in proportion to square of its length, while displacement is proportional to the third power. Therefore, an idea has come up that speed of a large boat may be increased by combining the hydrofoils with a submerged body. In other words, the idea is to levitate a ship by using composite support consisting of buoyancy of the submerged body and lifting force caused by the hydrofoils. Insufficiency of the lifting force may be complemented by the buoyancy of the submerged body which increases in an equivalent rate as that in the displacement. However, combining a submerged body with hydrofoils render a problem that lifting force for hydrofoils decreases because of interactions among the submerged body, hydrofoils, and free surface. Therefore, assuming a model of a submerged body with a length of 85 m cruising at 40 kt, analysis was given on decrease in lifting force for hydrofoils due to interactions between the submerged and lifting body and free surface by using the boundary element method. As a result, it was verified that the lifting force for the hydrofoils decreases as a result of creation of a flow that decreases effective angle of attach of the hydrofoils. It was also made clear that making the submerging depth greater reduces the decrease in the lifting force. 9 refs., 14 figs., 1 tab.

  15. Flow Characteristics Near to Stent Strut Configurations on Femoropopliteal Artery

    Science.gov (United States)

    Paisal, Muhammad Sufyan Amir; Fadhil Syed Adnan, Syed; Taib, Ishkrizat; Ismail, Al Emran; Kamil Abdullah, Mohammad; Nordin, Normayati; Seri, Suzairin Md; Darlis, Nofrizalidris

    2017-08-01

    Femoropopiteal artery stenting is a common procedure suggested by medical expert especially for patient who is diagnosed with severe stenosis. Many researchers reported that the growth of stenosis is significantly related to the geometry of stent strut configuration. The different shapes of stent geometry are presenting the different flow pattern and re-circulation in stented femoropopliteal artery. The blood flow characteristics near to the stent geometry are predicted for the possibility of thrombosis and atherosclerosis to be formed as well as increase the growth of stenosis. Thus, this study aims to determine the flow characteristic near to stent strut configuration based on different hemodynamic parameters. Three dimensional models of stent and simplified femoropopliteal artery are modelled using computer aided design (CAD) software. Three different models of stent shapes; hexagon, circle and rectangle are simulated using computational fluid dynamic (CFD) method. Then, parametric study is implemented to predict the performance of stent due to hemodynamic differences. The hemodynamic parameters considered are pressure, velocity, low wall shear stress (WSSlow) and wall shear stress (WSS). From the observation, flow re-circulation has been formed for all simulated stent models which the proximal region shown the severe vortices. However, rectangular shape of stent strut (Type P3) shows the lowest WSSlow and the highest WSS between the range of 4 dyne/cm2 and 70 dyne/cm2. Stent Type P3 also shows the best hemodynamic stent performance as compare to others. In conclusion, Type P3 has a favourable result in hemodynamic stent performance that predicted less probability of thrombosis and atherosclerosis to be formed as well as reduces the growth of restenosis.

  16. Portal WEB 2.0. utilizando Framework Struts

    OpenAIRE

    Palacín Mateo, Manuel

    2007-01-01

    El propósito de este proyecto es la implementación de un portal interactivo de contactos utilizando las tecnologías J2EE mediante Struts y siguiendo la tendencia Web 2.0. Previo a esta implementación se ha hecho una valoración del mercado actual de los portales de contactos y se han evaluado los servicios que ofrecen para posteriormente añadirlos a la demostración tecnológica. Tras esto se ha explicado lo que es la tendencia Web 2.0. Finalmente se han evaluado las diferentes opciones o tec...

  17. Six-strut arrangements for cartesian movements of mirrors

    International Nuclear Information System (INIS)

    Noll, T.; Zeschke, Th.; Reichardt, G.; Lammert, H.; Gudat, W.

    2001-01-01

    At BESSY a new six-strut arrangement for general small travel mirror adjustment mechanisms has been developed. This patented (Patent DE 10042802.5) arrangement allows very simple movements in all six linear and rotational degrees of freedom. The movements of the mirror are simply determined by moving either one drive, or up to three drives by the same amount. The first mirror adjustment systems of this design is successfully in operation since the start of BESSY II. Their performance and reliability is very satisfactory. This contribution will present the concepts

  18. Investigation of mixing characteristics in strut injectors using modal decomposition

    Science.gov (United States)

    Soni, Rahul Kumar; De, Ashoke

    2018-01-01

    Effect of a large-scale vortical structure on mixing and spreading of a shear layer is numerically investigated. Two strut configurations, namely, straight and tapered struts at two convective Mach numbers (Mc = 1.4 and 0.37) for two jet heights (0.6 and 1 mm) are investigated. The hydrogen jet is injected through a two-dimensional slot in oncoming coflow at Mach 2. An excellent agreement between simulated and experimental data is witnessed, whereas the instantaneous data reveal the presence of various large-scale structures in the flow field. From the instantaneous field, it becomes apparent that both the geometries have different vortical breakdown locations. It is also noticed that an early onset of vortex breakdown manifests itself into the mixing layer thickness enhancement, the effect of which is reflected in overall mixing characteristics. It becomes evident that the shear strength plays an important role in the near field mixing. The higher shear strength promotes the generation of large vortices. The analysis shows that the SS-0.6 case offers highest mixing efficiency being dominated by relatively large-scale structures. Eigenmodes obtained through Proper Orthogonal Decomposition (POD) confirm the presence of dominating structures and shed light into the series of events involved in vortex pairing/merging and breakdown. Dynamic modal decomposition also strengthens the observation made through the POD.

  19. Prediction of cryogenic cavitation around hydrofoil by an extensional Schnerr-Sauer cavitation model

    Science.gov (United States)

    Sun, T. Z.; Wei, Y. J.; Wang, C.

    2015-12-01

    Developing a robust computational strategy to address the rich physics characteristic involved in the thermodynamic effects on the cryogenic cavitation remains a challenging problem. The objective of this present study is to model the numerical methodology to simulate the cryogenic cavitation by implanting the thermodynamic effects to the Schnerr-Sauer cavitation model, and coupling the energy equation considered the latent heat. For this purpose, cavitating flows are investigated over a three dimensional hydrofoil in liquid hydrogen and nitrogen. Experimental measurements of pressure and temperature are utilized to validate the extensional Schnerr-Sauer cavitation model. Specifically, the further analysis of the cavitation solution with respect to the thermodynamic term is conducted. The results show that the extensional Schnerr-Sauer cavitation model predicts better accuracy to the quasi-steady cavitation over hydrofoil in the two cryogenic fluids.

  20. Hydrofoils : aplicació a la Copa Amèrica

    OpenAIRE

    Amens Murtra, Francesc Xavier

    2016-01-01

    Hydrofoils. Aplicació tècnica a la copa Amèrica.” És un treball que té cabuda dins de l’àmbit de la mecànica de fluids amb l’objectiu d’entendre d’una millor manera el com funcionen les hidroales, i un possible disseny i aplicació en les embarcacions que corren l’anomenada copa Amèrica. Els hydrofoils son uns perfils alars amb la peculiaritat que estan dissenyats per treballar a l’aigua, com que la densitat de l’aigua es de l’ordre de 1000x superior a la de l’aire, són perfils relativament p...

  1. Numerical Investigation on Vortex Shedding from a Hydrofoil with a Beveled Trailing Edge

    Directory of Open Access Journals (Sweden)

    Seung-Jae Lee

    2015-01-01

    study, we numerically investigated vortex shedding from various beveled trailing edges at a Reynolds number of 106. We then compared the numerical results with the experimental data, which show good agreement. We also conducted numerical simulations of wakes behind the hydrofoil at rest in periodically varying flows. Results reveal that vortex shedding is affected by the periodicity of a free-stream flow, as well as the trailing-edge shape.

  2. Determine the Correlation between Wicked Gates Angles and Servomotors Strokes for Asymmetric Hydrofoil

    Directory of Open Access Journals (Sweden)

    Daniel Daia

    2013-05-01

    Full Text Available The paper describe the results obtained from theoretical calculus of the kinematics of the wicked gates for the correlation: ao=f(α; aor=ao/Do(α; S=f(α and propose analytical formulas for ao=f(α correlation, applicable to 16, 24 wicked gates blade number and asymmetrical hydrofoils; also, numerical results compared with graphical values are presented.

  3. Characterisation of sheet cavity noise of a hydrofoil using the Ffowcs Williams-Hawkings acoustic analogy

    OpenAIRE

    Lidtke, Artur Konrad; Turnock, Stephen; Humphrey, Victor

    2016-01-01

    Concerns about pollution of the marine environment with ship-induced noise and the scarcity of available numerical methods have recently stimulated significant amounts of research in hydroacoustic modelling. In this work, Large Eddy Simulation (LES) is used with Schnerr-Sauer mass-transfer cavitation model and a porous Ffowcs Williams-Hawkings (FW-H) acoustic analogy in order to simulate sheet cavitation on a NACA0009 hydrofoil. The aim is to investigate how well the proposed method captures ...

  4. Cavitation control on a 2D hydrofoil through a continuous tangential injection of liquid: Experimental study

    Science.gov (United States)

    Timoshevskiy, M. V.; Zapryagaev, I. I.; Pervunin, K. S.; Markovich, D. M.

    2016-10-01

    In the paper, the possibility of active control of a cavitating flow over a 2D hydrofoil that replicates a scaled-down model of high-pressure hydroturbine guide vane (GV) was tested. The flow manipulation was implemented by a continuous tangential liquid injection at different flow rates through a spanwise slot in the foil surface. In experiments, the hydrofoil was placed in the test channel at the attack angle of 9°. Different cavitation conditions were reached by varying the cavitation number and injection velocity. In order to study time dynamics and spatial patterns of partial cavities, high-speed imaging was employed. A PIV method was used to measure the mean and fluctuating velocity fields over the hydrofoil. Hydroacoustic measurements were carried out by means of a pressure transducer to identify spectral characteristics of the cavitating flow. It was found that the present control technique is able to modify the partial cavity pattern (or even totally suppress cavitation) in case of stable sheet cavitation and change the amplitude of pressure pulsations at unsteady regimes. The injection technique makes it also possible to significantly influence the spatial distributions of the mean velocity and its turbulent fluctuations over the GV section for non-cavitating flow and sheet cavitation.

  5. Influence of polymer additive on flow past a hydrofoil: A numerical study

    Science.gov (United States)

    Xiong, Yongliang; Peng, Sai; Yang, Dan; Duan, Juan; Wang, Limin

    2018-01-01

    Flows of dilute polymer solutions past a hydrofoil (NACA0012) are examined by direct numerical simulation to investigate the modification of the wake pattern due to the addition of polymer. The influence of polymer additive is modeled by the FENE-P model in order to simulate a non-linear modulus of elasticity and a finite extendibility of the polymer macromolecules. Simulations were carried out at a Reynolds number of 1000 with the angle of attack varying from 0° to 20°. The results show that the influence of polymer on the flow behavior of the flow past a hydrofoil exhibits different flow regimes. In general, the addition of polymer modifies the wake patterns for all angles of attack in this study. Consequently, both drag and lift forces are changed as the Weissenberg number increases while the drag of the hydrofoil is enhanced at small angles of attack and reduced at large angles of attack. As the Weissenberg number increases, two attached recirculation bubbles or two columns of shedding vortices downstream tend to be symmetric, and the polymer tends to make the flow less sensitive to the variation of the angle of attack.

  6. Numerical investigation on cavitation flow of hydrofoil and its flow noise with emphasis on turbulence models

    Science.gov (United States)

    Kim, Sanghyeon; Cheong, Cheolung; Park, Warn-Gyu

    2017-06-01

    In this study, cavitation flow of hydrofoils is numerically investigated to characterize the effects of turbulence models on cavitation-flow patterns and the corresponding radiated sound waves. The two distinct flow conditions are considered by varying the mean flow velocity and angle of attack, which are categorized under the experimentally observed unstable or stable cavitation flows. To consider the phase interchanges between the vapor and the liquid, the flow fields around the hydrofoil are analyzed by solving the unsteady compressible Reynolds-averaged Navier-Stokes equations coupled with a mass-transfer model, also referred to as the cavitation model. In the numerical solver, a preconditioning algorithm with dual-time stepping techniques is employed in generalized curvilinear coordinates. The following three types of turbulence models are employed: the laminar-flow model, standard k - ɛ turbulent model, and filter-based model. Hydro-acoustic field formed by the cavitation flow of the hydrofoil is predicted by applying the Ffowcs Williams and Hawkings equation to the predicted flow field. From the predicted results, the effects of the turbulences on the cavitation flow pattern and radiated flow noise are quantitatively assessed in terms of the void fraction, sound-pressure-propagation directivities, and spectrum.

  7. Numerical investigation on cavitation flow of hydrofoil and its flow noise with emphasis on turbulence models

    Directory of Open Access Journals (Sweden)

    Sanghyeon Kim

    2017-06-01

    Full Text Available In this study, cavitation flow of hydrofoils is numerically investigated to characterize the effects of turbulence models on cavitation-flow patterns and the corresponding radiated sound waves. The two distinct flow conditions are considered by varying the mean flow velocity and angle of attack, which are categorized under the experimentally observed unstable or stable cavitation flows. To consider the phase interchanges between the vapor and the liquid, the flow fields around the hydrofoil are analyzed by solving the unsteady compressible Reynolds-averaged Navier–Stokes equations coupled with a mass-transfer model, also referred to as the cavitation model. In the numerical solver, a preconditioning algorithm with dual-time stepping techniques is employed in generalized curvilinear coordinates. The following three types of turbulence models are employed: the laminar-flow model, standard k − ε turbulent model, and filter-based model. Hydro-acoustic field formed by the cavitation flow of the hydrofoil is predicted by applying the Ffowcs Williams and Hawkings equation to the predicted flow field. From the predicted results, the effects of the turbulences on the cavitation flow pattern and radiated flow noise are quantitatively assessed in terms of the void fraction, sound-pressure-propagation directivities, and spectrum.

  8. Use of Cortical Strut Allograft After Extended Trochanteric Osteotomy in Revision Total Hip Arthroplasty.

    Science.gov (United States)

    Lim, Chin Tat; Amanatullah, Derek F; Huddleston, James I; Hwang, Katherine L; Maloney, William J; Goodman, Stuart B

    2017-05-01

    Cortical strut allografts restore bone stock and improve postoperative clinical scores after revision total hip arthroplasty (THA). However, use of a cortical strut allograft is implicated in delayed healing of an extended trochanteric osteotomy (ETO). To date, there are no reports directly comparing ETO with or without cortical strut allografts. We reviewed prospectively gathered data on 50 revision THAs performed from 2004-2014 using an ETO. We compared the demographic, radiological, and clinical outcome of patients with (16 hips) and without (34 hips) cortical strut allograft after an ETO. There were no significant differences in Western Ontario McMaster Universities Osteoarthritis Index or Harris Hip Score between the ETOs with and without a cortical strut allograft. Fifteen of the ETOs (94%) with a cortical strut allograft and 31 of the ETOs (91%) without a cortical strut allograft were in situ at final follow-up (P = 1.000). A higher proportion hips with cortical strut allograft (100%, 16 patients) had preoperative Paprosky grade bone loss more than IIIA compared to those without allograft (29%, 10 patients) (P revision THA with ETO does not reduce the rate of union, radiological or clinical outcomes. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Experimental Investigation of a High-Speed Hydrofoil with Parabolic Thickness Distribution and an Aspect Ratio of 3

    Science.gov (United States)

    Christopher, Kenneth W.

    1961-01-01

    An experimental investigation has been made to determine the hydro-dynamic characteristics of a 10-percent-thick hydrofoil with an aspect ratio of 3 designed to operate with acceptable efficiency at speeds in the neighborhood of 100 knots (169 fps). A cambered hydrofoil model with parabolic thickness distribution was investigated at a depth of chord over a range of angles of attack from -0.5 deg to 4.0 deg and at speeds from 120 to 210 fps. substantially wider range of operation at acceptable lift-drag ratios as well as higher maximum lift-drag-ratio values than did a hydrofoil of similar design with an aspect ratio of 1.

  10. Robust Course Keeping Control of a Fully Submerged Hydrofoil Vessel with Actuator Dynamics: A Singular Perturbation Approach

    Directory of Open Access Journals (Sweden)

    Sheng Liu

    2017-01-01

    Full Text Available This paper presents a two-time scale control structure for the course keeping of an advanced marine surface vehicle, namely, the fully submerged hydrofoil vessel. The mathematical model of course keeping control for the fully submerged hydrofoil vessel is firstly analyzed. The dynamics of the hydrofoil servo system is considered during control design. A two-time scale model is established so that the controllers of the fast and slow subsystems can be designed separately. A robust integral of the sign of the error (RISE feedback control is proposed for the slow varying system and a disturbance observer based state feedback control is established for the fast varying system, which guarantees the disturbance rejection performance for the two-time scale systems. Asymptotic stability is achieved for the overall closed-loop system based on Lyapunov stability theory. Simulation results show the effectiveness and robustness of the proposed methodology.

  11. Robust Course Keeping Control of a Fully Submerged Hydrofoil Vessel without Velocity Measurement: An Iterative Learning Approach

    Directory of Open Access Journals (Sweden)

    Sheng Liu

    2017-01-01

    Full Text Available This paper proposes a novel robust output feedback control methodology for the course keeping control of a fully submerged hydrofoil vessel. Based on a sampled-data iterative learning strategy, an iterative learning observer is established for the estimation of system states and the generalized disturbances. With the state observer, a feedback linearized iterative sliding mode controller is designed for the stabilization of the lateral dynamics of the fully submerged hydrofoil vessel. The stability of the overall closed-loop system is analyzed based on Lyapunov stability theory. Comparative simulation results verify the effectiveness of the proposed control scheme and show the dominance of the disturbance rejection performance.

  12. Numerical and experimental investigation of natural flow-induced vibrations of flexible hydrofoils

    Science.gov (United States)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Lelong, Alexandra; Astolfi, Jacques Andre; Young, Yin Lu

    2016-07-01

    The objective of this work is to present combined numerical and experimental studies of natural flow-induced vibrations of flexible hydrofoils. The focus is on identifying the dependence of the foil's vibration frequencies and damping characteristics on the inflow velocity, angle of attack, and solid-to-fluid added mass ratio. Experimental results are shown for a cantilevered polyacetate (POM) hydrofoil tested in the cavitation tunnel at the French Naval Academy Research Institute (IRENav). The foil is observed to primarily behave as a chordwise rigid body and undergoes spanwise bending and twisting deformations, and the flow is observed to be effectively two-dimensional (2D) because of the strong lift retention at the free tip caused by a small gap with a thickness less than the wall boundary layer. Hence, the viscous fluid-structure interaction (FSI) model is formulated by coupling a 2D unsteady Reynolds-averaged Navier-Stokes (URANS) model with a two degree-of-freedom (2-DOF) model representing the spanwise tip bending and twisting deformations. Good agreements were observed between viscous FSI predictions and experimental measurements of natural flow-induced vibrations in fully turbulent and attached flow conditions. The foil vibrations were found to be dominated by the natural frequencies in absence of large scale vortex shedding due to flow separation. The natural frequencies and fluid damping coefficients were found to vary with velocity, angle of attack, and solid-to-fluid added mass ratio. In addition, the numerical results showed that the in-water to in-air natural frequency ratios decreased rapidly, and the fluid damping coefficients increased rapidly, as the solid-to-fluid added mass ratio decreases. Uncoupled mode (UM) linear potential theory was found to significantly over-predict the fluid damping for cases of lightweight flexible hydrofoils, and this over-prediction increased with higher velocity and lower solid-to-fluid added mass ratio.

  13. Analysis and Optimation Hydrofoil Supported Catamaran (HYSUCAT Size 25 Meter based on CFD Method

    Directory of Open Access Journals (Sweden)

    Hari Prastowo

    2016-12-01

    Full Text Available In the field of transportation, ship is relatively cheap then others transportation. However, the ship still has constraints on speed and fuel consumption. Therefore, the ship has many variations of shape to achieve optimal condition. For example the body of ships with double hulls (catamaran or three (trimaran, that using foil to make ship can have a smaller resistance to achieve optimal efficiency. The purpose of this research in order to plan the maximum foil shape which can produce high force of buoyance on the catamaran boat (25 meters and also to determine the type of hydrofoil that produces maximum buoyance force using CFD method.

  14. Numerical evaluation of cavitation void ratio significance on hydrofoil dynamic response

    Science.gov (United States)

    Liu, Xin; Wang, Zhengwei; Escaler, Xavier; Zhou, Lingjiu

    2015-12-01

    The added mass effects on a NACA0009 hydrofoil under cavitation conditions determined in a cavitation tunnel have been numerically simulated using finite element method (FEM). Based on the validated model, the effects of averaged properties of the cavity considered as a two-phase mixture have been evaluated. The results indicate that the void ratio of the cavity plays an increasing role on the frequency reduction ratio and on the mode shape as the mode number increases. Moreover, the sound speed shows a more important role than the average cavity density.

  15. Spatio-temporal description of the cavitating flow behavior around NACA 2412 hydrofoil

    Science.gov (United States)

    Rudolf, P.; Štefan, D.; Sedlář, M.; Kozák, J.; Habán, V.; Huzlík, R.

    2015-12-01

    Spatio-temporal description of the cavitating flow around hydrofoil with 8 degrees incidence using proper orthogonal decomposition (POD) is presented. POD is a suitable tool, which provides information not only about the flow dynamics, but also about relevance of different flow structures. POD also enables to track energy transport within the domain and energy transfer among the eigenmodes of the flow field. Analysis documents change of the flow structure for decreasing cavitation number, which can be most likely attributed to sheet/cloud cavitation transition.

  16. A numerical study of unsteady cavitation on a hydrofoil by LES and URANS method

    Science.gov (United States)

    Li, Zi-ru; Zhang, Guang-ming; He, Wei; van Terwisga, Tom

    2015-12-01

    In this paper, the unsteady cavitation phenomena on a NACA0015 hydrofoil is numerically simulated by unsteady Reynolds-Averaged Navier-Stokes (URANS) method and Large Eddy Simulation (LES) in single-fluid approaches to multiphase modelling, respectively. It is observed that the large-scale structures and characteristic periodic shedding predicted by the URANS with the modified SST k-ω turbulence model show a good qualitative match with the experimental observations but with quantitative discrepancies, such as a different cavity length and volume, and a different location of shedding. Compared to the URANS results, the LES results reproduce more details of unsteady dynamics with an improved quantitative agreement.

  17. Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

    Directory of Open Access Journals (Sweden)

    Ristić Slavica S.

    2010-01-01

    Full Text Available Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp was experimentally determined by Laser Doppler Anemometry (LDA measurements. Two models were tested: model of airplane G4 (Super Galeb and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles.

  18. Fluid-mediated stability and speed-increase for heaving hydrofoils swimming side-by-side

    Science.gov (United States)

    Newbolt, Joel; Zhang, Jun; Ristroph, Leif

    2017-11-01

    As an example of collective motion in active swimmers we study the fluid-mediated interaction between two heaving hydrofoils that swim with a fixed transverse separation (between the heaving mid-heights) but are free to independently choose their forward swimming speeds and positions. Experiments reveal that out-of-phase foils are attracted to a side-by-side configuration which also increases the swimming speed of the pair (up to 59% faster for our parameters), while in-phase foils are repelled from this configuration. Because this type of swimming is qualitatively similar to that of fish and birds this interaction could be important to schooling and flocking.

  19. Boron-epoxy-reinforced titanium aircraft landing-gear drag strut

    International Nuclear Information System (INIS)

    Howell, W.E.

    1976-11-01

    The structural performance of a boron-epoxy-reinforced titanium drag strut, containing a bonded scarf joint and designed to the criteria of a large commercial transport, has been evaluated experimentally and analytically. The strut was exposed to two lifetimes of fatigue loading and was statically loaded to the tensile and compressive design ultimate loads. Throughout the test program no evidence of any damage in the drag strut was detected by strain-gage measurements, ultrasonic inspection, or visual observation. The bonded joint was analyzed using the NASTRAN computer program. A comparison of the strains predicted by the NASTRAN computer program with the experimentally determined values shows excellent agreement. An analytical study indicated that the nonlinear behavior of a structural spacer at each end of the strut could be explained by the inelastic behavior and possible creep of the adhesive

  20. Beam Shear Design According to Eurocode 2 - Limitations for the Concrete Strut Inclinations

    DEFF Research Database (Denmark)

    Hagsten, Lars German; Hestbech, Lars; Fisker, Jakob

    2011-01-01

    and are presented. These beams are all designed to fail in shear and the shear reinforcement is designed for different values of the concrete strut inclinations (cot θ varies from 1.5 to 3.4). These tests indicate a clear connection between the values of the concrete strut inclinations and crack width in the SLS......The beam shear design method adopted in Eurocode 2 is based on a lower bound plastic solution. This method is combined with limitations on the concrete strut inclination, θ. These limitations are introduced to ensure acceptable crack width in the SLS. 7 full scale beams have been tested....... In cases where larger crack widths (w > 0.4 mm) can be accepted, larger values of the concrete strut inclinations can be chosen. This will lead to less shear reinforcements. The results are also compared with analytical analysis based on energy methods. At the SLS the beams are expected to be cracked...

  1. Numerical estimation of interactions between foils and hulls of hydrofoil catamaran; Suichu yokutsuki sodosen no sentai to suichuyoku no sogo kansho

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, K.; Ando, J.; Nakatake, K. [Kyushu University, Fukuoka (Japan)

    1998-09-04

    The hydrofoil catamaran model which is built up with the twin Wigley hulls and the tandem fore and aft set of hydrofoils is used for the numerical calculation and the experiments of this model was performed at Kyushu University. In this paper, combining with a Rankine source method, the SQCM (a simple panel method) is applied to the unsymmetrical flow problem around catamarans. And the running attitude of the model is not fixed in both the calculation and the experiments. Comparing with the experiment we show the interaction between hulls and the hydrofoils for the lift and the wave-making resistance in the high speed range. 6 refs., 11 figs.

  2. Outlet strut fracture and leaflet escape of Bjork-Shiley convexo-concave valve.

    Science.gov (United States)

    Uchino, Gaku; Yoshida, Hideo; Sakoda, Naoya; Hattori, Shigeru; Kawabata, Takuya; Saiki, Munehiro; Fujita, Yasufumi; Yunoki, Keiji; Hisamochi, Kunikazu; Mine, Yoshinari

    2017-06-01

    Prosthetic valve fracture is a serious complication and may arise in patient post-valve replacement. We experienced an outlet strut fracture and leaflet escape of a Bjork-Shiley convexo-concave valve. We performed an emergency redo mitral valve replacement and successfully retrieved the fractured strut and escaped leaflet from superficial femoral artery and the abdominal aorta. The patient showed an uneventful postoperative recovery.

  3. Dynamic analysis of six-strut supporting system for accelerator magnet

    International Nuclear Information System (INIS)

    Leung, K.K.

    1994-01-01

    A six-strut magnet support system designed by Lawrence Berkeley Laboratory (LBL) is considered as an alternative to the current SSC magnet support system. The LBL designed a six-strut support system based on the kinematics mount concept that is generally used in the optical and the laser communication industries. The six-strut system is defined by six static degrees of freedom that constrain a point in space with no redundant restraint. Adjustment of any strut's length means redefining the translation or rotational degree of freedom of the mounting point and produces the desirable movement of the magnet system. The accurately operated six-strut mounting system used in the Berkeley's Advance Light Source (ALS) magnet support is able to maintain the magnet system structural integrity to survive a 7 earthquake, position the magnet to high tolerances, have a small footprint, simple to operate, and adjust to a micron level of accuracy. Though finite element simulation has been used for years in safety analysis, such as seismic dynamic response analysis in nuclear reactor and piping supports, in late 1970, it was employed in the dynamic study for a magnet system in Lawrence Berkeley Laboratory in the late eighties. The modeling methodology developed in LBL for the six-strut system design, especially for the critical mounting joint design under dynamic loads, is presented in this paper and may be employed for prospective SSC accelerator magnet supporting system design

  4. Effect of increased strut porosity of calcium phosphate bone graft substitute biomaterials on osteoinduction.

    Science.gov (United States)

    Coathup, Melanie J; Hing, Karin A; Samizadeh, Sorousheh; Chan, Oliver; Fang, Yvette S; Campion, Charlie; Buckland, Thomas; Blunn, Gordon W

    2012-06-01

    The effect of increasing strut porosity on the osteoinductivity of porous calcium phosphate (CaP) and silicate-substituted calcium phosphate (SiCaP) bone substitute materials was investigated in an ovine ectopic model. One to two millimeter-sized granules or block implants with strut porosities of 10, 20, or 30% were inserted into the left and right paraspinalis muscle. At 12 weeks, histological sections were prepared through the center of each implant and bone contact, bone area and implant area quantified. Backscattered scanning electron microscopy (bSEM) was used to visualize bone within small pores in the struts of the scaffolds. Increased bone formation was measured in the SiCaP with 30% strut porosity (5.482% ± 1.546%) when compared with the nonsilicate CaP with the same morphology (1.160% ± 0.502%, p = 0.02), indicating that silicate substitution may increase osteoinduction. Greater bone formation was seen in scaffolds with increased strut porosity. No bone growth was found in any of the SiCaP scaffold with 10% porosity. There was no significant difference between block and granule specimens. Scanning electron microscopy and EDX in combination with histology demonstrated bone formation within pores <5 μm in size. The use of silicate-substituted CaP material with increased strut porosity may further augment repair and regeneration in bony sites. Copyright © 2012 Wiley Periodicals, Inc.

  5. Comparison of turbulent separation over a smooth surface and mako shark skin on a NACA 4412 hydrofoil

    Science.gov (United States)

    Smith, Drew; Lang, Amy; Wahidi, Redha

    2011-11-01

    Shark skin is being investigated as a means of passive flow separation control due to the flexibility and preferential flow direction of the scales covering the skin. In this study, the effect of the scales is observed in a tripped turbulent boundary layer by comparing the flow over a NACA 4412 hydrofoil with a smooth surface to that over the same hydrofoil with samples of mako shark skin affixed to its upper surface. These samples were taken from the flank area of the shark because the scales at that location have been shown to have the greatest angle of erection, and thus the best potential for separation control. All flow data in this study was obtained using Time-Resolved Digital Particle Image Velocimetry and recorded at multiple angles of attack (between 8 and 16 degrees) and two Reynolds numbers. The flow was primarily analyzed by means of the backflow coefficient (a value based on the percentage of time that flow in a region over the hydrofoil is reversed) and the time history of instantaneous flow velocity values at specific points in the boundary layer over the hydrofoil models. Research performed under NSF grant 0932352.

  6. Vortex wake interactions and energy harvesting from tandem pitching and heaving hydrofoils

    Science.gov (United States)

    Su, Yunxing; Cardona, Jennifer; Miller, Michael; Mandre, Shreyas; Breuer, Kenneth

    2016-11-01

    Measurements of flow structure and power extraction by tandem pitching and heaving hydrofoils are conducted in a flume. The leading and trailing hydrofoils are synchronized and aligned parallel to the oncoming flow. Force measurements and time-resolved PIV are used to characterize the system. The system efficiency of tandem foils with the same kinematics is quantified as a function of the phase difference between the foils and there exist favorable and unfavorable phase angles and that system efficiencies can be as large as 0.45. For unfavorable phase angles, PIV indicates that the leading edge vortex generated by the trailing foil, which is critical to good energy harvesting, is weakened by the oncoming wake from the leading foil. Conversely, at a favorable phase, the vortex shed from the leading foil enhances the performance of the trailing foil, compensating for the otherwise negative aspects of operating in the wake. A model, combining frequency, separation distance and a characteristic convection velocity, is introduced to predict the optimal phase region and is validated over a range of parameters. By changing the pitching amplitude and phase angle in trailing foil we show that relatively larger pitching amplitudes can further improve the system efficiency. ARPA-e.

  7. Numerical Analysis of Hydrodynamics for Bionic Oscillating Hydrofoil Based on Panel Method.

    Science.gov (United States)

    Xue, Gang; Liu, Yanjun; Zhang, Muqun; Ding, Hongpeng

    2016-01-01

    The kinematics model based on the Slender-Body theory is proposed from the bionic movement of real fish. The Panel method is applied to the hydrodynamic performance analysis innovatively, with the Gauss-Seidel method to solve the Navier-Stokes equations additionally, to evaluate the flexible deformation of fish in swimming accurately when satisfying the boundary conditions. A physical prototype to mimic the shape of tuna is developed with the revolutionized technology of rapid prototyping manufacturing. The hydrodynamic performance for rigid oscillating hydrofoil is analyzed with the proposed method, and it shows good coherence with the cases analyzed by the commercial software Fluent and the experimental data from robofish. Furthermore, the hydrodynamic performance of coupled hydrofoil, which consisted of flexible fish body and rigid caudal fin, is analyzed with the proposed method. It shows that the caudal fin has great influence on trailing vortex shedding and the phase angle is the key factor on hydrodynamic performance. It is verified that the shape of trailing vortex is similar to the image of the motion curve at the trailing edge as the assumption of linear vortex plane under the condition of small downwash velocity. The numerical analysis of hydrodynamics for bionic movement based on the Panel method has certain value to reveal the fish swimming mechanism.

  8. Study of Cavitation Shedding Dynamics on a NACA0015 Hydrofoil Using X-Ray Densitometry

    Science.gov (United States)

    Ganesh, Harish; Wu, Juliana; Ceccio, Steven

    2016-11-01

    Cavitation dynamics on the NACA0015 hydrofoil at several attack angles are found to be spectrally rich, being multi-modal with abrupt changes in Strouhal number with change in cavitation number. Present study focusses on identifying the physical mechanisms responsible for the change in cavitation dynamics on a NACA0015 hydrofoil in a re-circulating water tunnel using time resolved X-ray densitometry. Time-resolved void fraction flow fields obtained using X-ray densitometry, synchronized with acoustic noise measurements using a hydrophone, are used to identify different flow features and mechanisms that are responsible for the change in the observed spectral behavior. It is shown that under higher cavitation numbers, the shedding mechanism is predominantly re-entrant liquid flow based, but as the cavitation number drops many different processes are at play. At lower cavitation numbers, the shed cavity cloud collapse arrests cavity growth and this results in altered cycle dynamics and hence the Strouhal number. In addition, propagation bubbly shock waves are also found to be a dominant mechanism of shedding for certain conditions. The multi-modal nature of the acoustic pressure signature is explained by presence of different flow features, which could be concurrent or alternating. Office of Naval Research.

  9. Numerical Analysis of Hydrodynamics for Bionic Oscillating Hydrofoil Based on Panel Method

    Directory of Open Access Journals (Sweden)

    Gang Xue

    2016-01-01

    Full Text Available The kinematics model based on the Slender-Body theory is proposed from the bionic movement of real fish. The Panel method is applied to the hydrodynamic performance analysis innovatively, with the Gauss-Seidel method to solve the Navier-Stokes equations additionally, to evaluate the flexible deformation of fish in swimming accurately when satisfying the boundary conditions. A physical prototype to mimic the shape of tuna is developed with the revolutionized technology of rapid prototyping manufacturing. The hydrodynamic performance for rigid oscillating hydrofoil is analyzed with the proposed method, and it shows good coherence with the cases analyzed by the commercial software Fluent and the experimental data from robofish. Furthermore, the hydrodynamic performance of coupled hydrofoil, which consisted of flexible fish body and rigid caudal fin, is analyzed with the proposed method. It shows that the caudal fin has great influence on trailing vortex shedding and the phase angle is the key factor on hydrodynamic performance. It is verified that the shape of trailing vortex is similar to the image of the motion curve at the trailing edge as the assumption of linear vortex plane under the condition of small downwash velocity. The numerical analysis of hydrodynamics for bionic movement based on the Panel method has certain value to reveal the fish swimming mechanism.

  10. Physical and numerical investigation of the flow induced vibration of the hydrofoil

    Science.gov (United States)

    Wu, Q.; Wang, G. Y.; Huang, B.

    2016-11-01

    The objective of this paper is to investigate the flow induced vibration of a flexible hydrofoil in cavitating flows via combined experimental and numerical studies. The experiments are presented for the modified NACA66 hydrofoil made of POM Polyacetate in the closed-loop cavitation tunnel at Beijing Institute of Technology. The high-speed camera and the single point Laser Doppler Vibrometer are applied to analyze the transient flow structures and the corresponding structural vibration characteristics. The hybrid coupled fluid structure interaction model is conducted to couple the incompressible and unsteady Reynolds Averaged Navier-Stokes solver with a simplified two-degree-of-freedom structural model. The k-ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model are introduced to the present simulations. The results showed that with the decreasing of the cavitation number, the cavitating flows display incipient cavitation, sheet cavitation, cloud cavitation and supercavitation. The vibration magnitude increases dramatically for the cloud cavitation and decline for the supercavitation. The cloud cavitation development strongly affects the vibration response, which is corresponding to the periodically developing and shedding of the large-scale cloud cavity. The main frequency of the vibration amplitude is accordance with the cavity shedding frequency and other two frequencies of the vibration amplitude are corresponding to the natural frequencies of the bending and twisting modes.

  11. Numerical and experimental study of the leakage flow in guide vanes with different hydrofoils

    Directory of Open Access Journals (Sweden)

    Sailesh Chitrakar

    2017-07-01

    Full Text Available Clearance gaps between guide vanes and cover plates of Francis turbines tend to increase in size due to simultaneous effect of secondary flow and erosion in sediment affected hydropower plants. The pressure difference between the two sides of the guide vane induces leakage flow through the gap. This flow enters into the suction side with high acceleration, disturbing the primary flow and causing more erosion and losses in downstream turbine components. A cascade rig containing a single guide vane passage has been built to study the effect of the clearance gap using pressure sensors and PIV (Particle Image Velocimetry technique. This study focuses on developing a numerical model of the test rig, validating the results with experiments and investigating the behavior of leakage flow numerically. It was observed from both CFD and experiment that the leakage flow forms a passage vortex, which shifts away from the wall while travelling downstream. The streamlines contributing to the formation of this vortex have been discussed. Furthermore, the reference guide vane with symmetrical hydrofoil has been compared with four cambered profiles, in terms of the guide vane loading and the consequent effect on the leakage flow. A dimensionless term called Leakage Flow Factor (Lff has been introduced to compare the performances of hydrofoils. It is shown that the leakage flow and its effect on increasing losses and erosion can be minimized by changing the pressure distribution over the guide vane.

  12. Delayed coverage in malapposed and side-branch struts with respect to well-apposed struts in drug-eluting stents: In vivo assessment with optical coherence tomography

    NARCIS (Netherlands)

    J.L. Gutiérrez-Chico; E.S. Regar (Eveline); E. NüesC.H. (Eveline); T. Okamura (Takayuki); J.J. Wykrzykowska (Joanna); C. di Mario (Carlo); S.W. Windecker (Stephan); G.A. van Es (Gerrit Anne); P. Gobbens (Pierre); P. Jüni (Peter); P.W.J.C. Serruys (Patrick)

    2011-01-01

    textabstractBackground-Pathology studies on fatal cases of very late stent thrombosis have described incomplete neointimal coverage as common substrate, in some cases appearing at side-branch struts. Intravascular ultrasound studies have described the association between incomplete stent apposition

  13. L-Shaped Columellar Strut in East Asian Nasal Tip Plasty

    Directory of Open Access Journals (Sweden)

    Eun-Sang Dhong

    2013-09-01

    Full Text Available Background Nasal tip support is an essential consideration for rhinoplasty in East Asians.There are many techniques to improve tip projection, and among them, the columellar strut isthe most popular technique. However, the conventional design is less supportive for rotatingthe tip. The amount of harvestable septal cartilage is relatively small in East Asians. For anoptimal outcome, we propose an L-shaped design for applying the columellar strut.Methods To evaluate the anthropometric outcomes, the change in nasal tip projection andthe columella-labial angle were analyzed by comparing preoperative and postoperative photographs.The anthropometric study group consisted of 25 patients who underwent the sameoperative technique of an L-shaped strut graft using septal cartilage and were followed upfor more than 9 months.Results There were statistically significant differences between the preoperative and postoperativevalues in the nasal tip projection ratio and columella-labial angle. We did not observeany complications directly related to the L-shaped columellar strut in the anthropometricstudy group.Conclusions The L-shaped columellar strut has advantages not only in the controlling of tipprojection and rotation, but in that it needs a smaller amount of cartilage compared to theconventional septal extension graft. It can therefore be an alternative technique for nasal tipplasty when there is an insufficient amount of harvestable septal cartilage.

  14. Improvement and Application of the Softened Strut-and-Tie Model

    Science.gov (United States)

    Fan, Guoxi; Wang, Debin; Diao, Yuhong; Shang, Huaishuai; Tang, Xiaocheng; Sun, Hai

    2017-11-01

    Previous experimental researches indicate that reinforced concrete beam-column joints play an important role in the mechanical properties of moment resisting frame structures, so as to require proper design. The aims of this paper are to predict the joint carrying capacity and cracks development theoretically. Thus, a rational model needs to be developed. Based on the former considerations, the softened strut-and-tie model is selected to be introduced and analyzed. Four adjustments including modifications of the depth of the diagonal strut, the inclination angle of diagonal compression strut, the smeared stress of mild steel bars embedded in concrete, as well as the softening coefficient are made. After that, the carrying capacity of beam-column joint and cracks development are predicted using the improved softened strut-and-tie model. Based on the test results, it is not difficult to find that the improved softened strut-and-tie model can be used to predict the joint carrying capacity and cracks development with sufficient accuracy.

  15. A few insights into the nature of classical and quantum gravity via null-strut calculus

    International Nuclear Information System (INIS)

    Kheyfets, Arkady

    1989-01-01

    Null-strut calculus is a 3 + 1 formulation of standard Regge calculus, wherein the dynamics of 3-geometry is propagated in time along light rays, or 'null struts'. However, just as Regge calculus is a discrete and geometric tool for the description of Einstein's theory of gravitation, so too NSC offers itself as a discrete and geometric tool for the description of Einstein's spacetime as the dynamics of discrete spacelike 3-geometries in time, or discrete geometrodynamics. It has for its objectives to provide a discrete model of a 3 + 1 split of spacetime into space plus time, while in so doing to preserve and illuminate the geometric content of Einstein's theory of gravity. The feature of 'light-cone-produced duality' is central to null-strut calculus. This paper will capitalise on this feature, and will attempt to provide some insights into the nature of classical and quantum gravity. (Author)

  16. Hearing Gain with Tailor-made Polyethylene Strut in Total Stapedectomy

    Directory of Open Access Journals (Sweden)

    Kanthong Thongyai

    2017-01-01

    Full Text Available Objective: To study audiometric changes after total stapedectomy with tailor-made polyethylene strut. Methods: A retrospective analysis of preoperative and postoperative hearing results. One hundred and ninety- eight patients underwent total stapedectomy during 2009-2014. Stapedectomy was performed with tailor-made polyethylene strut prosthesis on vein or perichondrium graft over oval window. Changes of preoperative and postoperative pure tone average (PTA were calculated from 4 frequencies after stapedectomy. Results: Ninety percent success rate in the air-bone gap closure within 10 dB after stapedectomy. Conclusion: Tailor-made polyethylene strut prosthesis is a cheap and cost-effective prosthesis, which is an alternative option for surgeons instead of the commercial prosthesis.

  17. Cavitation in liquid cryogens. 4: Combined correlations for venturi, hydrofoil, ogives, and pumps

    Science.gov (United States)

    Hord, J.

    1974-01-01

    The results of a series of experimental and analytical cavitation studies are presented. Cross-correlation is performed of the developed cavity data for a venturi, a hydrofoil and three scaled ogives. The new correlating parameter, MTWO, improves data correlation for these stationary bodies and for pumping equipment. Existing techniques for predicting the cavitating performance of pumping machinery were extended to include variations in flow coefficient, cavitation parameter, and equipment geometry. The new predictive formulations hold promise as a design tool and universal method for correlating pumping machinery performance. Application of these predictive formulas requires prescribed cavitation test data or an independent method of estimating the cavitation parameter for each pump. The latter would permit prediction of performance without testing; potential methods for evaluating the cavitation parameter prior to testing are suggested.

  18. Numerical study on cavitating flow due to a hydrofoil near a free surface

    Directory of Open Access Journals (Sweden)

    Ping-Chen Wu

    2016-09-01

    Full Text Available A numerical strategy is proposed for a viscous uniform flow past a 2-D partially cavitating hydrofoil placed at a finite depth from the free surface. The flow was modeled by the Reynolds-averaged Navier–Stokes (RANS equations. A finite-volume method with the SIMPLE scheme and k-ε turbulence model were employed for computations. The “full cavitation model,” which included the effects of vaporization, noncondensible gases and compressibility, was incorporated in the computation of cavitating flow. The cavity shape and free surface were updated iteratively till a reasonable convergence was reached. As for the determination of the free surface, the VOF approach was adopted. The test cases show the accuracy and stability of our procedure to capture the cavitating flow near the free surface.

  19. Numerical simulation of cavitation erosion on a NACA0015 hydrofoil based on bubble collapse strength

    Science.gov (United States)

    Hidalgo, V.; Luo, X.; Escaler, X.; Huang, R.; Valencia, E.

    2015-12-01

    The prediction of erosion under unsteady cavitation is crucial to prevent damage in hydraulic machinery. The present investigation deals with the numerical simulation of erosive partial cavitation around a NACA0015 hydrofoil. The study presents the calculation of the bubble collapse strength, Sb, based on the bubble potential energy to identify the surface areas with highest risk of damage. The results are obtained with a numerical scheme assuming homogeneous mixture flow, implicit LES and Zwart cavitation model. The 3D unsteady flow simulation has been solved using OpenFOAM. Python language and OpenFOAM calculator (foamCalcEx) have been used to obtain and represent Sb. The obtained results clearly show the instants of erosive bubble collapse and the affected surface areas.

  20. Experimental investigation of the flow-induced vibration of hydrofoils in cavitating flows

    Science.gov (United States)

    Wang, Guoyu; Wu, Qin; Huang, Biao; Gao, Yuan

    2015-12-01

    The objective of this paper is to investigate the correlation between fluid induced vibration and unsteady cavitation behaviours. Experimental results are presented for a modified NACA66 hydrofoil, which is fixed at α=8°. The high-speed camera is synchronized with a single point Laser Doppler Vibrometer to analyze the transient cavitating flow structures and the corresponding structural vibration characteristics. The results showed that, with the decreasing of the cavitation number, the cavitating flows in a water tunnel display several types of cavitation patterns, such as incipient cavitation, sheet cavitation and cloud cavitation. The cavity shedding frequency reduces with the decrease of the cavitation number. As for the cloud cavitation regime, the trend of the vibration velocity goes up with the growth of the attached cavity, accompanied with small amplitude fluctuations. Then the collapse and shedding of the large-scale cloud cavities leads to substantial increase of the vibration velocity fluctuations.

  1. Study of unsteady cavitation on NACA66 hydrofoil using dynamic cubic nonlinear subgrid-scale model

    Directory of Open Access Journals (Sweden)

    Xianbei Huang

    2015-11-01

    Full Text Available In this article, we describe the use of a new dynamic cubic nonlinear model, a new nonlinear subgrid-scale model, for simulating the cavitating flow around an NACA66 series hydrofoil. For comparison, the dynamic Smagorinsky model is also used. It is found that the dynamic cubic nonlinear model can capture the turbulence spectrum, while the dynamic Smagorinsky model fails. Both models reproduce the cavity growth/destabilization cycle, but the results of the dynamic cubic nonlinear model are much smoother. The re-entrant jet is clearly captured by the models, and it is shown that the re-entrant jet cuts the cavity into two parts. In general, the dynamic cubic nonlinear model provides improvement over the dynamic Smagorinsky model for the calculation of cavitating flow.

  2. Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow

    Science.gov (United States)

    Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu

    2016-06-01

    In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.

  3. Drag reduction through wave-current interactions with a marine hydrofoil

    Science.gov (United States)

    Tully, Susan; Viola, Ignazio Maria; Ingram, David

    2015-11-01

    A hydrofoil exposed to oscillating flow experiences a reduction in drag due to the Knoller-Betz effect. This is experimentally identifiable by an increasingly inverted von Kármán wake and a corresponding thrust force on the foil. The rate of drag reduction, dependent on plunge amplitude and frequency, reduces with unsteady flow phenomena at higher reduced frequencies. For experimental ease, investigations of this effect have relied on actively plunging/pitching a foil within a steady current. However, one potential application is to drag reduction in high-speed ships adopting submerged foils. In this case the foil is travelling through wave-current induced oscillatory flow, resulting in an additional dynamic variation of hydrostatic pressure across the chord; a phenomena not fully addressed in previous experiments. Here we investigate the effects of this pressure gradient on drag reduction for a stationary foil in combined waves and current, through a combination of force measurements and particle image velocimetry.

  4. Lagrangian-based investigation of the transient flow structures around a pitching hydrofoil

    Science.gov (United States)

    Wu, Qin; Huang, Biao; Wang, Guoyu

    2016-02-01

    The objective of this paper is to address the transient flow structures around a pitching hydrofoil by combining physical and numerical studies. In order to predict the dynamic behavior of the flow structure effectively, the Lagrangian coherent structures (LCS) defined by the ridges of the finite-time Lyapunov exponent (FTLE) are utilized under the framework of Navier-Stokes flow computations. In the numerical simulations, the k-ω shear stress transport (SST) turbulence model, coupled with a two-equation γ {-Re}_θ transition model, is used for the turbulence closure. Results are presented for a NACA66 hydrofoil undergoing slowly and rapidly pitching motions from 0° to 15° then back to 0° at a moderate Reynolds number Re=7.5× 105. The results reveal that the transient flow structures can be observed by the LCS method. For the slowly pitching case, it consists of five stages: quasi-steady and laminar, transition from laminar to turbulent, vortex development, large-scale vortex shedding, and reverting to laminar. The observation of LCS and Lagrangian particle tracers elucidates that the trailing edge vortex is nearly attached and stable during the vortex development stage and the interaction between the leading and trailing edge vortex caused by the adverse pressure gradient forces the vortexes to shed downstream during the large-scale vortex shedding stage, which corresponds to obvious fluctuations of the hydrodynamic response. For the rapidly pitching case, the inflection is hardly to be observed and the stall is delayed. The vortex formation, interaction, and shedding occurred once instead of being repeated three times, which is responsible for just one fluctuation in the hydrodynamic characteristics. The numerical results also show that the FTLE field has the potential to identify the transient flows, and the LCS can represent the divergence extent of infinite neighboring particles and capture the interface of the vortex region.

  5. Unsteady Lift and Drag Characteristics of Cavitating Clark Y-11.7% Hydrofoil

    International Nuclear Information System (INIS)

    Watanabe, S; Yamaoka, W; Furukawa, A

    2014-01-01

    Unsteady cavitating flow and lift/drag characteristics of a two-dimensional Clark Y- 11.7% hydrofoil are experimentally investigated in order to clarify the relation between the lift drop mechanism and the unsteady cavity behavior. Unsteady lift and drag forces are measured by strain gauges attached on the cantilever supporting the hydrofoil, assuming the negligible bending moment. In combination with the above force measurements, the cavitating flow is filmed from both top and side simultaneously using two high speed video cameras. It is clearly observed that, in larger attack angle conditions (4-10 degrees), the time-averaged lift coefficient slightly increases from that in the non-cavitating condition. After the slight increase, the lift gradually decreases then its steep decrease starts to occur. On the other hand, in a small attack angle case (2 degrees), little increase of the lift is observed, and just after that the sudden lift drop occurs. From the instantaneous frequency spectra of the lift, the followings are found; during the slight increase of the lift, the cavity is being a partial cavity in almost steady state, but during the subsequent gradual lift decrease, the partial cavity oscillates with cloud cavity shedding, in other word, the partial cavity oscillation occurs, whose frequency decreases with the growth of the cavity. During the sudden lift drop, the low frequency transitional cavity oscillation occurs, in which the cavity dramatically changes between partial and super cavities. The typical events of cavity behavior during the cavitation instabilities are found to be able to be related with the behavior of instantaneous lift force and pressure

  6. A fractured inferior vena cava filter strut migrating to the left pulmonary artery

    Directory of Open Access Journals (Sweden)

    Tamer Hudali

    2015-01-01

    Full Text Available Inferior vena cava filters are increasingly used in patients with recurrent venous thromboembolism who are contraindicated to anticoagulation. Migration of a broken strut to the pulmonary artery is a very rare complication of these filters. We report the case of an 83-year-old female who experienced this complication with the migratory strut remaining in the same position for years. This case provides evidence that such filters probably have higher rates of complications than what has been thought that remain asymptomatic. The indications and the management of complications of such devices need to be studied further.

  7. Numerical evaluation of cavitation shedding structure around 3D Hydrofoil: Comparison of PANS, LES and RANS results with experiments

    Science.gov (United States)

    Ji, B.; Peng, X. X.; Long, X. P.; Luo, X. W.; Wu, Y. L.

    2015-12-01

    Results of cavitating turbulent flow simulation around a twisted hydrofoil were presented in the paper using the Partially-Averaged Navier-Stokes (PANS) method (Ji et al. 2013a), Large-Eddy Simulation (LES) (Ji et al. 2013b) and Reynolds-Averaged Navier-Stokes (RANS). The results are compared with available experimental data (Foeth 2008). The PANS and LES reasonably reproduce the cavitation shedding patterns around the twisted hydrofoil with primary and secondary shedding, while the RANS model fails to simulate the unsteady cavitation shedding phenomenon and yields an almost steady flow with a constant cavity shape and vapor volume. Besides, it is noted that the predicted shedding vapor cavity by PANS is more turbulent and the shedding vortex is stronger than that by LES, which is more consistent with experimental photos.

  8. Effect of different wall injection schemes on the flow-field of hydrogen fuelled strut-based scramjet combustor

    Science.gov (United States)

    Choubey, Gautam; Pandey, K. M.

    2018-04-01

    The multi-strut injector is one of the most favourable perspectives for the mixing improvement in between the hydrogen and the high-speed air, and its parametric investigation has drawn an increasing attention among the researchers. Hence the flow-field aspects of a particular multi-strut based scramjet combustor have been investigated numerically with the addition of four wall injectors and at the same time, the influence of combination of different strut as well as wall injector scheme on the performance of multi-strut scramjet engine has also been explored. Moreover, the current computational approach has been validated against the experimental data present in the open literature in case of single strut scramjet engine. The attained results reveal that the collaboration of multi-strut along with 2 wall injectors' improves the efficiency of scramjet as compared to other multi-strut + wall injection scheme as this combination achieve higher penetration height which will boost to a wider temperature and robust combustion area adjacent to the wall. Again, the appearance of extra H2 in the separated flow region precisely ahead of the wall injection region is mainly reasonable for the abrupt decrease in the mixing as well combustion efficiency plot in all the multi-strut + wall injection strategy.

  9. Identification of Large Scale Structures in the Wake of Cavitating Hydrofoils Using LES and TR-PIV

    Science.gov (United States)

    Wosnik, Martin

    2005-11-01

    Large-scale three-dimensional cavitating structures exist in the wake of two-dimensional hydrofoils, as a result of sheet/cloud cavitation. This type of cavitation produces unsteady lift on most hydrofoils -- including the NACA 0015 studied here -- but is sufficiently periodic to have potential for control. A Large Eddy Simulation (LES) based on a virtual single-phase, fully compressible cavitation model captures the complex dynamical features of this highly unsteady cavitating flow well. The LES results are compared to Time-Resolved Particle Image Velocimetry (TR-PIV, recorded at 2000Hz) in the region immediately downstream of the hydrofoil, with particular attention to the predicted vortex shedding mechanisms. With a careful choice of photometric parameters and adaptive masking, the large, vortical, cavitating structures are identified quantitatively. The existence of the primary vortex pair predicted by the LES is confirmed by TR-PIV. This vortex pair produces large cross-stream velocities, with a general ejection direction of 3/4 π to the free stream. However, the shedding pattern as recorded with TR-PIV is not nearly as regular as in the LES, due to the limited number of spanwise grid points in the simulation and the highly three- dimensional nature of cloud cavitation shedding in the experiment.

  10. Optical coherence tomography at follow-up after percutaneous coronary intervention: relationship between procedural dissections, stent strut malapposition and stent healing

    DEFF Research Database (Denmark)

    Radu, Maria; Jørgensen, Erik; Kelbæk, Henning

    2011-01-01

    To analyse the relationship between strut apposition as visualised with optical coherence tomography (OCT) at follow-up and clinical and procedural characteristics at stent implantation, and to examine the relationship between strut apposition and stent healing.......To analyse the relationship between strut apposition as visualised with optical coherence tomography (OCT) at follow-up and clinical and procedural characteristics at stent implantation, and to examine the relationship between strut apposition and stent healing....

  11. Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

    Science.gov (United States)

    Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

    2011-01-01

    An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point…

  12. Self-oscillations of aircraft landing gear shock-strut at considerable non-linear friction

    Directory of Open Access Journals (Sweden)

    Б.М. Шифрин

    2004-01-01

    Full Text Available  The report considers self-oscillations at ε >1. The previous works were dedicated to the elastic frictional L.G. shock strut oscillations, the mathematical model of which is a non-linear differential equation with low ε parameter of its right-hand part.

  13. Absorbable Plate as a Perpendicular Strut for Acute Saddle Nose Deformities

    Directory of Open Access Journals (Sweden)

    Jong Gyu Kim

    2012-03-01

    Full Text Available BackgroundNasal pyramid fractures accompanied by saddle nose deformities are not easily corrected by closed reduction. We used an absorbable plate as a perpendicular strut to support the collapsed "keystone area" and obtained good results.MethodsBetween September 2008 and June 2011, 18 patients who had nasal pyramid fractures with saddle nose deformities underwent surgery. Pre- and postoperative facial computed tomographic images and photographs were taken to estimate outcomes. The operative technique included the mucoperichondrial dissection of the nasal septum, insertion of an absorbable plate prepared to an appropriate length to support the "keystone area", and fixation of the absorbable plate strut to the cartilaginous septum.ResultsFunctional and esthetic outcomes were satisfactory in all patients. Eleven patients assessed the postoperative appearance of the external nose as 'markedly improved' and 7 patients as 'improved'. The 5 surgeons scored the results as a mean of 4.5 on a 5-point scale.ConclusionsThe use of an absorbable plate as a perpendicular strut requires no additional procedures because the plate is gradually absorbed. The mechanical strength provided by a buttress between the "keystone area" and the maxillary crest lasts for a long time before the strut is absorbed.

  14. Microscale Diffusion Measurements and Simulation of a Scaffold with a Permeable Strut

    Directory of Open Access Journals (Sweden)

    Songwan Jin

    2013-10-01

    Full Text Available Electrospun nanofibrous structures provide good performance to scaffolds in tissue engineering. We measured the local diffusion coefficients of 3-kDa FITC-dextran in line patterns of electrospun nanofibrous structures fabricated by the direct-write electrospinning (DWES technique using the fluorescence recovery after photobleaching (FRAP method. No significant differences were detected between DWES line patterns fabricated with polymer supplied at flow rates of 0.1 and 0.5 mL/h. The oxygen diffusion coefficients of samples were estimated to be ~92%–94% of the oxygen diffusion coefficient in water based on the measured diffusion coefficient of 3-kDa FITC-dextran. We also simulated cell growth and distribution within spatially patterned scaffolds with struts consisting of either oxygen-permeable or non-permeable material. The permeable strut scaffolds exhibited enhanced cell growth. Saturated depths at which cells could grow to confluence were 15% deeper for the permeable strut scaffolds than for the non-permeable strut scaffold.

  15. Simulation of tandem hydrofoils by finite volume method with moving grid system; Henkei koshi wo tsukatta yugen taisekiho ni yoru tandem suichuyoku no simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kawashima, H. [Ship Research Inst., Tokyo (Japan); Miyata, H. [The University of Tokyo, Tokyo (Japan). Faculty of Engineering

    1996-12-31

    With an objective to clarify possibility of application of time-advancing calculated fluid dynamic (CFD) simulation by using a finite volume method with moving grid system, a simulation was performed on motion of a ship with hydrofoils including the control system therein. The simulation consists of a method that couples a moving grid system technology, an equation of motion, and the control system. Complex interactions between wings and with free surface may be considered automatically by directly deriving fluid force from a flow field by using the CFD. In addition, two-dimensional flows around tandem hydrofoils were calculated to solve the motion problem within a vertical plane. As a result, the following results were obtained: a finite volume method using a dynamic moving grid system method was applied to problems in non-steady tandem hydrofoils to show its usefulness; a method that couples the CFD with the equation of motion was applied to the control problems in the tandem hydrofoils to show possibility of a new technology for simulating motions; and a simulation that considers such wing interference as wave creation, discharged vortices, and associated flows was shown useful to understand characteristics of the tandem hydrofoils. 13 refs., 14 figs.

  16. Sagittal Alignment of a Strut Graft Affects Graft Subsidence and Clinical Outcomes of Anterior Cervical Corpectomy and Fusion.

    Science.gov (United States)

    Yamauchi, Koun; Fushimi, Kazunari; Miyamoto, Kei; Hioki, Akira; Shimizu, Katsuji; Akiyama, Haruhiko

    2017-10-01

    Retrospective study. The purpose of this study was to investigate the influence of sagittal alignment of the strut graft on graft subsidence and clinical outcomes after anterior cervical corpectomy and fusion (ACCF). ACCF is a common technique for the treatment of various cervical pathologies. Although graft subsidence sometimes occurs after ACCF, it is one cause for poor clinical results. Malalignment of the strut graft is probably one of the factors associated with graft subsidence. However, to the best of our knowledge, no prior reports have demonstrated correlations between the alignment of the strut graft and clinical outcomes. We evaluated 56 patients (33 men and 23 women; mean age, 59 years; range, 33-84 years; 45 with cervical spondylotic myelopathy and 11 with ossification of the posterior longitudinal ligament) who underwent one- or two-level ACCF with an autogenous fibular strut graft and anterior plating. The Japanese Orthopaedic Association (JOA) score recovery ratio for cervical spondylotic myelopathy was used to evaluate clinical outcomes. The JOA score and lateral radiograms were evaluated 1 week and 1 year postoperatively. Patients were divided into two groups (a straight group [group I] and an oblique group [group Z]) based on radiographic assessment of the sagittal alignment of the strut graft. Group I showed a significantly greater JOA score recovery ratio ( p subsidence than group Z ( p subsidence after ACCF. In contrast, an oblique strut graft can lead to significantly increased strut graft subsidence and poor clinical results.

  17. Cavitation dynamics on a NACA0015 hydrofoil using time resolved X-ray densitometry

    Science.gov (United States)

    Ganesh, Harish; Wu, Juliana; Ceccio, Steven

    2015-11-01

    Recent investigations of partial cavitation have shown that the transition from stable to shedding cavities can be related to the presence of both propagating bubbly shocks and re-entrant liquid jets originating in the cavity closure region. In the present study, formation of sheet cavitation and its transition to periodically shedding cavities is studied on a NACA0015 hydrofoil in a recirculating water tunnel at different attack angles. Using high-speed videos and time resolved X-ray densitometry, the instantaneous void fraction flow fields are obtained to identify the principal mechanism responsible for transition from stable to shedding cavities over a range of attack angles and cavitation numbers. The role of attack angle is of particular interest, since is it related to the pressure gradient at cavity enclosure, and can lead to the formation of stronger reentrant flows. The relative importance of reentrant liquid flow and bubbly shock wave propagation will be discussed This work is supported by Office of Naval Research.

  18. Effect of the Endwall Motion on a Hydrofoil with Various Widths of Clearance

    Science.gov (United States)

    Guo, Q.; Zhou, L. J.; Wang, Z. W.; Xiao, R. F.; Yao, Z. F.

    2016-11-01

    This paper is devoted to evaluate the effects of the relative motion between the blade tip and casing wall with different widths of gap. The steady non-cavitating simulations around a sharp tip hydrofoil in tunnel with a moving endwall are implemented and another calculation with the stationary wall is carried out as a contrast. Overall, the endwall motion moves the trajectory of the tip leakage vortex (TLV) much closer to the foil but brings small effect on the streamwise vorticity and the minimum pressure in the TLV. The influence of the gap width is taken into account with the normalized gap width withinτ=0.02∼0.4. The flow features on a cross section inside the gap suggest that the endwall motion causes a little lower leakage flow rate and velocity in pitchwise direction. Inside a wider gap like τ=0.2, the pressure of the tip separation vortex (TSV) is a little higher and the direction of the velocity gradient for the streamwise flow is changed under the effect of the moving wall. The foil loading characteristics are revealed by the lift and drag coefficients which are a slightly lower under the effect of the endwall motion.

  19. Bubbly Shock Waves in Multi-modal Cavitation Shedding Dynamics on a NACA0015 Hydrofoil

    Science.gov (United States)

    Wu, Juliana; Ganesh, Harish; Ceccio, Steven

    2017-11-01

    Cavitation dynamics on the NACA0015 hydrofoil is known to be multi-modal with abrupt changes in Strouhal number with change in cavitation number at several attack angles. In one of our previous studies we found that cavity collapse can arrest cavity growth abruptly thereby altering the shedding frequency. In addition, occurrence of propagating bubbly shocks that cause leading edge pinch-off is another process that can have an effect on changing the dynamics. In the current study, we obtain time-resolved X-ray densitometry measurements on larger model scale to resolve the processes involved in cloud collapse induced growth-arrest. Furthermore, time-resolved void fraction flow fields measurements obtained using X-ray densitometry, synchronized both with acoustic noise measurements using a hydrophone and dynamic pressure measurements from flush mounted pressure transducers on the model, are used to observe the role of shock waves in causing the abrupt change in cavitation dynamics. Sponsored by Office of Naval Research.

  20. Pitch and heave dynamics of an elastically-mounted cyber-physical hydrofoil

    Science.gov (United States)

    Su, Yunxing; Onoue, Kyohei; Miller, Michael; Breuer, Kenneth

    2017-11-01

    The energy harvesting performance of an elastically-mounted hydrofoil (chord, c, span, s) subject to a prescribed pitching motion is studied using a cyber-physical force-feedback control system. We vary the mass, m, the frequency of the pitching motion, ω, the parameters of the elastic support (stiffness, k and damping, b) and the Reynolds number, Re . The extracted energy is obtained from measured heave force and velocity, Fẏ . The ratio between the pitching frequency and the natural frequency of the system, ω /√{ k / m } , and the damping coefficient, b / (0.5 ρUsc) , are found to play a major role. In particular, the maximum power output is achieved at a frequency ratio of 1, which corresponds to an optimal phase difference of 90° between the driven pitch and passive heave motions. At the resonance condition, the damping coefficient defines the heaving amplitude, H, and thus the width of the wake and the Strouhal number, St = fH / U . The power coefficient, Cp = , reaches a maximum of 0.65 at a damping coefficient around 1.5, regardless of the Reynolds number (Re = 20,000 - 55,000). The contribution of the pitch component to power extraction is found to be small (< 10% of the heave component). This work is funded by ARPA-e.

  1. Numerical Simulation of Transient Flows around a 3D Pitching Hydrofoil

    Directory of Open Access Journals (Sweden)

    Qin Wu

    2015-02-01

    Full Text Available The objective of this paper is to investigate the hydrodynamic characteristics of the transient flows around a 3D pitching hydrofoil via numerical studies, where the effects of tunnel wall boundary layer and gap flows are considered. Simulations are performed using an unsteady Reynolds Average Navier-Stokes solver and the k-ω SST turbulence model, coupled with a two-equation γ-Reθ transition model. Hydrodynamic forces and flow structures are compared to the results with the equivalent 2D computations. During the upward pitching stage, the transition phenomenon is accurately captured by both the 2D and 3D simulations. The slightly lower lift and suction side loading coefficients predicted by the 3D simulation are due to the pressure effects caused by the tip gap flow. During the dynamic stall stage, the 2D case exhibits a clear overshoot on the hydrodynamic force coefficients and the 3D simulation results better agree with the experimental results. During the downward pitching stage, the flow transitions back to laminar. As for the effect of gap flow and the wall boundary condition, the gap flow causes disturbances to the formation and development of the vortex structures, resulting in the complex distribution of the three-dimensional streamlines and the particle path.

  2. RANS SIMULATION OF HYDROFOIL EFFECTS ON HYDRODYNAMIC COEFFICIENTS OF A PLANING CATAMARAN

    Directory of Open Access Journals (Sweden)

    Amin Najafi

    2016-03-01

    Full Text Available Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using RANS method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly, and requires meticulous laboratory equipment; therefore, utilizing numerical methods and developing a virtual laboratory seems highly efficient. In the present study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s (1992 experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency independent especially at high frequencies.

  3. A study of wakes trailing a cavitating and ventilated NACA 0015 hydrofoil

    Science.gov (United States)

    Time, Rune W.; Kjeldsen, Morten; Arndt, Roger E.

    2007-11-01

    In certain types of pumping applications oscillations are induced by operation with liquids containing immiscible gas in solution. To understand the physics of this process, a series of tests with a ventilated 2D NACA 0015 hydrofoil were performed in the water tunnel at the St. Anthony Falls Laboratory of the University of Minnesota. A relation between the cavitation index for both ventilated and naturally cavitating flows has been established. This allows direct comparison between the two types of two-phase flows. A good correspondence is found when comparing drag, lift break-down and lift/drag oscillation amplitudes for a properly defined cavitation index. A careful analysis is required to compare the spectral content of oscillatory flow. This study concentrates on analyzing wake structure for selected ventilation rates and cavitation numbers. The wake structure is mapped by conventional PIV techniques. Results for high cavitation/ventilation number flows are presented. Since conventional PIV represents snap shots of a time evolving phenomenon special care needs to be taken for the analysis.

  4. The Transport of Mass, Energy, and Entropy in Cryogenic Support Struts for Engineering Design

    Science.gov (United States)

    Elchert, J. P.

    2012-01-01

    Engineers working to understand and reduce cryogenic boil-off must solve a. variety of transport problems. An important class of nonlinear problems involves the thermal and mechanical design of cryogenic struts. These classic problems are scattered about the literature and typically require too many resources to obtain. So, to save time for practicing engineers, the author presents this essay. Herein, a variety of new, old, and revisited analytical and finite difference solutions of the thermal problem are covered in this essay, along with commentary on approach and assumptions, This includes a few thermal radiation and conduction combined mode solution with a discussion on insulation, optimum emissivity, and geometrical phenomenon. Solutions to cooling and heat interception problems are also presented, including a discussion of the entropy generation. And the literature on the combined mechanical and thermal design of cryogenic support struts is reviewed with an introduction to the associated numerical methods.

  5. Active strut placement using integer programming for the CSI Revolutionary Model

    Science.gov (United States)

    Padula, Sharon L.; Sandridge, Chris A.

    1992-01-01

    A method for determining the most effective locations for active struts on large space structures is developed and tested on the NASA CSI Evolutionary Model. Depending on the choice of weighting factors, the method can be used to maximize the maximum modal damping ratio or decay rate, or to maximize a mission-oriented measure of performance. Placement of 8, 16, and 32 active struts out of 1507 candidate truss elements is demonstrated. Preliminary estimates of damping enhancement are reported pending refined structural models and dynamic test results. The method can handle complicated FEM models wih a large number of truss elements and many target modes. It can treat each mode equally or it can emphasize the importance of selected modes. The method can eliminate some combinations of actuator locations based on topological constraints.

  6. Investigations on the Influence of the In-Stream Pylon and Strut on the Performance of a Scramjet Combustor

    Directory of Open Access Journals (Sweden)

    Hao Ouyang

    2014-01-01

    Full Text Available The influence of the in-stream pylon and strut on the performance of scramjet combustor was experimentally and numerically investigated. The experiments were conducted with a direct-connect supersonic model combustor equipped with multiple cavities. The entrance parameter of combustor corresponds to scramjet flight Mach number 4.0 with a total temperature of 947 K. The research results show that, compared with the scramjet combustor without pylon and strut, the wall pressure and the thrust of the scramjet increase due to the improvement of mixing and combustion effect due to the pylon and strut. The total pressure loss caused by the strut is considerable whereas pylon influence is slight.

  7. Cortical Strut Allograft Support of Modular Femoral Junctions During Revision Total Hip Arthroplasty.

    Science.gov (United States)

    Lim, Chin Tat; Amanatullah, Derek F; Huddleston, James I; Hwang, Katherine L; Maloney, William J; Goodman, Stuart B

    2017-05-01

    There is risk of junction failure when using modular femoral stems for revision total hip arthroplasty (THA), especially with loss of bone stock in the proximal femur. Using a cortical strut allograft may provide additional support of a modular femoral construct in revision THA. We reviewed prospectively gathered clinical and radiographic data for 28 revision THAs performed from 2004 to 2014 using cementless modular femoral components with cortical strut allograft applied to supplement proximal femoral bone loss: 5 (18%) were fluted taper designs and 23 (82%) were porous cylindrical designs All the patients had a Paprosky grade IIIA or greater femoral defect. The mean follow-up was 5.4 ± 3.9 years. The Harris Hip Scores improved from 26 ± 10 points preoperatively to 71 ± 10 points at final follow-up (P hips) of all revision or conversion THAs were in place at final follow-up. Three (11%) patients underwent reoperations, 2 for infection and 1 for periprosthetic fracture. There was no statistical significant change in femoral component alignment (P = .161) at final follow-up. Mean subsidence was 1.8 ± 1.3 mm at final follow-up. Femoral diameter increased from initial postoperative imaging to final follow-up imaging by a mean of 9.1 ± 5.1 mm (P hips (96%) achieved union between the cortical strut allograft and the host femur. The use of a modular femoral stem in a compromised femur with a supplementary cortical strut allgraft is safe and provides satisfactory clinical and radiological outcomes. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. The effect of struts on the radiation diagram of Cassegrain antennas

    International Nuclear Information System (INIS)

    Henriques, L.M.D.

    1981-09-01

    This work presents a study on the effect of subreflector support members of Cassegrain antennas using the theory of scattering by cylinders structures. Expression for the surface current densities and arbitrary cross sections cylinders are developed, and the components for the scattered field are obtained. Using these results we analyse the effect of the struts on the gain reduction, and the rise of maximum side-lobe level. The final results obtained are then compared to other approximate theories. (author)

  9. The Effect of the Nature of Surfaces on Resistance as Tested on Struts

    Science.gov (United States)

    Wieselsberger, Ing C

    1921-01-01

    The chief concern was to measure the variations of resistance brought about by the nature of the surface of the struts. The struts were spanned with aviation linen, and then covered with one coat of varnish. The top surface was not perfectly smooth after this treatment, being slightly rough owing to the threads and raised fibers of the fabric. The results of the measurements of the surfaces are shown by the dotted lines of the curves plotted in several figures. The resistance is given in terms of the characteristic value. Next, the surface was altered by the removal of any roughness on it by means of filing with sandpaper. The measurements of surfaces thus treated gave values represented by extended lines. The increase of resistance with increasing characteristic value, more or less marked in the first series of measurements, was no longer observable. Resistance always decreases with the increase of characteristic value, excepting in the case of strut 7, which shows a slight tendency to rise again. The reasons for this phenomenon have not yet been fully explained.

  10. Numerical prediction of cavitating flow around a hydrofoil using pans and improved shear stress transport k-omega model

    Directory of Open Access Journals (Sweden)

    Zhang De-Sheng

    2015-01-01

    Full Text Available The prediction accuracies of partially-averaged Navier-Stokes model and improved shear stress transport k-ω turbulence model for simulating the unsteady cavitating flow around the hydrofoil were discussed in this paper. Numerical results show that the two turbulence models can effectively reproduce the cavitation evolution process. The numerical prediction for the cycle time of cavitation inception, development, detachment, and collapse agrees well with the experimental data. It is found that the vortex pair induced by the interaction between the re-entrant jet and mainstream is responsible for the instability of the cavitation shedding flow.

  11. Frequency characteristics of liquid hydrogen cavitating flow over a NACA0015 hydrofoil

    Science.gov (United States)

    Zhu, Jiakai; Wang, Shunhao; Qiu, Limin; Zhi, Xiaoqin; Zhang, Xiaobin

    2018-03-01

    Large eddy simulation on unsteady cavitating flow of liquid hydrogen over a three-dimensional NACA0015 hydrofoil with the attack angle (α) of 6° are carried out to investigate the dynamic features of cavity with the existence of thermal effects. The numerical model considers the compressibility of both liquid and vapor phase, and is validated by comparing the results with the available experimental data. Special emphasis is put on analyzing the frequency characteristics of cavitation cloud. Strouhal number (St) is plotted against σ/2α (σ is cavitation number), and the water cavitation data reported by Andrt et al. are also used as a reference. It is found that the St number for LH2 cavitation is much smaller than the water, in which the thermal effects are generally not considered, at the same σ/2α value when it is greater than about 2.0, while it returns to the same level as water when σ/2α decreases to below 2.0. The reason is primarily ascribed to the thermal effects, and the detailed explanations are given based on the recognitions that the shedding mechanism of cavitation clouds is predominated by the combined action of the vortex flow and thermal effects. While, when σ/2α decreases to a critical value, the relative effect of the thermal effects on the cavitation dynamics is greatly weakened compared with the mechanism due to the vortex flow, like those in isothermal cavitation flow in traditional fluids. The results provide a deeper understanding of the cryogenic fluid cavitation flow.

  12. Vortex structure analysis of unsteady cloud cavitating flows around a hydrofoil

    Science.gov (United States)

    Zhao, Yu; Wang, Guoyu; Huang, Biao

    2016-01-01

    In this paper, time dependent vortex structures are numerically analyzed for both noncavitating and cloud cavitating flows around a Clark-Y hydrofoil with angle of attack α = 8∘ at a moderate Reynolds number, Re = 7 × 105. The numerical simulations are performed using a transport equation-based cavitation model and the large eddy simulation (LES) approach with a classical eddy viscosity subgrid scale (SGS) model. Compared with experimental results, present numerical predictions are capable of capturing the initiation of cavity, growth toward the trailing edge and subsequent shedding process. Results indicate that in noncavitating conditions, the trailing edge vortex and induced positive vortex shed periodically into the wake region to form the vortex street. In cloud cavitating conditions, interrelations between cavity and vortex induce different vortex dynamics at different cavity developing stages. (i) As attached cavity grows, vorticity production is greatly enhanced by the favorable pressure gradient at the leading edge. The trailing edge flow does not have a direct impact on the attached cavity expansion process. Furthermore, the liquid-vapor interface that moves toward the trailing edge enhances the vorticity in the attached cavity closure region. (ii) When the stable attached sheet cavity grows to its maximum length, the accumulation process of vorticity is eventually interrupted by the formation of the re-entrant jet. Re-entrant jet’s moving upstream leads to a higher spreading rate of the attached cavity and the formation of a large coherent structure inside the attached cavity. Moreover, the wavy/bubbly cavity interface enhances the vorticity near the trailing edge. (iii) As the attached sheet cavity breaks up, this large vortex structure converts toward the trailing edge region, which will eventually couple with a trailing edge vortex shedding from the lower surface to form the cloud cavity. The breakup of the stable attached cavity is the main

  13. Transient cavitating vortical flows around a hydrofoil using k-ω partially averaged Navier-Stokes model

    Science.gov (United States)

    Luo, Xianwu; Huang, Renfang; Ji, Bin

    2016-01-01

    For accurate simulations of wall-bounded turbulent cavitating flows, the present paper proposed a partially averaged Navier-Stokes (PANS) method derived from the k-ω turbulence model. Transient cavitating vortical flows around a NACA66 hydrofoil were simulated by using the k-ω PANS model with various filter parameters (fk = 0.2, 0.5 and 1, while fω = 1/fk) and a mass transfer cavitation model based on the Rayleigh-Plesset equation. Compared with the available experimental data, the k-ω PANS model with fk = 0.2 can accurately reproduce the cavitation evolution with more complicated structures due to the reduction in the predicted eddy viscosity. Further analyses, using the vorticity transport equation, indicate that the transition of cavitation structure from two dimension to three dimension is associated with strong vortex-cavitation interaction, where vortex stretching and dilation may play a major role. Therefore, the k-ω PANS model with the filter parameter of fk = 0.2 is an effective method to numerically predict the transient cavitating vortical flows around hydrofoils. The results obtained in this paper are helpful to provide a physical insight into the mechanisms of cavitation shedding dynamics.

  14. STRESS-DEFORMED STATE OF A STRUT-FRAMED CRANE GIRDER

    Directory of Open Access Journals (Sweden)

    Kh. M. Muselemov

    2017-01-01

    Full Text Available Objectives. The aim of the present work is to study the influence of design parameters on the stress-deformed state of a sprengel crane girder; to compile the tables and corresponding graphs illustrating changes in internal force factors in the characteristic cross-sections of the system elements under consideration. The article describes the study of the stress-deformed state (SDS of a metal strut-framed crane girder.Methods. Numerical methods of analysis based on the use of the Green's function are used during solving this problem. A dimensionless parameter is introduced, depending on which the tables and graphs are constructed. According to the known algorithm, the calculations of internal force factors in the sections of the considered construction are performed.Results. Depending on the dimensionless parameter characterising the geometry and physical features of the system, tables of bending moments and transverse forces are compiled. According to these tables, the appropriate graphs are plotted in order to choose easily the optimal design parameters.Conclusion. The dependence of the moments and transverse forces on the dimensionless parameter k was found, the corresponding graphs were plotted and the metal costs for the girders were calculated. The minimum values of the moments and transverse forces are established to take place when the dimensionless parameter k values are close to zero. The most economical was a strut-framed crane girder having k = 0.0001. The most uneconomical had k = 0.05 and k =∞. Eventually, the sprengel girders were found to be more profitable as compared to conventional crane girders. In the examples considered in the article, the metal savings amounted up to 14%. The presented methodology allows the calculation and designing of strut-framed crane girders with two racks to be carried out. 

  15. Experimental study of cone-struts and cavity flameholders in a kerosene-fueled round scramjet combustor

    Science.gov (United States)

    Zhang, Dongqing; Song, Wenyan

    2017-10-01

    Experimental investigations of liquid kerosene ignition and flameholding in a round supersonic combustor are presented. Three kinds of flameholders, a cone-struts structure, a cavity and the combination of the both, are studied for the kerosene ignition and flameholding. Results show that ignition and flameholding cannot be achieved by using the sole cone-struts flameholder, although flames are observed at the combustor outlet. The ignition and flameholding are achieved in a narrow range of equivalence ratios by using the cavity flameholder. This range is widened by employing the combination of the cone-struts and the cavity flameholders. It is observed that the back pressure disrupts the isolator entrance flow slightly by using the larger cone-struts (CR = 0.261). However, it does not happen when the smaller cone-struts (CR = 0.221) is employed. Then a characteristic air mass flow rate in the round combustor is redefined to calculate a modified Damkohler number that correlates the nonpremixed flame stability limits. The correlations are in good agreements with the experimental results.

  16. Investigation of passenger car using Macpherson strut for suspension system pt.1: Vehicle behaviour variation of time response

    Directory of Open Access Journals (Sweden)

    Ali Tanti

    2017-01-01

    Full Text Available It has been decade, researchers has been conducting researches on the topics concerning vehicle behavior. Suspension system, driving maneuver and road profile are the particular parameters in order to achieve the aim in vehicle behavior understanding. This paper combined these three criteria by means of using a passenger car equipped with MacPherson strut front suspension undergoes different driving behavior. The objective of this paper is to study the effect of passenger car equipped with MacPherson strut front suspension system vehicle behavior based on different driving maneuvers. For this study, Proton Persona Sedan 1.6 Manual Transmission Base Line was used to investigate the MacPherson strut suspension system. Data were collected using DEWESoft Software. As the velocity and direction varies with time, the vehicle response subjected to stationary excitation, while it varies with different velocity and different type of road. Acceleration, deceleration and bumpy test the suspension mechanism support the weight of the vehicle yet to cushion bumps and holes in the road. It can be concluded that the MacPherson strut suspension system has an effect on not only vehicle behavior but also comfort ride. These findings provide the following insights for future research in suspension vibration in order to optimize the performance of the MacPherson strut suspension system.

  17. Oscillating Hydrofoils for Tidal Energy Extraction: Experiments, Simulations and Salt Water Field Tests

    Science.gov (United States)

    Mandre, S.; Franck, J.; Breuer, K.; Fawzi, A.; Cardona, J.; Miller, M. J.; Su, Y.; Medina, A.; Loera Loera, C.; Junquera, E.; Simeski, F.; Volkmann, K.; Lorick, R.; Cowles, S.; Luiz Rocha Ribeiro, B.; Winckler, S.; Derecktor, T.

    2015-12-01

    We report on the development of a new oscillating hydrofoil technology for tidal flow energy harvesting. A series of flume experiments and computational fluid dynamics (CFD) simulations have been performed over a wide range of frequencies, f, heave amplitudes, h, and pitch angles, θ. The flume model has chord, c, of 10 cm and aspect ratio of 4.5. Mechanical power extracted is estimated from the foil trajectory, force and moment data. A robust real-time algorithm has been developed to identify the kinematics that optimizes either the total power or the Betz efficiency. Optimal efficiency is found when the pitch and heave cycles are 90 degrees out of phase, oscillating at a reduced frequency, fc/U, of approximately 0.15, with a heave amplitude of approximately 1c, and a pitch amplitude of θ=75 degrees. The high pitch amplitude and sharp leading edge of the foil generates a transient leading edge vortex on the suction side of the foil, significantly enhancing the vertical force and power. The optimal frequency ensures that the vortex generation and ultimate shedding maximize these unsteady hydrodynamic effects. The flume results, including power and efficiency, as well as flow visualization and particle image velocimetry (PIV) exhibit excellent agreement with the CFD. Furthermore, extensive CFD and physical experiments have been performed to investigate the effects of operating in confined or shallow channels. It is found that the efficiency and power generation can significantly increase in confined areas due to the acceleration of the freestream flow around the device. Finally, the Leading Edge team has designed, built, and as of this date, is currently field-testing a 1kW prototype device consisting of two foils operating in parallel. The prototype is attached to the underside of a pontoon boat, and testing is currently underway in the Narragansett Bay near Providence RI. On completion of the field tests, in October 2015, data from the prototype will be analyzed

  18. Experimental study on combustion modes and thrust performance of a staged-combustor of the scramjet with dual-strut

    Science.gov (United States)

    Yang, Qingchun; Chetehouna, Khaled; Gascoin, Nicolas; Bao, Wen

    2016-05-01

    To enable the scramjet operate in a wider flight Mach number, a staged-combustor with dual-strut is introduced to hold more heat release at low flight Mach conditions. The behavior of mode transition was examined using a direct-connect model scramjet experiment along with pressure measurements. The typical operating modes of the staged-combustor are analyzed. Fuel injection scheme has a significant effect on the combustor operating modes, particularly for the supersonic combustion mode. Thrust performances of the combustor with different combustion modes and fuel distributions are reported in this paper. The first-staged strut injection has a better engine performance in the operation of subsonic combustion mode. On the contrast, the second-staged strut injection has a better engine performance in the operation of supersonic combustion mode.

  19. Strut and tie modeling for RC short beams with corroded stirrups

    Directory of Open Access Journals (Sweden)

    Ahmed K. El-Sayed

    Full Text Available Corrosion of steel reinforcement is one of the major problems that shorten the service life of reinforced concrete (RC structures. Steel stirrups, due to their location as an outer reinforcement, are more susceptible to corrosion problems and damage. However, there is limited research work in the literature on the effects of stirrup corrosion on the shear strength of RC beams. This paper attempts to evaluate analytically the residual shear strength of RC short beams with corrosion-damaged stirrups. The shear strength of short or deep beams are generally determined using the strut and tie model. The corrosion effects were implemented in the model to make it capable of predicting the residual shear capacity of RC beams with corroded stirrups. The effect of corrosion is implemented considering the reduction in geometry of the concrete cross section due to spalling and reduction in effective compressive strength of concrete due to corrosion cracks. The proposed strut and tie model which accounts for the corrosion effects was verified using the experimental data available in the literature, and good agreement was found.

  20. Macro-mechanical strut and tie model for analysis of fibrous high-strength concrete corbels

    Directory of Open Access Journals (Sweden)

    E.S. Khalifa

    2012-12-01

    Full Text Available Reinforced concrete (RC corbels becoming a frequent attribute in the building construction with the increasing use of pre-cast high-strength concrete (HSC. The use of fibrous high-strength concrete (FHSC, increases corbel ductility and thus defines the mode of failure of the corbels, depending on the fiber parameters. In this paper a macro-mechanical strut and tie model is proposed for analysis of fibrous high-strength concrete corbels. In this model the fibers can be used as a replacement of horizontal stirrups, due to increasing of shear friction of (FHSC. The analytical macro-mechanical model takes into consideration the effect of fiber volume, fiber length, and fiber diameter, random distribution of fibers, fiber HSC interface and shear span-to-depth ratio, respectively. This model is compared with available experimental results found in literature and a good agreement is obtained. The parametric study is performed to examine for different parameters affecting the analysis of (FHSC corbels using the proposed macro-mechanical strut and tie model.

  1. Determination of Strain Rate Sensitivity of Micro-struts Manufactured Using the Selective Laser Melting Method

    Science.gov (United States)

    Gümrük, Recep; Mines, R. A. W.; Karadeniz, Sami

    2018-03-01

    Micro-lattice structures manufactured using the selective laser melting (SLM) process provides the opportunity to realize optimal cellular materials for impact energy absorption. In this paper, strain rate-dependent material properties are measured for stainless steel 316L SLM micro-lattice struts in the strain rate range of 10-3 to 6000 s-1. At high strain rates, a novel version of the split Hopkinson Bar has been developed. Strain rate-dependent materials data have been used in Cowper-Symonds material model, and the scope and limit of this model in the context of SLM struts have been discussed. Strain rate material data and the Cowper-Symonds model have been applied to the finite element analysis of a micro-lattice block subjected to drop weight impact loading. The model output has been compared to experimental results, and it has been shown that the increase in crush stress due to impact loading is mainly the result of strain rate material behavior. Hence, a systematic methodology has been developed to investigate the impact energy absorption of a micro-lattice structure manufactured using additive layer manufacture (SLM). This methodology can be extended to other micro-lattice materials and configurations, and to other impact conditions.

  2. Hierarchical tailoring of strut architecture to control permeability of additive manufactured titanium implants

    International Nuclear Information System (INIS)

    Zhang, Z.; Jones, D.; Yue, S.; Lee, P.D.; Jones, J.R.; Sutcliffe, C.J.; Jones, E.

    2013-01-01

    Porous titanium implants are a common choice for bone augmentation. Implants for spinal fusion and repair of non-union fractures must encourage blood flow after implantation so that there is sufficient cell migration, nutrient and growth factor transport to stimulate bone ingrowth. Additive manufacturing techniques allow a large number of pore network designs. This study investigates how the design factors offered by selective laser melting technique can be used to alter the implant architecture on multiple length scales to control and even tailor the flow. Permeability is a convenient parameter that characterises flow, correlating to structure openness (interconnectivity and pore window size), tortuosity and hence flow shear rates. Using experimentally validated computational simulations, we demonstrate how additive manufacturing can be used to tailor implant properties by controlling surface roughness at a microstructual level (microns), and by altering the strut ordering and density at a mesoscopic level (millimetre). Highlights: • Experimentally validated permeability prediction tools for hierarchical implants. • Randomised structures form preferential flow channels with stronger shear flows. • Hierarchical strut structures allow independent tailoring of flow and pore size

  3. Ignition and flame stabilization of a strut-jet RBCC combustor with small rocket exhaust.

    Science.gov (United States)

    Hu, Jichao; Chang, Juntao; Bao, Wen

    2014-01-01

    A Rocket Based Combined Cycle combustor model is tested at a ground direct connected rig to investigate the flame holding characteristics with a small rocket exhaust using liquid kerosene. The total temperature and the Mach number of the vitiated air flow, at exit of the nozzle are 1505 K and 2.6, respectively. The rocket base is embedded in a fuel injecting strut and mounted in the center of the combustor. The wall of the combustor is flush, without any reward step or cavity, so the strut-jet is used to make sure of the flame stabilization of the second combustion. Mass flow rate of the kerosene and oxygen injected into the rocket is set to be a small value, below 10% of the total fuel when the equivalence ratio of the second combustion is 1. The experiment has generated two different kinds of rocket exhaust: fuel rich and pure oxygen. Experiment result has shown that, with a relative small total mass flow rate of the rocket, the fuel rich rocket plume is not suitable for ignition and flame stabilization, while an oxygen plume condition is suitable. Then the paper conducts a series of experiments to investigate the combustion characteristics under this oxygen pilot method and found that the flame stabilization characteristics are different at different combustion modes.

  4. Three-Dimensional Printing of Hollow-Struts-Packed Bioceramic Scaffolds for Bone Regeneration.

    Science.gov (United States)

    Luo, Yongxiang; Zhai, Dong; Huan, Zhiguang; Zhu, Haibo; Xia, Lunguo; Chang, Jiang; Wu, Chengtie

    2015-11-04

    Three-dimensional printing technologies have shown distinct advantages to create porous scaffolds with designed macropores for application in bone tissue engineering. However, until now, 3D-printed bioceramic scaffolds only possessing a single type of macropore have been reported. Generally, those scaffolds with a single type of macropore have relatively low porosity and pore surfaces, limited delivery of oxygen and nutrition to surviving cells, and new bone tissue formation in the center of the scaffolds. Therefore, in this work, we present a useful and facile method for preparing hollow-struts-packed (HSP) bioceramic scaffolds with designed macropores and multioriented hollow channels via a modified coaxial 3D printing strategy. The prepared HSP scaffolds combined high porosity and surface area with impressive mechanical strength. The unique hollow-struts structures of bioceramic scaffolds significantly improved cell attachment and proliferation and further promoted formation of new bone tissue in the center of the scaffolds, indicating that HSP ceramic scaffolds can be used for regeneration of large bone defects. In addition, the strategy can be used to prepare other HSP ceramic scaffolds, indicating a universal application for tissue engineering, mechanical engineering, catalysis, and environmental materials.

  5. Generation of a wall jet to control unsteady cavitation over a 2D hydrofoil: visualization and hydroacoustic signal analysis

    Science.gov (United States)

    Timoshevskiy, Mikhail V.; Zapryagaev, Ivan I.

    2017-09-01

    In the paper, the possibility of active manipulation of unsteady cavitating flow over a 2D hydrofoil, a scaled-down model of Francis turbine guide vane (GV), was tested. The flow manipulation was implemented by generating of a wall jet at various flow rates through a spanwise slot nozzle in the foil surface. The experiments were carried out at two attack angles of 3° and 9°. Different cavitation conditions were reached by varying the cavitation number and injection velocity. Temporal and spatial cavity characteristics were studied by means of a high speed visualization. Hydroacoustic measurements were performed in order to investigate pressure pulsations spectral characteristics. It was found that the wall jet generation technique appears to be effective in suppressing cavity unsteady behavior or at least to reduce the corresponding pressure pulsations at low inclination angle and less efficient at high angles of attack, allowing only minor decrease of pressure pulsations.

  6. Numerical 3D analysis of cloud cavitation shedding frequency on a circular leading edge hydrofoil with a barotropic cavitation model

    Science.gov (United States)

    Blume, M.; Skoda, R.

    2015-12-01

    A compressible density-based time-explicit low Mach number consistent viscous flow solver is utilised in combination with a barotropic cavitation model for the analysis of cloud cavitation on a circular leading edge (CLE) hydrofoil. For 5° angle of attack, cloud structure and shedding frequency for different cavitation numbers are compared to experimental data. A strong grid sensitivity is found in particular for high cavitation numbers. On a fine grid, a very good agreement with validation data is achieved even without explicit turbulence model. The neglect of viscous effects as well as a two-dimensional set-up lead to a less realistic prediction of cloud structures and frequencies. Comparative simulations with the Sauer-Schnerr cavitation model and modified pre-factors of the mass transfer terms underestimate the measured shedding frequency.

  7. High-performance sailboat hydrofoil optimization using vortex lattice methods, and the effects of free-stream turbulence

    Science.gov (United States)

    Meneghello, Gianluca; Beyhaghi, Pooriya; Bewley, Thomas

    2016-11-01

    The identification of an optimized hydrofoil shape depends on an accurate characterization of both its geometry and the incoming, turbulent, free-stream flow. We analyze this dependence using the computationally inexpensive vortex lattice model implemented in AVL, coupled with the recently developed global, derivative-free optimization algorithm implemented in Δ - DOGS . Particular attention will be given to the effect of the free-stream turbulence level - as modeled by a change in the viscous drag coefficients - on the optimized values of the parameters describing the three dimensional shape of the foil. Because the simplicity of AVL, when contrasted with more complex and computationally expensive LES or RANS models, may cast doubts on its usefulness, its validity and limitations will be discussed by comparison with water tank measurement, and again taking into account the effect of the uncertainty in the free-stream characterization.

  8. Ultimate Load Capacity and Behavior of Thin-Walled Curved-Steel Square Struts, Subjected to Compressive Load

    Directory of Open Access Journals (Sweden)

    S.Mohammad Reza Mortazavi

    2016-06-01

    Full Text Available There have been some experimental tests on hollow curved-steel struts with thin-walled square sections, in order to investigate their general behavior, particularly their capacity for bearing differing loads. One set of square tubes are cold-formed into segments of circular arcs with curvature radii, equal to 4000 mm. Different lengths of curved struts are fabricated so as to cover a practical range of slenderness ratios. The struts tests were pin-ended and had slenderness ratios, based on the straight length between ends ranging from 31-126. The cold-forming operation induces initial inelastic behavior and associated residual stresses. There is, therefore, an interaction among material effects, such as the strain hardening capacity, the Bauschinger effect, strain aging, and residual stresses, together with the significant geometrical effect of the initial curvature, caused by the cold-forming operation. Eventually the results from three series of tests, which are taken on fully-aged and stress-relief-annealed square curved struts, are compared. The variations in load carrying response are discussed.

  9. Experimental investigation on combustion performance of cavity-strut injection of supercritical kerosene in supersonic model combustor

    Science.gov (United States)

    Sun, Ming-bo; Zhong, Zhan; Liang, Jian-han; Wang, Hong-bo

    2016-10-01

    Supersonic combustion with cavity-strut injection of supercritical kerosene in a model scramjet engine was experimentally investigated in Mach 2.92 facility with the stagnation temperatures of approximately 1430 K. Static pressure distribution in the axial direction was determined using pressure transducers installed along the centerline of the model combustor top walls. High speed imaging camera was used to capture flame luminosity and combustion region distribution. Multi-cavities were used to and stabilize the combustion in the supersonic combustor. Intrusive injection by thin struts was used to enhance the fuel-air mixing. Supercritical kerosene at temperatures of approximately 780 K and various pressures was prepared using a heat exchanger driven by the hot gas from a pre-burner and injected at equivalence ratios of approximately 1.0. In the experiments, combustor performances with different strut injection schemes were investigated and compared to direct wall injection scheme based on the measured static pressure distributions, the specific thrust increments and the images obtained by high-speed imaging camera. The experimental results showed that the injection by thin struts could obtain an enhanced mixing in the field but could not acquire a steady flame when mixing field cannot well match cavity separation region. There is no significant difference on performance between different schemes since the unsteady intermittent and oscillating flame leads to no actual combustion efficiency improvement.

  10. Euler strut: a mechanical analogy for dynamics in the vicinity of a critical point

    International Nuclear Information System (INIS)

    Bobnar, Jaka; Podgornik, Rudolf; Susman, Katarina; Cepic, Mojca; Parsegian, V Adrian; Rand, Peter R

    2011-01-01

    An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point load at its end shows that when approaching the critical end-load, the period of such an inverted pendulum diverges in a fashion analogous to a 'soft mode' critical slowing down in, for example, a ferroelectric phase transition of displacive type. We thus show that an advanced concept of solid state physics, i.e. 'soft mode' dynamics and critical slowing down, observable in a variety of second-order phase transitions, can be actualized in this simple mechanical system. The variable loads attached to a vertical spring allow for an experimental implementation and quantitative measurements as an illustration of this analogy.

  11. Dynamic characteristics of vibration isolation platforms considering the joints of the struts

    Science.gov (United States)

    Zhang, Jingrui; Guo, Zixi; Zhang, Yao

    2016-09-01

    This paper discusses the dynamic characteristics of the impacts and corresponding frictions generated by the clearances of joints of vibration isolation platforms for control moment gyroscopes (CMGs) on spacecraft. A contact force model is applied using a nonlinear contact force model, and the frictions in the joints are considered in the dynamic analysis. First, the dynamic characteristics of a single isolation strut with spherical joints were studied, and joints with different initial clearance sizes were separately analyzed. Then, dynamic models of the vibration isolation platform for a CMG cluster with both perfect joints and joints with clearances were established. During the numeral simulation, joints with different elastic moduli were used to study the nonlinear characteristics. Finally, the distributions of the collision points, which can serve as a reference for the reliability and lifetime of a platform, were given.

  12. Nonlinear mode interaction in equal-leg angle struts susceptible to cellular buckling.

    Science.gov (United States)

    Bai, L; Wang, F; Wadee, M A; Yang, J

    2017-11-01

    A variational model that describes the interactive buckling of a thin-walled equal-leg angle strut under pure axial compression is presented. A formulation combining the Rayleigh-Ritz method and continuous displacement functions is used to derive a system of differential and integral equilibrium equations for the structural component. Solving the equations using numerical continuation reveals progressive cellular buckling (or snaking) arising from the nonlinear interaction between the weak-axis flexural buckling mode and the strong-axis flexural-torsional buckling mode for the first time-the resulting behaviour being highly unstable. Physical experiments conducted on 10 cold-formed steel specimens are presented and the results show good agreement with the variational model.

  13. Automated detection of vessel lumen and stent struts in intravascular optical coherence tomography to evaluate stent apposition and neointimal coverage

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Hyeong Soo; Kim, Chang-Soo; Yoo, Hongki, E-mail: kjwmm@korea.ac.kr, E-mail: hyoo@hanyang.ac.kr [Department of Biomedical Engineering, Hanyang University, Seoul 04763 (Korea, Republic of); Lee, Jae Joong; Song, Joon Woo; Kim, Jin Won, E-mail: kjwmm@korea.ac.kr, E-mail: hyoo@hanyang.ac.kr [Division of Interventional Cardiology, Cardiovascular Center, Korea University Guro Hospital, Seoul 08308 (Korea, Republic of)

    2016-04-15

    Purpose: Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the microstructure of arterial walls in vivo. IV-OCT enables the clinician to clearly observe and accurately measure stent apposition and neointimal coverage of coronary stents, which are associated with side effects such as in-stent thrombosis. In this study, the authors present an algorithm for quantifying stent apposition and neointimal coverage by automatically detecting lumen contours and stent struts in IV-OCT images. Methods: The algorithm utilizes OCT intensity images and their first and second gradient images along the axial direction to detect lumen contours and stent strut candidates. These stent strut candidates are classified into true and false stent struts based on their features, using an artificial neural network with one hidden layer and ten nodes. After segmentation, either the protrusion distance (PD) or neointimal thickness (NT) for each strut is measured automatically. In randomly selected image sets covering a large variety of clinical scenarios, the results of the algorithm were compared to those of manual segmentation by IV-OCT readers. Results: Stent strut detection showed a 96.5% positive predictive value and a 92.9% true positive rate. In addition, case-by-case validation also showed comparable accuracy for most cases. High correlation coefficients (R > 0.99) were observed for PD and NT between the algorithmic and the manual results, showing little bias (0.20 and 0.46 μm, respectively) and a narrow range of limits of agreement (36 and 54 μm, respectively). In addition, the algorithm worked well in various clinical scenarios and even in cases with a low level of stent malapposition and neointimal coverage. Conclusions: The presented automatic algorithm enables robust and fast detection of lumen contours and stent struts and provides quantitative measurements of PD and NT. In addition, the algorithm was validated using

  14. Free fibular strut graft in neglected femoral neck fractures in adult

    Directory of Open Access Journals (Sweden)

    Azam Md Quamar

    2009-01-01

    Full Text Available Background: Neglected femoral neck fracture in adults still poses a formidable challenge. Existing treatment options varies from osteotomy (with or without graft to osteosynthesis using various implants and grafting techniques (muscle pedicle, vascularized, and nonvascularized fibula. The aim of this study was to assess outcome of nonvascularized fibular strut graft and cancellous screw fixation in neglected femoral neck fractures in the younger age group. Materials and Methods: Medical records of 32 patients of neglected femoral neck fracture, in the age group of 22-45 years (mean 37.8 years, operated between May 1994 to December 2001, were retrospectively reviewed. After the application of inclusion and exclusion criteria, 28 patients having three years minimum follow-up (mean 4.6 years were included. Delay between injury and operation varied from four weeks to 42 weeks (mean 16.4 weeks. Closed reduction was achieved in 17 patients; open reduction through Watson-Jones anterolateral approach was performed in the remaining 15 patients in whom closed reduction failed. The fracture was transfixed with three parallel guide wires. Appropriate sized cannulated lag screw (7 mm was then inserted in two of the wires. Selection of the third guide wire for fibula depended on the space available in both anteroposterior and lateral view. Results: Satisfactory bony union was obtained in 25 patients, of whom in four cases, the union occurred in 10-20° (mean 15° of varus. Nonunion occurred in three patients (9.37%, and aseptic necrosis occurred in another six patients (18.75%. Of the 25 patients where union was achieved, five patients showed excellent results; 14 good and six had poor functional result, as evaluated using modified Anglen criteria. Conclusion: Nonvascularized fibular strut graft along with cancellous screws provides a dependable and technically less-demanding alternative procedure for neglected femoral neck fractures in young adults. Fibula

  15. Use of non-vascularized autologous fibula strut graft in the treatment of segmental bone loss.

    Science.gov (United States)

    Lawal, Y Z; Garba, E S; Ogirima, M O; Dahiru, I L; Maitama, M I; Abubakar, K; Ejagwulu, F S

    2011-01-01

    Fractures resulting in segmental bone loss challenge the orthopedic surgeon. Orthopedic surgeons in developed countries have the option of choosing vascularized bone transfers, bone transport, allogenic bone grafts, bone graft substitutes and several other means to treat such conditions. In developing countries where such facilities or expertise may not be readily available, the surgeon has to rely on other techniques of treatment. Non-vascularized fibula strut graft and cancellous bone grafting provides a reliable means of treating such conditions in developing countries. Over a period of six years all patients with segmental bone loss either from trauma or oncologic resection were included in the study. Data concerning the type of wound, size of gap and skin loss at tumor or fracture were obtained from clinical examination and radiographs. Ten patients satisfied the inclusion criteria for the study. The average length of the fibula strut is 7 cm, the longest being 15 cm and the shortest 3 cm long. The average defect length was 6.5 cm. Five patients had Gustillo III B open tibial fractures. One patient had recurrent giant cell tumor of the distal radius and another had a polyostotic bone cyst of the femur, which was later confirmed to be osteosarcoma. Another had non-union of distal tibial fracture with shortening. One other patient had gunshot injury to the femur and was initially managed by skeletal traction. The tenth patient had a comminuted femoral fracture. All trauma patients had measurement of missing segment, tissue envelope assessment, neurological examination, and debridement under general anesthesia with fracture stabilization with external fixators or casts. Graft incorporation was 80% in all treated patients. Autologous free, non-vascularized fibula and cancellous graft is a useful addition to the armamentarium of orthopedic surgeon in developing countries attempting to manage segmental bone loss, whether created by trauma or excision of tumors.

  16. Ununited fracture neck of femur treated with closed reduction and internal fixation with cancellous screw and fibular strut graft

    Directory of Open Access Journals (Sweden)

    Singh Daria

    2006-01-01

    Full Text Available Background: Ununited fracture neck of femur in young adults has been tackled in various ways. Methods: Twenty five patients of ununited fracture neck of femur in age group 21-55 years were treated by closed reduction, cancellous screw fixation and fibular strut graft and followed up for 2-6 years. Time gap between injury and operation was 6 weeks to 58 weeks. Five cases were previously fixed with various fixation devices. Results: Osseous union was achieved in 24 cases with average time of 18.16 weeks. Main complication encountered in follow-up was avascular necrosis of femoral head, others were joint stiffness and shortening. Functional end results were good to excellent in 24 cases. Conclusion: Closed reduction with internal fixation by cancellous screw and fibular strut grafting is easy and useful procedure.

  17. Structural FEM analysis of the strut-to-fuselage joint of a two-seat composite aircraft

    International Nuclear Information System (INIS)

    Vargas-Rojas, Erik; Camarena-Arellano, Diego; Hernández-Moreno, Hilario

    2014-01-01

    An analysis of a strut-to-fuselage joint is realized in order to evaluate the zones with a high probability of failure by means of a safety factor. The whole section is analyzed using the Finite Element Method (FEM) so as to estimate static resistance behavior, therefore it is necessary a numerical mock-up of the section, the mechanical properties of the Carbon-Epoxy (C-Ep) material, and to evaluate the applied loads. Results of the analysis show that the zones with higher probability of failure are found around the wing strut and the fuselage joint, with a safety factor lower than expected in comparison with the average safety factor used on aircrafts built mostly with metals

  18. Structural FEM analysis of the strut-to-fuselage joint of a two-seat composite aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Rojas, Erik, E-mail: erikvargasrojas@hotmail.com; Camarena-Arellano, Diego, E-mail: erikvargasrojas@hotmail.com; Hernández-Moreno, Hilario, E-mail: erikvargasrojas@hotmail.com [IPN, ESIME Ticomán, Av. Ticomán 600, Col. San José Ticomán 07340 (Mexico)

    2014-05-15

    An analysis of a strut-to-fuselage joint is realized in order to evaluate the zones with a high probability of failure by means of a safety factor. The whole section is analyzed using the Finite Element Method (FEM) so as to estimate static resistance behavior, therefore it is necessary a numerical mock-up of the section, the mechanical properties of the Carbon-Epoxy (C-Ep) material, and to evaluate the applied loads. Results of the analysis show that the zones with higher probability of failure are found around the wing strut and the fuselage joint, with a safety factor lower than expected in comparison with the average safety factor used on aircrafts built mostly with metals.

  19. Research on shock wave characteristics in the isolator of central strut rocket-based combined cycle engine under Ma5.5

    Science.gov (United States)

    Wei, Xianggeng; Xue, Rui; Qin, Fei; Hu, Chunbo; He, Guoqiang

    2017-11-01

    A numerical calculation of shock wave characteristics in the isolator of central strut rocket-based combined cycle (RBCC) engine fueled by kerosene was carried out in this paper. A 3D numerical model was established by the DES method. The kerosene chemical kinetic model used the 9-component and 12-step simplified mechanism model. Effects of fuel equivalence ratio, inflow total temperature and central strut rocket on-off on shock wave characteristics were studied under Ma5.5. Results demonstrated that with the increase of equivalence ratio, the leading shock wave moves toward upstream, accompanied with higher possibility of the inlet unstart. However, the leading shock wave moves toward downstream as the inflow total temperature rises. After the central strut rocket is closed, the leading shock wave moves toward downstream, which can reduce risks of the inlet unstart. State of the shear layer formed by the strut rocket jet flow and inflow can influence the shock train structure significantly.

  20. Coolant pressure and airflow distribution in a strut-supported transpiration-cooled vane for a gas turbine engine

    Science.gov (United States)

    Kaufman, A.; Poferl, D. J.; Richards, H. T.

    1972-01-01

    An analysis to predict pressure and flow distribution in a strut-supported wire-cloth vane was developed. Results were compared with experimental data obtained from room-temperature airflow tests conducted over a range of vane inlet airflow rates from 10.7 to 40.4 g/sec (0.0235 to 0.0890 lb/sec). The analytical method yielded reasonably accurate predictions of vane coolant flow rate and pressure distribution.

  1. Fracture and embolization of a Celect inferior vena cava filter strut to the liver: A Case Report

    International Nuclear Information System (INIS)

    Kim, So Hee; Song, Yun Gyu

    2017-01-01

    Inferior vena cava (IVC) filters are typically used for prophylaxis against pulmonary embolism. A new version of the Günther Tulip filter, the Celect IVC filter was introduced in April 2007. To the best of our knowledge, there are no reports commenting on Celect IVC filter fracture and fragment embolization to liver. We report a case in which the strut of the Celect IVC filter embolized to the liver

  2. Fracture and embolization of a Celect inferior vena cava filter strut to the liver: A Case Report

    Energy Technology Data Exchange (ETDEWEB)

    Kim, So Hee; Song, Yun Gyu [Dept. of Radiology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon (Korea, Republic of)

    2017-07-15

    Inferior vena cava (IVC) filters are typically used for prophylaxis against pulmonary embolism. A new version of the Günther Tulip filter, the Celect IVC filter was introduced in April 2007. To the best of our knowledge, there are no reports commenting on Celect IVC filter fracture and fragment embolization to liver. We report a case in which the strut of the Celect IVC filter embolized to the liver.

  3. Experimental evaluation of the strut-and-tie method applied to low-rise concrete walls

    Directory of Open Access Journals (Sweden)

    Julian Carrillo León

    2010-01-01

    Full Text Available The strut-and-tie method (S-T is a practical tool for the seismic design of reinforced concrete elements. Experimental and analytical research with low-rise concrete walls was carried out for assessing the S-T method proposed by the current ACI-318 building code. Four specimens designed to fail during shear and shaking table tests were included in the experimental programme. The variables studied consisted of the type of concrete (normal and cellular weight, the amount of steel web (0.125% and 0.25% and the type of web reinforcement against shear (corrugated bars and welded wire mesh. Wall properties were typical of low-rise housing in Mexico. When the calculated shear strength was compared with the measured one it was found that the S-T method proposed by the ACI-318 building code suitably estimated the shear capacity of the models being studied. However, the wall’s shear failure mode, loading rate, the number of cycles and the cumulative energy dissipated would noticeably affect the degradation in strength of low-rise, reinforced concrete walls.

  4. Numerical Investigation into Effects of Viscous Flux Vectors on Hydrofoil Cavitation Flow and Its Radiated Flow Noise

    Directory of Open Access Journals (Sweden)

    Sanghyeon Kim

    2018-02-01

    Full Text Available In this study, cavitation flow around a hydrofoil and its radiated hydro-acoustic fields were numerically investigated, with an emphasis on the effects of viscous flux vectors. The full three-dimensional unsteady compressible Reynolds-averaged Navier–Stokes equations were numerically solved. The mass transfer model was adopted to model phase changes between liquid water and vapor. To resolve the numerical instability problem arising from the rapid changes in local density and speed of sound of the mixture, the preconditioning and dual-time stepping methods were employed. The filter-based turbulent model was applied to resolve the unstable cavitation flow field more accurately. In splitting the viscous terms, three approaches for dealing with viscous flux vectors were considered: the so-called viscous lagging, full viscous, and thin-layer models. Radiated hydro-acoustic waves were predicted by applying the Ffowcs Williams and Hawkings equations. The effects of the viscous flux vectors on the predicted flow fields and its radiated noise were then examined by comparing the hydro-dynamic forces, velocity distribution, volume fraction, far-field sound directivities, and sound spectrum of the three approaches. The results revealed that the thin-layer model can provide predictions as accurate as the full viscous model, but required less computational time.

  5. Cavitating flow control through continuous tangential mass injection on a 2D hydrofoil at a small attack angle

    Directory of Open Access Journals (Sweden)

    Timoshevskiy Mikhail V.

    2016-01-01

    Full Text Available We studied cavitating flow over the suction side of a symmetric 2D foil – a scaled-down model of high-pressure hydroturbine guide vanes (GV – in different cavitation regimes at the attack angle of 3°. High-speed imaging was used to analyze spatial patterns and time dynamics of the gas-vapour cavities. A hydroacoustic pressure transducer was employed to register time-spectra of pressure fluctuations nearby the hydrofoil. A PIV technique was applied to measure the velocity fields and its fluctuations. The active flow control was implemented by means of a continuous liquid supply with different flow rates through a slot channel located in the GV surface. It was found that the active mass injection does not influence the primary flow upstream of the slot channel position. For the cavitation-free and cavitation inception cases, the injection was shown to make the turbulent wake past the GV section more intense. However, at the developed cavitation regimes the active flow management made it possible to reduce substantially the amplitude or even totally suppress the periodic cavity length oscillations and pressure pulsations associated with them.

  6. Monte Carlo Investigation on the Effect of Heterogeneities on Strut Adjusted Volume Implant (SAVI) Dosimetry

    Science.gov (United States)

    Koontz, Craig

    Breast cancer is the most prevalent cancer for women with more than 225,000 new cases diagnosed in the United States in 2012 (ACS, 2012). With the high prevalence, comes an increased emphasis on researching new techniques to treat this disease. Accelerated partial breast irradiation (APBI) has been used as an alternative to whole breast irradiation (WBI) in order to treat occult disease after lumpectomy. Similar recurrence rates have been found using ABPI after lumpectomy as with mastectomy alone, but with the added benefit of improved cosmetic and psychological results. Intracavitary brachytherapy devices have been used to deliver the APBI prescription. However, inability to produce asymmetric dose distributions in order to avoid overdosing skin and chest wall has been an issue with these devices. Multi-lumen devices were introduced to overcome this problem. Of these, the Strut-Adjusted Volume Implant (SAVI) has demonstrated the greatest ability to produce an asymmetric dose distribution, which would have greater ability to avoid skin and chest wall dose, and thus allow more women to receive this type of treatment. However, SAVI treatments come with inherent heterogeneities including variable backscatter due to the proximity to the tissue-air and tissue-lung interfaces and variable contents within the cavity created by the SAVI. The dose calculation protocol based on TG-43 does not account for heterogeneities and thus will not produce accurate dosimetry; however Acuros, a model-based dose calculation algorithm manufactured by Varian Medical Systems, claims to accurately account for heterogeneities. Monte Carlo simulation can calculate the dosimetry with high accuracy. In this thesis, a model of the SAVI will be created for Monte Carlo, specifically using MCNP code, in order to explore the affects of heterogeneities on the dose distribution. This data will be compared to TG-43 and Acuros calculated dosimetry to explore their accuracy.

  7. Stents Eluting 6-Mercaptopurine Reduce Neointima Formation and Inflammation while Enhancing Strut Coverage in Rabbits.

    Directory of Open Access Journals (Sweden)

    Matthijs S Ruiter

    Full Text Available The introduction of drug-eluting stents (DES has dramatically reduced restenosis rates compared with bare metal stents, but in-stent thrombosis remains a safety concern, necessitating prolonged dual anti-platelet therapy. The drug 6-Mercaptopurine (6-MP has been shown to have beneficial effects in a cell-specific fashion on smooth muscle cells (SMC, endothelial cells and macrophages. We generated and analyzed a novel bioresorbable polymer coated DES, releasing 6-MP into the vessel wall, to reduce restenosis by inhibiting SMC proliferation and decreasing inflammation, without negatively affecting endothelialization of the stent surface.Stents spray-coated with a bioresorbable polymer containing 0, 30 or 300 μg 6-MP were implanted in the iliac arteries of 17 male New Zealand White rabbits. Animals were euthanized for stent harvest 1 week after implantation for evaluation of cellular stent coverage and after 4 weeks for morphometric analyses of the lesions.Four weeks after implantation, the high dose of 6-MP attenuated restenosis with 16% compared to controls. Reduced neointima formation could at least partly be explained by an almost 2-fold induction of the cell cycle inhibiting kinase p27Kip1. Additionally, inflammation score, the quantification of RAM11-positive cells in the vessel wall, was significantly reduced in the high dose group with 23% compared to the control group. Evaluation with scanning electron microscopy showed 6-MP did not inhibit strut coverage 1 week after implantation.We demonstrate that novel stents coated with a bioresorbable polymer coating eluting 6-MP inhibit restenosis and attenuate inflammation, while stimulating endothelial coverage. The 6-MP-eluting stents demonstrate that inhibition of restenosis without leaving uncovered metal is feasible, bringing stents without risk of late thrombosis one step closer to the patient.

  8. Computational fluid dynamics model for predicting flow of viscous fluids in a large fermentor with hydrofoil flow impellers and internal cooling coils

    Science.gov (United States)

    Kelly; Humphrey

    1998-03-01

    Considerable debate has occurred over the use of hydrofoil impellers in large-scale fermentors to improve mixing and mass transfer in highly viscous non-Newtonian systems. Using a computational fluid dynamics software package (Fluent, version 4.30) extensive calculations were performed to study the effect of impeller speed (70-130 rpm), broth rheology (value of power law flow behavior index from 0.2 to 0.6), and distance between the cooling coil bank and the fermentor wall (6-18 in.) on flow near the perimeter of a large (75-m3) fermentor equipped with A315 impellers. A quadratic model utilizing the data was developed in an attempt to correlate the effect of A315 impeller speed, power law flow behavior index, and distance between the cooling coil bank and the fermentor wall on the average axial velocity in the coil bank-wall region. The results suggest that there is a potential for slow or stagnant flow in the coil bank-wall region which could result in poor oxygen and heat transfer for highly viscous fermentations. The results also indicate that there is the potential for slow or stagnant flow in the region between the top impeller and the gas headspace when flow through the coil bank-wall region is slow. Finally, a simple guideline was developed to allow fermentor design engineers to predict the degree of flow behind a bank of helical cooling coils in a large fermentor with hydrofoil flow impellers.

  9. Infection rate in mandibular angle fractures treated with a 2.0-mm 8-hole curved strut plate.

    Science.gov (United States)

    Bui, Peter; Demian, Nagi; Beetar, Patrick

    2009-04-01

    The aim of this study was to determine the rate of postoperative infection and the efficacy of removing teeth in the line of mandibular angle fractures treated with 2.0-mm 8-hole titanium curved strut plates. Our understanding is that this method of repair is currently being used only in a few centers in the United States. A retrospective review of mandibular angle fractures treated with a 2.0-mm 8-hole strut plate during a 4-year period. Postoperative antibiotics were given for 1 week. Follow-up appointments were 4 weeks or longer. A nonchewing diet was instructed for 6 weeks. Data for all selected patients include the information such as age, gender, etiology of injuries, medical history, concurrent injuries, nerve deficits, pre- and postoperative antibiotic administration, postop infection, a presence or absence of teeth in the line of fractures, and whether these teeth were removed. Four patients (4 of 49 or 8.2%) developed infections. Two of those patients had a tooth in the line of a fracture that was retained (2 of 14 or 14%). The third had a tooth in the line of a fracture that was extracted (1 of 18 or 5.6%). The fourth patient was 1 of the 17 patients who did not have teeth in the line of fracture and developed infection (1 of 17 or 5.9%). None of the patients developed failed hardware, malunion, nonunion, malocclusion, or iatrogenic nerve injury. The use of a 2.0-mm 8-hole strut plate is associated with a low infection rate (8.2%). The infection rate for those mandibular angle fractures with teeth in the line of fracture retained was 14% compared with 5.6% for those fractures with the teeth in the line of fracture extracted.

  10. Relationship between peri-strut low intensity areas and vascular healing response after everolimus-eluting bioresorbable scaffold implantation: An optical coherence tomography study.

    Science.gov (United States)

    Sato, Takao; Jose, John; El-Mawardy, Mohamed; Sulimov, Dmitriy S; Tölg, Ralph; Richardt, Gert; Abdel-Wahab, Mohamed

    2017-04-01

    Peri-strut low intensity areas (PLIA) surrounding metallic coronary stent struts on optical coherence tomography (OCT) images have been histologically related to delayed healing and inflammation, and have been associated with neointimal proliferation. The relationship between PLIA and vascular healing response after bioresorbable scaffold (BRS) implantation remains unclear. This study includes 38 consecutive patients (50 scaffolds) evaluated using OCT 12 months after BRS implantation. Mean and percent neointimal area were quantified. A PLIA was defined as a peri-strut region with an homogenous lower intensity appearance than the surrounding tissue on OCT images without significant signal attenuation. Cross sections were scored as follows: score 0, no PLIA; score 1, BRS implantation appears to be significantly associated with neointimal formation. Copyright © 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  11. Use of intramedullary fibular strut graft: a novel adjunct to plating in the treatment of osteoporotic humeral shaft nonunion.

    Science.gov (United States)

    Vidyadhara, S; Vamsi, K; Rao, Sharath K; Gnanadoss, James J; Pandian, S

    2009-08-01

    Humeral shaft fractures respond well to conservative treatment and unite without much problem. Since it is uncommon, there is not much discussion regarding the management of nonunion in the literature, and hence this is a challenge to the treating orthopaedic surgeon. Osteoporosis of the fractured bone and stiffness of the surrounding joints compounds the situation further. The Ilizarov fixator, locking compression plate, and vascularised fibular graft are viable options in this scenario but are technically demanding. We used a fibular strut graft for bridging the fracture site in order to enhance the pull-out strength of the screws of the dynamic compression plate. Six patients in the study had successful uneventful union of the fracture at the last follow-up. The fibula is easy to harvest and produces less graft site morbidity. None of the study patients needed additional iliac crest bone grafting. This is the largest reported series of patients with osteoporotic atrophic nonunion of humerus successfully treated solely using the combination of an intramedullary fibular strut graft and dynamic compression plate.

  12. Comparison of Single Ti6Al4V Struts Made Using Selective Laser Melting and Electron Beam Melting Subject to Part Orientation

    Directory of Open Access Journals (Sweden)

    Volker Weißmann

    2017-03-01

    Full Text Available The use of additive manufacturing technologies to produce lightweight or functional structures is widespread. Especially Ti6Al4V plays an important role in this development field and parts are manufactured and analyzed with the aim to characterize the mechanical properties of open-porous structures and to generate scaffolds with properties specific to their intended application. An SLM and an EBM process were used respectively to fabricate the Ti6Al4V single struts. For mechanical characterization, uniaxial compression tests and hardness measurements were conducted. Furthermore, the struts were manufactured in different orientations for the determination of the mechanical properties. Roughness measurements and a microscopic characterization of the struts were also carried out. Some parts were characterized following heat treatment (hot isostatic pressing. A functional correlation was found between the compressive strength and the slenderness ratio (λ as well as the equivalent diameter (d and the height (L of EBM and SLM parts. Hardness investigations revealed considerable differences related to the microstructure. An influence of heat treatment as well as of orientation could be determined. In this work, we demonstrate the influence of the fabrication quality of single struts, the roughness and the microstructure on mechanical properties as a function of orientation.

  13. Impact of strut thickness on acute mechanical performance: A comparison study using optical coherence tomography between DESolve 150 and DESolve 100.

    Science.gov (United States)

    Boeder, Niklas F; Dörr, Oliver; Bauer, Timm; Mattesini, Alessio; Elsässer, Albrecht; Liebetrau, Christoph; Achenbach, Stephan; Hamm, Christian W; Nef, Holger M

    2017-11-01

    To evaluate the acute performance of a novolimus-eluting bioresorbable scaffold (BRS) with different strut thickness (DESolve system 150 and 100) using optical coherence tomography (OCT) in terms of appropriate scaffold deployment. Outcome after BRS implantation seen in registries and meta-analyses continue to show a higher rate of scaffold thrombosis than those reported with DES. Thus, second scaffold generations with lower strut thickness might have potential advantages in terms of flow disturbance. However, whether mechanical properties are comparable has to be evaluated. Fifty-seven patients undergoing OCT-guided scaffold implantation were enrolled consecutively in this retrospective study. The final pullback after DESolve 150 (n=42) and DESolve 100 (n=15) were compared. The following indices were calculated: mean and minimum area, residual area stenosis, incomplete strut apposition, tissue prolapse, eccentricity and symmetry indexes, strut fracture, and edge dissection. Most patients suffered a multi vessel disease. Maximum pre-dilatation balloon inflation pressure was 13.5±3.2 vs 14.5±2.5atm. OCT analysis showed a minimal lumen area of 6.1±1.9 vs 5.2±1.6mm 2 , p=0.06. Mean residual area stenosis was 15.3% vs 21.3, p=0.22. Mean eccentricity index did not differ significantly (0.8±0.1 vs 0.6±0.1, p=0.61). Prolapse area was 4.5±8.8 vs 5.6±9.8mm 2 . OCT showed similar post-procedural scaffold geometry and outcome indicating that both BRS may be implanted with good acute performance. However, the trend towards a smaller MLA and a higher percentage of RAS suggest a decreased radial strength for the 100μm BRS. The attempt to reduce strut thickness should not result in loss of radial strength. Rates of scaffold thrombosis after bioresorbable scaffold (BRS) implantation are reported to be higher than after metallic stent (DES) implantation. Thus, second scaffold generations with lower strut thickness might have potential advantages in terms of flow

  14. Locomotor function of forelimb protractor and retractor muscles of dogs: evidence of strut-like behavior at the shoulder.

    Science.gov (United States)

    Carrier, David R; Deban, Stephen M; Fischbein, Timna

    2008-01-01

    The limbs of running mammals are thought to function as inverted struts. When mammals run at constant speed, the ground reaction force vector appears to be directed near the point of rotation of the limb on the body such that there is little or no moment at the joint. If this is true, little or no external work is done at the proximal joints during constant-speed running. This possibility has important implications to the energetics of running and to the coupling of lung ventilation to the locomotor cycle. To test if the forelimb functions as an inverted strut at the shoulder during constant-speed running and to characterize the locomotor function of extrinsic muscles of the forelimb, we monitored changes in the recruitment of six muscles that span the shoulder (the m. pectoralis superficialis descendens, m. pectoralis profundus, m. latissimus dorsi, m. omotransversarius, m. cleidobrachialis and m. trapezius) to controlled manipulations of locomotor forces and moments in trotting dogs (Canis lupus familiaris Linnaeus 1753). Muscle activity was monitored while the dogs trotted at moderate speed (approximately 2 m s(-1)) on a motorized treadmill. Locomotor forces were modified by (1) adding mass to the trunk, (2) inclining the treadmill so that the dogs ran up- and downhill (3) adding mass to the wrists or (4) applying horizontally directed force to the trunk through a leash. When the dogs trotted at constant speed on a level treadmill, the primary protractor muscles of the forelimb exhibited activity during the last part of the ipsilateral support phase and the beginning of swing phase, a pattern that is consistent with the initiation of swing phase but not with active protraction of the limb during the beginning of support phase. Results of the force manipulations were also consistent with the protractor muscles initiating swing phase and contributing to active braking via production of a protractor moment on the forelimb when the dogs decelerate. A similar

  15. Funzionalizzazione della mandibola dopo ricostruzione con lembo libero rivascolarizzato di fibula "single strut". Al di là del deficit di verticalità.

    OpenAIRE

    Gessaroli, Manlio

    2009-01-01

    Obiettivi: Valutare la modalità  più efficace per la riabilitazione funzionale del limbo libero di fibula "single strut", dopo ampie resezioni per patologia neoplastica maligna del cavo orale. Metodi: Da una casistica di 62 ricostruzioni microvascolari con limbo libero di fibula, 11 casi sono stati selezionati per essere riabilitati mediante protesi dentale a supporto implantare. 6 casi sono stati trattati senza ulteriori procedure chirurgiche ad eccezione dell'implantologia (gruppo 1), a...

  16. A numerical study of steady 2D flow around NACA 0015 and NACA 0012 hydrofoil with free surface using VOF method

    Directory of Open Access Journals (Sweden)

    Adjali Saadia

    2015-01-01

    Full Text Available Accurate simulation of turbulent free surface flows around surface ships has a central role in the optimal design of such naval vessels. The flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. In this paper, our goal is to estimate the lift and drag coefficients for NACA 0012 of hydrofoil advancing in calm water under steady conditions with free surface and emerged NACA 0015. The commercial CFD software FLUENT version 14 is used for the computations in the present study. The calculated grid is established using the code computer GAMBIT 2.3.26.The shear stress k-ωSST model is used for turbulence modeling and the volume of fluid technique is employed to simulate the free-surface motion. In this computation, the second order upwind scheme is used for discretizing the convection terms in the momentum transport equations, the Modified HRIC scheme for VOF discretisation. The results obtained compare well with the experimental data.

  17. A numerical study of steady 2D flow around NACA 0015 and NACA 0012 hydrofoil with free surface using VOF method

    Science.gov (United States)

    Adjali, Saadia; Belkadi, Mustapha; Aounallah, Mohammed; Imine, Omar

    2015-05-01

    Accurate simulation of turbulent free surface flows around surface ships has a central role in the optimal design of such naval vessels. The flow problem to be simulated is rich in complexity and poses many modeling challenges because of the existence of breaking waves around the ship hull, and because of the interaction of the two-phase flow with the turbulent boundary layer. In this paper, our goal is to estimate the lift and drag coefficients for NACA 0012 of hydrofoil advancing in calm water under steady conditions with free surface and emerged NACA 0015. The commercial CFD software FLUENT version 14 is used for the computations in the present study. The calculated grid is established using the code computer GAMBIT 2.3.26.The shear stress k-ωSST model is used for turbulence modeling and the volume of fluid technique is employed to simulate the free-surface motion. In this computation, the second order upwind scheme is used for discretizing the convection terms in the momentum transport equations, the Modified HRIC scheme for VOF discretisation. The results obtained compare well with the experimental data.

  18. Dual role of circulating endothelial progenitor cells in stent struts endothelialisation and neointimal regrowth: A substudy of the IN-PACT CORO trial

    Energy Technology Data Exchange (ETDEWEB)

    De Maria, Giovanni Luigi [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Porto, Italo, E-mail: italo.porto@gmail.com [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Interventional Cardiology Unit, San Donato Hospital, Arezzo (Italy); Burzotta, Francesco; Brancati, Marta Francesca; Trani, Carlo; Pirozzolo, Giancarlo; Leone, Antonio Maria; Niccoli, Giampaolo [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy); Prati, Francesco [Department of Interventional Cardiology, San Giovanni Hospital, Rome (Italy); Crea, Filippo [Institute of Cardiology, Catholic University of the Sacred Heart, Rome (Italy)

    2015-01-15

    Background: Endothelialisation is a crucial event after percutaneous coronary intervention (PCI). Endothelial progenitor cells (EPCs) are bone marrow derived elements with reparative properties. We aimed to assess the relationship between circulating EPC levels and stent neointimal hyperplasia (NIH) using frequency domain optical coherence tomography (FD-OCT). Methods: Patients undergoing elective PCI to native vessels and randomised to bare metal stent (BMS) alone versus BMS plus drug coated balloon (DCB) were included. At six months, angiographic follow-up and FD-OCT were performed to measure percentage neointimal hyperplasia volume obstruction (%NIHV), and percentage of uncovered stent struts (%US). Venous blood samples were obtained before the procedure and at six months to detect CD34+CD45dimKDR + EPC levels. Results: Twenty patients were enrolled. A significant relationship was observed between baseline EPC levels and %NIHV (R: 0.63, p: 0.03) and %US (R: − 0.56, p: 0.01) at follow-up. Both EPC levels and DCB use were independently related to %NIHV (β: 0.55; p < 0.001 and β: − 0.51; p: 0.001, respectively), while only EPC levels were independently associated to %US (β: − 0.52; p: 0.01). Higher %NIHV (p: 0.004) and lower %US (p: 0.005) were observed in patients with stable or increasing EPC level. Conclusion: Our study shows a relationship between EPC levels and stent strut coverage, supporting a dual role for these cells in favouring stent endothelialisation but also NIH growth. - Highlights: • Substudy of IN-PACT CORO trial comparing, by adoption of optical coherence tomography, the amount of neointimal growth and stent struts coverage at six months of follow up, in elective patients randomised to conventional PCI with bare metal stent implantation (BMS group) or to stent implantation with pre or postdilation with a drug coated balloon (BMS + DCB group) • Lower neointimal regrowth observed in BMS + DCB group • First in vivo demonstration that

  19. 3-D Lagrangian-based investigations of the time-dependent cloud cavitating flows around a Clark-Y hydrofoil with special emphasis on shedding process analysis

    Science.gov (United States)

    Cheng, Huai-yu; Long, Xin-ping; Ji, Bin; Liu, Qi; Bai, Xiao-rui

    2018-02-01

    In the present paper, the unsteady cavitating flow around a 3-D Clark-Y hydrofoil is numerically investigated with the filter-based density correction model (FBDCM), a turbulence model and the Zwart-Gerber-Belamri (ZGB) cavitation model. A reasonable agreement is obtained between the numerical and experimental results. To study the complex flow structures more straightforwardly, a 3-D Lagrangian technology is developed, which can provide the particle tracks and the 3-D Lagrangian coherent structures (LCSs). Combined with the traditional methods based on the Eulerian viewpoint, this technology is used to analyze the attached cavity evolution and the re-entrant jet behavior in detail. At stage I, the collapse of the previous shedding cavity and the growth of a new attached cavity, the significant influence of the collapse both on the suction and pressure sides are captured quite well by the 3-D LCSs, which is underestimated by the traditional methods like the iso-surface of Q-criteria. As a kind of special LCSs, the arching LCSs are observed in the wake, induced by the counter-rotating vortexes. At stage II, with the development of the re-entrant jet, the influence of the cavitation on the pressure side is still not negligible. And with this 3-D Lagrangian technology, the tracks of the re-entrant jet are visualized clearly, moving from the trailing edge to the leading edge. Finally, at stage III, the re-entrant jet collides with the mainstream and finally induces the shedding. The cavitation evolution and the re-entrant jet movement in the whole cycle are well visualized with the 3-D Lagrangian technology. Moreover, the comparison between the LCSs obtained with 2-D and 3-D Lagrangian technologies indicates the advantages of the latter. It is demonstrated that the 3-D Lagrangian technology is a promising tool in the investigation of complex cavitating flows.

  20. Tip-leakage cavitation in the clearance of a 2D hydrofoil with fillets: high-speed visualization and PIV/PTV measurements

    Science.gov (United States)

    Zapryagaev, Ivan I.; Timoshevskiy, Mikhail V.; Pervunin, Konstantin S.

    2017-09-01

    Tip-clearance cavitation is one of the most aggressive forms of cavitation as it can cause surface erosion of hydraulic machinery elements and, as a result, their fatigue damage and disturb designed operating conditions. At present, the literature lacks for detailed experimental data on the inception and development of this type of cavitation at various flow conditions. In the paper, a tip-leakage cavitation occurring in the clearance between an end face of a 2D hydrofoil (a scaled-down model of guide vanes (GV) of a Francis turbine) and a transparent wall of the test section was studied. The experiments were carried out for different cavitating regimes on the cavitation number and two attack angles of 3° and 9°, with the gap size (tip clearance width) varied in the range from 0.4 to 0.8 mm. In order to determine the cavitation inception conditions and investigate the dynamics of the tip-leakage cavitation, a high-speed visualization was applied. A modified PIV/PTV technique with a diverging laser beam instead of a laser light sheet was used to measure the mean velocity distributions within the gap. It was shown that the cavitation pattern on the suction side of the GV model impacts the dynamics of the leakage flow in the gap but does not affect the sheet cavity formed close to the foil leading edge in the clearance as well as its size and dynamics. When the gap size is increased, the tip-leakage cavitation initiates at higher cavitation numbers or, in other words, conditions for the cavitation occurrence become more favorable.

  1. Management of resistant distal femur non-unions with allograft strut and autografts combined with osteosynthesis in a series of 22 patients.

    Science.gov (United States)

    Kanakeshwar, Raja Bhaskara; Jayaramaraju, Dheenadhayalan; Agraharam, Devendra; Rajasekaran, Shanmuganathan

    2017-08-01

    Challenges to the surgeon in managing cases of resistant non-union of the distal femur include poor bone stock, disuse osteopenia and joint contractures. Procedures varying from simple bone grafting to megaprosthesis revision have been described. We successfully managed such cases using our technique of combining cortical allograft struts to augment the defect in the femoral condyle coupled with autogenous iliac crest bone grafting and locking plate osteosynthesis. Between April 2012 and May 2014, 22 patients who presented with resistant nonunions of the distal femur following initial surgery were managed using this technique. Cortical allograft struts were taken from the tissue bank of our institution. All patients were followed up post operatively and their time to union was noted. Functional outcome was calculated using LEFS (Lower extremity functional score). The average follow up of all our patients was 24 months. All patients went on to achieve complete bony union. The average union time was 6.2 months (5 to 8 months). One patient who was a diabetic had superficial infection post operatively which was treated successfully with IV antibiotics. Average knee flexion was 110 degrees (80 to 130 degrees). The mean LEFS score was 72 (59 to 79). Combing a locking plate fixation with the bone grafting technique of using an allograft strut to support the metaphyseal medial bone defect and autografts gives a good union and a good functional outcome in the management of resistant non-unions of the distal femur by enhancing the biology and providing a good structural support to the distal femur. © 2017 Elsevier Ltd. All rights reserved.

  2. Investigation on Selective Laser Melting AlSi10Mg Cellular Lattice Strut: Molten Pool Morphology, Surface Roughness and Dimensional Accuracy

    Directory of Open Access Journals (Sweden)

    Xuesong Han

    2018-03-01

    Full Text Available AlSi10Mg inclined struts with angle of 45° were fabricated by selective laser melting (SLM using different scanning speed and hatch spacing to gain insight into the evolution of the molten pool morphology, surface roughness, and dimensional accuracy. The results show that the average width and depth of the molten pool, the lower surface roughness and dimensional deviation decrease with the increase of scanning speed and hatch spacing. The upper surface roughness is found to be almost constant under different processing parameters. The width and depth of the molten pool on powder-supported zone are larger than that of the molten pool on the solid-supported zone, while the width changes more significantly than that of depth. However, if the scanning speed is high enough, the width and depth of the molten pool and the lower surface roughness almost keep constant as the density is still high. Therefore, high dimensional accuracy and density as well as good surface quality can be achieved simultaneously by using high scanning speed during SLMed cellular lattice strut.

  3. Investigation on Selective Laser Melting AlSi10Mg Cellular Lattice Strut: Molten Pool Morphology, Surface Roughness and Dimensional Accuracy.

    Science.gov (United States)

    Han, Xuesong; Zhu, Haihong; Nie, Xiaojia; Wang, Guoqing; Zeng, Xiaoyan

    2018-03-07

    AlSi10Mg inclined struts with angle of 45° were fabricated by selective laser melting (SLM) using different scanning speed and hatch spacing to gain insight into the evolution of the molten pool morphology, surface roughness, and dimensional accuracy. The results show that the average width and depth of the molten pool, the lower surface roughness and dimensional deviation decrease with the increase of scanning speed and hatch spacing. The upper surface roughness is found to be almost constant under different processing parameters. The width and depth of the molten pool on powder-supported zone are larger than that of the molten pool on the solid-supported zone, while the width changes more significantly than that of depth. However, if the scanning speed is high enough, the width and depth of the molten pool and the lower surface roughness almost keep constant as the density is still high. Therefore, high dimensional accuracy and density as well as good surface quality can be achieved simultaneously by using high scanning speed during SLMed cellular lattice strut.

  4. Data Presentation of Force Characteristics of Several Engine-strut-body Configurations at Mach Numbers of 1.8 and 2.0 / Robert T. Madden and Emil J. Kremzier

    Science.gov (United States)

    Madden, Robert T; Kremzier, Emil J

    1951-01-01

    Investigation to determine lift, drag, and pitching-moment characteristics of several engine-strut-body combinations was conducted over range of angles of attack from 0 degrees to 10 degrees at Mach numbers of 1.8 and 2.0. The average Reynolds number based on body length was 28x106. Data are presented without analysis and indicate decreases in minimum drag and lift curve slope with decreasing in minimum drag and lift curve slope with decreasing strut length. Decreases in minimum drag also noted with rear-ward movement of engines.

  5. Serial optical coherence tomography assessment of malapposed struts after everolimus-eluting stent implantation. A subanalysis from the HEAL-EES study

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, Kohki [Cardiology Department, Cardiovascular Institute, Hospital Clínic, Institut d' Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona (Spain); Otsuki, Shuji [Division of Cardiology, Teikyo University Hospital, Tokyo (Japan); Giacchi, Giuseppe; Ortega-Paz, Luis [Cardiology Department, Cardiovascular Institute, Hospital Clínic, Institut d' Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona (Spain); Shiratori, Yoshitaka [Division of Cardiology, Teikyo University Hospital, Tokyo (Japan); Freixa, Xavier; Martín-Yuste, Victoria; Masotti, Mónica; Sabaté, Manel [Cardiology Department, Cardiovascular Institute, Hospital Clínic, Institut d' Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona (Spain); Brugaletta, Salvatore, E-mail: sabrugal@clinic.ub.es [Cardiology Department, Cardiovascular Institute, Hospital Clínic, Institut d' Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona (Spain)

    2017-01-15

    Background: Incomplete stent apposition (ISA) is related to stent thrombosis, which is a serious adverse event. We aim to assess the time-course of ISA after 2nd generation everolimus-eluting stent (EES) implantation. Methods: In HEAL-EES study, we enrolled 36 patients who underwent percutaneous coronary intervention (PCI) with EES. OCT imaging was performed at baseline and follow-up. Patients were randomized 1:1:1 into 3 groups according to the time in which follow-up was performed: group A (6-month), group B (9-month), and group C (12-month). In this subanalysis, patients who had ISA segments at baseline and/or follow-up OCT were analyzed. Result: At baseline, among 41 lesions in 36 patients, 20 lesions in 18 patients had ISA segments and were analyzed. At baseline, there were 3.0% ISA struts in group A (n = 8), 2.8% in group B (n = 4), and 4.5% in group C (n = 8). At follow-up, ISA struts were present in 0.09%, 0.16% and 0.64%; respectively in groups A, B, and C. At follow-up, there was a significant decrease in the frequency of ISA: group A 3.0% vs. 0.09% (p < 0.001), group B 2.8% vs. 0.16% (p < 0.001), and group C 4.5% vs. 0.64% (p < 0.001). In group A, there was one late acquired ISA at follow-up. Conclusions: In patients undergoing 2nd generation EES implantation, area of acute ISA assessed by OCT, was almost resolved at 6-month follow-up. - Highlights: • Time-course of incomplete stent apposition of everolimus-eluting stent was assessed. • Serial optical coherence tomography images at baseline and follow-up were evaluated. • Acute incomplete stent apposition was almost resolved as early as at 6 months.

  6. The challenge of non-union in subtrochanteric fractures with breakage of intramedullary nail: evaluation of outcomes in surgery revision with angled blade plate and allograft bone strut.

    Science.gov (United States)

    Rollo, G; Tartaglia, N; Falzarano, G; Pichierri, P; Stasi, A; Medici, A; Meccariello, L

    2017-12-01

    Subtrochanteric fractures have a bimodal age distribution. They usually require open reduction and internal fixation. Closed reduction and intramedullary nail fixation rate are increased for this type of fracture. As a result, the hardware breakage and non-union rate is high among such patients. Our purpose is to evaluate the outcomes of the role of blade plate and bone strut allograft in the management of subtrochanteric non-union by femoral nailing. We reported a group of 22 patients with subtrochanteric non-union, associated with breakage of the intramedullary nail with medial femoral allograft bone and lateral blade plate and wire (PS) s; and a group of 13 patients with subtrochanteric non-union, associated with breakage of the intramedullary nail treated with lateral blade plate and screws (CG). The chosen criteria to evaluate the two group during the clinical and radiological follow-up were the quality of life, measured by The Short Form (12) Health Survey (SF-12), the hip function and quality of life related to it, measured by the Harris Hip Score (HHS), bone healing, measured by Radiographic Union Score (RUS) by XR and CT at 1 year after the surgery, and postoperative complications. The evaluation endpoint was set at 12 months. The Bone healing measured by RUS occurred and also the full recovery before the first trauma measured by SF-12 and HHS are better in PS group. We only had three unimportant complications in PS while four breakage hardware in CG. We conclude that in complicated non-unions, the use of blade plate and bone strut allograft has a definite positive role in the management of such cases.

  7. Solving the Issue of Restenosis After Stenting of Intracranial Stenoses: Experience with Two Thin-Strut Drug-Eluting Stents (DES)—Taxus Element™ and Resolute Integrity™

    Energy Technology Data Exchange (ETDEWEB)

    Kurre, Wiebke, E-mail: wiebke.kurre@gmx.de; Aguilar-Pérez, Marta [Klinikum Stuttgart, Klinik für Diagnostische und Interventionelle Neuroradiologie (Germany); Fischer, Sebastian [Universitätsklinikum Knappschaftskrankenhaus Bochum GmbH, Institut für Diagnostische und Interventionelle Radiologie, Neuroradiologie und Nuklearmedizin (Germany); Arnold, Guy [Klinikverbund Südwest, Klinikum Sindelfingen, Klinik für Neurologie (Germany); Schmid, Elisabeth; Bäzner, Hansjörg [Klinikum Stuttgart, Klinik für Neurologie (Germany); Henkes, Hans [Klinikum Stuttgart, Klinik für Diagnostische und Interventionelle Neuroradiologie (Germany)

    2015-06-15

    PurposeThin-strut, flexible DES are suitable for intracranial stenting and may improve long-term vessel patency. The purpose of this study was to report our experience with two new-generation DES for the treatment of intracranial atherosclerotic disease.Patients and MethodsWe retrospectively reviewed all patients treated with Taxus Element™ or Resolute Integrity™ stent for an intracranial atherosclerotic stenosis between March 2011 and August 2013. Technical success was defined as the ability to deploy the device at the desired location and reduce the degree of stenosis below 50 %. All procedure-related strokes were recorded. Control angiography was scheduled after 6 weeks, 3, 6, and 12 months and yearly thereafter. A luminal narrowing ≥50 % was regarded as a restenosis. Stroke recurrence in the territory of the treated artery was reported.ResultsIn the defined period we treated 101 patients harboring 117 intracranial stenoses. The procedure was successful in 100 (85.5 %) lesions. Procedure-related strokes occurred in 10 (9.9 %) patients with a permanent morbidity in 3 (3.0 %). Follow-up angiography was available for 83 of 100 (83.0 %) successfully treated lesions with an average of 355 days (IQR 153–482 days). Three (3.6 %) asymptomatic restenoses were detected. All occurred after treatment with Resolute Integrity™, none after Taxus Element™ (p = 0.059). New strokes in the territory of the treated artery were encountered in 2 (2.6 %) occasions.ConclusionThin-strut DES improve long-term patency and reduce the risk of subsequent stroke. Differences between devices may exist. Feasibility is comparable to bare-metal balloon-mounted stents and procedure-related strokes occurred within the expected range.

  8. Impact of Strut Width in Periprocedural Myocardial Infarction: A Propensity-Matched Comparison Between Bioresorbable Scaffolds and the First-Generation Sirolimus-Eluting Stent.

    Science.gov (United States)

    Kawamoto, Hiroyoshi; Panoulas, Vasileios F; Sato, Katsumasa; Miyazaki, Tadashi; Naganuma, Toru; Sticchi, Alessandro; Figini, Filippo; Latib, Azeem; Chieffo, Alaide; Carlino, Mauro; Montorfano, Matteo; Colombo, Antonio

    2015-06-01

    This study aimed to assess the clinical impact of strut width (evaluated by abluminal strut surface area [ASSA]) on periprocedural myocardial infarction (PMI) and clinical outcomes in patients treated with bioresorbable scaffolds (BRS) versus first-generation sirolimus-eluting stents (SES). To date, there are no reports on the impact of ASSA on PMI and clinical outcomes. We compared the impact of ASSA on outcomes and PMI in propensity-matched patients treated with BRS and SES. The primary outcome was the incidence of major adverse cardiac events (MACE), defined as the combination of all-cause mortality, follow-up myocardial infarction, and target vessel revascularization, at 30-days and 1-year follow-ups. The secondary endpoint was the incidence of PMI. After propensity-matched analysis, 499 patients (147 BRS patients vs. 352 SES patients) were evaluated. Mean ASSA was higher in patients treated with BRS versus SES (BRS: 132.3 ± 76.7 mm(2) vs. SES: 67.6 ± 48.4 mm(2), p BRS: 0% vs. SES: 1.4%, p = 0.16, and 1-year MACE: BRS: 15.7% vs. SES: 11.4%, p = 0.67). The incidence of PMI was significantly higher in the BRS group (BRS: 13.1% vs. SES: 7.5%, p = 0.05). Multivariable analyses indicated that treatment of left anterior descending artery and ASSA were independent predictors of PMI. BRS implantation, compared with SES implantation, was associated with a higher incidence of PMI. MACE at 30 days and 1 year were not significantly different. Left anterior descending artery percutaneous coronary intervention and ASSA were independent predictors of PMI. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  9. Intra- and interobserver reliability and intra-catheter reproducibility using frequency domain optical coherence tomography for the evaluation of morphometric stent parameters and qualitative assessment of stent strut coverage

    International Nuclear Information System (INIS)

    Antonsen, Lisbeth; Thayssen, Per; Junker, Anders; Veien, Karsten Tange; Hansen, Henrik Steen; Hansen, Knud Nørregaard; Hougaard, Mikkel; Jensen, Lisette Okkels

    2015-01-01

    Purpose: Frequency-domain optical coherence tomography (FD-OCT) is a high-resolution imaging tool (~ 10–15 μm), which enables near-histological in-vivo images of the coronary vessel wall. The use of the technique is increasing, both for research- and clinical purposes. This study sought to investigate the intra- and interobserver reliability, as well as the intra-catheter reproducibility of quantitative FD-OCT-assessment of morphometric stent parameters and qualitative FD-OCT-evaluation of strut coverage in 10 randomly selected 6-month follow-up Nobori® biolimus-eluting stents (N-BESs). Methods: Ten N-BESs (213 cross sectional areas (CSAs) and 1897 struts) imaged with OCT 6 months post-implantation were randomly selected and analyzed by 2 experienced analysts, and the same 10 N-BESs were analyzed by one of the analysts 3 months later. Further, 2 consecutive pullbacks randomly performed in another 10 N-BESs (219 CSAs and 1860 struts) were independently assessed by one of the analysts. Results: The intraobserver variability with regard to relative difference of mean luminal area and mean stent area at the CSA-level was very low: 0.1% ± 1.4% and 0.5% ± 3.2%. Interobserver variability also proved to be low: − 2.1% ± 3.3% and 2.1% ± 4.6%, and moreover, very restricted intra-catheter variation was observed: 0.02% ± 6.8% and − 0.18% ± 5.2%. The intraobserver-, interobserver- and intra-catheter reliability for the qualitative evaluation of strut coverage was found to be: kappa (κ) = 0.91 (95% confidence interval (CI): 0.88–0.93, p < 0.01), κ = 0.88 (95% CI: 0.85–0.91, p < 0.01), and κ = 0.73 (95% CI: 0.68–0.78, p < 0.01), respectively. Conclusions: FD-OCT is a reproducible and reliable imaging tool for quantitative evaluation of stented coronary segments, and for qualitative assessment of strut coverage. - Highlights: • Frequency-domain optical coherence tomography (FD-OCT) is increasingly adopted in the catherization laboratories. • This

  10. Marine Hydrokinetic (MHK) Energy Conversion Research at UNH: From Fundamental Studies of Hydrofoil Sections, to Moderate Reynolds Number Turbine Tests in a Tow Tank, to Open Water Deployments at Tidal Energy Test Sites (Invited)

    Science.gov (United States)

    Wosnik, M.; Bachant, P.; Nedyalkov, I.; Rowell, M.; Dufresne, N.; Lyon, V.

    2013-12-01

    We report on research related to MHK turbines at the Center for Ocean Renewable Energy (CORE) at the University of New Hampshire (UNH). The research projects span varies scales, levels of complexity and environments - from fundamental studies of hydrofoil sections in a high speed water tunnel, to moderate Reynolds number turbine tests with inflow and wake studies in a large cross-section tow tank, to deployments of highly instrumented process models at tidal energy test sites in New England. A concerted effort over the past few years has brought significant new research infrastructure for marine hydrokinetic energy conversion online at UNH-CORE. It includes: a high-speed cavitation tunnel with independent control of velocity and pressure; a highly accurate tow mechanism, turbine test bed and wake traversing system for the 3.7m x 2.4m cross-section UNH tow tank; a 10.7m x 3.0m tidal energy test platform which can accommodate turbines up to 1.5m in diameter, for deployments at the UNH-CORE Tidal Energy Test Site in Great Bay Estuary, NH, a sheltered 'nursery site' suitable for intermediate scale tidal energy conversion device testing with peak currents typically above 2 m/s during each tidal cycle. Further, a large boundary layer wind tunnel, the new UNH Flow Physics Facility (W6.0m x H2.7m xL72m) is being used for detailed turbine wake studies, producing data and insight also applicable to MHK turbines in low Froude number deployments. Bi-directional hydrofoils, which perform equally well in either flow direction and could avoid the use of complex and maintenance-intensive yaw or blade pitch mechanisms, are being investigated theoretically, numerically and experimentally. For selected candidate shapes lift, drag, wake, and cavitation inception/desinence are measured. When combined with a cavitation inception model for MHK turbines, this information can be used to prescribe turbine design/operational parameters. Experiments were performed with a 1m diameter and 1m

  11. Initial and mid-term results of a 4F compatible self-expanding low strut profile nitinol stent in the superficial femoral artery

    Energy Technology Data Exchange (ETDEWEB)

    Muehlenbruch, G.; Brock, H.; Das, M.; Hohl, C.; Mahnken, A.H.; Wildberger, J.; Guenther, R.W. [Universitaetsklinikum der RWTH Aachen (Germany). Klinik fuer Radiologische Diagnostik; Haage, P. [Universitaetsklinik Witten/Herdecke (Germany). HELIOS-Klinikum Wuppertal, Klinik fuer Diagnostische und Interventionelle Radiologie

    2007-07-15

    Purpose: To evaluate the initial and mid-term results of a new self-expanding low strut profile nitinol stent for treatment of atherosclerotic lesions stenoses and occlusions in the superficial femoral artery (SFA). Materials and Methods: In 8 patients (4 male, 4 female, mean age 74.8 {+-} 8.8 years) with SFA lesions and non-satisfying results after PTA treatment alone, 10 self-expanding nitinol Xpert stents were deployed via a 4 F sheath. Stent characteristics and handling were graded by the interventionalist. Fontaine classification, duplex flow measurements and ankle brachial index (ABI) at rest and stress were taken prior and one day after stent placement. Patients were followed 3, 6 and 12 months after the procedure obtaining the same parameters at each appointment. Results: Initial stent treatment was successful in all patients. Stent handling and positioning were rated very good and safe. All patients improved clinically by at least one Fontaine stage (range before treatment: stage IIb to IV). The mean ABI at rest (stress) improved initially from 0.68 (0.70) to 1.07 (0.99). During a mean follow-up period of 8.3 months no case of clinically relevant in-stent stenosis was observed with stable values of ABI at rest and stress. (orig.)

  12. Autologous grafts of double-strut fibular cortical bone plate to treat the fractures and defects of distal femur: a case report and review of literature

    Directory of Open Access Journals (Sweden)

    CHEN Xu

    2012-02-01

    Full Text Available 【Abstract】We reported a 23-year-old man who was involved in a high-speed motorcycle accident. He sustained a closed fracture at the right distal femur. The primary fracture happened on February 2008. He underwent open reduction and internal fixation with cloverleaf plate. And one hundred days after the surgery, the proximal screws were pulled-out, but the bone union was not achieved. Treatment consisted of exchanging the cloverleaf plate with a locking compression plate and using an auto-iliac bone graft to fill the nonunion gap. In July 2009, the patient had a sharp pain in the right lower limb. The X-ray revealed that the plate implanted last year was broken, causing a nonunion at the fracture site. Immediately the plate and screws were removed and an intramedullary nail was inserted reversely from the distal femur as well as a 7 cm long bone from the right fibula was extracted and longitudinally split into two pieces to construct cortical bone plates. Then we placed them laterally and medially to fracture site, drilled two holes respectively, and fastened them with suture. We carried on auto-iliac bone grafting with the nonunion bone grafts. The follow-up at 15 months after operation showed that the treatment was successful, X-ray confirmed that there was no rotation and no angular or short deformity. We briefly reviewed the literature regarding such an unusual presentation and discussed in details the possible etiology and the advantages of autologous double-strut fibular grafts to cope with such an intractable situation. Key words: Femur; Transplantation, autologous; Bone screws

  13. Sensitivity and Trade-Off Analysis of Wave Making Resistance and Stability of Small Water Plane Area Trimarans

    Science.gov (United States)

    2007-09-01

    for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing...data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden...struts for two or three strut configurations are assumed to be identical vertical elliptical hydrofoils with the same length and thickness. The

  14. Development of a dynamic in vitro model of a stented blood vessel to evaluate the effects of stent strut material selection and surface coating on smooth muscle cell response

    Science.gov (United States)

    Winn, Bradley Huegh

    formation of this new tissue, primarily consisting of VSMCs of the synthetic phenotype and their subsequent extracellular matrix, is the sole causation of in-stent restenosis since the stent serves to prevent elastic recoil and negative remodeling. This doctoral research program is focused on endovascular stent biomaterials science and engineering. Overall, this doctoral project is founded on the hypothesis that smooth muscle cell hyperplasia, as an important causative factor for vascular restenosis following endovascular stent deployment, is triggered by the various effects of stent strut contact on the vessel wall including contact forces and material biocompatibility. In this program, a dynamic in vitro model of a stented blood vessel aimed at evaluating the effect of stent strut material selection, and surface coating on smooth muscle cell response was developed. The in vitro stented artery model was validated through the proliferation of VSMC in contact with stent struts. Additionally, it was demonstrated that, with respect to known biocompatible materials such as Nitinol and 316L stainless steel, DNA synthesis and alpha-actin expression, as indicators of VSMC phenotype, are independent of stent material composition. Furthermore, hydroxyapatite was shown to be a biocompatible stent surface coating with acceptable post-strain integrity. This coating was shown in a feasibility study to be capable of serving as a favorable drug delivery platform able to reliably deliver locally therapeutic doses of bisphosphonates, such as alendronate, to control VSMC proliferation in an in vitro model of a stented blood vessel. This stent coating/drug combination may be effective for reducing restenosis as a result of VSMC hyperplasia in vivo.

  15. Strut your SmartWay Stuff

    Science.gov (United States)

    This EPA presentation provides information on the SmartWay Transport Partnership Program, including SW brand market research results, program success, partner participation, logo usage, and available promotional and publicity resources.

  16. Stretching the HM200 series SES

    Science.gov (United States)

    Tattersall, E. G.; Gee, N. I.

    The HM200 series SESs are discussed and compared with respect to design specifications, cost, and performance specifications such as speed loss in waves, and vertical accelerations. Structural modifications for the HM221, demonstrating a capacity increases of 33 percent over the HM218 for only a 22 percent increase in first cost, include small increases on bottom shell thickness and a 30 percent lift power increase (by using the turbo charged version of the HM218 naturally aspirated engine). It is shown that the HM200 series requires about half the HP and fuel consumption of the catamaran, and about 30 percent less than the surface piercing hydrofoils, in the same speed range.

  17. Numerical study of hydrofoil tip vortex fluid field

    Directory of Open Access Journals (Sweden)

    PU Jijun

    2017-01-01

    Full Text Available Three different models,k-ω,DES and LES,are conducted in the analysis of the tip vortex flow field. In order to reduce the discrete error induced by the grid,mesh refinement is applied to the area of the tip vortex core in numerical simulations. The axis and tangential velocities of the tip vortex flow field with no cavitation are calculated,and the calculated velocities agree well with the experimental results. On the basis of this process,the influence of vortex roll-up on the tip vortex pressure filed is discussed,and bubble static equilibrium is proposed by which the tip vortex cavitation inception number is computed.

  18. Hydrodynamic studies on two wiggling hydrofoils in an oblique arrangement

    Science.gov (United States)

    Lin, Xingjian; He, Guoyi; He, Xinyi; Wang, Qi; Chen, Longsheng

    2017-12-01

    The propulsive performance of an oblique school of fish is numerically studied using an immersed boundary technique. The effect of the spacing and wiggling phase on the hydrodynamics of the system is investigated. The hydrodynamics of the system is deeply affected by the spacing between each fish in the school. When the horizontal separation is smaller than the length of the fish body, the downstream fish exhibits a larger thrust coefficient and greater propulsive efficiency than the isolated fish. However, the corresponding values for the upstream fish are smaller. The opposite behavior occurs when the horizontal separation increases beyond the length of fish body. The propulsive performance of the entire oblique school of fish can be substantially enhanced when the separations are optimized.

  19. An Integrated Hydrofoil and Propeller Design Tool for the Window (Trademark) Environment

    Science.gov (United States)

    1996-06-01

    return msg.wParam; p 4 When viewed for the first time, and particularly without the benefit of experience with the C programming language, the logic...origin~jrpbhx+270*BANGINUIjIOfl* width640.); pointuljy - I(intX(orgn- gmo -rpby+((max -thick-BTHKINiI[OI)/ delta dzck)*40)*heigbt43O.0); Euip~eBaMdediniDC...DiIgcbme) //ucrqp tM e rig umin whil (sexlcharil3&A xwclbat10) mexiche - gec(blade); I/red W. the anUmber at components hcauqbladetlW,&LDEV); //$ crop the

  20. Effect of wavelength of fish-like undulation of a hydrofoil in a free ...

    Indian Academy of Sciences (India)

    Thekkethil Namshad

    separately for undulating and pitching fishes/foil. ... the low wavelength case undulating Пk ¼ 0.8ч foil is different from the mechanism for the high wavelength pitching foil. .... where X is the non-dimensional distance from the head and k is the ...

  1. Measurement of Surface Strains from a Composite Hydrofoil using Fibre Bragg Grating Sensing Arrays

    Science.gov (United States)

    2015-07-01

    and crazing along the leading edge up to mid span length. A CNC waterjet cutter (TECHNI model TJ3000-x2) was used to cut a transverse section out of...UNCLASSIFIED DST-Group-TN-1438 UNCLASSIFIED 10 A cutting template with the same dimensions as the channel width is used to cut strips of the Redux with...b) Figure 10: Photos showing the cutting of Redux strips to match channel width

  2. MVC Design Pattern for the multi framework distributed applications using XML, spring and struts framework

    OpenAIRE

    Praveen Gupta,; Prof. M.C. Govil

    2010-01-01

    The model view controller (MVC) is a fundamental design pattern for the separation between user interface logic and business logic. Since applications are very large in size these days and the MVC designpattern can weak the coupling among the different application tiers of application. this paper presents a web application framework based on MVC in J2EE platform, and extends it with XML so that the framework is more flexible, expansible and easy to maintain. This is a multi tier system includ...

  3. Anterior cervical debridement and strut-grafting for osteomyelitis of the cervical spine.

    Science.gov (United States)

    Stone, J L; Cybulski, G R; Rodriguez, J; Gryfinski, M E; Kant, R

    1989-06-01

    A retrospective review of the surgical experience in treating 18 patients with osteomyelitis of the cervical spine is reported. The patients ranged in age from 20 to 60 years and all complained of neck pain upon admission. Ten patients had a prior history of intravenous drug abuse, three had previously suffered penetrating injuries of the neck, and one had an extraspinal site of osteomyelitis. Bacteria were isolated in 13 cases and tuberculosis in three. Neurological abnormalities were present in over one-half of the patients, consisting of myelopathy (nine cases) or radiculopathy (four cases). Plain cervical spine films and polytomography demonstrated vertebral and end-plate destruction, spinal instability, and increased paravertebral soft-tissue shadow in all cases. Computerized tomography and, more recently, magnetic resonance imaging have proven helpful in detecting bone involvement and the presence of epidural extension associated with cervical osteomyelitis. The risk of vertebral body collapse, kyphosis, and myelopathy in the osteomyelitic cervical spine has standardized the management of this problem in this institution to consist of skeletal traction, needle aspiration or blood culture for organism identification, anterior cervical debridement, autogenous iliac graft fusion, and intravenous administration of antibiotics. Spinal stability and neurological improvement were achieved in all 18 patients.

  4. Use of non-vascularized autologous fibula strut graft in the treatment ...

    African Journals Online (AJOL)

    Background: Fractures resulting in segmental bone loss challenge the orthopedic surgeon. Orthopedic surgeons in developed countries have the option of choosing vascularized bone transfers, bone transport, allogenic bone grafts, bone graft substitutes and several other means to treat such conditions. In developing ...

  5. Development of a safe TRU transportation system (STRUTS) for DOE's TRU waste

    International Nuclear Information System (INIS)

    Edling, D.A.; Hopkins, D.R.; Walls, H.C.

    1978-01-01

    Transportation, the link between TRU waste generation and WIPP (Waste Isolation Pilot Project) and a vital link in the overall TRU waste management program, must be addressed. The program must have many facets: ensuring public and carrier acceptance, formation of a functional and current transportation data base, systems integration, maximum utilization of existing technology, and effective implementation and integration of the transport system into current and planned operational systems

  6. Use of non-vascularized autologous fibula strut graft in the treatment ...

    African Journals Online (AJOL)

    Orthopedic surgeons in developed countries have the option of choosing vascularized bone transfers, bone transport, allogenic bone grafts, bone graft substitutes ... tissue envelope assessment, neurological examination, and debridement under general anesthesia with fracture stabilization with external fixators or casts.

  7. Strut Attachment System for In-Space Robotic Assembly, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The size of space systems is currently limited to payload envelopes of existing launch vehicles. Due to this and the customized nature of satellites, existing space...

  8. Strut Attachment System for In-Space Robotic Assembly, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The size of space systems is currently limited to payload envelopes of existing launch vehicles. Due to this and the customized nature of satellites, existing space...

  9. Variable Geometry Aircraft Wing Supported by Struts And/Or Trusses

    Science.gov (United States)

    Melton, John E. (Inventor); Dudley, Michael R. (Inventor)

    2016-01-01

    The present invention provides an aircraft having variable airframe geometry for accommodating efficient flight. The aircraft includes an elongated fuselage, an oblique wing pivotally connected with said fuselage, a wing pivoting mechanism connected with said oblique wing and said fuselage, and a brace operably connected between said oblique wing and said fuselage. The present invention also provides an aircraft having an elongated fuselage, an oblique wing pivotally connected with said fuselage, a wing pivoting mechanism connected with said oblique wing and said fuselage, a propulsion system pivotally connected with said oblique wing, and a brace operably connected between said propulsion system and said fuselage.

  10. Flow Control Technology

    Science.gov (United States)

    2010-07-01

    cm. In a similar fashion, the blades are exchangeable. For the results presented here, a blade chord of 50mm with a symmetric NACA 0015 hydrofoil ...Skogsberg and Roland [3]. Each propeller blade assembly is composed of a mounting bracket (1), Hydrofoil Shaft Bracket (2), Blade Servo (3), NACA 0015... Hydrofoil (4), Hydrofoil Shaft Connection (5), and Motor Bracket (6). This set-up can be seen in schematics of Figure 14. Blade 3’s Hydrofoil Shaft

  11. Effect of Drag-Reducing Polymer Injection on the Lift and Drag of a Two- Dimensional Hydrofoil

    Science.gov (United States)

    1974-09-01

    computer progrmming and equipment technology need be required for problem set-up and solution. 2. Simulation preparation and set-up to be free from...34Application of General-Purpose Simulation to the Navy Problems, Research and Technology Conference on Optimization/Statistics Simulation and Information...1973 238A Helth Care Dacilities Plming November 2, 1973 Lxtnsion Courses: X461POR Product Development October 1967, Noveber 1968 X407.1 Construction

  12. Determination of frequencies of oscillations of cloud cavitation on a 2-D hydrofoil from high-speed camera observations

    Czech Academy of Sciences Publication Activity Database

    Zima, Patrik; Fürst, T.; Sedlář, M.; Komárek, M.; Huzlík, R.

    2016-01-01

    Roč. 28, č. 3 (2016), s. 369-378 ISSN 1001-6058 R&D Projects: GA ČR GA13-23550S Institutional support: RVO:61388998 Keywords : unsteady cavitation * oscillation frequency * high-speed camera observation Subject RIV: BK - Fluid Dynamics Impact factor: 1.174, year: 2016 http://ac.els-cdn.com/S1001605816606406/1-s2.0-S1001605816606406-main.pdf?_tid=dee3b8f4-4a62-11e6-9d83-00000aacb361&acdnat=1468570098_ce8b727c766e0f96ee20d505e7058102

  13. Jet grout strut for deep station boxes of the north/south metro line Amsterdam : Design and back analysis

    NARCIS (Netherlands)

    Delfgaauw, S.; Buykx, S.M.; Bosch, J.W.

    2009-01-01

    The new North/South metro line in Amsterdam contains several stations, some of which with an excavation depth of 30 m below surface. The design of these station boxes is very much determined by the adjacent historic buildings, high water table and the relatively soft soil. A lot of effort is put

  14. Direct intrahepatic portocaval shunt creation via the inter-strut space of the inferior vena cava stent

    International Nuclear Information System (INIS)

    Tsauo, J.; Yu, Y.; Luo, X.; Wang, Z.; Liu, L.; Li, X.

    2014-01-01

    Highlights: • The feasibility of DIPS creation through an IVC stent was investigated. • DIPS creation through the IVC stent was successful in all four patients. • DIPS creation through the IVC stent is feasible

  15. Clinical Characteristics and Prognosis of Peri-strut Low-intensity Area Detected by Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    De-Wei Wu

    2015-01-01

    Conclusions: PLIA detected by OCT was positively correlated with higher serum lipid level, history of cerebrovascular disease and initial presentation of ACS, and negatively correlated with stent implantation time. Patients with PLIA were more likely to have UA than those with high-intensity while no significant difference was found in MACEs.

  16. A hybrid finite element analysis and evolutionary computation method for the design of lightweight lattice components with optimized strut diameter

    DEFF Research Database (Denmark)

    Salonitis, Konstantinos; Chantzis, Dimitrios; Kappatos, Vasileios

    2017-01-01

    Components incorporating lattice structures have become very popular lately due to their lightweight nature and the flexibility that additive manufacturing offers with respect to their fabrication. However, design optimization of lattice components has been addressed so far either with empirical...... approaches or with the use of topology optimization methodologies. An optimization approach utilizing multipurpose optimization algorithms has not been proposed yet. This paper presents a novel user-friendly method for the design optimization of lattice components towards weight minimization, which combines...... finite element analysis and evolutionary computation. The proposed method utilizes the cell homogenization technique in order to reduce the computational cost of the finite element analysis and a genetic algorithm in order to search for the most lightweight lattice configuration. A bracket consisting...

  17. Thermal conductivity measurement below 40 K of the CFRP tubes for the Mid-Intrared Instrument mounting struts

    DEFF Research Database (Denmark)

    Shaughnessy, B. M.; Eccleston, P.; Fereday, K. J.

    2007-01-01

    The Mid-Infrared Instrument (MIRI) is one of four instruments on the James Webb Space Telescope observatory, scheduled for launch in 2013. It must be cooled to about 7 K and is supported within the telescope’s 40 K instrument module by a hexapod of carbon fibre reinforced plastic (CFRP) tubing. T....... This article describes the measurement of cryogenic thermal conductivity of the candidate CFRP. Measured thermal conductivities were about 0.05 W/m K at a mean temperature of 10 K increasing to about 0.20 W/m K at a mean temperature of 40 K....

  18. Optimizing Noise Attenuation in Aircraft Exhaust Ducts Employing Passive and Active Absorbing Splitters and Struts, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA requires accurate numerical simulation of high bypass nacelle acoustics and the development of advanced nacelle absorption techniques to reduce engine noise...

  19. Metal-directed topological diversity of three fluorescent metal-organic frameworks based on a new tetracarboxylate strut

    KAUST Repository

    Lou, Xinhua

    2013-01-01

    Three d- or p-block metal ions based metal-organic frameworks (MOFs) were isolated by employing a new tetracarboxylate linker, featuring unusual flu, self-interpenetrated lvt and new (3,5)-c topological nets, respectively. Interesting photoluminescent properties of these solid-state materials were also observed. © 2013 The Royal Society of Chemistry.

  20. "Surveymarine" A High Speed Hydrographic Survey Platform

    National Research Council Canada - National Science Library

    Spinning, John N; Dixon, Dan G

    1969-01-01

    .... Those platforms showing the most promise are hydrofoils and sidewall hovercraft. NAVOCEANO has participated in several demonstrations of commercially available hovercraft and hydrofoils in addition to conducting a series of trials of its own...

  1. A Study of Two-Dimensional Unsteady Breaking Waves in Finite-Depth Water

    Science.gov (United States)

    2010-01-01

    1880). [8] J. H. Duncan, “An experimental investigation of breaking waves produced by a towed hydrofoil ,” Proc. R. Soc. London, Ser. A 377, 331(1981...measured the drag per unit length due to quasi-steady breaking waves generated with a submerged hydrofoil . His measurements illustrated that the... hydrofoil . Proc. R. Soc. London Ser. A 377, 331-348. DUNCAN, J. H. 1983 The breaking and non-breaking wave resistance of a two- dimensional hydrofoil . J

  2. Density Deconvolution With EPI Splines

    Science.gov (United States)

    2015-09-01

    Comparison of Deconvolution Methods . . . . . . . . . . . . . . . 28 5 High-Fidelity and Low-Fidelity Simulation Output 31 5.1 Hydrofoil Concept...46 A.3 Hydrofoil Concept . . . . . . . . . . . . . . . . . . . . . . . . 47 A.4 Notes on Computation Time...Epi-Spline Estimates . . . . . . . . . . . 28 Figure 4.3 Deconvolution Method Comparison . . . . . . . . . . . . . . . . 29 Figure 5.1 Hydrofoil

  3. A Numerical Study of Vortex Dynamics of Flexible Wing Propulsors

    Science.gov (United States)

    2009-11-23

    properties such as time dependent pressure loading, speed, free stream velocity, and local acceleration of the hydrofoil determine the instantaneous...deformation of the hydrofoil , which has effect on the propulsive characteristics of the aquatic animal. A potential flow analysis is done on the flexible... hydrofoil , to evaluate the both inertial and elastic effects on propulsive characteristics such as efficiency and thrust coefficient. Thrust

  4. Mast Wake Reduction by Shaping

    National Research Council Canada - National Science Library

    Beauchamp, Charles H

    2005-01-01

    The present invention relates to various mast shapes, in which the mast shapes minimize the production of visible, electro-optic, infrared and radar cross section wake signatures produced by water surface piercing masts...

  5. JHSS Baseline Shaft and Strut (BSS) Model 5653-3 Added Resistance and Powering and Ship Motions, Sea State 6 Random Waves and Regular Waves

    Science.gov (United States)

    2009-04-01

    r^ N- r^ t^- dddddddddd d d d d Ul u. ~"" 5 (A a> c •c > 3 to UJ cvnnmfNiO) Nif )<NtoN CM m o h~ o 2 mmmmcMcommmm in in s o re .c a...regions out of 2mm tolerance C6 K -0 177 Low Spot General Color Plots Figure C5 and Figure C6 illustrate the positive and negative deviations...different shades of blues) indicate where the model has low spots. Figure C6 has a zoomed in scale so that the localized deviations below the

  6. An Experimental Investigation of the Acoustic and Fluid Dynamic Characteristics of a Circulation-Controlled Airfoil

    Science.gov (United States)

    2011-05-13

    sound production from a hydrofoil and identified three mechanisms: (1) low frequency curvature noise associated with interaction of a turbulent...2002). 2 Technical Approach A two-dimensional, dual-slotted, elliptic circulation control airfoil based on the hydrofoil studied by Rogers...airfoil, shown in Figure 1A, is designed based on the geometry of the hydrofoil previously studied by Rogers & Donnelly (2004). The airfoil’s profile

  7. Tethered Antennas for Unmanned Underwater Vehicles

    Science.gov (United States)

    2009-04-27

    Concepts The first design (Figure 1) was based on the concept of an airfoil kite. The shape of the tow body was built around a NACA5515 hydrofoil to...Underwater Vehicles Brooke Ocean Technology (USA) Inc. 6 Figure 1: Hydrofoil Design The second design was based on that of a boat hull...communications. A sharp bow was utilized to cut through the water to reduce drag when on the surface. Like the hydrofoil design the top profile was

  8. Application of a pressure based CFD code with mass transfer model based on the Rayleigh equation for the numerical simulation of the cavitating flow around a hydrofoil with circular leading edge

    Directory of Open Access Journals (Sweden)

    Deimel Christian

    2014-03-01

    Full Text Available The most common method for simulating cavitating flows is using the governing flow equations in a form with a variable density and treats both phases as incompressible in combination with a transport equation for the vapour volume fraction. This approach is commonly referred to as volume of fluid method (VoF. To determine the transition of the liquid phase to vapour and vice versa, a relation for the mass transfer is needed. Several models exist, based on slightly differing physical assumptions, for example derivation from the dynamics of single bubbles or large bubble clusters. In our simulation, we use the model of Sauer and Schnerr which is based on the Rayleigh equation. One common problem of all mass transfer models is the use of model constants which often need to be tuned with regard to the examined problem. Furthermore, these models often overpredict the turbulent dynamic viscosity in the two-phase region which counteracts the development of transient shedding behaviour and is compensated by the modification proposed by Reboud. In the presented study, we vary the parameters of the Sauer-Schnerr model with Reboud modification that we implemented into an OpenFOAM solver to match numerical to experimental data.

  9. Joint High Speed Sealift (JHSS) Baseline Shaft & Strut (BSS) Model 5653-3: Series 2, Propeller Disk LDV Wake Survey; and Series 3, Stock Propeller Powering and Stern Flap Evaluation Experiments

    National Research Council Canada - National Science Library

    Cusanelli, Dominic S; Chesnakas, Christopher J

    2007-01-01

    ...) and Stock Propeller Powering and Stern Flap Evaluation tests (Series 3. In order to assist in the design of a propeller for the BSS hull, the nominal wakes in the inboard and outboard starboard propeller planes were measured using LDV...

  10. One-Year Outcomes in "Real-World" Patients Treated With a Thin-Strut, Platinum-Chromium, Everolimus-Eluting Stent (from the PROMUS Element Plus US Post-Approval Study [PE-Plus PAS]).

    Science.gov (United States)

    Kandzari, David E; Amjadi, Nima; Caputo, Christopher; Rowe, Steven K; Williams, Jerome; Tamboli, Hoshedar P; Christen, Thomas; Allocco, Dominic J; Dawkins, Keith D

    2016-02-15

    The PROMUS Element Plus US Post-Approval Study (PE-Plus PAS) was a prospective, open-label, multicenter, observational study designed to examine outcomes in everyday clinical practice in patients treated with everolimus-eluting, platinum-chromium PROMUS Element Plus stents at 52 centers in the United States. This is the first report of results from this large study. The primary end point of the PE-Plus PAS was 12-month cardiac death or myocardial infarction in the more restricted population of "PLATINUM-like" patients pooled from the PE-Plus PAS, PE-PROVE (PROMUS Element European post-approval study), and PLATINUM Workhorse/Small Vessel trials. Additional clinical end points were tested in the overall PE-Plus PAS patient population. Of the 2,683 patients enrolled in PE-Plus PAS, 70% were men, mean age was 64 years, 33% had diabetes, and 29% were "PLATINUM-like." Among the PLATINUM-like patients, 12-month cardiac death or myocardial infarction was 1.8% (33 of 1,855) with an upper 1-sided 95% confidence interval of 2.3%, which was significantly less than the prespecified performance goal of 3.2% (pnoninferiority <0.001). In the overall PE-Plus population, 12-month target vessel failure (defined as death, MI, or revascularization related to the target vessel) was 6.7% (170 of 2,554), cardiac death was 1.4% (37 of 2,554), MI was 1.1% (28 of 2,554), and ARC-definite/probable stent thrombosis was 0.7% (19 of 2,554). A prespecified secondary end point of 12-month target vessel failure in diabetic patients demonstrated a rate of 4.2% (14 of 332) with an upper 1-sided 95% confidence interval of 6.03%, which was significantly less than the performance goal of 12.6% (pnoninferiority <0.001). In conclusion, in this large registry of unselected patients, coronary artery revascularization with the PROMUS Element Plus everolimus-eluting stent demonstrates favorable results with low 1-year clinical event rates. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Residual non-union in a case of two and half year old child congenital pseudoarthrosis of ipsilateral tibia and fibula treated by intramedullary fixation with K-wire and allogeniccancellous strut graft: A case report

    Directory of Open Access Journals (Sweden)

    Siddaram N Patil, Sankar Rao P, Ranjith K Yalamanchili

    2013-04-01

    Full Text Available The pseudarthrosis usually develops during the first two years of life; however, there are reports of cases in which fractures developed before birth and reports of late-onset pseudarthrosis. There is a strong association between Congenital pseudoarthrosis and Type I neurofibromatosis. CPT develops in about 5.7% of patients with NF-I and 40% of patients with pseudoarthrosis were found to have NF-I. Main pathology is hyperplasia of fibroblasts with the formation of dense fibrous tissue at fracture site causing osteolysis, and persistence of pseudarthrosis. The difficulty in treating this condition occurs because of two factors. 1 Biologic: poor healing ability of the dysplastic segment of bone and 2 Mechanical: technical difficulty to fix small and osteopenic bone fragments in children without damaging the distal physis. A multitude of treatment protocols focusing on stimulating the healing process by using different bone grafting techniques were documented6. The graft materials most commonly used included osteoperiosteal graft, massive onlay graft, autogenous iliac crest bone graft, and vascularised bone graft.

  12. Munitions Response Projects Shallow Water Marine UXO Detection Survey - Underwater Survey of Camp Lejeune

    Science.gov (United States)

    2011-03-01

    includes a 2.0 meter (m) wide (2 receiver coil) non-contact bottom-skimming sensor platform, a down rigging tow bar, and a hydrofoil control surface...an elevator control surface that is commonly referred to as a hydrofoil . During the demonstration the system was mounted on a 6.7 m. ThunderJet jet...collection. • The hydrofoil (also referred to as an elevator) is an active control surface that produces upward and downward force on the sensor

  13. Shallow Water Marine UXO Detection Survey, United States Marine Corps Base, Camp Lejeune, North Carolina

    Science.gov (United States)

    2011-04-01

    rigging tow bar, and a hydrofoil control surface mounted on a 6.7 m (22 ft) ThunderJet® boat. The system was designed to be used with a 6 to 7 m (20 to...in which data collection could be conducted was 1 m (3 ft). The towing system, hydrofoil , and tiller were not designed to withstand greater sea state...platform, a down rigging tow bar, and a hydrofoil control surface mounted on a 6.7 m (22 ft) ThunderJet® boat. The system was designed to be used

  14. Center for Coastline Security Technology, Year 3

    Science.gov (United States)

    2008-05-01

    Figure 2.6.8: Close-Up Photograph of RPUUV Tail Section. Figure 2.6.9: Force and moments applied on a hydrofoil . Figure 2.6.10: The NACA 21016... hydrofoil profile. Florida Atlantic University 4/28/08 Page 10 Center for Coastline Security Technology Year Three-Final Report Figure...as a 3D wing with a NACA 21016 hydrofoil profile (Figure 2.6.10) held by 3 cylinders (Figure 2.6.8). Center for Coastline Security Technology Year

  15. Measurements of Cloaking Produced by an Array of Circular Cylinders

    DEFF Research Database (Denmark)

    Read, Robert; Bingham, Harry B.; Newman, J. N.

    2016-01-01

    -type cloaking. From a practical perspective, the elimination of the meandrift force on a surface-piercing structure associated with the cloaking process may find application in the reduction of second-order mooring loads in large offshore structures.This paper describes a further experimental investigation...

  16. SURFACE WAKE OF A CIRCULAR CYLINDER IN DILUTE AQUEOUS SOLUTIONS OF POLY(ETHYLENE OXIDE).

    Science.gov (United States)

    The wake formed by surface-piercing circular cylinders towed through 0, 100, and 200 parts per million (by weight) aqueous solutions of Poly( ethylene ... oxide ), Polyox WSR-301, was examined photographically. Cylinder diameters ranged from 1/4 in. to 2 in.; Froude numbers from 0.6 to 10. Measurements

  17. ASPECTS RELATED TO THE PROPULSION HYDRAFOIL SHIPS

    Directory of Open Access Journals (Sweden)

    Levent ALI

    2016-12-01

    Full Text Available In this paper, we analyze some aspects related to the propulsion of hydrofoil ships. They are very important for the success of the mission if they are military ships and for cargo security, if they are civilian transport ships, especially when navigating at high speed on their hydrofoil wings in rough sea conditions. This paper presents an original procedure for estimating the propulsion of hydrofoil ships. This procedure has enabled the development of a computer program that can predict both those types of ship propulsion regime imposed at a quasi-stationary speed and the march regime on wings. The calculation software obtained may serve to design any type of hydrofoil ship.

  18. Prediction of Cavitating Waterjet Propulsor Performance Using a Boundary Element Method

    Science.gov (United States)

    2007-10-01

    fast ferries. Compared to conventional propellers, waterjet propulsors provide several advantages. A comprehensive review of issues concerning the...approach Viscous Flow Analysis on a Partially Cavitating (Kerwin et al, 1987), as was recently implemented in Hydrofoil ," Journal of Ship Research, Vol. 41...Cavitating Hydrofoils ," Journal of Fluid Mechanics, Performance of Ducted Propeller," Sixth International Vol. 254, pp. 151-181, 1993. Symposium on

  19. Steaming on Convex Hulls

    Science.gov (United States)

    2007-08-01

    subsequently applied this example when he took command of USS AQUILA, a patrol hydrofoil missile ship. AQUILA achieved results so striking in comparison...achieve this record. Kline’s spreadsheet decision-support tool was provided to other hydrofoil commanders. A more general version has been conveyed to the...for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection

  20. A Numerical Study of Cavitation Inception in Complex Flow Fields

    Science.gov (United States)

    2007-12-01

    time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the...INCEPTION OF FINITE-SPAN HYDROFOIL [4] .........................................8 2.2 EFFECT OF VORTEX/VORTEX INTERACTION ON CAVITATION INCEPTION FOR...2M4001-1-ONR - p. 3 LIST OF TABLES TABLE 1. SUMMARY OF THE POWER CONSTANT IN THE SCALING LAW FOR THE NACA HYDROFOILS IN THE CASE OF A RELATIVELY

  1. 76 FR 62663 - Airworthiness Directives; The Boeing Company Model 767 Airplanes

    Science.gov (United States)

    2011-10-11

    ... load fittings of the front spar which could result in the loss of the strut-to-wing upper link load..., we are reopening the comment period to allow the public the chance to comment on these proposed... in the loss of the strut-to-wing upper link load path and possible separation of a strut and engine...

  2. 78 FR 49221 - Airworthiness Directives; Piper Aircraft, Inc. Airplanes

    Science.gov (United States)

    2013-08-13

    ... this AD, inspect the wing lift strut forks for cracks using magnetic particle procedures, such as those... Aircraft, Inc. Model J-2 airplanes equipped with wing lift struts. AD 99-26-19 currently requires repetitively inspecting the wing lift struts for dents and corrosion; repetitively inspecting the wing lift...

  3. Surface Patterning: Controlling Fluid Flow Through Dolphin and Shark Skin Biomimicry

    Science.gov (United States)

    Gamble, Lawren; Lang, Amy; Bradshaw, Michael; McVay, Eric

    2013-11-01

    Dolphin skin is characterized by circumferential ridges, perpendicular to fluid flow, present from the crest of the head until the tail fluke. When observing a cross section of skin, the ridges have a sinusoidal pattern. Sinusoidal grooves have been proven to induce vortices in the cavities that can help control flow separation which can reduce pressure drag. Shark skin, however, is patterned with flexible scales that bristle up to 50 degrees with reversed flow. Both dolphin ridges and shark scales are thought to help control fluid flow and increase swimming efficiency by delaying the separation of the boundary layer. This study investigates how flow characteristics can be altered with bio-inspired surface patterning. A NACA 4412 hydrofoil was entirely patterned with transverse sinusoidal grooves, inspired by dolphin skin but scaled so the cavities on the model have the same Reynolds number as the cavities on a swimming shark. Static tests were conducted at a Reynolds number of approximately 100,000 and at varying angles of attack. The results were compared to the smooth hydrofoil case. The flow data was quantified using Digital Particle Image Velocimetry (DPIV). The results of this study demonstrated that the patterned hydrofoil experienced greater separation than the smooth hydrofoil. It is hypothesize that this could be remediated if the pattern was placed only after the maximum thickness of the hydrofoil. Funding through NSF REU grant 1062611 is gratefully acknowledged.

  4. Comparing the performances of circular ponds with different impellers by CFD simulation and microalgae culture experiments.

    Science.gov (United States)

    Meng, Chen; Huang, Jianke; Ye, Chunyu; Cheng, Wenchao; Chen, Jianpei; Li, Yuanguang

    2015-07-01

    In this study, a numerical simulation using computational fluid dynamics (CFD) was used to investigate the hydrodynamic characteristics of circular ponds with three different impellers (hydrofoil, four-pitched-blade turbine, and grid plate). The reliability of the CFD model was validated by particle image velocimetry (PIV). Hydrodynamic analyses were conducted to evaluate the average velocity magnitude along the light direction (Uz), turbulence properties, average shear stress, pressure loss and the volume percentage of dead zone inside circular ponds. The simulation results showed that Uz value of hydrofoil was 58.9, 40.3, and 28.8% higher than those of grid plate with single arm, grid plate with double arms and four-pitched blade turbines in small-scale circular ponds, respectively. In addition, hydrofoil impeller with down-flow operation had outstanding mixing characteristics. Lastly, the results of Chlorella pyrenoidosa cultivation experiments indicated that the biomass concentration of hydrofoil impeller with down-flow operation was 65.2 and 88.8% higher than those of grid plate with double arms and four-pitched-blade turbine, respectively. Therefore, the optimal circular pond mixing system for microalgae cultivation involved a hydrofoil impeller with down-flow operation.

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

    OpenAIRE

    Willert, Christian; Kompenhans, Jürgen

    2010-01-01

    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 mo...

  6. The emission of sound by statistically homogeneous bubble layers

    NARCIS (Netherlands)

    van Wijngaarden, L.; van Wijngaarden, L.; Buist, J.

    1992-01-01

    This paper is concerned with the flow of a bubbly fluid along a wavy wall, which is one Fourier component of a linearized hydrofoil. The bubbles are dispersed, not throughout the whole of the liquid, but only over a certain distance from the wall, as occurs in practice with cavitation bubbles.

  7. Multiphase Thermodynamic Tables for Efficient Numerical Simulation of Cavitating Flows: A Novel Look-Up Approach Toward Efficient and Accurate Tables

    NARCIS (Netherlands)

    Khatami, F.; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie

    2015-01-01

    In this paper a numerical simulation of unsteady sheet cavitation is presented as it occurs on an NACA-0015 hydrofoil. The computational approach is based on the Euler equations for unsteady compressible flow, using an equilibrium cavitation model of Schnerr, Schmidt, and Saurel. It was found that

  8. Cavitation Simulation on Conventional and Highly-Skewed Propellers in the Behind Condition

    DEFF Research Database (Denmark)

    Shin, Keun Woo; Andersen, Poul; Mikkelsen, Robert Flemming

    2011-01-01

    . The validation of the cavitation model in EllipSys has been conducted for the cavitating flows on 2D/3D hydrofoils (Shin 2010). Prior to the cavitation simulation, the open-water characteristics of the propellers from the computation are compared with those from the propulsion test for the fully-wetted flows (Li...

  9. Compressible Turbulent Flow Numerical Simulations of Tip Vortex Cavitation

    NARCIS (Netherlands)

    Khatami, F.; van der Weide, Edwin Theodorus Antonius; Hoeijmakers, Hendrik Willem Marie

    2015-01-01

    For an elliptic Arndt’s hydrofoil numerical simulations of vortex cavitation are presented. An equilibrium cavitation model is employed. This single-fluid model assumes local thermodynamic and mechanical equilibrium in the mixture region of the flow, is employed. Furthermore, for characterizing the

  10. The Specialist Committee on Cavitation Induced Pressures, Final Report and Recommendations to the 23rd ITTC

    DEFF Research Database (Denmark)

    Friesch, J.; Kim, K.-H.; Andersen, Poul

    2002-01-01

    . But the trend of CFD applications toward 2-D and 3-D cavitating hydrofoils shows the great potential of those codes for propeller applications as well. For all numerical predictions, potential methods as well as RANS, it is important that the cavitation simulation is fully unsteady, particularly if higher...

  11. Ride Quality Index - A New Approach to Quantifying the Comparison of Acceleration Responses of High Speed Craft

    Science.gov (United States)

    2011-06-01

    reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information...ships, hydrofoils • NSWCCD mid-1970’s: RMS values reported not applicable when craft motions include shocks or impulsive velocity changes

  12. The Navy Unmanned Surface Vehicle (USV) Master Plan

    Science.gov (United States)

    2007-07-23

    average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and...completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of...PLANING HULL CRAFT....................................................................................................... 55 HYDROFOIL CRAFT

  13. A Computational Tool for the Rapid Design and Prototyping of Propellers for Underwater Vehicles

    Science.gov (United States)

    2007-09-01

    printer. The third study reviews the complete process of the design and production of an AUV propeller. Thus, OpenPVL performs a variety of...Butterworth-Heinemann Ltd., 1994. [4] J. E. Kerwin. Hydrofoils and Propellers. Cambridge, MIT CopyTech, 2001. [5] H. Chung, “An Enhanced Propeller

  14. Experimental Investigation into the Fatigue Life of Hybrid Joints Under Fully Reversed Flexure Loading

    Science.gov (United States)

    2008-06-01

    7 1.4 Literature Review ...Sea FlyerI one example vessel called the MIDFOIL where a hydrofoil and a parabolic lifting body shape are combined with a catamaran hull to achieve...integrity. *6 I 1.3 Scope of Work IA literature review of previous work relating to the present research is presented in the remainder of this section. A

  15. Submersible Aircraft Concept Design Study

    Science.gov (United States)

    2010-08-01

    response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and... reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information...5.3.1 Air cushion __________________________________________________ 8 5.3.2 Hydrofoils ___________________________________________________ 8 5.3.3

  16. CFD Analysis of a Penta-hulled, Air-Entrapment, High-Speed Planning Vessel

    Science.gov (United States)

    2008-03-01

    0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing ...instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information...f. Hydrofoils ................................................................................10 4. Analytic Hierarchy Process

  17. RANS Calculations of the Flow Past Inclined Propellers

    Science.gov (United States)

    2010-05-01

    Hyatt Chair/Document Review Panel ANSYS R© and CFX R© are registered trademarks of ANSYS, Inc. or its subsidiaries in the United States or other...ittc.sname.org/Propulsion.pdf. (Access Date: November 2009). [7] Vaz, G. N. V. B. (2005), Modelling of Sheet Cavitation on Hydrofoils and Marine

  18. Comparison of Real and Idealized Cetacean Flippers

    Science.gov (United States)

    2009-10-16

    collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources...gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or... hydrofoils (Fish and Rohr 1999). The similarity of design indicates similar hydrodynamic performance. The streamlined profile is characterized by a

  19. 46 CFR 153.2 - Definitions and acronyms.

    Science.gov (United States)

    2010-10-01

    ..., including hydrofoils, air-cushion vehicles, submersibles, floating craft whether self-propelled or not, and... BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS General § 153.2 Definitions and.... 90 °F) still water and 46 °C (approx. 115 °F) still air. Relief valve setting means the inlet line...

  20. National Academy of Sciences-Academy of Sciences of the USSR Workshop on the Mechanics of Ice and Its Applications Held in Moscow and Leningrad on June 16-26, 1991

    Science.gov (United States)

    1993-01-01

    hydrofoils, and hovercraft . The institute also works for foreign firms and is interested in acquiring additional foreign business. Moreover, Krylov offers...magnitudes, time of occurrence, and interplay may be seen. The main result of the energy exdiage study is the thesis that intermittent crushIMr or ice

  1. Sound Propagation in Shallow Water. Volume 2. Unclassified Papers

    Science.gov (United States)

    1974-11-15

    Nonlinear Acoustic Parametric End-Fire Array, ’• Fh.D. Thesis , University of Birmingham (England), June 1971. 14. M.B. Moffett, P.J. Westervelt, and...operational flexibility» Mobile platforms, such as surface ship hydrofoils or hovercraft , could use long towed arrays at the cost of limiting the coverage

  2. Optimization of submerged vane parameters

    Indian Academy of Sciences (India)

    H Sharma

    experimentally obtained the optimum vane sizes and recommended that it can be used for vane design. This ..... lift produced around the hydro-foil. More is .... energy. The reason behind this drop is that the vortices separate from the vane, which is acting as source of tur- bulence generation is now far away from the vortices.

  3. Management of Bone Gaps with Intramedullary Autologous Fibular ...

    African Journals Online (AJOL)

    ... 7 consecutive patients who presented with bone gaps that were managed with intramedullary non vascularised fibular strut graft. Method: Intramedulary Autologous fibular strut graft was used to breach the bone and the whole length augmented with cancellous graft and bridged with bone plate; external fixators or k wires.

  4. 2-year outcome after biodegradable polymer sirolimus- and biolimus- eluting coronary stents.From the randomized SORT OUT VII trial

    DEFF Research Database (Denmark)

    Jensen, Lisette Okkels; Maeng, Michael; Raungaard, Bent

    2018-01-01

    AIMS: The SORT OUT VII trial compared the thin-strut cobalt-chromium sirolimus-eluting Orsiro stent with a slow polymer degradation and the thicker-strut stainless steel biolimus-eluting Nobori stent with a moderate-term polymer degradation in an all-comer patient population. METHODS AND RESULTS...

  5. Microstructure and micromechanics of the heart urchin test from X-ray tomography

    DEFF Research Database (Denmark)

    Müter, D.; Sørensen, H. O.; Oddershede, Jette

    2015-01-01

    . Three dimensional imaging demonstrates that the bulk of the test is composed of only two distinct, highly porous, fenestrated regions (stereom), in which the thickness of the struts is constant. Different degrees of porosity are achieved by varying the spacing of the struts. Drawing an analogy...

  6. Fracture of metal foams : In-situ testing and numerical modeling

    NARCIS (Netherlands)

    Onck, P.R.; van Merkerk, R.; de Hosson, J.T.M.; Schmidt, I

    This paper is on a combined experimental/modeling study on the tensile fracture of open-cell foams. In-situ tensile tests show that individual struts can fail in a brittle or ductile mode, presumably depending on the presence of casting defects. In-situ single strut tests were performed, enabling

  7. Periprosthetic femoral fractures

    DEFF Research Database (Denmark)

    Tomás Hernández, Jordi; Holck, Kim

    2015-01-01

    Cortical onlay strut allografts, as the primary method of fixation or as a supplementary fixation when a plate is used, have been a common option to treat B1 and C type PFF in the past decades since the technique was described by Penenberg et al. in 1989 [5]. Strut grafts were described as a usef...

  8. Short vowel placements in RP past and present

    DEFF Research Database (Denmark)

    Fabricius, Anne

    This study addresses diachronic change in the short vowel system of RP. While TRAP lowering and backing in RP has been reported previously, the movements STRUT has undergone have proven more difficult to determine. This study identifies a TRAP/STRUT 'rotation' using acoustic measurements of the s...

  9. Optical coherence tomography analysis of the stenting of saphenous vein graft (SOS) Xience V Study: use of the everolimus-eluting stent in saphenous vein graft lesions.

    Science.gov (United States)

    Papayannis, Aristotelis C; Michael, Tesfaldet T; Yangirova, Dinara; Abdel-Karim, Abdul-Rahman; Kohlhaas, Julia; Mahmood, Arif; Addo, Tayo; Haagen, Donald; Makke, Lorenza; Roesle, Michele; Rangan, Bavana; Banerjee, Subhash; Brilakis, Emmanouil S

    2012-08-01

    The Stenting of Saphenous Grafts-Xience V (SOS-Xience V) trial prospectively examined the frequency of angiographic in-stent restenosis in saphenous vein graft (SVG) lesions 12 months after implantation of a Xience V everolimus-eluting stent (EES; Abbott Vascular). Optical coherence tomography (OCT) during follow-up angiography was added to the protocol after OCT was approved for clinical use in the United States. Forty patients with 40 SVG lesions were enrolled in the study, of whom 27 underwent 12-month coronary angiography and 12 (only 1 of whom had in-stent restenosis) also had follow-up OCT evaluation. OCT strut-level analysis was performed to determine the percentage of strut coverage, malapposition, strut protrusion, neointimal thickness, and the existence of thrombus. Mean patient age was 67 ± 7 years, and 95% were men. A total of 2584 struts were evaluated by OCT. The percentages for uncovered, malapposed, and protruding struts were 4%, 9%, and 15%, respectively. The mean strut neointimal thickness was 0.094 ± 0.094 mm. Of the 12 stents analyzed, 4 (33%) showed full neointimal coverage, 2 (17%) had all the struts embedded, 7 (58%) had at least 1 malapposed strut, and 10 (83%) had at least 1 protruding strut. The mean difference between the stent area and the lumen area was 0.36 ± 1.6 mm². No thrombus was detected in the stented areas. Use of EES in SVGs is associated with high rates of stent strut coverage and high malapposition rates at 12 months post implantation.

  10. Method and apparatus for production of subsea hydrocarbon formations

    Science.gov (United States)

    Blandford, J.W.

    1995-01-17

    A system for controlling, separating, processing and exporting well fluids produced from subsea hydrocarbon formations is disclosed. The subsea well tender system includes a surface buoy supporting one or more decks above the water surface for accommodating equipment to process oil, gas and water recovered from the subsea hydrocarbon formation. The surface buoy includes a surface-piercing central flotation column connected to one or more external flotation tanks located below the water surface. The surface buoy is secured to the sea bed by one or more tendons which are anchored to a foundation with piles imbedded in the sea bed. The system accommodates multiple versions on the surface buoy configuration. 20 figures.

  11. Design and Evolution of a Modular Tensegrity Robot Platform

    Science.gov (United States)

    Bruce, Jonathan; Caluwaerts, Ken; Iscen, Atil; Sabelhaus, Andrew P.; SunSpiral, Vytas

    2014-01-01

    NASA Ames Research Center is developing a compliant modular tensegrity robotic platform for planetary exploration. In this paper we present the design and evolution of the platform's main hardware component, an untethered, robust tensegrity strut, with rich sensor feedback and cable actuation. Each strut is a complete robot, and multiple struts can be combined together to form a wide range of complex tensegrity robots. Our current goal for the tensegrity robotic platform is the development of SUPERball, a 6-strut icosahedron underactuated tensegrity robot aimed at dynamic locomotion for planetary exploration rovers and landers, but the aim is for the modular strut to enable a wide range of tensegrity morphologies. SUPERball is a second generation prototype, evolving from the tensegrity robot ReCTeR, which is also a modular, lightweight, highly compliant 6-strut tensegrity robot that was used to validate our physics based NASA Tensegrity Robot Toolkit (NTRT) simulator. Many hardware design parameters of the SUPERball were driven by locomotion results obtained in our validated simulator. These evolutionary explorations helped constrain motor torque and speed parameters, along with strut and string stress. As construction of the hardware has finalized, we have also used the same evolutionary framework to evolve controllers that respect the built hardware parameters.

  12. The effects of temperature and use of vibrating wire strain gauges for braced excavations

    Energy Technology Data Exchange (ETDEWEB)

    Boone, S. J. [Golder Associates, Irvine, CA (United States); Crawford, A. M. [Toronto Univ., ON (Canada). Dept. of Civil Engineering

    2000-09-01

    Strut loads in bracer excavations are routinely monitored with strain gauges which range in complexity from simple mechanical measurements to vibrating wire transducers. While in soft soils the effect of temperature changes in strut loads may not be significant, these effects may be very signifciant for stiff and dense soils and rock thermal loading, where inadequate appreciation of the role played by thermal laods may lead to misinterpretations and faulty design that is not representative of potential field loading. This paper interprets the theoretical and practical implications of temperature change on strut loads and discusses the relative merits of using a vibrating wire strain gauge to measure and evaluate the effects of temperature and earth loads. It is shown that by comparing the incremental changes of strut load and temperature from vibrating wire strain gauge data, the temperature-dependent loads, the relative fixity of the strut end, and the earth loads, and mobilized ground stiffness can be deduced. The approach proposed provides a transparent and strut-specific means of evaluating the effects of temperature on struts with braced excavations and is supported by both empirical data and practical application of elastic theory. 9 refs., 6 figs.

  13. Kinematic performance analysis of a parallel-chain hexapod machine

    Energy Technology Data Exchange (ETDEWEB)

    Jing Song; Jong-I Mou; Calvin King

    1998-05-18

    Inverse and forward kinematic models were derived to analyze the performance of a parallel-chain hexapod machine. Analytical models were constructed for both ideal and real structures. Performance assessment and enhancement algorithms were developed to determine the strut lengths for both ideal and real structures. The strut lengths determined from both cases can be used to analyze the effect of structural imperfections on machine performance. In an open-architecture control environment, strut length errors can be fed back to the controller to compensate for the displacement errors and thus improve the machine's accuracy in production.

  14. Optical coherence tomography findings after chronic total occlusion interventions: Insights from the “AngiographiC evaluation of the everolimus-eluting stent in chronic Total occlusions” (ACE-CTO) study (NCT01012869)

    Energy Technology Data Exchange (ETDEWEB)

    Sherbet, Daniel P.; Christopoulos, Georgios; Karatasakis, Aris; Danek, Barbara Anna; Kotsia, Anna; Navara, Rachita; Michael, Tesfaldet T.; Roesle, Michele; Rangan, Bavana V.; Haagen, Donald [VA North Texas Healthcare System and University of Texas Southwestern Medical Center, Dallas, TX (United States); Garcia, Santiago [Minneapolis VA Healthcare System and University of Minnesota, Minneapolis, MN (United States); Maniu, Calin [Bon Secours Health System, Suffolk, VA (United States); Pershad, Ashish [Banner Good Samaritan Medical Center, Phoenix, AZ (United States); Abdullah, Shuaib M.; Hastings, Jeffrey L.; Kumbhani, Dharam J.; Luna, Michael; Addo, Tayo; Banerjee, Subhash [VA North Texas Healthcare System and University of Texas Southwestern Medical Center, Dallas, TX (United States); Brilakis, Emmanouil S., E-mail: esbrilakis@gmail.com [VA North Texas Healthcare System and University of Texas Southwestern Medical Center, Dallas, TX (United States)

    2016-10-15

    Background: There is limited information on optical coherence tomography (OCT) findings after percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs). OCT allows high resolution imaging that can enhance understanding of the vascular response after stenting of chronically occluded vessels. Methods: The Angiographic Evaluation of the Everolimus-Eluting Stent in Chronic Total Occlusions (ACE-CTO) study collected angiographic and clinical outcomes from 100 patients undergoing CTO PCI with the everolimus-eluting stent (EES). OCT was performed 8-months post stenting in 62 patients. Every third frame was analyzed throughout the course of the stented arterial segment. Lumen contours were semi-automatically traced and stent struts were manually delineated, with automatic measurement of the strut to lumen distance. Struts on the luminal side of the lumen contour were classified as malapposed if the distance to the lumen contour exceeded 0.108 mm. Results: A total of 44,450 struts in 6047 frames were analyzed, of which 4113 9.3%, 95% confidence intervals [CI] 9.0% to 9.5%) were malapposed and 1230 (2.8%, 95% CI 2.6% to 2.9%) were uncovered. Fifty-five of 62 patients (88.7%, 95% CI 78.5% to 98.4%) had at least one malapposed stent strut and 50 patients (80.7%, 95% CI 69.2% to 88.6%) had at least one uncovered stent strut. Mean strut-intimal thickness of the apposed and malapposed struts was 0.126 ± 0.140 mm and − 0.491 ± 0.440 mm, respectively. Conclusion: High rates of stent strut malapposition and incomplete stent strut coverage were observed after CTO PCI using EES, highlighting unique challenges associated with stent implantation in CTOs. - Highlights: • Percutaneous coronary intervention with drug-eluting stents for chronic total occlusion is associated with a 40% rate of binary in-stent restenosis at 8 months • Of patients who receive a drug eluting stent for a chronic total occlusion 88.7% will have stent strut malapposition and 80.7% will

  15. Compression-compression fatigue of Pd43Ni10Cu27P20 metallic glass foam

    Science.gov (United States)

    Wang, Gongyao; Demetriou, Marios D.; Schramm, Joseph P.; Liaw, Peter K.; Johnson, William L.

    2010-07-01

    Compression-compression fatigue testing of metallic-glass foam is performed. A stress-life curve is constructed, which reveals an endurance limit at a fatigue ratio of about 0.1. The origin of fatigue resistance of this foam is identified to be the tendency of intracellular struts to undergo elastic and reversible buckling, while the fatigue process is understood to advance by anelastic strut buckling leading to localized plasticity (shear banding) and ultimate strut fracture. Curves of peak and valley strain versus number of cycles coupled with plots of hysteresis loops and estimates of energy dissipation at various loading cycles confirm the four stages of foam-fatigue.

  16. Efficient computations of wave loads on offshore structures

    DEFF Research Database (Denmark)

    Paulsen, Bo Terp

    The present thesis considers numerical computations of fully nonlinear wave impacts on bottom mounted surface piercing circular cylinders at intermediate water depths. The aim of the thesis is to provide new knowledge regarding wave loads on foundations for offshore wind turbines. Hence, the dime......The present thesis considers numerical computations of fully nonlinear wave impacts on bottom mounted surface piercing circular cylinders at intermediate water depths. The aim of the thesis is to provide new knowledge regarding wave loads on foundations for offshore wind turbines. Hence...... and established analytical force formulations accurate to the third order in wave steepness. The physics related to the strongly nonlinear load phenomena “secondary load cycles” is described and an explanation of the wave load phenomena is provided. To further support the explanation a simple inviscid kinematic...... model flow is derived. The discussion of wave impacts on circular cylinders is further extended to uni- and bi-directional phase-focused waves. Here, the influence of the nondimensional wave steepness and wave directionality is discussed. For the steepest wave impacts “secondary load cycles...

  17. Air Entrainment and Surface Ripples in a Turbulent Ship Hull Boundary Layer

    Science.gov (United States)

    Masnadi, Naeem; Erinin, Martin; Duncan, James H.

    2017-11-01

    The air entrainment and free-surface fluctuations caused by the interaction of a free surface and the turbulent boundary layer of a vertical surface-piercing plate is studied experimentally. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes. This belt device is mounted inside a large water tank with the water level set just below the top edge of the belt. The belt, rollers, and supporting frame are contained within a sheet metal box to keep the device dry except for one 6-meter-long straight test section. The belt is accelerated suddenly from rest until reaching constant speed in order to create a temporally evolving boundary layer analogous to the spatially evolving boundary layer that would exist along a surface-piercing towed flat plate. Surface ripples are measured using a cinematic laser-induced fluorescence technique with the laser sheet oriented parallel or normal to the belt surface. Air entrainment events and bubble motions are recorded from underneath the water surface using a stereo imaging system. Measurements of small bubbles, that tend to stay submerged for a longer time, are planned via a high-speed digital in-line holographic system. The support of the Office of Naval Research is gratefully acknowledged.

  18. Further validation of the hybrid particle-mesh method for vortex shedding flow simulations

    Directory of Open Access Journals (Sweden)

    Seung-Jae Lee

    2015-11-01

    Full Text Available This is the continuation of a numerical study on vortex shedding from a blunt trailing-edge of a hydrofoil. In our previous work (Lee et al., 2015, numerical schemes for efficient computations were successfully implemented; i.e. multiple domains, the approximation of domain boundary conditions using cubic spline functions, and particle- based domain decomposition for better load balancing. In this study, numerical results through a hybrid particle-mesh method which adopts the Vortex-In-Cell (VIC method and the Brinkman penalization model are further rigorously validated through comparison to experimental data at the Reynolds number of 2 × 106. The effects of changes in numerical parameters are also explored herein. We find that the present numerical method enables us to reasonably simulate vortex shedding phenomenon, as well as turbulent wakes of a hydrofoil.

  19. A THERMODYNAMIC CAVITATION MODEL APPLICABLE TO HIGH TEMPERATURE FLOW

    Directory of Open Access Journals (Sweden)

    De-Min Liu

    2011-01-01

    Full Text Available Cavitation is not only related with pressure, but also affected by temperature. Under high temperature, temperature depression of liquids is caused by latent heat of vaporization. The cavitation characteristics under such condition are different from those under room temperature. The paper focuses on thermodynamic cavitation based on the Rayleigh-Plesset equation and modifies the mass transfer equation with fully consideration of the thermodynamic effects and physical properties. To validate the modified model, the external and internal flow fields, such as hydrofoil NACA0015 and nozzle, are calculated, respectively. The hydrofoil NACA0015's cavitation characteristic is calculated by the modified model at different temperatures. The pressure coefficient is found in accordance with the experimental data. The nozzle cavitation under the thermodynamic condition is calculated and compared with the experiment.

  20. Modular Hydropower Engineering and Pilot Scale Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Chesser, Phillip C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    Emrgy has developed, prototyped and tested a modular hydropower system for renewable energy generation. ORNL worked with Emrgy to demonstrate the use of additive manufacturing in the production of the hydrofoils and spokes for the hydrokinetic system. Specifically, during Phase 1 of this effort, ORNL printed and finished machined patterns for both the hydrofoils and spokes that were subsequently used in a sand casting manufacturing process. Emrgy utilized the sand castings for a pilot installation in Denver, CO, where the parts represented an 80% cost savings from the previous prototype build that was manufactured using subtractive manufacturing. In addition, the castings were completed with ORNL’s newly developed AlCeMg alloy that will be tested for performance improvements including higher corrosion resistance in a water application than the 6160 alloy used previously

  1. Experimental aeroacoustic study of a landing gear in the unsteady flow induced by a propeller

    Science.gov (United States)

    Chekiri, Rafik

    An aeroacoustic study of a two-strut, two-wheel, nacelle-mounted landing gear was conducted to investigate the effects of an upstream propeller on the radiated noise. The development of a 1:10.8 scale model based on a Bombardier Q400 aircraft, consisting of a propeller, motor, nacelle, and landing gear assembly is discussed. Comparisons are made between cases with and without an actuated upstream propeller. Far-field microphone measurements out of the airstream are presented to characterize the acoustic effects of each model component. The main strut and wheels of the model were equipped with surface-mounted microphones to measure unsteady pressures. It is shown that the noise signature of the landing gear cannot be observed over the tunnel background noise in the far-field. Unsteady surface pressures on the main strut show dominant peaks related to vortex shedding from the drag strut for both steady and unsteady upstream conditions.

  2. Rockets in World War I

    Science.gov (United States)

    2004-01-01

    World War I enlisted rockets once again for military purposes. French pilots rigged rockets to the wing struts of their airplanes and aimed them at enemy observation balloons filled with highly inflammable hydrogen.

  3. Plasticity Approach to HSC Shear Wall Design

    DEFF Research Database (Denmark)

    Liu, Lunying; Nielsen, Mogens Peter

    1998-01-01

    The paper describes a simple theory for determining the ultimate strength of shear walls. It is based on application of the theory of perfectly plastic materials. When applied to concrete the theoretical solutions must be modified by inserting into the solutions a reduced compressive strength...... to 140 MPa and reinforcement yield strengths up to 1420 MPa. The work was carried out as a Ph.D. study by the first author, the second author supervising the study.Keywords: shear wall, plasticity, strut and tie, load-carrying capacity, concrete, reinforcement....... of concrete. The reduced strength is named the effective strength. The paper describes simple lower bound solutions. They consist of pure strut action or strut action combined with diagonal compression fields outside the struts. Near moment maximum and near supports the stress fields are modified to save...

  4. Experimental Study of Blood Laminar Flow Through a Stented Artery

    National Research Council Canada - National Science Library

    Benard, N

    2001-01-01

    .... That is why, to study the flow disturbances through a stented section, we built an in vitro model reproducing the struts shapes of a marketed endoprothesis, The experimental artery, is composed...

  5. Plaadid / Veiko Pesur

    Index Scriptorium Estoniae

    Pesur, Veiko

    2006-01-01

    Uutest heliplaatidest Iron Maiden "A Matter of Life and Death", Quantic "An Announcement To Answer", The Answer "Rise", Amp Fiddler "Afro Strut", Honey Power "Macrosilly", Paris Hilton "Paris", Marie Fredriksson "Min Bäste vän"

  6. Geometric modeling of Plateau borders using the orthographic projection method for closed cell rigid polyurethane foam thermal conductivity prediction

    Science.gov (United States)

    Xu, Jie; Wu, Tao; Peng, Chuang; Adegbite, Stephen

    2017-09-01

    The geometric Plateau border model for closed cell polyurethane foam was developed based on volume integrations of approximated 3D four-cusp hypocycloid structure. The tetrahedral structure of convex struts was orthogonally projected into 2D three-cusp deltoid with three central cylinders. The idealized single unit strut was modeled by superposition. The volume of each component was calculated by geometric analyses. The strut solid fraction f s and foam porosity coefficient δ were calculated based on representative elementary volume of Kelvin and Weaire-Phelan structures. The specific surface area Sv derived respectively from packing structures and deltoid approximation model were put into contrast against strut dimensional ratio ɛ. The characteristic foam parameters obtained from this semi-empirical model were further employed to predict foam thermal conductivity.

  7. Laser Metrology System for Precision Pointing

    National Research Council Canada - National Science Library

    Hospodar, Edward

    2003-01-01

    .... The Precision Pointing Hexapod (PPH) at Naval Postgraduate School (NPS) is exactly such a platform initially installed with voice coil actuators and accelerometers on each strut by CSA Engineering Inc...

  8. Obstacle-induced spiral vortex breakdown

    OpenAIRE

    Pasche, Simon; Gallaire, François; Dreyer, Matthieu; Farhat, Mohamed

    2014-01-01

    An experimental investigation on vortex breakdown dynamics is performed. An adverse pressure gradient is created along the axis of a wing-tip vortex by introducing a sphere downstream of an elliptical hydrofoil. The instrumentation involves high-speed visualizations with air bubbles used as tracers and 2D Laser Doppler Velocimeter (LDV). Two key parameters are identified and varied to control the onset of vortex breakdown: the swirl number, defined as the maximum azimuthal velocity divided by...

  9. Proceedings of the General Meeting of the American Towing Tank Conference (20th) Held at Hoboken, New Jersey on 2-4 August 1983. Volume 1.

    Science.gov (United States)

    1983-08-01

    the Conference. The sheer magnitude of these contributions required a two volume publication of the proceedings containing the following materials...Vol. 7, No. 65 Jan. 1960. 6) Wade, R.B. "Linearized Theory of a Partially Cavitating Piano -Convex Hydrofoil Including the Effects of Camber and...shape NACA 64 A010 Turbulence stimulator wire 0.016 in. (0.041 an) Turbulence stimulation was provided by 0.016 in. (0.04U6 an) diameter piano wire

  10. Multiple-Vehicle Resource-Constrained Navigation in the Deep Ocean

    Science.gov (United States)

    2011-09-01

    for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data...sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden...seen suc- cess in certain circumstances. Most vehicles use a combination of propeller thrusters and hydrofoil control surfaces to steer and maneuver

  11. Computer-Aided Detection of Rapid, Overt, Airborne, Reconnaissance Data with the Capability of Removing Oceanic Noises

    Science.gov (United States)

    2013-12-01

    for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of...mounted on a hydrofoil sled. The generator produces direct current through the electrode array to create a magnetic field that replicates the magnetic...War College Review , 61, no. 1, 106–127. Watts, A. J., 1999: Jane’s Underwater Warfare Systems. 11th ed. Jane’s Information Group, 259–276. 137

  12. Between Peace and the Air-Sea Battle: A War at Sea Strategy

    Science.gov (United States)

    2012-01-01

    including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the...23 of the 1988 republication of Corbett’s masterwork by the Naval Institute Press. 3. For comparison, a PHM (or patrol combatant hydrofoil , a type... Review , Autumn 2012, Vol. 65, No. 4 NWC_Autumn2012Review.indd 34 8/14/12 8:46 AM

  13. UV Sentry: A Collaborative Approach to Creating a Collaborative System

    Science.gov (United States)

    2012-02-01

    0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions...searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send... Hydrofoil Supported Catamaran Length Overall 11 m Beam 4.7 m Draft 0.8 m Displacement 7.8 tonnes Speed (S.S. 4) 40 knots Duration 6 days

  14. Prediction of Waterjet Cavitation: End of Year FY08

    Science.gov (United States)

    2008-08-11

    hour per response, including the time for reviewing instructions, searching existing data sources,gathering and maintaining the data needed, and...completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection ofinformation...M has been applied to a variety of compressible and incompressible multiphase flows, from hydrofoils and control surfaces to high-speed

  15. Towing Tank Measurements of Hydrodynamic Performance of a Horizontal Axis Tidal Turbine Under Unsteady Flow Conditions

    Science.gov (United States)

    2013-05-10

    hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and...completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of...torque using the same principles an airplane uses to remain in the air. The blades act as hydrofoils , creating lift and using the lift to turn the shaft

  16. Review of parameters influencing the structural response of a submerged body under cavitation conditions

    OpenAIRE

    Escaler, X; De La Torre, O; Farhat, M

    2015-01-01

    Submerged structures that operate under extreme flows are prone to suffer large scale cavitation attached to thei r surfaces. Under such conditions the added mass effects differ from the expected ones in pure liquids. Moreover, the existence of small gaps between the structure and surrounding bodies filled with fluid also influence the dynamic response. A series of experiments and numerical simulations have been carried out with a truncated NACA0009 hydrofoil mounted as a cantilever beam at t...

  17. Assessment of underwater glider performance through viscous computational fluid dynamics

    OpenAIRE

    Lidtke, Artur Konrad; Turnock, Stephen; Downes, Jon

    2016-01-01

    The process of designing an apt hydrodynamic shape for a new underwater glider is discussed. Intermediate stages include selecting a suitable axi-symmetric hull shape, adding hydrofoils and appendages, and evaluating the performance of the final design. All of the hydrodynamic characteristics are obtained using computational fluid dynamics using the kT - kL - ω transition model. It is shown that drag reduction of the main glider hull is of crucial importance to the ultimate performance. Sugge...

  18. Transient Euler-Lagrange/DEM simulation of stent thrombosis

    Directory of Open Access Journals (Sweden)

    Stiehm Michael

    2016-09-01

    Full Text Available Stent implantation is the treatment of choice for cardiovascular diseases. By introduction of biodegradable thick strut stents investigations of thrombosis formation is one focus of research. This study deals with a transient Euler-Lagrange/DEM approach to simulate the flow field, platelet movement and clotting. The recirculation zones prolong particle residence time. As a result, the vicinity of stent struts shown a particularly higher risk for stent thrombosis.

  19. Correlation between Bieniawski's RMR and Barton's Q Index in Low-Quality Soils

    OpenAIRE

    Castro-Fresno,D; Diego-Carrera,R; Ballester-Muñoz,F; Álvarez-García,J

    2010-01-01

    The appropriate sizing of the strutting sections of a tunnel depends on the adequacy of the parameters initially used to perform the calculation. A very common practice in underground engineering is to make an estimation of the strutting through the use of geomechanical classifications. Nowadays, the most widely used classifications are Bieniawski's RMR Quality Index and The Barton et al. Q Quality Index. The research work carried out aims to provide a correlation between the two quality inde...

  20. Modeling and simulation of a novel autonomous underwater vehicle with glider and flapping-foil propulsion capabilities

    Science.gov (United States)

    Tian, Wen-long; Song, Bao-wei; Du, Xiao-xu; Mao, Zhao-yong; Ding, Hao

    2012-12-01

    HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes: glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the conceptual vehicle was developed on the assumption that HAISHEN has a rigid body with two independently controlled oscillating hydrofoils. A flapping-foil model was developed based on the work done by Georgiades et al. (2009). Effect of controllable hydrofoils on the vehicle stable motion performance was studied theoretically. Finally, a dynamics simulation of the vehicle in both operating modes is created in this paper. The simulation demonstrates that: (1) in the glider mode, owing to the independent control of the pitch angle of each hydrofoil, HAISHEN travels faster and more efficiently and has a smaller turning radius than conventional fix-winged gliders; (2) in the flapping-foil propulsion mode, HAISHEN has a high maneuverability with a turning radius smaller than 15 m and a forward motion velocity about 1.8 m/s; (3) the vehicle is stable under all expected operating conditions.

  1. Numerical Prediction of Wave Patterns Due to Motion of 3D Bodies by Kelvin-Havelock Sources

    Directory of Open Access Journals (Sweden)

    Ghassemi Hassan

    2016-12-01

    Full Text Available This paper discusses the numerical evaluation of the hydrodynamic characteristics of submerged and surface piercing moving bodies. Generally, two main classes of potential methods are used for hydrodynamic characteristic analysis of steady moving bodies which are Rankine and Kelvin-Havelock singularity distribution. In this paper, the Kelvin- Havelock sources are used for simulating the moving bodies and then free surface wave patterns are obtained. Numerical evaluation of potential distribution of a Kelvin-Havelock source is completely presented and discussed. Numerical results are calculated and presented for a 2D cylinder, single source, two parallel moving source, sphere, ellipsoid and standard Wigley hull in different situation that show acceptable agreement with results of other literatures or experiments.

  2. Hydrodynamic analysis of a floating body with an open chamber using a 2D fully nonlinear numerical wave tank

    Directory of Open Access Journals (Sweden)

    Ahmed Syed Uzair

    2012-09-01

    Full Text Available Hydrodynamic analysis of a surface-piercing body with an open chamber was performed with incident regular waves and forced-heaving body motions. The floating body was simulated in the time domain using a 2D fully nonlinear numerical wave tank (NWT technique based on potential theory. This paper focuses on the hydrodynamic behavior of the free surfaces inside the chamber for various input conditions, including a two-input system: both incident wave profiles and forced body velocities were implemented in order to calculate the maximum surface elevations for the respective inputs and evaluate their interactions. An appropriate equivalent linear or quadratic viscous damping coefficient, which was selected from experimental data, was employed on the free surface boundary inside the chamber to account for the viscous energy loss on the system. Then a comprehensive parametric study was performed to investigate the nonlinear behavior of the wave-body interaction.

  3. Uncertainty quantification and validation of 3D lattice scaffolds for computer-aided biomedical applications.

    Science.gov (United States)

    Gorguluarslan, Recep M; Choi, Seung-Kyum; Saldana, Christopher J

    2017-07-01

    A methodology is proposed for uncertainty quantification and validation to accurately predict the mechanical response of lattice structures used in the design of scaffolds. Effective structural properties of the scaffolds are characterized using a developed multi-level stochastic upscaling process that propagates the quantified uncertainties at strut level to the lattice structure level. To obtain realistic simulation models for the stochastic upscaling process and minimize the experimental cost, high-resolution finite element models of individual struts were reconstructed from the micro-CT scan images of lattice structures which are fabricated by selective laser melting. The upscaling method facilitates the process of determining homogenized strut properties to reduce the computational cost of the detailed simulation model for the scaffold. Bayesian Information Criterion is utilized to quantify the uncertainties with parametric distributions based on the statistical data obtained from the reconstructed strut models. A systematic validation approach that can minimize the experimental cost is also developed to assess the predictive capability of the stochastic upscaling method used at the strut level and lattice structure level. In comparison with physical compression test results, the proposed methodology of linking the uncertainty quantification with the multi-level stochastic upscaling method enabled an accurate prediction of the elastic behavior of the lattice structure with minimal experimental cost by accounting for the uncertainties induced by the additive manufacturing process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Plasma separation process: Magnet move to Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    1989-07-01

    This is the final report on the series of operations which culminated with the delivery of the Plasma Separation Process prototype magnet system (PMS) to Building K1432 at Oak Ridge National Laboratory (ORNL). This procedure included real time monitoring of the cold mass support strut strain gauges and an in-cab rider to monitor the instrumentation and direct the driver. The primary technical consideration for these precautions was the possibility of low frequency resonant vibration of the cold mass when excited by symmetrical rough road conditions at specific speeds causing excess stress levels in the support struts and consequent strut failure. A secondary consideration was the possibility of high acceleration loads due to sudden stops, severe road conditions, of impacts. The procedure for moving and transportation to ORNL included requirements for real time continuous monitoring of the eight strut stain gauges and three external accelerometers. Because the strain gauges had not been used since the original magnet cooldown, it was planned to verify their integrity during magnet warmup. The measurements made from the strut strain gauges resulted in stress values that were physically impossible. It was concluded that further evaluation was necessary to verify the usefulness of these gauges and whether they might be faulty. This was accomplished during the removal of the magnet from the building. 6 figs., 1 tab

  5. Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure.

    Science.gov (United States)

    Torres, Ashley M; Matheny, Jonathan B; Keaveny, Tony M; Taylor, David; Rimnac, Clare M; Hernandez, Christopher J

    2016-03-15

    Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure.

  6. Reinforcements in avian wing bones: Experiments, analysis, and modeling.

    Science.gov (United States)

    Novitskaya, E; Ruestes, C J; Porter, M M; Lubarda, V A; Meyers, M A; McKittrick, J

    2017-12-01

    Almost all species of modern birds are capable of flight; the mechanical competency of their wings and the rigidity of their skeletal system evolved to enable this outstanding feat. One of the most interesting examples of structural adaptation in birds is the internal structure of their wing bones. In flying birds, bones need to be sufficiently strong and stiff to withstand forces during takeoff, flight, and landing, with a minimum of weight. The cross-sectional morphology and presence of reinforcing structures (struts and ridges) found within bird wing bones vary from species to species, depending on how the wings are utilized. It is shown that both morphology and internal features increases the resistance to flexure and torsion with a minimum weight penalty. Prototypes of reinforcing struts fabricated by 3D printing were tested in diametral compression and torsion to validate the concept. In compression, the ovalization decreased through the insertion of struts, while they had no effect on torsional resistance. An elastic model of a circular ring reinforced by horizontal and vertical struts is developed to explain the compressive stiffening response of the ring caused by differently oriented struts. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Active Flow Control on Bidirectional Rotors for Tidal MHK Applications

    Energy Technology Data Exchange (ETDEWEB)

    Shiu, Henry [Research Engineer; van Dam, Cornelis P. [Professor

    2013-08-22

    A marine and hydrokinetic (MHK) tidal turbine extracts energy from tidal currents, providing clean, sustainable electricity generation. In general, all MHK conversion technologies are confronted with significant operational hurdles, resulting in both increased capital and operations and maintenance (O&M) costs. To counter these high costs while maintaining reliability, MHK turbine designs can be simplified. Prior study found that a tidal turbine could be cost-effectively simplified by removing blade pitch and rotor/nacelle yaw. Its rotor would run in one direction during ebb and then reverse direction when the current switched to flood. We dubbed such a turbine a bidirectional rotor tidal turbine (BRTT). The bidirectional hydrofoils of a BRTT are less efficient than conventional hydrofoils and capture less energy, but the elimination of the pitch and yaw systems were estimated to reduce levelized cost of energy by 7.8%-9.6%. In this study, we investigated two mechanisms for recapturing some of the performance shortfall of the BRTT. First, we developed a novel set of hydrofoils, designated the yy series, for BRTT application. Second, we investigated the use of active flow control via microtabs. Microtabs are small deployable/retractable tabs, typically located near the leading or trailing edge of an air/hydrofoil with height on the order of the boundary layer thickness (1% - 2% of chord). They deploy approximately perpendicularly to the foil surface and, like gurney flaps and plain flaps, globally affect the aerodynamics of the airfoil. By strategically placing microtabs and selectively deploying them based on the direction of the inflow, performance of a BRTT rotor can be improved while retaining bidirectional operation. The yy foils were computationally designed and analyzed. They exhibited better performance than the baseline bidirectional foil, the ellipse. For example, the yyb07cn-180 had 14.7% higher (l/d)max than an ellipse of equal thickness. The yyb07cn

  8. On the motion of linked spheres in a Stokes flow

    Science.gov (United States)

    Box, F.; Han, E.; Tipton, C. R.; Mullin, T.

    2017-04-01

    The results of an experimental investigation into the motion of linked spheres at low Reynolds number are presented. Small permanent magnets were embedded in the spheres and torques were generated by application of an external magnetic field. Pairs of neutrally buoyant spheres, connected by either glass rods or thin elastic struts, move in a reciprocal orbit when driven by an oscillatory field. An array of three spheres linked by elastic struts buckles in a periodic, non-reciprocal manner. The induced magneto-elastic buckling propels the elemental swimmer and we find that the geometrical asymmetry of the device, introduced by the struts of different lengths, determines the swimming direction. We propose that this novel method of creating movement remotely is suitable for miniaturization.

  9. X-ray Tomography Characterisation of Lattice Structures Processed by Selective Electron Beam Melting

    Directory of Open Access Journals (Sweden)

    Everth Hernández-Nava

    2017-08-01

    Full Text Available Metallic lattice structures intentionally contain open porosity; however, they can also contain unwanted closed porosity within the structural members. The entrained porosity and defects within three different geometries of Ti-6Al-4V lattices, fabricated by Selective Electron Beam Melting (SEBM, is assessed from X-ray computed tomography (CT scans. The results suggest that horizontal struts that are built upon loose powder show particularly high (~20 × 10−3 vol % levels of pores, as do nodes at which many (in our case 24 struts meet. On the other hand, for struts more closely aligned (0° to 54° to the build direction, the fraction of porosity appears to be much lower (~0.17 × 10−3% arising mainly from pores contained within the original atomised powder particles.

  10. Modeling of Supersonic Combustion Systems for Sustained Hypersonic Flight

    Directory of Open Access Journals (Sweden)

    Stephen M. Neill

    2017-11-01

    Full Text Available Through Computational Fluid Dynamics and validation, an optimal scramjet combustor has been designed based on twin-strut Hydrogen injection to sustain flight at a desired speed of Mach 8. An investigation undertaken into the efficacy of supersonic combustion through various means of injection saw promising results for Hydrogen-based systems, whereby strut-style injectors were selected over transverse injectors based on their pressure recovery performance and combustive efficiency. The final configuration of twin-strut injectors provided robust combustion and a stable region of net thrust (1873 kN in the nozzle. Using fixed combustor inlet parameters and injection equivalence ratio, the finalized injection method advanced to the early stages of two-dimensional (2-D and three-dimensional (3-D scramjet engine integration. The overall investigation provided a feasible supersonic combustion system, such that Mach 8 sustained cruise could be achieved by the aircraft concept in a computational design domain.

  11. Mobile work station concept for assembly of large space structures (zero gravity simulation tests)

    Science.gov (United States)

    Heard, W. L., Jr.; Bush, H. G.; Wallsom, R. E.; Jensen, J. K.

    1982-01-01

    The concept presented is intended to enhance astronaut assembly of truss structure that is either too large or complex to fold for efficient Shuttle delivery to orbit. The potential of augmented astronaut assembly is illustrated by applying the result of the tests to a barebones assembly of a truss structure. If this structure were assembled from the same nestable struts that were used in the Mobile Work Station assembly tests, the spacecraft would be 55 meters in diameter and consist of about 500 struts. The struts could be packaged in less than 1/2% of the Shuttle cargo bay volume and would take up approximately 3% of the mass lift capability. They could be assembled in approximately four hours. This assembly concept for erectable structures is not only feasible, but could be used to significant economic advantage by permitting the superior packaging feature of erectable structures to be exploited and thereby reduce expensive Shuttle delivery flights.

  12. Challenges of Designing a 13-Hz High-Load Vibration Isolation System with Tight Volume Constraints: Lessons Learned and Path Forward

    Science.gov (United States)

    Dearing, Stella; Ruebsamen, Dale

    2016-01-01

    This paper describes the design of a passive isolation system using D-struts (Registered TradeMark) to isolate an optical payload from aircraft-borne jitter with challenging stroke per volume requirements. It discusses the use of viscoelastic-coated D-struts® that meet the customer performance and outgassing specification, NASA-1124. The result was a relatively soft isolation system, (where the first mode was 13 Hz), with each individual strut capable of withstanding loads on the order of magnitude of 623 N (140 lbf), weighing less than 910 g (2 lbm), fitting in a volume 5.1 cm (2 inches) in diameter and 12-cm (4.7-inches) long and capable of performing up to 1000 Hz without nonlinearities.

  13. Mechanisms for the functional differentiation of the propulsive and braking roles of the forelimbs and hindlimbs during quadrupedal walking in primates and felines.

    Science.gov (United States)

    Granatosky, Michael C; Fitzsimons, Aidan; Zeininger, Angel; Schmitt, Daniel

    2018-01-22

    During quadrupedal walking in most animals, the forelimbs play a net braking role, whereas the hindlimbs are net propulsive. However, the mechanism by which this differentiation occurs remains unclear. Here, we test two models to explain this pattern using primates and felines: (1) the horizontal strut effect (in which limbs are modeled as independent struts), and (2) the linked strut model (in which limbs are modeled as linked struts with a center of mass in between). Video recordings were used to determine point of contact, timing of mid-stance, and limb protraction/retraction duration. Single-limb forces were used to calculate contact time, impulses and the proportion of the stride at which the braking-to-propulsive transition (BP) occurred for each limb. We found no association between the occurrence of the BP and mid-stance, little influence of protraction and retraction duration on the braking-propulsive function of a limb, and a causative relationship between vertical force distribution between limbs and the patterns of horizontal forces. These findings reject the horizontal strut effect, and provide some support for the linked strut model, although predictions were not perfectly matched. We suggest that the position of the center of mass relative to limb contact points is a very important, but not the only, factor driving functional differentiation of the braking and propulsive roles of the limbs in quadrupeds. It was also found that primates have greater differences in horizontal impulse between their limbs compared with felines, a pattern that may reflect a fundamental arboreal adaptation in primates. © 2018. Published by The Company of Biologists Ltd.

  14. Neointimal coverage and late apposition of everolimus-eluting bioresorbable scaffolds implanted in the acute phase of myocardial infarction: OCT data from the PRAGUE-19 study.

    Science.gov (United States)

    Toušek, Petr; Kočka, Viktor; Malý, Martin; Lisa, Libor; Buděšínský, Tomáš; Widimský, Petr

    2016-06-01

    Incomplete stent apposition and uncovered struts are associated with a higher risk of stent thrombosis. No data exist on the process of neointimal coverage and late apposition status of the bioresorbable vascular scaffold (BVS) when implanted in the highly thrombogenic setting of ST-segment elevation acute myocardial infarction (STEMI). The aim of this study was to assess the serial changes in strut apposition and early neointimal coverage of the BVS using optical coherence tomography (OCT) in selected patients enrolled in the PRAGUE-19 study. Intracoronary OCT was performed in 50 patients at the end of primary percutaneous coronary intervention for acute STEMI. Repeated OCT of the implanted BVS was performed in 10 patients. Scaffold area, scaffold mean diameter and incomplete strut apposition (ISA) were compared between baseline and control OCT. Furthermore, strut neointimal coverage was assessed during the control OCT. Mean scaffold area and diameter did not change between the baseline and control OCT (8.59 vs. 9.06 mm(2); p = 0.129 and 3.31 vs. 3.37 mm; p = 0.202, respectively). Differences were observed in ISA between the baseline and control OCT (0.63 vs. 1.47 %; p OCT was performed 4-6 weeks after BVS implantation, and 100 % covered struts in two patients 6 months after BVS implantation. Persistent strut apposition and early neointimal coverage were observed after biodegradable vascular scaffold implantation in patients with acute ST-segment elevation myocardial infarction.

  15. Early vascular healing with rapid breakdown biodegradable polymer sirolimus-eluting versus durable polymer everolimus-eluting stents assessed by optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    Tada, Tomohisa, E-mail: tomohisa@dhm.mhn.de [Deutsches Herzzentrum, Technische Universität, München (Germany); Byrne, Robert A. [Deutsches Herzzentrum, Technische Universität, München (Germany); Schuster, Tibor [Institut für Medizinische Statistik und Epidemiologie, München (Germany); Cuni, Rezarta [Deutsches Herzzentrum, Technische Universität, München (Germany); Kitabata, Hironori [Wakayama Medical University, Wakayama (Japan); Tiroch, Klaus [Deutsches Herzzentrum, Technische Universität, München (Germany); Dirninger, Alfred; Gratze, Franz; Kaspar, Klaus; Zenker, Gerald [Landeskrankenhaus Bruck/Mur (Austria); Joner, Michael; Schömig, Albert; Kastrati, Adnan [Deutsches Herzzentrum, Technische Universität, München (Germany)

    2013-03-15

    Background: Differences in early arterial healing patterns after stent implantation between biodegradable and durable polymer based new generation drug-eluting stents are not well understood. The aim of this study was to compare the healing patterns of a novel rapid breakdown (≤ 8 weeks) biodegradable polymer sirolimus-eluting stent (BP-SES) with a durable polymer everolimus-eluting stent (EES) using intravascular optical coherence tomography (OCT) at 4 months. Methods: A total of 20 patients were randomly assigned to stenting with BP-SES (n = 11) or EES (n = 9). Overall intravascular imaging was available for 15 (75%) patients. The primary endpoint was the difference in rate of uncovered struts between BP-SES and EES. To account for strut-level clustering, the results in both treatment groups were compared using a generalized linear mixed model approach. Results: Regarding the primary endpoint, BP-SES as compared to EES showed similar rates of uncovered struts (37 [6.8%] versus 167 [17.5%], odds ratio (OR) 0.45 (95% CI 0.09-2.24), p = 0.33). There were no malapposed struts in BP-SES group and 14 malapposed struts in EES group (p = 0.97). No difference in percent neointimal volume (14.1 ± 8.2% vs. 11.4 ± 6.4%, p = 0.56) was observed. Conclusions: Although rapid-breakdown BP-SES as compared to EES showed signs of improved early tissue coverage, after adjustment for strut-level clustering these differences were not statistically significant. No differences in ability to suppress neointimal hyperplasia after stent implantation between 2 stents were observed.

  16. The fate of incomplete scaffold apposition of everolimus-eluting bioresorble scaffolds: A serial optical coherence tomography analysis.

    Science.gov (United States)

    Sato, Takao; Tölg, Ralph; El-Mawardy, Mohamed; Sulimov, Dmitriy S; Richardt, Gert; Abdel-Wahab, Mohamed

    2017-11-01

    Incomplete stent apposition (ISA) can be divided into acute and late forms. Late ISA may be due to persistent ISA or late-acquired ISA (LAISA). This study evaluated the natural course of ISA after bioresorbable vascular scaffold (BRS) implantation using optical coherence tomography (OCT). Thirty-two patients (45 BRS) were assessed immediately after BRS implantation and 1 year thereafter using OCT. Acute ISA identified after BRS implantation but absent at follow-up was defined as resolved; otherwise, it was considered persistent. LAISA was defined as newly developed ISA that was identified at follow-up despite complete apposition immediately after BRS implantation. Intra-BRS fibrin-like material (IBF) was identified as an irregular intraluminal mass. ISA percentage was expressed as follows: (number of ISA/total number of BRS struts)×100. Among 45 BRS and 15,894 analyzed BRS struts, 34 and 882 had acute ISA post-procedure, respectively. At follow-up, 92 of 15,364 analyzed struts exhibited late ISA (64 persistent ISA and 28 LAISA). In 15 of 28 struts with LAISA, LAISA occurred at the sites adjacent to post-interventional dissection. Uncovered struts were more frequently observed in late ISA compared to apposed struts (3.7±4.8 vs. 0.58±2.2%, p=0.09). IBF was significantly more common in BRS with late ISA (62.5 vs. 8.1%, p=0.02). Receiver-operating characteristic curve analysis identified a cut-off value of 280μm for acute ISA distance predicting persistent ISA. Resolution of acute ISA after BRS is common. The occurrence of LAISA may be infrequent and may be a nidus of stent thrombosis. Copyright © 2017 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  17. Supercavitation Advances and Perspectives A collection dedicated to the 70th jubilee of YuN Savchenko

    CERN Document Server

    2012-01-01

    This collection is dedicated to the 70th jubilee of Yu. N. Savchenko, and presents experimental, theoretical, and numerical investigations written by an international group of well-known authors. The contributions solve very important problems of the high-speed hydrodynamics, such as supersonic motion in water, drag diminishing, dynamics and stability of supercavitating vehicles, water entry and hydrodynamic performances of hydrofoils, ventilated cavities after a disc and under the ship bottom. The  book is written for researches, scientists, engineers, and students interested in problems of hydromechanics.

  18. National standards for ACV's and the IMO code - 'Putting flesh on the skeleton'

    Science.gov (United States)

    Wade, R. G.

    The 'Code of Safety for Dynamically Supported Craft' is the international safety standard developed for air-cushion vehicles (ACVs), surface-effect ships, hydrofoils, etc. The relationship between this code and national domestic standards is presently discussed in light of Canadian Coast Guard experience to date. Several of the mode definitive requirements of the international code are noted to be in need of modification; attention is also drawn to cases in which a nationally-certified ACV will conform to the international code, but not to the standards of another nation which nevertheless conform with the international code.

  19. Indian Defense Policy, Its Implications for Nepal.

    Science.gov (United States)

    1986-04-15

    defended at the Hindu Kush, the Himalayas, the Malacca Straits and A Bab- el Mandab, it not the Suez.9 Senior military leaders still support this view...attack thereby reinforcing the traditional concept of a defense based on the Hindu Kush, the Himalayas, the Malacca Straits and Bab- el Mandab. After...Shanghai-II FAC(T). 4 Ch Huchwan hydrofoil FAC(T). 3 US Adjutant and MSC268 coastal MCM. 2 tankers (1 ocean, 1 coastal), 1 Br Oido cruiser (cadet trg/AA

  20. Prospectively electrocardiogram-triggered high-pitch spiral acquisition coronary computed tomography angiography for assessment of biodegradable vascular scaffold expansion: Comparison with optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    D’Alfonso, Maria Grazia [Interventional Cardiology Unit University Of Florence, Heart and Vessels department, AOU Careggi, Florence (Italy); Mattesini, Alessio, E-mail: amattesini@gmail.com [Interventional Cardiology Unit University Of Florence, Heart and Vessels department, AOU Careggi, Florence (Italy); Meucci, Francesco [Interventional Cardiology Unit University Of Florence, Heart and Vessels department, AOU Careggi, Florence (Italy); Acquafresca, Manlio [Radiology Unit 4, Radiology Department, AOU Careggi, Florence (Italy); Gensini, Gian Franco; Valente, Serafina [Interventional Cardiology Unit University Of Florence, Heart and Vessels department, AOU Careggi, Florence (Italy)

    2014-11-15

    BVS polymeric struts are transparent to the light so that the vessel wall contour can be easily visualized using optical coherence tomography (OCT). Therefore OCT represents a unique tool for both the evaluation of the resorption process and for the assessment of acute BVS mechanical failure. Similarly, the metal-free struts allow unrestricted coronary computed tomography angiography (CCTA), thus this non invasive method might become the gold standard for a non invasive assessment of BVS. In this case we show the ability of CCTA, performed with a low X-Ray dose, to provide a good evaluation of scaffold expansion. The quantitative measurements were in agreement with those obtained with OCT.

  1. Study of Forebody Injection and Mixing with Application to Hypervelocity Airbreathing Propulsion

    Science.gov (United States)

    Axdahl, Erik; Kumar, Ajay; Wilhite, Alan

    2012-01-01

    The use of premixed, shock-induced combustion in the context of a hypervelocity, airbreathing vehicle requires effective injection and mixing of hydrogen fuel and air on the vehicle forebody. Three dimensional computational simulations of fuel injection and mixing from flush-wall and modified ramp and strut injectors are reported in this study. A well-established code, VULCAN, is used to conduct nonreacting, viscous, turbulent simulations on a flat plate at conditions relevant to a Mach 12 flight vehicle forebody. In comparing results of various fuel injection strategies, it is found that strut injection provides the greatest balance of performance between mixing efficiency and stream thrust potential.

  2. Transverse partial stent ablation with rotational atherectomy for suboptimal culotte technique in left main stem bifurcation.

    Science.gov (United States)

    De Maria, Giovanni Luigi; Kharbanda, Rajesh; Banning, Adrian P

    2017-11-06

    Longitudinal rotational atherectomy of metal struts is well described as bail-out strategy to treat undilatable instent restenosis. Ablation of metal stent struts jailing the ostium of a major side branch in a coronary bifurcation is not described. In the current report, we describe a case of "transverse" rotational atherectomy to treat a failure of culotte stenting in a left main stem bifurcation. We document for the first time in vivo and in man the effect of this strategy using optical coherence tomography. © 2017 Wiley Periodicals, Inc.

  3. Trusses Of Tensegrity Type In A Concept Of Train Station Renovation In Żary

    Directory of Open Access Journals (Sweden)

    Lechocka Paulina

    2015-09-01

    Full Text Available The first railway station in Żary was built in 1843 in Germany. After the Second World War and years of socialism in Poland the meaning of railway decreased and its technical condition deteriorated. Now the building needs renovation and change of function. Tensegrity structures may be useful in renovation of platforms shelter. They are strut and tie construction, in which there is self-stabilization between compressed and tensioned elements. Conception of new platform shelter is based on exemplary tensegrity module consist of three struts and nine cables (called „Simplex”. Tensegrity would make railway station more modern, but not cover its original elevation.

  4. Variable volume combustor with aerodynamic fuel flanges for nozzle mounting

    Science.gov (United States)

    McConnaughhay, Johnie Franklin; Keener, Christopher Paul; Johnson, Thomas Edward; Ostebee, Heath Michael

    2016-09-20

    The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and for providing the flow of fuel therethrough. The fuel injection system also may include a number of aerodynamic fuel flanges connecting the micro-mixer fuel nozzles and the support struts.

  5. Advanced Technology Helicopter Landing Gear Preliminary Design Investigation

    Science.gov (United States)

    1985-10-01

    helicopter studied, the criteria for attitudes and sink rates to develop landing gear loads should be as follows: * The peak design load in the shock...baseline shock struts and the shock struts required for the peak load at 42 feet per second -5 deg pifrh and 15 deg roll. Baseline design load Peak ... design load P = 50,390 lb P = 57,000 lbcB C Pressure = 6074 psi Pressure = 6870 psi Lower Piston Sections C-C and G-G (Figures 26 and 27) O-D = 3.250 4340

  6. Collet lock joint for space station truss

    Science.gov (United States)

    Wesselski, Clarence J. (Inventor)

    1988-01-01

    A lock joint for a Space Station has a series of struts joined together in a predetermined configuration by node point fittings. The fittings have removeable inserts. The lock joint has an elongated housing connected at one end to a strut. A split-fingered collet is mounted within the housing to insure reciprocal movement. A handle on the housing is connected to the collet for moving the collet into the insert where the fingers of the collet expand to lock the joint to the fitting.

  7. Serial 5-Year Evaluation of Side Branches Jailed by Bioresorbable Vascular Scaffolds Using 3-Dimensional Optical Coherence Tomography: Insights From the ABSORB Cohort B Trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions).

    Science.gov (United States)

    Onuma, Yoshinobu; Grundeken, Maik J; Nakatani, Shimpei; Asano, Taku; Sotomi, Yohei; Foin, Nicolas; Ng, Jaryl; Okamura, Takayuki; Wykrzykowska, Joanna J; de Winter, Robbert J; van Geuns, Robert-Jan; Koolen, Jacques; Christiansen, Evald; Whitbourn, Robert; McClean, Dougal; Smits, Pieter; Windecker, Stephan; Ormiston, John A; Serruys, Patrick W

    2017-09-01

    The long-term fate of Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, CA) struts jailing side branch ostia has not been clarified. We therefore evaluate serially (post-procedure and at 6 months, 1, 2, 3, and 5 years) the appearance and fate of jailed Absorb bioresorbable vascular scaffold struts. We performed 3-dimensional optical coherence tomographic analysis of the ABSORB Cohort B trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions) up to 5 years using a novel, validated cut-plane analysis method. We included 29 patients with a total of 85 side branch ostia. From the 12 ostia which could be assessed in true serial fashion, 7 showed a pattern of initial decrease in the ostial area free from struts, followed by an increase in strut-free ostial area toward the end of the 5 years of follow-up. In a repeated-measures analysis with time as fixed variable and ostial area free from struts as dependent variable, we showed a numeric decrease in the estimated ostial area free from struts from 0.75 mm 2 (baseline) to 0.68 mm 2 (first follow-up visit at 6 months or 1 year) and 0.63 mm 2 (second follow-up visit at 2 or 3 years). However, from the second visit to the 5-year follow-up visit, there was a statistically significant increase from 0.63 to 0.89 mm 2 ( P =0.001). Struts overlying an ostium divided the ostium into compartments, and the number of these compartments decreased over time. This study showed that in most cases, the side branch ostial area free from struts initially decreased. However, with full scaffold bioresorption, the ostial area free from scaffold increased between 2 to 3 years and 5 years in the vast majority of patients. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00856856. © 2017 American Heart Association, Inc.

  8. A Hafnium-Based Metal–Organic Framework as a Nature-Inspired Tandem Reaction Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Beyzavi, M. Hassan [International; Vermeulen, Nicolaas A. [International; Howarth, Ashlee J. [International; Tussupbayev, Samat [Department; League, Aaron B. [Department; Schweitzer, Neil M. [International; Gallagher, James R. [Chemical; Platero-Prats, Ana E. [X-ray; Hafezi, Nema [International; Sarjeant, Amy A. [International; Miller, Jeffrey T. [Chemical; School; Chapman, Karena W. [X-ray; Stoddart, J. Fraser [International; Cramer, Christopher J. [Department; Hupp, Joseph T. [International; Farha, Omar K. [International; Department

    2015-10-15

    Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new MOF with porphyrinic struts and Hf6 nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when a Fe-decorated Hf6-node and the Fe-porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis.

  9. A Hafnium-Based Metal-Organic Framework as a Nature-Inspired Tandem Reaction Catalyst.

    Science.gov (United States)

    Beyzavi, M Hassan; Vermeulen, Nicolaas A; Howarth, Ashlee J; Tussupbayev, Samat; League, Aaron B; Schweitzer, Neil M; Gallagher, James R; Platero-Prats, Ana E; Hafezi, Nema; Sarjeant, Amy A; Miller, Jeffrey T; Chapman, Karena W; Stoddart, J Fraser; Cramer, Christopher J; Hupp, Joseph T; Farha, Omar K

    2015-10-28

    Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new metal-organic framework (MOF) with porphyrinic struts and Hf6 nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when an Fe-decorated Hf6 node and the Fe-porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis.

  10. Omental flap transposition for inferior vena cava filter penetration

    Directory of Open Access Journals (Sweden)

    Junji Yamaguchi, MD

    2017-03-01

    Full Text Available A 40-year-old woman presented with uterine malignancy, deep vein thrombosis, and nonmassive pulmonary embolism in both lungs. Gunter-tulip filter was inserted, because she had severe genital bleeding, which is one of the contraindications to anticoagulation therapy. Total hysterectomy was conducted and anticoagulation therapy was started afterward. The thrombus worsened perioperatively, and the filter could not be retrieved. Since there was lymph node recurrence, the second time operation was performed. During operation, the struts were found to be penetrating the inferior vena cava. Omental flap was used to cover the struts, and no associated complications occurred after operation.

  11. Summary of monographs made public in the 93rd meeting by West Japan Society of Naval Architects. Lecture meeting sponsored jointly by three shipbuilding societies for fall in 1996; Seibu zosenkai dai 93 kai reikai ronbun kogai. 1996 nendo shuki zosen sangakukai rengo koenkai

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-01

    A lecture meeting sponsored by the three ship building societies for fall in 1996 was held on November 14 and 15, 1996 at the Hiroshima Prefecture Information Plaza, where 16 monographs were presented. With regard to fluid dynamic problems in vessels, reports were given on experimental studies on performance of tandem hydrofoils in highspeed regions, solution methods for non-steady two-dimensional hydrofoil problems by using a simple panel method, a consideration on lateral inclination during maneuvering operation, and a new prediction approach for ships maneuvering hydrodynamics. With respect to structural material strength, reports were made on one consideration on buckling and plastic breakdown strength characteristics of surface fine grain steel plates, a study on buckling and final strength of square plates subjected to load in combined planes, and one consideration on evaluating life to generate corrosion fatigue cracking. Other reports were also given on a theoretical study on sea shock load acting on two-dimensional floating bodies, a study on a method for setting design hydrographic conditions, and a numerical simulation on flow and density field in the Kagoshima bay in summer by using a multi-layer model.

  12. Pengaruh Posisi Foil Terhadap Gaya Angkat Dan Hambatan Kapal Katamaran

    Directory of Open Access Journals (Sweden)

    Muhammad Rizki Darmawan Adi Kusuma

    2017-08-01

    Full Text Available Perkembangan teknologi dalam dunia perkapalan terjadi sangat pesat, mulanya kapal memiliki satu lambung (monohull, kemudian berkembang dengan munculnya kapal katamaran atau memiliki dua lambung, kapal katamaran memiliki banyak kelebihan dibanding dengan monohull mulai dari segi hambatan, olah gerak, dan lain-lain. Kapal katamaran akhirnya dikembangkan lagi dengan menjadikannya kapal hydrofoil yang bertujuan untuk mengurangi hambatan. Hydrofoil adalah sebuah kapal dengan bagian seperti sayap yang dipasang pada penyangga di bawah lambung kapal yang digunakan untuk mengangkat lambung kapal, pada saat kapal mencapai kecepatan tinggi yang menyebabkan pengurangan hambatan. Pada penelitian ini bertujuan untuk mendapatkan konfigurasi posisi foil yang menghasilkan gaya angkat paling besar serta hambatan yang paling kecil. Dalam melaksanakan penelitian ini penulis menggunakan program komputer berbasis Computational Fluid Dynamic(CFD untuk penyelesaian masalah dari tujuan penelitian, Computational fluid dynamic(CFD merupakan ilmu sains dalam penentuan penyelesaian numerik dinamika fluida.Penelitian dilakukan dengan cara menganalisa dan menghitung hambatan total kapal menggunakan model.Berdasarkan hasil analisa menggunakan software Tdyn 12.2.3.0 didapatkan nilai hambatan untuk berbagai variasi konfigurasi foil. Nilai hambatan total dapat diperkecil  hingga 37,56%, nilai ini terjadi pada Froude Number 1,737 pada variasi konfigurasi Canard dengan konfigurasi 65%(aft dan 35%(fore.

  13. Intermittent Swimming with a Flexible Propulsor

    Science.gov (United States)

    Akoz, Emre; Moored, Keith

    2017-11-01

    Aquatic animals use a variety of swimming gaits to propel themselves efficiently through the oceans. One type of gait known as intermittent or burst-and-coast swimming is used by species such as saithe, cod and trout. Recent studies have shown that this gait can save up to 60% of a swimmer's energy by exploiting an inviscid Garrick mechanism. These detailed studies have examined the effects of an intermittent swimming gait on rigid propulsors, yet the caudal fins of intermittent swimmers are in fact highly flexible propulsors. In this respect, to gain a comprehensive understanding of intermittent swimming, the effect of elasticity on the swimming performance and wake flow of an intermittent swimmer is investigated. To accomplish this a torsional spring structural model is strongly coupled to a fast boundary element method solver that captures the fluid-structure interaction of a two-dimensional self-propelled intermittently pitching hydrofoil. It is shown that flexibility introduces extra vortices to the coasting phase of motion that can either promote or diminish thrust production depending upon the hydrofoil parameters. An optimal intermittent flexible swimmer is shown to increase its efficiency by as much as 28% when compared to an optimal continuous flexible swimmer. Supported by the Office of Naval Research under Program Director Dr. Bob Brizzolara, MURI Grant Number N00014-14-1-0533.

  14. Kinetics of enzymatic synthesis of liquid wax ester from oleic acid and oleyl alcohol.

    Science.gov (United States)

    Radzi, Salina Mat; Mohamad, Rosfarizan; Basri, Mahiran; Salleh, Abu Bakar; Ariff, Arbakariya; Rahman, Mohammad Basyaruddin Abdul; Rahman, Raja Noor Zaliha Raja Abdul

    2010-01-01

    The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 2l stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively.

  15. Novel concepts for the containment of oil in flowing water

    International Nuclear Information System (INIS)

    Brown, H.M.; Nicholson, P.; Goodman, R.H.; Berry, B.A.; Hughes, B.R.

    1993-01-01

    Both a laboratory study of the hydrodynamic properties of variously shaped objects and a meso-scale flume study of several containment concepts have been undertaken to determine whether these can be used to contain oil in fast flowing water. The laboratory study showed that stable vortices are difficult to generate and that spilled oil is not easily trapped by them. Only two of the structures studied showed some promise of trapping oil in fast moving water: a partially submerged barrier with fins placed at an angle across the flume and a horizontal hydrofoil placed across the channel near the surface. Several filter materials were tested in an outdoor flowing channel with both floating and neutrally buoyant oil. Although some of these materials trapped and held heavy oil, they were not a significant improvement over nylon fishing nets which had been tested previously. The filter materials would not hold a medium gravity oil. A hydrofoil device which generated a horizontal eddy successfully trapped and held surface oil at water speeds up to 0.35 m/s. Neutrally buoyant oil was often caught by the eddy but was never held for more than 1-2 minutes. 9 refs., 5 figs., 3 tabs

  16. An experimental study on suppressing Tip Vortex Cavitation by means of a Flexible Thread

    Science.gov (United States)

    Seo, Jeonghwa; Amini, Ali; Lee, Seung Jae; Park, Jongyeol; Yeo, Honggu; Farhat, Mohamed; Rhee, Shin Hyung

    2017-11-01

    Tip vortex cavitation (TVC) is an important issue in hydraulic machines and efforts to reduce it are required. The present study aims to mitigate the intensity of a TVC by attaching a flexible thread at the hydrofoil tip. As the test model, a hydrofoil with elliptical planform with NACA 16-020 cross section was used. Reynolds number, incidence angle, and cavitation number were varied to examine the cavitation suppression effects under different flow conditions. It is observed that the size of the cavitating core of the tip vortex is drastically reduced in comparison to the same flow conditions without the thread. The vortex roll-up and formation was disturbed by the fluctuations of the flexible string around the TVC, resulting in cavitation intensity reduction. In addition, the thread diameter and length were varied, to show that the technique was proved effective even for strings as short as half of the root chord length, which acted like a stiff thread. Our results demonstrate that there exists a critical thread length of, where the decrease in the cavitating core diameter converges. It is also found that this recipe ameliorates the desinent cavitation index of the TVC.

  17. Proceedings of the Spring Meeting of the Society of Naval Architects of Japan (1996). Part 1. Resistance, propulsion, advance, and ocean; Nihon zosen gakkai (1996 nen) shunki koen ronbun maezuri. 1. Teiko, suishin shindo, kaiyo

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    This is a proceedings of the Spring Meeting of the Society of Naval Architects of Japan made public on May 15 and 16, 1996. In the basic research, the following were included: Numerical simulation for submerged body fitted with hydrofoil; Simulation of tandem hydrofoils by finite volume method with moving grid system; Determination of the unknown method surface of planning plates by a formulation based on high aspect ratio approximation; Numerical simulation of a bubble flow by modified density function method, etc. As to floating bodies, Response characteristics of a long life type floating offshore airport in waves (3rd report: Response due to short waves and an attempt of active inclination control); Feasibility design of a floating airport and estimation of environmental forces on it; On the estimation method of hydrodynamic forces acting on a huge floating structure, etc. In addition, A numerical prediction with `DMDF` model of pack ice motion in the Okhotsk Sea; Development of an observation robot `Flying Fish` for comprehensive measurements of ocean environment; Water entry simulation of free-fall lifeboat, etc.

  18. 78 FR 8107 - Certain Steel Wire Garment Hangers From the Socialist Republic of Vietnam: Countervailing Duty Order

    Science.gov (United States)

    2013-02-05

    .... SUPPLEMENTARY INFORMATION: Case History In accordance with section 705(d) of the Tariff Act of 1930, as amended... shirt, suit, strut, caped, or latex (industrial) hangers. Specifically excluded from the scope are (a...) (collectively, the Hamico Companies) Infinite Industrial Hanger Limited (Infinite) and 90.42 Supreme Hanger...

  19. Research Article

    African Journals Online (AJOL)

    2016-06-11

    Jun 11, 2016 ... n this article we try to explain the usage of tie-and-strut method a g this method in design of ... economical usage and ability to using them repeatedly (formwork system), the possibility of using the larger .... connecting regions have sufficient plastic deformation capacity, understanding of its behaviour will be ...

  20. Mr. Rooster

    Directory of Open Access Journals (Sweden)

    Joyce Carol Oates

    2017-05-01

    Full Text Available The behavior of barnyard roosters, replicating the more belligerent, strutting-preening-aggressive macho behavior of many male creatures, was a source of endless fascination, and trepidation, to me as a young child growing up on a small farm in the “north country” of western New York State.

  1. Aortic stentgrafts and en dovascular abdominal aortic aneurysm repair

    African Journals Online (AJOL)

    2007-07-19

    Jul 19, 2007 ... with or without hooks or barbs attached to the proximal covered stent), or suprarenal with uncovered metal stent struts that maintain perfusion of the renal arteries, while the infrarenal covered component provides the seal. Distally, a seal requires normal common iliac arteries. Associated iliac aneurysms.

  2. A Survey of Serious Aircraft Accidents Involving Fatigue Fracture. Volume 2. Rotary-Wing Aircraft (Etude sur des Accidents Importants d’Avions du aux Effets des Fractures de Fatigue. Volume 2. Effets sur des Helicopteres).

    Science.gov (United States)

    1983-04-01

    Japan NoT. NI08 Bell 2063 3 Jun 79 0 D Morgan City, La. USA. Turbine blade. NTSB file 3-2100. N109 Fairchild 25 Jul 79 0 S Riviere Eternite , Que. Canada...transmission lift link strut failed. Role: aerial logging. N109 Fairchild 25 Jul 79 0 S Riviere Eternite , Que. Canada. FH-1100 Abraidable plastic

  3. Java Web Frameworks Which One to Choose?

    OpenAIRE

    Nassourou, Mohamadou

    2010-01-01

    This article discusses web frameworks that are available to a software developer in Java language. It introduces MVC paradigm and some frameworks that implement it. The article presents an overview of Struts, Spring MVC, JSF Frameworks, as well as guidelines for selecting one of them as development environment.

  4. Chronic Pain Syndrome Caused by a Bird's Nest Filter: First Case Report

    International Nuclear Information System (INIS)

    Al-Basheer, Mamoun Ahmad; Hamilton, Mark; Holdaway, Chris

    2008-01-01

    AimTo report the first case of a Bird's Nest IVC filter causing a chronic pain syndrome lasting 13 years through IVC wall penetration and subsequent break off of one of the filter struts.Materials and ResultsA 43-year-old female presented with a 13-year history of abdominal pain following uneventful insertion of a Bird's Nest vena cava filter through a right internal jugular percutanous approach. A year following the procedure, CT scan revealed one arm of the filter to be outside IVC borders. Nine years from the date of insertion the nature of the pain changed acutely following a five feet jump to more localized RUQ pain worse with twisting movements. A CT scan showed the strut to have pierced the IVC wall and penetrated the Unicate process of pancreas. Plain x-rays taken at different times in February 2006 showed one of the struts to be free floating in the peritoneal cavity. The floating strut was removed surgically from the wall of the Ileum. Postoperative recovery was uneventful and the patient was discharged pain free three days later.ConclusionChronic pain is an added complication of BNF devices. Although rare, it further emphasizes the need for long-term follow up of patients with IVC filters.

  5. Outcome of a posterior spinal fusion technique using spinous ...

    African Journals Online (AJOL)

    Adeolu and Komolafe: Posterior spinal fusion with spinous process wire and vertical strut. Introduction ... risk of injuring the canal contents on both short and ... Patient population. Patients were informed about the technique and availability of other spinal fusion options and potential advantages and disadvantages were.

  6. Morphological and mechanical properties of the posterior leaflet chordae tendineae in the mitral valve

    NARCIS (Netherlands)

    Lodder, J.; Verkerke, Gijsbertus Jacob; Delemarre, B.J.M.; Dodou, D.

    2016-01-01

    A number of studies have investigated the morphological and mechanical properties of the chordae tendineae of the mitral valve, providing comparisons between basal, marginal, and strut chordae and between chordae at the anterior and posterior leaflets. This study contributes to the literature by

  7. Morphological and mechanical properties of the posterior leaflet chordae tendineae in the mitral valve

    NARCIS (Netherlands)

    Lodder, Joost; Verkerke, Gijsbertus J.; Delemarre, Ben J. M.; Dodou, Dimitra

    A number of studies have investigated the morphological and mechanical properties of the chordae tendineae of the mitral valve, providing comparisons between basal, marginal, and strut chordae and between chordae at the anterior and posterior leaflets. This study contributes to the literature by

  8. Return to Running and Sports Participation After Limb Salvage

    Science.gov (United States)

    2011-07-01

    agility training without an increase in pain. The majority of TABLE 1. Sample Strength Progressions Strength: Knee Dominant Strength: Hip Dominant Box squat...providing energy return through the posterior strut, much like an amputation running prosthesis . Therefore, our patients with limited ankle mobility

  9. Sadhana | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Fracture and Fatigue: Some New Insights. pp 1-1. Foreword ... pp 3-15. Effect of loading condition, specimen geometry, size-effect and softening function on double- fracture parameters of concrete .... pp 89-105. Evaluation of size effect on shear strength of reinforced concrete deep beams using refined strut-and-tie model.

  10. ( Anogeissus leiocarpus ) timber columns

    African Journals Online (AJOL)

    A procedure for designing axially loaded Ayin (Anogeissus leiocarpus) wood column or strut has been investigated. Instead of the usual categorization of columns into short, intermediate and slender according to the value of slenderness ratio, a continuous column formula representing the three categories was derived.

  11. A Teaching Model for Truss Structures

    Science.gov (United States)

    Bigoni, Davide; Dal Corso, Francesco; Misseroni, Diego; Tommasini, Mirko

    2012-01-01

    A classroom demonstration model has been designed, machined and successfully tested in different learning environments to facilitate understanding of the mechanics of truss structures, in which struts are subject to purely axial load and deformation. Gaining confidence with these structures is crucial for the development of lattice models, which…

  12. Preclinical Evaluation of Degradation Kinetics and Elemental Mapping of First and Second Generation Bioresorbable Magnesium Scaffolds.

    Science.gov (United States)

    Joner, Michael; Ruppelt, Philipp; Zumstein, Philine; Lapointe-Corriveau, Capucine; Leclerc, Guy; Bulin, Anna; Castellanos, Maria Isabel; Wittchow, Eric; Haude, Michael; Waksman, Ron

    2018-02-20

    Because vascular restoration therapy using bioresorbable vascular scaffolds (BRS) remains an appealing concept to restore vasoreactivity, understanding of biodegradation remains paramount during preclinical testing. Qualitative characterization of biodegradation was performed in 41 DREAMS 1G up to 3 years, while degradation kinetics were acquired in 54 DREAMS 2G implanted into porcine coronary arteries for 28, 90 and 180 days, 1 and 2 years. Assessment of end product composition was achieved in DREAMS 2G at 180 days. Myocardium was examined, while an OCT attenuation score was derived at strut-level from 180 days to 2 years in DREAMS 2G. Degradation of DREAMS entails two corrosive phases. At 1 year, 94.8% of the magnesium was bioabsorbed in DREAMS 2G and at 2 years, magnesium was completely replaced by amorphous calcium phosphate. Von Kossa staining revealed variable peri-strut mineralization at all time points and only small focal myocardial emboli observed in 1 animal of the 180 days cohort. Strut discontinuity density was low at 28 days (of 0.5 ± 0.57 per mm) and increased to a density above 7.5 per mm up to 1 year. OCT attenuation score correlated well with strut-based degradation analysis up to 2 years. While the current set of data supports vascular safety, clinical trials are warranted to prove the concept of vascular restoration following DREAMS implantation.

  13. Copepoda: Siphonostomatoida

    African Journals Online (AJOL)

    1987-04-13

    Apr 13, 1987 ... movable (Kabata & Hewitt 1971) it appears probable that the sternal furca may be functional in acting as a supporting strut during attachment, thus enlarging the area under the cephalothorax and consequently the suction, which is necessary for attachment, as suggested by Wilson (1905). The presence of ...

  14. Dynamic Stability Parameters

    Science.gov (United States)

    1981-05-01

    on an aircraft fuselage or a slender body, as is demonstrated by the results obtained by Ruben 1 for his strut design (Fig. 13). Perkins showed the...are unique and demonstrate a very successful symbiosis of the powerful and flexible tool of parameter identification together with highly qualified

  15. Fulltext PDF

    Indian Academy of Sciences (India)

    Punjabi to UNL enconversion system. 299. Deep beams. Evaluation of size effect on shear strength of reinforced concrete deep beams using refined strut-and-tie model. 89. Degree of coupling. Degree of coupling in high-rise mixed shear walls structures. 481. Depth of penetration. Simulation of depth of penetration during.

  16. Photographic replica of the plaque Apollo 13 astronauts will leave on moon

    Science.gov (United States)

    1970-01-01

    A photographic replica of the plaque which the Apollo 13 astronauts will leave behind on the Moon during their lunar landing mission. The plaque will be attached to the ladder on the landing gear strut on the Lunar Module's descent stage.

  17. Photographic replica of plaque Apollo 15 astronauts will leave on Moon

    Science.gov (United States)

    1971-01-01

    A photographic replica of the plaque which Apollo 15 astronauts will leave behind on the Moon during their lunar landing mission. The seven by nine-inch stainless steel plaque will be attached to the ladder on the landing gear strut on the Lunar Module's descent stage.

  18. View of replica of plaque Apollo 12 astronauts will leave on the Moon

    Science.gov (United States)

    1969-01-01

    Close-up view of a replica of the plaque which the Apollo 12 astronauts will leave on the Moon in commemoration of their flight. The plaque will be attached to the ladder on the landing gear strut on the descent stage of the Apollo 12 Lunar Module.

  19. View of plaque Apollo 11 astronauts left on moon

    Science.gov (United States)

    1969-01-01

    Closeup view of the plaque which the Apollo 11 astronauts left on the moon in commemoration of the historic lunar landing mission. The plaque was attached to the ladder on the landing gear strut on the descent stage of the Apollo 11 Lunar Module. The plaque was covered with a thin sheet of stainless steel during flight.

  20. Soft-Capture Mechanism For Collet Joint

    Science.gov (United States)

    Huff, John E., Jr.

    1992-01-01

    Soft-capture mechanism part of latching-and-rigidifying mechanism joining strut rigidly to node on truss. Latching-and-rigidifying mechanism of spreading-collet type, in which collet inserted into base that mates with collet to assure proper alignment, then collet spread to rigidify joint, fixing alignment. Designed to be operable by heavily gloved hand or by robot.

  1. Robot Would Assemble Collet/Flexible-Drive Truss Joint

    Science.gov (United States)

    Evenson, Erik E.; Wesselski, Clarence J.; Ruiz, Steve

    1992-01-01

    Proposed truss joint designed for assembly by robot. Requires only simple motions of end effector of robot, tolerates relatively large initial misalignment of strut, and assembled with little feedback. Principal features of joint: expanding collet latches it to node ball and collet expanded by flexible drive shaft operated by robot. Developed for Space Station, also used for robotic construction in hazardous or undersea locations.

  2. Using Angle calculations to demonstrate vowel shifts

    DEFF Research Database (Denmark)

    Fabricius, Anne

    2008-01-01

    This paper gives an overview of the long-term trends of diachronic changes evident within the short vowel system of RP during the 20th century. more specifically, it focusses on changing juxtapositions of the TRAP, STRUT and LOT, FOOT vowel centroid positions. The paper uses geometric calculation...

  3. Evaluation and analysis of the performance of masonary infills during the Northridge earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, R.M.; Fischer, W.L. [Univ. of Tennessee, Knoxville, TN (United States); Flanagan, R.D.; Tenbus, M.A. [Lockheed Martin, Oak Ridge, TN (United States)] [and others

    1996-02-01

    Observations were made of the behavior of masonry infills in structural frames during the Northridge earthquake, and an analytical technique was developed for analyzing infilled frame structures. Infills near the epicenter suffered significant damage, but in several cases contributed to the seismic resistance and life safety performance. Older infill buildings in downtown Los Angeles experienced intensity of shaking similar to that expected in central/eastern United States earthquakes. The infills experienced some cracking, but otherwise complemented the lateral resistance of the weak building frames. This suggests infill frame buildings in moderate seismic zones may provide at least life safety functions without the need for expensive retrofit. A developed analytical technique was used to analyze two buildings for which the observed behavior and records from the Northridge earthquake were available. The analytical technique was based on using a piecewise linear equivalent strut for the infill. Parameters for the strut were obtained by examining the results of a wide variety of experimental infill tests. The strut method is easy to incorporate in standard linear analyses, and converges quite rapidly. The strut method was applied to two structures that had records from the Northridge earthquake. Very favorable comparisons between the analytical method and observed response were obtained. Recommendations were made concerning evaluation of the vulnerability of infills to earthquakes, and the construction of infills.

  4. Serial 5-Year Evaluation of Side Branches Jailed by Bioresorbable Vascular Scaffolds Using 3-Dimensional Optical Coherence Tomography: Insights From the ABSORB Cohort B Trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions)

    NARCIS (Netherlands)

    Onuma, Y.; Grundeken, M.J.; Nakatani, S.; Asano, T.; Sotomi, Y.; Foin, N.; Ng, J.; Okamura, T.; Wykrzykowska, J.J.; Winter, R.J. de; Geuns, R.J.M. van; Koolen, J.; Christiansen, E.; Whitbourn, R.; McClean, D.; Smits, P; Windecker, S.; Ormiston, J.A.; Serruys, P.W.

    2017-01-01

    BACKGROUND: The long-term fate of Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, CA) struts jailing side branch ostia has not been clarified. We therefore evaluate serially (post-procedure and at 6 months, 1, 2, 3, and 5 years) the appearance and fate of jailed Absorb

  5. Serial 5-Year Evaluation of Side Branches Jailed by Bioresorbable Vascular Scaffolds Using 3-Dimensional Optical Coherence Tomography Insights From the ABSORB Cohort B Trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions)

    NARCIS (Netherlands)

    Onuma, Yoshinobu; Grundeken, Maik J.; Nakatani, Shimpei; Asano, Taku; Sotomi, Yohei; Foin, Nicolas; Ng, Jaryl; Okamura, Takayuki; Wykrzykowska, Joanna J.; de Winter, Robbert J.; van Geuns, Robert-Jan; Koolen, Jacques; Christiansen, Evald; Whitbourn, Robert; McClean, Dougal; Smits, Pieter; Windecker, Stephan; Ormiston, John A.; Serruys, Patrick W.

    2017-01-01

    Background-The long-term fate of Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, CA) struts jailing side branch ostia has not been clarified. We therefore evaluate serially (post-procedure and at 6 months, 1, 2, 3, and 5 years) the appearance and fate of jailed Absorb

  6. Nickel( ii ) and copper( i , ii )-based metal-organic frameworks incorporating an extended tris-pyrazolate linker

    Energy Technology Data Exchange (ETDEWEB)

    Tăbăcaru, Aurel [Scuola di Scienze del Farmaco e dei Prodotti della Salute; Università di Camerino; 62032 Camerino, Italy; Department of Chemistry; Physics and Environment; Galli, Simona [Dipartimento di Scienza e Alta Tecnologia; Università dell' Insubria; 22100 Como, Italy; Pettinari, Claudio [Scuola di Scienze del Farmaco e dei Prodotti della Salute; Università di Camerino; 62032 Camerino, Italy; Masciocchi, Norberto [Dipartimento di Scienza e Alta Tecnologia; Università dell' Insubria; 22100 Como, Italy; McDonald, Thomas M. [Department of Chemistry; University of California, Berkeley; , USA; Long, Jeffrey R. [Department of Chemistry; University of California, Berkeley; , USA; Materials Science Division; Lawrence Berkeley National Laboratory

    2015-01-01

    The synthesis, thermal behavior, crystal structure and adsorption properties of two novel MOFs isolated by coupling Ni(ii) and Cu(ii) to the extended tris(pyrazolate) strut 1,3,5-tris((1H-pyrazol-4-yl)phenyl)benzene are reported.

  7. Compensation strategy to reduce geometry and mechanics mismatches in porous biomaterials built with Selective Laser Melting.

    Science.gov (United States)

    Bagheri, Zahra S; Melancon, David; Liu, Lu; Johnston, R Burnett; Pasini, Damiano

    2017-06-01

    The accuracy of Additive Manufacturing processes in fabricating porous biomaterials is currently limited by their capacity to render pore morphology that precisely matches its design. In a porous biomaterial, a geometric mismatch can result in pore occlusion and strut thinning, drawbacks that can inherently compromise bone ingrowth and severely impact mechanical performance. This paper focuses on Selective Laser Melting of porous microarchitecture and proposes a compensation scheme that reduces the morphology mismatch between as-designed and as-manufactured geometry, in particular that of the pore. A spider web analog is introduced, built out of Ti-6Al-4V powder via SLM, and morphologically characterized. Results from error analysis of strut thickness are used to generate thickness compensation relations expressed as a function of the angle each strut formed with the build plane. The scheme is applied to fabricate a set of three-dimensional porous biomaterials, which are morphologically and mechanically characterized via micro Computed Tomography, mechanically tested and numerically analyzed. For strut thickness, the results show the largest mismatch (60% from the design) occurring for horizontal members, reduces to 3.1% upon application of the compensation. Similar improvement is observed also for the mechanical properties, a factor that further corroborates the merit of the design-oriented scheme here introduced. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Selective laser melting-produced porous titanium scaffolds regenerate bone in critical size cortical bone defects

    NARCIS (Netherlands)

    J. van der Stok (Johan); O.P. van der Jagt (Olav); S. Amin Yavari (Saber); M.F.P. de Haas (Mirthe); J.H. Waarsing (Jan); H. Jahr (Holger); E.M.M. van Lieshout (Esther); P. Patka (Peter); J.A.N. Verhaar (Jan); A.A. Zadpoor (Amir Abbas); H.H. Weinans (Harrie)

    2013-01-01

    textabstractPorous titanium scaffolds have good mechanical properties that make them an interesting bone substitute material for large bone defects. These scaffolds can be produced with selective laser melting, which has the advantage of tailoring the structure's architecture. Reducing the strut

  9. Elastic and failure response of imperfect three-dimensional metallic lattices: the role of geometric defects induced by Selective Laser Melting

    Science.gov (United States)

    Liu, Lu; Kamm, Paul; García-Moreno, Francisco; Banhart, John; Pasini, Damiano

    2017-10-01

    This paper examines three-dimensional metallic lattices with regular octet and rhombicuboctahedron units fabricated with geometric imperfections via Selective Laser Sintering. We use X-ray computed tomography to capture morphology, location, and distribution of process-induced defects with the aim of studying their role in the elastic response, damage initiation, and failure evolution under quasi-static compression. Testing results from in-situ compression tomography show that each lattice exhibits a distinct failure mechanism that is governed not only by cell topology but also by geometric defects induced by additive manufacturing. Extracted from X-ray tomography images, the statistical distributions of three sets of defects, namely strut waviness, strut thickness variation, and strut oversizing, are used to develop numerical models of statistically representative lattices with imperfect geometry. Elastic and failure responses are predicted within 10% agreement from the experimental data. In addition, a computational study is presented to shed light into the relationship between the amplitude of selected defects and the reduction of elastic properties compared to their nominal values. The evolution of failure mechanisms is also explained with respect to strut oversizing, a parameter that can critically cause failure mode transitions that are not visible in defect-free lattices.

  10. Strain-rate dependence for Ni/Al hybrid foams

    Directory of Open Access Journals (Sweden)

    Jung Anne

    2015-01-01

    Full Text Available Shock absorption often needs stiff but lightweight materials that exhibit a large kinetic energy absorption capability. Open-cell metal foams are artificial structures, which due to their plateau stress, including a strong hysteresis, can in principle absorb large amounts of energy. However, their plateau stress is too low for many applications. In this study, we use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nickel is deposited by electrodeposition as coating on the strut surface. The mechanical behaviour of cellular materials, including their behaviour under higher strain-rates, is governed by their microstructure due to the properties of the strut material, pore/strut geometry and mass distribution over the struts. Micro-inertia effects are strongly related to the microstructure. For a conclusive model, the exact real microstructure is needed. In this study a micro-focus computer tomography (μCT system has been used for the analysis of the microstructure of the foam samples and for the development of a microstructural Finite Element (micro-FE mesh. The microstructural FE models have been used to model the mechanical behaviour of the Ni/Al hybrid foams under dynamic loading conditions. The simulations are validated by quasi-static compression tests and dynamic split Hopkinson pressure bar tests.

  11. Pop / Lauri Tikerpe

    Index Scriptorium Estoniae

    Tikerpe, Lauri

    2006-01-01

    Heliplaatidest: Amp Fiddler "Afro Strut", Various "The World Is Gone", Guillemots "Through The Windowpane", Geltic Frost "Monotheist", Joan As Police Woman "Real Life", Slayer "Christ Illusion", Apocalyptica "Amplified//A Decade of Reinventing the Cello", Erinevad esitajad "Delicious Cafe Moskva - mixed by Dave Storm", Honey Power "Macrosilly"

  12. Pre-Stressing Timber-Based Plate Tensegrity Structures

    DEFF Research Database (Denmark)

    Falk, Andreas; Kirkegaard, Poul Henning

    2012-01-01

    paper considers the concept of plate tensegrity based on CLT plates (cross-laminated timber). It combines the principles of tensegrity with the principles of plate shells and is characterised by a plate shell stabilised by struts and cables. The paper deals with material aspects and robustness of timber...

  13. Assessment of nostril symmetry after primary cleft rhinoplasty in patients with complete unilateral cleft lip and palate

    NARCIS (Netherlands)

    Reddy, S.G.; Devarakonda, V.; Reddy, RR

    2013-01-01

    The aim of this study was to assess the nostril symmetry following primary cleft rhinoplasty done with either a dorsal onlay or columellar strut graft in patients with non-syndromic complete unilateral cleft lip and palate. In this retrospective study 30 consecutive patients treated with autogenous

  14. Spatial distribution and temporal evolution of scattering centers by optical coherence tomography in the poly(L-lactide) backbone of a bioresorbable vascular scaffold

    DEFF Research Database (Denmark)

    Gutiérrez-Chico, Juan Luis; Radu, Maria D; Diletti, Roberto

    2012-01-01

    Scattering centers (SC) are often observed with optical coherence tomography (OCT) in some struts of bioresorbable vascular scaffolds (BVS). These SC might be caused by crazes in the polymer during crimp-deployment (more frequent at inflection points) or by other processes, such as physiological...

  15. Microstructural characterization of in situ MXCT images of high density foams under large strains

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, Brian M [Los Alamos National Laboratory; Gleiman, Seth [Los Alamos National Laboratory; Marks, Trevor G [UCSB; Milstein, Fredrick [UCSB

    2009-01-01

    Foams are used in numerous applications, such as vibration damping and energy mitigation (e.g., packaging and helmets), wherein their mechanical properties are of critical importance. A typical compressive response of a high density elastomeric foam, shown in Fig 1, generally contains three regions of interest: (I) a linear-elastic region, governed by strut bending; (II) a relatively flat, or slowly increasing stress-strain response, accompanied by strut buckling and the localized collapse of pores; and (III) an exponentially increasing stress-strain curve wherein the collapse of the pore matrix leads to densification. Two material properties of interest, upon which considerable research has focused are the foam's Young's modulus, E{sub f}, defined as the slope of the stress-strain response in region I, and the collapse stress, {sigma}{sub f}, defined as the stress at which the response begins to deviate from linearity. It has been observed [1, 2, 3] that Young's modulus and the collapse stress are dependent on the material properties of the strut material and the non-dimensional relative-density of the foam, {rho}* = {rho}{sub f}/{rho}{sub m}, where {rho}{sub r} is the gross density of the foam and {rho}{sub m} is the density of the strut, or matrix, material. For foam of low relative-density, i.e, {rho}* < 0.1, the collapse stress and Young's modulus obey the relations {sigma}{sub c}/E{sub m} {proportional_to} ({rho}*){sup m} and E{sub f}/E{sub m} {proportional_to} ({rho}*){sup n} where E{sub m} is Young's modulus of the strut material and the bounds on the parameters m and n are 0.05 {le} m {le} 0.2 and 1 {le} n {le} 4 [4]. For open-celled foams, n = 2, whereas for closed-celled foams, n = 3. Theoretically, n = 1 for foams with an ''ideal strut'' configuration [6]. Foams of high relative-density ({rho}* > 0.1) require correcting terms to account for the axial contributions of the ''thick'' struts

  16. A Sub-Hertz, Low-Frequency Vibration Isolation Platform

    Science.gov (United States)

    Ortiz, Gerardo, G.; Farr, William H.; Sannibale, Virginio

    2011-01-01

    One of the major technical problems deep-space optical communication (DSOC) systems need to solve is the isolation of the optical terminal from vibrations produced by the spacecraft navigational control system and by the moving parts of onboard instruments. Even under these vibration perturbations, the DSOC transceivers (telescopes) need to be pointed l000 fs of times more accurately than an RF communication system (parabolic antennas). Mechanical resonators have been extensively used to provide vibration isolation for groundbased, airborne, and spaceborne payloads. The effectiveness of these isolation systems is determined mainly by the ability of designing a mechanical oscillator with the lowest possible resonant frequency. The Low-Frequency Vibration Isolation Platform (LFVIP), developed during this effort, aims to reduce the resonant frequency of the mechanical oscillators into the sub-Hertz region in order to maximize the passive isolation afforded by the 40 dB/decade roll-off response of the resonator. The LFVIP also provides tip/tilt functionality for acquisition and tracking of a beacon signal. An active control system is used for platform positioning and for dampening of the mechanical oscillator. The basic idea in the design of the isolation platform is to use a passive isolation strut with an approximately equal to 100-mHz resonance frequency. This will extend the isolation range to lower frequencies. The harmonic oscillator is a second-order lowpass filter for mechanical disturbances. The resonance quality depends on the dissipation mechanisms, which are mainly hysteretic because of the low resonant frequency and the absence of any viscous medium. The LFVIP system is configured using the well-established Stewart Platform, which consists of a top platform connected to a base with six extensible struts (see figure). The struts are attached to the base and to the platform via universal joints, which permit the extension and contraction of the struts. The

  17. Mechanical behaviour of nickel foams: three-dimensional morphology, non-linear models and fracture; Caracterisation et simulation numerique du comportement mecanique des mousses de nickel: morphologie tridimensionnelle, reponse elastoplastique et rupture

    Energy Technology Data Exchange (ETDEWEB)

    Dillard, Th.

    2004-03-15

    The deformation behaviour and failure of nickel foams were studied during loading by using X-ray microtomography. Strut alignment and stretching are observed in tension whereas strut bending followed by strut buckling are observed in compression. Strain localisation, that occurs during compression tests, depends on nickel weight distribution in the foam. Fracture in tension first takes place at cell nodes and the crack propagates cell by cell. The damaged area in front of a crack is about five cells wide. A detailed description of the three-dimensional morphology is also presented. One third of the cells are dodecahedral and 57 % of the faces are pentagonal. The most frequent cell is composed of two quadrilaterals, two hexagons and eight pentagons. The dimensions of the equivalent ellipsoid of each cell are identified and cell orientation are determined. The geometrical aspect ratio is linked to the mechanical anisotropy of the foam. In tension, a uniaxial analytical model, based on elastoplastic strut bending, is developed. The whole stress-strain curve of the foam is predicted according to its specific weight and its anisotropy. It is found that the non-linear regime of the macroscopic curve of the foam is not only due to the elastoplastic bending of the struts. The model is also extended to two-phase foams and the influence of the hollow struts is analysed. The two-phase foams model is finally applied to oxidized nickel foams and compared with experimental data. The strong increase in the rigidity of nickel foams with an increasing rate of oxidation, is well described by the model. However, a fracture criterion must also be introduced to take into account the oxide layer cracking. A phenomenological compressible continuum plasticity model is also proposed and identified in tension. The identification of the model is carried out using experimental strain maps obtained by a photo-mechanical technique. A validation of the model is provided by investigating the

  18. Time-related changes in neointimal tissue coverage of a novel Sirolimus eluting stent

    Energy Technology Data Exchange (ETDEWEB)

    Secco, Gioel Gabrio, E-mail: gioel.gabrio.secco@gmail.com [Interventional Cardiology, “Santi Antonio e Biagio e Cesare Arrigo” Hospital, Alessandria (Italy); NIHR Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London (United Kingdom); Mattesini, Alessio [NIHR Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London (United Kingdom); Fattori, Rossella; Parisi, Rosario [Interventional Cardiology, “San Salvatore” Hospital, Pesaro (Italy); Castriota, Fausto [GVM Care and Research, Cotignola (Italy); Vercellino, Matteo [Interventional Cardiology, “Santi Antonio e Biagio e Cesare Arrigo” Hospital, Alessandria (Italy); Dall’Ara, Gianni [NIHR Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London (United Kingdom); Uguccioni, Lucia; Marinucci, Lucia [Interventional Cardiology, “San Salvatore” Hospital, Pesaro (Italy); De Luca, Giuseppe; Marino, Paolo Nicola [University of Eastern Piedmont, Novara (Italy); Pistis, Gianfranco [Interventional Cardiology, “Santi Antonio e Biagio e Cesare Arrigo” Hospital, Alessandria (Italy); Di Mario, Carlo [NIHR Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust, London (United Kingdom)

    2016-01-15

    Background: DES has reduced rates of restenosis compared with BMS but it has been associated with delayed healing and increase of stent thrombosis. The aim of our study was to evaluate the vascular time-related changes following implantation of a new SES coated with an amorphous silicon carbide that allows faster re-endothelisation (Orsiro-Biotronik). Methods: This prospective registry enrolled STEMI-patients with multi-vessel disease, thus candidates for a two-step procedure. PCI of the culprit lesion was performed with at least one Orsiro stent that was OCT-analysed during the second-step procedure (deferred to 30,90 and 180-days). Results: 16 of the 95 patients with MVD underwent an OCT evaluation of the study device implanted in the culprit lesion during the second-step staged procedure and were enrolled in the present Registry. A total of 3060-struts were analysed. The percentage of uncovered struts was 19.6% at30-days, 1.3% at90-days and 1.8% at180-days (p < 0.001). The percentage of cross section with ≥ 1 uncovered struts were 51.3% at30-days, 6.5% at90-days and 5.7% at180-days (p < 0.001). The percentage of cross sections containing thrombus was 6.2% at30-days while no thrombus was detected both at90 and 180-days. Conclusions: Our data shows that the new Orsiro stent promotes early and persistent strut coverage with low peri-strut thrombus. This pilot OCT evaluation might suggest a low incidence of late adverse events and anticipate safe outcome after early withdrawal of dual antiplatelet therapy. - Highlights: • This is the first serial study comparing coverage at 1, 3, and 6-months in consecutive patients with STEMI; • Aim of our study was to evaluate the vascular time-related changes following implantation of a new SES coated with an amorphous silicon carbide that allows faster re-endothelisation (Orsiro-Biotronik); • The main finding of this pilot study is that the study device presented a fast pattern of intimal coverage, with a thin intimal

  19. A topological study of gravity free-surface waves generated by bluff bodies using the method of steepest descents

    Science.gov (United States)

    Trinh, Philippe H.

    2016-07-01

    The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel.

  20. Autonomous Observational Platforms for Ocean Studies: Operation, Advantages of Sensor Technology and Data Management

    Science.gov (United States)

    Atamanchuk, D.; Lai, J.; Vining, M.; Kehoe, D.; Siddall, G.; Send, U.; Wallace, D.

    2016-02-01

    Ocean Science and Technology research group (CERC.OCEAN) at Dalhousie University focuses on new approaches in design and development of autonomous platforms to study biogeochemical and ecological changes in the world's oceans. The principal research regions included the Labrador Sea, the Northwest Atlantic between Halifax and Bermuda, and the coastal areas of Atlantic Canada. The need for improved constraints on the ocean's present and future carbon cycle is of high relevance for the Northwest Atlantic, which is recognized as a largest sink of carbon dioxide(CO2) through air-sea exchange and subsequent transport to deeper layers of the global ocean. With the use of novel sensor technology integrated into the designed platforms we are achieving a superior spatial and temporal resolution of observations. SeaCycler - a surface piercing mooring - was designed to endure year-long measurements in harsh conditions of the open ocean, like Labrador Sea, while making daily profiles of the upper 150m of the water column. Significant research efforts within CERC.OCEAN are dedicated for improving sensors' data outcome. This includes testing, calibration of the sensors, QC and postprocessing to assure reliable and trustworthy measurements. Examples and implication of the data from SeaCycler, and other platforms including buoys, and automonous Volunteer Observing Ship (VOS) flow-through system will be presented.

  1. Prediction of regular wave loads on a fixed offshore oscillating water column-wave energy converter using CFD

    Directory of Open Access Journals (Sweden)

    Ahmed Elhanafi

    2016-12-01

    Full Text Available In this paper, hydrodynamic wave loads on an offshore stationary–floating oscillating water column (OWC are investigated via a 2D and 3D computational fluid dynamics (CFD modeling based on the RANS equations and the VOF surface capturing scheme. The CFD model is validated against previous experiments for nonlinear regular wave interactions with a surface-piercing stationary barge. Following the validation stage, the numerical model is modified to consider the pneumatic damping effect, and an extensive campaign of numerical tests is carried out to study the wave–OWC interactions for different wave periods, wave heights and pneumatic damping factors. It is found that the horizontal wave force is usually larger than the vertical one. Also, there a direct relationship between the pneumatic and hydrodynamic vertical forces with a maximum vertical force almost at the device natural frequency, whereas the pneumatic damping has a little effect on the horizontal force. Additionally, simulating the turbine damping with an orifice plate induces higher vertical loads than utilizing a slot opening. Furthermore, 3D modeling significantly escalates and declines the predicted hydrodynamic vertical and horizontal wave loads, respectively.

  2. The Interaction of a Turbulent Ship-Hull Boundary Layer and a Free Surface

    Science.gov (United States)

    Masnadi, N.; Washuta, N.; Wang, A.; Duncan, J. H.

    2013-11-01

    The free-surface deformation pattern caused by subsurface turbulent velocity fluctuations in the boundary layer at the mid-length of a naval ship is studied with a novel laboratory scale experimental technique. In this technique, the boundary layer is created in a large tank (13.4 m long, 1.3 m tall, and 2.4 m wide) with a surface-piercing meter-wide stainless steel belt that travels in a horizontal loop around two vertically oriented rollers whose axes are separated by 7.5 m. The device is enclosed in a dry box except for one of the two lengths between the rollers where a straight 6-meter-long section is exposed to the water and represents one side of the ship hull. The belt operates at full-scale ship speeds (up to 15 m/s) in order to match the Reynolds, Froude, and Weber numbers to those of naval ships, thus faithfully modeling the interaction of the turbulence with the free surface at laboratory scale. The water surface profile history midway between the rollers is recorded cinematically in a vertical plane normal to the belt using a Laser Induced Fluorescence (LIF) technique. This surface profile data is used to study the near-wall and far-field frequency content and propagation behavior of the surface ripples. The support of the Office of Naval Research is gratefully acknowledged.

  3. Surface Ripples Generated in a Couette Flow with a Free Surface

    Science.gov (United States)

    Masnadi, N.; Washuta, N.; Duncan, J. H.

    2014-11-01

    Free surface ripples created by subsurface turbulence in the gap between a vertical surface-piercing moving wall and a parallel fixed wall are studied experimentally. The moving wall is created with the aide of a meter-wide stainless steel belt that travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. One of the two 7.5-m-long belt sections between the rollers is in contact with the water in a large open-surface water tank and forms the moving wall. The fixed wall is an acrylic plate located 4 cm from the belt surface. The water surface ripples are measured in a plane normal to the belt using a cinematic LIF technique. Measurements are done at a location about 100 gap widths downstream of the leading edge of the fixed plate in order to have a fully developed flow condition. It is found that the overall RMS surface fluctuations increase linearly with belt speed. The frequency-domain spectra of the surface height fluctuation and its temporal derivative are computed at locations across the gap width and are used to explore the physics of the free surface motions. The support of the Office of Naval Research is gratefully acknowledged.

  4. Review of parameters influencing the structural response of a submerged body under cavitation conditions

    International Nuclear Information System (INIS)

    Escaler, X; De La Torre, O; Farhat, M

    2015-01-01

    Submerged structures that operate under extreme flows are prone to suffer large scale cavitation attached to their surfaces. Under such conditions the added mass effects differ from the expected ones in pure liquids. Moreover, the existence of small gaps between the structure and surrounding bodies filled with fluid also influence the dynamic response. A series of experiments and numerical simulations have been carried out with a truncated NACA0009 hydrofoil mounted as a cantilever beam at the LMH-EPFL cavitation tunnel. The three first modes of vibration have been determined and analysed under various hydrodynamic conditions ranging from air and still water to partial cavitation and supercavitation. A remote nonintrusive excitation system with piezoelectric patches has been used for the experiments. The effects of the cavity properties and the lateral gap size on the natural frequencies and mode shapes have been determined. As a result, the significance of several parameters in the design of such structures is discussed. (paper)

  5. First records of Gastrotricha from South Africa, with description of a new species of Halichaetonotus (Chaetonotida, Chaetonotidae

    Directory of Open Access Journals (Sweden)

    M. Todaro

    2011-10-01

    Full Text Available During a survey of the biota of the St. Lucia Estuary in the iSimangaliso Wetland Park, South Africa, a number of Gastrotricha were found among samples of meiofauna. Fresh, marine sediment yielded several specimens belonging to a total of seven species. Of these, two are already known from other regions (i.e., Dactylopodola australiensis and Heteroxenotrichula squamosa, one is described as new to science (Halichaetonotus sanctaeluciae sp. n., while the remaining four (Pseudostomella sp., Halichaetonotus sp.1, Halichaetonotus sp. 2, Xenotrichula sp. require further collections and analysis, in order to establish the extent of their affiliation to species already described. General appearance, shape of hydrofoil scale and the occurrence of three long spines on the dorsal side make the new species most closely related to H. australis and H. marivagus. The key differences from these taxa and between Halichaetonotus sanctaeluciae sp. n. and H. aculifer are discussed.

  6. Numerical simulation and experimental visualization of the separated cavitating boundary layer over NACA2412

    Directory of Open Access Journals (Sweden)

    Kozák Jiří

    2015-01-01

    Full Text Available Cavitation is physical phenomenon of crucial impact on the operation range and service lifetime of the hydraulic machines (pumps, turbines, valves etc.. Experimental measurement of cavitation is expensive and time consuming process, while some important characteristic of the flow are difficult to measure due to the nature of the phenomenon. Current possibilities of computational fluid dynamics provide a way for deeper understanding of cavitation which is important for many applications in the hydraulic machines industry such as expanding operation range or extending lifetime of the hydraulic machines. Simplified model consists of NACA 2412 hydrofoil with 8 degrees angle of attack fixed in between the walls of cavitation tunnel. Present investigation focuses on comparison of vapor volume fractions obtained by 3D CFD simulations and high speed visualization of the real cavitation phenomena. Several operating regimes corresponding to different cavitation numbers are studied with aim to assess the dynamics of the separated cavitating sheets/clouds

  7. STUDY UPON THE CAVITATION PHENOMENON OF THE ROTORS

    Directory of Open Access Journals (Sweden)

    Beazit ALI

    2011-11-01

    Full Text Available The main problem of the hydrodynamics of cavitation implosion of a single bubble, consists inpressure and velocity fields determination, including the collapse velocity of the bubble wall. By analysis thetheoretic and experimental phenomenon it establish the implicit function which describes this phenomenon. Byapplication the  theorem for this implicit function it finds the criterion equation of phenomenon.Depending on operating condition various cavitation patterns can be observed on a body surface astravelling bubbles, attached sheet cavitation, shear cavitation or vortex cavitation. Leading edge attachedpartialcavitation is commonly encountered on rotor blades or on hydrofoil. It corresponds to the case for whichavapor cavity is attached in the vecinity of the leading edge and extends over a fraction of the foil surface. Itgenerally takes places at incidence angles for which a leading edge pressure peak occurs and reduced belowtheliquid vapor pressure. At the early phases of development, leading edge partial cavitation is steady.

  8. Review of parameters influencing the structural response of a submerged body under cavitation conditions

    Science.gov (United States)

    Escaler, X.; De La Torre, O.; Farhat, M.

    2015-12-01

    Submerged structures that operate under extreme flows are prone to suffer large scale cavitation attached to their surfaces. Under such conditions the added mass effects differ from the expected ones in pure liquids. Moreover, the existence of small gaps between the structure and surrounding bodies filled with fluid also influence the dynamic response. A series of experiments and numerical simulations have been carried out with a truncated NACA0009 hydrofoil mounted as a cantilever beam at the LMH-EPFL cavitation tunnel. The three first modes of vibration have been determined and analysed under various hydrodynamic conditions ranging from air and still water to partial cavitation and supercavitation. A remote nonintrusive excitation system with piezoelectric patches has been used for the experiments. The effects of the cavity properties and the lateral gap size on the natural frequencies and mode shapes have been determined. As a result, the significance of several parameters in the design of such structures is discussed.

  9. High Performance Marine Vessels

    CERN Document Server

    Yun, Liang

    2012-01-01

    High Performance Marine Vessels (HPMVs) range from the Fast Ferries to the latest high speed Navy Craft, including competition power boats and hydroplanes, hydrofoils, hovercraft, catamarans and other multi-hull craft. High Performance Marine Vessels covers the main concepts of HPMVs and discusses historical background, design features, services that have been successful and not so successful, and some sample data of the range of HPMVs to date. Included is a comparison of all HPMVs craft and the differences between them and descriptions of performance (hydrodynamics and aerodynamics). Readers will find a comprehensive overview of the design, development and building of HPMVs. In summary, this book: Focuses on technology at the aero-marine interface Covers the full range of high performance marine vessel concepts Explains the historical development of various HPMVs Discusses ferries, racing and pleasure craft, as well as utility and military missions High Performance Marine Vessels is an ideal book for student...

  10. The hovercraft environment.

    Science.gov (United States)

    Lovesey, E J

    1970-06-01

    In just over a decade the hovercraft has progressed from first prototype to a successful commercial form of transport which also has the ability to penetrate many environments hitherto virtually inaccessible to manned vehicles. Comparison with rival short range vehicles such as the helicopter and hydrofoil show that the hovercraft has become one of the most versatile forms of transport available. This versatility and ability to operate in unusual or extreme environments has been accompanied by the problems of control and of protection of the occupants of the hovercraft from the hazards associated with these environments. Several of these problems are discussed, together with their possible solutions. This article is based on a paper given to the Nederlands Vereniging Voor Ergonomie/Ergonomics Research Society joint conference at Noordwijk in Holland, 11-13 June, 1969.

  11. Control of Oscillating Foil for Propulsion of Biorobotic Autonomous Underwater Vehicle (AUV

    Directory of Open Access Journals (Sweden)

    S. N. Singh

    2005-01-01

    Full Text Available The paper treats the question of control of a laterally and rotationally oscillating hydrofoil for the propulsion of biologically inspired robotic (biorobotic autonomous underwater vehicles (BAUVs. Sinusoidal oscillations of foils produce maneuvering and propulsive forces. The design is based on the internal model principle. Two springs are used to transmit forces from the actuators to the foil. Oscillating fins produce periodic forces, which can be used for fish-like propulsion and control of autonomous underwater vehicles (AUVs. The equations of motion of the foil include hydrodynamic lift and moment based on linear, unsteady, aerodynamic theory. A control law is derived for the lateral and rotational sinusoidal oscillation of the foil. In the closed-loop system, the lateral displacement and the rotational angle of the foil asymptotically follow sinusoidal trajectories of distinct frequencies and amplitudes independently. Simulation results are presented to show the trajectory tracking performance of the foil for different freestream velocities and sinusoidal command trajectories.

  12. Potential applications for Flettner rotors and Turbosails in tidal stream turbines

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    Oreada reports on its studies of two novel lifting devices, namely Flettner Rotors and Turbosails, for application in powering tidal stream generators. Through computer modelling, the power generated by the lift devices has been compared with that of a conventional hydrofoil. The mathematical model assumes the base-case configuration for the turbine to be four parallel lift devices at a constant radius from the centre of the turbine and simulates a vertical axis turbine. Adjacent lift devices subtend an angle of ninety degrees at the centre of the turbine. The theoretical study indicated that the planned second part of the project involving bench tests should not go ahead. The study was largely funded by the DTI.

  13. Submerged electricity generation plane with marine current-driven motors

    Science.gov (United States)

    Dehlsen, James G.P.; Dehlsen, James B.; Fleming, Alexander

    2014-07-01

    An underwater apparatus for generating electric power from ocean currents and deep water tides. A submersible platform including two or more power pods, each having a rotor with fixed-pitch blades, with drivetrains housed in pressure vessels that are connected by a transverse structure providing buoyancy, which can be a wing depressor, hydrofoil, truss, or faired tube. The platform is connected to anchors on the seafloor by forward mooring lines and a vertical mooring line that restricts the depth of the device in the water column. The platform operates using passive, rather than active, depth control. The wing depressor, along with rotor drag loads, ensures the platform seeks the desired operational current velocity. The rotors are directly coupled to a hydraulic pump that drives at least one constant-speed hydraulic-motor generator set and enables hydraulic braking. A fluidic bearing decouples non-torque rotor loads to the main shaft driving the hydraulic pumps.

  14. Knowledge of damage identification about tensegrities via flexibility disassembly

    Science.gov (United States)

    Jiang, Ge; Feng, Xiaodong; Du, Shigui

    2017-12-01

    Tensegrity structures composing of continuous cables and discrete struts are under tension and compression, respectively. In order to determine the damage extents of tensegrity structures, a new method for tensegrity structural damage identification is presented based on flexibility disassembly. To decompose a tensegrity structural flexibility matrix into the matrix represention of the connectivity between degress-of-freedoms and the diagonal matrix comprising of magnitude informations. Step 1: Calculate perturbation flexibility; Step 2: Compute the flexibility connectivity matrix and perturbation flexibility parameters; Step 3: Calculate the perturbation stiffness parameters. The efficiency of the proposed method is demonstrated by a numeical example comprising of 12 cables and 4 struts with pretensioned. Accurate identification of local damage depends on the availability of good measured data, an accurate and reasonable algorithm.

  15. A comparative study of behaviors of ventilated supercavities between experimental models with different mounting configurations

    International Nuclear Information System (INIS)

    Lee, Seung-Jae; Karn, Ashish; Arndt, Roger E A; Kawakami, Ellison

    2016-01-01

    Small-scale water tunnel experiments of the phenomenon of supercavitation can be carried out broadly using two different kinds of experimental models–in the first model (forward facing model, or FFM), the incoming flow first interacts with the cavitator at front, which is connected to the strut through a ventilation pipe. The second model could have the strut and the ventilation pipe preceding the cavitator (backward facing model, or BFM). This is the continuation of a water tunnel study of the effects of unsteady flows on axisymmetric supercavities. In this study, the unwanted effect of test model configuration on supercavity shape in periodic flows was explored through a comparison of FFM and BFM models. In our experiments, it was found that periodic gust flows have only a minimal effect on the maximum diameter and the cavity length can be shortened above a certain vertical velocity of periodic flows. These findings appear to be robust regardless of the model configuration. (paper)

  16. Ultra-light hierarchical meta-materials on a body-centred cubic lattice

    Science.gov (United States)

    Rayneau-Kirkhope, Daniel; Mao, Yong; Farr, Robert

    2017-07-01

    Modern fabrication techniques offer the freedom to design and manufacture structures with complex geometry on many lengthscales, offering many potential advantages. For example, fractal/hierarchical struts have been shown to be exceptionally strong and yet light (Rayneau-Kirkhope D. et al., Phys. Rev. Lett., 109 (2012) 204301). In this letter, we propose a new class of meta-material, constructed from fractal or hierarchical struts linking a specific set of lattice points. We present a mechanical analysis of this meta-material resulting from a body-centred cubic (BCC) lattice. We show that, through the use of hierarchy, the material usage follows an enhanced scaling relation, and both material property and overall efficiency can be optimised for a specific applied stress. Such a design has the potential of providing the next generation of lightweight, buckling-resistant meta-materials.

  17. Flow disturbances in stent-related coronary evaginations

    DEFF Research Database (Denmark)

    Radu, Maria D; Pfenniger, Aloïs; Räber, Lorenz

    2014-01-01

    Aims: Angiographic ectasias and aneurysms in stented segments have been associated with late stent thrombosis. Using optical coherence tomography (OCT), some stented segments show coronary evaginations reminiscent of ectasias. The purpose of this study was to explore, using computational fluid......-dynamic (CFD) simulations, whether OCT-detected coronary evaginations can induce local changes in blood flow. Methods and results: OCT-detected evaginations are defined as outward bulges in the luminal vessel contour between struts, with the depth of the bulge exceeding the actual strut thickness. Evaginations...... can be characterised cross ectionally by depth and along the stented segment by total length. Assuming an ellipsoid shape, we modelled 3-D evaginations with different sizes by varying the depth from 0.2-1.0 mm, and the length from 1-9 mm. For the flow simulation we used average flow velocity data from...

  18. Gas Raman sensing with multi-opened-up suspended core fiber.

    Science.gov (United States)

    Wang, Guanjun; Liu, Jiansheng; Yang, Yi; Zheng, Zheng; Xiao, Jing; Li, Ruichao

    2011-11-01

    Gas sensing and fluid-guiding response properties of a suspended core fiber Raman analyzer with side-opened and strut microfluid-guiding array are explored. A Raman sensing model is introduced for effective mode area optimization and normalized intensity overlap enhancement between Raman sensing light and analyte. Calculations predict that there is a trade-off between the overlap and the effective mode area, while the optimal trade-off depends on the refractive index of the background material, core diameter, and strut's thickness. Furthermore, the multi-opened-up structure ensures a fast gases diffusing into/out of each hole for real-time Raman sensing. Simulation results confirm a limited gas sensing response time of less than 6 s could be feasible and, thus, a new approach to real-time gas sensing applications is identified. © 2011 Optical Society of America

  19. Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics

    Science.gov (United States)

    Bushnell, Dennis M.

    2000-01-01

    This paper discusses Advanced Aircraft configurational approaches across the speed range, which are either enabled, or greatly enhanced, by clever Flow Control. Configurations considered include Channel Wings with circulation control for VTOL (but non-hovering) operation with high cruise speed, strut-braced CTOL transports with wingtip engines and extensive ('natural') laminar flow control, a midwing double fuselage CTOL approach utilizing several synergistic methods for drag-due-to-lift reduction, a supersonic strut-braced configuration with order of twice the L/D of current approaches and a very advanced, highly engine flow-path-integrated hypersonic cruise machine. This paper indicates both the promise of synergistic flow control approaches as enablers for 'Revolutions' in aircraft performance and fluid mechanic 'areas of ignorance' which impede their realization and provide 'target-rich' opportunities for Fluids Research.

  20. Analytical simulation of seismic testing of VKL piping system at the HDR test facility

    International Nuclear Information System (INIS)

    Srinivasan, M.G.; Kot, C.A.; Hsieh, B.J.

    1990-01-01

    The paper describes the analytical modeling, calculations, and results of the posttest simulation of seismic testing of the VKL piping system at the HDR Test Facility in West Germany. A main objective of the tests was to evaluate analytical methods for calculating the seismic response of realistic piping systems subjected to seismic excitation. Six different pipe-support configurations, ranging from a stiff system with struts and snubbers to a very flexible system with practically no seismic supports, were subjected to simulated earthquakes. The posttest calculations cover the stiffest system with snubbers, and a reasonably compliant system with only rigid struts. Responses for 100 to 300% safe-shutdown-earthquake loading were calculated using the piping response module of the SMACS code with multiple, independent support acceleration input. Analytical simulation of the tests was found to somewhat underestimate the responses. The paper discusses the possible explanation for this and the effect on the results of the damping ratios assumed

  1. Solar wind rare gas analysis: Trapped solar wind helium and neon in Surveyor 3 material

    Science.gov (United States)

    Buehler, F.; Eberhardt, P.; Geiss, J.; Schwarzmueller, J.

    1972-01-01

    The He-4 and Ne-20 contents in sections of the Surveyor 3 support strut samples were determined by optical and scanning electron microscopy and are compared to the results of the Apollo solar wind composition (SWC) experiments. The He-4/Ne-20 ratio in the samples from the sunlit side of the strut was approximately 300; the ratios determined in Apollo 12 lunar fines and SWC foil were below 100. The He-4/He-3 ratios were also determined, and the ratio obtained from Surveyor 3 material is higher than those found with Apollo 11 and 12 SWC experiments. The effects of spallation by cosmic rays or solar protons, stripping by cosmic ray or energetic solar alpha particles, recycling of solar wind He and radiogenic Ne, He from terrestrial atmosphere, mass discrimination near the moon, mass dependence of trapping probability, diffusion, and contamination by lunar dust are considered.

  2. A Class of Generalized Gough-Stewart Platforms Used for Effectively Obtaining Dynamic Isotropy – An Analytical Study

    Directory of Open Access Journals (Sweden)

    Afzali-Far Behrouz

    2015-01-01

    Full Text Available In this paper, we propose a class of Generalized Gough-Stewart Platforms (GGSPs used, as a novel approach, to eliminate the classical isotropic constraint of GSPs (hexapods. GGSPs are based on the standard GSP architecture with additional rotations of the three strut-pairs. Despite the architectural generalization introduced in GGSPs, they do not require much more effort in order to be fabricated. This is due to the fact that all the struts (actuators can be chosen identical, similar to standard GSPs. We analytically show how effectively the classical isotropic constraint is removed and that still sufficient simplicity is retained. Furthermore, this paper gives an intuitive understanding of dynamic isotropy in GGSPs as well as GSPs.

  3. The 3D structure of real polymer foams.

    Science.gov (United States)

    Montminy, Matthew D; Tannenbaum, Allen R; Macosko, Christopher W

    2004-12-01

    The intricate structure of polymeric foams may be examined using 3D imaging techniques such as MRI or X-ray tomography followed by image processing. Using a new 3D image processing technique, six images of polyurethane foams were analyzed to create computerized 3D models of the samples. Measurements on these models yielded distributions of many microstructural features, including strut length and window and cell shape distributions. Nearly 8000 struts, 4000 windows, and 376 cells were detected and measured in six polyurethane foam samples. When compared against previous theories and studies, these measurements showed that the structure of real polymeric foams differs significantly from both equilibrium models and aqueous foams. For example, previous studies of aqueous foams showed that about 70% of foam windows were pentagons. In the polymeric sample studied here, only 55% of windows were pentagonal.

  4. Characterization of porous materials using combined small-angle X-ray and neutron scattering techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Naiping; Borkar, Neha; Kohls, Doug; Schaefer, Dale W. (UCIN)

    2014-09-24

    A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize porous materials. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 {mu}m was used as a model to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.

  5. Characterization of porous materials using combined small-angle X-ray and neutron scattering techniques

    International Nuclear Information System (INIS)

    Hu, Naiping; Borkar, Neha; Kohls, Doug; Schaefer, Dale W.

    2012-01-01

    A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize porous materials. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 μm was used as a model to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.

  6. Motion Planning of Kinematically Redundant 12-tetrahedral Rolling Robot

    Directory of Open Access Journals (Sweden)

    Xingbo Wang

    2016-02-01

    Full Text Available The 12-tetrahedral robot is an addressable reconfigurable technology (ART-based variable geometry truss mechanism with 26 extensible struts and nine nodes arranged in a tetrahedral mesh. The robot has the capability of configuring its shape to adapt to environmental requirements, which makes it suitable for space exploration. This paper considers the motion planning problem for the robot in terms of gait planning and trajectory planning. First, a gait planning method is developed that limits the forward falling angles to only 25 degrees. Then, according to the given gait, the jerk-bounded method and inverse kinematics are utilized to calculate the trajectories of the nodes and the struts, respectively. A robot system model was built in ADAMS and simulations were conducted to demonstrate the feasibility of the motion planning method.

  7. Inhomogeneity of deformed state during compression testing of titanium implant

    Directory of Open Access Journals (Sweden)

    Loginov Yury

    2017-01-01

    Full Text Available This study examines the inhomogeneity of deformed state during compression testing of porous titanium implant. The theoretical part of the article includes numerical simulation of deformation of a prismatic titanium sample compressed with absolutely rigid plates. The porosity was provided by the circular shape pores with titanium struts between them. To solve the problem by means of the finite element analysis, the boundary conditions were set using the ABAQUS software. The fields of strain, stresses and displacements were determined. Presumable place of fracture coincide with the highest values of strain which are localized in vertical struts. Physical modeling of the implant compression was performed at the second part of the study on the testing machine with video recording. It was shown that in the real process the localization of failure corresponds to the calculated data.

  8. Analysis of the Scramjet inlet flow field using two-dimensional Navier-Stokes equations

    Science.gov (United States)

    Kumar, A.; Tiwari, S. N.

    1982-01-01

    A computer code was developed to solve the full two dimensional Navier-Stokes equations in a scramjet inlet. The analysis uses a numerical coordinate transformation which generates a set of boundary-fitted curvilinear coordinates. The explicit finite difference algorithm of MacCormack is used to solve the governing equations. A two-layer eddy viscosity model is used for the turbulent flow. The code can analyze both inviscid and viscous flows with multiple struts in the flow field. Detailed results are presented for two model problems and two scramjet inlets with one and two struts. The application of the two dimensional analysis in the preliminary design of the actual scramjet inlet is briefly discussed.

  9. A fresh look at bioresorbable scaffold technology: Intuition pumps

    Directory of Open Access Journals (Sweden)

    Sundeep Mishra

    2017-01-01

    Full Text Available Bioresorbable scaffolds (BRS are a new enticing treatment option in coronary interventions. Absorb BVS™ Is the most widely used and researched polymer based BRS, eluting everolimus. However currently it has several technical limitations; low radial support, larger strut size, poor visualization, poor deliverability and complex implantation technique. Magnesium based BRS are an alternate but they are also limited not only by lower radial support and poor visualization but also earlier bio-absorption. Material processing: blow-molding, annealing, polymer orientation, change in composition and use of higher molecular weight polymer, as well new polymers like tyrosine or salicyclate analogs and even hybrid (polymer and metallic combined with intelligent cell design has led to evolution of BRS technology. Newer BRS has higher radial strength, lower strut thickness, improved visualization, ease of scaffold implantation as also optimal bio-resorption time.

  10. Extremal limits of the C metric: Nariai, Bertotti-Robinson, and anti-Nariai C metrics

    International Nuclear Information System (INIS)

    Dias, Oscar J.C.; Lemos, Jose P.S.

    2003-01-01

    In two previous papers we have analyzed the C metric in a background with a cosmological constant Λ, namely, the de-Sitter (dS) C metric (Λ>0), and the anti-de Sitter (AdS) C metric (Λ 0, Λ=0, and Λ 2 xS-tilde 2 ) to each point in the deformed two-sphere S-tilde 2 corresponds a dS 2 spacetime, except for one point which corresponds to a dS 2 spacetime with an infinite straight strut or string. There are other important new features that appear. One expects that the solutions found in this paper are unstable and decay into a slightly nonextreme black hole pair accelerated by a strut or by strings. Moreover, the Euclidean version of these solutions mediate the quantum process of black hole pair creation that accompanies the decay of the dS and AdS spaces

  11. Performance variation due to stiffness in a tuna-inspired flexible foil model.

    Science.gov (United States)

    Rosic, Mariel-Luisa N; Thornycroft, Patrick J M; Feilich, Kara L; Lucas, Kelsey N; Lauder, George V

    2017-01-17

    Tuna are fast, economical swimmers in part due to their stiff, high aspect ratio caudal fins and streamlined bodies. Previous studies using passive caudal fin models have suggested that while high aspect ratio tail shapes such as a tuna's generally perform well, tail performance cannot be determined from shape alone. In this study, we analyzed the swimming performance of tuna-tail-shaped hydrofoils of a wide range of stiffnesses, heave amplitudes, and frequencies to determine how stiffness and kinematics affect multiple swimming performance parameters for a single foil shape. We then compared the foil models' kinematics with published data from a live swimming tuna to determine how well the hydrofoil models could mimic fish kinematics. Foil kinematics over a wide range of motion programs generally showed a minimum lateral displacement at the narrowest part of the foil, and, immediately anterior to that, a local area of large lateral body displacement. These two kinematic patterns may enhance thrust in foils of intermediate stiffness. Stiffness and kinematics exhibited subtle interacting effects on hydrodynamic efficiency, with no one stiffness maximizing both thrust and efficiency. Foils of intermediate stiffnesses typically had the greatest coefficients of thrust at the highest heave amplitudes and frequencies. The comparison of foil kinematics with tuna kinematics showed that tuna motion is better approximated by a zero angle of attack foil motion program than by programs that do not incorporate pitch. These results indicate that open questions in biomechanics may be well served by foil models, given appropriate choice of model characteristics and control programs. Accurate replication of biological movements will require refinement of motion control programs and physical models, including the creation of models of variable stiffness.

  12. The functional anatomy of forearm rotation

    OpenAIRE

    Lees, Vivien C.

    2009-01-01

    The elbow, forearm and wrist act as a unified structure to provide a stable, strong and highly mobile strut for positioning the hand in space and for conducting load-bearing tasks. An understanding of the relevant anatomy and biomechanics is important for the surgeon assessing and treating disorders of forearm function. This paper is concerned with illuminating the principles and concepts governing forearm rotation and load-bearing functions.

  13. Une structure active de type tensegrité

    OpenAIRE

    Fest, Etienne; Smith, Ian

    2005-01-01

    A tensegrity is a lightweight space reticulated structure consisting of compression members — struts — surrounded by a network of tension members — cables — that provide rigidity and stability. They can be easily dismantled and therefore, they provide innovative possibilities for reusable and modular structures. To date, tensegrity construction has been limited to sculptures. The number of full-scale prototypes built is increasing though few have been tested experimentally statically. Tensegr...

  14. Reversed single string technique for coronary bifurcation stenting-First report of case demonstrations in vitro.

    Science.gov (United States)

    Adjedj, Julien; Toth, Gabor G; Pellicano, Mariano; Wijns, William

    2018-02-15

    This work reports the concept and the practical feasibility of Reversed Single String bifurcation stenting technique by demonstrating three in vitro cases. Provisional T stenting is the most used interventional technique to treat coronary bifurcation lesions. However, after main branch (MB) stenting, treatment of the side branch (SB) may become indicated to provide a good final result. Currently applied methods all have their structural limitations with respect to wall coverage, multiple strut layers, poor apposition rate. We reasoned that reversing the Single String technique principle could be used as a bail out after inadequate provisional T stenting. We simulated in three silicone bifurcation phantoms a scenario whereby stenting the SB becomes indicated after provisional T stenting. Thereafter, as first step of Reversed Single String, a stent was deployed into the SB ostium with one single protruding stent-cell into the MB. After wiring that stent-cell and positioning MB balloon across it, final kissing balloon dilation was performed. Results of the in vitro Reversed Single String cases were evaluated by X-ray angiography, optical frequency domain imaging, and 3-Dimensional (3D) reconstruction (OFDI). Each case was successfully performed and completed. In the bifurcation area, perfect apposition was documented in over 81% of the struts. Malapposition remained below 4% of struts in each case. 3D OFDI reconstruction did not reveal any strut fracture. This report suggests that Reversed Single String technique might offer a potential bail out solution for provisional T-stenting cases, when treatment of the SB becomes indicated. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Sandwich allografts for long-bone nonunions in patients with osteogenesis imperfecta: a retrospective study.

    Science.gov (United States)

    Puvanesarajah, Varun; Shapiro, Jay R; Sponseller, Paul D

    2015-02-18

    Patients with osteogenesis imperfecta often develop nonunions, as internal fixation has limited applicability in this condition. We report the outcomes of a modified "sandwich technique" in the treatment of long-bone nonunions in patients with osteogenesis imperfecta; this technique brings circumferential stabilization and normal collagen to the nonunion site. From May 2003 through February 2012, twelve patients (eight females, four males; median age, 39.0 years; range, eleven to seventy-eight years) who had osteogenesis imperfecta (Sillence type I [three], type III [eight], and type IV [one]) and a combined total of thirteen nonunions (two humeral, two radial, three femoral, four tibial, and two ulnar; median duration, 15.0 months; range, six to 204 months) were treated at our institution with compressed sandwich allograft cortical struts. The struts were fashioned to be wide enough to allow for increased osteoconductive surface area and to approximate a hemicylindrical shape. Treatment history and demographics data were acquired through retrospective chart review. Follow-up radiographs were analyzed by two attending orthopaedic surgeons to determine radiographic findings. The median follow-up time was 4.6 years (range, 2.1 to 10.3 years). All thirteen nonunions, including one requiring a second graft procedure, healed with abundant, smooth allograft incorporation, resulting in an initial healing rate of 92% because of a refracture in one patient. This patient's nonunion ultimately healed with additional allograft struts and a new intramedullary rod. One patient required removal of prominent screws. The final follow-up examinations revealed no pain or refracture at the original nonunion site. All patients regained their prefracture level of function. Sandwich allograft struts constitute a durable, safe method for the stabilization and healing of persistent long-bone nonunions in patients with osteogenesis imperfecta. All patients showed incorporation of the

  16. Position Analysis of Planar Tensegrity Structures

    Science.gov (United States)

    2006-08-01

    and 2 non-compliant members. Finding a simple solution approach for a closed form solution to the other two dimensional tensegrity structures...dimensional tensegrity structures, struts still do not touch. A tensegrity structure stands by itself in its equilibrium position and maintains its form ...equilibrium position when no external force or torque is applied. A closed- form solution of a two-spring, three-spring, and four- spring planar tensegrity

  17. Sensor to detect endothelialization on an active coronary stent

    Directory of Open Access Journals (Sweden)

    Coffey Arthur C

    2010-11-01

    Full Text Available Abstract Background A serious complication with drug-eluting coronary stents is late thrombosis, caused by exposed stent struts not covered by endothelial cells in the healing process. Real-time detection of this healing process could guide physicians for more individualized anti-platelet therapy. Here we present work towards developing a sensor to detect this healing process. Sensors on several stent struts could give information about the heterogeneity of healing across the stent. Methods A piezoelectric microcantilever was insulated with parylene and demonstrated as an endothelialization detector for incorporation within an active coronary stent. After initial characterization, endothelial cells were plated onto the cantilever surface. After they attached to the surface, they caused an increase in mass, and thus a decrease in the resonant frequencies of the cantilever. This shift was then detected electrically with an LCR meter. The self-sensing, self-actuating cantilever does not require an external, optical detection system, thus allowing for implanted applications. Results A cell density of 1300 cells/mm2 on the cantilever surface is detected. Conclusions We have developed a self-actuating, self-sensing device for detecting the presence of endothelial cells on a surface. The device is biocompatible and functions reliably in ionic liquids, making it appropriate for implantable applications. This sensor can be placed along the struts of a coronary stent to detect when the struts have been covered with a layer of endothelial cells and are no longer available surfaces for clot formation. Anti-platelet therapy can be adjusted in real-time with respect to a patient's level of healing and hemorrhaging risks.

  18. Correction of the retracted alar base.

    Science.gov (United States)

    Losquadro, William D; Bared, Anthony; Toriumi, Dean M

    2012-04-01

    Alar base retraction is a common yet difficult problem faced by the rhinoplasty surgeon. It may be caused by weakened, overresected lateral crura, vestibular lining deficiencies, or congenital alar malpositioning. Methods of correction include soft tissue manipulation, auricular composite grafting, and cartilage grafting. We present the senior author's graded approach to alar retraction using auricular composite grafting, alar rim grafting, and lateral crural strut graft placement with caudal lateral crural repositioning. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  19. [Reconstruction of periprosthetic fractures of hip with cortical bone plates allografts].

    Science.gov (United States)

    Zhou, Zong-ke; Pei, Fu-xing; Tu, Chong-qi; Yang, Jing; Shen, Bin; Liu, Lei; Fatou, Camara-yagouba

    2004-12-22

    To observe clinical results for reconstruction of periprosthetic fractures of hip with cortical bone plates allografts by deep-freezing and ethylene oxide treatment. Seven patients with periprosthetic fractures of hip underwent cortical bone plates allografts by deep-freezing at -70 degrees C after being treatment of 48 degrees C ethylene oxide. And evaluate clinical outcome by examining T lymphocytes, Harris scores, X-rays photograph, and bone scintigraphy. There were not activity of immune rejection and infection in all patients. Harris scores of patients increased 21, 32, 40, 40 scores at 3, 6, 12, 24 months after surgery. T-lymphocytes, antibody and immunocomplex in blood was normal postoperation. X-ray film indicated that fracture was healed at 3 months and there was partially bone conjunction between allograft strut and host bone. There was incorporation of 85% allograft strut to host bone, and 15% allograft strut was partially absorbed at 12 months after surgery. The size of femur of host was added 3 mm to 5 mm, averaged 4.3 mm at 12 months postoperation. Density of 80% allograft plates was as same as host bone after remodeling and the absorbtion of 10% allograft plates stopped at 24 months after surgery. There was thick of nuclein in the area of allograft cortical bone plates by bone scintigraphy examination at 3 months postoperation, and the thick of nuclein was stronger at 6, and 12 months after surgery. Allograft cortical bone plates by deep frozen at -70 degrees C after being treatment of 48 degrees C ethylene oxide is suitable for mechanical fixation and biological bone transplantation, and it can increase bone reservation, augment strength of femur once the allograft strut incorporates to host bone, and avoid removing metal implant in second operation when being applied into reconstruction femoral fracture in joint replacement.

  20. On the physical parametrization and magnetic analogs of the Emparan-Teo dihole solution

    Energy Technology Data Exchange (ETDEWEB)

    Cazares, J.A. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, CP 07000, Mexico D.F. (Mexico); Garcia-Compean, H. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, CP 07000, Mexico D.F. (Mexico); CINVESTAV-IPN, Unidad Monterrey, Via del Conocimiento 201, Parque de Investigacion e Innovacion Tecnologica (PIIT), Autopista nueva al Aeropuerto Km. 9.5, Lote 1, manzana 29, CP 66600, Apodaca, Nuevo Leon (Mexico); Manko, V.S. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, CP 07000, Mexico D.F. (Mexico)], E-mail: vsmanko@fis.cinvestav.mx

    2008-04-17

    The Emparan-Teo non-extremal black dihole solution is reparametrized using Komar quantities and the separation distance as arbitrary parameters. We show how the potential A{sub 3} can be calculated for the magnetic analogs of this solution in the Einstein-Maxwell and Einstein-Maxwell-dilaton theories. We also demonstrate that, similar to the extreme case, the external magnetic field can remove the supporting strut in the non-extremal black dihole too.

  1. U. S. Naval Forces, Vietnam Monthly Historical Summary for December 1970

    Science.gov (United States)

    1971-02-15

    such as engine overhauls, bar armour repair, hull welding, and strut and rudder repair. In that day’s situation summary, he reported that only nine...with emphasis on bars and restaurant frequented by friendly forces. Further reports have indicated that high sapper activity will accompany mortar...8217 -Honorable Carlos G,~ Camanchoj Governor of Gu-Am; Rear Admiral F. L. Garrett, USN, Chief .of Chaplains, lviartha Raye , Colonel, USAR (Cam Ranh Bay

  2. Side branch healing patterns of the Tryton dedicated bifurcation stent: a 1-year optical coherence tomography follow-up study.

    Science.gov (United States)

    Grundeken, Maik J; Garcia-Garcia, Hector M; Kraak, Robin P; Woudstra, P; de Bruin, Daniel M; van Leeuwen, Ton G; Koch, Karel T; Tijssen, Jan G; de Winter, Robbert J; Wykrzykowska, Joanna J

    2014-12-01

    The bare-metal Tryton Side Branch (SB) Stent™ (Tryton Medical, Durham, NC, USA) is used with a drug-eluting stent (DES) in the main branch (MB) to treat bifurcation lesions. It is argued that a drug-eluting Tryton-version is needed to improve clinical outcomes, although previous registries have shown good clinical results. More insights in neo-intimal hyperplasia (NIH) growth patterns of the Tryton treatment strategy are needed to decide if and where to drug-coat the stent. Ten patients returned for follow-up angiography (mean follow-up time 393 ± 103 days) and optical coherence tomography (OCT) pullbacks from the MB were obtained in all patients and from the SB in six patients. A per-strut analysis showed an uncovered strut rate of 0.7 % and an incompletely-apposed strut rate of 0.8 %. Most incompletely-apposed struts were found at the bifurcation region, in the luminal half facing towards the SB. Mean NIH thickness in the proximal MB, distal MB and SB were 0.14 ± 0.11, 0.19 ± 0.11, and 0.34 ± 0.19 mm, respectively, with a variety of growth patterns observed in the SB. We found good vascular healing of the DES in the MB, while healing was less favourably in the SB part. Furthermore, we observed a variety of NIH growth patterns in this SB part and more studies are needed to investigate the relation between growth patterns and clinical outcomes.

  3. Comparison of early-phase arterial repair following cobalt-chrome everolimus-eluting stent and slow-release zotarolimus-eluting stent: an angioscopic study.

    Science.gov (United States)

    Ishihara, Takayuki; Iida, Osamu; Fujita, Masashi; Masuda, Masaharu; Okamoto, Shin; Nanto, Kiyonori; Kanda, Takashi; Tsujimura, Takuya; Sunaga, Akihiro; Awata, Masaki; Nanto, Shinsuke; Uematsu, Masaaki

    2018-04-01

    Whether arterial repair following implantation of drug-eluting stents (DES) of the second generation differs among stent types remains unknown. We examined 41 DES placed in 28 patients (age 72 ± 7 years, male 89%) presenting with stable angina pectoris due to de novo lesions in native coronary arteries. Coronary angioscopy was performed 4 ± 1 months after stent implantation. Patients were divided into two groups based on the DES types: 22 cobalt-chrome everolimus-eluting stents (CoCr-EES) in 13 patients and 19 slow-release zotarolimus-eluting stents (R-ZES) in 15 patients. Neointimal coverage (NIC) was graded as: grade 0, stent struts exposed; grade 1, struts bulging into the lumen, although covered; grade 2, struts embedded in the neointima, but translucent; grade 3, struts fully embedded and invisible. NIC was defined as heterogeneous when the NIC grade variation was ≥1. Presence of thrombus was also investigated. Distribution of dominant NIC grade (CoCr-EES: grade 0, 9%; grade 1, 77%; grade 2, 9%; grade 3, 5%; R-ZES: grade 0, 16%; grade 1: 47%; grade 2, 37%; grade 3, 0%, P = 0.38) and heterogeneity of NIC (P = 0.43) were similar between CoCr-EES and R-ZES groups. Existence of thrombus was not significantly different in CoCr-EES and R-ZES (18 versus 42%, P = 0.17). Arterial repair occurred without significant differences between CoCr-EES and R-ZES 4 months after implantation.

  4. View of the plaque to be left on the moon by the Apollo 17 astronauts

    Science.gov (United States)

    1972-01-01

    View of the plaque to be left at the Taurus-Littrow lunar landing site by the Apollo 17 astronauts. The commemorative plaque is made of stainless steel measuring nine by seven by five-eighths inches and one-sixteenth inch thick. It is attached to the ladder on the landing gear strut on the descent stage of the Apollo 17 Lunar Module 'Challenger'.

  5. Orbiter Landing Loads Math Model Description and Correlation with ALT Flight Data

    Science.gov (United States)

    Hamilton, D. A.; Schliesing, J. A.; Zupp, G. A., Jr.

    1980-01-01

    Results of the space shuttle approach and landing test are examined in order to assess landing gear characteristics and performance and verify landing dynamic analyses. The landing gears were instrumented with load-calibrated strain gages, a wheel-speed sensor, and strut stroke measurement devices. The mathematical procedure used in predicting the shuttle touchdown loads and dynamics is presented together with the comparisons between measured flight data and the analytical predictions. Conclusions from these data are also presented.

  6. Download this PDF file

    African Journals Online (AJOL)

    5c Intact left tibia after graft incorporation and bone healing. Fig. 6. Radiograph of the right radius showing evidence of incorporation of the fihular graft \\ subperiosteally and used as a strut graft to replace the radial loss. The gap left by the harvested fibular graft was left. Fig. 2 This was held in place with plate and screws and ...

  7. On the physical parametrization and magnetic analogs of the Emparan-Teo dihole solution

    International Nuclear Information System (INIS)

    Cazares, J.A.; Garcia-Compean, H.; Manko, V.S.

    2008-01-01

    The Emparan-Teo non-extremal black dihole solution is reparametrized using Komar quantities and the separation distance as arbitrary parameters. We show how the potential A 3 can be calculated for the magnetic analogs of this solution in the Einstein-Maxwell and Einstein-Maxwell-dilaton theories. We also demonstrate that, similar to the extreme case, the external magnetic field can remove the supporting strut in the non-extremal black dihole too

  8. Computational simulation of platelet interactions in the initiation of stent thrombosis due to stent malapposition

    Science.gov (United States)

    Chesnutt, Jennifer K. W.; Han, Hai-Chao

    2016-02-01

    Coronary stenting is one of the most commonly used approaches to open coronary arteries blocked due to atherosclerosis. Stent malapposition can induce thrombosis but the microscopic process is poorly understood. The objective of this study was to determine the platelet-level process by which different extents of stent malapposition affect the initiation of stent thrombosis. We utilized a discrete element model to computationally simulate the transport, adhesion, and activation of thousands of individual platelets and red blood cells during thrombus initiation in stented coronary arteries. Simulated arteries contained a malapposed stent with a specified gap distance (0, 10, 25, 50, or 200 μm) between the struts and endothelium. Platelet-level details of thrombus formation near the proximal-most strut were measured during the simulations. The relationship between gap distance and amount of thrombus in the artery varied depending on different conditions (e.g., amount of dysfunctional endothelium, shear-induced activation of platelets, and thrombogenicity of the strut). Without considering shear-induced platelet activation, the largest gap distance (200 μm) produced no recirculation and less thrombus than the smallest two gap distances (0 and 10 μm) that created recirculation downstream of the strut. However, with the occurrence of shear-induced platelet activation, the largest gap distance produced more thrombus than the two smallest gap distances, but less thrombus than an intermediate gap distance (25 μm). A large gap distance was not necessarily the most thrombogenic, in contrast to implications of some computational fluid dynamics studies. The severity of stent malapposition affected initial stent thrombosis differently depending on various factors related to fluid recirculation, platelet trajectories, shear stress, and endothelial condition.

  9. Light-harvesting and ultrafast energy migration in porphyrin-based metal-organic frameworks.

    Science.gov (United States)

    Son, Ho-Jin; Jin, Shengye; Patwardhan, Sameer; Wezenberg, Sander J; Jeong, Nak Cheon; So, Monica; Wilmer, Christopher E; Sarjeant, Amy A; Schatz, George C; Snurr, Randall Q; Farha, Omar K; Wiederrecht, Gary P; Hupp, Joseph T

    2013-01-16

    Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal-organic frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts [5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinato]zinc(II) and [5,15-bis[4-(pyridyl)ethynyl]-10,20-diphenylporphinato]zinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ~45 porphyrin struts within its lifetime in DA-MOF (but only ~3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.

  10. Active-passive integrated vibration control for control moment gyros and its application to satellites

    Science.gov (United States)

    Zhang, Yao; Zang, Yue; Li, Mou; Wang, Youyi; Li, Wenbo

    2017-04-01

    The strategy of active-passive integrated vibration control on the truss enveloping control moment gyroscopes (CMGs) is presented and its characteristics of time domain and frequency domain are analyzed. Truss enveloping CMGs contains pyramid-type CMGs, which are enveloped by multiple struts. These struts can be employed to realize the active-passive integrated vibration control. In addition, the struts of the trusses can maintain the working space of CMGs. Firstly, the disturbance characteristics of CMGs are analyzed considering static and dynamic imbalances of the CMG's rotor; then, an active-passive integrated vibration isolation truss structure is developed based on its characteristics. This structure can restrain the CMG vibration as much as possible and reduce its influence on the photographic quality of optical payloads. Next, the dynamic model of the active-passive vibration isolation truss structure is established. The frequency domain analysis of this model shows that the active-passive integrated vibration control method can restrain the high-frequency vibration and also improve the characteristics of low-frequency vibration. Finally, the dynamic model for the whole satellite is built with this type of CMGs. The time domain simulations of satellite attitude control verify the attitude control improvements resulting from the CMGs vibration control strategy.

  11. Characteristics of stent thrombosis in bifurcation lesions analysed by optical coherence tomography.

    Science.gov (United States)

    Bechiri, Mohamed Y; Souteyrand, Geraud; Lefèvre, Thierry; Trouillet, Charlotte; Rangé, Gregoire; Cayla, Guillaume; Dérimay, François; Mangin, Lionel; Meneveau, Nicolas; Caussin, Christophe; Motreff, Pascal; Amabile, Nicolas

    2018-04-06

    This work aimed to investigate a cohort of patients presenting with stent thrombosis (ST) explored by optical coherence tomography (OCT) to identify the underlying mechanical abnormalities in case of bifurcation lesions. The PESTO study was a prospective national registry involving 29 French catheterisation facilities. Patients with acute coronary syndromes were prospectively screened for presence of definite ST and analysed by OCT after culprit lesion reopening. The cohort involved 120 subjects, including 21 patients (17.5% of the global PESTO group; median age: 62.6 yrs; 76% male) with bifurcation lesions. The clinical presentation was acute or subacute ST in 34%, late ST in 5% and very late ST in 62% of the patients. The main underlying mechanisms were strut malapposition in 33%, stent underexpansion in 19% and isolated strut uncoverage in 19% of the cases. The proximal main branch was involved in 71%, distal main branch in 52% and jailed side branch in 5% of the patients. In this cohort, bifurcation lesions represented a limited number of all ST cases. Different sections of the bifurcation could be involved. Although the underlying mechanisms were various, strut malapposition was the most frequently observed cause.

  12. Phenotypic divergence of secondary sexual traits among sage grouse, Centrocercus urophasianus, populations

    Science.gov (United States)

    Young, Jessica R.; Hupp, Jerry W.; Bradbury, Jack W.; Braun, Clait E.

    1994-01-01

    Sage grouse, Centrocercus urophasianus, in an isolated montane basin near Gunnison, Colorado differ in several morphological and behavioural traits from conspecifics studied in other areas of the species' range. Both sexes in Gunnison are smaller than sage grouse elsewhere, and males possess differences in feather morphology as well. The mating behaviour of male sage grouse in three populations was examined to determine whether male strut displays of Gunnison sage grouse were behaviourally distinct. Behavioural analyses revealed Gunnison males perform strut displays at a slower rate than males in the two other sage grouse populations sampled. In addition, Gunnison males' strut displays contain unique visual and acoustical aspects. The most distinguishing attributes of Gunnison sage grouse were male secondary sexual characteristics including traits that correlate with mating success in other populations. Thus, phenotypic differences observed in the Gunnison population represent a divergence in expression of traits that are likely to be influenced by sexual selection. Recent models of speciation suggest that species characterized by intense sexual selection, such as those with lek mating systems, have the potential for rapid inter-populational divergence in male traits and female preferences leading to speciation.

  13. Test Program for High Efficiency Gas Turbine Exhaust Diffuser

    Energy Technology Data Exchange (ETDEWEB)

    Norris, Thomas R.

    2009-12-31

    This research relates to improving the efficiency of flow in a turbine exhaust, and thus, that of the turbine and power plant. The Phase I SBIR project demonstrated the technical viability of “strutlets” to control stalls on a model diffuser strut. Strutlets are a novel flow-improving vane concept intended to improve the efficiency of flow in turbine exhausts. Strutlets can help reduce turbine back pressure, and incrementally improve turbine efficiency, increase power, and reduce greenhouse gas emmission. The long-term goal is a 0.5 percent improvement of each item, averaged over the US gas turbine fleet. The strutlets were tested in a physical scale model of a gas turbine exhaust diffuser. The test flow passage is a straight, annular diffuser with three sets of struts. At the end of Phase 1, the ability of strutlets to keep flow attached to struts was demonstrated, but the strutlet drag was too high for a net efficiency advantage. An independently sponsored followup project did develop a highly-modified low-drag strutlet. In combination with other flow improving vanes, complicance to the stated goals was demonstrated for for simple cycle power plants, and to most of the goals for combined cycle power plants using this particular exhaust geometry. Importantly, low frequency diffuser noise was reduced by 5 dB or more, compared to the baseline. Appolicability to other diffuser geometries is yet to be demonstrated.

  14. Compression-compression fatigue of open cell aluminum foams: macro-/micro- mechanisms and the effects of heat treatment

    International Nuclear Information System (INIS)

    Zhou, J.; Soboyejo, W.O.

    2004-01-01

    This paper presents the results of an experimental study of the fatigue mechanisms of Duocel[reg] open cell aluminum foams and the effects of heat treatment on foam fatigue behaviour. The macro-/micro-mechanisms of fatigue were studied for the foams in the as-fabricated (F), annealed (O) and T6-strengthened (T6) conditions. The effects of annealing and T6-strengthening on the stress-strain behavior and plastic collapse strengths of foams were introduced before presenting the results of compression-compression fatigue experiments. The formation of localized deformation bands were investigated using an in-situ digital camera. Scanning electron microscopy (SEM) revealed clear evidence of the surface crack nucleation in the individual struts, prior to the abrupt strain jumps. Fractographic analysis of the failed struts also revealed fatigue striations and surface crack nucleation mechanisms in the struts. Finally, a simple compression-compression fatigue mechanism is proposed to link the observed macro- and micro-scale fatigue mechanisms in open cell aluminum foams

  15. Guenter Tulip Filter Retrieval Experience: Predictors of Successful Retrieval

    International Nuclear Information System (INIS)

    Turba, Ulku Cenk; Arslan, Bulent; Meuse, Michael; Sabri, Saher; Macik, Barbara Gail; Hagspiel, Klaus D.; Matsumoto, Alan H.; Angle, John F.

    2010-01-01

    We report our experience with Guenter Tulip filter placement indications, retrievals, and procedural problems, with emphasis on alternative retrieval techniques. We have identified 92 consecutive patients in whom a Guenter Tulip filter was placed and filter removal attempted. We recorded patient demographic information, filter placement and retrieval indications, procedures, standard and nonstandard filter retrieval techniques, complications, and clinical outcomes. The mean time to retrieval for those who experienced filter strut penetration was statistically significant [F(1,90) = 8.55, p = 0.004]. Filter strut(s) IVC penetration and successful retrieval were found to be statistically significant (p = 0.043). The filter hook-IVC relationship correlated with successful retrieval. A modified guidewire loop technique was applied in 8 of 10 cases where the hook appeared to penetrate the IVC wall and could not be engaged with a loop snare catheter, providing additional technical success in 6 of 8 (75%). Therefore, the total filter retrieval success increased from 88 to 95%. In conclusion, the Guenter Tulip filter has high successful retrieval rates with low rates of complication. Additional maneuvers such as a guidewire loop method can be used to improve retrieval success rates when the filter hook is endothelialized.

  16. Patient-specific puzzle implant preformed with 3D-printed rapid prototype model for combined orbital floor and medial wall fracture.

    Science.gov (United States)

    Kim, Young Chul; Min, Kyung Hyun; Choi, Jong Woo; Koh, Kyung S; Oh, Tae Suk; Jeong, Woo Shik

    2017-11-29

    The management of combined orbital floor and medial wall fractures involving the inferomedial strut is challenging due to absence of stable cornerstone. In this article, we proposed surgical strategies using customized 3D puzzle implant preformed with Rapid Prototype (RP) skull model. Retrospective review was done in 28 patients diagnosed with combined orbital floor and medial wall fracture. Using preoperative CT scans, original and mirror-imaged RP skull models for each patient were prepared and sterilized. In all patients, porous polyethylene-coated titanium mesh was premolded onto RP skull model in two ways; Customized 3D jigsaw puzzle technique was used in 15 patients with comminuted inferomedial strut, whereas individual 3D implant technique was used in each fracture for 13 patients with intact inferomedial strut. Outcomes including enophthalmos, visual acuity, and presence of diplopia were assessed and orbital volume was measured using OsiriX software preoperatively and postoperatively. Satisfactory results were achieved in both groups in terms of clinical improvements. Of 10 patients with preoperative diplopia, 9 improved in 6 months, except one with persistent symptom who underwent extraocular muscle rupture. 18 patients who had moderate to severe enophthalmos preoperatively improved, and one remained with mild degree. Orbital volume ratio, defined as volumetric ratio between affected and control orbit, decreased from 127.6% to 99.79% (p orbital floor and medial wall fractures. Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  17. Rehabilitation of a concrete buttress dam for seismic loads

    International Nuclear Information System (INIS)

    Pataky, T.J.; Kemp, B.G.

    1990-01-01

    A comprehensive inspection and review of the Jordan River Dam, part of the Jordan River Power Development on Vancouver Island, carried out in 1985 by British Columbia Hydro's dam safety program, identified the need for a deficiency investigation. This involved foundation exploration, field non-destructive sampling of buttress sections, removal and testing of concrete samples and dynamic structural analyses. The main conclusion of the investigation was that the buttress dam would likely fail under an earthquake with a horizontal cross-canyon acceleration in the range of 0.05-0.10 gravities. The failure of the dam would result in uncontrolled release of the reservoir, which was considered unacceptable. Cost estimates of the various rehabilitation alternatives indicated that strengthening of the buttresses with a system of cast-in-place reinforced concrete pilasters and struts would be cost effective. Rigorous, iterative finite element analyses allowed for the optimization of the final design, which was proven to be significantly below initial cost estimates. Details are provided of computer models for the analyses, sensitivity studies, optimization of the pilaster-strut layout, and design of pilasters, struts, slabs, buttress reinforcing strips, and anchors. 13 refs., 18 figs

  18. GPU-Accelerated Framework for Intracoronary Optical Coherence Tomography Imaging at the Push of a Button

    Science.gov (United States)

    Han, Myounghee; Kim, Kyunghun; Jang, Sun-Joo; Cho, Han Saem; Bouma, Brett E.; Oh, Wang-Yuhl; Ryu, Sukyoung

    2015-01-01

    Frequency domain optical coherence tomography (FD-OCT) has become one of the important clinical tools for intracoronary imaging to diagnose and monitor coronary artery disease, which has been one of the leading causes of death. To help more accurate diagnosis and monitoring of the disease, many researchers have recently worked on visualization of various coronary microscopic features including stent struts by constructing three-dimensional (3D) volumetric rendering from series of cross-sectional intracoronary FD-OCT images. In this paper, we present the first, to our knowledge, "push-of-a-button" graphics processing unit (GPU)-accelerated framework for intracoronary OCT imaging. Our framework visualizes 3D microstructures of the vessel wall with stent struts from raw binary OCT data acquired by the system digitizer as one seamless process. The framework reports the state-of-the-art performance; from raw OCT data, it takes 4.7 seconds to provide 3D visualization of a 5-cm-long coronary artery (of size 1600 samples x 1024 A-lines x 260 frames) with stent struts and detection of malapposition automatically at the single push of a button. PMID:25880375

  19. The Effect of Structural Design on Mechanical Properties and Cellular Response of Additive Manufactured Titanium Scaffolds

    Directory of Open Access Journals (Sweden)

    Jan Wieding

    2012-08-01

    Full Text Available Restoration of segmental defects in long bones remains a challenging task in orthopedic surgery. Although autologous bone is still the ‘Gold Standard’ because of its high biocompatibility, it has nevertheless been associated with several disadvantages. Consequently, artificial materials, such as calcium phosphate and titanium, have been considered for the treatment of bone defects. In the present study, the mechanical properties of three different scaffold designs were investigated. The scaffolds were made of titanium alloy (Ti6Al4V, fabricated by means of an additive manufacturing process with defined pore geometry and porosities of approximately 70%. Two scaffolds exhibited rectangular struts, orientated in the direction of loading. The struts for the third scaffold were orientated diagonal to the load direction, and featured a circular cross-section. Material properties were calculated from stress-strain relationships under axial compression testing. In vitro cell testing was undertaken with human osteoblasts on scaffolds fabricated using the same manufacturing process. Although the scaffolds exhibited different strut geometry, the mechanical properties of ultimate compressive strength were similar (145–164 MPa and in the range of human cortical bone. Test results for elastic modulus revealed values between 3.7 and 6.7 GPa. In vitro testing demonstrated proliferation and spreading of bone cells on the scaffold surface.

  20. A Computational Model to Assess Poststenting Wall Stresses Dependence on Plaque Structure and Stenosis Severity in Coronary Artery

    Directory of Open Access Journals (Sweden)

    Zuned Hajiali

    2014-01-01

    Full Text Available The current study presents computational models to investigate the poststenting hemodynamic stresses and internal stresses over/within the diseased walls of coronary arteries which are in different states of atherosclerotic plaque. The finite element method is applied to build the axisymmetric models which include the plaque, arterial wall, and stent struts. The study takes into account the mechanical effects of the opening pressure and its association with the plaque severity and the morphology. The wall shear stresses and the von Mises stresses within the stented coronary arteries show their strong dependence on the plaque structure, particularly the fibrous cap thickness. Higher stresses occur in severely stenosed coronaries with a thinner fibrous cap. Large stress concentrations around the stent struts cause injury or damage to the vessel wall which is linked to the mechanism of restenosis. The in-stent restenosis rate is also highly dependent on the opening pressure, to the extent that stenosed artery is expanded, and geometry of the stent struts. The present study demonstrates, for the first time, that the restenosis is to be viewed as a consequence of biomechanical design of a stent repeating unit, the opening pressure, and the severity and morphology of the plaque.

  1. Solar dynamic power systems for space station

    Science.gov (United States)

    Irvine, Thomas B.; Nall, Marsha M.; Seidel, Robert C.

    1986-01-01

    The Parabolic Offset Linearly Actuated Reflector (POLAR) solar dynamic module was selected as the baseline design for a solar dynamic power system aboard the space station. The POLAR concept was chosen over other candidate designs after extensive trade studies. The primary advantages of the POLAR concept are the low mass moment of inertia of the module about the transverse boom and the compactness of the stowed module which enables packaging of two complete modules in the Shuttle orbiter payload bay. The fine pointing control system required for the solar dynamic module has been studied and initial results indicate that if disturbances from the station are allowed to back drive the rotary alpha joint, pointing errors caused by transient loads on the space station can be minimized. This would allow pointing controls to operate in bandwidths near system structural frequencies. The incorporation of the fine pointing control system into the solar dynamic module is fairly straightforward for the three strut concentrator support structure. However, results of structural analyses indicate that this three strut support is not optimum. Incorporation of a vernier pointing system into the proposed six strut support structure is being studied.

  2. Cell adhesion on NiTi thin film sputter-deposited meshes.

    Science.gov (United States)

    Loger, K; Engel, A; Haupt, J; Li, Q; Lima de Miranda, R; Quandt, E; Lutter, G; Selhuber-Unkel, C

    2016-02-01

    Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium(NiTi) thin film mesheswere produced by means of magnetron sputter deposition.Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm2 and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133+) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm2 and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applicationsin cardiovascular tissue engineering, particularly for the fabrication of heart valves.

  3. Comparison of the influences of structural characteristics on bulk mechanical behaviour: experimental study using a bone surrogate.

    Science.gov (United States)

    Levasseur, A; Ploeg, H-L; Petit, Y

    2012-01-01

    An experimental study was conducted to classify the influence of trabecular architecture and cortical shell thickness on the mechanical properties using a bone surrogate. Thirty-six rectangular prisms and 18 vertebral-shaped specimens were fabricated with fused deposition modelling (FDM) as a bone surrogate with controlled structural characteristics (cortical wall thickness, strut spacing, strut angle and strut orientation). The apparent density of the FDM specimens was evaluated using quantitative computed tomography (QCT) imaging and related to the apparent elastic modulus measured with compression testing. The effects of the structural parameters on the apparent elastic modulus were analysed using analysis of variance (ANOVA). The results obtained corroborate that the structural parameters have a significant effect on the apparent mechanical properties of the bulk material. The cortical shell thickness was found to have more influence than trabecular architecture. Therefore, accurate modelling of the cortical shell thickness should be considered more important than trabecular architecture in development of bone finite element models and bone surrogates.

  4. Caval penetration by retrievable inferior vena cava filters: a retrospective comparison of Option and Günther Tulip filters.

    Science.gov (United States)

    Olorunsola, Olufoladare G; Kohi, Maureen P; Fidelman, Nicholas; Westphalen, Antonio C; Kolli, Pallav K; Taylor, Andrew G; Gordon, Roy L; LaBerge, Jeanne M; Kerlan, Robert K

    2013-04-01

    To compare the frequency of vena caval penetration by the struts of the Option and Günther Tulip cone filters on postplacement computed tomography (CT) imaging. All patients who had an Option or Günther Tulip inferior vena cava (IVC) filter placed between January 2010 and May 2012 were identified retrospectively from medical records. Of the 208 IVC filters placed, the positions of 58 devices (21 Option filters, 37 Günther Tulip filters [GTFs]) were documented on follow-up CT examinations obtained for reasons unrelated to filter placement. In cases when multiple CT studies were obtained after placement, each study was reviewed, for a total of 80 examinations. Images were assessed for evidence of caval wall penetration by filter components, noting the number of penetrating struts and any effect on pericaval tissues. Penetration of at least one strut was observed in 17% of all filters imaged by CT between 1 and 447 days following placement. Although there was no significant difference in the overall prevalence of penetration when comparing the Option filter and GTF (Option, 10%; GTF, 22%), only GTFs showed time-dependent penetration, with penetration becoming more likely after prolonged indwelling times. No patient had damage to pericaval tissues or documented symptoms attributed to penetration. Although the Günther Tulip and Option filters exhibit caval penetration at CT imaging, only the GTF exhibits progressive penetration over time. Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.

  5. Collagen immobilization of multi-layered BCP-ZrO{sub 2} bone substitutes to enhance bone formation

    Energy Technology Data Exchange (ETDEWEB)

    Linh, Nguyen Thuy Ba [Department of Regenerative Medicine, College of Medicine, Soonchunhyang University, Cheonan, 330-090 (Korea, Republic of); Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, 330-090 (Korea, Republic of); Jang, Dong-Woo [Department of Regenerative Medicine, College of Medicine, Soonchunhyang University, Cheonan, 330-090 (Korea, Republic of); Lee, Byong-Taek, E-mail: lbt@sch.ac.kr [Department of Regenerative Medicine, College of Medicine, Soonchunhyang University, Cheonan, 330-090 (Korea, Republic of); Institute of Tissue Regeneration, College of Medicine, Soonchunhyang University, Cheonan, 330-090 (Korea, Republic of)

    2015-08-01

    Graphical abstract: - Highlights: • Col-BCP-ZrO. • Collagen fibers were formed and attached firmly on the surface of BCP-ZrO. • Highly interconnected but uniform porosity were obtained. • High biocompatible, strength scaffolds and new bone were evident in Col-BCP-ZrO{sub 2}. - Abstract: A porous microstructure of multi-layered BCP-ZrO{sub 2} bone substitutes was fabricated using the sponge replica method in which the highly interconnected structure was immobilized with collagen via ethyl(dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide crosslinking. Their struts are combined with a three-layered BCP/BCP-ZrO{sub 2}/ZrO{sub 2} microstructure. Collagen fibers were firmly attached to the strut surface of the BCP-ZrO{sub 2} scaffolds. With control of the three-layered microstructure and collagen immobilization, the compressive strength of the scaffolds increased significantly to 6.8 MPa compared to that of the monolithic BCP scaffolds (1.3 MPa). An in vitro study using MTT, confocal observation, and real-time polymer chain reaction analysis demonstrated that the proliferation and differentiation of the pre-osteoblast-like MC3T3-E1 cells was improved due to the collagen incorporation. Remarkable enhancement of bone regeneration was observed without any immunological reaction in the femurs of rabbits during 1 and 5 months of implantation. Furthermore, the interfaces between new bone and the scaffold struts bonded directly without any gaps.

  6. Collagen immobilization of multi-layered BCP-ZrO2 bone substitutes to enhance bone formation

    Science.gov (United States)

    Linh, Nguyen Thuy Ba; Jang, Dong-Woo; Lee, Byong-Taek

    2015-08-01

    A porous microstructure of multi-layered BCP-ZrO2 bone substitutes was fabricated using the sponge replica method in which the highly interconnected structure was immobilized with collagen via ethyl(dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide crosslinking. Their struts are combined with a three-layered BCP/BCP-ZrO2/ZrO2 microstructure. Collagen fibers were firmly attached to the strut surface of the BCP-ZrO2 scaffolds. With control of the three-layered microstructure and collagen immobilization, the compressive strength of the scaffolds increased significantly to 6.8 MPa compared to that of the monolithic BCP scaffolds (1.3 MPa). An in vitro study using MTT, confocal observation, and real-time polymer chain reaction analysis demonstrated that the proliferation and differentiation of the pre-osteoblast-like MC3T3-E1 cells was improved due to the collagen incorporation. Remarkable enhancement of bone regeneration was observed without any immunological reaction in the femurs of rabbits during 1 and 5 months of implantation. Furthermore, the interfaces between new bone and the scaffold struts bonded directly without any gaps.

  7. Kinerja Struktur Rangka Beton Bertulang dengan Penambahan Dinding Pengisi Berlubang sebagai Perkuatan Seismik

    Directory of Open Access Journals (Sweden)

    Ida Ayu Made Budiwati

    2017-04-01

    Full Text Available This research was conducted to develop a model of seismic retrofitting of reinforced concrete frame using infill wall with central openings, with and without lintels around the opening, by comparing the behaviour and performance of the frame structures with varying opening ratios. Prior to model the strengthened frames, validation was done by comparing the behaviour of computer models using shell element (RDPsh and diagonal strut (RDPst to those of laboratory tests conducted by others. The validation models show that the lateral load-displacement diagrams of RDPsh fit the test result better than the strut ones. It was also found that the strut width equation for opening without lintel can not be used for opening with lintels as the lintels stiffen the frame and strengthen the wall around the openings. Based on these results, the width of strut was modified to match the response of model using shell element with lintels around the opening. The RC frames of 3, 4, and 5 storey retrofitted using infill wall with central opening ratio varies from 0 to 100%, was then conducted by modeling the infill wall as an equivalent diagonal strut and shell elements in SAP2000 software. The analysis results of 3-storey frames show that, reduction on lateral drifts of 65%, 58%, 43%, 22%, and 5% was observed for opening ratio of 0%, 20%, 40%, 60%, dan 80%, respectively. Similar results were also found for the 4 and 5 storey frames. From the reinforcement requirements it can be concluded that the strengthening method can be applied with limitation on the wall opening ratios. For 3- storey frames, the addition of infill wall with opening ratio up to 60% is adequate to withstand the quake load specified in the SNI 1726:2012. For 4 and 5-storey frames however, opening ratio of 40% or less is required. Interestingly, the addition of infill wall with lintels can withstand higher base shear forces. However, the increased strength is followed by a decreased ductility in

  8. Vascular response to percutaneous coronary intervention with biodegradable-polymer vs. new-generation durable-polymer drug-eluting stents: a meta-analysis of optical coherence tomography imaging trials.

    Science.gov (United States)

    Cassese, Salvatore; Xhepa, Erion; Ndrepepa, Gjin; Kufner, Sebastian; Colleran, Roisin; Giacoppo, Daniele; Koppara, Tobias; Mankerious, Nader; Byrne, Robert A; Laugwitz, Karl-Ludwig; Schunkert, Heribert; Fusaro, Massimiliano; Kastrati, Adnan; Joner, Michael

    2018-01-02

    Whether biodegradable-polymer drug-eluting stents (BP-DES) induce a vascular response at follow-up more favourable than that of new-generation durable-polymer drug-eluting stents (DP-DES) remains controversial. We sought to evaluate the vascular response to percutaneous coronary intervention (PCI) with BP-DES vs. new-generation DP-DES as assessed by optical coherence tomography (OCT) imaging at follow-up. We undertook a meta-analysis of aggregate data by searching electronic scientific databases for investigations of PCI-patients receiving BP-DES vs. new-generation DP-DES and OCT imaging at follow-up. The primary outcome was neointima hyperplasia (NIH) thickness. The co-primary outcome was the incidence of lesions with uncovered struts. The main secondary outcome was the incidence of lesions with malapposed struts. Among 10 trials, a total of 544 PCI-patients were assigned to BP-DES (n = 282) or new-generation DP-DES (n = 262). Of these, 447 participants with 480 treated lesions had analysable OCT imaging at a weighted median follow-up of 7 months. Lesions treated with BP-DES vs. new-generation DP-DES showed comparable NIH thickness [weighted mean difference 95% confidence intervals (CI)  = -11.37 (-29.25, 6.52); P = 0.21]. However, thick-struts (>100 μm) BP-DES showed less NIH thickness as compared to new-generation DP-DES [-20.39 (-33.83, -6.95); P = 0.003]. BP-DES vs. new-generation DP-DES showed a higher risk for uncovered struts [odds ratio 95% CI = 3.50 (1.69-7.26); P = 0.0008] and a trend towards higher risk for malapposed struts [2.01 (0.98-4.12); P = 0.06]. In PCI-patients with available OCT imaging at follow-up, BP-DES with thicker backbones delay vascular response as compared with new-generation DP-DES. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2018. For permissions, please email: journals.permissions@oup.com.

  9. Comparative analysis of trabecular bone structure and orientation in South African hominin tali.

    Science.gov (United States)

    Su, Anne; Carlson, Kristian J

    2017-05-01

    Tali of several hominin taxa are preserved in the fossil record and studies of the external morphology of these often show a mosaic of human-like and ape-like features. This has contributed to a growing recognition of variability characterizing locomotor kinematics of Australopithecus. In contrast, locomotor kinematics of another Plio-Pleistocene hominin, Paranthropus, are substantially less well-documented, in part, because of the paucity of postcranial fossils securely attributed to the genus. Since the talus transmits locomotor-based loads through the ankle and its internal structure is hypothesized to reflect accommodation to such loads, it is a cornerstone structure for reconstructing locomotor kinematics. Here we quantify and characterize trabecular bone morphology within tali attributed to Australopithecus africanus (StW 102, StW 363, StW 486) and Paranthropus robustus (TM 1517), making quantitative comparisons to modern humans, extant non-human apes, baboons, and a hominin talus attributed to Paranthropus boisei (KNM-ER 1464). Using high-resolution images of fossil tali (25 μm voxels), nine trabecular bone subregions of interest beneath the articular surface of the talar trochlea were segmented to quantify localized patterns in distribution and primary strut orientation. It was found that trabecular strut orientation and shape, in some cases, can discriminate amongst species characterized by different locomotor foot kinematics. Discriminant function analyses using standard trabecular bone structural properties align TM 1517 with Pan and Gorilla, while other hominin tali structurally most resemble those of baboons. In primary strut orientation, Paranthropus tali (KNM-ER 1464 and TM 1517) resemble the human condition in the anterior-medial subregion, where strut orientation appears positioned to distribute compressive loads medially and distally toward the talar head. In A. africanus tali (particularly StW 486), primary strut orientation in this region

  10. Polar Seismic TETwalker: Integrating Engineering Teaching and Research

    Science.gov (United States)

    Gifford, C. M.; Ruiz, I.; Carmichael, B. L.; Wade, U. B.; Agah, A.

    2007-12-01

    Based on the TETwalker robot platform at NASA/Goddard Space Flight Center, the Center for Remote Sensing of Ice Sheets (CReSIS) has begun work on designing and modeling the integration of seismic surveying equipment into the TETwalker robot architecture for use in polar environments. Employing multiple Seismic TETwalker robots will allow gathering of polar seismic data in previously inaccessible or unexplored terrains, as well as help significantly reduce human involvement in such harsh environments. NASA's TETwalker mobile robot uses a unique form of mobility to topple across the surface and over obstacles. This robot therefore does not suffer the fate of other wheeled and tracked robots if tipped over. It is composed of extending struts and nodes, forming a tetrahedral shape which can be strategically adjusted to change the robot's center of gravity for toppling. Of the many platforms the TETwalker architecture can form, the 4-TETwalker robot (consisting of four ground nodes, a center payload node, and interconnecting struts) has been the focus of current research. The center node has been chosen as the geophone deployment medium, designed in such a way to allow geophone insertion using any face of the robot's structure. As the robot comes to rest at the deployment location, one of its faces will rest on the surface. No matter which side it is resting on, a geophone spike will be perpendicular to its face and an extending strut will be vertical for pushing the geophone into the ground. Lengthening and shortening struts allow the deployment node to precisely place the geophone into the ground, as well as vertically orient the geophones for proper data acquisition on non-flat surfaces. Power source integration has been investigated, incorporating possible combinations of solar, wind, and vibration power devices onboard the robot models for long-term survival in a polar environment. Designs have also been modeled for an alternate center node sensor package (e

  11. Measurement of in vitro and in vivo stent geometry and deformation by means of 3D imaging and stereo-photogrammetry.

    Science.gov (United States)

    Zwierzak, Iwona; Cosentino, Daria; Narracott, Andrew J; Bonhoeffer, Philipp; Diaz, Vanessa; Fenner, John W; Schievano, Silvia

    2014-12-01

    To quantify variability of in vitro and in vivo measurement of 3D device geometry using 3D and biplanar imaging. Comparison of stent reconstruction is reported for in vitro coronary stent deployment (using micro-CT and optical stereo-photogrammetry) and in vivo pulmonary valve stent deformation (using 4DCT and biplanar fluoroscopy). Coronary stent strut length and inter-strut angle were compared in the fully deployed configuration. Local (inter-strut angle) and global (dog-boning ratio) measures of stent deformation were reported during stent deployment. Pulmonary valve stent geometry was assessed throughout the cardiac cycle by reconstruction of stent geometry and measurement of stent diameter. Good agreement was obtained between methods for assessment of coronary stent geometry with maximum disagreement of +/- 0.03 mm (length) and +/- 3 degrees (angle). The stent underwent large, non-uniform, local deformations during balloon inflation, which did not always correlate with changes in stent diameter. Three-dimensional reconstruction of the pulmonary valve stent was feasible for all frames of the fluoroscopy and for 4DCT images, with good correlation between the diameters calculated from the two methods. The largest compression of the stent during the cardiac cycle was 6.98% measured from fluoroscopy and 7.92% from 4DCT, both in the most distal ring. Quantitative assessment of stent geometry reconstructed from biplanar imaging methods in vitro and in vivo has shown good agreement with geometry reconstructed from 3D techniques. As a result of their short image acquisition time, biplanar methods may have significant advantages in the measurement of dynamic 3D stent deformation.

  12. Structures and Mechanisms Design Concepts for Adaptive Deployable Entry Placement Technology

    Science.gov (United States)

    Yount, Bryan C.; Arnold, James O.; Gage, Peter J.; Mockelman, Jeffrey; Venkatapathy, Ethiraj

    2012-01-01

    System studies have shown that large deployable aerodynamic decelerators such as the Adaptive Deployable Entry and Placement Technology (ADEPT) concept can revolutionize future robotic and human exploration missions involving atmospheric entry, descent and landing by significantly reducing the maximum heating rate, total heat load, and deceleration loads experienced by the spacecraft during entry [1-3]. ADEPT and the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) [4] share the approach of stowing the entry system in the shroud of the launch vehicle and deploying it to a much larger diameter prior to entry. The ADEPT concept provides a low ballistic coefficient for planetary entry by employing an umbrella-like deployable structure consisting of ribs, struts and a fabric cover that form an aerodynamic decelerator capable of undergoing hypersonic flight. The ADEPT "skin" is a 3-D woven carbon cloth that serves as a thermal protection system (TPS) and as a structural surface that transfers aerodynamic forces to the underlying ribs [5]. This paper focuses on design activities associated with integrating ADEPT components (cloth, ribs, struts and mechanisms) into a system that can function across all configurations and environments of a typical mission concept: stowed during launch, in-space deployment, entry, descent, parachute deployment and separation from the landing payload. The baseline structures and mechanisms were selected via trade studies conducted during the summer and fall of 2012. They are now being incorporated into the design of a ground test article (GTA) that will be fabricated in 2013. It will be used to evaluate retention of the stowed configuration in a launch environment, mechanism operation for release, deployment and locking, and static strength of the deployed decelerator. Of particular interest are the carbon cloth interfaces, underlying hot structure, (Advanced Carbon- Carbon ribs) and other structural components (nose cap, struts, and

  13. Isolation, pointing, and suppression (IPS) system for high-performance spacecraft

    Science.gov (United States)

    Hindle, Tim; Davis, Torey; Fischer, Jim

    2007-04-01

    Passive mechanical isolation is often times the first step taken to remedy vibration issues on-board a spacecraft. In many cases, this is done with a hexapod of axial members or struts to obtain the desired passive isolation in all six degrees-of-freedom (DOF). In some instances, where the disturbance sources are excessive or the payload is particularly sensitive to vibration, additional steps are taken to improve the performance beyond that of passive isolation. Additional performance or functionality can be obtained with the addition of active control, using a hexapod of hybrid (passive/active) elements at the interface between the payload and the bus. This paper describes Honeywell's Isolation, Pointing, and Suppression (IPS) system. It is a hybrid isolation system designed to isolate a sensitive spacecraft payload with very low passive resonant break frequencies while affording agile independent payload pointing, on-board payload disturbance rejection, and active isolation augmentation. This system is an extension of the work done on Honeywell's previous Vibration Isolation, Steering, and Suppression (VISS) flight experiment. Besides being designed for a different size payload than VISS, the IPS strut includes a dual-stage voice coil design for improved dynamic range as well as improved low-noise drive electronics. In addition, the IPS struts include integral load cells, gap sensors, and payloadside accelerometers for control and telemetry purposes. The associated system-level control architecture to accomplish these tasks is also new for this program as compared to VISS. A summary of the IPS system, including analysis and hardware design, build, and single axis bipod testing will be reviewed.

  14. In vitro and in vivo degradation of microfiber bioresorbable coronary scaffold.

    Science.gov (United States)

    Huang, Chi-Hung; Lee, Sheng-Yang; Horng, Sonida; Guy, Louis-Georges; Yu, Ting-Bin

    2017-09-18

    The degradation of Mirage Bioresorbable Microfiber Scaffold was evaluated in vitro and in vivo. The degradation in polymer molecular weight (MW), strut morphology, and integrity was accessed using gel permeation chromatography (GPC), X-ray micro-computed tomography (micro-CT) evaluation. To simulate the physiological degradation in vitro, scaffolds were deployed in silicone mock vessels connected to a peristaltic pumping system, which pumps 37°C phosphate-buffered saline (PBS, pH 7.4) at a constant rate. At various time points (30D, 60D, 90D, 180D, 270D, and 360D), the MW of microfibers decreased to 57.3, 49.8, 36.9, 13.9, 6.4, and 5.1% against the baseline. The in vivo degradation study was performed by implanting scaffolds in internal thoracic arteries (ITAs) of mini-swine. At the scheduled sacrifice time points (30D, 90D, 180D, 270D, 360D, and 540D), the implanted ITAs were excised for GPC analysis; the MW of the implanted scaffolds dropped to 58.5, 34.7, 24.8, 16.1, 12.9, and 7.1, respectively. Mass loss of scaffolds reached 72.4% at 540D of implantation. Two stages of hydrolysis were observed in in vitro and in vivo degradation kinetics, and the statistical analysis suggested a positive correlation between in vivo and in vitro degradation. After 6 months of incubation in animals, significant strut degradation was seen in the micro-CT evaluation in all sections as strut fragments and separations. The micro-CT results further confirmed that every sample at 720D had X-ray transmission similar to surrounding tissue, thereby indicating full degradation within 2 years. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

  15. Pair of accelerated black holes in a de Sitter background: The dS C metric

    International Nuclear Information System (INIS)

    Dias, Oscar J.C.; Lemos, Jose P.S.

    2003-01-01

    Following the work of Kinnersley and Walker for flat spacetimes, we analyzed the anti-de Sitter C metric in a previous paper. In this paper we study the de Sitter C metric (dS C metric). The C metric with a generic cosmological constant and other extra parameters was introduced by Plebanski and Demianski. When one then sets to zero some of the extra parameters, and works with a positive cosmological constant, one has the dS C metric which has been analyzed and physically interpreted by Podolsky and Griffiths. It describes a pair of accelerated black holes in the dS background with the acceleration being provided (in addition to the cosmological constant) by a strut that pushes away the two black holes or, alternatively, by a string that pulls them. We extend their analysis mainly in four directions. First, we draw the Carter-Penrose diagrams of the massless uncharged dS C metric, of the massive uncharged dS C metric and of the massive charged dS C metric. These diagrams allow us to clearly identify the presence of two dS black holes and to conclude that they cannot interact gravitationally. Second, we reexamine the embedding of the dS C metric in the 5D Minkowski spacetime and we represent the motion of the dS C metric origin in the dS 4-hyperboloid as well as the localization of the strut. Third, we comment on the physical properties of the strut that connects the two black holes. Finally, we find the range of parameters that correspond to nonextreme black holes, extreme black holes, and naked particles

  16. Magnetizable stent-grafts enable endothelial cell capture

    Energy Technology Data Exchange (ETDEWEB)

    Tefft, Brandon J. [Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN (United States); Uthamaraj, Susheil [Division of Engineering, Mayo Clinic, Rochester, MN (United States); Harburn, J. Jonathan [School of Medicine, Pharmacy and Health, Durham University, Stockton-on-Tees (United Kingdom); Hlinomaz, Ota [Department of Cardioangiology, St. Anne' s University Hospital, Brno (Czech Republic); Lerman, Amir [Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN (United States); Dragomir-Daescu, Dan [Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN (United States); Sandhu, Gurpreet S., E-mail: sandhu.gurpreet@mayo.edu [Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN (United States)

    2017-04-01

    Emerging nanotechnologies have enabled the use of magnetic forces to guide the movement of magnetically-labeled cells, drugs, and other therapeutic agents. Endothelial cells labeled with superparamagnetic iron oxide nanoparticles (SPION) have previously been captured on the surface of magnetizable 2205 duplex stainless steel stents in a porcine coronary implantation model. Recently, we have coated these stents with electrospun polyurethane nanofibers to fabricate prototype stent-grafts. Facilitated endothelialization may help improve the healing of arteries treated with stent-grafts, reduce the risk of thrombosis and restenosis, and enable small-caliber applications. When placed in a SPION-labeled endothelial cell suspension in the presence of an external magnetic field, magnetized stent-grafts successfully captured cells to the surface regions adjacent to the stent struts. Implantation within the coronary circulation of pigs (n=13) followed immediately by SPION-labeled autologous endothelial cell delivery resulted in widely patent devices with a thin, uniform neointima and no signs of thrombosis or inflammation at 7 days. Furthermore, the magnetized stent-grafts successfully captured and retained SPION-labeled endothelial cells to select regions adjacent to stent struts and between stent struts, whereas the non-magnetized control stent-grafts did not. Early results with these prototype devices are encouraging and further refinements will be necessary in order to achieve more uniform cell capture and complete endothelialization. Once optimized, this approach may lead to more rapid and complete healing of vascular stent-grafts with a concomitant improvement in long-term device performance. - Highlights: • Magnetic stent-grafts were made from 2205 steel stents and polyurethane nanofibers. • Stent-grafts remained patent and formed a thin and uniform neointima when implanted. • Stent-grafts captured endothelial cells labeled with magnetic nanoparticles.

  17. Development of asymmetric stent for treatment of eccentric plaque.

    Science.gov (United States)

    Syaifudin, Achmad; Takeda, Ryo; Sasaki, Katsuhiko

    2018-01-01

    The selection of stent and balloon type is decisive in the stenting process. In the treatment of an eccentric plaque obstruction, a symmetric expansion from stent dilatation generates nonuniform stress distribution, which may aggravate fibrous cap prone to rupture. This paper developed a new stent design to treat eccentric plaque using structural transient dynamic analysis in ANSYS. A non-symmetric structural geometry of stent is generated to obtain reasonable stress distribution safe for the arterial layer surrounding the stent. To derive the novel structural geometry, a Sinusoidal stent type is modified by varying struts length and width, adding bridges, and varying curvature width of struts. An end ring of stent struts was also modified to eliminate dogboning phenomenon and to reduce the Ectropion angle. Two balloon types were used to deploy the stent, an ordinary cylindrical and offset balloon. Positive modification results were used to construct the final non-symmetric stent design, called an Asymmetric stent. Analyses of the deformation characteristics, changes in surface roughness and induced stresses within intact arterial layer were subsequently examined. Interaction between the stent and vessel wall was implemented by means of changes in surface roughness and stress distribution analyses. The Palmaz and the Sinusoidal stent were used for a comparative study. This study indicated that the Asymmetric stent types reduced the central radial recoiling and the dogboning phenomenon. In terms of changes in surface roughness and induced stresses, the Asymmetric stent has a comparable effect with that of the Sinusoidal stent. In addition, it could enhance the distribution of surface roughening as expanded by an offset balloon.

  18. In vitro biomechanics of an expandable vertebral body replacement with self-adjusting end plates.

    Science.gov (United States)

    Buttermann, Glenn R; Freeman, Andrew L; Beaubien, Brian P

    2010-11-01

    Unstable burst fractures of the thoracolumbar spine may be treated surgically. Vertebral body replacements (VBRs) give anterior column support and, when used with supplemental fixation, impart rigidity to the injured segments. Although some VBRs are expandable, device congruity to the vertebral end plates is imprecise and may lead to stress risers and device subsidence. The objective of this study was to compare the rigidity of a VBR that self-adjusts to the adjacent vertebral end plates versus structural bone allograft and with an unsupported anterior column in a traumatic burst fracture reconstruction model. Biomechanical flexibility testing with rod strain measurement. Twelve T11-L3 human spine segments. Range of motion, neutral zone, and posterior fixation rod stress (moments). Flexibility testing was performed to ± 6 Nm in flexion-extension, lateral bending, and axial rotation on 12 intact human T11-L3 specimens. Burst fractures were created in L1, and flexibility testing was repeated in three additional states: subtotal corpectomy with posterior instrumentation (PI) only from T12 to L2, reconstruction with a femoral strut allograft and PI, and reconstruction with a VBR (with self-adjusting end plates) and PI. The PI consisted of pedicle screws and strain gage instrumented rods that were calibrated to measure rod stress via flexion-extension bending moments. There was no statistical difference in range of motion or neutral zone between the strut graft and VBR constructs, which both had less motion than the PI-only construct in flexion/extension and torsion and were both less than the intact values in flexion/extension and lateral bending (p combined with PI. Posterior rod stress was not significantly increased with this type of VBR compared with the strut graft reconstruction. The benefits of burst fracture stabilization using a self-adjusting VBR ultimately will not be known until long-term clinical studies are performed. Copyright © 2010 Elsevier Inc. All

  19. Impact of Cigarette Smoking and Smoking Cessation on Stent Changes as Determined by Optical Coherence Tomography After Sirolimus Stent Implantation.

    Science.gov (United States)

    Huang, Xingtao; Wang, Xuedong; Zou, Yongpeng; Chen, Shuyuan; Zhang, Ruoxi; Li, Lulu; Yu, Bo; Hou, Jingbo

    2017-10-15

    There is debate regarding whether smoking results in microstructural changes after stenting. The aim of this study was to evaluate the microstructural changes after stenting in patients with different smoking statuses. We retrospectively identified 220 sirolimus-eluting stents in 179 patients who underwent follow-up optical coherence tomography examination 12 months after sirolimus stenting. Subjects were classified as current smokers (CS, n = 31), smoking cessation ≤1 year (n = 36), smoking cessation >1 year (SC > 1Y, n = 27), and never smokers (NS, n = 85). The neointimal hyperplasia (NIH) area was larger in CS than in NS (1.04 ± 0.72 mm 2 vs 0.96 ± 0.68 mm 2 ; p = 0.04). The incidence of lipid-laden neointima was lower in SC > 1Y patients (1.6%) than in all other patients (NS: 3.9%, p = 0.002; CS: 3.0%, p = 0.073; SC1Y: 5.0%, p Smoking cessation level was negatively correlated with NIH (B = -0.154; 95% confidential interval -0.187, -0.121; p smoking cessation patients showed a decreased trend in the incidence of malapposed struts (p = 0.0003). In conclusion, continued smoking increases NIH and the incidence of malapposed struts. However, smoking cessation slows down NIH progression and decreases the incidence of malapposed struts. Smoking cessation promotes vascular healing after stenting. Copyright © 2017. Published by Elsevier Inc.

  20. Cell adhesion on NiTi thin film sputter-deposited meshes

    Energy Technology Data Exchange (ETDEWEB)

    Loger, K. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Engel, A.; Haupt, J. [Department of Cardiovascular Surgery, University Hospital of Schleswig-Holstein, Kiel (Germany); Li, Q. [Biocompatible Nanomaterials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Lima de Miranda, R. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); ACQUANDAS GmbH, Kiel (Germany); Quandt, E. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Lutter, G. [Department of Cardiovascular Surgery, University Hospital of Schleswig-Holstein, Kiel (Germany); Selhuber-Unkel, C. [Biocompatible Nanomaterials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany)

    2016-02-01

    Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium (NiTi) thin film meshes were produced by means of magnetron sputter deposition. Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm{sup 2} and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133 +) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm{sup 2} and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applications in cardiovascular tissue engineering, particularly for the fabrication of heart valves. - Highlights: • Freestanding NiTi thin film scaffolds were fabricated with magnetron sputtering process. • Effective mechanical properties of NiTi scaffolds can be adapted by the mesh structure parameters. • Cell adhesion on the NiTi thin film scaffold is controlled by the structure parameters of the mesh. • Cells strongly adhere after seven days and form a confluent layer on the mesh.