Prediction of Hot Tearing Using a Dimensionless Niyama Criterion

Science.gov (United States)

Monroe, Charles; Beckermann, Christoph

2014-08-01

The dimensionless form of the well-known Niyama criterion is extended to include the effect of applied strain. Under applied tensile strain, the pressure drop in the mushy zone is enhanced and pores grow beyond typical shrinkage porosity without deformation. This porosity growth can be expected to align perpendicular to the applied strain and to contribute to hot tearing. A model to capture this coupled effect of solidification shrinkage and applied strain on the mushy zone is derived. The dimensionless Niyama criterion can be used to determine the critical liquid fraction value below which porosity forms. This critical value is a function of alloy properties, solidification conditions, and strain rate. Once a dimensionless Niyama criterion value is obtained from thermal and mechanical simulation results, the corresponding shrinkage and deformation pore volume fractions can be calculated. The novelty of the proposed method lies in using the critical liquid fraction at the critical pressure drop within the mushy zone to determine the onset of hot tearing. The magnitude of pore growth due to shrinkage and deformation is plotted as a function of the dimensionless Niyama criterion for an Al-Cu alloy as an example. Furthermore, a typical hot tear "lambda"-shaped curve showing deformation pore volume as a function of alloy content is produced for two Niyama criterion values.

Mass-Inertial Characteristics and Dimensionless Equations of Two-bearing Rotor Motion with Auto-balancer in Terms of Compensating Body Mass

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A. N. Gorbenko

2015-01-01

Full Text Available Modern rotary machines use auto-balancing devices of passive type to provide automatic balancing of rotors and reduce vibration. Most available researches on the rotor auto-balancing dynamics and stability are based on the assumption that the compensating bodies of the autobalancer, as well as the rotor imbalance, are infinitesimal values. The literature review has shown that the problems concerning the automatic balancing of rotor with its three-dimensional motion are solved approximately and require an in-depth analysis taking into consideration the final mass of the compensating bodies.The paper analyses the effect of an auto-balancer mass on the mass-inertial properties of the three-dimensional rotor motion. It gives the autonomous equations of the system motion. The work shows that attaching the point masses of compensating auto-balancer bodies and imbalance to the rotor causes an increase, however non-identical, in all components of the total inertia tensor of the mechanical system. This leads to a qualitative change in mass-inertial characteristics of the system.The composite rotor becomes an inertia anisotropic body in which the inertia moments about the two transverse own axes are not equal to each other. The rotor anisotropy results in complicated dynamic behavior of the gyroscopic rotor. In this case, the additional critical rotor speeds and the zones of instability of motion may occur.It is shown that in the case of using multi-body auto-balancer the inertial parameters of the rotor system grow into the interval values, i.e. their values are not uniquely determined and may be equal to a variety values from a certain range. Thus, the degree of inertial anisotropy and other auto-balancing parameters are the interval values as well in this case.The system of dimensionless equations of rotary machine motion, which contains the minimum required number of dimensionless parameters, has been obtained. The specific ranges of the dimensionless

Useful scaling parameters for the pulse tube

International Nuclear Information System (INIS)

Lee, J.M.; Kittel, P.; Timmerhaus, K.D.

1996-01-01

A set of dimensionless scaling parameters for use in correlating performance data for Pulse Tube Refrigerators is presented. The dimensionless groups result after scaling the mass and energy conservation equations, and the equation of motion for an axisymmetric, two-dimensional ideal gas system. Allowed are viscous effects and conduction heat transfer between the gas and the tube wall. The scaling procedure results in reducing the original 23 dimensional variables to a set of 11 dimensionless scaling groups. Dimensional analysis is used to verify that the 11 dimensionless groups obtained is the minimum number needed to describe the system. The authors also examine 6 limiting cases which progressively reduce the number of dimensionless groups from 11 to 3. The physical interpretation of the parameters are described, and their usefulness is outlined for understanding how heat transfer and mass streaming affect ideal enthalpy flow

Comparing Jupiter and Saturn: dimensionless input rates from plasma sources within the magnetosphere

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V. M. Vasyliūnas

2008-06-01

Full Text Available The quantitative significance for a planetary magnetosphere of plasma sources associated with a moon of the planet can be assessed only by expressing the plasma mass input rate in dimensionless form, as the ratio of the actual mass input to some reference value. Traditionally, the solar wind mass flux through an area equal to the cross-section of the magnetosphere has been used. Here I identify another reference value of mass input, independent of the solar wind and constructed from planetary parameters alone, which can be shown to represent a mass input sufficiently large to prevent corotation already at the source location. The source rate from Enceladus at Saturn has been reported to be an order of magnitude smaller (in absolute numbers than that from Io at Jupiter. Both reference values, however, are also smaller at Saturn than at Jupiter, by factors ~40 to 60; expressed in dimensionless form, the estimated mass input from Enceladus may be larger than that from Io by factors ~4 to 6. The magnetosphere of Saturn may thus, despite a lower mass input in kg s⁻¹, intrinsically be more heavily mass-loaded than the magnetosphere of Jupiter.

Comparing Jupiter and Saturn: dimensionless input rates from plasma sources within the magnetosphere

Directory of Open Access Journals (Sweden)

V. M. Vasyliūnas

2008-06-01

Full Text Available The quantitative significance for a planetary magnetosphere of plasma sources associated with a moon of the planet can be assessed only by expressing the plasma mass input rate in dimensionless form, as the ratio of the actual mass input to some reference value. Traditionally, the solar wind mass flux through an area equal to the cross-section of the magnetosphere has been used. Here I identify another reference value of mass input, independent of the solar wind and constructed from planetary parameters alone, which can be shown to represent a mass input sufficiently large to prevent corotation already at the source location. The source rate from Enceladus at Saturn has been reported to be an order of magnitude smaller (in absolute numbers than that from Io at Jupiter. Both reference values, however, are also smaller at Saturn than at Jupiter, by factors ~40 to 60; expressed in dimensionless form, the estimated mass input from Enceladus may be larger than that from Io by factors ~4 to 6. The magnetosphere of Saturn may thus, despite a lower mass input in kg s−1, intrinsically be more heavily mass-loaded than the magnetosphere of Jupiter.

Comments Simplification of thermodynamic calculations through dimensionless entropies

International Nuclear Information System (INIS)

Pitzer, K.S.; Brewer, L.

1979-01-01

The advantages of using thermodynamic quantities divided by the gas constant (H/R, G/R, etc,) in calculations are described. It is recommended that thermodynamic tables be presented in this form, so that the entries are either dimensionless or in units of kelvins

A dimensionless criterion for characterising internal transport barriers in tokamaks

International Nuclear Information System (INIS)

Tresset, G.; Litaudon, X.; Moreau, D.

2000-07-01

A simple criterion, based on a dimensionless parameter (ρ T * =ρ s /L T ) related to drift wave turbulence stabilisation and anomalous transport theory, is proposed in order to characterise the emergence and the space-time evolution of internal transport barriers (ITB's) during a tokamak discharge. The underlying physics which led us to consider the possible relevance of this parameter as a local indicator of a bifurcated plasma state is the breaking of the gyro-Bohm turbulence scaling by the diamagnetic velocity shear, which has been observed in various numerical simulations [e.g. X. Garbet and R.E. Waltz, Phys. Plasmas 3(1996) 1898]. The presence of an ITB is inferred when ρ T * exceeds a threshold value. The main features like the emergence time, location and even dynamics of ITB's can then be summarized on a single graphical representation consistent with measurement uncertainties. The validity of such a criterion is demonstrated on the Optimized Shear (OS) database of JET in several experimental configurations. Large database analysis and realtime control of OS discharges are envisaged as the most attractive applications. (author)

Dimensionless Analysis for Designing Domestic Rainwater Harvesting Systems at the Regional Level in Northern Taiwan

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Chao-Hsien Liaw

2014-12-01

Full Text Available A regional-level and dimensionless analysis for designing a domestic rainwater harvesting system (DRWHS was developed. To consider various combinations of water demand, storage capacity, effective roof area, and rainfall in DRWHS design, two dimensionless ratios were used, namely, demand fraction and storage fraction, along with a relationship between the two ratios. Firstly, Northern Taiwan was divided into four sub-regions through cluster analysis based on the average annual 10-day rainfall distribution at rainfall stations and administrative districts. Easy-to-use dimensionless curves between demand fraction and storage fraction were obtained for five rainwater supply reliabilities of the DRWHS for the four sub-regions. Based on the dimensionless curves, a nomogram was constructed for designing DRWHSs at a rainwater supply reliability of 95% in the sub-region I. Storage capacities determined from the dimensionless curves showed a close fit with those determined from simulated values, but were larger than the values estimated from the method presented in the Green Building Evaluation Manual in most situations. The methodology developed herein can be used effectively for the preliminary design of a DRWHS and for overcoming the difficulties faced in designing a DRWHS without rainfall data and with incomplete rainfall data.

The H-mode pedestal, ELMs and TF ripple effects in JT-60U/JET dimensionless identity experiments

International Nuclear Information System (INIS)

Saibene, G.; Oyama, N.; Loennroth, J.; Andrew, Y.; Luna, E. de la; Giroud, C.; Huysmans, G.T.A.; Kamada, Y.; Kempenaars, M.A.H.; Loarte, A.; Donald, D. Mc; Nave, M.M.F.; Meiggs, A.; Parail, V.; Sartori, R.; Sharapov, S.; Stober, J.; Suzuki, T.; Takechi, M.; Toi, K.; Urano, H.

2007-01-01

This paper summarizes results of dimensionless identity experiments in JT-60U and JET, aimed at the comparison of the H-mode pedestal and ELM behaviour in the two devices. Given their similar size, dimensionless matched plasmas are also similar in their dimensional parameters (in particular, the plasma minor radius a is the same in JET and JT-60U). Power and density scans were carried out at two values of I p , providing a q scan (q 95 = 3.1 and 5.1) with fixed (and matched) toroidal field. Contrary to initial expectations, a dimensionless match between the two devices was quite difficult to achieve. In general, p ped in JT-60U is lower than in JET and, at low q, the pedestal pressure of JT-60U with a Type I ELMy edge is matched in JET only in the Type III ELM regime. At q 95 = 5.1, a dimensionless match in ρ*, ν* and β p,ped is obtained with Type I ELMs, but only with low power JET H-modes. These results motivated a closer investigation of experimental conditions in the two devices, to identify possible 'hidden' physics that prevents obtaining a good match of pedestal values over a large range of plasmas parameters. Ripple-induced ion losses of the medium bore plasma used in JT-60U for the similarity experiments are identified as the main difference with JET. The magnitude of the JT-60U ripple losses is sufficient to induce counter-toroidal rotation in co-injected plasma. The influence of ripple losses was demonstrated at q 95 = 5.1: reducing ripple losses by ∼2 (from 4.3 to 1.9 MW) by replacing positive with negative neutral beam injection at approximately constant P in resulted in an increased p ped in JT-60U, providing a good match to full power JET H-modes. At the same time, the counter-toroidal rotation decreased. Physics mechanisms relating ripple losses to pedestal performance are not yet identified, and the possible role of velocity shear in the pedestal stability, as well as the possible influence of ripple on thermal ion transport are briefly

An equation for the dimensionless friction factor of consolidated ...

African Journals Online (AJOL)

An equation that relates the dimensionless friction factor of a porous medium its Reynolds number, during incompressible and compressible fluid flow through the medium is proposed. The equation is a curve fit of a graph drawn from the results of Ohirhian for water (liquid) and that of Akpokene for Nitrogen (gas) flow ...

Dosage-based parameters for characterization of puff dispersion results.

Science.gov (United States)

Berbekar, Eva; Harms, Frank; Leitl, Bernd

2015-01-01

A set of parameters is introduced to characterize the dispersion of puff releases based on the measured dosage. These parameters are the dosage, peak concentration, arrival time, peak time, leaving time, ascent time, descent time and duration. Dimensionless numbers for the scaling of the parameters are derived from dimensional analysis. The dimensionless numbers are tested and confirmed based on a statistically representative wind tunnel dataset. The measurements were carried out in a 1:300 scale model of the Central Business District in Oklahoma City. Additionally, the effect of the release duration on the puff parameters is investigated. Copyright © 2014 Elsevier B.V. All rights reserved.

Elastic orthorhombic anisotropic parameter inversion: An analysis of parameterization

KAUST Repository

Oh, Juwon

2016-09-15

The resolution of a multiparameter full-waveform inversion (FWI) is highly influenced by the parameterization used in the inversion algorithm, as well as the data quality and the sensitivity of the data to the elastic parameters because the scattering patterns of the partial derivative wavefields (PDWs) vary with parameterization. For this reason, it is important to identify an optimal parameterization for elastic orthorhombic FWI by analyzing the radiation patterns of the PDWs for many reasonable model parameterizations. We have promoted a parameterization that allows for the separation of the anisotropic properties in the radiation patterns. The central parameter of this parameterization is the horizontal P-wave velocity, with an isotropic scattering potential, influencing the data at all scales and directions. This parameterization decouples the influence of the scattering potential given by the P-wave velocity perturbation fromthe polar changes described by two dimensionless parameter perturbations and from the azimuthal variation given by three additional dimensionless parameters perturbations. In addition, the scattering potentials of the P-wave velocity perturbation are also decoupled from the elastic influences given by one S-wave velocity and two additional dimensionless parameter perturbations. The vertical S-wave velocity is chosen with the best resolution obtained from S-wave reflections and converted waves, little influence on P-waves in conventional surface seismic acquisition. The influence of the density on observed data can be absorbed by one anisotropic parameter that has a similar radiation pattern. The additional seven dimensionless parameters describe the polar and azimuth variations in the P- and S-waves that we may acquire, with some of the parameters having distinct influences on the recorded data on the earth\\'s surface. These characteristics of the new parameterization offer the potential for a multistage inversion from high symmetry

Elastic orthorhombic anisotropic parameter inversion: An analysis of parameterization

KAUST Repository

Oh, Juwon; Alkhalifah, Tariq Ali

2016-01-01

The resolution of a multiparameter full-waveform inversion (FWI) is highly influenced by the parameterization used in the inversion algorithm, as well as the data quality and the sensitivity of the data to the elastic parameters because the scattering patterns of the partial derivative wavefields (PDWs) vary with parameterization. For this reason, it is important to identify an optimal parameterization for elastic orthorhombic FWI by analyzing the radiation patterns of the PDWs for many reasonable model parameterizations. We have promoted a parameterization that allows for the separation of the anisotropic properties in the radiation patterns. The central parameter of this parameterization is the horizontal P-wave velocity, with an isotropic scattering potential, influencing the data at all scales and directions. This parameterization decouples the influence of the scattering potential given by the P-wave velocity perturbation fromthe polar changes described by two dimensionless parameter perturbations and from the azimuthal variation given by three additional dimensionless parameters perturbations. In addition, the scattering potentials of the P-wave velocity perturbation are also decoupled from the elastic influences given by one S-wave velocity and two additional dimensionless parameter perturbations. The vertical S-wave velocity is chosen with the best resolution obtained from S-wave reflections and converted waves, little influence on P-waves in conventional surface seismic acquisition. The influence of the density on observed data can be absorbed by one anisotropic parameter that has a similar radiation pattern. The additional seven dimensionless parameters describe the polar and azimuth variations in the P- and S-waves that we may acquire, with some of the parameters having distinct influences on the recorded data on the earth's surface. These characteristics of the new parameterization offer the potential for a multistage inversion from high symmetry

Theoretical investigation of the upper and lower bounds of a generalized dimensionless bearing health indicator

Science.gov (United States)

Wang, Dong; Tsui, Kwok-Leung

2018-01-01

Bearing-supported shafts are widely used in various machines. Due to harsh working environments, bearing performance degrades over time. To prevent unexpected bearing failures and accidents, bearing performance degradation assessment becomes an emerging topic in recent years. Bearing performance degradation assessment aims to evaluate the current health condition of a bearing through a bearing health indicator. In the past years, many signal processing and data mining based methods were proposed to construct bearing health indicators. However, the upper and lower bounds of these bearing health indicators were not theoretically calculated and they strongly depended on historical bearing data including normal and failure data. Besides, most health indicators are dimensional, which connotes that these health indicators are prone to be affected by varying operating conditions, such as varying speeds and loads. In this paper, based on the principle of squared envelope analysis, we focus on theoretical investigation of bearing performance degradation assessment in the case of additive Gaussian noises, including distribution establishment of squared envelope, construction of a generalized dimensionless bearing health indicator, and mathematical calculation of the upper and lower bounds of the generalized dimensionless bearing health indicator. Then, analyses of simulated and real bearing run to failure data are used as two case studies to illustrate how the generalized dimensionless health indicator works and demonstrate its effectiveness in bearing performance degradation assessment. Results show that squared envelope follows a noncentral chi-square distribution and the upper and lower bounds of the generalized dimensionless health indicator can be mathematically established. Moreover, the generalized dimensionless health indicator is sensitive to an incipient bearing defect in the process of bearing performance degradation.

Parameter estimation for an expanding universe

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Jieci Wang

2015-03-01

Full Text Available We study the parameter estimation for excitations of Dirac fields in the expanding Robertson–Walker universe. We employ quantum metrology techniques to demonstrate the possibility for high precision estimation for the volume rate of the expanding universe. We show that the optimal precision of the estimation depends sensitively on the dimensionless mass m˜ and dimensionless momentum k˜ of the Dirac particles. The optimal precision for the ratio estimation peaks at some finite dimensionless mass m˜ and momentum k˜. We find that the precision of the estimation can be improved by choosing the probe state as an eigenvector of the hamiltonian. This occurs because the largest quantum Fisher information is obtained by performing projective measurements implemented by the projectors onto the eigenvectors of specific probe states.

Mathematical modelling of nonstationary processes in a regenerator with dissociating coolant at supercritical parameters

International Nuclear Information System (INIS)

Tashchilova, Eh.M.; Sharovarov, G.A.

1985-01-01

The mathematical model of nonstationary processes in heat exchangers with dissociating coolant at supercritical parameters is given. Its dimensionless criteria are deveped. The effect of NPP regenerator parameters on criteria variation is determined. The proceeding nonstationary processes are estimated qualitatively using the dimensionless parameters. Dynamics of the processes in heat exchangers is described by the energy, mass and moment-of-momentum equations for heating and heated medium taking into account heat accumulation in the heat-transfer wall and distribution of parameters along the length of a heat exchanger

Can we calculate the fundamental dimensionless constants of physics

International Nuclear Information System (INIS)

Barut, A.O.

1987-07-01

We review some dynamical models to calculate the dimensionless constants α=e 2 /4πε 0 (h/2π)c, β=M p /m e (or β'=m μ /m e ), γ=G Fermi m e 2 /c(h/2π) 3 and δ=G Newton m e 2 /(e 2 /4πε 0 ) which are associated with the four different manifestations (electromagnetic, strong, weak and gravitational) of a possible single interaction. (author). 15 refs

Dimensionless Energy Conversion Characteristics of an Air-Powered Hydraulic Vehicle

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Dongkai Shen

2018-02-01

Full Text Available Due to the advantages of resource conservation and less exhaust emissions, compressed air-powered vehicle has attracted more and more attention. To improve the power and efficiency of air-powered vehicle, an air-powered hydraulic vehicle was proposed. As the main part of the air-powered hydraulic vehicles, HP transformer (short for Hydropneumatic transformer is used to convert the pneumatic power to higher hydraulic power. In this study, to illustrate the energy conversion characteristics of air-powered hydraulic vehicle, dimensionless mathematical model of the vehicle’s working process was set up. Through experimental study on the vehicle, the dimensionless model was verified. Through simulation study on the vehicle, the following can be obtained: firstly, the increase of the hydraulic chamber orifice and the area ratio of the pistons can lead to a higher output power, while output pressure is just the opposite. Moreover, the increase of the output pressure and the aperture of the hydraulic chamber can lead to a higher efficiency, while area ratio of the pistons played the opposite role. This research can be referred to in the performance and design optimization of the HP transformers.

Universal dependences between turbulent and mean flow parameters instably and neutrally stratified Planetary Boundary Layers

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I. N. Esau

2006-01-01

Full Text Available We consider the resistance law for the planetary boundary layer (PBL from the point of view of the similarity theory. In other words, we select the set of the PBL governing parameters and search for an optimal way to express through these parameters the geostrophic drag coefficient Cg=u* /Ug and the cross isobaric angle α (where u* is the friction velocity and Ug is the geostrophic wind speed. By this example, we demonstrate how to determine the 'parameter space' in the most convenient way, so that make independent the dimensionless numbers representing co-ordinates in the parameter space, and to avoid (or at least minimise artificial self-correlations caused by the appearance of the same factors (such as u* in the examined dimensionless combinations (e.g. in Cg=u* /Ug and in dimensionless numbers composed of the governing parameters. We also discuss the 'completeness' of the parameter space from the point of view of large-eddy simulation (LES modeller creating a database for a specific physical problem. As recognised recently, very large scatter of data in prior empirical dependencies of Cg and α on the surface Rossby number Ro=Ug| fz0|-1 (where z0 is the roughness length and the stratification characterised by µ was to a large extent caused by incompactness of the set of the governing parameters. The most important parameter overlooked in the traditional approach is the typical value of the Brunt-Väisälä frequency N in the free atmosphere (immediately above the PBL, which involves, besides Ro and µ, one more dimensionless number: µN=N/ | f |. Accordingly, we consider Cg and α as dependent on the three (rather then two basic dimensionless numbers (including µN using LES database DATABASE64. By these means we determine the form of the dependencies under consideration in the part of the parameter space representing typical atmospheric PBLs, and provide analytical expressions for Cg and α.

Dimensionless parameterization of lidar for laser remote sensing of the atmosphere and its application to systems with SiPM and PMT detectors.

Science.gov (United States)

Agishev, Ravil; Comerón, Adolfo; Rodriguez, Alejandro; Sicard, Michaël

2014-05-20

In this paper, we show a renewed approach to the generalized methodology for atmospheric lidar assessment, which uses the dimensionless parameterization as a core component. It is based on a series of our previous works where the problem of universal parameterization over many lidar technologies were described and analyzed from different points of view. The modernized dimensionless parameterization concept applied to relatively new silicon photomultiplier detectors (SiPMs) and traditional photomultiplier (PMT) detectors for remote-sensing instruments allowed predicting the lidar receiver performance with sky background available. The renewed approach can be widely used to evaluate a broad range of lidar system capabilities for a variety of lidar remote-sensing applications as well as to serve as a basis for selection of appropriate lidar system parameters for a specific application. Such a modernized methodology provides a generalized, uniform, and objective approach for evaluation of a broad range of lidar types and systems (aerosol, Raman, DIAL) operating on different targets (backscatter or topographic) and under intense sky background conditions. It can be used within the lidar community to compare different lidar instruments.

A Diagnosis Method for Rotation Machinery Faults Based on Dimensionless Indexes Combined with K-Nearest Neighbor Algorithm

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Jianbin Xiong

2015-01-01

Full Text Available It is difficult to well distinguish the dimensionless indexes between normal petrochemical rotating machinery equipment and those with complex faults. When the conflict of evidence is too big, it will result in uncertainty of diagnosis. This paper presents a diagnosis method for rotation machinery fault based on dimensionless indexes combined with K-nearest neighbor (KNN algorithm. This method uses a KNN algorithm and an evidence fusion theoretical formula to process fuzzy data, incomplete data, and accurate data. This method can transfer the signals from the petrochemical rotating machinery sensors to the reliability manners using dimensionless indexes and KNN algorithm. The input information is further integrated by an evidence synthesis formula to get the final data. The type of fault will be decided based on these data. The experimental results show that the proposed method can integrate data to provide a more reliable and reasonable result, thereby reducing the decision risk.

A dimensionless ordered pull-through model of the mammalian lens epithelium evidences scaling across species and explains the age-dependent changes in cell density in the human lens

Science.gov (United States)

Wu, Jun Jie; Wu, Weiju; Tholozan, Frederique M.; Saunter, Christopher D.; Girkin, John M.; Quinlan, Roy A.

2015-01-01

We present a mathematical (ordered pull-through; OPT) model of the cell-density profile for the mammalian lens epithelium together with new experimental data. The model is based upon dimensionless parameters, an important criterion for inter-species comparisons where lens sizes can vary greatly (e.g. bovine (approx. 18 mm); mouse (approx. 2 mm)) and confirms that mammalian lenses scale with size. The validated model includes two parameters: β/α, which is the ratio of the proliferation rate in the peripheral and in the central region of the lens; and γGZ, a dimensionless pull-through parameter that accounts for the cell transition and exit from the epithelium into the lens body. Best-fit values were determined for mouse, rat, rabbit, bovine and human lens epithelia. The OPT model accounts for the peak in cell density at the periphery of the lens epithelium, a region where cell proliferation is concentrated and reaches a maximum coincident with the germinative zone. The β/α ratio correlates with the measured FGF-2 gradient, a morphogen critical to lens cell survival, proliferation and differentiation. As proliferation declines with age, the OPT model predicted age-dependent changes in cell-density profiles, which we observed in mouse and human lenses. PMID:26236824

Experimental constraints on transport from dimensionless parameter scaling studies

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baker, D.R.; Ballet, B.; Carlstrom, T.N.; Cordey, J.G.; DeBoo, J.C.; Gohil, P.; Groebner, R.J.; Rice, B.W.; Thomas, D.M.; Wade, M.R.; Waltz, R.E.

1998-01-01

The scalings of heat transport with safety factor (q), normalized collisionality (ν), plasma beta (β), and relative gyroradius (ρ * ) have been measured on the DIII-D tokamak [Fusion Technol. 8, 441 (1985)]. The measured ρ * , β and ν scalings of heat transport indicate that ExB transport from drift wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like χ eff ∝q 2.3±0.64 , with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, τ th ∝q -2.42±0.31 ; however, when the magnetic shear was allowed to vary to keep q 0 fixed during the (edge) safety factor scan, a weaker global dependence was observed, τ th ∝q 95 -1.43±0.23 . This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined ρ * , β , ν and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (dimensional) parameters with the exception of weaker power degradation. copyright 1998 American Institute of Physics

Advanced control of liquid water region in diffusion media of polymer electrolyte fuel cells through a dimensionless number

Science.gov (United States)

Wang, Yun; Chen, Ken S.

2016-05-01

In the present work, a three-dimension (3-D) model of polymer electrolyte fuel cells (PEFCs) is employed to investigate the complex, non-isothermal, two-phase flow in the gas diffusion layer (GDL). Phase change in gas flow channels is explained, and a simplified approach accounting for phase change is incorporated into the fuel cell model. It is found that the liquid water contours in the GDL are similar along flow channels when the channels are subject to two-phase flow. Analysis is performed on a dimensionless parameter Da0 introduced in our previous paper [Y. Wang and K. S. Chen, Chemical Engineering Science 66 (2011) 3557-3567] and the parameter is further evaluated in a realistic fuel cell. We found that the GDL's liquid water (or liquid-free) region is determined by the Da0 number which lumps several parameters, including the thermal conductivity and operating temperature. By adjusting these factors, a liquid-free GDL zone can be created even though the channel stream is two-phase flow. Such a liquid-free zone is adjacent to the two-phase region, benefiting local water management, namely avoiding both severe flooding and dryness.

Simultaneous release of diclofenac sodium and papaverine hydrochloride from tablets and pellets using the flow-through cell apparatus described by dimensionless equations.

Science.gov (United States)

Kasperek, Regina

2011-01-01

The release of diclofenac sodium and papaverine hydrochloride from tablets and pellets using the flow-through cell apparatus was studied. The influence of excipients and of a size of the solid dosage forms on the amount of the released substances at the intervals of time using the different rates of flow of the dissolution medium was investigated. Physical parameters corresponding to the dissolution process as the mass transfer coefficient, the thickness of the boundary diffusion layer and the concentration of the saturated solution at this layer were calculated. The results of release were described by dimensionless equations.

Dimensionless numbers and correlating equations for the analysis of the membrane-gas diffusion electrode assembly in polymer electrolyte fuel cells

Science.gov (United States)

Gyenge, E. L.

The Quraishi-Fahidy method [Can. J. Chem. Eng. 59 (1981) 563] was employed to derive characteristic dimensionless numbers for the membrane-electrolyte, cathode catalyst layer and gas diffuser, respectively, based on the model presented by Bernardi and Verbrugge for polymer electrolyte fuel cells [AIChE J. 37 (1991) 1151]. Monomial correlations among dimensionless numbers were developed and tested against experimental and mathematical modeling results. Dimensionless numbers comparing the bulk and surface-convective ionic conductivities, the electric and viscous forces and the current density and the fixed surface charges, were employed to describe the membrane ohmic drop and its non-linear dependence on current density due to membrane dehydration. The analysis of the catalyst layer yielded electrode kinetic equivalents of the second Damköhler number and Thiele modulus, influencing the penetration depth of the oxygen reduction front based on the pseudohomogeneous film model. The correlating equations for the catalyst layer could describe in a general analytical form, all the possible electrode polarization scenarios such as electrode kinetic control coupled or not with ionic and/or oxygen mass transport limitation. For the gas diffusion-backing layer correlations are presented in terms of the Nusselt number for mass transfer in electrochemical systems. The dimensionless number-based correlating equations for the membrane electrode assembly (MEA) could provide a practical approach to quantify single-cell polarization results obtained under a variety of experimental conditions and to implement them in models of the fuel cell stack.

Dimensionless numbers and correlating equations for the analysis of the membrane-gas diffusion electrode assembly in polymer electrolyte fuel cells

Energy Technology Data Exchange (ETDEWEB)

Gyenge, E.L. [Department of Chemical and Biological Engineering, The University of British Columbia, 2216 Main Mall, Vancouver, BC (Canada V6T 1Z4)

2005-12-01

The Quraishi-Fahidy method [Can. J. Chem. Eng. 59 (1981) 563] was employed to derive characteristic dimensionless numbers for the membrane-electrolyte, cathode catalyst layer and gas diffuser, respectively, based on the model presented by Bernardi and Verbrugge for polymer electrolyte fuel cells [AIChE J. 37 (1991) 1151]. Monomial correlations among dimensionless numbers were developed and tested against experimental and mathematical modeling results. Dimensionless numbers comparing the bulk and surface-convective ionic conductivities, the electric and viscous forces and the current density and the fixed surface charges, were employed to describe the membrane ohmic drop and its non-linear dependence on current density due to membrane dehydration. The analysis of the catalyst layer yielded electrode kinetic equivalents of the second Damkohler number and Thiele modulus, influencing the penetration depth of the oxygen reduction front based on the pseudohomogeneous film model. The correlating equations for the catalyst layer could describe in a general analytical form, all the possible electrode polarization scenarios such as electrode kinetic control coupled or not with ionic and/or oxygen mass transport limitation. For the gas diffusion-backing layer correlations are presented in terms of the Nusselt number for mass transfer in electrochemical systems. The dimensionless number-based correlating equations for the membrane electrode assembly (MEA) could provide a practical approach to quantify single-cell polarization results obtained under a variety of experimental conditions and to implement them in models of the fuel cell stack. (author)

Homeostasis and Heterostasis: from Invariant to Dimensionless Numbers

Directory of Open Access Journals (Sweden)

BRUNO GÜNTHER

2003-01-01

Full Text Available In the present paper we have examined the applicability of dimensionless and invariant numbers (DN & IN to the analysis of the cardiovascular system of mammals, whose functions were measured at standard metabolic conditions. The calculated IN did not change when we compared these figures with those obtained in dogs while they were submitted to graded exercise on a treadmill. In both instances, rest and exercise, the constancy of the IN prevailed, in accordance with Cannon's principle of "homeostasis" (1929. On the contrary, when dogs were examined during a standardized hypovolemic shock, we observed a breakdown of the IN, and the resulting DN evolved as a reliable index of the condition of "heterostasis" as defined by H. Selye. The robustness of the homeostatic regulations is based on high-gain integral feedback mechanisms, while "heterostasis" could be associated with low-gain integral feedback processes, when organisms are submitted to unitary step disturbances or to changes of the set-point at the entrance of the feedback loop.

Performance analysis of pin fins with temperature dependent thermal parameters using the variation of parameters method

Directory of Open Access Journals (Sweden)

Cihat Arslantürk

2016-08-01

Full Text Available The performance of pin fins transferring heat by convection and radiation and having variable thermal conductivity, variable emissivity and variable heat transfer coefficient was investigated in the present paper. Nondimensionalizing the fin equation, the problem parameters which affect the fin performance were obtained. Dimensionless nonlinear fin equation was solved with the variation of parameters method, which is quite new in the solution of nonlinear heat transfer problems. The solution of variation of parameters method was compared with known analytical solutions and some numerical solution. The comparisons showed that the solutions are seen to be perfectly compatible. The effects of problem parameters were investigated on the heat transfer rate and fin efficiency and results were presented graphically.

Effects of soil-structure in high-rise buildings by means of dimensionless analysis and a simplified model

NARCIS (Netherlands)

Gómez, S.S.; Pruiksma, J.

2017-01-01

In this paper simplified expressions for assessing fundamental frequency and modal damping of high-rise buildings taking into account the soil-structure interaction (SSI) are proposed. To this end, several steps have been followed. First, a 3DoF model is formulated making use of dimensionless

Hovering efficiency comparison of rotary and flapping flight for a rigid and rectangular wings via dimensionless multi-objective optimization.

Science.gov (United States)

Bayiz, Yagiz Efe; Ghanaatpishe, Mohammad; Fathy, Hosam; Cheng, Bo

2018-03-20

In this work, a multi-objective optimization framework is developed for optimizing low-Reynolds number (Re) hovering flight. This framework is then applied to compare the efficiency of rigid revolving and flapping wings with rectangular shape under varying Re and Rossby number (Ro, or aspect ratio). The proposed framework is capable of generating sets of optimal solutions and Pareto fronts for maximizing lift coefficient and minimizing power coefficient in dimensionless space, which explicitly reveal the trade off between lift generation and power consumption. The results indicate that revolving wings are more efficient if the required average lift coefficient CL is low (< 1 for Re = 100 and < 1.6 for Re = 8000), while flapping wings are more efficient in achieving higher CL. Using dimensionless power loading as the single objective performance measure to be maximized, rotary flight is more efficient than flapping wings for Re > 100 regardless of the amount of energy storage assumed in the flapping-wing actuation mechanism, while flapping flight becomes more efficient for Re < 100. It is observed that wings with low Ro perform better if higher CL is needed, whereas higher Ro cases are more efficient at CL < 0.9 region. However, for the selected geometry and Re, the efficiency is weakly dependent on Ro if the dimensionless power loading is maximized. © 2018 IOP Publishing Ltd.

Error analysis of dimensionless scaling experiments with multiple points using linear regression

International Nuclear Information System (INIS)

Guercan, Oe.D.; Vermare, L.; Hennequin, P.; Bourdelle, C.

2010-01-01

A general method of error estimation in the case of multiple point dimensionless scaling experiments, using linear regression and standard error propagation, is proposed. The method reduces to the previous result of Cordey (2009 Nucl. Fusion 49 052001) in the case of a two-point scan. On the other hand, if the points follow a linear trend, it explains how the estimated error decreases as more points are added to the scan. Based on the analytical expression that is derived, it is argued that for a low number of points, adding points to the ends of the scanned range, rather than the middle, results in a smaller error estimate. (letter)

Multi-objective optimization and design for free piston Stirling engines based on the dimensionless power

Science.gov (United States)

Mou, Jian; Hong, Guotong

2017-02-01

In this paper, the dimensionless power is used to optimize the free piston Stirling engines (FPSE). The dimensionless power is defined as a ratio of the heat power loss and the output work. The heat power losses include the losses of expansion space, heater, regenerator, cooler and the compression space and every kind of the heat loss calculated by empirical formula. The output work is calculated by the adiabatic model. The results show that 82.66% of the losses come from the expansion space and 54.59% heat losses of expansion space come from the shuttle loss. At different pressure the optimum bore-stroke ratio, heat source temperature, phase angle and the frequency have different values, the optimum phase angles increase with the increase of pressure, but optimum frequencies drop with the increase of pressure. However, no matter what the heat source temperature, initial pressure and frequency are, the optimum ratios of piston stroke and displacer stroke all about 0.8. The three-dimensional diagram is used to analyse Stirling engine. From the three-dimensional diagram the optimum phase angle, frequency and heat source temperature can be acquired at the same time. This study offers some guides for the design and optimization of FPSEs.

Effect of Surface Texturing Parameters on the Lubrication Characteristics of an Axial Piston Pump Valve Plate

Directory of Open Access Journals (Sweden)

Zhaoqiang Wang

2018-05-01

Full Text Available In this article, a geometrical model of different microtextures is established for an axial piston pump valve plate. A finite differential method was used to solve the Reynolds equation for the oil film thickness and pressure, which were simulated under different microtextures. The influence of microtexture shape and structure on performance was studied and optimal parameters sought. Different convergence gaps are formed by different microtexture radii, and they produce different hydrodynamic effects. The lubrication characteristics of the valve plate are better when a microtexture is used and are influenced by the type of microtexture. We reached the following conclusions: (1 The lubrication characteristics of the valve plate are influenced by different microtexture parameters and can be improved by optimizing the microtexture parameters; (2 There is an optimal parameter combination when adding microtexture with three shapes (spherical, cylindrical and square and the optimal dimensionless oil film pressure lubrication characteristics can be obtained; (3 The degree of improvement in the dimensionless oil film pressure lubrication characteristics was (listed from highest to lowest: micro-hemispherical texture > micro-cylindrical texture > micro-square texture.

Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

Directory of Open Access Journals (Sweden)

Yongfang Huang

2017-04-01

Full Text Available For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ and pit depth (d with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively.

Study on TVD parameters sensitivity of a crankshaft using multiple scale and state space method considering quadratic and cubic non-linearities

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R. Talebitooti

Full Text Available In this paper the effect of quadratic and cubic non-linearities of the system consisting of the crankshaft and torsional vibration damper (TVD is taken into account. TVD consists of non-linear elastomer material used for controlling the torsional vibration of crankshaft. The method of multiple scales is used to solve the governing equations of the system. Meanwhile, the frequency response of the system for both harmonic and sub-harmonic resonances is extracted. In addition, the effects of detuning parameters and other dimensionless parameters for a case of harmonic resonance are investigated. Moreover, the external forces including both inertia and gas forces are simultaneously applied into the model. Finally, in order to study the effectiveness of the parameters, the dimensionless governing equations of the system are solved, considering the state space method. Then, the effects of the torsional damper as well as all corresponding parameters of the system are discussed.

Unravelling abiotic and biotic controls on the seasonal water balance using data-driven dimensionless diagnostics

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S. P. Seibert

2017-06-01

Full Text Available The baffling diversity of runoff generation processes, alongside our sketchy understanding of how physiographic characteristics control fundamental hydrological functions of water collection, storage, and release, continue to pose major research challenges in catchment hydrology. Here, we propose innovative data-driven diagnostic signatures for overcoming the prevailing status quo in catchment inter-comparison. More specifically, we present dimensionless double mass curves (dDMC which allow inference of information on runoff generation and the water balance at the seasonal and annual timescales. By separating the vegetation and winter periods, dDMC furthermore provide information on the role of biotic and abiotic controls in seasonal runoff formation. A key aspect we address in this paper is the derivation of dimensionless expressions of fluxes which ensure the comparability of the signatures in space and time. We achieve this by using the limiting factors of a hydrological process as a scaling reference. We show that different references result in different diagnostics. As such we define two kinds of dDMC which allow us to derive seasonal runoff coefficients and to characterize dimensionless streamflow release as a function of the potential renewal rate of the soil storage. We expect these signatures for storage controlled seasonal runoff formation to remain invariant, as long as the ratios of release over supply and supply over storage capacity develop similarly in different catchments. We test the proposed methods by applying them to an operational data set comprising 22 catchments (12–166 km2 from different environments in southern Germany and hydrometeorological data from 4 hydrological years. The diagnostics are used to compare the sites and to reveal the dominant controls on runoff formation. The key findings are that dDMC are meaningful signatures for catchment runoff formation at the seasonal to annual scale and that the type of

THE DIMENSIONLESS AGE OF THE UNIVERSE: A RIDDLE FOR OUR TIME

Energy Technology Data Exchange (ETDEWEB)

Avelino, Arturo; Kirshner, Robert P., E-mail: aavelino@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts, 02138 (United States)

2016-09-01

We present the interesting coincidence of cosmology and astrophysics that points toward a dimensionless age of the Universe H {sub 0} t {sub 0} that is close to one. Despite cosmic deceleration for 9 Gyr and acceleration since then, we find H {sub 0} t {sub 0} = 0.96 ± 0.01 for the ΛCDM model that fits SN Ia data from Pan-STARRS, CMB power spectra, and baryon acoustic oscillations. Similarly, astrophysical measures of stellar ages and the Hubble constant derived from redshifts and distances point to H {sub 0} t ∼ 1.0 ± 0.1. The wide range of possible values for H {sub 0} t {sub 0} realized during cosmic evolution means that we live at what appears to be a special time. This “synchronicity problem” is not precisely the same as the usual coincidence problem , because there are combinations of Ω{sub M} and Ω{sub Λ} for which the usual coincidence problem holds but for which H {sub 0} t {sub 0} is not close to 1.

Parameter-Independent Dynamical Behaviors in Memristor-Based Wien-Bridge Oscillator

Directory of Open Access Journals (Sweden)

Ning Wang

2017-01-01

Full Text Available This paper presents a novel memristor-based Wien-bridge oscillator and investigates its parameter-independent dynamical behaviors. The newly proposed memristive chaotic oscillator is constructed by linearly coupling a nonlinear active filter composed of memristor and capacitor to a Wien-bridge oscillator. For a set of circuit parameters, phase portraits of a double-scroll chaotic attractor are obtained by numerical simulations and then validated by hardware experiments. With a dimensionless system model and the determined system parameters, the initial condition-dependent dynamical behaviors are explored through bifurcation diagrams, Lyapunov exponents, and phase portraits, upon which the coexisting infinitely many attractors and transient chaos related to initial conditions are perfectly offered. These results are well verified by PSIM circuit simulations.

Dimensionless scalings of confinement, heat transport and pedestal stability in JET-ILW and comparison with JET-C

Czech Academy of Sciences Publication Activity Database

Frassinetti, L.; Saarelma, S.; Lomas, P.; Nunes, I.; Rimini, F.; Beurskens, M.N.A.; Bílková, Petra; Boom, J.E.; De La Luna, E.; Delabie, E.; Drewelow, P.; Flanagan, J.; Garzotti, L.; Giroud, C.; Hawks, N.; Joffrin, E.; Kempenaars, M.; Kim, H.-T.; Kruezi, U.; Loarte, A.; Lomanowski, B.; Lupelli, I.; Meneses, L.; Maggi, C.F.; Menmuir, S.; Peterka, Matěj; Rachlew, E.; Romanelli, M.; Stefanikova, E.

2017-01-01

Roč. 59, č. 1 (2017), č. článku 014014. ISSN 0741-3335. [EPS 2016: Conference on Plasma Physics/43./. Leuven, 04.07.2016-08.07.2016] EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : JET-ILW * dimensionless scaling * pedestal * confinement * pedestal stability * heat transport Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016 http://dx.doi.org/10.1088/0741-3335/59/1/014014

Irreversibility analysis of non isothermal flat plate solar collectors for air heating with a dimensionless model; Analisis de las irreversibilidades en colectores solares de placas planas no isotermicos para calentamiento de aire utilizando un modelo adimensional

Energy Technology Data Exchange (ETDEWEB)

Bracamonte-Baran, Johane Hans; Baritto-Loreto, Miguel Leonardo [Universidad Central de Venezuela (Venezuela)]. E-mails: johanehb@gmail.com; johane.bracamonte@ucv.ve; miguel.baritto@ucv.ve

2013-04-15

The dimensionless model developed and validated by Baritto and Bracamonte (2012) for the thermal behavior of flat plate solar collector without glass cover is improved by adding the entropy balance equation in a dimensionless form. The model is solved for a wide range of aspect ratios and mass flow numbers. A parametric study is developed and the distribution of internal irreversibilities along the collector is analyzed. The influence of the design parameters on the entropy generation by fluid friction and heat transfer is analyzed and it is found that for certain combinations of these parameters optimal thermodynamic operation can be achieved. [Spanish] En el presente trabajo, el modelo adimensional desarrollado y validado por Baritto y Bracamonte (2012) para describir el comportamiento termico de colectores solares de placas planas sin cubierta transparente, se complementa con la ecuacion adimensional de balance de entropia para un elemento diferencial de colector solar. El modelo se resuelve para un amplio rango de valores de relaciones de aspecto y numero de flujo de masa. A partir de los resultados del modelo se desarrolla un analisis detallado de la influencia de estos parametros sobre la distribucion de irreversibilidades internas a lo largo del colector. Adicionalmente se estudia la influencia de estos parametros sobre los numeros de generacion de entropia por friccion viscosa, por transferencia de calor y total. Se encuentra que existen combinaciones de los parametros antes mencionados, para los cuales, la operacion del colector es termodinamicamente optima para numeros de flujo de masa elevados.

Predictions of the marviken subcooled critical mass flux using the critical flow scaling parameters

Energy Technology Data Exchange (ETDEWEB)

Park, Choon Kyung; Chun, Se Young; Cho, Seok; Yang, Sun Ku; Chung, Moon Ki [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

A total of 386 critical flow data points from 19 runs of 27 runs in the Marviken Test were selected and compared with the predictions by the correlations based on the critical flow scaling parameters. The results show that the critical mass flux in the very large diameter pipe can be also characterized by two scaling parameters such as discharge coefficient and dimensionless subcooling (C{sub d,ref} and {Delta}{Tau}{sup *} {sub sub}). The agreement between the measured data and the predictions are excellent. 8 refs., 8 figs. 1 tab. (Author)

Predictions of the marviken subcooled critical mass flux using the critical flow scaling parameters

Energy Technology Data Exchange (ETDEWEB)

Park, Choon Kyung; Chun, Se Young; Cho, Seok; Yang, Sun Ku; Chung, Moon Ki [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1997-12-31

A total of 386 critical flow data points from 19 runs of 27 runs in the Marviken Test were selected and compared with the predictions by the correlations based on the critical flow scaling parameters. The results show that the critical mass flux in the very large diameter pipe can be also characterized by two scaling parameters such as discharge coefficient and dimensionless subcooling (C{sub d,ref} and {Delta}{Tau}{sup *} {sub sub}). The agreement between the measured data and the predictions are excellent. 8 refs., 8 figs. 1 tab. (Author)

Technical characterization of dialysis fluid flow and mass transfer rate in dialyzers with various filtration coefficients using dimensionless correlation equation.

Science.gov (United States)

Fukuda, Makoto; Yoshimura, Kengo; Namekawa, Koki; Sakai, Kiyotaka

2017-06-01

The objective of the present study is to evaluate the effect of filtration coefficient and internal filtration on dialysis fluid flow and mass transfer coefficient in dialyzers using dimensionless mass transfer correlation equations. Aqueous solution of vitamin B 12 clearances were obtained for REXEED-15L as a low flux dialyzer, and APS-15EA and APS-15UA as high flux dialyzers. All the other design specifications were identical for these dialyzers except for filtration coefficient. The overall mass transfer coefficient was calculated, moreover, the exponents of Reynolds number (Re) and film mass transfer coefficient of the dialysis-side fluid (k D ) for each flow rate were derived from the Wilson plot and dimensionless correlation equation. The exponents of Re were 0.4 for the low flux dialyzer whereas 0.5 for the high flux dialyzers. Dialysis fluid of the low flux dialyzer was close to laminar flow because of its low filtration coefficient. On the other hand, dialysis fluid of the high flux dialyzers was assumed to be orthogonal flow. Higher filtration coefficient was associated with higher k D influenced by mass transfer rate through diffusion and internal filtration. Higher filtration coefficient of dialyzers and internal filtration affect orthogonal flow of dialysis fluid.

Discovering Hidden Controlling Parameters using Data Analytics and Dimensional Analysis

Science.gov (United States)

Del Rosario, Zachary; Lee, Minyong; Iaccarino, Gianluca

2017-11-01

Dimensional Analysis is a powerful tool, one which takes a priori information and produces important simplifications. However, if this a priori information - the list of relevant parameters - is missing a relevant quantity, then the conclusions from Dimensional Analysis will be incorrect. In this work, we present novel conclusions in Dimensional Analysis, which provide a means to detect this failure mode of missing or hidden parameters. These results are based on a restated form of the Buckingham Pi theorem that reveals a ridge function structure underlying all dimensionless physical laws. We leverage this structure by constructing a hypothesis test based on sufficient dimension reduction, allowing for an experimental data-driven detection of hidden parameters. Both theory and examples will be presented, using classical turbulent pipe flow as the working example. Keywords: experimental techniques, dimensional analysis, lurking variables, hidden parameters, buckingham pi, data analysis. First author supported by the NSF GRFP under Grant Number DGE-114747.

PHOTOSPHERE EMISSION FROM A HYBRID RELATIVISTIC OUTFLOW WITH ARBITRARY DIMENSIONLESS ENTROPY AND MAGNETIZATION IN GRBs

Energy Technology Data Exchange (ETDEWEB)

Gao, He [Current address: Department of Astronomy and Astrophysics, Department of Physics, Center for Particle Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Zhang, Bing, E-mail: gaohe@physics.unlv.edu, E-mail: zhang@physics.unlv.edu, E-mail: hug18@psu.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

2015-03-10

In view of the recent Fermi observations of gamma-ray burst (GRB) prompt emission spectra, we develop a theory of photosphere emission of a hybrid relativistic outflow with a hot fireball component (defined by dimensionless entropy η) and a cold Poynting-flux component (defined by magnetization σ{sub 0} at the central engine). We consider the scenarios both without and with sub-photospheric magnetic dissipations. Based on a simplified toy model of jet dynamics, we develop two approaches: a 'bottom-up' approach to predict the temperature (for a non-dissipative photosphere) and luminosity of the photosphere emission and its relative brightness for a given pair of (η, σ{sub 0}); and a 'top-down' approach to diagnose central engine parameters (η and σ{sub 0}) based on the observed quasi-thermal photosphere emission properties. We show that a variety of observed GRB prompt emission spectra with different degrees of photosphere thermal emission can be reproduced by varying η and σ{sub 0} within the non-dissipative photosphere scenario. In order to reproduce the observed spectra, the outflows of most GRBs need to have a significant σ, both at the central engine and at the photosphere. The σ value at 10{sup 15} cm from the central engine (a possible non-thermal emission site) is usually also greater than unity, so that internal-collision-induced magnetic reconnection and turbulence (ICMART) may be the mechanism to power the non-thermal emission. We apply our top-down approach to GRB 110721A and find that the temporal evolution behavior of its blackbody component can be well interpreted with a time-varying (η, σ{sub 0}) at the central engine, instead of invoking a varying engine base size r {sub 0} as proposed by previous authors.

Dimensionless model to determine spontaneous combustion danger zone in the longwall gob

Institute of Scientific and Technical Information of China (English)

ZHANG Xin-hai; DENG Jun; WEN Hu

2011-01-01

According to spontaneous combustion propensity,the longwall gob is divided into three zones,including heat dissipation zone,self-heating zone and the choking zone.Only in the self-heating zone can temperature of coal rise due to oxidation.Studying the distribution of the “Three Zones” in gob is important for predicting and preventing spontaneous combustion in coalmine.In normal mining operations,temperature of coal is roughly constant.The process of mass transfer in the gob is considered to be steady.Based on mass conservation,gas species conservation,darcy' s law,Ficks law of diffusion and coal oxidation 1-grade reaction rule,governing equation for air leakage intensity and species concentration are deduced.With critical value of coal spontaneous combustion and the size of longwall workface as basic dimension,a dimensionless steady coupled model of air flow diffusion and chemical reaction in loose coal of Fully Mechanized Top-Coal Caving Mining Workface (FMTCCMW) is setup.By solving the model numerically,regulation of three zones' distribution and spontaneous combustion in the gob can be obtained.The results can be easily popularized to prediction of spontaneous combustion in other coalmines' longwall gob.

On the use of the fictitious wave steepness and related surf-similarity parameters in methods that describe the hydraulic and structural response to waves

NARCIS (Netherlands)

Heineke, D.; Verhagen, H.J.

2007-01-01

To assess the hydraulic performance of coastal structures - viz. wave run-up, overtopping and reflection - and to evaluate the stability of the armour layers, use is made of the dimensionless surf similarity parameter, as introduced by Battjes (1974). The front side slope of the structure and the

Estimation of gloss from rough surface parameters

Science.gov (United States)

Simonsen, Ingve; Larsen, Åge G.; Andreassen, Erik; Ommundsen, Espen; Nord-Varhaug, Katrin

2005-12-01

Gloss is a quantity used in the optical industry to quantify and categorize materials according to how well they scatter light specularly. With the aid of phase perturbation theory, we derive an approximate expression for this quantity for a one-dimensional randomly rough surface. It is demonstrated that gloss depends in an exponential way on two dimensionless quantities that are associated with the surface randomness: the root-mean-square roughness times the perpendicular momentum transfer for the specular direction, and a correlation function dependent factor times a lateral momentum variable associated with the collection angle. Rigorous Monte Carlo simulations are used to access the quality of this approximation, and good agreement is observed over large regions of parameter space.

Dimensionless Numerical Approaches for the Performance Prediction of Marine Waterjet Propulsion Units

Directory of Open Access Journals (Sweden)

Marco Altosole

2012-01-01

Full Text Available One of the key issues at early design stage of a high-speed craft is the selection and the performance prediction of the propulsion system because at this stage only few information about the vessel are available. The objective of this work is precisely to provide the designer, in the case of waterjet propelled craft, with a simple and reliable calculation tool, able to predict the waterjet working points in design and off-design conditions, allowing to investigate several propulsive options during the ship design process. In the paper two original dimensionless numerical procedures, one referred to jet units for naval applications and the other more suitable for planing boats, are presented. The first procedure is based on a generalized performance map for mixed flow pumps, derived from the analysis of several waterjet pumps by applying similitude principles of the hydraulic machines. The second approach, validated by some comparisons with current waterjet installations, is based on a complete physical approach, from which a set of non-dimensional waterjet characteristics has been drawn by the authors. The presented application examples show the validity and the degree of accuracy of the proposed methodologies for the performance evaluation of waterjet propulsion systems.

Simultaneous measurement of 3 fluctuating plasma parameters

International Nuclear Information System (INIS)

Carlson, A.; Giannone, L.

1991-01-01

Langmuir triple probes can provide simultaneous measurements of n e , T e and V pl with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (author) 1 fig

Simultaneous measurement of 3 fluctuating plasma parameters

International Nuclear Information System (INIS)

Carlson, A.; Giannone, L.

1991-01-01

Langmuir triple probes can provide simultaneous measurements of n e , T e , and V pl with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (orig.)

Simultaneous measurement of 3 fluctuating plasma parameters

Energy Technology Data Exchange (ETDEWEB)

Carlson, A; Giannone, L. (Max-Planck-Institut fuer Plasmaphysik, Garching (Germany))

1991-01-01

Langmuir triple probes can provide simultaneous measurements of n[sub e], T[sub e] and V[sub pl] with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (author) 1 fig.

A new dimensionless number highlighted from mechanical energy exchange during running.

Science.gov (United States)

Delattre, Nicolas; Moretto, Pierre

2008-09-18

This study aimed to highlight a new dimensionless number from mechanical energy transfer occurring at the centre of gravity (Cg) during running. We built two different-sized spring-mass models (SMM #1 and SMM #2). SMM #1 was built from the previously published data, and SMM #2 was built to be dynamically similar to SMM #1. The potential gravitational energy (E(P)), kinetic energy (E(K)), and potential elastic energy (E(E)) were taken into account to test our hypothesis. For both SMM #1 and SMM #2, N(Mo-Dela)=(E(P)+E(K))/E(E) reached the same mean value and was constant (4.1+/-0.7) between 30% and 70% of contact time. Values of N(Mo-Dela) obtained out of this time interval were due to the absence of E(E) at initial and final times of the simulation. This phenomenon does not occur during in vivo running because a leg muscle's pre-activation enables potential elastic energy storage prior to ground contact. Our findings also revealed that two different-sized spring-mass models bouncing with equal N(Mo-Dela) values moved in a dynamically similar fashion. N(Mo-Dela), which can be expressed by the combination of Strouhal and Froude numbers, could be of great interest in order to study animal and human locomotion under Earth's gravity or to induce dynamic similarity between different-sized individuals during bouncing gaits.

Parametric study on single shot peening by dimensional analysis method incorporated with finite element method

Science.gov (United States)

Wu, Xian-Qian; Wang, Xi; Wei, Yan-Peng; Song, Hong-Wei; Huang, Chen-Guang

2012-06-01

Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and resistance to corrosion fatigue, cracking, etc. Compressive residual stress and dent profile are important factors to evaluate the effectiveness of shot peening process. In this paper, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimensionless relations of processing parameters that affect the maximum compressive residual stress and the maximum depth of the dent were deduced by dimensional analysis method. Secondly, the influence of each dimensionless parameter on dimensionless variables was investigated by the finite element method. Furthermore, related empirical formulas were given for each dimensionless parameter based on the simulation results. Finally, comparison was made and good agreement was found between the simulation results and the empirical formula, which shows that a useful approach is provided in this paper for analyzing the influence of each individual parameter.

Determination of kinetic parameters of heterogeneous isotopic exchange reaction

International Nuclear Information System (INIS)

Huang, Ting-Chia; Tsai, Fuan-Nan

1977-01-01

A mathematical model has been proposed for a heterogeneous isotopic exchange reaction which involves film diffusion, surface chemical reaction and intraparticle diffusion. The exchange equation to predict the exchange fraction as a function of time for the spherical particles immersed in a solution of finite volume has been derived. The relations between the exchange fraction and dimensionless time are plotted with xi(=ak sub(f)/KD sub(e)), xi 1 (=K 1 a 2 /D sub(e)) and final fractional uptake as parameters. From the values of the kinetic parameters xi and xi 1 , the relative importance of each limiting step is discussed. Experimental results of the isotopic exchange reaction of calcium ion in both system CaCO 3 (s)/Ca 2+ (aq) and system calcium type resin Dowex 50W-X8/Ca 2+ (aq) are coincident with the theoretical equation proposed in this study. (auth.)

STUDY OF POND WATER QUALITY BY THE ASSESSMENT OF PHYSICOCHEMICAL PARAMETERS AND WATER QUALITY INDEX

OpenAIRE

Vinod Jena; Satish Dixit; Ravi ShrivastavaSapana Gupta; Sapana Gupta

2013-01-01

Water quality index (WQI) is a dimensionless number that combines multiple water quality factors into a single number by normalizing values to subjective rating curves. Conventionally it has been used for evaluating the quality of water for water resources suchas rivers, streams and lakes, etc. The present work is aimed at assessing the Water Quality Index (W.Q.I) ofpond water and the impact of human activities on it. Physicochemical parameters were monitored for the calculation of W.Q.I for ...

Quantifying the effects of ecological constraints on trait expression using novel trait-gradient analysis parameters.

Science.gov (United States)

Ottaviani, Gianluigi; Tsakalos, James L; Keppel, Gunnar; Mucina, Ladislav

2018-01-01

Complex processes related to biotic and abiotic forces can impose limitations to assembly and composition of plant communities. Quantifying the effects of these constraints on plant functional traits across environmental gradients, and among communities, remains challenging. We define ecological constraint ( C i ) as the combined, limiting effect of biotic interactions and environmental filtering on trait expression (i.e., the mean value and range of functional traits). Here, we propose a set of novel parameters to quantify this constraint by extending the trait-gradient analysis (TGA) methodology. The key parameter is ecological constraint, which is dimensionless and can be measured at various scales, for example, on population and community levels. It facilitates comparing the effects of ecological constraints on trait expressions across environmental gradients, as well as within and among communities. We illustrate the implementation of the proposed parameters using the bark thickness of 14 woody species along an aridity gradient on granite outcrops in southwestern Australia. We found a positive correlation between increasing environmental stress and strength of ecological constraint on bark thickness expression. Also, plants from more stressful habitats (shrublands on shallow soils and in sun-exposed locations) displayed higher ecological constraint for bark thickness than plants in more benign habitats (woodlands on deep soils and in sheltered locations). The relative ease of calculation and dimensionless nature of C i allow it to be readily implemented at various scales and make it widely applicable. It therefore has the potential to advance the mechanistic understanding of the ecological processes shaping trait expression. Some future applications of the new parameters could be investigating the patterns of ecological constraints (1) among communities from different regions, (2) on different traits across similar environmental gradients, and (3) for the same

Subtidal hydrodynamics in a tropical lagoon: A dimensionless numbers approach

Science.gov (United States)

Tenorio-Fernandez, L.; Valle-Levinson, A.; Gomez-Valdes, J.

2018-01-01

Observations in a tropical lagoon of the Yucatan peninsula motivated a non-dimensional number analysis to examine the relative influence of tidal stress, density gradients and wind stress on subtidal hydrodynamics. A two-month observation period in Chelem Lagoon covered the transition from the dry to the wet season. Chelem Lagoon is influenced by groundwater inputs and exhibits a main sub-basin (central sub-basin), a west sub-basin and an east sub-basin. Subtidal hydrodynamics were associated with horizontal density gradients that were modified seasonally by evaporation, precipitation, and groundwater discharge. A tidal Froude number (Fr0), a Wedderburn number (W), and a Stress ratio (S0) were used to diagnose the relative importance of dominant subtidal driving forces. The Froude number (Fr0) compares tidal forcing and baroclinic forcing through the ratio of tidal stress to longitudinal baroclinic pressure gradient. The Wedderburn number (W) relates wind stress to baroclinicity. The stress ratio (S0) sizes tidal stress and wind stress. S0 is a new diagnostic tool for systems influenced by tides and winds, and represents the main contribution of this research. Results show that spring-tide subtidal flows in the tropical lagoon had log(Fr0) ≫ 0 and log(S0) > 0 , i.e., driven mainly by tidal stresses (advective accelerations). Neap tides showed log(Fr0) ≪ 0 and log(S0) < 0) , i.e., flows driven by baroclinicity, especially at the lagoon heads of the east and west sub-basins. However, when the wind stress intensified over the lagoon, the relative importance of baroclinicity decreased and the wind stress controlled the dynamics (log(W) ≫ 0). Each sub-basin exhibited a different subtidal response, according to the dimensionless numbers. The response depended on the fortnightly tidal cycle, the location and magnitude of groundwater input, and the direction and magnitude of the wind stress.

Waveform inversion in acoustic orthorhombic media with a practical set of parameters

KAUST Repository

Masmoudi, Nabil; Alkhalifah, Tariq Ali

2017-01-01

Full-waveform inversion (FWI) in anisotropic media is overall challenging, mainly because of the large computational cost, especially in 3D, and the potential trade-offs between the model parameters needed to describe such a media. We propose an efficient 3D FWI implementation for orthorhombic anisotropy under the acoustic assumption. Our modeling is based on solving the pseudo-differential orthorhombic wave equation split into a differential operator and a scalar one. The modeling is computationally efficient and free of shear wave artifacts. Using the adjoint state method, we derive the gradients with respect to a practical set of parameters describing the acoustic orthorhombic model, made of one velocity and five dimensionless parameters. This parameterization allows us to use a multi-stage model inversion strategy based on the continuity of the scattering potential of the parameters as we go from higher symmetry anisotropy to lower ones. We apply the proposed approach on a modified SEG-EAGE overthrust synthetic model. The quality of the inverted model suggest that we may recover only 4 parameters, with different resolution scales depending on the scattering potential of these parameters.

Waveform inversion in acoustic orthorhombic media with a practical set of parameters

KAUST Repository

Masmoudi, Nabil

2017-08-17

Full-waveform inversion (FWI) in anisotropic media is overall challenging, mainly because of the large computational cost, especially in 3D, and the potential trade-offs between the model parameters needed to describe such a media. We propose an efficient 3D FWI implementation for orthorhombic anisotropy under the acoustic assumption. Our modeling is based on solving the pseudo-differential orthorhombic wave equation split into a differential operator and a scalar one. The modeling is computationally efficient and free of shear wave artifacts. Using the adjoint state method, we derive the gradients with respect to a practical set of parameters describing the acoustic orthorhombic model, made of one velocity and five dimensionless parameters. This parameterization allows us to use a multi-stage model inversion strategy based on the continuity of the scattering potential of the parameters as we go from higher symmetry anisotropy to lower ones. We apply the proposed approach on a modified SEG-EAGE overthrust synthetic model. The quality of the inverted model suggest that we may recover only 4 parameters, with different resolution scales depending on the scattering potential of these parameters.

Gaussian beam profile shaping apparatus, method therefore and evaluation thereof

International Nuclear Information System (INIS)

Dickey, F.M.; Holswade, S.C.; Romero, L.A.

1999-01-01

A method and apparatus maps a Gaussian beam into a beam with a uniform irradiance profile by exploiting the Fourier transform properties of lenses. A phase element imparts a design phase onto an input beam and the output optical field from a lens is then the Fourier transform of the input beam and the phase function from the phase element. The phase element is selected in accordance with a dimensionless parameter which is dependent upon the radius of the incoming beam, the desired spot shape, the focal length of the lens and the wavelength of the input beam. This dimensionless parameter can also be used to evaluate the quality of a system. In order to control the radius of the incoming beam, optics such as a telescope can be employed. The size of the target spot and the focal length can be altered by exchanging the transform lens, but the dimensionless parameter will remain the same. The quality of the system, and hence the value of the dimensionless parameter, can be altered by exchanging the phase element. The dimensionless parameter provides design guidance, system evaluation, and indication as to how to improve a given system. 27 figs

One-dimensional model of steady, compressible channel flow with mass, momentum, and energy addition

International Nuclear Information System (INIS)

Johnston, S.C.

1976-09-01

A one-dimensional model of steady, compressible channel flow with mass, momentum and energy addition is discussed. An exact solution to the governing equations was found and from it a similarity parameter relating dimensionless mass, momentum and energy addition identified. This similarity parameter is used to make two flows having different dimensionless mass, momentum and energy additions equivalent. Application of the similarity parameter to the LASL Intense Neutron Source experiment and the Sandia simulation of that experiment results in an expression relating the dimensionless mass addition of combustible gas required in the Sandia experiment to dimensionless energy addition in the LASL experiment. Results of the analysis indicate that the Sandia experiment can realistically simulate the energy addition in the LASL Intense Neutron Source experiment

Weighting factor for instantaneous source functions of a permeable ...

African Journals Online (AJOL)

A multiplicative weighting factor, E, is obtained which shows constant behaviour at late dimensionless flow times for a particular set of well and reservoir dimensionless parameters. Computation of dimensionless pressures using the factor shows conformity with expected behaviour for a layered reservoir with crossflow ...

Damage Evaluation of Critical Components of Tilted Support Spring Nonlinear System under a Rectangular Pulse

Directory of Open Access Journals (Sweden)

Ningning Duan

2015-01-01

Full Text Available Dimensionless nonlinear dynamical equations of a tilted support spring nonlinear packaging system with critical components were obtained under a rectangular pulse. To evaluate the damage characteristics of shocks to packaged products with critical components, a concept of the damage boundary surface was presented and applied to a titled support spring system, with the dimensionless critical acceleration of the system, the dimensionless critical velocity, and the frequency parameter ratio of the system taken as the three basic parameters. Based on the numerical results, the effects of the frequency parameter ratio, the mass ratio, the dimensionless peak pulse acceleration, the angle of the system, and the damping ratio on the damage boundary surface of critical components were discussed. It was demonstrated that with the increase of the frequency parameter ratio, the decrease of the angle, and/or the increase of the mass ratio, the safety zone of critical components can be broadened, and increasing the dimensionless peak pulse acceleration or the damping ratio may lead to a decrease of the damage zone for critical components. The results may lead to a thorough understanding of the design principles for the tilted support spring nonlinear system.

Study of ATES thermal behavior using a steady flow model

Science.gov (United States)

Doughty, C.; Hellstroem, G.; Tsang, C. F.; Claesson, J.

1981-01-01

The thermal behavior of a single well aquifer thermal energy storage system in which buoyancy flow is neglected is studied. A dimensionless formulation of the energy transport equations for the aquifer system is presented, and the key dimensionless parameters are discussed. A simple numerical model is used to generate graphs showing the thermal behavior of the system as a function of these parameters. Some comparisons with field experiments are given to illustrate the use of the dimensionless groups and graphs.

Defining New Parameters for Green Engineering Design of Treatment Reactors

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Susana Boeykens

2016-06-01

Full Text Available This study proposes a green way to design Plug Flow Reactors (PFR that use biodegradable polymer solutions, capable of contaminant retaining, for industrial wastewater treatment. Usually, to the design of a PFR, the reaction rate is determined by tests on a Continuous Stirred-Tank Reactor (CSTR, these generate toxic effluents and also increase the cost of the design. In this work, empirical expressions (called “slip functions”, in terms of the average concentration of the contaminant, were developed through the study of the transport behaviour of CrVI into solutions of xanthan gum. “In situ” XRµF was selected as a no-invasive micro-technique to determine local concentrations. Slip functions were used with laboratory PFR experiments planned in similar conditions, to obtain useful dimensionless parameters for the industrial design. 

Universality in quantum chaos and the one-parameter scaling theory.

Science.gov (United States)

García-García, Antonio M; Wang, Jiao

2008-02-22

The one-parameter scaling theory is adapted to the context of quantum chaos. We define a generalized dimensionless conductance, g, semiclassically and then study Anderson localization corrections by renormalization group techniques. This analysis permits a characterization of the universality classes associated to a metal (g-->infinity), an insulator (g-->0), and the metal-insulator transition (g-->g(c)) in quantum chaos provided that the classical phase space is not mixed. According to our results the universality class related to the metallic limit includes all the systems in which the Bohigas-Giannoni-Schmit conjecture holds but automatically excludes those in which dynamical localization effects are important. The universality class related to the metal-insulator transition is characterized by classical superdiffusion or a fractal spectrum in low dimensions (d < or = 2). Several examples are discussed in detail.

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African Journals Online (AJOL)

De Don

where ;_ is the Frank-Kamenetski i parameter. 0 is the dimensionless temperature variable, (5 is the dimensionless combustible variable and r is the dimensionless radial distance variable. For different values of nand m, we have the following cases subject to the boundary conditions. For Slab: Case 1; n = 0, m = -2 ...

Influence of non-integer order parameter and Hartmann number on the heat and mass transfer flow of a Jeffery fluid over an oscillating vertical plate via Caputo-Fabrizio time fractional derivatives

Science.gov (United States)

Butt, A. R.; Abdullah, M.; Raza, N.; Imran, M. A.

2017-10-01

In this work, semi analytical solutions for the heat and mass transfer of a fractional MHD Jeffery fluid over an infinite oscillating vertical plate with exponentially heating and constant mass diffusion via the Caputo-Fabrizio fractional derivative are obtained. The governing equations are transformed into dimensionless form by introducing dimensionless variables. A modern definition of the Caputo-Fabrizio derivative has been used to develop the fractional model for a Jeffery fluid. The expressions for temperature, concentration and velocity fields are obtained in the Laplace transformed domain. We have used the Stehfest's and Tzou's algorithm for the inverse Laplace transform to obtain the semi analytical solutions for temperature, concentration and velocity fields. In the end, in order to check the physical impact of flow parameters on temperature, concentration and velocity fields, results are presented graphically and in tabular forms.

Unsteady MHD blood flow through porous medium in a parallel plate channel

Science.gov (United States)

Latha, R.; Rushi Kumar, B.

2017-11-01

In this study, we have analyzed heat and mass transfer effects on unsteady blood flow through parallel plate channel in a saturated porous medium in the presence of a transverse magnetic field with thermal radiation. The governing higher order nonlinear PDE’S are converted to dimensionless equations using dimensionless variables. The dimensionless equations are then solved analytically using boundary conditions by choosing the axial flow transport and the fields of concentration and temperature apart from the normal velocity as a function of y and t. The effects of different pertinent parameters appeared in this model viz thermal radiation, Prandtl number, Heat source parameter, Hartmann number, Permeability parameter, Decay parameter on axial flow transport and the normal velocity are analyzed in detail.

Analysis of activation energy in Couette-Poiseuille flow of nanofluid in the presence of chemical reaction and convective boundary conditions

Science.gov (United States)

Zeeshan, A.; Shehzad, N.; Ellahi, R.

2018-03-01

The motivation of the current article is to explore the energy activation in MHD radiative Couette-Poiseuille flow nanofluid in horizontal channel with convective boundary conditions. The mathematical model of Buongiorno [1] effectively describes the current flow analysis. Additionally, the impact of chemical reaction is also taken in account. The governing flow equations are simplified with the help of boundary layer approximations. Non-linear coupled equations for momentum, energy and mass transfer are tackled with analytical (HAM) technique. The influence of dimensionless convergence parameter like Brownian motion parameter, radiation parameter, buoyancy ratio parameter, dimensionless activation energy, thermophoresis parameter, temperature difference parameter, dimensionless reaction rate, Schmidt number, Brinkman number, Biot number and convection diffusion parameter on velocity, temperature and concentration profiles are discussed graphically and in tabular form. From the results, it is elaborate that the nanoparticle concentration is directly proportional to the chemical reaction with activation energy and the performance of Brownian motion on nanoparticle concentration gives reverse pattern to that of thermophoresis parameter.

Exact closed-form solutions of a fully nonlinear asymptotic two-fluid model

Science.gov (United States)

Cheviakov, Alexei F.

2018-05-01

A fully nonlinear model of Choi and Camassa (1999) describing one-dimensional incompressible dynamics of two non-mixing fluids in a horizontal channel, under a shallow water approximation, is considered. An equivalence transformation is presented, leading to a special dimensionless form of the system, involving a single dimensionless constant physical parameter, as opposed to five parameters present in the original model. A first-order dimensionless ordinary differential equation describing traveling wave solutions is analyzed. Several multi-parameter families of physically meaningful exact closed-form solutions of the two-fluid model are derived, corresponding to periodic, solitary, and kink-type bidirectional traveling waves; specific examples are given, and properties of the exact solutions are analyzed.

Effect of Magnetic Field on Entropy Generation Due to Laminar Forced Convection Past a Horizontal Flat Plate

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Moh'd A. Al-Nimr

2004-06-01

Full Text Available Magnetic field effect on local entropy generation due to steady two-dimensional laminar forced convection flow past a horizontal plate was numerically investigated. This study was focused on the entropy generation characteristics and its dependency on various dimensionless parameters. The effect of various dimensionless parameters, such as Hartmann number (Ha, Eckert number (Ec, Prandtl number (Pr, Joule heating parameter (R and the free stream temperature parameter (θ∞ on the entropy generation characteristics is analyzed. The dimensionless governing equations in Cartesian coordinate were solved by an implicit finite difference technique. The solutions were carried out for Ha2=0.5-3, Ec=0.01-0.05, Pr=1-5 and θ∞=1.1-2.5. It was found that, the entropy generation increased with increasing Ha, Ec and R. While, increasing the free stream temperature parameter, and Prandtl number tend to decrease the local entropy generation.

Application of decomposition method and inverse prediction of parameters in a moving fin

International Nuclear Information System (INIS)

Singla, Rohit K.; Das, Ranjan

2014-01-01

Highlights: • Adomian decomposition is used to study a moving fin. • Effects of different parameters on the temperature and efficiency are studied. • Binary-coded GA is used to solve an inverse problem. • Sensitivity analyses of important parameters are carried out. • Measurement error up to 8% is found to be tolerable. - Abstract: The application of the Adomian decomposition method (ADM) is extended to study a conductive–convective and radiating moving fin having variable thermal conductivity. Next, through an inverse approach, ADM in conjunction with a binary-coded genetic algorithm (GA) is also applied for estimation of unknown properties in order to satisfy a given temperature distribution. ADM being one of the widely-used numerical methods for solving non-linear equations, the required temperature field has been obtained using a forward method involving ADM. In the forward problem, the temperature field and efficiency are investigated for various parameters such as convection–conduction parameter, radiation–conduction parameter, Peclet number, convection sink temperature, radiation sink temperature, and dimensionless thermal conductivity. Additionally, in the inverse problem, the effect of random measurement errors, iterative variation of parameters, sensitivity coefficients of unknown parameters are investigated. The performance of GA is compared with few other optimization methods as well as with different temperature measurement points. It is found from the present study that the results obtained from ADM are in good agreement with the results of the differential transformation method available in the literature. It is also observed that for satisfactory reconstruction of the temperature field, the measurement error should be within 8% and the temperature field is strongly dependent on the speed than thermal parameters of the moving fin

Finite time exergy analysis and multi-objective ecological optimization of a regenerative Brayton cycle considering the impact of flow rate variations

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2015-01-01

Highlights: • Defining a dimensionless parameter includes the finite-time and size concepts. • Inserting the concept of exergy of fluid streams into finite-time thermodynamics. • Defining, drawing and modifying of maximum ecological function curve. • Suggesting the appropriate performance zone, according to maximum ecological curve. - Abstract: In this study, the optimal performance of a regenerative Brayton cycle is sought through power and then ecological function maximization using finite-time thermodynamic concept and finite-size components. Multi-objective optimization is used for maximizing the ecological function. Optimizations are performed using genetic algorithm. In order to take into account the finite-time and finite-size concepts in current problem, a dimensionless mass-flow parameter is introduced deploying time variations. The variations of output power, total exergy destruction of the system, and decision variables for the optimum state (maximum ecological function state) are compared to the maximum power state using the dimensionless parameter. The modified ecological function in optimum state is obtained and plotted relating to the dimensionless mass-flow parameter. One can see that the modified ecological function study results in a better performance than that obtained with the maximum power state. Finally, the appropriate performance zone of the heat engine will be obtained

Nominal power density analysis of thermoelectric pins with non-constant cross sections

International Nuclear Information System (INIS)

Shi, Yaoguang; Mei, Deqing; Yao, Zhehe; Wang, Yancheng; Liu, Haiyan; Chen, Zichen

2015-01-01

Highlights: • Nominal power density of TEGs with non-constant cross sections pins is analyzed. • An analytical model of nominal power density (NPD) is developed. • Influences of shape parameter on NPD for different geometric pins are investigated. • Effects of dimensionless efficiency and the temperature ratio on NPD are examined. - Abstract: The investigation of the geometric structure of TEG (thermoelectric generator) pins is essential, as their geometry determines the performance of devices. In this study, nominal power density (NPD) is used to find a better geometric structure of thermoelectric pins of TEGs, since a comparison of maximum dimensionless efficiencies for different geometric pins cannot be used to identify the optimum geometry. The influence of shape parameter on NPD for TEG pins in linear, quadratic and exponential cross-sectional functions is studied. The NPD decreases when the shape parameter increases for different geometric pins, while the maximum values of NPD are the same. Then, the effects of dimensionless efficiency and the temperature ratio on the NPD are analyzed. The NPD decreases with the increase in dimensionless efficiency and temperature ratio. Pins with linear variation in cross section have the highest NPD among the three geometries of pins evaluated

Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap

International Nuclear Information System (INIS)

Yi, W.; Duan, L.-M.

2006-01-01

We map out the detailed phase diagram of a trapped ultracold Fermi gas with population imbalance across a wide Feshbach resonance. We show that under the local density approximation, the properties of the atoms in any (anisotropic) harmonic traps are universally characterized by three dimensionless parameters: the normalized temperature, the dimensionless interaction strength, and the population imbalance. We then discuss the possible quantum phases in the trap, and quantitatively characterize their phase boundaries in various typical parameter regions

Enamel surface topography analysis for diet discrimination. A methodology to enhance and select discriminative parameters

Science.gov (United States)

Francisco, Arthur; Blondel, Cécile; Brunetière, Noël; Ramdarshan, Anusha; Merceron, Gildas

2018-03-01

Tooth wear and, more specifically, dental microwear texture is a dietary proxy that has been used for years in vertebrate paleoecology and ecology. DMTA, dental microwear texture analysis, relies on a few parameters related to the surface complexity, anisotropy and heterogeneity of the enamel facets at the micrometric scale. Working with few but physically meaningful parameters helps in comparing published results and in defining levels for classification purposes. Other dental microwear approaches are based on ISO parameters and coupled with statistical tests to find the more relevant ones. The present study roughly utilizes most of the aforementioned parameters in their more or less modified form. But more than parameters, we here propose a new approach: instead of a single parameter characterizing the whole surface, we sample the surface and thus generate 9 derived parameters in order to broaden the parameter set. The identification of the most discriminative parameters is performed with an automated procedure which is an extended and refined version of the workflows encountered in some studies. The procedure in its initial form includes the most common tools, like the ANOVA and the correlation analysis, along with the required mathematical tests. The discrimination results show that a simplified form of the procedure is able to more efficiently identify the desired number of discriminative parameters. Also highlighted are some trends like the relevance of working with both height and spatial parameters, as well as the potential benefits of dimensionless surfaces. On a set of 45 surfaces issued from 45 specimens of three modern ruminants with differences in feeding preferences (grazing, leaf-browsing and fruit-eating), it is clearly shown that the level of wear discrimination is improved with the new methodology compared to the other ones.

Prediction of moisture transfer parameters for convective drying of shrimp at different pretreatments

Directory of Open Access Journals (Sweden)

Marcus Vinicius da COSTA

2018-04-01

Full Text Available Abstract By the analytical model proposed by Dincer and Dost, the mass transfer parameters (moisture transfer coefficient and moisture diffusivity of shrimp samples were determined. Three sets of drying experiments were performed with three samples of shrimp: without boiling (WB, boiled in salt solution (SB and boiled in salt solution and subjected to liquid smoking process (SBS. The experiments were performed under controlled conditions of drying air at temperature of 60°C and velocity of 1.5 m/s. Experimental dimensionless moisture content data were used to calculate the drying coefficients and lag factors, which were then incorporated into the analytical model for slab and cylinder shapes. The results showed an adequate fit between the experimental data and the values predicted from the correlation. The boiling is the most recommended pretreatment, because provided a shorter drying time, with high values of moisture transfer coefficient and moisture diffusivity.

Parameter values for the estimation of radionuclide transfer to major food crops in Korea

International Nuclear Information System (INIS)

Choi, Yong-Ho; Lim, Kwang-Muk; Jun, In; Keum, Dong-Kwon; Lee, Chang-Woo

2008-01-01

This paper summarizes the results of the radiotracer experiments and field studies performed in Korea for the past 20 years to obtain parameter values for estimating the environmental transfer of radionuclides to food crops. With regards to direct plant contamination, the interception fractions, weathering half-lives and translocation factors of Cs, Sr, Mn, Co and Ru were measured for depositions at different growth stages of selected food crops. In order to investigate an indirect contamination pathway, the soil-to-plant transfer factors (TF m , dimensionless) of Cs, Sr, Mn, Co and/or Zn were measured for rice, Chinese cabbage, radish, soybean, barley, lettuce and so on in one or more soils. In addition, the transfer factors (TF a , m 2 kg -1 ) based on a deposition density were also measured following depositions at different times during the growth periods of several food crops. Particularly for rice and Chinese cabbage, tritium experiments were also carried out for the TF a . The obtained parameter values varied considerably with the soils, crops, radionuclides and deposition times. These data would be applicable to both normal and acute releases not only in Korea but also in many other countries. (author)

Two parameters Lie group analysis and numerical solution of unsteady free convective flow of non-Newtonian fluid

Directory of Open Access Journals (Sweden)

M.J. Uddin

2016-09-01

Full Text Available The two-dimensional unsteady laminar free convective heat and mass transfer fluid flow of a non-Newtonian fluid adjacent to a vertical plate has been analyzed numerically. The two parameters Lie group transformation method that transforms the three independent variables into a single variable is used to transform the continuity, the momentum, the energy and the concentration equations into a set of coupled similarity equations. The transformed equations have been solved by the Runge–Kutta–Fehlberg fourth-fifth order numerical method with shooting technique. Numerical calculations were carried out for the various parameters entering into the problem. The dimensionless velocity, temperature and concentration profiles were shown graphically and the skin friction, heat and mass transfer rates were given in tables. It is found that friction factor and heat transfer (mass transfer rate for methanol are higher (lower than those of hydrogen and water vapor. Friction factor decreases while heat and mass transfer rate increase as the Prandtl number increases. Friction (heat and mass transfer rate factor of Newtonian fluid is higher (lower than the dilatant fluid.

Entropy in the Present and Early Universe: New Small Parameters and Dark Energy Problem

Directory of Open Access Journals (Sweden)

Alexander Shalyt-Margolin

2010-04-01

Full Text Available It is demonstrated that entropy and its density play a significant role in solving the problem of the vacuum energy density (cosmological constant of the Universe and hence the dark energy problem. Taking this in mind, two most popular models for dark energy—Holographic Dark Energy Model and Agegraphic Dark Energy Model—are analysed. It is shown that the fundamental quantities in the first of these models may be expressed in terms of a new small dimensionless parameter that is naturally occurring in High Energy Gravitational Thermodynamics and Gravitational Holography (UV-limit. On this basis, the possibility of a new approach to the problem of Quantum Gravity is discussed. Besides, the results obtained on the uncertainty relation of the pair “cosmological constant–volume of space-time”, where the cosmological constant is a dynamic quantity, are reconsidered and generalized up to the Generalized Uncertainty Relation.

Parametric Study on the Characteristics of Multiphase Laminar Flow with Density Difference in Various Microchannels

International Nuclear Information System (INIS)

Paek, Seung Ho; Kim, Dong Sung; Choi, Young Ki

2009-01-01

In this paper, we have performed a parametric study on the characteristics of multiphase laminar flow with density difference in various microchannels. The interface between multiphase fluids is rotated by the gravitational forces induced by density difference. The numerical simulations were carried out via commercial CFD package to study the characteristics of multiphase laminar flow. The results of the numerical simulations in this study were verified by comparing with the previously reported experimental results in the literature. We have also proposed a new dimensionless relationship between dimensionless rotation angle of interface and dimensionless parameters are proposed for square microchannels with various aspect ratios. The dimensionless relationship could be widely applied to the reliable design of various microfluidic devices dealing with multiphase laminar flow

Hydrologic classification of rivers based on cluster analysis of dimensionless hydrologic signatures: Applications for environmental instream flows

Science.gov (United States)

Praskievicz, S. J.; Luo, C.

2017-12-01

Classification of rivers is useful for a variety of purposes, such as generating and testing hypotheses about watershed controls on hydrology, predicting hydrologic variables for ungaged rivers, and setting goals for river management. In this research, we present a bottom-up (based on machine learning) river classification designed to investigate the underlying physical processes governing rivers' hydrologic regimes. The classification was developed for the entire state of Alabama, based on 248 United States Geological Survey (USGS) stream gages that met criteria for length and completeness of records. Five dimensionless hydrologic signatures were derived for each gage: slope of the flow duration curve (indicator of flow variability), baseflow index (ratio of baseflow to average streamflow), rising limb density (number of rising limbs per unit time), runoff ratio (ratio of long-term average streamflow to long-term average precipitation), and streamflow elasticity (sensitivity of streamflow to precipitation). We used a Bayesian clustering algorithm to classify the gages, based on the five hydrologic signatures, into distinct hydrologic regimes. We then used classification and regression trees (CART) to predict each gaged river's membership in different hydrologic regimes based on climatic and watershed variables. Using existing geospatial data, we applied the CART analysis to classify ungaged streams in Alabama, with the National Hydrography Dataset Plus (NHDPlus) catchment (average area 3 km2) as the unit of classification. The results of the classification can be used for meeting management and conservation objectives in Alabama, such as developing statewide standards for environmental instream flows. Such hydrologic classification approaches are promising for contributing to process-based understanding of river systems.

The quantitative characterization of sintering of urania powders

International Nuclear Information System (INIS)

Das, P.; Kulkarni, U.D.

1981-01-01

This paper presents a unified approach towards characterization of the sintering behaviour of UO 2 powders in terms of their extrinsic properties. Empirical equations connecting the sintering index with various powder parameters have been set up. The influence of various powder parameters, either individually or as dimensionless/dimensional groups, on the sintering behaviour has been studied. The relative importance of these factors has also been analysed. A good polynomial fit has been obtained for variation of sintering index with some of the powder parameters and dimensionless/dimensional groups. The equations are expected to provide a good basis for assessing the sinterability of UO 2 powders. (Auth.)

Mixed Convection Heat Transfer on the Outside of a Vertical Cylinder

Energy Technology Data Exchange (ETDEWEB)

Bhattacharyya, A

1965-10-15

An experimental study was made of turbulent heat transfer from a vertical cylinder placed in a square channel. The flow medium was water flowing upwards. Basic differential equations governing the mixed flow heat transfer phenomena in a vertical annulus are presented. A dimensional analysis is done to find the dimensionless variables affecting the relative magnitude of the effect of buoyancy on forced convection heat transfer. Dimensionless equations correlating the experimental data ana incorporating a buoyancy parameter of the form Gr/Re{sup 2} are presented. Reynolds number range covered is 690 to 129,500 and the Rayleigh num- ber range covered is 10{sup 9} to 4.2 x 10{sup 13} . Effect of different length parameters, like hydraulic diameter and distance of the measuring point from the inlet of the test section, on dimensionless equations are studied.

Propagation of bottom-trapped waves over variable topography

Digital Repository Service at National Institute of Oceanography (India)

Shetye, S.R.

Fig. 5. Variation in the magnitude of bottom-intensification of the incident and reflected waves (a and if) with meridional wavenumber (B, in dimensionless units). The values of parameters used in the computations are defined in the caption to Fig. 4... 1 I I I 0'0 1.0 (X) =~ Fig. 8. p~°)(x, y, z, 0) on the planes (a) z = 1, and (b) y = 0. The spatial coordinates are in dimensionless units. The values of the parameters used to compute the solution are defined in the caption to Fig. 4. The zonal...

Statistical modeling of geopressured geothermal reservoirs

Science.gov (United States)

Ansari, Esmail; Hughes, Richard; White, Christopher D.

2017-06-01

Identifying attractive candidate reservoirs for producing geothermal energy requires predictive models. In this work, inspectional analysis and statistical modeling are used to create simple predictive models for a line drive design. Inspectional analysis on the partial differential equations governing this design yields a minimum number of fifteen dimensionless groups required to describe the physics of the system. These dimensionless groups are explained and confirmed using models with similar dimensionless groups but different dimensional parameters. This study models dimensionless production temperature and thermal recovery factor as the responses of a numerical model. These responses are obtained by a Box-Behnken experimental design. An uncertainty plot is used to segment the dimensionless time and develop a model for each segment. The important dimensionless numbers for each segment of the dimensionless time are identified using the Boosting method. These selected numbers are used in the regression models. The developed models are reduced to have a minimum number of predictors and interactions. The reduced final models are then presented and assessed using testing runs. Finally, applications of these models are offered. The presented workflow is generic and can be used to translate the output of a numerical simulator into simple predictive models in other research areas involving numerical simulation.

Analysis of heat transfer for unsteady MHD free convection flow of rotating Jeffrey nanofluid saturated in a porous medium

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Nor Athirah Mohd Zin

Full Text Available In this article, the influence of thermal radiation on unsteady magnetohydrodynamics (MHD free convection flow of rotating Jeffrey nanofluid passing through a porous medium is studied. The silver nanoparticles (AgNPs are dispersed in the Kerosene Oil (KO which is chosen as conventional base fluid. Appropriate dimensionless variables are used and the system of equations is transformed into dimensionless form. The resulting problem is solved using the Laplace transform technique. The impact of pertinent parameters including volume fraction φ, material parameters of Jeffrey fluid λ1, λ, rotation parameter r, Hartmann number Ha, permeability parameter K, Grashof number Gr, Prandtl number Pr, radiation parameter Rd and dimensionless time t on velocity and temperature profiles are presented graphically with comprehensive discussions. It is observed that, the rotation parameter, due to the Coriolis force, tends to decrease the primary velocity but reverse effect is observed in the secondary velocity. It is also observed that, the Lorentz force retards the fluid flow for both primary and secondary velocities. The expressions for skin friction and Nusselt number are also evaluated for different values of emerging parameters. A comparative study with the existing published work is provided in order to verify the present results. An excellent agreement is found. Keywords: Jeffrey nanofluid, AgNPs, MHD and Porosity, Rotating flow, Laplace transform technique

On the effect of velocity gradients on the depth of correlation in μPIV

International Nuclear Information System (INIS)

Mustin, B; Stoeber, B

2016-01-01

The present work revisits the effect of velocity gradients on the depth of the measurement volume (depth of correlation) in microscopic particle image velocimetry (μPIV). General relations between the μPIV weighting functions and the local correlation function are derived from the original definition of the weighting functions. These relations are used to investigate under which circumstances the weighting functions are related to the curvature of the local correlation function. Furthermore, this work proposes a modified definition of the depth of correlation that leads to more realistic results than previous definitions for the case when flow gradients are taken into account. Dimensionless parameters suitable to describe the effect of velocity gradients on μPIV cross correlation are derived and visual interpretations of these parameters are proposed. We then investigate the effect of the dimensionless parameters on the weighting functions and the depth of correlation for different flow fields with spatially constant flow gradients and with spatially varying gradients. Finally this work demonstrates that the results and dimensionless parameters are not strictly bound to a certain model for particle image intensity distributions but are also meaningful when other models for particle images are used. (paper)

On the effect of velocity gradients on the depth of correlation in μPIV

Science.gov (United States)

Mustin, B.; Stoeber, B.

2016-03-01

The present work revisits the effect of velocity gradients on the depth of the measurement volume (depth of correlation) in microscopic particle image velocimetry (μPIV). General relations between the μPIV weighting functions and the local correlation function are derived from the original definition of the weighting functions. These relations are used to investigate under which circumstances the weighting functions are related to the curvature of the local correlation function. Furthermore, this work proposes a modified definition of the depth of correlation that leads to more realistic results than previous definitions for the case when flow gradients are taken into account. Dimensionless parameters suitable to describe the effect of velocity gradients on μPIV cross correlation are derived and visual interpretations of these parameters are proposed. We then investigate the effect of the dimensionless parameters on the weighting functions and the depth of correlation for different flow fields with spatially constant flow gradients and with spatially varying gradients. Finally this work demonstrates that the results and dimensionless parameters are not strictly bound to a certain model for particle image intensity distributions but are also meaningful when other models for particle images are used.

The potential of computer vision, optical backscattering parameters and artificial neural network modelling in monitoring the shrinkage of sweet potato (Ipomoea batatas L.) during drying.

Science.gov (United States)

Onwude, Daniel I; Hashim, Norhashila; Abdan, Khalina; Janius, Rimfiel; Chen, Guangnan

2018-03-01

Drying is a method used to preserve agricultural crops. During the drying of products with high moisture content, structural changes in shape, volume, area, density and porosity occur. These changes could affect the final quality of dried product and also the effective design of drying equipment. Therefore, this study investigated a novel approach in monitoring and predicting the shrinkage of sweet potato during drying. Drying experiments were conducted at temperatures of 50-70 °C and samples thicknesses of 2-6 mm. The volume and surface area obtained from camera vision, and the perimeter and illuminated area from backscattered optical images were analysed and used to evaluate the shrinkage of sweet potato during drying. The relationship between dimensionless moisture content and shrinkage of sweet potato in terms of volume, surface area, perimeter and illuminated area was found to be linearly correlated. The results also demonstrated that the shrinkage of sweet potato based on computer vision and backscattered optical parameters is affected by the product thickness, drying temperature and drying time. A multilayer perceptron (MLP) artificial neural network with input layer containing three cells, two hidden layers (18 neurons), and five cells for output layer, was used to develop a model that can monitor, control and predict the shrinkage parameters and moisture content of sweet potato slices under different drying conditions. The developed ANN model satisfactorily predicted the shrinkage and dimensionless moisture content of sweet potato with correlation coefficient greater than 0.95. Combined computer vision, laser light backscattering imaging and artificial neural network can be used as a non-destructive, rapid and easily adaptable technique for in-line monitoring, predicting and controlling the shrinkage and moisture changes of food and agricultural crops during drying. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

STRESS-DEFORMED STATE OF A STRUT-FRAMED CRANE GIRDER

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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. 

Assessment of capabilities of lidar systems in day-and night-time under different atmospheric and internal-noise conditions

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Agishev, Ravil; Comerón, Adolfo

2018-04-01

As an application of the dimensionless parameterization concept proposed earlier for the characterization of lidar systems, the universal assessment of lidar capabilities in day and night conditions is considered. The dimensionless parameters encapsulate the atmospheric conditions, the lidar optical and optoelectronic characteristics, including the photodetector internal noise, and the sky background radiation. Approaches to ensure immunity of the lidar system to external background radiation are discussed.

Anisotropic permeable porous facing and slip velocity on squeeze film in an axially undefined journal bearing with ferrofluid lubricant

International Nuclear Information System (INIS)

Shah, R.C.; Bhat, M.V.

2004-01-01

Ferrofluid squeeze film in an axially undefined porous journal bearing was analyzed to determine its performance considering anisotropic permeability of the porous facing and slip velocity at the interface of porous matrix and film region using Jenkins flow model. Expressions were obtained for dimensionless pressure, load capacity and response time of the squeeze film. How to deduce results for no-slip case, isotropic porous case and for Neuringer-Rosensweig model case were indicated. The computed values of dimensionless load capacity and response time were displayed in graphical form. They increased with increasing values of eccentricity ratio and anisotropic parameter while they decreased with increasing values of slip parameter or material parameter of Jenkins model

Theoretical Analysis of Effects of Wall Suction on Entropy Generation Rate in Laminar Condensate Layer on Horizontal Tube

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Tong-Bou Chang

2014-01-01

Full Text Available The effects of wall suction on the entropy generation rate in a two-dimensional steady film condensation flow on a horizontal tube are investigated theoretically. In analyzing the liquid flow, the effects of both the gravitational force and the viscous force are taken into account. In addition, a film thickness reduction ratio, Sf, is introduced to evaluate the effect of wall suction on the thickness of the condensate layer. The analytical results show that, the entropy generation rate depends on the Jakob number Ja, the Rayleigh number Ra, the Brinkman number Br, the dimensionless temperature difference ψ, and the wall suction parameter Sw. In addition, it is shown that in the absence of wall suction, a closed-form correlation for the Nusselt number can be derived. Finally, it is shown that the dimensionless entropy generation due to heat transfer, NT, increases with an increasing suction parameter Sw, whereas the dimensionless entropy generation due to liquid film flow friction, NF, decreases.

Estimating hourly direct and diffuse solar radiation for the compilation of solar radiation distribution maps

International Nuclear Information System (INIS)

Ueyama, H.

2005-01-01

This paper presents a new method for estimating hourly direct and diffuse solar radiation. The essence of the method is the estimation of two important factors related to solar radiation, atmospheric transmittance and a dimensionless parameter, using empirical and physical equations and data from general meteorological observation stations. An equation for atmospheric transmittance of direct solar radiation and a dimensionless parameter representing diffuse solar radiation are developed. The equation is based on multiple regression analysis and uses three parameters as explanatory variates: calculated hourly extraterrestrial solar radiation on a horizontal plane, observed hourly sunshine duration and hourly precipitation as observed at a local meteorological observatory. The dimensionless parameter for estimating a diffuse solar radiation is then determined by linear least squares using observed hourly solar radiation at a local meteorological observatory. The estimated root mean square error (RMSE) of hourly direct and diffuse solar radiation is about 0.0-0.2 MJ¥m(-2)¥h(-1) in each mean period. The RMSE of the ten-day and monthly means of these quantities is about 0.0-0.2 MJ¥m(-2)¥h(-1), based on comparisons with AMeDAS station data, located at a distance of 6 km

Improved lumped models for transient combined convective and radiative cooling of multi-layer composite slabs

International Nuclear Information System (INIS)

An Chen; Su Jian

2011-01-01

Improved lumped parameter models were developed for the transient heat conduction in multi-layer composite slabs subjected to combined convective and radiative cooling. The improved lumped models were obtained through two-point Hermite approximations for integrals. Transient combined convective and radiative cooling of three-layer composite slabs was analyzed to illustrate the applicability of the proposed lumped models, with respect to different values of the Biot numbers, the radiation-conduction parameter, the dimensionless thermal contact resistances, the dimensionless thickness, and the dimensionless thermal conductivity. It was shown by comparison with numerical solution of the original distributed parameter model that the higher order lumped model (H 1,1 /H 0,0 approximation) yielded significant improvement of average temperature prediction over the classical lumped model. In addition, the higher order (H 1,1 /H 0,0 ) model was applied to analyze the transient heat conduction problem of steel-concrete-steel sandwich plates. - Highlights: → Improved lumped models for convective-radiative cooling of multi-layer slabs were developed. → Two-point Hermite approximations for integrals were employed. → Significant improvement over classical lumped model was achieved. → The model can be applied to high Biot number and high radiation-conduction parameter. → Transient heat conduction in steel-concrete-steel sandwich pipes was analyzed as an example.

Nonlinear dynamics of a flexible rotor supported by turbulent journal bearings with couple stress fluid

International Nuclear Information System (INIS)

Lo, C.-Y.; Chang-Jian, C.-W.

2008-01-01

This study presents a dynamic analysis of a rotor supported by two turbulent flow model journal bearings and lubricated with couple stress fluid under nonlinear suspension. The dynamics of the rotor center and bearing center is studied. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The results show that the values of dimensionless parameters l* strongly influence dynamic motions of bearing and rotor centre. It is found that couple stress fluid improve the stability of the system when l* > 0.4 even if the flow of this system is turbulent. We also demonstrated that the dimensionless rotational speed ratios s and the dimensionless unbalance parameter β are also significant system parameters. The modeling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided

Numerical investigation of potential stratification caused by a cryogenic helium spill inside a tunnel

Science.gov (United States)

Sinclair, Cameron; Malecha, Ziemowit; Jedrusyna, Artur

2018-04-01

The sudden release of cryogenic fluid into an accelerator tunnel can pose a significant health and safety risk. For this reason, it is important to evaluate the consequences of such a spill. Previous publications concentrated on either Oxygen Deficiency Hazard or the evaluation of mathematical models using experimental data. No studies to date have focussed on the influence of cryogen inlet conditions on flow development. In this paper, the stratification behaviour of low-temperature helium released into an air-filled accelerator tunnel is investigated for varying helium inlet diameters. A numerical model was constructed using the OpenFOAM Toolbox of a generalised 3D geometry, with similar hydraulic characteristics to the CERN and SLAC tunnels. This model has been validated against published experimental and numerical data. A dimensionless parameter, based on Bakke number, was then determined for the onset of stratification, taking into account the helium inlet diameter; a dimensionless parameter for the degree of stratification was also employed. The simulated flow behaviour is described in terms of these dimensionless parameters, as well as the temperature and oxygen concentration at various heights throughout the tunnel.

A closed form solution for the response of a long elastic beam to dynamic loading

International Nuclear Information System (INIS)

Mittal, R.K.

1989-01-01

Closed form solutions have been obtained using Fourier transform method for the deflection, curvature and particle velocity of a long elastic beam when it is subjected to a concentrated transverse force which is varying with time. These solutions have been illustrated with the help of two force histories, i.e. a half-sine pulse and a rectangular pulse. Dimensionless parameters representing deflection, curvature and particle velocity have been plotted as functions of dimensionless distance and dimensionless time. Furthermore, the particular case of constant velocity impact which has been studied by other authors using different techniques has also been considered in the present paper and the results compare within numerical errors involved in the evaluation of integrals. (orig.) [de

Scaling for Dynamical Systems in Biology.

Science.gov (United States)

Ledder, Glenn

2017-11-01

Asymptotic methods can greatly simplify the analysis of all but the simplest mathematical models and should therefore be commonplace in such biological areas as ecology and epidemiology. One essential difficulty that limits their use is that they can only be applied to a suitably scaled dimensionless version of the original dimensional model. Many books discuss nondimensionalization, but with little attention given to the problem of choosing the right scales and dimensionless parameters. In this paper, we illustrate the value of using asymptotics on a properly scaled dimensionless model, develop a set of guidelines that can be used to make good scaling choices, and offer advice for teaching these topics in differential equations or mathematical biology courses.

The effective thermal conductivity of porous media based on statistical self-similarity

International Nuclear Information System (INIS)

Kou Jianlong; Wu Fengmin; Lu Hangjun; Xu Yousheng; Song Fuquan

2009-01-01

A fractal model is presented based on the thermal-electrical analogy technique and statistical self-similarity of fractal saturated porous media. A dimensionless effective thermal conductivity of saturated fractal porous media is studied by the relationship between the dimensionless effective thermal conductivity and the geometrical parameters of porous media with no empirical constant. Through this study, it is shown that the dimensionless effective thermal conductivity decreases with the increase of porosity (φ) and pore area fractal dimension (D f ) when k s /k g >1. The opposite trends is observed when k s /k g t ). The model predictions are compared with existing experimental data and the results show that they are in good agreement with existing experimental data.

CROSS-FLOW ULTRAFILTRATION OF SECONDARY EFFLUENTS. MEMBRANE FOULING ANALYSIS

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Luisa Vera

2014-12-01

Full Text Available The application of cross-flow ultrafiltration to regenerate secondary effluents is limited by membrane fouling. This work analyzes the influence of the main operational parameters (transmembrane pressure and cross-flow velocity about the selectivity and fouling observed in an ultrafiltration tubular ceramic membrane. The experimental results have shown a significant retention of the microcolloidal and soluble organic matter (52 – 54% in the membrane. The fouling analysis has defined the critical operational conditions where the fouling resistance is minimized. Such conditions can be described in terms of a dimensionless number known as shear stress number and its relationship with other dimensionless parameter, the fouling number.

Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

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Waqar Azeem Khan

Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer

Magnetohydrodynamics effect on convective boundary layer flow and heat transfer of viscoelastic micropolar fluid past a sphere

Science.gov (United States)

Amera Aziz, Laila; Kasim, Abdul Rahman Mohd; Zuki Salleh, Mohd; Syahidah Yusoff, Nur; Shafie, Sharidan

2017-09-01

The main interest of this study is to investigate the effect of MHD on the boundary layer flow and heat transfer of viscoelastic micropolar fluid. Governing equations are transformed into dimensionless form in order to reduce their complexity. Then, the stream function is applied to the dimensionless equations to produce partial differential equations which are then solved numerically using the Keller-box method in Fortran programming. The numerical results are compared to published study to ensure the reliability of present results. The effects of selected physical parameters such as the viscoelastic parameter, K, micropolar parameter, K1 and magnetic parameter, M on the flow and heat transfer are discussed and presented in tabular and graphical form. The findings from this study will be of critical importance in the fields of medicine, chemical as well as industrial processes where magnetic field is involved.

Conditions for tidal bore formation in convergent alluvial estuaries

Science.gov (United States)

Bonneton, Philippe; Filippini, Andrea Gilberto; Arpaia, Luca; Bonneton, Natalie; Ricchiuto, Mario

2016-04-01

Over the last decade there has been an increasing interest in tidal bore dynamics. However most studies have been focused on small-scale bore processes. The present paper describes the first quantitative study, at the estuary scale, of the conditions for tidal bore formation in convergent alluvial estuaries. When freshwater discharge and large-scale spatial variations of the estuary water depth can be neglected, tide propagation in such estuaries is controlled by three main dimensionless parameters: the nonlinearity parameter ε0 , the convergence ratio δ0 and the friction parameter ϕ0. In this paper we explore this dimensionless parameter space, in terms of tidal bore occurrence, from a database of 21 estuaries (8 tidal-bore estuaries and 13 non tidal-bore estuaries). The field data point out that tidal bores occur for convergence ratios close to the critical convergence δc. A new proposed definition of the friction parameter highlights a clear separation on the parameter plane (ϕ0,ε0) between tidal-bore estuaries and non tidal-bore estuaries. More specifically, we have established that tidal bores occur in convergent estuaries when the nonlinearity parameter is greater than a critical value, εc , which is an increasing function of the friction parameter ϕ0. This result has been confirmed by numerical simulations of the two-dimensional Saint Venant equations. The real-estuary observations and the numerical simulations also show that, contrary to what is generally assumed, tide amplification is not a necessary condition for tidal bore formation. The effect of freshwater discharge on tidal bore occurrence has been analyzed from the database acquired during three long-term campaigns carried out on the Gironde/Garonne estuary. We have shown that in the upper estuary the tidal bore intensity is mainly governed by the local dimensionless tide amplitude ε. The bore intensity is an increasing function of ε and this relationship does not depend on freshwater

Periodic flow hydrodynamic resistance parameters for woven screen matrices at cryogenic temperatures

Science.gov (United States)

Perrella, M. D.; Ghiaasiaan, S. M.

2017-12-01

The regenerator is a critical component in all Stirling and Pulse Tube cryocoolers. It generally consists of a microporous metallic or rare-earth filler material contained within a cylindrical shell. Accurate modelling of the hydrodynamic and thermal behaviour of different regenerator materials is crucial to the successful design of cryogenic systems. Previous investigations have used experimental measurements at steady and periodic flow conditions in conjunction with pore-level CFD analysis to determine the pertinent hydrodynamic parameters, namely the Darcy permeability and Forchheimer coefficients. Due to the difficulty associated with experimental measurement at cryogenic temperatures, past investigations were mostly performed at ambient conditions and their results are assumed to be appropriate for cryogenic temperatures. In this study, a regenerator filled with woven screen matrices such as 400 mesh T316 stainless steel were assembled and experimentally tested under periodic helium flow at cryogenic temperatures. The mass flow and pressure drop data were analysed using CFD to determine the dimensionless friction factor, Darcy Permeability and Forchheimer coefficients. These results are compared to previous investigations at ambient temperature conditions, and the relevance of room-temperature models and correlations to cryogenic temperatures is critically assessed.

Deformation of ferrofluid marbles in the presence of a permanent magnet.

Science.gov (United States)

Nguyen, Nam-Trung

2013-11-12

This paper investigates the deformation of ferrofluid marbles in the presence of a permanent magnet. Ferrofluid marbles are formed using a water-based ferrofluid and 1 μm hydrophobic polytetrafluoride particles. A marble placed on a Teflon coated glass plate deforms under gravity. In the presence of a permanent magnet, the marble is further deformed with a larger contact area. The geometric parameters are normalized by the radius of an undistorted spherical marble. The paper first discusses a scaling relationship between the dimensionless radius of the contact area as well as the dimensionless height and the magnetic Bond number. The dimensionless contact radius is proportional to the fourth root of the magnetic bond number. The dimensionless height scales with the inverse square root of the magnetic Bond number. In the case of a moving marble dragged by a permanent magnet, the deformation is evaluated as the difference between advancing and receding curvatures of the top view. The dimensionless height and the contact diameter of the marble do not significantly depend on the speed or the capillary number. The scaling analysis and experimental data show that the deformation is proportional to the capillary number.

Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies

Science.gov (United States)

Wagner, Brian J.; Harvey, Judson W.

1997-01-01

Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI ≫ 1.0), solute

Multi-objective shape optimization of double pipe heat exchanger with inner corrugated tube using RSM method

International Nuclear Information System (INIS)

Han, Huai-Zhi; Li, Bing-Xi; Wu, Hao; Shao, Wei

2015-01-01

Integrated a fully developing three-dimensional heat transfer and flow model, a multi-objective optimization aims to fulfill the geometric design for double-tube heat exchangers with inner corrugated tube is investigated in this work with RSM. Dimensionless corrugation pitch (p/D), dimensionless corrugation height (H/D), dimensionless corrugation radius (r/D) and Reynolds number (Re) are considered as four design parameters. Considering the process parameters, the characteristic numbers involving heat transfer characteristic, resistance characteristic and overall heat transfer performance calculated by CFD, and are served as objective functions to the RSM (Nu c , f c , Nu c /Nu s , f c /f s and h in this paper). The results of optimal designs are a set of multiple optimum solutions, called 'Pareto optimal solutions'. It reveals the identical tendency of Nu c /Nu s and f c /f s reflecting the conflict between them that means augmenting the heat transfer performance with various design parameters in the optimal situation inevitably sacrificed the increase of flow resistance. According to the Pareto optimal curves, the optimum designing parameters of double pipe heat exchanger with inner corrugated tube under the constrains of Nu c /Nu s ≥1.2 are found to be P/D = 0.82, H/D = 0.22, r/D = 0.23, Re = 26,263, corresponding to the maximum value of η = 1.12. (authors)

Unsteady axisymmetric flow of a micropolar fluid between the ...

African Journals Online (AJOL)

The influence of several parameters on dimensionless velocities is presented through plots. The behavior of skin friction and couple stress coefficients is tabulated against various values of the pertinent parameters. Keywords: Unsteady flow, micropolar fluid, radial stretching, skin friction coefficient, couple stress coefficient

Effect of thermal radiation and Hall current on heat and mass transfer of unsteady MHD flow of a viscoelastic micropolar fluid through a porous medium

Directory of Open Access Journals (Sweden)

B.I. Olajuwon

2014-12-01

Full Text Available Heat and mass transfer effects on unsteady flow of a viscoelastic micropolar fluid over an infinite moving permeable plate in a saturated porous medium in the presence of a transverse magnetic field with Hall effect and thermal radiation are studied. The governing system of partial differential equations is transformed to dimensionless equations using dimensionless variables. The dimensionless equations are then solved analytically using perturbation technique to obtain the expressions for velocity, microrotation, temperature and concentration. With the help of graphs, the effects of magnetic field parameter M, thermal radiation parameter Nr, Hall current parameter m, K, viscoelastic parameter a, and slip parameter h on the velocity, microrotation, temperature and concentration fields within the boundary layer are discussed. The result showed that increase in Nr and m increases translational velocity across the boundary layer while (a decreases translational velocity in the vicinity of the plate but the reverse happens when away from the plate. As h increases the translational velocity across the boundary layer increases. The higher the values of Nr, the higher the micro-rotational velocity effect while m lowers it. Also the effects n, a, m, Nr, Pr and Sc on the skin friction coefficient, Nusselt number and Sherwood numbers are presented numerically in tabular form. The result also revealed that increase in n reduces the skin friction coefficient. Pr enhances the rate of heat transfer while Sc enhances the rate of mass transfer.

Experimental characterization of the spreading and break-up of liquid flat-fan sheets discharging in a low-density atmosphere and application to BrLi solutions

Energy Technology Data Exchange (ETDEWEB)

Palacios, E. [Universidad Politecnica de Madrid (Spain). Departamento de Mecanica Industrial; Nogueira, J.; Rodriguez, P.A.; Lecuona, A. [Universidad Carlos III de Madrid (Spain). Departamento de Ingenieria Termica y de Fluidos

2009-02-15

This work presents and characterizes the existence of two different regimes in the spreading and break-up of liquid flat-fan sheets when discharging in low-density atmospheres. The motivation of the study is the improvement on the absorption phenomena of lithium bromide aqueous solution when discharging in a 600-1,500 Pa water vapor environment. This corresponds to the absorber conditions in current absorption closed-cycle cooling machines. Despite this, the dimensionless characterization obtained has universal validity. The conditions that define the change in the break-up regime, the dimensionless sheet break-up length and the break-up time are given as a function of the parameters involved. Digital particle tracking velocimetry (PTV) has been applied to measure the velocity field and additional visualization techniques have been used to further characterize the break-up process. The experiments verify the existence of critical gas-to-liquid density and viscosity ratios below which gas to liquid interaction becomes negligible. The article also offers expressions that define their values as a function of the other dimensionless parameters. (orig.)

Study of entropy generation in a slab with non-uniform internal heat generation

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El Haj Assad Mamdouh

2013-01-01

Full Text Available Analysis of entropy generation in a rectangular slab with a nonuniform internal heat generation is presented. Dimensionless local and total entropy generation during steady state heat conduction through the slab are obtained. Two different boundary conditions have been considered in the analysis, the first with asymmetric convection and the second with constant slab surface temperature. Temperature distribution within the slab is obtained analytically. The study investigates the effect of some relevant dimensionless heat transfer parameters on entropy generation. The results show that there exists a minimum local entropy generation but there does not exist a minimum total entropy generation for certain combinations of the heat transfer parameters. The results of calculations are presented graphically.

Instability of single-phase natural circulation

International Nuclear Information System (INIS)

Xie Heng; Zhang Jinling; Jia Dounan

1997-01-01

The author has investigated the instability of single-phase flows in natural circulation loops. The momentum equation and energy equation are made dimensionless according to some definitions, and some important dimensionless parameters are gotten. The authors decomposed the mean mass flowrate and temperature into a steady solution and a small disturbance equations. Through solving the disturbance equations, the authors get the neutral stability curves. The authors have studied the effect of the two parameters which represent the ratio of buoyancy force to the friction loss in the loop on the stability of loops. The authors also have studied the effect of the difference of height between the center of heat source and the heat sink on the stability

Band structure analysis of a thin plate with periodic arrangements of slender beams

Science.gov (United States)

Serrano, Ó.; Zaera, R.; Fernández-Sáez, J.

2018-04-01

This work analyzes the wave propagation in structures composed of a periodic arrangement of vertical beams rigidly joined to a plate substrate. Three different configurations for the distribution of the beams have been analyzed: square, triangular, and hexagonal. A dimensional analysis of the problem indicates the presence of three dimensionless groups of parameters controlling the response of the system. The main features of the wave propagation have been found using numerical procedures based on the Finite Element Method, through the application of the Bloch's theorem for the corresponding primitive unit cells. Illustrative examples of the effect of the different dimensionless parameters on the dynamic behavior of the system are presented, providing information relevant for design.

Radial plasma profile and neutron yield in an adiabatic trap with fast atom injection

International Nuclear Information System (INIS)

Panov, D.A.

1988-01-01

Radial profiles of ion densities depending on two dimensionless parameters, which values are determined by the trap, plasma and injected beam parameters are found in dimensionless units for a plasma generated by fast atom injection in an adiabatic trap. The calculated profiles are used for determining the neutron yield. Simple approximated dimensional relations permitting to estimate quickly neutron yield, required injection power, flux of charge exchange atoms on the wall around the plasma in a wide energy range of injected atoms, trap field modulud, injection angle, trap radius and length are determined. The energetic efficiency of neutron production is estimated and it is shown that it grows with the injection energy. 7 refs.; 7 figs

Rotating ring-ring electrode theory and experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kellyb, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

The Rotating Ring-Ring Electrode. Theory and Experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kelly, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

The effect of heat generation in inclined slats on the natural convective heat transfer from an isothermal heated vertical plate

International Nuclear Information System (INIS)

Oosthuizen, P.H.; Sun, L.; Naylor, D.

2003-01-01

Natural convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat surfaces (termed 'slats') near the heated surface, these surfaces being, in general, inclined to the heated surface. There is, in general, a uniform heat generation in the slats. The slats are pivoted about their centre-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air being considered. The heat generation in the slats in this situation is the result of solar radiation passing through the window and falling on and being absorbed by the slats of the blind. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. The solution has the following parameters: (1) the Rayleigh number (2) the Prandtl number (3) the dimensionless heat generation rate in the slats per unit frontal area (4) the dimensionless distance of the slat center point (the pivot point) from the surface (5) the dimensionless slat size (6) the dimensionless slat spacing (7) the angle of inclination of the slats. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated vertical surface has been examined. (author)

Analysis Method of Combine Harvesters Technical Level by Functional and Structural Parameters

Directory of Open Access Journals (Sweden)

E. V. Zhalnin

2018-01-01

Full Text Available The analysis of modern methods of evaluation of the grain harvesters technical level revealed a discrepancy in various criteria: comparative parameters, dimensionless series, the names of firms, the power of the motor, the width of the capture of the harvester, the capacity at the location of the manufacturer plant, advertising brands. (Purpose of research This led to a variety in the name of harvester models, which significantly complicates the assessment of their technical level, complicates the choice of agricultural necessary to him fashion, does not give the perception of the continuity of the change of generations of combines, makes it impossible to analyze trends in their development, does not disclose the technological essence of a model, but - most importantly - combines can not be compared with each other. The figures in the name of the harvester model are not related functionally to the main parameters and performance capabilities. (Materials and methods The close correlation in the form of a linear equation between their design parameters and the capacity of combines was revealed. Verification of this equation in the process of operation of the combine showed that it statistically stable and the estimates are always within the confidence interval with an error of 5-8 percent. It was found that four parameters of the variety of factors, that affect the performance of the harvester per hour net time, having most close correlation with it are: the motor power and the square of the separation concave, straw walkers and sieves for cleaning. (Results and discussion On the basis of the revealed correlation dependence we proposed a new method of assessment of the technical level of combines, which is based on the throughput (kg/s of the wetted material and the size series, indicating the nominal productivity of the combine in centners of grain harvested in 1 hour of basic time. The methodological background and mathematical apparatus

Heat and Mass Transfer with Free Convection MHD Flow Past a Vertical Plate Embedded in a Porous Medium

Directory of Open Access Journals (Sweden)

Farhad Ali

2013-01-01

on free convection unsteady magnetohydrodynamic (MHD flow of viscous fluid embedded in a porous medium is presented. The flow in the fluid is induced due to uniform motion of the plate. The dimensionless coupled linear partial differential equations are solved by using Laplace transform method. The solutions that have been obtained are expressed in simple forms in terms of elementary function exp(· and complementary error function erfc(·. They satisfy the governing equations; all imposed initial and boundary conditions and can immediately be reduced to their limiting solutions. The influence of various embedded flow parameters such as the Hartmann number, permeability parameter, Grashof number, dimensionless time, Prandtl number, chemical reaction parameter, Schmidt number, and Soret number is analyzed graphically. Numerical solutions for skin friction, Nusselt number, and Sherwood number are also obtained in tabular forms.

Design optimization by numerical characterization of fluid flow through the valveless diffuser micropumps

Energy Technology Data Exchange (ETDEWEB)

Ahmadian, M T; Mehrabian, Amin [Center of Excellence in Design, Robotics and Automation, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

2006-04-01

Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand how the pump rectification efficiency and optimum diffuser angle depend on these parameters. A set of characteristic curves are constructed which show these dependencies. The application of these curves would have far reaching implications for valveless micropumps design and selection purposes.

Design optimization by numerical characterization of fluid flow through the valveless diffuser micropumps

International Nuclear Information System (INIS)

Ahmadian, M T; Mehrabian, Amin

2006-01-01

Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand how the pump rectification efficiency and optimum diffuser angle depend on these parameters. A set of characteristic curves are constructed which show these dependencies. The application of these curves would have far reaching implications for valveless micropumps design and selection purposes

A methodology to predict the uniformity of double-shell waste slurries based on mixer pump operation

International Nuclear Information System (INIS)

Liljegren, L.M.; Bamberger, J.A.

1992-08-01

Dimensional analysis is used to determine the similarity parameters that describe the uniformity of radioactive slurry wastes to be suspended by mixer pumps. The results of this analysis are applied to the design of scaled experiments that will determine the operating parameters that will ensure an adequately uniform feed stream during waste retrieval from Hanford double-shell tanks. Ten dimensionless parameters describing the slurry mixing process were identified. Of these, three describe purely geometric features, three describe slurry properties only, one is a dimensionless time scale, and three describe important dynamic factors. The three parameters describing the dynamic features are the Reynolds number, which describes the degree of turbulence in the tank; the Froude number, which describes the effects of stratification on the circulation patterns; and the gravitational settling number, which describes the balance between the work done by gravity to cause settling and the work done by the pump to resuspend particles

Design of a Data Catalogue for Perdigão-2017 Field Experiment: Establishing the Relevant Parameters, Post-Processing Techniques and Users Access

Science.gov (United States)

Palma, J. L.; Belo-Pereira, M.; Leo, L. S.; Fernando, J.; Wildmann, N.; Gerz, T.; Rodrigues, C. V.; Lopes, A. S.; Lopes, J. C.

2017-12-01

Perdigão is the largest of a series of wind-mapping studies embedded in the on-going NEWA (New European Wind Atlas) Project. The intensive observational period of the Perdigão field experiment resulted in an unprecedented volume of data, covering several wind conditions through 46 consecutive days between May and June 2017. For researchers looking into specific events, it is time consuming to scrutinise the datasets looking for appropriate conditions. Such task becomes harder if the parameters of interest were not measured directly, instead requiring their computation from the raw datasets. This work will present the e-Science platform developed by University of Porto for the Perdigao dataset. The platform will assist scientists of Perdigao and the larger scientific community in extrapolating the datasets associated to specific flow regimes of interest as well as automatically performing post-processing/filtering operations internally in the platform. We will illustrate the flow regime categories identified in Perdigao based on several parameters such as weather type classification, cloud characteristics, as well as stability regime indicators (Brunt-Väisälä frequency, Scorer parameter, potential temperature inversion heights, dimensionless Richardson and Froude numbers) and wind regime indicators. Examples of some of the post-processing techniques available in the e-Science platform, such as the Savitzky-Golay low-pass filtering technique, will be also presented.

Correlation between mass transfer coefficient kLa and relevant operating parameters in cylindrical disposable shaken bioreactors on a bench-to-pilot scale.

Science.gov (United States)

Klöckner, Wolf; Gacem, Riad; Anderlei, Tibor; Raven, Nicole; Schillberg, Stefan; Lattermann, Clemens; Büchs, Jochen

2013-12-02

Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen kLa and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal kLa correlation. A Respiration Activity Monitoring System (RAMOS) was used to measure kLa values in cylindrical disposable shaken bioreactors and Buckingham's π-Theorem was applied to define a dimensionless equation for kLa. In this way, a scale- and volume-independent kLa correlation was developed and validated in bioreactors with volumes from 2 L to 200 L. The final correlation was used to calculate cultivation parameters at different scales to allow a sufficient oxygen supply of tobacco BY-2 cell suspension cultures. The resulting equation can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters such as the reactor diameter, the shaking frequency, the filling volume, the viscosity, the oxygen diffusion coefficient, the gravitational acceleration or the shaking diameter within an accuracy range of +/- 30%. To our knowledge, this is the first kLa correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale.

Research Article Special Issue

African Journals Online (AJOL)

pc

2017-11-24

Nov 24, 2017 ... Keywords: multiple regression; mathematical model; GIS; Hydrology; ... Mathematical models are called "phenomenological", when they try to stochastic ... The multiple correlation coefficient R is a dimensionless parameter ...

Optimal homotopy asymptotic method for flow and heat transfer of a viscoelastic fluid in an axisymmetric channel with a porous wall.

Science.gov (United States)

Mabood, Fazle; Khan, Waqar A; Ismail, Ahmad Izani Md

2013-01-01

In this article, an approximate analytical solution of flow and heat transfer for a viscoelastic fluid in an axisymmetric channel with porous wall is presented. The solution is obtained through the use of a powerful method known as Optimal Homotopy Asymptotic Method (OHAM). We obtained the approximate analytical solution for dimensionless velocity and temperature for various parameters. The influence and effect of different parameters on dimensionless velocity, temperature, friction factor, and rate of heat transfer are presented graphically. We also compared our solution with those obtained by other methods and it is found that OHAM solution is better than the other methods considered. This shows that OHAM is reliable for use to solve strongly nonlinear problems in heat transfer phenomena.

Quasinormal modes and strong cosmic censorship in near-extremal Kerr-Newman-de Sitter black-hole spacetimes

Science.gov (United States)

Hod, Shahar

2018-05-01

The quasinormal resonant modes of massless neutral fields in near-extremal Kerr-Newman-de Sitter black-hole spacetimes are calculated in the eikonal regime. It is explicitly proved that, in the angular momentum regime a bar >√{1 - 2 Λ bar/4 + Λ bar / 3 }, the black-hole spacetimes are characterized by slowly decaying resonant modes which are described by the compact formula ℑ ω (n) =κ+ ṡ (n + 1/2 ) [here the physical parameters { a bar ,κ+ , Λ bar , n } are respectively the dimensionless angular momentum of the black hole, its characteristic surface gravity, the dimensionless cosmological constant of the spacetime, and the integer resonance parameter]. Our results support the validity of the Penrose strong cosmic censorship conjecture in these black-hole spacetimes.

Scaling Analysis of the Single-Phase Natural Circulation: the Hydraulic Similarity

International Nuclear Information System (INIS)

Yu, Xin-Guo; Choi, Ki-Yong

2015-01-01

These passive safety systems all rely on the natural circulation to cool down the reactor cores during an accident. Thus, a robust and accurate scaling methodology must be developed and employed to both assist in the design of a scaled-down test facility and guide the tests in order to mimic the natural circulation flow of its prototype. The natural circulation system generally consists of a heat source, the connecting pipes and several heat sinks. Although many applauding scaling methodologies have been proposed during last several decades, few works have been dedicated to systematically analyze and exactly preserve the hydraulic similarity. In the present study, the hydraulic similarity analyses are performed at both system and local level. By this mean, the scaling criteria for the exact hydraulic similarity in a full-pressure model have been sought. In other words, not only the system-level but also the local-level hydraulic similarities are pursued. As the hydraulic characteristics of a fluid system is governed by the momentum equation, the scaling analysis starts with it. A dimensionless integral loop momentum equation is derived to obtain the dimensionless numbers. In the dimensionless momentum equation, two dimensionless numbers, the dimensionless flow resistance number and the dimensionless gravitational force number, are identified along with a unique hydraulic time scale, characterizing the system hydraulic response. A full-height full-pressure model is also made to see which model among the full-height model and reduced-height model can preserve the hydraulic behavior of the prototype. From the dimensionless integral momentum equation, a unique hydraulic time scale, which characterizes the hydraulic response of a single-phase natural circulation system, is identified along with two dimensionless parameters: the dimensionless flow resistance number and the dimensionless gravitational force number. By satisfying the equality of both dimensionless numbers

Scaling Analysis of the Single-Phase Natural Circulation: the Hydraulic Similarity

Energy Technology Data Exchange (ETDEWEB)

Yu, Xin-Guo; Choi, Ki-Yong [KAERI, Daejeon (Korea, Republic of)

2015-05-15

These passive safety systems all rely on the natural circulation to cool down the reactor cores during an accident. Thus, a robust and accurate scaling methodology must be developed and employed to both assist in the design of a scaled-down test facility and guide the tests in order to mimic the natural circulation flow of its prototype. The natural circulation system generally consists of a heat source, the connecting pipes and several heat sinks. Although many applauding scaling methodologies have been proposed during last several decades, few works have been dedicated to systematically analyze and exactly preserve the hydraulic similarity. In the present study, the hydraulic similarity analyses are performed at both system and local level. By this mean, the scaling criteria for the exact hydraulic similarity in a full-pressure model have been sought. In other words, not only the system-level but also the local-level hydraulic similarities are pursued. As the hydraulic characteristics of a fluid system is governed by the momentum equation, the scaling analysis starts with it. A dimensionless integral loop momentum equation is derived to obtain the dimensionless numbers. In the dimensionless momentum equation, two dimensionless numbers, the dimensionless flow resistance number and the dimensionless gravitational force number, are identified along with a unique hydraulic time scale, characterizing the system hydraulic response. A full-height full-pressure model is also made to see which model among the full-height model and reduced-height model can preserve the hydraulic behavior of the prototype. From the dimensionless integral momentum equation, a unique hydraulic time scale, which characterizes the hydraulic response of a single-phase natural circulation system, is identified along with two dimensionless parameters: the dimensionless flow resistance number and the dimensionless gravitational force number. By satisfying the equality of both dimensionless numbers

Maximally Rotating Supermassive Stars at the Onset of Collapse: The Perturbative Effects of Gas Pressure, Magnetic Fields, Dark Matter and Dark Energy

Science.gov (United States)

Butler, Satya P.; Lima, Alicia R.; Baumgarte, Thomas W.; Shapiro, Stuart L.

2018-04-01

The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors - supermassive stars - become unstable to gravitational collapse. For uniformly rotating stars supported by pure radiation pressure and spinning at the mass-shedding limit, the critical configuration at the onset of collapse is characterized by universal values of the dimensionless spin and radius parameters J/M2 and R/M, independent of mass M. We consider perturbative effects of gas pressure, magnetic fields, dark matter and dark energy on these parameters, and thereby determine the domain of validity of this universality. We obtain leading-order corrections for the critical parameters and establish their scaling with the relevant physical parameters. We compare two different approaches to approximate the effects of gas pressure, which plays the most important role, find identical results for the above dimensionless parameters, and also find good agreement with recent numerical results.

OFF-DESIGN OPERATION OF IMPELLER OF THE CENTRIFUGAL COMPRESSOR

Directory of Open Access Journals (Sweden)

Saim KOÇAK

2004-02-01

Full Text Available Inducer and discharge dimensions of impellers of centrifugal compressor are determined as a preliminary design. Blockage factor and inducer dimensionless mass flow are exercised in relation with the relative Mach number. The equation which will be based o off-design calculation, related with the discharge relative Mach number are iterated until it will equal to inducer dimensionless mass flow rate. Then discharge relative Mach number for off-design works is obtained. The results calculated in accordance with pressure, temperature and density are seen to be similar with the theoretical parameters.

Study of Nonlinear MHD Tribological Squeeze Film at Generalized Magnetic Reynolds Numbers Using DTM.

Science.gov (United States)

Rashidi, Mohammad Mehdi; Freidoonimehr, Navid; Momoniat, Ebrahim; Rostami, Behnam

2015-01-01

In the current article, a combination of the differential transform method (DTM) and Padé approximation method are implemented to solve a system of nonlinear differential equations modelling the flow of a Newtonian magnetic lubricant squeeze film with magnetic induction effects incorporated. Solutions for the transformed radial and tangential momentum as well as solutions for the radial and tangential induced magnetic field conservation equations are determined. The DTM-Padé combined method is observed to demonstrate excellent convergence, stability and versatility in simulating the magnetic squeeze film problem. The effects of involved parameters, i.e. squeeze Reynolds number (N1), dimensionless axial magnetic force strength parameter (N2), dimensionless tangential magnetic force strength parameter (N3), and magnetic Reynolds number (Rem) are illustrated graphically and discussed in detail. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems and biological prosthetics.

Study of Nonlinear MHD Tribological Squeeze Film at Generalized Magnetic Reynolds Numbers Using DTM.

Directory of Open Access Journals (Sweden)

Mohammad Mehdi Rashidi

Full Text Available In the current article, a combination of the differential transform method (DTM and Padé approximation method are implemented to solve a system of nonlinear differential equations modelling the flow of a Newtonian magnetic lubricant squeeze film with magnetic induction effects incorporated. Solutions for the transformed radial and tangential momentum as well as solutions for the radial and tangential induced magnetic field conservation equations are determined. The DTM-Padé combined method is observed to demonstrate excellent convergence, stability and versatility in simulating the magnetic squeeze film problem. The effects of involved parameters, i.e. squeeze Reynolds number (N1, dimensionless axial magnetic force strength parameter (N2, dimensionless tangential magnetic force strength parameter (N3, and magnetic Reynolds number (Rem are illustrated graphically and discussed in detail. Applications of the study include automotive magneto-rheological shock absorbers, novel aircraft landing gear systems and biological prosthetics.

Numerical study of unsteady MHD oblique stagnation point flow and heat transfer due to an oscillating stream

Science.gov (United States)

Javed, T.; Ghaffari, A.; Ahmad, H.

2016-05-01

The unsteady stagnation point flow impinging obliquely on a flat plate in presence of a uniform applied magnetic field due to an oscillating stream has been studied. The governing partial differential equations are transformed into dimensionless form and the stream function is expressed in terms of Hiemenz and tangential components. The dimensionless partial differential equations are solved numerically by using well-known implicit finite difference scheme named as Keller-box method. The obtained results are compared with those available in the literature. It is observed that the results are in excellent agreement with the previous studies. The effects of pertinent parameters involved in the problem namely magnetic parameter, Prandtl number and impinging angle on flow and heat transfer characteristics are illustrated through graphs. It is observed that the influence of magnetic field strength increases the fluid velocity and by the increase of obliqueness parameter, the skin friction increases.

Entropy generation analysis of a proton exchange membrane fuel cell (PEMFC) with a fermat spiral as a flow distributor

International Nuclear Information System (INIS)

Rangel-Hernandez, V.H.; Damian-Ascencio, C.; Juarez-Robles, D.; Gallegos-Munoz, A.; Zaleta-Aguilar, A.; Plascencia-Mora, H.

2011-01-01

The present paper aims at investigating the main sources of irreversibility in a Proton Exchange Membrane Fuel Cell (PEMFC) using a Fermat spiral as flow distributor and also to direct possible improvements in its design. The numerical analysis is based on a finite volume technique with a SIMPLE algorithm as numerical procedure. In order to have a more complete and rigorous analysis a new dimensionless parameter is proposed here. The parameter represents the ratio of the entropy generation due to mass transfer to the total entropy generation is proposed here. Results demonstrate that the main sources of irreversibility in a fuel cell are the concentration losses for the most part of the operational domain, whereas the heat transfer effect is not dominant. -- Highlights: → PEM Fuel Cell with Fermat Spiral as distributor. → Causes of irreversibilities. → A new dimensionless parameter to determine contribution of mass transfer in entropy generation.

A successful application of homotopy perturbation method for efficiency and effectiveness assessment of longitudinal porous fins

International Nuclear Information System (INIS)

Cuce, Erdem; Cuce, Pinar Mert

2015-01-01

Highlights: • Homotopy perturbation method has been applied to porous fins. • Dimensionless efficiency and effectiveness expressions have been firstly developed. • Effects of porous and convection parameters on thermal analysis have been clarified. • Ratio of porous fin to solid fin heat transfer rate has been given for various cases. • Reliability and practicality of homotopy perturbation method has been illustrated. - Abstract: In our previous works, thermal performance of straight fins with both constant and temperature-dependent thermal conductivity has been investigated in detail and dimensionless analytical expressions of fin efficiency and fin effectiveness have been developed for the first time in literature via homotopy perturbation method. In this study, previous works have been extended to porous fins. Governing equations have been formulated by performing Darcy’s model. Dimensionless temperature distribution along the length of porous fin has been determined as a function of porosity and convection parameters. The ratio of porous fin to solid fin heat transfer rate has also been evaluated as a function of thermo-geometric fin parameter. The results have been compared with those of finite difference method for a specific case and an excellent agreement has been observed. The expressions developed are beneficial for thermal engineers for preliminary assessment of thermophysical systems instead of consuming time in heat conduction problems governed by strongly nonlinear differential equations

The effect of inclined vertical slats on natural convective heat transfer from an isothermal heated vertical plate

International Nuclear Information System (INIS)

Oosthuizen, P.H.; Sun, L.; Naylor, D.

2002-01-01

Natural convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat adiabatic surfaces (termed 'slats') near the heated surface, these surfaces being, in general, inclined to the heated surface. The slats are pivoted about their center-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air, i.e. where air-conditioning is being used, being considered. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Biuniqueness type approximation. Although the flow is in general three-dimensional, the flow over each slat is assumed to be the same and attention can therefore be restricted to flow over a single slat by using repeating boundary conditions. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. The solution has the following parameters: (1) the Rayleigh number (2) the Prandtl number (3) the dimensionless distance of the slat center point (the pivot point) from the surface (4) the dimensionless slat size (5) the dimensionless slat spacing (6) the angle of inclination of the slats. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated surface has been examined. (author)

Modelling and parameter estimation in reactive continuous mixtures: the catalytic cracking of alkanes - part II

Directory of Open Access Journals (Sweden)

F. C. PEIXOTO

1999-09-01

Full Text Available Fragmentation kinetics is employed to model a continuous reactive mixture of alkanes under catalytic cracking conditions. Standard moment analysis techniques are employed, and a dynamic system for the time evolution of moments of the mixture's dimensionless concentration distribution function (DCDF is found. The time behavior of the DCDF is recovered with successive estimations of scaled gamma distributions using the moments time data.

Adhesion and friction in polymer films on solid substrates: conformal sites analysis and corresponding surface measurements.

Science.gov (United States)

An, Rong; Huang, Liangliang; Mineart, Kenneth P; Dong, Yihui; Spontak, Richard J; Gubbins, Keith E

2017-05-21

In this work, we present a statistical mechanical analysis to elucidate the molecular-level factors responsible for the static and dynamic properties of polymer films. This analysis, which we term conformal sites theory, establishes that three dimensionless parameters play important roles in determining differences from bulk behavior for thin polymer films near to surfaces: a microscopic wetting parameter, α wx , defined as the ratio of polymer-substrate interaction to polymer-polymer interaction; a dimensionless film thickness, H*; and dimensionless temperature, T*. The parameter α wx introduced here provides a more fundamental measure of wetting than previous metrics, since it is defined in terms of intermolecular forces and the atomic structure of the substrate, and so is valid at the nanoscale for gas, liquid or solid films. To test this theoretical analysis, we also report atomic force microscopy measurements of the friction coefficient (μ), adhesion force (F A ) and glass transition temperature (T g ) for thin films of two polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), on two planar substrates, graphite and silica. Both the friction coefficient and the glass transition temperature are found to increase as the film thickness decreases, and this increase is more pronounced for the graphite than for the silica surface. The adhesion force is also greater for the graphite surface. The larger effects encountered for the graphite surface are attributed to the fact that the microscopic wetting parameter, α wx , is larger for graphite than for silica, indicating stronger attraction of polymer chains to the graphite surface.

Influence of yield stress on free convective boundary-layer flow of a non-Newtonian nanofluid past a vertical plate in a porous medium

International Nuclear Information System (INIS)

Hady, F. M.; Ibrahim, F. S.; Abdel-Gaied, S. M.; Eid, M. R.

2011-01-01

The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter

Exergoeconomic performance optimization of an endoreversible intercooled regenerative Brayton combined heat and power plant coupled to variable-temperature heat reservoirs

Energy Technology Data Exchange (ETDEWEB)

Yang, Bo; Chen, Lingen; Sun, Fengrui [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

2012-07-01

An endoreversible intercooled regenerative Brayton combined heat and power (CHP) plant model coupled to variable-temperature heat reservoirs is established. The exergoeconomic performance of the CHP plant is investigated using finite time thermodynamics. The analytical formulae about dimensionless profit rate and exergy efficiency of the CHP plant with the heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are deduced. By taking the maximum profit rate as the objective, the heat conductance allocation among the five heat exchangers and the choice of intercooling pressure ratio are optimized by numerical examples, the characteristic of the optimal dimensionless profit rate versus corresponding exergy efficiency is investigated. When the optimization is performed further with respect to the total pressure ratio, a double-maximum profit rate is obtained. The effects of the design parameters on the double-maximum dimensionless profit rate and corresponding exergy efficiency, optimal total pressure ratio and optimal intercooling pressure ratio are analyzed in detail, and it is found that there exist an optimal consumer-side temperature and an optimal thermal capacitance rate matching between the working fluid and the heat reservoir, respectively, corresponding to a thrice-maximum dimensionless profit rate.

Coexistence properties of the Redlich-Kwong model for a fluid

International Nuclear Information System (INIS)

Pina, Eduardo; Selva, Sara MarIa Teresa de la

2006-01-01

It is shown in this paper that for pure substances obeying the van der Waals (VdW) equation of state (EOS) or Redlich-Kwong (RK) type equations of state below the critical temperature, it is possible to obtain with the help of the Maxwell equal areas rule the vapour pressure curve, the difference between the molar volume of the vapour and of the liquid, and the difference between the molar entropies of vapour and liquid; each property is obtained in the first step as a dimensionless expression, function of a dimensionless temperature. Any particular property of a particular fluid obeying VdW EOS or one type of RK EOS can be obtained from the corresponding dimensionless expression by multiplying it with a dimension unit which is a function of the particular temperature-dependent parameter a(T) of the EOS considered for the fluid. In the cases of VdW and the original RK (EOS), the dimensionless functions are unique for all the pure fluids that obey the EOS under consideration. A comparison of VdW, RK and RK-Soave (SRK) predictions with experimental vapour pressure data is exemplified for carbon dioxide

Vacuum drying of apples (cv. Golden Delicious): drying characteristics, thermodynamic properties, and mass transfer parameters

Science.gov (United States)

Nadi, Fatemeh; Tzempelikos, Dimitrios

2018-01-01

In this work, apples of cv. Golden Delicious were cut into slices that were 5 and 7 mm thick and then vacuum dried at 50, 60 and 70 °C and pressure of 0.02 bar. The thin layer model drying kinetics was studied, and mass transfer properties, specifically effective moisture diffusivity and convective mass transfer coefficient, were evaluated using the Fick's equation of diffusion. Also, thermodynamic parameters of the process, i.e. enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG), were determined. Colour properties were evaluated as one of the important indicators of food quality and marketability. Determination of mass transfer parameters and thermodynamic properties of vacuum dried apple slices has not been discussed much in the literature. In conclusion, the Nadi's model fitted best the observed data that represent the drying process. Thermodynamic properties were determined based on the dependence of the drying constant of the Henderson and Pabis model on temperature, and it was concluded that the variation in drying kinetics depends on the energy contribution of the surrounding environment. The enthalpy and entropy diminished, while the Gibbs free energy increased with the increase of the temperature of drying; therefore, it was possible to verify that variation in the diffusion process in the apple during drying depends on energetic contributions of the environment. The obtained results showed that diffusivity increased for 69%, while the mass transfer coefficient increase was even higher, 75%, at the variation of temperature of 20 °C. The increase in the dimensionless Biot number was 20%.

Characterization of rarefaction waves in van der Waals fluids

Science.gov (United States)

Yuen, Albert; Barnard, John J.

2015-12-01

We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015), 10.1103/PhysRevE.92.033019] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy.

Non-Darcy Mixed Convection in a Doubly Stratified Porous Medium with Soret-Dufour Effects

Directory of Open Access Journals (Sweden)

D. Srinivasacharya

2014-01-01

Full Text Available This paper presents the nonsimilarity solutions for mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a doubly stratified fluid saturated porous medium in the presence of Soret and Dufour effects. The flow in the porous medium is described by employing the Darcy-Forchheimer based model. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms and then solved numerically. The influence of pertinent parameters on dimensionless velocity, temperature, concentration, heat, and mass transfer in terms of the local Nusselt and Sherwood numbers is discussed and presented graphically.

Thermoelectric generator performance analysis: Influence of pin tapering on the first and second law efficiencies

International Nuclear Information System (INIS)

Yilbas, B.S.; Ali, H.

2015-01-01

Highlights: • Double tapering of thermoelectric elements improves first and second law efficiency. • Pin geometric feature maximizing device output work does not maximize thermal efficiency. • Pin geometric feature maximizing first law efficiency slight alters for maximum second law efficiency. • External resistance and operating temperature ratios influence design configuration of thermoelectric generator. - Abstract: Thermoelectric generators are the important candidates for clean energy conversion from the waste heat; however, their low efficiency limits the practical applications of the devices. Tailoring the geometric configuration of the device in line with the operating conditions can improve the device performance. Consequently; in the present study, the influence of the pin geometric configuration on the thermoelectric generator performance is investigated. The dimensionless tapering parameter is introduced and its effect on the first and second law efficiencies is examined for various operating conditions including the external load resistance and the temperature ratio. It is found that the first and second law efficiencies are significantly influenced by the pin geometry. The dimensionless tapering parameter (a), increasing tapering of the thermoelectric pins, within the range of 2 ⩽ a ⩽ 4 results in improved first and second law efficiencies. However, the dimensionless tapering parameter maximizing the first and second law efficiencies does not maximize the device output power. This behavior is associated with the external load resistance which has a considerable influence on the device output power such that increasing external load resistance lowers the device output power

Coupling of electromagnetics and structural/fluid dynamics - application to the dual coolant blanket subjected to plasma disruptions

International Nuclear Information System (INIS)

Jordan, T.

1996-01-01

Some aspects concerning the coupling of quasi-stationary electromagnetics and the dynamics of structure and fluid are investigated. The necessary equations are given in a dimensionless form. The dimensionless parameters in these equations are used to evaluate the importance of the different coupling effects. A finite element formulation of the eddy-current damping in solid structures is developed. With this formulation, an existing finite element method (FEM) structural dynamics code is extended and coupled to an FEM eddy-current code. With this program system, the influence of the eddy-current damping on the dynamic loading of the dual coolant blanket during a centered plasma disruption is determined. The analysis proves that only in loosely fixed or soft structures will eddy-current damping considerably reduce the resulting stresses. Additionally, the dynamic behavior of the liquid metal in the blankets' poloidal channels is described with a simple two-dimensional magnetohydrodynamic approach. The analysis of the dimensionless parameters shows that for small-scale experiments, which are designed to model the coupled electromagnetic and structural/fluid dynamic effects in such a blanket, the same magnetic fields must be applied as in the real fusion device. This will be the easiest way to design experiments that produce transferable results. 10 refs., 7 figs

Efficient production of hot plasmas through multiple-wire implosion in transmission line generators

International Nuclear Information System (INIS)

Bloomberg, H.W.

1980-01-01

Model equations for the implosion of multiple-wire arrays mounted across the electrodes of a transmission line generator are used to obtain an expression for the energy-coupling efficiency. For a useful class of imploding loads, the efficiency is shown to depend on a single dimensionless parameter. Furthermore, the efficiency curve has a maximum, and this permits an explicit optimization of the wire load parameters in terms of the machine parameters

Thermally radiative three-dimensional flow of Jeffrey nanofluid with internal heat generation and magnetic field

Energy Technology Data Exchange (ETDEWEB)

Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abdullah, Z. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Hayat, T. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan)

2016-01-01

This research work addresses the three-dimensional hydromagnetic flow of Jeffrey fluid with nanoparticles. Flow is generated by a bidirectional stretching surface. The effects of thermal radiation and internal heat generation are encountered in energy expressions. More realistic convective boundary conditions at the surface are employed instead of constant surface temperature and mass species conditions. Boundary layer assumptions lead to the governing non-linear mathematical model. Resulting equations through momentum, energy and mass species are made dimensionless using suitable variables. The solution expressions of dimensionless velocities, temperature and nanoparticle concentration have been computed for the convergent series solutions. The impacts of interesting parameters on the dimensionless quantities are displayed and interpreted. The values of physical quantities are computed and analyzed. - Highlights: • Three-dimensional hydromagnetic flow of Jeffrey nanofluid is considered. • Brownian motion and thermophoresis effects are encountered. • Heat transfer analysis is performed with thermal radiation. • Results are plotted and visualized.

BNS damping of beam breakup instability

International Nuclear Information System (INIS)

Stupakov, G.V.

1997-08-01

The author studies BNS damping of the beam breakup instability in a simple model assuming a constant beam energy, flat bunch distribution, and a smooth transverse focusing. The model allows an analytic solution for a constant and linear wake functions. Scaling dimensionless parameters are derived and the beam dynamics is illustrated for the range of parameters relevant to the Stanford Linear Collider

Critical Magnetic Scattering of Neutrons in Iron

DEFF Research Database (Denmark)

Passell, L.; Blinowski, K.; Brun, T.

1965-01-01

correlations and the dynamics of the spin-ordering process. For the dimensionless parameter 2mΛ/ℏ which describes the time dependence of the spin fluctuations, we obtain the value 11.0±0.6 at T-Tc=2 and 18°C. The zero-field magnetic susceptibility, as determined by the parameters κ1 and r1 (which represent...

A Note on Variable Viscosity and Chemical Reaction Effects on Mixed Convection Heat and Mass Transfer Along a Semi-Infinite Vertical Plate

Directory of Open Access Journals (Sweden)

Mostafa A. A. Mahmoud

2007-01-01

Full Text Available In the present study, an analysis is carried out to study the variable viscosity and chemical reaction effects on the flow, heat, and mass transfer characteristics in a viscous fluid over a semi-infinite vertical porous plate. The governing boundary layer equations are written into a dimensionless form by similarity transformations. The transformed coupled nonlinear ordinary differential equations are solved numerically by using the shooting method. The effects of different parameters on the dimensionless velocity, temperature, and concentration profiles are shown graphically. In addition, tabulated results for the local skin-friction coefficient, the local Nusselt number, and the local Sherwood number are presented and discussed.

MHD flow of a micropolar fluid over a stretchable disk in a porous medium with heat and mass transfer

Directory of Open Access Journals (Sweden)

A. Rauf

2015-07-01

Full Text Available This article studies the simultaneous impacts of heat and mass transfer of an incompressible electrically conducting micropolar fluid generated by the stretchable disk in presence of porous medium. The thermal radiation effect is accounted via Rosseland’s approximation. The governing boundary layer equations are reduced into dimensionless form by employing the suitable similarity transformations. A finite difference base algorithm is utilized to obtain the solution expressions. The impacts of physical parameters on dimensionless axial velocity, radial velocity, micro-rotation, temperature and concentrations profiles are presented and examined carefully. Numerical computation is performed to compute shear stress, couple stress, heat and mass rate at the disk.

MHD flow of a micropolar fluid over a stretchable disk in a porous medium with heat and mass transfer

Energy Technology Data Exchange (ETDEWEB)

Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk; Meraj, M. A. [Department of Mathematics, CIIT Sahiwal 57000 (Pakistan); Ashraf, M.; Batool, K. [Department of CASPAM, Bahauddin Zakariya University, Multan 63000 (Pakistan); Hussain, M. [Department of Sciences & Humanities, National University of computer & Emerging Sciences, Islamabad 44000 (Pakistan)

2015-07-15

This article studies the simultaneous impacts of heat and mass transfer of an incompressible electrically conducting micropolar fluid generated by the stretchable disk in presence of porous medium. The thermal radiation effect is accounted via Rosseland’s approximation. The governing boundary layer equations are reduced into dimensionless form by employing the suitable similarity transformations. A finite difference base algorithm is utilized to obtain the solution expressions. The impacts of physical parameters on dimensionless axial velocity, radial velocity, micro-rotation, temperature and concentrations profiles are presented and examined carefully. Numerical computation is performed to compute shear stress, couple stress, heat and mass rate at the disk.

ADRC for spacecraft attitude and position synchronization in libration point orbits

Science.gov (United States)

Gao, Chen; Yuan, Jianping; Zhao, Yakun

2018-04-01

This paper addresses the problem of spacecraft attitude and position synchronization in libration point orbits between a leader and a follower. Using dual quaternion, the dimensionless relative coupled dynamical model is derived considering computation efficiency and accuracy. Then a model-independent dimensionless cascade pose-feedback active disturbance rejection controller is designed to spacecraft attitude and position tracking control problems considering parameter uncertainties and external disturbances. Numerical simulations for the final approach phase in spacecraft rendezvous and docking and formation flying are done, and the results show high-precision tracking errors and satisfactory convergent rates under bounded control torque and force which validate the proposed approach.

Analogy of convective heat transfer between developing laminar secondary flows in pipes

OpenAIRE

Ishigaki, Hiroshi; 石垣　博

1998-01-01

Analogy of convective heat transfer between developing laminar flows in curved pipes and orthogonally rotating pipes is described through similarity arguments and numerical computation. Governing parameters and a dimensionless axial distance are properly used for the respective flows. When the second parameter is large in each flow, it is shown that the temperature profiles and the Nusselt numbers of the two flows are approximately similar for the same values of the governing parameter, Prand...

Modelling extrudate expansion in a twin-screw food extrusion cooking process through dimensional analysis methodology

DEFF Research Database (Denmark)

Cheng, Hongyuan; Friis, Alan

2010-01-01

A new phenomenological model is proposed to correlate extrudate expansion and extruder operation parameters in a twin-screw food extrusion cooking process. Buckingham's pi dimensional analysis method is applied to establish the model. Three dimensionless groups, i.e. pump efficiency, water content...

Oscillatory electroosmotic flow in a parallel-plate microchannel under asymmetric zeta potentials

Science.gov (United States)

Peralta, M.; Arcos, J.; Méndez, F.; Bautista, O.

2017-06-01

In this work, we conduct a theoretical analysis of the start-up of an oscillatory electroosmotic flow (EOF) in a parallel-plate microchannel under asymmetric zeta potentials. It is found that the transient evolution of the flow field is controlled by the parameters {R}ω , {R}\\zeta , and \\bar{κ }, which represent the dimensionless frequency, the ratio of the zeta potentials of the microchannel walls, and the electrokinetic parameter, which is defined as the ratio of the microchannel height to the Debye length. The analysis is performed for both low and high zeta potentials; in the former case, an analytical solution is derived, whereas in the latter, a numerical solution is obtained. These solutions provide the fundamental characteristics of the oscillatory EOFs for which, with suitable adjustment of the zeta potential and the dimensionless frequency, the velocity profiles of the fluid flow exhibit symmetric or asymmetric shapes.

Chirality Quantum Phase Transition in Noncommutative Dirac Oscillator

International Nuclear Information System (INIS)

Wang Shao-Hua; Hou Yu-Long; Jing Jian; Wang Qing; Long Zheng-Wen

2014-01-01

The charged Dirac oscillator on a noncommutative plane coupling to a uniform perpendicular magnetic held is studied in this paper. We map the noncommutative plane to a commutative one by means of Bopp shift and study this problem on the commutative plane. We find that this model can be mapped onto a quantum optics model which contains Anti—Jaynes—Cummings (AJC) or Jaynes—Cummings (JC) interactions when a dimensionless parameter ζ (which is the function of the intensity of the magnetic held) takes values in different regimes. Furthermore, this model behaves as experiencing a chirality quantum phase transition when the dimensionless parameter ζ approaches the critical point. Several evidences of the chirality quantum phase transition are presented. We also study the non-relativistic limit of this model and find that a similar chirality quantum phase transition takes place in its non-relativistic limit. (physics of elementary particles and fields)

Sediment transport modeling in deposited bed sewers: unified form of May's equations using the particle swarm optimization algorithm.

Science.gov (United States)

Safari, Mir Jafar Sadegh; Shirzad, Akbar; Mohammadi, Mirali

2017-08-01

May proposed two dimensionless parameters of transport (η) and mobility (F s ) for self-cleansing design of sewers with deposited bed condition. The relationships between those two parameters were introduced in conditional form for specific ranges of F s , which makes it difficult to use as a practical tool for sewer design. In this study, using the same experimental data used by May and employing the particle swarm optimization algorithm, a unified equation is recommended based on η and F s . The developed model is compared with original May relationships as well as corresponding models available in the literature. A large amount of data taken from the literature is used for the models' evaluation. The results demonstrate that the developed model in this study is superior to May and other existing models in the literature. Due to the fact that in May's dimensionless parameters more effective variables in the sediment transport process in sewers with deposited bed condition are considered, it is concluded that the revised May equation proposed in this study is a reliable model for sewer design.

Comprehensive performance analyses and optimization of the irreversible thermodynamic cycle engines (TCE) under maximum power (MP) and maximum power density (MPD) conditions

International Nuclear Information System (INIS)

Gonca, Guven; Sahin, Bahri; Ust, Yasin; Parlak, Adnan

2015-01-01

This paper presents comprehensive performance analyses and comparisons for air-standard irreversible thermodynamic cycle engines (TCE) based on the power output, power density, thermal efficiency, maximum dimensionless power output (MP), maximum dimensionless power density (MPD) and maximum thermal efficiency (MEF) criteria. Internal irreversibility of the cycles occurred during the irreversible-adiabatic processes is considered by using isentropic efficiencies of compression and expansion processes. The performances of the cycles are obtained by using engine design parameters such as isentropic temperature ratio of the compression process, pressure ratio, stroke ratio, cut-off ratio, Miller cycle ratio, exhaust temperature ratio, cycle temperature ratio and cycle pressure ratio. The effects of engine design parameters on the maximum and optimal performances are investigated. - Highlights: • Performance analyses are conducted for irreversible thermodynamic cycle engines. • Comprehensive computations are performed. • Maximum and optimum performances of the engines are shown. • The effects of design parameters on performance and power density are examined. • The results obtained may be guidelines to the engine designers

Accurate evaluation for the biofilm-activated sludge reactor using graphical techniques

Science.gov (United States)

Fouad, Moharram; Bhargava, Renu

2018-05-01

A complete graphical solution is obtained for the completely mixed biofilm-activated sludge reactor (hybrid reactor). The solution consists of a series of curves deduced from the principal equations of the hybrid system after converting them in dimensionless form. The curves estimate the basic parameters of the hybrid system such as suspended biomass concentration, sludge residence time, wasted mass of sludge, and food to biomass ratio. All of these parameters can be expressed as functions of hydraulic retention time, influent substrate concentration, substrate concentration in the bulk, stagnant liquid layer thickness, and the minimum substrate concentration which can maintain the biofilm growth in addition to the basic kinetics of the activated sludge process in which all these variables are expressed in a dimensionless form. Compared to other solutions of such system these curves are simple, easy to use, and provide an accurate tool for analyzing such system based on fundamental principles. Further, these curves may be used as a quick tool to get the effect of variables change on the other parameters and the whole system.

Parametric Studies of Flat Plate Trajectories Using VIC and Penalization

Directory of Open Access Journals (Sweden)

François Morency

2018-01-01

Full Text Available Flying debris is generated in several situations: when a roof is exposed to a storm, when ice accretes on rotating wind turbines, or during inflight aircraft deicing. Four dimensionless parameters play a role in the motion of flying debris. The goal of the present paper is to investigate the relative importance of four dimensionless parameters: the Reynolds number, the Froude number, the Tachikawa number, and the mass moment of inertia parameters. Flying debris trajectories are computed with a fluid-solid interaction model formulated for an incompressible 2D laminar flow. The rigid moving solid effects are modelled in the Navier-Stokes equations using penalization. A VIC scheme is used to solve the flow equations. The aerodynamic forces and moments are used to compute the acceleration and the velocity of the solid. A database of 64 trajectories is built using a two-level full factorial design for the four factors. The dispersion of the plate position at a given horizontal position decreases with the Froude number. Moreover, the Tachikawa number has a significant effect on the median plate position.

Prediction of EMP cavitation threshold from other than sodium testing

International Nuclear Information System (INIS)

Kambe, M.; Kamei, M.

2002-01-01

An experimental study has been performed to predict the cavitation threshold of electromagnetic pumps from measurements on test models using water and alcohol. Cavitation tests were carried out using water and alcohol test loop on subscale ducts of transparent acrylic resin with reference to an actual pump (1.1m 3 /min). These data were compared to those obtained from the in-sodium tests on the actual pump. The investigation revealed that the value of Thoma's dimensionless parameter: σ applied to the test model for water and alcohol is quite higher than that of corresponding σ on the actual pump. To minimize the incipient cavitation safety margin, more accurate prediction must be required. In view of this, the authors proposed the dimensionless parameter: σ T =σ/W-bare where W-bare denotes the Weber number. This parameter was confirmed to predict the cavitation threshold of electromagnetic pumps with much more accuracy than ever before. It can also be adopted to predict cavitation threshold of other FBR components. (author)

Comparison between predicted and observed sand waves and sand banks in the North Sea

NARCIS (Netherlands)

Hulscher, Suzanne J.M.H.; van den Brink, G.M.

2001-01-01

For the first time a prediction model of regular morphological patterns on the seabed was tested against observations of sand wave and sand bank occurrence in the entire North Sea. The model, which originates from first physical principles, predicts this occurrence via two dimensionless parameters

On the misinterpretation of the correlation coefficient in pharmaceutical sciences

DEFF Research Database (Denmark)

Sonnergaard, Jørn

2006-01-01

The correlation coefficient is often used and more often misused as a universal parameter expressing the quality in linear regression analysis. The popularity of this dimensionless quantity is evident as it is easy to communicate and considered to be unproblematic to comprehend. However, illustra...

Effects of chemical reaction on moving isothermal vertical plate with variable mass diffusion

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2003-01-01

Full Text Available An exact solution to the problem of flow past an impulsively started infinite vertical isothermal plate with variable mass diffusion is presented here, taking into account of the homogeneous chemical reaction of first-order. The dimensionless governing equations are solved by using the Laplace - transform technique. The velocity and skin-friction are studied for different parameters like chemical reaction parameter, Schmidt number and buoyancy ratio parameter. It is observed that the veloc­ity increases with decreasing chemical reaction parameter and increases with increasing buoyancy ratio parameter.

Unsteady magnetohydrodynamic thermal and diffusion boundary layer from a horizontal circular cylinder

Directory of Open Access Journals (Sweden)

Boričić Aleksandar Z.

2016-01-01

Full Text Available The unsteady 2-D dynamic, thermal, and diffusion magnetohydrodynamic laminar boundary layer flow over a horizontal cylinder of incompressible and electrical conductivity fluid, in mixed convection in the presence of heat source or sink and chemical reactions. The present magnetic field is homogenous and perpendicular to the body surface. It is assumed that induction of outer magnetic field is a function of longitudinal co-ordinate outer electric field is neglected and magnetic Reynolds number is significantly lower than one, i. e. considered the problem is in approximation without induction. Fluid electrical conductivity is constant. Free stream velocity, temperature, and concentration on the body are functions of longitudinal co-ordinate. The developed governing boundary layer equations and associated boundary conditions are made dimensionless using a suitable similarity transformation and similarity parameters. System of non-dimensionless equations is solved using the implicit finite difference three-diagonal and iteration method. Numerical results are obtained and presented for different Prandtl, Eckart, and Schmidt numbers, and values: magnetic parameter, temperature, and diffusion parameters, buoyancy temperature parameters, thermal parameter, and chemical reaction parameter. Variation of velocity profiles, temperature and diffusion distributions, and many integral and differential characteristics, boundary layer, are evaluated numerically for different values of the magnetic field. Transient effects of velocity, temperature and diffusion are analyzed. A part of obtained results is given in the form of figures and corresponding conclusions.

Hydromagnetic flow of third grade nanofluid with viscous dissipation and flux conditions

Energy Technology Data Exchange (ETDEWEB)

Hussain, T. [Faculty of Computing, Mohammad Ali Jinnah University, Islamabad 44000 (Pakistan); Shehzad, S. A., E-mail: ali-qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Hayat, T. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Alsaedi, A. [Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2015-08-15

This article investigates the magnetohydrodynamic flow of third grade nanofluid with thermophoresis and Brownian motion effects. Energy equation is considered in the presence of thermal radiation and viscous dissipation. Rosseland’s approximation is employed for thermal radiation. The heat and concentration flux conditions are taken into account. The governing nonlinear mathematical expressions of velocity, temperature and concentration are converted into dimensionless expressions via transformations. Series solutions of the dimensionless velocity, temperature and concentration are developed. Convergence of the constructed solutions is checked out both graphically and numerically. Effects of interesting physical parameters on the temperature and concentration are plotted and discussed in detail. Numerical values of skin-friction coefficient are computed for the hydrodynamic and hydromagnetic flow cases.

Thermal radiation and mass transfer effects on unsteady MHD free convection flow past a vertical oscillating plate

Science.gov (United States)

Rana, B. M. Jewel; Ahmed, Rubel; Ahmmed, S. F.

2017-06-01

Unsteady MHD free convection flow past a vertical porous plate in porous medium with radiation, diffusion thermo, thermal diffusion and heat source are analyzed. The governing non-linear, partial differential equations are transformed into dimensionless by using non-dimensional quantities. Then the resultant dimensionless equations are solved numerically by applying an efficient, accurate and conditionally stable finite difference scheme of explicit type with the help of a computer programming language Compaq Visual Fortran. The stability and convergence analysis has been carried out to establish the effect of velocity, temperature, concentration, skin friction, Nusselt number, Sherwood number, stream lines and isotherms line. Finally, the effects of various parameters are presented graphically and discussed qualitatively.

THEORETICAL AND EXPERIMENTAL ANALYSIS OF A CROSS-FLOW HEAT EXCHANGER

Directory of Open Access Journals (Sweden)

R. Tuğrul OĞULATA

1996-03-01

Full Text Available In this study, cross-flow plate type heat exchanger has been investigated because of its effective use in waste heat recovery systems. For this purpose, a heat regain system has been investigated and manufactured in laboratory conditions. Manufactured heat exchanger has been tested with an applicable experimental set up and temperatures, velocity of the air and the pressure losses occuring in the system have been measured and the efficiency of the system has been determined. The irreversibility of heat exchanger has been taken into consideration while the design of heat exchanger is being performed. So minimum entropy generation number has been analysied with respect to second law of thermodynamics in cross-flow heat exchanger. The minimum entropy generation number depends on parameters called optimum flow path length, dimensionless mass velocity and dimensionless heat transfer area. Variations of entropy generation number with these parameters have been analysied and introduced their graphics with their comments.

Non-linear time series analysis on flow instability of natural circulation under rolling motion condition

International Nuclear Information System (INIS)

Zhang, Wenchao; Tan, Sichao; Gao, Puzhen; Wang, Zhanwei; Zhang, Liansheng; Zhang, Hong

2014-01-01

Highlights: • Natural circulation flow instabilities in rolling motion are studied. • The method of non-linear time series analysis is used. • Non-linear evolution characteristic of flow instability is analyzed. • Irregular complex flow oscillations are chaotic oscillations. • The effect of rolling parameter on the threshold of chaotic oscillation is studied. - Abstract: Non-linear characteristics of natural circulation flow instabilities under rolling motion conditions were studied by the method of non-linear time series analysis. Experimental flow time series of different dimensionless power and rolling parameters were analyzed based on phase space reconstruction theory. Attractors which were reconstructed in phase space and the geometric invariants, including correlation dimension, Kolmogorov entropy and largest Lyapunov exponent, were determined. Non-linear characteristics of natural circulation flow instabilities under rolling motion conditions was studied based on the results of the geometric invariant analysis. The results indicated that the values of the geometric invariants first increase and then decrease as dimensionless power increases which indicated the non-linear characteristics of the system first enhance and then weaken. The irregular complex flow oscillation is typical chaotic oscillation because the value of geometric invariants is at maximum. The threshold of chaotic oscillation becomes larger as the rolling frequency or rolling amplitude becomes big. The main influencing factors that influence the non-linear characteristics of the natural circulation system under rolling motion are thermal driving force, flow resistance and the additional forces caused by rolling motion. The non-linear characteristics of the natural circulation system under rolling motion changes caused by the change of the feedback and coupling degree among these influencing factors when the dimensionless power or rolling parameters changes

On the use of dimensionless parameters in acid-base theory: VI. The buffer capacities of equimolar binary mixtures of monovalent weak protolytes as compared to that of bivalent protolytes.

Science.gov (United States)

Rilbe, H

1994-05-01

The general equation for the relative molar buffer capacity, earlier shown to be valid for bivalent acids, bases, and ampholytes, is shown to hold also for equimolar, binary mixtures of monovalent protolytes if only the parameter s = square root of K1'/4K2' is exchanged for t = s + 1/4s. The same applies to the equations for the mean valence of the two classes of protolytes. As a consequence thereof, the titration and buffer capacity curves of a bivalent protolyte are identical with those of a monovalent protolyte with a pK' value equal to the with those of a monovalent protolyte with a pK' value equal to square root of K1'K2' of the bivalent one (the isoprotic point of an ampholyte). For a hypothetical bivalent acid, base, or ampholyte with s = 1, delta pK' = log 4, this implies that the intrinsic rather than the hybrid dissociation constants are responsible for the titration and buffer capacity curves.

Prediction of 222 Rn exhalation rates from phosphogypsum based stacks. Part I: parametric mathematical modeling

International Nuclear Information System (INIS)

Rabi, Jose A.; Mohamad, Abdulmajeed A.

2004-01-01

Radon-222 is a radionuclide exhaled from phosphogypsum by-produced at phosphate fertilizer industries. Alternative large-scale application of this waste may indicate a material substitute for civil engineering provided that environmental issues concerning its disposal and management are overcome. The first part of this paper outlines a steady-state two-dimensional model for 222 Rn transport through porous media, inside which emanation (source term) and decay (sink term) exist. Boussinesq approach is evoked for the laminar buoyancy-driven interstitial air flow, which is also modeled according to Darcy-Brinkman formulation. In order to account for simultaneous effects of entailed physical parameters, governing equations are cast into dimensionless form. Apart from usual controlling parameters like Reynolds, Prandtl, Schmidt, Grashof and Darcy numbers, three unconventional dimensionless groups are put forward. Having in mind 222 Rn transport in phosphogypsum-bearing porous media, the physical meaning of those newly introduced parameters and representative values for the involved physical parameters are presented. A limiting diffusion-dominated scenario is addressed, for which an analytical solution is deduced for boundary conditions including an impermeable phosphogypsum stack base and a non-zero fixed concentration activity at the stack top. Accordingly, an expression for the average Sherwood number corresponding to the normalized 222 Rn exhalation rate is presented

A numerical study of the rolling friction between a microsphere and a substrate considering the adhesive effect

International Nuclear Information System (INIS)

Zhang, Yuyan; Wang, Xiaoli; Yang, Weixu; Li, Hanqing

2016-01-01

A numerical model of the rolling friction between a microsphere and a substrate is established by introducing the adhesion hysteresis between the front and rear sides of the contact region into Zhang’s adhesive contact model. Effects of the size ratio which is defined as the sphere radius divided by the equilibrium separation, relative amount of adhesion hysteresis and Tabor parameter on the dimensionless maximum rolling friction torque in the case of zero normal force are inspected, and the quantitative relationship between the maximum rolling friction torque and the normal force is achieved. Results indicate that due to adhesion hysteresis at microscale, the dimensionless maximum rolling friction torque at zero normal force is not zero, which not only increases with decreasing size ratio, showing clear size effects, but also increases with increasing relative amount of adhesion hysteresis and Tabor parameter. In addition, the maximum rolling friction torque at microscale presents a sublinear relationship with the normal force, and the exponent of the normal force is influenced by the size ratio, relative amount of adhesion hysteresis and Tabor parameter, which are remarkably different from the superlinear relationship at macroscale. (paper)

Investigation of the microwave emission from the PRETEXT tokamak

International Nuclear Information System (INIS)

Gandy, R.F.

1981-10-01

A study of the microwave emission from the PRETEXT tokamak has been conducted. Two types of emission have been observed: electron cyclotron and electron plasma frequency. Three general emission regimes have been identified. These regimes are best classified by the dimensionless parameter α, where α = ω/sub pe//Ω/sub e/

The Radio And Very Low Frequency (VLF) Electromagnetic ...

African Journals Online (AJOL)

The Radio And Very Low Frequency (VLF) Electromagnetic Response Of A Layered Earth Media With Variable Dielectric Permittivity. ... A radio frequency of 125 KHz and a very low frequency (VLF) of 20 KHz were used in the computations and the field parameters studied over a dimensionless induction number, B. The ...

Thermodynamic optimization of ground heat exchangers with single U-tube by entropy generation minimization method

International Nuclear Information System (INIS)

Li Min; Lai, Alvin C.K.

2013-01-01

Highlights: ► A second-law-based analysis is performed for single U-tube ground heat exchangers. ► Two expressions for the optimal length and flow velocity are developed for GHEs. ► Empirical velocities of GHEs are large compared to thermodynamic optimum values. - Abstract: This paper investigates thermodynamic performance of borehole ground heat exchangers with a single U-tube by the entropy generation minimization method which requires information of heat transfer and fluid mechanics, in addition to thermodynamics analysis. This study first derives an expression for dimensionless entropy generation number, a function that consists of five dimensionless variables, including Reynolds number, dimensionless borehole length, scale factor of pressures, and two duty parameters of ground heat exchangers. The derivation combines a heat transfer model and a hydraulics model for borehole ground heat exchangers with the first law and the second law of thermodynamics. Next, the entropy generation number is minimized to produce two analytical expressions for the optimal length and the optimal flow velocity of ground heat exchangers. Then, this paper discusses and analyzes implications and applications of these optimization formulas with two case studies. An important finding from the case studies is that widely used empirical velocities of circulating fluid are too large to operate ground-coupled heat pump systems in a thermodynamic optimization way. This paper demonstrates that thermodynamic optimal parameters of ground heat exchangers can probably be determined by using the entropy generation minimization method.

Dimensional analysis of detrimental ozone generation by positive wire-to-plate corona discharge in air

Science.gov (United States)

Bo, Z.; Chen, J. H.

2010-02-01

The dimensional analysis technique is used to formulate a correlation between ozone generation rate and various parameters that are important in the design and operation of positive wire-to-plate corona discharges in indoor air. The dimensionless relation is determined by linear regression analysis based on the results from 36 laboratory-scale experiments. The derived equation is validated by experimental data and a numerical model published in the literature. Applications of such derived equation are illustrated through an example selection of the appropriate set of operating conditions in the design/operation of a photocopier to follow the federal regulations of ozone emission. Finally, a new current-voltage characteristic equation is proposed for positive wire-to-plate corona discharges based on the derived dimensionless equation.

Dimensional analysis of detrimental ozone generation by positive wire-to-plate corona discharge in air

International Nuclear Information System (INIS)

Bo, Z; Chen, J H

2010-01-01

The dimensional analysis technique is used to formulate a correlation between ozone generation rate and various parameters that are important in the design and operation of positive wire-to-plate corona discharges in indoor air. The dimensionless relation is determined by linear regression analysis based on the results from 36 laboratory-scale experiments. The derived equation is validated by experimental data and a numerical model published in the literature. Applications of such derived equation are illustrated through an example selection of the appropriate set of operating conditions in the design/operation of a photocopier to follow the federal regulations of ozone emission. Finally, a new current-voltage characteristic equation is proposed for positive wire-to-plate corona discharges based on the derived dimensionless equation.

Monte Carlo studies of diamagnetism and charge density wave order in the cuprate pseudogap regime

Science.gov (United States)

Hayward Sierens, Lauren; Achkar, Andrew; Hawthorn, David; Melko, Roger; Sachdev, Subir

2015-03-01

The pseudogap regime of the hole-doped cuprate superconductors is often characterized experimentally in terms of a substantial diamagnetic response and, from another point of view, in terms of strong charge density wave (CDW) order. We introduce a dimensionless ratio, R, that incorporates both diamagnetic susceptibility and the correlation length of CDW order, and therefore reconciles these two fundamental characteristics of the pseudogap. We perform Monte Carlo simulations on a classical model that considers angular fluctuations of a six-dimensional order parameter, and compare our Monte Carlo results for R with existing data from torque magnetometry and x-ray scattering experiments on YBa2Cu3O6+x. We achieve qualitative agreement, and also propose future experiments to further investigate the behaviour of this dimensionless ratio.

Density Transition Based Self-Focusing of cosh-Gaussian Laser Beam in Plasma with Linear Absorption

International Nuclear Information System (INIS)

Kant, Niti; Wani, Manzoor Ahmad

2015-01-01

Density transition based self-focusing of cosh-Gaussian laser beam in plasma with linear absorption has been studied. The field distribution in the plasma is expressed in terms of beam width parameter, decentered parameter, and linear absorption coefficient. The differential equation for the beam width parameter is solved by following Wentzel–Kramers–Brillouin (WKB) and paraxial approximation through parabolic wave equation approach. The behaviour of beam width parameter with dimensionless distance of propagation is studied at optimum values of plasma density, decentered parameter and with different absorption levels in the medium. The results reveal that these parameters can affect the self-focusing significantly. (paper)

Equations for estimating synthetic unit-hydrograph parameter values for small watersheds in Lake County, Illinois

Science.gov (United States)

Melching, C.S.; Marquardt, J.S.

1997-01-01

Design hydrographs computed from design storms, simple models of abstractions (interception, depression storage, and infiltration), and synthetic unit hydrographs provide vital information for stormwater, flood-plain, and water-resources management throughout the United States. Rainfall and runoff data for small watersheds in Lake County collected between 1990 and 1995 were studied to develop equations for estimation of synthetic unit-hydrograph parameters on the basis of watershed and storm characteristics. The synthetic unit-hydrograph parameters of interest were the time of concentration (TC) and watershed-storage coefficient (R) for the Clark unit-hydrograph method, the unit-graph lag (UL) for the Soil Conservation Service (now known as the Natural Resources Conservation Service) dimensionless unit hydrograph, and the hydrograph-time lag (TL) for the linear-reservoir method for unit-hydrograph estimation. Data from 66 storms with effective-precipitation depths greater than 0.4 inches on 9 small watersheds (areas between 0.06 and 37 square miles (mi2)) were utilized to develop the estimation equations, and data from 11 storms on 8 of these watersheds were utilized to verify (test) the estimation equations. The synthetic unit-hydrograph parameters were determined by calibration using the U.S. Army Corps of Engineers Flood Hydrograph Package HEC-1 (TC, R, and UL) or by manual analysis of the rainfall and run-off data (TL). The relation between synthetic unit-hydrograph parameters, and watershed and storm characteristics was determined by multiple linear regression of the logarithms of the parameters and characteristics. Separate sets of equations were developed with watershed area and main channel length as the starting parameters. Percentage of impervious cover, main channel slope, and depth of effective precipitation also were identified as important characteristics for estimation of synthetic unit-hydrograph parameters. The estimation equations utilizing area

CFD Modelling of the Effects of Operating Parameters on the Spreading of Liquids on a Spinning Disc

Directory of Open Access Journals (Sweden)

Y. Pan

2014-03-01

Full Text Available A novel dry slag granulation process based on a spinning disc is being developed by CSIRO. This process utilises centrifugal force to break up molten slag into droplets, which are then quenched into solidified granules by a flow of cold air. In this process the sensible heat of slag is recovered as hot air. In the present work, a previously developed steady-state, two-dimensional and multiphase CFD model was applied to perform parametric numerical experiments to investigate the effects of a number of parameters on the liquid film thickness at the disc edge, which included liquid mass feeding (pouring rate, disc spinning speed, disc radius, liquid viscosity, density and surface tension. The modelling results were compared with experimental data and were found to be in good agreement. To reduce the number of simulations needed, Box and Behnken's fractional factorial design of numerical experiment was adopted. Furthermore, in order for the modelling results to be applicable to atomisation of different liquids using spinning discs of different sizes, a dimensionless correlation was developed based on dimensional analysis of the numerical simulation data. The modelling results indicate that the liquid film thickness can be significantly influenced by the disc radius and spinning speed, the liquid mass feeding rate, viscosity and density, whereas the liquid surface tension has a negligible effect.

A practical dimensionless equation for the thermal conductivity of carbon nanotubes and CNT arrays

Directory of Open Access Journals (Sweden)

Qiang Chen

2014-05-01

Full Text Available Experimental results reported in the last decade on the thermal conductivity of carbon nanotubes (CNTs have shown a fairly divergent behavior. An underlying intrinsic consistency was believed to exist in spite of the divergence in the thermal conductivity data of various CNTs. A dimenisonless equation that describes the temperature dependence of thermal conductivity was derived by introducing reduced forms relative to a chosen reference point. This equation can serve as a practical approximation to characterize the conductivity of individual CNT with different structural parameters as well as bulk CNT arrays with different bundle configurations. Comparison of predictions by the equation and historical measurements showed good agreements within their uncertainties.

The Hyperbolic Sine Cardinal and the Catenary

Science.gov (United States)

Sanchez-Reyes, Javier

2012-01-01

The hyperbolic function sinh(x)/x receives scant attention in the literature. We show that it admits a clear geometric interpretation as the ratio between length and chord of a symmetric catenary segment. The inverse, together with the use of dimensionless parameters, furnishes a compact, explicit construction of a general catenary segment of…

Theoretical analysis of consecutive reactions in adiabatic stirred tank reactors

International Nuclear Information System (INIS)

Jo, Byung Wook; Kim, Sun Il; Hong, Won Hae; Cha, Wol Suk; Kim, Soong Pyung; Kim, Jung Gyu

1990-01-01

By mathematical model for the case of the consecutive first-order exothermic reaction in an adiabatic CSTR, the effects of the system parameter i. e. relative residence time, heat of reaction and thermal sensitivity of reaction rate constant, on the concentration profile of the intermediate product of a consecutive reaction were obtained as follows. For fixed values of the ratio of the reaction rate constants t 1 / t 2 , the ratio of the correponding system parameter α where α>1 and the sensitivities of the reaction rate constants S1 and S2, the maximum value of the intermediate production dimensionless concentration increases with increase in the values of the relative energy parameter E1 and E2 and it decreases with a decrease in E1 and E2. For fixed values of the ratio of the reaction rate constants t 1 / t 2 , the ratio of the corresponding system parameter α where α 1 and t 2 and it increases with a decrease in S1 and S2. For fixed values of the ratio of the reaction rate constants t 1 / t 2 , the ratio of the corresponding system parameters α where α=1 and the relative energy parameters E1 and E2, the maximum value of the intermediate product dimensionless is constant with either increase or decrease in the sensitivities of the reaction rate constants S1 and S2. (Author)

Numerical and dimensional investigation of two-phase countercurrent imbibition in porous media

KAUST Repository

El-Amin, Mohamed

2013-04-01

In this paper, we introduce a numerical solution of the problem of two-phase immiscible flow in porous media. In the first part of this work, we present the general conservation laws for multiphase flows in porous media as outlined in the literature for the sake of completion where we emphasize the difficulties associated with these equations in their primitive form and the fact that they are, generally, unclosed. The second part concerns the 1D computation for dimensional and non-dimensional cases and a theoretical analysis of the problem under consideration. A time-scale based on the characteristic velocity is used to transform the macroscopic governing equations into a non-dimensional form. The resulting dimensionless governing equations involved some important dimensionless physical parameters such as Bond number Bo, capillary number Ca and Darcy number Da. Numerical experiments on the Bond number effect is performed for two cases, gravity opposing and assisting. The theoretical analysis illustrates that common formulations of the time-scale forces the coefficient Da12Ca to be equal to one, while formulation of dimensionless time based on a characteristic velocity allows the capillary and Darcy numbers to appear in the dimensionless governing equation which leads to a wide range of scales and physical properties of fluids and rocks. The results indicate that the buoyancy effects due to gravity force take place depending on the location of the open boundary. © 2012 Elsevier B.V. All rights reserved.

Correlations of drift velocity for gas-liquid two-phase flow in rod bundle

International Nuclear Information System (INIS)

Kataoka, Isao; Matsuura, Keizo; Serizawa, Akimi

2004-01-01

A new correlation was developed for the drift velocity for low inlet liquid flux in rod bundle. Based on authors' previous analysis of drift velocity for large diameter pipe, an analysis was made on the drift velocity in rod bundle. It is assumed that the large bubble of which size is several subchannel diameter behaves as slug bubble. Under this assumption, it becomes very important how to define equivalent diameter for rod bundle. In view of physical consideration of slug bubble behavior and previous analysis, an equivalent diameter based on the wetted perimeter was found to be most appropriate. Using this equivalent diameter, experimental data of drift velocity in rod bundle were correlated with dimensional analysis. It was found out that for small diameter (dimensionless diameter less than 48) drift velocity increased with square root of diameter which is same dependency of ordinary slug flow correlation. For larger diameter (dimensionless diameter is more than 48), drift velocity is almost constant and same as that of dimensionless diameter of 48. The physical meaning of this result was considered to be the instability of interface of large slug bubble. The density ratio between gas and liquid and viscosity of liquid phase were found to be the main parameters which affect the drift velocity. This is physically reasonable because density ratio is related to the buoyancy force and liquid viscosity is related to shear force near solid wall. The experimental data were correlated by density ratio and dimensionless liquid viscosity. The obtained dimensionless correlation for the drift velocity in rod bundle successfully correlated experimental data for various rod bundles (equivalent diameters), pressures, liquid fluxes etc. It is also consistent with the drift flux correlation for round tube. (author)

Radiative mixed convection over an isothermal cone embedded in a porous medium with variable permeability

KAUST Repository

El-Amin, Mohamed; Ebrahiem, N.A.; Salama, Amgad; Sun, S.

2011-01-01

The interaction of mixed convection with thermal radiation of an optical dense viscous fluid adjacent to an isothermal cone imbedded in a porous medium with Rosseland diffusion approximation incorporating the variation of permeability and thermal conductivity is numerically investigated. The transformed conservation laws are solved numerically for the case of variable surface temperature conditions. Numerical results are given for the dimensionless temperature profiles and the local Nusselt number for various values of the mixed convection parameter , the cone angle parameter ?, the radiation-conduction parameter R d, and the surface temperature parameter H. Copyright 2011 M. F. El-Amin et al.

Henry constants in polymer solutions with the van der Waals equation of state

DEFF Research Database (Denmark)

Bithas, Sotiris; Kalospiros, Nikolaos; Kontogeorgis, Georgios

1996-01-01

parameter is satisfactory, with typical errors within the experimental uncertainty and comparable to those with the more complex Perturbed Hard Chain Theory-based equations of state with the same number of adjustable parameters. A predictive scheme for calculating Henry constants is also presented, which...... is a corresponding-states correlation for a dimensionless Henry constant defined based on the van der Waals equation of state. Satisfactory results-often close to the ones from the one-parameter correlation-are obtained for all systems investigated in this work. Compared with literature models that have been applied...

Current sheets in the Earth’s magnetosphere and in laboratory experiments: The magnetic field structure and the Hall effect

International Nuclear Information System (INIS)

Frank, A. G.; Artemyev, A. V.; Zelenyi, L. M.

2016-01-01

The main characteristics of current sheets (CSs) formed in laboratory experiments are compared with the results of satellite observations of CSs in the Earth’s magnetotail. We show that many significant features of the magnetic field structure and the distributions of plasma parameters in laboratory and magnetospheric CSs exhibit a qualitative similarity, despite the enormous differences of scales, absolute values of plasma parameters, magnetic fields, and currents. In addition to a qualitative comparison, we give a number of dimensionless parameters that demonstrate the possibility of laboratory modeling of the processes occurring in the magnetosphere.

Comparison between relativistic, semirelativistic, and nonrelativistic approaches of quarkonium

International Nuclear Information System (INIS)

Semay, C.; Silvestre-Brac, B.

1992-01-01

We study the connections existing between relativistic, semirelativistic, and nonrelativistic potential models of quarkonium using an interaction composed of an attractive Coulomb potential and a confining power-law term. We show that the spectra of these very different models become nearly similar provided specific relations exist between the dimensionless parameters peculiar to each model. As our analysis is carried out by taking advantage of scaling laws, our results are applicable for a wide range of physical parameters

Improved lumped models for transient combined convective and radiative cooling of a two-layer spherical fuel element

International Nuclear Information System (INIS)

Silva, Alice Cunha da; Su, Jian

2013-01-01

The High Temperature Gas cooled Reactor (HTGR) is a fourth generation thermal nuclear reactor, graphite-moderated and helium cooled. The HTGRs have important characteristics making essential the study of these reactors, as well as its fuel element. Examples of these are: high thermal efficiency,low operating costs and construction, passive safety attributes that allow implication of the respective plants. The Pebble Bed Modular Reactor (PBMR) is a HTGR with spherical fuel elements that named the reactor. This fuel element is composed by a particulate region with spherical inclusions, the fuel UO2 particles, dispersed in a graphite matrix and a convective heat transfer by Helium happens on the outer surface of the fuel element. In this work, the transient heat conduction in a spherical fuel element of a pebble-bed high temperature reactor was studied in a transient situation of combined convective and radiative cooling. Improved lumped parameter model was developed for the transient heat conduction in the two-layer composite sphere subjected to combined convective and radiative cooling. The improved lumped model was obtained through two-point Hermite approximations for integrals. Transient combined convective and radiative cooling of the two-layer spherical fuel element was analyzed to illustrate the applicability of the proposed lumped model, with respect to die rent values of the Biot number, the radiation-conduction parameter, the dimensionless thermal contact resistance, the dimensionless inner diameter and coating thickness, and the dimensionless thermal conductivity. It was shown by comparison with numerical solution of the original distributed parameter model that the improved lumped model, with H2,1/H1,1/H0,0 approximation yielded significant improvement of average temperature prediction over the classical lumped model. (author)

Derivation and application of mathematical model for well test analysis with variable skin factor in hydrocarbon reservoirs

Directory of Open Access Journals (Sweden)

Pengcheng Liu

2016-06-01

Full Text Available Skin factor is often regarded as a constant in most of the mathematical model for well test analysis in oilfields, but this is only a kind of simplified treatment with the actual skin factor changeable. This paper defined the average permeability of a damaged area as a function of time by using the definition of skin factor. Therefore a relationship between a variable skin factor and time was established. The variable skin factor derived was introduced into existing traditional models rather than using a constant skin factor, then, this newly derived mathematical model for well test analysis considering variable skin factor was solved by Laplace transform. The dimensionless wellbore pressure and its derivative changed with dimensionless time were plotted with double logarithm and these plots can be used for type curve fitting. The effects of all the parameters in the expression of variable skin factor were analyzed based on the dimensionless wellbore pressure and its derivative. Finally, actual well testing data were used to fit the type curves developed which validates the applicability of the mathematical model from Sheng-2 Block, Shengli Oilfield, China.

An investigation into the nature and signifiance of a new critical heat flux correlation

International Nuclear Information System (INIS)

Green, W.J.; Beattie, D.R.H.

1983-01-01

An empirical critical heat flux correlation, which is based upon dimensionsless groups, and which was developed from a wide range of experimental data for vertical upflow in uniformly heated tubes, has been further examined to determine if, because of its accuracy and generality, it might provide an insight into the mechanisms of boiling crisis. A parameter survey using the correlation showed that it was well able to predict the so-called 'crisis of the second kind' without needing to define any separate or distinct flow regimes. Comparison of the empirical correlation with a general form of theoretical correlation, developed from a combination of several simple physical models which occur during the crisis phenomenon, shows a strong similarity in the form of the dimensionless groups. It also indicates that a further dimensionless group may need to be incorporated in the empirical correlation to achieve complete generality. Rearrangements of the dimensionless groups and the form of the empirical correlation, together with some minor approximations, indicate that boiling crisis is influenced by local hydrodynamic and thermal phenomena and can be related to pre- and post-crisis coolant conditions. (orig.)

Adomian decomposition method for Hall and ion-slip effects on mixed convection flow of a chemically reacting Newtonian fluid between parallel plates with heat generation/absorption

Directory of Open Access Journals (Sweden)

Ch.Ram Reddy

2017-12-01

Full Text Available This paper analyzes the heat and mass transfer characteristics on mixed convective fully developed flow in an electrically conducting Newtonian fluid between vertical parallel plates. The chemical reaction, heat generation, Hall and ion-slip effects are taken into consideration. By using similarity transformations the nonlinear governing equations are reduced into dimensionless form and hence solved using Adomian decomposition method (ADM. The influence of magnetic parameter, Hall parameter, ion-slip parameter, chemical reaction parameter, and heat generation/absorption parameter on non-dimensional velocities, temperature and concentration profiles are exhibited graphically. In addition, the numerical data for skin friction, heat and mass transfer rates are shown in tabular form.

Comprehensive energy transport scalings derived from DIII-D similarity experiments

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baity, F.W.

1998-12-01

The dependences of heat transport on the dimensionless plasma physics parameters has been measured for both L-mode and H-mode plasmas on the DIII-D tokamak. Heat transport in L-mode plasmas has a gyroradius scaling that is gyro-Bohm-like for electrons and worse than Bohm-like for ions, with no measurable beta or collisionality dependence; this corresponds to having an energy confinement time that scales like τ E ∝ n 0.5 P -0.5 . H-mode plasmas have gyro-Bohm-like scaling of heat transport for both electrons and ions, weak beta scaling, and moderate collisionality scaling. In addition, H-mode plasmas have a strong safety factor scaling (χ ∼ q 2 ) at all radii. Combining these four dimensionless parameter scalings together gives an energy confinement time scaling for H-mode plasmas like τ E ∝ B -1 ρ -3.15 β 0.03 v -0.42 q 95 -1.43 ∝ I 0.84 B 0.39 n 0.18 P -0.41 L 2.0 , which is similar to empirical scalings derived from global confinement databases

Comprehensive energy transport scalings derived from DIII-D similarity experiments

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baity, F.W.

1999-01-01

The dependences of heat transport on the dimensionless plasma physics parameters has been measured for both L-mode and H-mode plasmas on the DIII-D tokamak. Heat transport in L-mode plasmas has a gyroradius scaling that is gyro-Bohm-like for electrons and worse than Bohm-like for ions, with no measurable beta or collisionality dependence; this corresponds to having an energy confinement time that scales like τ E ∝ n 0.5 P -0.5 . H-mode plasmas have gyro-Bohm-like scaling of heat transport for both electrons and ions, weak beta scaling, and moderate collisionality scaling. In addition, H-mode plasmas have a strong safety factor scaling (χ ∼ q 2 ) at all radii. Combining these four dimensionless parameter scalings together gives an energy confinement time scaling for H-mode plasmas like τ E ∝ B -1 ρ -3.15 β 0.03 ν -0.42 q 95 -1.43 ∝ I 0.84 B 0.39 n 0.18 P -0.41 L 2.0 , which is similar to empirical scalings derived from global confinement databases. (author)

Comprehensive energy transport scalings derived from DIII-D similarity experiments

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baker, D.R.

2001-01-01

The dependences of heat transport on the dimensionless plasma physics parameters has been measured for both L-mode and H-mode plasmas on the DIII-D tokamak. Heat transport in L-mode plasmas has a gyroradius scaling that is gyro-Bohm-like for electrons and worse than Bohm-like for ions, with no measurable beta or collisionality dependence; this corresponds to having an energy confinement time that scales like τ E ∝n 0.5 P -0.5 . H-mode plasmas have gyro-Bohm-like scaling of heat transport for both electrons and ions, weak beta scaling, and moderate collisionality scaling. In addition, H-mode plasmas have a strong safety factor scaling (χ∼q 2 ) at all radii. Combining these four dimensionless parameter scalings together gives an energy confinement time scaling for H-mode plasmas like τ E ∝ B -1 ρ -3.15 β 0.03 ν -0.42 q 95 -1.43 ∝ I 0.84 B 0.39 n 0.18 P -0.41 L 2.0 , which is similar to empirical scalings derived from global confinement databases. (author)

A modified variable physical properties model, for analyzing nanofluids flow and heat transfer over nonlinearly stretching sheet

Directory of Open Access Journals (Sweden)

Pooria Akbarzadeh

2017-07-01

Full Text Available In this paper, the problem of laminar nanofluid flow which results from the nonlinear stretching of a flat sheet is investigated numerically. In this paper, a modified variable physical properties model for analyzing nanofluids flow and heat transfer is introduced. In this model, the effective viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids which are commonly utilized in the homogenous single-phase model, are locally combined with the prevalent single-phase model. A numerical similarity solution is considered which depends on the local Prandtl number, local Brownian motion number, local Lewis number, and local thermophoresis number. The results are compared to the prevalent single-phase model. This comparison depicts that the prevalent single-phase model has a considerable deviation for predicting the behavior of nanofluids flow especially in dimensionless temperature and nanoparticle volume fraction. In addition the effect of the governing parameters such as Prandtl number, the Brownian motion number, the thermophoresis parameter, the Lewis number, and etc. on the velocity, temperature, and volume fraction distribution and the dimensionless heat and mass transfer rates are examined.

Evaluation of aerodynamic forces acting on oscillating cantilever beams based on the study of the damped flexural vibration of aluminium test samples

Science.gov (United States)

Egorov, A. G.; Kamalutdinov, A. M.; Nuriev, A. N.

2018-05-01

The paper is devoted to study of the aerodynamic forces acting on flat cantilever beams performing flexural vibrations in a viscous fluid. Original method for the force evaluation is presented based on analysis of experimental measurements of a logarithmic decrement of vibrations and relative variation in frequency of duralumin test specimens. The theoretical core of the method is based on the classical theory of bending beam oscillations and quasi-two dimensional model of interaction between a beam and a gas. Using the proposed method, extensive series of experiments for a wide range of oscillations parameters were carried out. The processing of the experimental data allowed to establish the global influence of the aerodynamic effects on beam oscillations and the local force characteristics of each cross-section of the beam in the form of universal functions of dimensionless amplitude and dimensionless frequency of oscillation. The obtained estimates of the drag and added mass forces showed a good correspondence with the available numerical and experimental data practically in the entire range of the investigated parameters.

New exergy analysis of a regenerative closed Brayton cycle

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2017-01-01

Highlights: • The maximum power is studied relating to time and size constraints variations. • The influence of time and size constraints on exergy destruction are investigated. • The definitions of heat exergy, and second law efficiency are modified. - Abstract: In this study, the optimal performance of a regenerative closed Brayton cycle is sought through power maximization. Optimization is performed on the output power as the objective function using genetic algorithm. In order to take into account the time and the size constraints in current problem, the dimensionless mass-flow parameter is used. The influence of the unavoidable exergy destruction due to finite-time constraint is taken into account by developing the definition of heat exergy. Finally, the improved definitions are proposed for heat exergy, and the second law efficiency. Moreover, the new definitions will be compared with the conventional ones. For example, at a specified dimensionless mass-flow parameter, exergy overestimation in conventional definition, causes about 31% lower estimation of the second law efficiency. These results could be expected to be utilized in future solar thermal Brayton cycle assessment and optimization.

FOR STIMUL-RESPONSIVE POLYMERS WITH ENHANCED EFFICIENCY IN RESERVOIR RECOVERY PROCESSES

Energy Technology Data Exchange (ETDEWEB)

Charles McCormick; Roger Hester

2004-03-26

This report contains a series of terpolymers containing acrylic acid, methacrylamide and a twin-tailed hydrophobic monomer that were synthesized using micellar polymerization methods. These polymer systems were characterized using light scattering, viscometry, and fluorescence methods. Viscosity studies indicate that increasing the nonpolar character of the hydrophobic monomer (longer chain length or twin tailed vs. single tailed) results in enhanced viscosity in aqueous solutions. The interactions of these polymers with surfactants were investigated. These surfactants include sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB), Triton X-100. Viscosity measurements of DiC{sub 6}AM and DiC{sub 8}AM mixtures indicate little interaction with SDS, gelation with CTAB, and hemimicelle formation followed by polymer hydrophobe solubilization with Triton X-100. The DiC{sub 10}Am terpolymer shows similar interaction behavior with CTAB and Triton X-100. However, the enhanced hydrophobic nature of the DiC{sub 10} polymer allows complex formation with SDS as confirmed by surface tensiometry. Fluorescence measurements performed on a dansyl labeled DiC{sub 10}Am terpolymer in the presence of increasing amounts of each of the surfactant indicate relative interaction strengths to be CTAB>Triton X-100>SDS. A modified model based on Yamakawa-Fujii and Odjik-Skolnick-Fixman theories was found to describe the contribution of electrostatic forces to the excluded volume of a polyelectrolyte in solution. The model was found to be valid for flexible polymer coils in aqueous salt solutions where intermolecular interactions are minimal. The model suggested that a dimensionless group of parameters termed the dimensionless viscosity should be proportional to the dimensionless ratio of solution screening length to polyion charge spacing. Several sets of experimental data from the literature and from our laboratory have been analyzed according to the model and the results

Analytical solutions for prediction of the ignition time of wood particles based on a time and space integral method

International Nuclear Information System (INIS)

Haseli, Y.; Oijen, J.A. van; Goey, L.P.H. de

2012-01-01

Highlights: ► A simple model for prediction of the ignition time of a wood particle is presented. ► The formulation is given for both thermally thin and thermally thick particles. ► Transition from thermally thin to thick regime occurs at a critical particle size. ► The model is validated against a numerical model and various experimental data. - Abstract: The main idea of this paper is to establish a simple approach for prediction of the ignition time of a wood particle assuming that the thermo-physical properties remain constant and ignition takes place at a characteristic ignition temperature. Using a time and space integral method, explicit relationships are derived for computation of the ignition time of particles of three common shapes (slab, cylinder and sphere), which may be characterized as thermally thin or thermally thick. It is shown through a dimensionless analysis that the dimensionless ignition time can be described as a function of non-dimensional ignition temperature, reactor temperature or external incident heat flux, and parameter K which represents the ratio of conduction heat transfer to the external radiation heat transfer. The numerical results reveal that for the dimensionless ignition temperature between 1.25 and 2.25 and for values of K up to 8000 (corresponding to woody materials), the variation of the ignition time of a thermally thin particle with K and the dimensionless ignition temperature is linear, whereas the dependence of the ignition time of a thermally thick particle on the above two parameters obeys a quadratic function. Furthermore, it is shown that the transition from the regime of thermally thin to the regime of thermally thick occurs at K cr (corresponding to a critical size of particle) which is found to be independent of the particle shape. The model is validated by comparing the predicted and the measured ignition time of several wood particles obtained from different sources. Good agreement is achieved which

Application of dimensionless sediment rating curves to predict suspended-sediment concentrations, bedload, and annual sediment loads for rivers in Minnesota

Science.gov (United States)

Ellison, Christopher A.; Groten, Joel T.; Lorenz, David L.; Koller, Karl S.

2016-10-27

Consistent and reliable sediment data are needed by Federal, State, and local government agencies responsible for monitoring water quality, planning river restoration, quantifying sediment budgets, and evaluating the effectiveness of sediment reduction strategies. Heightened concerns about excessive sediment in rivers and the challenge to reduce costs and eliminate data gaps has guided Federal and State interests in pursuing alternative methods for measuring suspended and bedload sediment. Simple and dependable data collection and estimation techniques are needed to generate hydraulic and water-quality information for areas where data are unavailable or difficult to collect.The U.S. Geological Survey, in cooperation with the Minnesota Pollution Control Agency and the Minnesota Department of Natural Resources, completed a study to evaluate the use of dimensionless sediment rating curves (DSRCs) to accurately predict suspended-sediment concentrations (SSCs), bedload, and annual sediment loads for selected rivers and streams in Minnesota based on data collected during 2007 through 2013. This study included the application of DSRC models developed for a small group of streams located in the San Juan River Basin near Pagosa Springs in southwestern Colorado to rivers in Minnesota. Regionally based DSRC models for Minnesota also were developed and compared to DSRC models from Pagosa Springs, Colorado, to evaluate which model provided more accurate predictions of SSCs and bedload in Minnesota.Multiple measures of goodness-of-fit were developed to assess the effectiveness of DSRC models in predicting SSC and bedload for rivers in Minnesota. More than 600 dimensionless ratio values of SSC, bedload, and streamflow were evaluated and delineated according to Pfankuch stream stability categories of “good/fair” and “poor” to develop four Minnesota-based DSRC models. The basis for Pagosa Springs and Minnesota DSRC model effectiveness was founded on measures of goodness

Energetics of the multi-phase fluid flow in a narrow kerf in laser cutting conditions

Science.gov (United States)

Golyshev, A. A.; Orishich, A. M.; Shulyatyev, V. B.

2016-10-01

The energy balance of the multi-phase medium flow is studied experimentally under the laser cutting. Experimental data are generalized due to the condition of minimal roughness of the created surface used as a quality criterion of the melt flow, and also due to the application of dimensionless parameters: Peclet number and dimensionless absorbed laser power. For the first time ever it is found that, regardless the assistant gas (oxygen or nitrogen), laser type (the fiber one with the wavelength of 1.07 µm or CO2-laser with the wavelength of 10.6 µm), the minimal roughness is provided at a certain energy input in a melt unit, about 26 J/mm3. With oxygen, 50% of this input is provided by the radiation, the other 50% - by the exothermic reaction of iron oxidation.

Implications of fin profiles on overall performance and weight reduction of a fin and tube heat exchanger

DEFF Research Database (Denmark)

Singh, Shobhana; Sørensen, Kim; Simonsen, Anders Schou

2017-01-01

Fin and tube heat exchangers are being used in several industrial applications by means of novel design and optimized performance. Improvements in geometric design may deliver energy efficient and cost-effective heat exchanger performance with reduced weight. In this paper, a systematic study...... on a cross-flow type fin and tube heat exchanger design for a waste heat recovery application is conducted. The geometric profile of the fin is characterized by a dimensionless design variable named aspect ratio which is parametrically varied to obtain different profiles. Two cases, case-I, and case......,000 using computational fluid dynamics. The numerical results obtained for the reference fin profile are verified with the experimental correlations. Dimensionless parameters such as Nusselt number, Euler number, and efficiency index are calculated to predict the overall performance of the heat exchanger...

Vibration of heat exchange components in liquid and two-phase cross-flow

International Nuclear Information System (INIS)

Pettigrew, M.J.

1978-05-01

Heat exchange components must be analysed at the design stage to avoid flow-induced vibration problems. This paper presents information required to formulate flow-induced vibration excitation mechanisms in liquid and two-phase cross-flow. Three basic excitation mechanisms are considered, namely: 1) fluidelastic instability, 2) periodic wake shedding, and 3) response to random flow turbulence. The vibration excitation information is deduced from vibration response data for various types of tube bundles. Sources of information are: 1) fundamental studies on tube bundles, 2) model testing, 3) field measurements, and 4) operating experiences. Fluidelastic instability is formulated in terms of dimensionless flow velocity and dimensionless damping; periodic wake shedding in terms of Strouhal number and lift coefficient; and random turbulence excitation in terms of statistical parameters of random forces. Guidelines are recommended for design purposes. (author)

Propagation of laser-generated plasma jet in an ambient medium

International Nuclear Information System (INIS)

Loupias, B; Falize, E; Vinci, T; Bouquet, S; Gregory, C D; Koenig, M; Ravasio, A; Pikuz, S; Waugh, J; Woolsey, N C; Nazarov, W; Michaut, C; Kuramitsu, Y; Seiichi, D; Sakawa, Y; Takabe, H; Schiavi, A; Atzeni, S

2009-01-01

In this work we present experimental research related to laboratory astrophysics using an intense laser. The goal of these experiments is to investigate some of the complex features of young stellar objects and astrophysical outflows, in particular the plasma jet interaction with the interstellar medium. The relevance of these experiments to astrophysics is measured through similarity criteria (scaling laws). These ensure the similarity between the astrophysical object and the laboratory provided that the dimensionless numbers are equivalent. Consequently, measurements of the plasma parameters are crucial to link laboratory research to astrophysics as they are needed for the determination of these dimensionless numbers. In this context, we designed experiments to generate plasma jets using an intense laser, and to study the evolution in vacuum and in an ambient medium.

Simulation of square wave voltammetry of three electrode reactions coupled by two reversible chemical reactions

OpenAIRE

Lovrić, Milivoj

2017-01-01

Three fast and reversible electrode reactions that are connected by two reversible chemical reactions that are permanently in the equilibrium are analysed theoretically for square wave voltammetry. The dependence of peak potentials on the dimensionless equilibrium constants of chemical reactions is calculated. The influence of the basic thermodynamic parameters on the square wave voltammetric responses is analysed.

Determination of the radius of a self-pinched beam from its energy integral

International Nuclear Information System (INIS)

Lee, E.P.

1980-01-01

The total transverse energy (kinetic plus potential) of a self-pinched beam may be used to predict the final equilibrium radius when the beam is mismatched at injection. The dependence of potential energy on the current profile shape is characterized by a dimensionless parameter C(z), variations of which are correlated with the change of emittance

Rotation and Radiation Effects on MHD Flow through Porous Medium Past a Vertical Plate with Heat and Mass Transfer

Directory of Open Access Journals (Sweden)

Uday Singh Rajput

2017-11-01

Full Text Available Effects of rotation and radiation on unsteady MHD flow past a vertical plate with variable wall temperature and mass diffusion in the presence of Hall current is studied here. Earlier we studied chemical reaction effect on unsteady MHD flow past an exponentially accelerated inclined plate with variable temperature and mass diffusion in the presence of Hall current. We had obtained the results which were in agreement with the desired flow phenomenon. To study further, we are changing the model by considering radiation effect on fluid, and changing the geometry of the model. Here in this paper we are taking the plate positioned vertically upward and rotating with velocity Ω . Further, medium of the flow is taken as porous. The plate temperature and the concentration level near the plate increase linearly with time. The governing system of partial differential equations is transformed to dimensionless equations using dimensionless variables. The dimensionless equations under consideration have been solved by Laplace transform technique. The model contains equations of motion, diffusion equation and equation of energy. To analyze the solution of the model, desirable sets of the values of the parameters have been considered. The governing equations involved in the flow model are solved by the Laplace-transform technique. The results obtained have been analyzed with the help of graphs drawn for different parameters. The numerical values obtained for the drag at boundary and Nusselt number have been tabulated. We found that the values obtained for velocity, concentration and temperature are in concurrence with the actual flow of the fluid

Heat transfer effects on flow past an exponentially accelerated vertical plate with variable temperature

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2008-01-01

Full Text Available An exact solution to the problem of flow past an exponentially accelerated infinite vertical plate with variable temperature is analyzed. The temperature of the plate is raised linearly with time t. The dimensionless governing equations are solved using Laplace-transform technique. The velocity and temperature profiles are studied for different physical parameters like thermal Grashof number Gr, time and an accelerating parameter a. It is observed that the velocity increases with increasing values of a or Gr.

Dust-ion-acoustic Gardner double layers in a dusty plasma with two ...

Indian Academy of Sciences (India)

and dimensionless parameter, and can be considered as the expansion parameter ϵ, i.e.,. |σ − σc| ≃ ϵ and s = 1 for σ >σc and s = −1 for σ <σc. So, ρ(2) can be described as. ϵ2ρ(2) ≃ −ϵ3 1. 2 c1sψ2,. (13) which, then, must be included in the third-order Poisson's equation. To the next higher order in ϵ, we get the following ...

Heat and mass transfer effects on moving vertical plate in the presence of thermal radiation

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2004-01-01

Full Text Available Thermal radiation effects on moving infinite vertical plate in the presence variable temperature and mass diffusion is considered. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The plate temperature and the concentration level near the plate are raised linearly with time. The dimensionless governing equations are solved using the Laplace-transform technique. The velocity and skin-friction are studied for different parameters like thermal Grashof number, mass Grashof number, time and radiation parameter. It is observed that the velocity slightly decreases with increasing value of the radiation parameter.

Critical submergence for isolated and dual rectangular intakes

Indian Academy of Sciences (India)

Kerem Taştan

China Tech. Sci. 54(4): 799–805. [6] Suerich-Gulick F, Gaskin S, Villeneuve M and Parkinson E. 2014 Characteristics of free-surface vortices at low-head hydropower intakes. J. Hydraulic Eng. 140(3): 291–299. [7] Tastan K and Yıldırım N 2010 Effects of dimensionless parameters on air-entraining vortices. J. Hydraulic Res.

COVER ILLUSTRATION: Complexities of splashing

Science.gov (United States)

Deegan, R. D.; Brunet, P.; Eggers, J.

2008-01-01

We study the impact of a drop of liquid onto a thin layer of the same liquid. We give an overview of the sequence of events that occur as the two most important dimensionless control parameters are varied. In particular, multiple cohorts of droplets can be ejected at different stages after impact due to different mechanisms. Edgerton's famous Milkdrop Coronet is only observed for a narrow range of parameters. Outside this range, the splash is either qualitatively different, or suffers from a much lower level of regularity.

Heavy crude production from shallow formations: long horizontal wells versus horizontal fractures

Energy Technology Data Exchange (ETDEWEB)

Valko, P.; Economides, M. J. [Texas A and M Univ., TX (United States)

1998-12-31

The feasibility of producing heavy oil from shallow formations using either horizontal wells or short horizontal wells fractured horizontally is demonstrated. The problem of optimum proppant placement is solved in two steps. In step one, the finite productivity performance is considered in general terms showing that the performance is a function of two dimensionless parameters. Following derivation of optimum conditions, the solution is applied to the horizontal fracture consideration. The limiting factor is that to create an effective finite conductivity fracture, the dimensionless fracture conductivity must be on the order of unity, a fracture that is difficult to realize in higher permeability formations. The best candidates for the suggested configuration are shallow or moderate formations, or formations otherwise proven to accept horizontal fractures, and formations with low permeability/viscosity ratio. 7 refs., 2 tabs., 10 figs., 2 appendices.

A theoretical study on the accuracy of the T-history method for enthalpy–temperature curve measurement: analysis of the influence of thermal gradients inside T-history samples

International Nuclear Information System (INIS)

Mazo, Javier; Delgado, Mónica; Lázaro, Ana; Dolado, Pablo; Peñalosa, Conchita; Marín, José María; Zalba, Belén

2015-01-01

The present work analyses the effect of radial thermal gradients inside T-history samples on the enthalpy temperature curve measurement. A conduction heat transfer model has been utilized for this purpose. Some expressions have been obtained that relate the main dimensionless numbers of the experiments with the deviations in specific heat capacity, phase change enthalpy and phase change temperature estimations. Although these relations can only be strictly applied to solid materials (e.g. measurements of shape stabilized phase change materials), they can provide some useful and conservative bounds for the deviations of the T-history method. Biot numbers emerge as the most relevant dimensionless parameters in the accuracy of the specific heat capacity and phase change enthalpy estimation whereas this model predicts a negligible influence of the temperature levels used for the experiments or the Stefan number. (paper)

The Influence of Cross-Sectional Shape and Orientation of Micropillar Surface on Microdroplet Formation by a Dewetting Process

Directory of Open Access Journals (Sweden)

Bambang Arip Dwiyantoro

2013-07-01

Full Text Available In this study the dewetting process on micropillars of three different cross-sectional shapes, i.e. circular, square and triangular, was numerically investigated. The influence of the orientation of the triangular and square micropillars on the dewetting behavior was also studied. The numerical simulations showed that the cross-sectional shapes of the micropillars and their orientation play an important role in determining the flow pattern of the dewetting process, especially the evolution and movement of the meniscus across the micropillar before a microdroplet is formed. The diameter of the microdroplets is mainly determined by the capillary effect, viscous drag and fluid inertia contributed by the peeling rate and the thickness of the water layer above the micropillar. The numerical results also indicate that the hydraulic diameter of the micropillars (Dp is one of the parameters governing the size of the microdroplets formed on the top surface of the micropillars after the dewetting process, while the microdroplet diameter is almost insensitive to the cross-sectional shape and orientation of the micropillars. The dimensionless diameter of the microdroplets (d can then be expressed as a function of a dimensionless group, i.e. the Ohnesorge number (Oh, the capillary number (Ca, the dimensionless liquid thickness (H, and the contact angle (q.

Dynamics of Solid Body in Magnetic Suspension under Periodic Excitation

Directory of Open Access Journals (Sweden)

A. M. Gouskov

2017-01-01

Full Text Available The article studies dynamics of ferromagnetic body in hybrid magnetic suspension (HMS. The body is supposed to have one degree of freedom and a nonlinear magnetic force dependence on the current and displacement. The magnetic force induced in the HMS is divided into a passive component and an active one. Specifying the law of current variation in the coil allows us to generate nonlinear oscillations under electromagnet action. To provide periodic excitation the appropriate law of the current variation in the electromagnet coil is proposed. The mathematical model includes external periodic step-excitation. The equation of motion is formed. The scales of similarity are highlighted in the system, and the equation of motion is reduced to dimensionless form.The motion dynamics is studied numerically. The relaxation method was used to determine the periodic motions at different values of dimensionless frequency of the electromagnet excitation as well as to estimate the influence of other dimensionless parameters on the system dynamics. The amplitude-frequency curve analysis allows us to come to conclusion that the nature of system nonlinearity is rigid. Adding the external periodic step-excitation leads to the qualitative change in the nature of movement. This points to the occurrence of bifurcation.

A generalized power-law scaling law for a two-phase imbibition in a porous medium

KAUST Repository

El-Amin, Mohamed

2013-11-01

Dimensionless time is a universal parameter that may be used to predict real field behavior from scaled laboratory experiments in relation to imbibition processes in porous media. Researchers work to nondimensionalize the time has been through the use of parameters that are inherited to the properties of the moving fluids and the porous matrix, which may be applicable to spontaneous imbibition. However, in forced imbibition, the dynamics of the process depends, in addition, on injection velocity. Therefore, we propose the use of scaling velocity in the form of a combination of two velocities, the first of which (the characteristic velocity) is defined by the fluid and the porous medium parameters and the second is the injection velocity, which is a characteristic of the process. A power-law formula is suggested for the scaling velocity such that it may be used as a parameter to nondimensionalize time. This may reduce the complexities in characterizing two-phase imbibition through porous media and works well in both the cases of spontaneous and forced imbibition. The proposed scaling-law is tested against some oil recovery experimental data from the literature. In addition, the governing partial differential equations are nondimensionalized so that the governing dimensionless groups are manifested. An example of a one-dimensional countercurrent imbibition is considered numerically. The calculations are carried out for a wide range of Ca and Da to illustrate their influences on water saturation as well as relative water/oil permeabilities. © 2013 Elsevier B.V.

A generalized power-law scaling law for a two-phase imbibition in a porous medium

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; Sun, Shuyu

2013-01-01

Dimensionless time is a universal parameter that may be used to predict real field behavior from scaled laboratory experiments in relation to imbibition processes in porous media. Researchers work to nondimensionalize the time has been through the use of parameters that are inherited to the properties of the moving fluids and the porous matrix, which may be applicable to spontaneous imbibition. However, in forced imbibition, the dynamics of the process depends, in addition, on injection velocity. Therefore, we propose the use of scaling velocity in the form of a combination of two velocities, the first of which (the characteristic velocity) is defined by the fluid and the porous medium parameters and the second is the injection velocity, which is a characteristic of the process. A power-law formula is suggested for the scaling velocity such that it may be used as a parameter to nondimensionalize time. This may reduce the complexities in characterizing two-phase imbibition through porous media and works well in both the cases of spontaneous and forced imbibition. The proposed scaling-law is tested against some oil recovery experimental data from the literature. In addition, the governing partial differential equations are nondimensionalized so that the governing dimensionless groups are manifested. An example of a one-dimensional countercurrent imbibition is considered numerically. The calculations are carried out for a wide range of Ca and Da to illustrate their influences on water saturation as well as relative water/oil permeabilities. © 2013 Elsevier B.V.

The effects of design parameters on vortex diode pump performance, 2

International Nuclear Information System (INIS)

Yoshitomi, Hideki; Koizumi, Tadao; Muroyama, Kenichi; Wada, Tsutomu.

1989-01-01

A fluidic pump with two vortex diodes is a new technology for transporting dangerous corrosive fluids without the use of moving parts. The pump can be connected with the discharge tank through series and cascade connections. In the previous report, we described the fundamentals and design criteria of the pump for the series connection case. This study has been performed with the same object as the previous work for the case of cascade connection. First, we present the basic pump characteristics with some dimensionless performance factors by analyzing the pump model. Then, the effects of the cylinder volumetric coefficient, driving pressure, suction-diode-to-delivery-diode-passage-area ratio and reverse-flow-to-forward-flow-resistance ratio of the vortex diode are investigated. As a result, the characteristic difference between series and cascade connections is clarified. Basic ways to decide the value of each performance factor are suggested. (author)

Classical entropy generation analysis in cooled homogenous and functionally graded material slabs with variation of internal heat generation with temperature, and convective–radiative boundary conditions

International Nuclear Information System (INIS)

Torabi, Mohsen; Zhang, Kaili

2014-01-01

This article investigates the classical entropy generation in cooled slabs. Two types of materials are assumed for the slab: homogeneous material and FGM (functionally graded material). For the homogeneous material, the thermal conductivity is assumed to be a linear function of temperature, while for the FGM slab the thermal conductivity is modeled to vary in accordance with the rule of mixtures. The boundary conditions are assumed to be convective and radiative concurrently, and the internal heat generation of the slab is a linear function of temperature. Using the DTM (differential transformation method) and resultant temperature fields from the DTM, the local and total entropy generation rates within slabs are derived. The effects of physically applicable parameters such as the thermal conductivity parameter for the homogenous slab, β, the thermal conductivity parameter for the FGM slab, γ, gradient index, j, internal heat generation parameter, Q, Biot number at the right side, Nc 2 , conduction–radiation parameter, Nr 2 , dimensionless convection sink temperature, δ, and dimensionless radiation sink temperature, η, on the local and total entropy generation rates are illustrated and explained. The results demonstrate that considering temperature- or coordinate-dependent thermal conductivity and radiation heat transfer at both sides of the slab have great effects on the entropy generation. - Highlights: • The paper investigates entropy generation in a slab due to heat generation and convective–radiative boundary conditions. • Both homogeneous material and FGM (functionally graded material) were considered. • The calculations are carried out using the differential transformation method which is a well-tested analytical technique

Buckling of thin viscous sheets with inhomogenous viscosity under extensional flows

Science.gov (United States)

Srinivasan, Siddarth; Wei, Zhiyan; Mahadevan, L.

2016-11-01

We investigate the dynamics, shape and stability of a thin viscous sheet subjected to an extensional flow under an imposed non-uniform temperature field. Using finite element simulations, we first solve for the stretching flow to determine the pre-buckling sheet thickness and in-plane flow velocities. Next, we use this solution as the base state and solve the linearized partial differential equation governing the out-of-plane deformation of the mid-surface as a function of two dimensionless operating parameters: the normalized stretching ratio α and a dimensionless width of the heating zone β. We show the sheet can become unstable via a buckling instability driven by the development of localized compressive stresses, and determine the global shape and growth rates of the most unstable mode. The growth rate is shown to exhibit a transition from stationary to oscillatory modes in region upstream of the heating zone. Finally, we investigate the effect of surface tension and present an operating diagram that indicates regions of the parameter space that minimizes or entirely suppresses the instability while achieving desired outlet sheet thickness. Therefore, our work is directly relevant to various industrial processes including the glass redraw & float-glass method.

Radiated chemical reaction impacts on natural convective MHD mass transfer flow induced by a vertical cone

Science.gov (United States)

Sambath, P.; Pullepu, Bapuji; Hussain, T.; Ali Shehzad, Sabir

2018-03-01

The consequence of thermal radiation in laminar natural convective hydromagnetic flow of viscous incompressible fluid past a vertical cone with mass transfer under the influence of chemical reaction with heat source/sink is presented here. The surface of the cone is focused to a variable wall temperature (VWT) and wall concentration (VWC). The fluid considered here is a gray absorbing and emitting, but non-scattering medium. The boundary layer dimensionless equations governing the flow are solved by an implicit finite-difference scheme of Crank-Nicolson which has speedy convergence and stable. This method converts the dimensionless equations into a system of tri-diagonal equations and which are then solved by using well known Thomas algorithm. Numerical solutions are obtained for momentum, temperature, concentration, local and average shear stress, heat and mass transfer rates for various values of parameters Pr, Sc, λ, Δ, Rd are established with graphical representations. We observed that the liquid velocity decreased for higher values of Prandtl and Schmidt numbers. The temperature is boost up for decreasing values of Schimdt and Prandtl numbers. The enhancement in radiative parameter gives more heat to liquid due to which temperature is enhanced significantly.

Effectiveness of ANN for seismic behaviour prediction considering geometric configuration effect in concrete gravity dams

Directory of Open Access Journals (Sweden)

Mohd. Saqib

2016-09-01

Full Text Available In this study, an Artificial Neural Networks (ANN model is built and verified for quick estimation of the structural parameter obtained for a concrete gravity dam section due to seismic excitation. The database of numerous inputs and outputs obtained through Abaqus which are further converted into dimensionless forms in the statistical software (MATLAB to build the ANN model. The developed model can be used for accurate estimation of this parameter. The results showed an excellent capability of the model to predict the outputs with high accuracy and reduced computational time.

A model of the fluid temperature field in a turbulent flow parallel to heated tube bundle

International Nuclear Information System (INIS)

Carvalho Tofani, P. de.

1986-01-01

Basic understanding of thermal-hydraulic phenomena is essential to achieving reactor fuel assembly performance analysis. In this paper, a dimensionless parameter - a normalized fluid temperature - is defined and applied to fluid temperature measurements at particular positions at the exit plane of a bank of nine heated tubes, under different transverse heat flux shapes. This parameter presents an asymptotic trend to equilibrium values, which depend upon considered positions and flux shapes; when increasing the bulk Reynolds Number. Proposed correlations underlie the present approach to predict the fluid temperature field within the tube bundle. (Author) [pt

Complexities of splashing

International Nuclear Information System (INIS)

Deegan, R D; Brunet, P; Eggers, J

2008-01-01

We study the impact of a drop of liquid onto a thin layer of the same liquid. We give an overview of the sequence of events that occur as the two most important dimensionless control parameters are varied. In particular, multiple cohorts of droplets can be ejected at different stages after impact due to different mechanisms. Edgerton's famous Milkdrop Coronet is only observed for a narrow range of parameters. Outside this range, the splash is either qualitatively different, or suffers from a much lower level of regularity. (cover illustration)

MHD and radiation effects on moving isothermal vertical plate with variable mass diffusion

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2006-01-01

Full Text Available An analysis is performed to study the effects of thermal radiation on unsteady free convective flow over a moving vertical plate with mass transfer in the presence of magnetic field. The fluid considered here is a gray, absorbing-emitting radiation but a non- scattering medium. The plate temperature is raised to T 0 and the concentration level near the plate is also raised linearly with time. The dimensionless governing equations are solved using the Laplace transform technique. The velocity, temperature and concentration are studied for different parameters like the magnetic field parameter, radiation parameter, thermal Grashof number, mass Grashof number and time. It is observed that the velocity decreases with increasing magnetic field parameter or radiation parameter. .

A Resolution of the Paradox of Enrichment

Science.gov (United States)

Feng, Z. C.; Li, Y. Charles

2015-06-01

The paradox of enrichment was observed by Rosenzweig [1971] in a class of predator-prey models. Two of the parameters in the models are crucial for the paradox. These two parameters are the prey's carrying capacity and prey's half-saturation for predation. Intuitively, increasing the carrying capacity due to enrichment of the prey's environment should lead to a more stable predator-prey system. Analytically, it turns out that increasing the carrying capacity always leads to an unstable predator-prey system that is susceptible to extinction from environmental random perturbations. This is the so-called paradox of enrichment. Our resolution here rests upon a closer investigation on a dimensionless number H formed from the carrying capacity and the prey's half-saturation. By recasting the models into dimensionless forms, the models are in fact governed by a few dimensionless numbers including H. The effects of the two parameters: carrying capacity and half-saturation are incorporated into the number H. In fact, increasing the carrying capacity is equivalent (i.e. has the same effect on H) to decreasing the half-saturation which implies more aggressive predation. Since there is no paradox between more aggressive predation and instability of the predator-prey system, the paradox of enrichment is resolved. The so-called instability of the predator-prey system is characterized by the existence of a stable limit cycle in the phase plane, which gets closer and closer to the predator axis and prey axis. Due to random environmental perturbations, this can lead to extinction. We also further explore spatially dependent models for which the phase space is infinite-dimensional. The spatially independent limit cycle which is generated by a Hopf bifurcation from an unstable steady state, is linearly stable in the infinite-dimensional phase space. Numerical simulations indicate that the basin of attraction of the limit cycle is riddled. This shows that spatial perturbations can

Thermal analysis of annular fins with temperature-dependent thermal properties

Institute of Scientific and Technical Information of China (English)

I. G. AKSOY

2013-01-01

The thermal analysis of the annular rectangular profile fins with variable thermal properties is investigated by using the homotopy analysis method (HAM). The thermal conductivity and heat transfer coefficient are assumed to vary with a linear and power-law function of temperature, respectively. The effects of the thermal-geometric fin parameter and the thermal conductivity parameter variations on the temperature distribution and fin efficiency are investigated for different heat transfer modes. Results from the HAM are compared with numerical results of the finite difference method (FDM). It can be seen that the variation of dimensionless parameters has a significant effect on the temperature distribution and fin efficiency.

Parameter Estimation

DEFF Research Database (Denmark)

Sales-Cruz, Mauricio; Heitzig, Martina; Cameron, Ian

2011-01-01

of optimisation techniques coupled with dynamic solution of the underlying model. Linear and nonlinear approaches to parameter estimation are investigated. There is also the application of maximum likelihood principles in the estimation of parameters, as well as the use of orthogonal collocation to generate a set......In this chapter the importance of parameter estimation in model development is illustrated through various applications related to reaction systems. In particular, rate constants in a reaction system are obtained through parameter estimation methods. These approaches often require the application...... of algebraic equations as the basis for parameter estimation.These approaches are illustrated using estimations of kinetic constants from reaction system models....

Asymptotic solution for heat convection-radiation equation

Energy Technology Data Exchange (ETDEWEB)

Mabood, Fazle; Ismail, Ahmad Izani Md [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Khan, Waqar A. [Department of Engineering Sciences, National University of Sciences and Technology, PN Engineering College, Karachi, 75350 (Pakistan)

2014-07-10

In this paper, we employ a new approximate analytical method called the optimal homotopy asymptotic method (OHAM) to solve steady state heat transfer problem in slabs. The heat transfer problem is modeled using nonlinear two-point boundary value problem. Using OHAM, we obtained the approximate analytical solution for dimensionless temperature with different values of a parameter ε. Further, the OHAM results for dimensionless temperature have been presented graphically and in tabular form. Comparison has been provided with existing results from the use of homotopy perturbation method, perturbation method and numerical method. For numerical results, we used Runge-Kutta Fehlberg fourth-fifth order method. It was found that OHAM produces better approximate analytical solutions than those which are obtained by homotopy perturbation and perturbation methods, in the sense of closer agreement with results obtained from the use of Runge-Kutta Fehlberg fourth-fifth order method.

Collection and evaluation of salt mixing data with the real time data acquisition system. [LMFBR

Energy Technology Data Exchange (ETDEWEB)

Glazer, S.; Chiu, C.; Todreas, N.E.

1977-09-01

A minicomputer based real time data acquisition system was designed and built to facilitate data collection during salt mixing tests in mock ups of LMFBR rod bundles. The system represents an expansion of data collection capabilities over previous equipment. It performs steady state and transient monitoring and recording of up to 512 individual electrical resistance probes. Extensive real time software was written to govern all phases of the data collection procedure, including probe definition, probe calibration, salt mixing test data acquisition and storage, and data editing. Offline software was also written to permit data examination and reduction to dimensionless salt concentration maps. Finally, the computer program SUPERENERGY was modified to permit rapid extraction of parameters from dimensionless salt concentration maps. The document describes the computer system, and includes circuit diagrams of all custom built components. It also includes descriptions and listings of all software written, as well as extensive user instructions.

Transient heat characteristics of water-saturated porous media with freezing; Toketsu wo tomonau gansui takoshitsu sonai no hiteijo netsu tokusei

Energy Technology Data Exchange (ETDEWEB)

Sasaki, A [Akita National College of Technology, Akita (Japan)

1998-02-25

Analytical and experimental investigations were performed to examine the transient heat characteristics of water-saturated porous media with freezing. As a physical model, a two-dimensional vertical cavity was considered. One vertical wall was abruptly cooled below the fusion temperature. Other three walls were thermally insulated. Three different sizes of glass, and iron, alumina and copper beads were used as the porous media in this study. The cold energy stored up in the porous media and the average thickness of frozen layer were measured in the experiments. Comparisons of the analytical results with the experimental ones were made, and the effects of Darcy number, Stefan number and modified Prandtl number on the transient heat characteristics were discussed. The dimensionless equations for predicting the averaged frozen layer thickness and the stored cold energy were obtained as a function of various dimensionless parameters. 8 refs., 16 figs., 1 tab.

THE PROCESS OF MASS TRANSFER ON THE SOLID-LIQUID BOUNDARY LAYER DURING THE RELEASE OF DICLOFENAC SODIUM AND PAPAVERINE HYDROCHLORIDE FROM TABLETS IN A PADDLE APPARATUS.

Science.gov (United States)

Kasperek, Regina; Zimmer, Lukasz; Poleszak, Ewa

2016-01-01

The release study of diclofenac sodium (DIC) and papaverine hydrochloride (PAP) from two formulations of the tablets in the paddle apparatus using different rotation speeds to characterize the process of mass transfer on the solid-liquid boundary layer was carried out. The dissolution process of active substances was described by values of mass transfer coefficients, the diffusion boundary layer thickness and dimensionless numbers (Sh and Re). The values of calculated parameters showed that the release of DIC and PAP from tablets comprising potato starch proceeded faster than from tablets containing HPMC and microcrystalline cellulose. They were obtained by direct dependencies between Sh and Re in the range from 75 rpm to 125 rpm for both substances from all tablets. The description of the dissolution process with the dimensionless numbers make it possible to plan the drug with the required release profile under given in vitro conditions.

Spherical null geodesics of rotating Kerr black holes

International Nuclear Information System (INIS)

Hod, Shahar

2013-01-01

The non-equatorial spherical null geodesics of rotating Kerr black holes are studied analytically. Unlike the extensively studied equatorial circular orbits whose radii are known analytically, no closed-form formula exists in the literature for the radii of generic (non-equatorial) spherical geodesics. We provide here an approximate formula for the radii r ph (a/M;cosi) of these spherical null geodesics, where a/M is the dimensionless angular momentum of the black hole and cos i is an effective inclination angle (with respect to the black-hole equatorial plane) of the orbit. It is well-known that the equatorial circular geodesics of the Kerr spacetime (the prograde and the retrograde orbits with cosi=±1) are characterized by a monotonic dependence of their radii r ph (a/M;cosi=±1) on the dimensionless spin-parameter a/M of the black hole. We use here our novel analytical formula to reveal that this well-known property of the equatorial circular geodesics is actually not a generic property of the Kerr spacetime. In particular, we find that counter-rotating spherical null orbits in the range (3√(3)−√(59))/4≲cosi ph (a/M;cosi=const) on the dimensionless rotation-parameter a/M of the black hole. Furthermore, it is shown that spherical photon orbits of rapidly-rotating black holes are characterized by a critical inclination angle, cosi=√(4/7), above which the coordinate radii of the orbits approach the black-hole radius in the extremal limit. We prove that this critical inclination angle signals a transition in the physical properties of the spherical null geodesics: in particular, it separates orbits which are characterized by finite proper distances to the black-hole horizon from orbits which are characterized by infinite proper distances to the horizon.

Optimal energy-utilization ratio for long-distance cruising of a model fish

Science.gov (United States)

Liu, Geng; Yu, Yong-Liang; Tong, Bing-Gang

2012-07-01

The efficiency of total energy utilization and its optimization for long-distance migration of fish have attracted much attention in the past. This paper presents theoretical and computational research, clarifying the above well-known classic questions. Here, we specify the energy-utilization ratio (fη) as a scale of cruising efficiency, which consists of the swimming speed over the sum of the standard metabolic rate and the energy consumption rate of muscle activities per unit mass. Theoretical formulation of the function fη is made and it is shown that based on a basic dimensional analysis, the main dimensionless parameters for our simplified model are the Reynolds number (Re) and the dimensionless quantity of the standard metabolic rate per unit mass (Rpm). The swimming speed and the hydrodynamic power output in various conditions can be computed by solving the coupled Navier-Stokes equations and the fish locomotion dynamic equations. Again, the energy consumption rate of muscle activities can be estimated by the quotient of dividing the hydrodynamic power by the muscle efficiency studied by previous researchers. The present results show the following: (1) When the value of fη attains a maximum, the dimensionless parameter Rpm keeps almost constant for the same fish species in different sizes. (2) In the above cases, the tail beat period is an exponential function of the fish body length when cruising is optimal, e.g., the optimal tail beat period of Sockeye salmon is approximately proportional to the body length to the power of 0.78. Again, the larger fish's ability of long-distance cruising is more excellent than that of smaller fish. (3) The optimal swimming speed we obtained is consistent with previous researchers’ estimations.

Experimental study on the unstable direct contact condensation regimes

International Nuclear Information System (INIS)

Damasio, C.; Del Tin, G.; Fiegna, G.; Malandrone, M.

1985-01-01

Vapour-liquid interface fluctuation frequencies have been measured by means of electrical resistive probes. Frequency data from these probes have been compared with measured frequencies from a Kistler piezoelectric pressure transducer in the pool near the steam-water interaction region. An attempt has been made to correlate measured frequencies to the observed condensation regimes. Experimental data concerning ''steam chugging'' and condensation oscillation regimes have been correlated in terms of dimensionless parameters

Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

OpenAIRE

Maksimov Vyacheslav I.; Nagornova Tatiana A.; Glazyrin Viktor P.; Shestakov Igor A.

2016-01-01

Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG). The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables "vorticity – the stream function". Are obtained distributions of the hydrodynamic parameters and temperatures, that character...

Mathematical Simulation of Convective Heat Transfer in the Low-Temperature Storage of Liquefied Natural Gas

OpenAIRE

Shestakov, Igor; Dolgova, Anastasia; Maksimov, Vyacheslav Ivanovich

2015-01-01

The article shows the results of mathematical modeling of convective heat transfer in the low-temperature storage of liquefied natural gas. Regime of natural convection in an enclosure with different intensity of the heat flux at the external borders are investigated. Was examined two-dimensional nonstationary problem within the model of Navier-Stokes in dimensionless variables “vorticity - stream function - temperature”. Distributions of hydrodynamic parameters and temperatures that characte...

Hydrodynamics of Turning Flocks

OpenAIRE

Yang, Xingbo; Marchetti, M. Cristina

2014-01-01

We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The continuum equations controlled by only two dimensionless parameters, orientational inertia and alignment strength, are derived by coarse graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields anisotropic spin waves that mediate the propagation o...

Burnout correlations for even- and odd-numbered peripheral rod clusters over low pressure range

International Nuclear Information System (INIS)

Akaho, E.H.K.

1995-01-01

Burnout data with low pressure Freon-113 for even- and odd- numbered peripheral rod clusters with relatively large spacings were used to derive equations in terms of dimensionless parameters suggested by Barnett. The equations which are for three different flow regimes for each rod geometry (even or odd) were found to predict burnout data with maximum RMS deviation being 3.8%. (author). 11 figs., 3 tabs., 15 refs

Modeling the angular motion dynamics of spacecraft with a magnetic attitude control system based on experimental studies and dynamic similarity

Science.gov (United States)

Kulkov, V. M.; Medvedskii, A. L.; Terentyev, V. V.; Firsyuk, S. O.; Shemyakov, A. O.

2017-12-01

The problem of spacecraft attitude control using electromagnetic systems interacting with the Earth's magnetic field is considered. A set of dimensionless parameters has been formed to investigate the spacecraft orientation regimes based on dynamically similar models. The results of experimental studies of small spacecraft with a magnetic attitude control system can be extrapolated to the in-orbit spacecraft motion control regimes by using the methods of the dimensional and similarity theory.

Theoretical study on air flow in a solar chimney with real insulation conditions; Estudo teorico do escoamento de ar em uma chamine solar com condicoes reais de insolacao

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Andre Guimaraes; Cortez, Marcio Fonte-Boa; Molina Valle, Ramon; Brasil, Cristiana Santiago [Minas Gerais Univ., Belo Horizonte, MG, (Brazil). Dept. de Engenharia Mecanica]. E-mail: ferreira@demec.ufmg.br

2000-07-01

This paper presents a theoretical analysis of the turbulent air flow with real conditions of insulation inside a solar chimney. The flow is described by the mass, momentum and energy conservation equations, besides the transport equations of the quantities in the turbulence model (k and epsilon). Dimensionless parameters are presented at way out the device, as function of time and the insulation conditions, represented by the soil and the roof heating.

The fluid similarity of the boiling crisis

International Nuclear Information System (INIS)

Katsaounis, A.

1986-01-01

Most of the measurements related to the boiling crisis have, until now, been undertaken for a wide parameter variation in the water, and were mainly related to the water-cooled reactor. This article investigates, whether or how the measuring results can be transferred to other fluids. Derived dimensionless similarity figures and those taken from literature are verified by measurements from complex geometries in water and freon 12. (orig.) [de

The fluid similarity of the boiling crisis

International Nuclear Information System (INIS)

Katsaounis, A.

1987-01-01

Most of the measurements related to the boiling crisis have, until now, been undertaken for a wide parameter variation in the water, and were mainly related to the water-cooled reactor. This article investigates, whether or how the measuring results can be transferred to other fluids. Derived dimensionless similarity figures and those taken from literature are verified by measurements from complex geometries in water and freon 12. (orig./GL) [de

Non Newtonian Behavior of Blood in Presence of Arterial Occlusion

OpenAIRE

Dr.Arun Kumar Maiti

2016-01-01

The objective of the present numerical model is to investigate the effect of shape of stenosis on blood flow through an artery using Bingham plastic fluid model. Blood is modeled as Bingham plastic fluid in a uniform circular tube with an axially symmetric but radially non symmetric stenosis. The expressions for flux, dimensionless resistance to flow with stenosis shape parameter, stenosis length and stenosis size have been shown graphically

Comparative study of chemo-electro-mechanical transport models for an electrically stimulated hydrogel

International Nuclear Information System (INIS)

Elshaer, S E; Moussa, W A

2014-01-01

The main objective of this work is to introduce a new expression for the hydrogel’s hydration for use within the Poisson Nernst–Planck chemo electro mechanical (PNP CEM) transport models. This new contribution to the models support large deformation by considering the higher order terms in the Green–Lagrangian strain tensor. A detailed discussion of the CEM transport models using Poisson Nernst–Planck (PNP) and Poisson logarithmic Nernst–Planck (PLNP) equations for chemically and electrically stimulated hydrogels will be presented. The assumptions made to simplify both CEM transport models for electric field application in the order of 0.833 kV m −1 and a highly diluted electrolyte solution (97% is water) will be explained. This PNP CEM model has been verified accurately against experimental and numerical results. In addition, different definitions for normalizing the parameters are used to derive the dimensionless forms of both the PNP and PLNP CEM. Four models, PNP CEM, PLNP CEM, dimensionless PNP CEM and dimensionless PNLP CEM transport models were employed on an axially symmetric cylindrical hydrogel problem with an aspect ratio (diameter to thickness) of 175:3. The displacement and osmotic pressure obtained for the four models are compared against the variation of the number of elements for finite element analysis, simulation duration and solution rate when using the direct numerical solver. (papers)

Magnetic field line random walk in two-dimensional dynamical turbulence

Science.gov (United States)

Wang, J. F.; Qin, G.; Ma, Q. M.; Song, T.; Yuan, S. B.

2017-08-01

The field line random walk (FLRW) of magnetic turbulence is one of the important topics in plasma physics and astrophysics. In this article, by using the field line tracing method, the mean square displacement (MSD) of FLRW is calculated on all possible length scales for pure two-dimensional turbulence with the damping dynamical model. We demonstrate that in order to describe FLRW with the damping dynamical model, a new dimensionless quantity R is needed to be introduced. On different length scales, dimensionless MSD shows different relationships with the dimensionless quantity R. Although the temporal effect affects the MSD of FLRW and even changes regimes of FLRW, it does not affect the relationship between the dimensionless MSD and dimensionless quantity R on all possible length scales.

Thermodynamic optimization of a coiled tube heat exchanger under constant wall heat flux condition

International Nuclear Information System (INIS)

Satapathy, Ashok K.

2009-01-01

In this paper the second law analysis of thermodynamic irreversibilities in a coiled tube heat exchanger has been carried out for both laminar and turbulent flow conditions. The expression for the scaled non-dimensional entropy generation rate for such a system is derived in terms of four dimensionless parameters: Prandtl number, heat exchanger duty parameter, Dean number and coil to tube diameter ratio. It has been observed that for a particular value of Prandtl number, Dean number and duty parameter, there exists an optimum diameter ratio where the entropy generation rate is minimum. It is also found that with increase in Dean number or Reynolds number, the optimum value of the diameter ratio decreases for a particular value of Prandtl number and heat exchanger duty parameter.

Response of the Water Level in a Well to Earth Tides and Atmospheric Loading Under Unconfined Conditions

Science.gov (United States)

Rojstaczer, Stuart; Riley, Francis S.

1990-08-01

The response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well. Because vertical averaging tends to diminish the influence of the water table, the response is qualitatively similar to the response of a well under partially confined conditions. When the influence of well bore storage can be ignored, the response to Earth tides is strongly governed by a dimensionless aquifer frequency Q'u. The response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters: a dimensionless unsaturated zone frequency, R, and a dimensionless aquifer frequency Qu. The differences between Q'u and Qu are generally small for aquifers which are highly sensitive to Earth tides. When Q'u and Qu are large, the response of the well to Earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions. At small values of Q'u and Qu, well response to Earth tides and atmospheric loading is strongly influenced by water table drainage. When R is large relative to Qu, the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone. The presence of partial penetration retards phase advance in well response to Earth tides and atmospheric loading. When the theoretical response of a phreatic well to Earth tides and atmospheric loading is fit to the well response inferred from cross-spectral estimation, it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer.

WIPP Compliance Certification Application calculations parameters. Part 1: Parameter development

International Nuclear Information System (INIS)

Howarth, S.M.

1997-01-01

The Waste Isolation Pilot Plant (WIPP) in southeast New Mexico has been studied as a transuranic waste repository for the past 23 years. During this time, an extensive site characterization, design, construction, and experimental program was completed, which provided in-depth understanding of the dominant processes that are most likely to influence the containment of radionuclides for 10,000 years. Nearly 1,500 parameters were developed using information gathered from this program; the parameters were input to numerical models for WIPP Compliance Certification Application (CCA) Performance Assessment (PA) calculations. The CCA probabilistic codes frequently require input values that define a statistical distribution for each parameter. Developing parameter distributions begins with the assignment of an appropriate distribution type, which is dependent on the type, magnitude, and volume of data or information available. The development of the parameter distribution values may require interpretation or statistical analysis of raw data, combining raw data with literature values, scaling of lab or field data to fit code grid mesh sizes, or other transformation. Parameter development and documentation of the development process were very complicated, especially for those parameters based on empirical data; they required the integration of information from Sandia National Laboratories (SNL) code sponsors, parameter task leaders (PTLs), performance assessment analysts (PAAs), and experimental principal investigators (PIs). This paper, Part 1 of two parts, contains a discussion of the parameter development process, roles and responsibilities, and lessons learned. Part 2 will discuss parameter documentation, traceability and retrievability, and lessons learned from related audits and reviews

Effect of buoyancy on fuel containment in an open-cycle gas-core nuclear rocket engine.

Science.gov (United States)

Putre, H. A.

1971-01-01

Analysis aimed at determining the scaling laws for the buoyancy effect on fuel containment in an open-cycle gas-core nuclear rocket engine, so conducted that experimental conditions can be related to engine conditions. The fuel volume fraction in a short coaxial flow cavity is calculated with a programmed numerical solution of the steady Navier-Stokes equations for isothermal, variable density fluid mixing. A dimensionless parameter B, called the Buoyancy number, was found to correlate the fuel volume fraction for large accelerations and various density ratios. This parameter has the value B = 0 for zero acceleration, and B = 350 for typical engine conditions.

The basic components of residual migration in VTI media using anisotropy continuation

KAUST Repository

Alkhalifah, Tariq Ali; Fomel, S.

2011-01-01

We introduce anisotropy continuation as a process which relates changes in seismic images to perturbations in the anisotropic medium parameters. This process is constrained by two kinematic equations, one for perturbations in the normal-moveout (NMO) velocity and the other for perturbations in the dimensionless anisotropy parameter ?. We consider separately the case of post-stack migration and show that the kinematic equations in this case can be solved explicitly by converting them to ordinary differential equations using the method of characteristics. When comparing the results of kinematic analytical computations with synthetic numerical experiments confirms the theoretical accuracy of the method.

Comparative study of heat transfer and wetting behaviour of conventional and bioquenchants for industrial heat treatment

Energy Technology Data Exchange (ETDEWEB)

Fernandes, Peter; Prabhu, K. Narayan [Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Surathkal, P.O. Srinivasnagar 575 025 Mangalore, Karnataka State (India)

2008-02-15

An investigation was conducted to study the suitability of vegetable oils as bioquenchants for industrial heat treatment. The study involved the assessment of the severity of quenching and wetting behaviour of conventional and vegetable oil quench media. Quench severities of sunflower, coconut and palm oils were found to be greater than mineral oil. The quench severity of aqueous media is greater than oil media although their wettability is poor as indicated by their higher contact angles. A dimensionless contact angle parameter defined in this work is found to be a better parameter to compare the wetting behaviour with heat transfer. (author)

The basic components of residual migration in VTI media using anisotropy continuation

KAUST Repository

Alkhalifah, Tariq Ali

2011-03-24

We introduce anisotropy continuation as a process which relates changes in seismic images to perturbations in the anisotropic medium parameters. This process is constrained by two kinematic equations, one for perturbations in the normal-moveout (NMO) velocity and the other for perturbations in the dimensionless anisotropy parameter ?. We consider separately the case of post-stack migration and show that the kinematic equations in this case can be solved explicitly by converting them to ordinary differential equations using the method of characteristics. When comparing the results of kinematic analytical computations with synthetic numerical experiments confirms the theoretical accuracy of the method.

Theory-based scaling of the SOL width in circular limited tokamak plasmas

International Nuclear Information System (INIS)

Halpern, F.D.; Ricci, P.; Labit, B.; Furno, I.; Jolliet, S.; Loizu, J.; Mosetto, A.; Arnoux, G.; Silva, C.; Gunn, J.P.; Horacek, J.; Kočan, M.; LaBombard, B.

2013-01-01

A theory-based scaling for the characteristic length of a circular, limited tokamak scrape-off layer (SOL) is obtained by considering the balance between parallel losses and non-linearly saturated resistive ballooning mode turbulence driving anomalous perpendicular transport. The SOL size increases with plasma size, resistivity, and safety factor q. The scaling is verified against flux-driven non-linear turbulence simulations, which reveal good agreement within a wide range of dimensionless parameters, including parameters closely matching the TCV tokamak. An initial comparison of the theory against experimental data from several tokamaks also yields good agreement. (letter)

Density of states in an optical speckle potential

International Nuclear Information System (INIS)

Falco, G. M.; Fedorenko, A. A.; Giacomelli, J.; Modugno, M.

2010-01-01

We study the single-particle density of states of a one-dimensional speckle potential, which is correlated and non-Gaussian. We consider both the repulsive and the attractive cases. The system is controlled by a single dimensionless parameter determined by the mass of the particle, the correlation length, and the average intensity of the field. Depending on the value of this parameter, the system exhibits different regimes, characterized by the localization properties of the eigenfunctions. We calculate the corresponding density of states using the statistical properties of the speckle potential. We find good agreement with the results of numerical simulations.

A correlation for the quench front velocity in the rewetting of a rod by a falling film

International Nuclear Information System (INIS)

Castiglia, F.; Olivieri, E.; Taibi, S.; Vella, G.

1989-01-01

In recent works the exact analytical solutions to the problem of the steady propagation of the quench front in the rewetting by a falling film of both hot vertical slabs and rods have been presented. These solutions furnish the temperature distribution in the solid and, in particular, the dimensioless sputtering temperature, in terms of the Biot number B and the dimensionless front velocity u. As it is well known, however, in practical applications it result more convenient to deal with an explicit - even if approximate - formula which gives the dimensionless rewetting velocity in terms of B and Θ. In view of this, in the present paper, an extension to the case of rods of a simple and reliable correlation for the prediction of the quench front velocity, already proposed for slabs, is presented. Also in this case, the correlation proves fairly satisfactory and confirms its validity in the full range of practical interest the operating parameters

Rewetting of composite slab

International Nuclear Information System (INIS)

Satapathy, A.K.; Singh, K.C.

1996-01-01

The process of re-establishment of wetting of hot surface is of practical importance in chemical, metallurgical and nuclear industries. Rewetting is considered in emergency core cooling in nuclear reactors in the event of postulated loss of coolant accident (LOCA). This paper deals with numerical solution of the two-dimensional quasi-static conduction controlled rewetting of an infinite parallel sided composite slab assuming perfect contact is maintained at the interface. On the wetted side upstream of the quench front, a constant heat transfer coefficient is assumed. The downstream of quench front and unwetted side of slab are supposed to be adiabatic. The solution gives the quench front temperature as a function of various model parameters such as Peclet number, wet side Blot number, dimensionless thickness of slab and cladding to fuel ratio of thermal conductivities. The results show that for large values of rewetting velocities, the dimensionless rewetting temperature is unaffected by fuel properties for all values of Blot numbers. (author). 7 refs., 2 tabs., 1 fig

arXiv Agravity up to infinite energy

CERN Document Server

Salvio, Alberto

2018-02-10

The self-interactions of the conformal mode of the graviton are controlled, in dimensionless gravity theories (agravity), by a coupling $f_0$ that is not asymptotically free. We show that, nevertheless, agravity can be a complete theory valid up to infinite energy. When $f_0$ grows to large values, the conformal mode of the graviton decouples from the rest of the theory and does not hit any Landau pole provided that scalars are asymptotically conformally coupled and all other couplings approach fixed points. Then agravity can flow to conformal gravity at infinite energy. We identify scenarios where the Higgs mass does not receive unnaturally large physical corrections. We also show a useful equivalence between agravity and conformal gravity plus two extra conformally coupled scalars, and we give a simpler form for the renormalization group equations of dimensionless couplings as well as of massive parameters in the presence of the most general matter sector.

Thermoelastic stress due to an instantaneous finite line heat source in an infinite medium

International Nuclear Information System (INIS)

Claesson, J.; Hellstroem, G.

1995-09-01

The problem originates from studies of nuclear waste repositories in rock. The problem is by superposition reduced to the case of a single, infinite, antisymmetric, instantaneous line heat source. The dimensionless problem turns out to depend on the dimensionless radial and axial coordinates only, although the original time-dependent problem contains several parameters. An exact analytical solution is derived. The solution is surprisingly handy, considering the complexity of the original problem. The stress and strain field are readily obtained from derivatives of the displacement components. These fields are studied and presented in detail. Asymptotic behaviour, field of principal stresses, regions of compression and tension, and largest values of compression and tension of the components are given as exact formulas. The solution may be used to test numerical models for coupled thermoelastic processes. It may also be used in more detailed numerical simulations of the process near the heat sources as boundary conditions to account for the three-dimensional global process. 7 refs

Agravity up to infinite energy

Energy Technology Data Exchange (ETDEWEB)

Salvio, Alberto [CERN, Theoretical Physics Department, Geneva (Switzerland); Strumia, Alessandro [Dipartimento di Fisica, Universita di Pisa (Italy); INFN, Pisa (Italy)

2018-02-15

The self-interactions of the conformal mode of the graviton are controlled, in dimensionless gravity theories (agravity), by a coupling f{sub 0} that is not asymptotically free. We show that, nevertheless, agravity can be a complete theory valid up to infinite energy. When f{sub 0} grows to large values, the conformal mode of the graviton decouples from the rest of the theory and does not hit any Landau pole provided that scalars are asymptotically conformally coupled and all other couplings approach fixed points. Then agravity can flow to conformal gravity at infinite energy. We identify scenarios where the Higgs mass does not receive unnaturally large physical corrections. We also show a useful equivalence between agravity and conformal gravity plus two extra conformally coupled scalars, and we give a simpler form for the renormalization group equations of dimensionless couplings as well as of massive parameters in the presence of the most general matter sector. (orig.)

Quantum entanglement at negative temperature

International Nuclear Information System (INIS)

Furman, G B; Meerovich, V M; Sokolovsky, V L

2013-01-01

An isolated spin system that is in internal thermodynamic equilibrium and that has an upper limit to its allowed energy states can possess a negative temperature. We calculate the thermodynamic characteristics and the concurrence in this system over the entire range of positive and negative temperatures. Our calculation was performed for different real structures, which can be used in experiments. It is found that the temperature dependence of the concurrence is substantially asymmetrical similarly to other thermodynamic characteristics. At a negative temperature the maximum concurrence and the absolute temperature of the entanglement appearance are significantly larger than those at a positive temperature. The concurrence can be characterized by two dimensionless parameters: the ratio between the Zeeman and dipolar energies and the ratio of the thermal and dipolar energies. It was shown that for all considered structures the dimensionless temperatures of the transition between entanglement and separability of the first and second spins are independent of spin structure and the number of spins. (paper)

A mesoscopic simulation of static and dynamic wetting using many-body dissipative particle dynamics

Science.gov (United States)

Ghorbani, Najmeh; Pishevar, Ahmadreza

2018-01-01

A many-body dissipative particle dynamics simulation is applied here to pave the way for investigating the behavior of mesoscale droplets after impact on horizontal solid substrates. First, hydrophobic and hydrophilic substrates are simulated through tuning the solid-liquid interfacial interaction parameters of an innovative conservative force model. The static contact angles are calculated on homogeneous and several patterned surfaces and compared with the predicted values by the Cassie's law in order to verify the model. The results properly evaluate the amount of increase in surface superhydrophobicity as a result of surface patterning. Then drop impact phenomenon is studied by calculating the spreading factor and dimensionless height versus dimensionless time and the comparisons made between the results and the experimental values for three different static contact angles. The results show the capability of the procedure in calculating the amount of maximum spreading factor, which is a significant concept in ink-jet printing and coating process.

Prediction of 222 Rn exhalation rates from phosphogypsum based stacks. Part II: preliminary numerical results

International Nuclear Information System (INIS)

Rabi, Jose A.; Mohamad, Abdulmajeed A.

2004-01-01

The first part of this paper proposes a steady-state 2-D model for 222 Rn transport in phosphogypsum stacks. In this second part, the dimensionless model equations are solved numerically with the help of an existing finite-volume simulator that has been successfully used to solve heat and mass transfer problems in porous media. As a test case, a rectangular shaped stack is considered in order to verify the ability of the proposed parametric approach to account for concurrent effects on the 222 Rn exhalation into the local atmosphere. Air flow is supposed to be strictly buoyancy driven and the ground is assumed to be impermeable to 222 Rn and at a higher temperature under the stack base. Dimensionless controlling parameters are set to representative values and results are presented for Grashof number in the range 10 6 ≤Gr≤ 10 8 , corresponding to very small to small temperature differences between incoming air and ground underneath the stack base. For the particular set of parameters and inasmuch as Gr increases, streamlines presented basically the same pattern while internal isotherms and iso concentration lines remained almost unchanged. Total average Sherwood number proved to be rather insensitive to Gr while total average Nusselt increased slightly with Gr. (author)

Numerical solutions for magnetohydrodynamic flow of nanofluid over a bidirectional non-linear stretching surface with prescribed surface heat flux boundary

International Nuclear Information System (INIS)

Mahanthesh, B.; Gireesha, B.J.; Gorla, R.S. Reddy; Abbasi, F.M.; Shehzad, S.A.

2016-01-01

Numerical solutions of three-dimensional flow over a non-linear stretching surface are developed in this article. An electrically conducting flow of viscous nanoliquid is considered. Heat transfer phenomenon is accounted under thermal radiation, Joule heating and viscous dissipation effects. We considered the variable heat flux condition at the surface of sheet. The governing mathematical equations are reduced to nonlinear ordinary differential systems through suitable dimensionless variables. A well-known shooting technique is implemented to obtain the results of dimensionless velocities and temperature. The obtained results are plotted for multiple values of pertinent parameters to discuss the salient features of these parameters on fluid velocity and temperature. The expressions of skin-friction coefficient and Nusselt number are computed and analyzed comprehensively through numerical values. A comparison of present results with the previous results in absence of nanoparticle volume fraction, mixed convection and magnetic field is computed and an excellent agreement noticed. We also computed the results for both linear and non-linear stretching sheet cases. - Highlights: • Hydromagnetic flow of nanofluid over a bidirectional non-linear stretching surface is examined. • Cu, Al 2 O3 and TiO 2 types nanoparticles are taken into account. • Numerical solutions have been computed and addressed. • The values of skin-friction and Nusselt number are presented.

Pore Pressure Response to Groundwater Fluctuations in Saturated Double-Layered Soil

Directory of Open Access Journals (Sweden)

Hongwei Ying

2015-01-01

Full Text Available Analytical solutions are developed for one-dimensional consolidation of double-layered saturated soil subjected to groundwater fluctuations. The solutions are derived by an explicit mathematical procedure using Duhamel’s theorem in conjunction with a Fourier series, when groundwater fluctuation is described by a general time-dependent function and assumed to be the pore water pressure variations at the upper boundary. Taking as an example the harmonic groundwater fluctuation, the relevant response of the excess pore water pressure is discussed in detail, and the main influencing factors of the excess pore pressure distribution are analyzed. A dimensionless parameter θ has been introduced because it significantly affects the phase and the amplitude of excess pore pressures. The influences of the coefficients of permeability and compressibility of soil on the excess pore pressure distribution are different and cannot be incorporated into the coefficient of consolidation in double-layered soil. The relative permeability ratio of two clayey soils also plays an important role on the curves of the distributions of the excess pore pressures. The effects of the thickness of the soil layer on the excess pore pressure distribution should be considered together with the dimensionless parameter θ and the permeability and compressibility of the double-layered soil system.

Strong field effects on binary systems in Einstein-aether theory

International Nuclear Information System (INIS)

Foster, Brendan Z.

2007-01-01

'Einstein-aether' theory is a generally covariant theory of gravity containing a dynamical preferred frame. This article continues an examination of effects on the motion of binary pulsar systems in this theory, by incorporating effects due to strong fields in the vicinity of neutron star pulsars. These effects are included through an effective approach, by treating the compact bodies as point particles with nonstandard, velocity dependent interactions parametrized by dimensionless sensitivities. Effective post-Newtonian equations of motion for the bodies and the radiation damping rate are determined. More work is needed to calculate values of the sensitivities for a given fluid source; therefore, precise constraints on the theory's coupling constants cannot yet be stated. It is shown, however, that strong field effects will be negligible given current observational uncertainties if the dimensionless couplings are less than roughly 0.1 and two conditions that match the PPN parameters to those of pure general relativity are imposed. In this case, weak field results suffice. There then exists a one-parameter family of Einstein-aether theories with 'small-enough' couplings that passes all current observational tests. No conclusion can be reached for larger couplings until the sensitivities for a given source can be calculated

Semi-analytical solutions for flow to a well in an unconfined-fractured aquifer system

Science.gov (United States)

Sedghi, Mohammad M.; Samani, Nozar

2015-09-01

Semi-analytical solutions of flow to a well in an unconfined single porosity aquifer underlain by a fractured double porosity aquifer, both of infinite radial extent, are obtained. The upper aquifer is pumped at a constant rate from a pumping well of infinitesimal radius. The solutions are obtained via Laplace and Hankel transforms and are then numerically inverted to time domain solutions using the de Hoog et al. algorithm and Gaussian quadrature. The results are presented in the form of dimensionless type curves. The solution takes into account the effects of pumping well partial penetration, water table with instantaneous drainage, leakage with storage in the lower aquifer into the upper aquifer, and storativity and hydraulic conductivity of both fractures and matrix blocks. Both spheres and slab-shaped matrix blocks are considered. The effects of the underlying fractured aquifer hydraulic parameters on the dimensionless drawdown produced by the pumping well in the overlying unconfined aquifer are examined. The presented solution can be used to estimate hydraulic parameters of the unconfined and the underlying fractured aquifer by type curve matching techniques or with automated optimization algorithms. Errors arising from ignoring the underlying fractured aquifer in the drawdown distribution in the unconfined aquifer are also investigated.

Internal Electric Field In The Space Charge Layer Of A Solar Cell Based On Silicon In The Presence Of Excitons

Directory of Open Access Journals (Sweden)

Modou Faye

2015-08-01

Full Text Available Abstract The author faced with the impossibility of assessing the relative importance of the different contributions of physical quantities appearing in the equations of transport he appealed to the dimensional analysis. Thus by grouping the physical parameters the dependent and independent variables it generates dimensionless numbers. The latter having a physical significance make it possible to characterize the various contributions. To solve the dimensionless equations obtained strongly coupled reduced scale the author opts for a numerical method. The spatial discretization variable pitch and tight at the interfaces of different zones of the field because of the strong gradients in these regions is adopted. The equations are then integrated in the numerical domain using the finite volume method and the coefficients are approached by the schema of the power Patankar law. The resulting system of algebraic equations is solved by the method of double course combined with an iterative relaxation line by line type Gauss-Seidel. Furthermore with a volumetric coefficient of coupling which depends on the dissociation of the excitons and the average temperature field the author has studied the influence of some physical parameters on the total density of photocurrent such that the heating factor the conversion velocity and the volume coupling coefficient of charge carriers.

Radiation effects on flow past an impulsively started vertical plate with variable temperature and mass flux

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2005-01-01

Full Text Available An analysis is performed to study the thermal radiation effects on unsteady free convective flow over a moving vertical plate in the presence of variable temperature and uniform mass flux. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The temperature is raised linearly with time and the concentration level near the plate are raised linearly with time. The dimensionless governing equations are solved using the Laplace transform technique. The velocity and skinfriction are studied for different parameters like the radiation parameter, Schmidt number, thermal Grashof number, mass Grashof number and time. It is observed that the velocity increases with decreasing radiation parameter.

Method of γ expansions in the electronic theory of disordered alloys

International Nuclear Information System (INIS)

Masanskii, I.V.; Tokar', V.I.

1989-01-01

In the electronic theory of disordered alloys an expansion with respect to the parameter γ = exp( -1/ξ ), where ξ is the dimensionless correlation length of the single-electron Green's function, is proposed. This expansion makes it possible to take into account the presence in the alloy of short-range order and the effects of multiple scattering of the electrons by different sites. It is shown that in the case of sufficiently strong disorder γ is a small parameter of the coherent potential approximation, and the corrections to this approximation are found. It is also shown that in the framework of this approximation the equilibrium values of the parameters of the short-range order can be calculated

HEAT AND MASS TRANSFER EFFECTS ON FLOW PAST PARABOLIC STARTING MOTION OF ISOTHERMAL VERTICAL PLATE IN THE PRESENCE OF FIRST ORDER CHEMICAL REACTION

Directory of Open Access Journals (Sweden)

R. Muthucumaraswamy

2013-06-01

Full Text Available An exact solution of unsteady flow past a parabolic starting motion of the infinite isothermal vertical plate with uniform mass diffusion, in the presence of a homogeneous chemical reaction of the first order, has been studied. The plate temperature and the concentration level near the plate are raised uniformly. The dimensionless governing equations are solved using the Laplace transform technique. The effect of velocity profiles are studied for different physical parameters, such as chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number, and time. It is observed that velocity increases with increasing values of thermal Grashof number or mass Grashof number. The trend is reversed with respect to the chemical reaction parameter.

MHD Jeffrey nanofluid past a stretching sheet with viscous dissipation effect

Science.gov (United States)

Zokri, S. M.; Arifin, N. S.; Salleh, M. Z.; Kasim, A. R. M.; Mohammad, N. F.; Yusoff, W. N. S. W.

2017-09-01

This study investigates the influence of viscous dissipation on magnetohydrodynamic (MHD) flow of Jeffrey nanofluid over a stretching sheet with convective boundary conditions. The nonlinear partial differential equations are reduced into the nonlinear ordinary differential equations by utilizing the similarity transformation variables. The Runge-Kutta Fehlberg method is used to solve the problem numerically. The numerical solutions obtained are presented graphically for several dimensionless parameters such as Brownian motion, Lewis number and Eckert number on the specified temperature and concentration profiles. It is noted that the temperature profile is accelerated due to increasing values of Brownian motion parameter and Eckert number. In contrast, both the Brownian motion parameter and Lewis number have caused the deceleration in the concentration profiles.

Silhouette and spectral line profiles in the special modification of the Kerr black hole geometry generated by quintessential fields

Energy Technology Data Exchange (ETDEWEB)

Schee, Jan; Stuchlik, Zdenek [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics and Research Centre for Theoretical Physics and Astrophysics, Opava (Czech Republic)

2016-11-15

We study optical effects in quintessential Kerr black hole spacetimes corresponding to the limiting case of the equation-of-state parameter ω{sub q} = -1/3 of the quintessence. In dependence on the dimensionless quintessential field parameter c, we determine the black hole silhouette and the spectral line profiles of Keplerian disks generated in this special quintessential Kerr geometry, representing an extension of the general modifications of the Kerr geometry introduced recently by Ghasemi-Nodehi and Bambi (Eur. Phys. J. C 56:290, 2016). We demonstrate that due to the influence of the parameter c, the silhouette is almost homogeneously enlarged, and the spectral line profiles are redshifted with almost conserved shape. (orig.)

Echocardiographic Evaluation of Hemodynamic Changes in Left-Sided Heart Valves in Pregnant Women With Valvular Heart Disease.

Science.gov (United States)

Samiei, Niloufar; Amirsardari, Mandana; Rezaei, Yousef; Parsaee, Mozhgan; Kashfi, Fahimeh; Hantoosh Zadeh, Sedigheh; Beikmohamadi, Somayeh; Fouladi, Masoumeh; Hosseini, Saeid; Peighambari, Mohammad Mehdi; Mohebbi, Ahmad

2016-10-01

Physiologic changes during pregnancy can deteriorate or improve patients' hemodynamic status in the setting of valvular heart disease. There are sparse data regarding the effect of pregnancy on valve hemodynamics in normal pregnant women with known valvular heart disease. In a prospective study from July 2014 to January 2016, a total of 52 normal pregnant women who had mitral stenosis, aortic stenosis, or a history of mitral valve or aortic valve replacements were assessed. All patients underwent echocardiographic examinations and hemodynamic parameters were measured for both the mitral valve and aortic valve at first, second, and third trimesters. The parameters included mean gradient, peak gradient, mean gradient/heart rate, peak gradient/heart rate, pressure halftime, dimensionless velocity index, and valve area. Although most hemodynamic parameters (i.e., mean gradient, peak gradient, mean gradient/heart rate, and peak gradient/heart rate) increased approximately 50% from first to second trimester and first to third trimester (p 0.05). The ratio of changes between trimesters for valve area and dimensionless velocity index were comparable. No clinical decompensations were observed except for 3 and 7 cases of deterioration to functional class II at second and third trimesters, respectively. In conclusion, during a full-term and uncomplicated pregnancy, mitral and aortic valve gradients increase without significant changes in valve area that are more marked between the second and first trimester than between the third and second trimester. Copyright © 2016 Elsevier Inc. All rights reserved.

Hydromagnetic transport phenomena from a stretching or shrinking nonlinear nanomaterial sheet with Navier slip and convective heating: A model for bio-nano-materials processing

Energy Technology Data Exchange (ETDEWEB)

Uddin, M.J., E-mail: jashim_74@yahoo.com [Department of Mathematics, American International University-Bangladesh, Banani Dhaka 1213 (Bangladesh); Bég, O. Anwar [Gort Engovation Research (Propulsion/Biomechanics), Gabriel' s Wing House, 15 Southmere Ave., Bradford, BD7 3NU England (United Kingdom); Amin, N. [Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor (Malaysia)

2014-11-15

Steady two-dimensional magnetohydrodynamic laminar free convective boundary layer slip flow of an electrically conducting Newtonian nanofluid from a translating stretching/shrinking sheet in a quiescent fluid is studied. A convective heating boundary condition is incorporated. The transport equations along with the boundary conditions are first converted into dimensionless form and following the implementation of a linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge–Kutta–Fehlberg fourth fifth order method from Maple. Validation of the Maple solutions is achieved with previous non-magnetic published results. The effects of the emerging thermophysical parameters; namely, stretching/shrinking, velocity slip, magnetic field, convective heat transfer and buoyancy ratio parameters, on the dimensionless velocity, temperature and concentration (nanoparticle fraction) are depicted graphically and interpreted at length. It is found that velocity increases whilst temperature and concentration reduce with the velocity slip. Magnetic field causes to reduce velocity and enhances temperature and concentration. Velocity, temperature as well as concentration rises with convective heating parameter. The study is relevant to the synthesis of bio-magnetic nanofluids of potential interest in wound treatments, skin repair and smart coatings for biological devices. - Highlights: • This paper analyses MHD slip flow of nofluid with convective boundary conditions. • Group method is used to transform governing equations into similarity equations. • The Runge–Kutta–Fehlberg method is used for numerical computations. • The study is relevant to synthesis of bio-magnetic nanofluids.

Hazardous waste incinerators under waste uncertainty: balancing and throughput maximization via heat recuperation.

Science.gov (United States)

Tsiliyannis, Christos Aristeides

2013-09-01

Hazardous waste incinerators (HWIs) differ substantially from thermal power facilities, since instead of maximizing energy production with the minimum amount of fuel, they aim at maximizing throughput. Variations in quantity or composition of received waste loads may significantly diminish HWI throughput (the decisive profit factor), from its nominal design value. A novel formulation of combustion balance is presented, based on linear operators, which isolates the wastefeed vector from the invariant combustion stoichiometry kernel. Explicit expressions for the throughput are obtained, in terms of incinerator temperature, fluegas heat recuperation ratio and design parameters, for an arbitrary number of wastes, based on fundamental principles (mass and enthalpy balances). The impact of waste variations, of recuperation ratio and of furnace temperature is explicitly determined. It is shown that in the presence of waste uncertainty, the throughput may be a decreasing or increasing function of incinerator temperature and recuperation ratio, depending on the sign of a dimensionless parameter related only to the uncertain wastes. The dimensionless parameter is proposed as a sharp a' priori waste 'fingerprint', determining the necessary increase or decrease of manipulated variables (recuperation ratio, excess air, auxiliary fuel feed rate, auxiliary air flow) in order to balance the HWI and maximize throughput under uncertainty in received wastes. A 10-step procedure is proposed for direct application subject to process capacity constraints. The results may be useful for efficient HWI operation and for preparing hazardous waste blends. Copyright © 2013 Elsevier Ltd. All rights reserved.

Lumped-parameter models

Energy Technology Data Exchange (ETDEWEB)

Ibsen, Lars Bo; Liingaard, M.

2006-12-15

A lumped-parameter model represents the frequency dependent soil-structure interaction of a massless foundation placed on or embedded into an unbounded soil domain. In this technical report the steps of establishing a lumped-parameter model are presented. Following sections are included in this report: Static and dynamic formulation, Simple lumped-parameter models and Advanced lumped-parameter models. (au)

Heat transfer analysis in internally-cooled fuel elements by means of a conformal mapping approach

International Nuclear Information System (INIS)

Sarmiento, G.S.; Laura, P.A.A.

1981-01-01

The present paper deals with an approximate solution of the steady-state heat conduction problem in internally cooled fuel elements of fast breeder reactors. Explicit expressions for the dimensionless temperature distribution in terms of the governing physical and geometrical parameters are determined by means of a coupled conformal mapping-variational approach. The results obtained are found to be in very good agreement with those calculated by means of a finite element code. (orig.)

Sum rules, asymptotic behaviour and (multi)baryon states in the Skyrme model

International Nuclear Information System (INIS)

Mignaco, J.A.; Wulck, S.

1990-01-01

We obtain sum roles that should be satisfied by the solutions of the Euler-Lagrange equation for the chiral angle in the Skyrme model in the hedgehog representation. The sum rules allow to determine the existence of solutions with integer baryon number for well determined values of a relevant dimensionless parameter Φ only. For all other values, there are no solutions with integer baryon number, in particular for the pure non-linear sigma model. (author)

Competition between Local Collisions and Collective Hydrodynamic Feedback Controls Traffic Flows in Microfluidic Networks

Science.gov (United States)

Belloul, M.; Engl, W.; Colin, A.; Panizza, P.; Ajdari, A.

2009-05-01

By studying the repartition of monodisperse droplets at a simple T junction, we show that the traffic of discrete fluid systems in microfluidic networks results from two competing mechanisms, whose significance is driven by confinement. Traffic is dominated by collisions occurring at the junction for small droplets and by collective hydrodynamic feedback for large ones. For each mechanism, we present simple models in terms of the pertinent dimensionless parameters of the problem.

Untitled

Indian Academy of Sciences (India)

number K = kH for the fundamental Love mode for various values of the anisotropy parameters. The curye corresponding to g = 0 is for isotropic media. The phase velocity lies in the range. (1 – e)” < C < 1.3(1 − s.)”. K = 0 for c = (1-s)”; K – co as C– 13(1-3)”. where C = c/6, is the dimensionless phase velocity, K = kH is the ...

Booster parameter list

International Nuclear Information System (INIS)

Parsa, Z.

1986-10-01

The AGS Booster is designed to be an intermediate synchrotron injector for the AGS, capable of accelerating protons from 200 MeV to 1.5 GeV. The parameters listed include beam and operational parameters and lattice parameters, as well as parameters pertaining to the accelerator's magnets, vacuum system, radio frequency acceleration system, and the tunnel. 60 refs., 41 figs

A parameter tree approach to estimating system sensitivities to parameter sets

International Nuclear Information System (INIS)

Jarzemba, M.S.; Sagar, B.

2000-01-01

A post-processing technique for determining relative system sensitivity to groups of parameters and system components is presented. It is assumed that an appropriate parametric model is used to simulate system behavior using Monte Carlo techniques and that a set of realizations of system output(s) is available. The objective of our technique is to analyze the input vectors and the corresponding output vectors (that is, post-process the results) to estimate the relative sensitivity of the output to input parameters (taken singly and as a group) and thereby rank them. This technique is different from the design of experimental techniques in that a partitioning of the parameter space is not required before the simulation. A tree structure (which looks similar to an event tree) is developed to better explain the technique. Each limb of the tree represents a particular combination of parameters or a combination of system components. For convenience and to distinguish it from the event tree, we call it the parameter tree. To construct the parameter tree, the samples of input parameter values are treated as either a '+' or a '-' based on whether or not the sampled parameter value is greater than or less than a specified branching criterion (e.g., mean, median, percentile of the population). The corresponding system outputs are also segregated into similar bins. Partitioning the first parameter into a '+' or a '-' bin creates the first level of the tree containing two branches. At the next level, realizations associated with each first-level branch are further partitioned into two bins using the branching criteria on the second parameter and so on until the tree is fully populated. Relative sensitivities are then inferred from the number of samples associated with each branch of the tree. The parameter tree approach is illustrated by applying it to a number of preliminary simulations of the proposed high-level radioactive waste repository at Yucca Mountain, NV. Using a

Inventory parameters

CERN Document Server

Sharma, Sanjay

2017-01-01

This book provides a detailed overview of various parameters/factors involved in inventory analysis. It especially focuses on the assessment and modeling of basic inventory parameters, namely demand, procurement cost, cycle time, ordering cost, inventory carrying cost, inventory stock, stock out level, and stock out cost. In the context of economic lot size, it provides equations related to the optimum values. It also discusses why the optimum lot size and optimum total relevant cost are considered to be key decision variables, and uses numerous examples to explain each of these inventory parameters separately. Lastly, it provides detailed information on parameter estimation for different sectors/products. Written in a simple and lucid style, it offers a valuable resource for a broad readership, especially Master of Business Administration (MBA) students.

Interrelations between EOS parameters and cohesive energy of transition metals: Thermostatistical approach, ab initio calculations and analysis of ;universality; features

Science.gov (United States)

Bertoldi, Dalía S.; Ramos, Susana B.; Guillermet, Armando Fernández

2017-08-01

We present a theoretical analysis of the equation of state (EOS) of metals using a quasi-harmonic Einstein model with a dimensionless cohesive energy versus distance function (F(z)) involving the Wigner-Seitz radius and a material-dependent scaling length, as suggested in classical works by Rose, Ferrante, Smith and collaborators. Using this model, and "universal" values for the function and its first and second derivatives at the equilibrium distance (z=0), three general interrelations between EOS parameters and the cohesive energy are obtained. The first correlation involves the bulk modulus, and the second, the thermal expansion coefficient. In order to test these results an extensive database is developed, which involves available experimental data, and results of current ab initio density-functional-theory calculations using the VASP code. In particular, the 0 K values for volume, bulk modulus, its pressure derivative, and the cohesive energy of 27 elements belonging to the first (Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn), second (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd) and third (Hf, Ta, W, Re, Os, Ir, Pt, Au) transition row of the Periodic Table are calculated ab initio and used to test the present results. The third correlation obtained, allows an evaluation of the third derivative of F(z) at z=0 for the current elements. With this new information, a discussion is presented of the possibility of finding a "universal" F(z) versus z function able to account accurately for the pressure derivative of the bulk modulus of the transition elements.

A comparison between two powder compaction parameters of plasticity: the effective medium A parameter and the Heckel 1/K parameter.

Science.gov (United States)

Mahmoodi, Foad; Klevan, Ingvild; Nordström, Josefina; Alderborn, Göran; Frenning, Göran

2013-09-10

The purpose of the research was to introduce a procedure to derive a powder compression parameter (EM A) representing particle yield stress using an effective medium equation and to compare the EM A parameter with the Heckel compression parameter (1/K). 16 pharmaceutical powders, including drugs and excipients, were compressed in a materials testing instrument and powder compression profiles were derived using the EM and Heckel equations. The compression profiles thus obtained could be sub-divided into regions among which one region was approximately linear and from this region, the compression parameters EM A and 1/K were calculated. A linear relationship between the EM A parameter and the 1/K parameter was obtained with a strong correlation. The slope of the plot was close to 1 (0.84) and the intercept of the plot was small in comparison to the range of parameter values obtained. The relationship between the theoretical EM A parameter and the 1/K parameter supports the interpretation of the empirical Heckel parameter as being a measure of yield stress. It is concluded that the combination of Heckel and EM equations represents a suitable procedure to derive a value of particle plasticity from powder compression data. Copyright © 2013 Elsevier B.V. All rights reserved.

Numerical simulation of MHD pulsatile flow of a biofluid in a channel

Directory of Open Access Journals (Sweden)

Kashif Ali

2015-08-01

Full Text Available The purpose of this paper is to numerically study the interaction of an external magnetic field with the flow of a biofluid through a Darcy-Forchhmeir porous channel, due to an oscillatory pressure gradient, in the presence of wall transpiration as well as chemical reaction considerations. We have noticed that if the Reynolds number of the wall transpiration flow is increased, the average (or maximum velocity of the main flow direction is raised. Similar effect has also been observed for the rheological parameter and the Darcy parameter, whereas an opposite trend has been noted for both the Forchheimer quadratic drag parameter and the magnetic parameter. Further, an increase in the Reynolds number results in straightening the concentration profile, thus making it an almost linear function of the dimensionless spatial variable.

Effects of magnetic, radiation and chemical reaction on unsteady heat and mass transfer flow of an oscillating cylinder

Science.gov (United States)

Ahmed, Rubel; Rana, B. M. Jewel; Ahmmed, S. F.

2017-06-01

The effects of magnetic, radiation and chemical reaction parameters on the unsteady heat and mass transfer boundary layer flow past an oscillating cylinder is considered. The dimensionless momentum, energy and concentration equations are solved numerically by using explicit finite difference method with the help of a computer programming language Compaq visual FORTRAN 6.6a. The obtained results of this study have been discussed for different values of well-known parameters with different time steps. The effect of these parameters on the velocity field, temperature field and concentration field, skin-friction, Nusselt number, streamlines and isotherms has been studied and results are presented by graphically represented by the tabular form quantitatively. The stability and convergence analysis of the solution parameters that have been used in the mathematical model have been tested.

Finite element and network electrical simulation of rotating magnetofluid flow in nonlinear porous media with inclined magnetic field and hall currents

Directory of Open Access Journals (Sweden)

Bég Anwar O.

2014-01-01

Full Text Available A mathematical model is presented for viscous hydromagnetic flow through a hybrid non-Darcy porous media rotating generator. The system is simulated as steady, incompressible flow through a nonlinear porous regime intercalated between parallel plates of the generator in a rotating frame of reference in the presence of a strong, inclined magnetic field A pressure gradient term is included which is a function of the longitudinal coordinate. The general equations for rotating viscous magnetohydrodynamic flow are presented and neglecting convective acceleration effects, the two-dimensional viscous flow equations are derived incorporating current density components, porous media drag effects, Lorentz drag force components and Hall current effects. Using an appropriate group of dimensionless variables, the momentum equations for primary and secondary flow are rendered nondimensional and shown to be controlled by six physical parameters-Hartmann number (Ha, Hall current parameter (Nh, Darcy number (Da, Forchheimer number (Fs, Ekman number (Ek and dimensionless pressure gradient parameter (Np, in addition to one geometric parameter-the orientation of the applied magnetic field (θ . Several special cases are extracted from the general model, including the non-porous case studied earlier by Ghosh and Pop (2006. A numerical solution is presented to the nonlinear coupled ordinary differential equations using both the Network Simulation Method and Finite Element Method, achieving excellent agreement. Additionally very good agreement is also obtained with the earlier analytical solutions of Ghosh and Pop (2006. for selected Ha, Ek and Nh values. We examine in detail the effects of magnetic field, rotation, Hall current, bulk porous matrix drag, second order porous impedance, pressure gradient and magnetic field inclination on primary and secondary velocity distributions and also frictional shear stresses at the plates. Primary velocity is seen to decrease

Statistical MOSFET Parameter Extraction with Parameter Selection for Minimal Point Measurement

Directory of Open Access Journals (Sweden)

Marga Alisjahbana

2013-11-01

Full Text Available A method to statistically extract MOSFET model parameters from a minimal number of transistor I(V characteristic curve measurements, taken during fabrication process monitoring. It includes a sensitivity analysis of the model, test/measurement point selection, and a parameter extraction experiment on the process data. The actual extraction is based on a linear error model, the sensitivity of the MOSFET model with respect to the parameters, and Newton-Raphson iterations. Simulated results showed good accuracy of parameter extraction and I(V curve fit for parameter deviations of up 20% from nominal values, including for a process shift of 10% from nominal.

Microneedle-assisted transdermal delivery of Zolmitriptan: effect of microneedle geometry, in vitro permeation experiments, scaling analyses and numerical simulations.

Science.gov (United States)

Uppuluri, Chandra Teja; Devineni, Jyothirmayee; Han, Tao; Nayak, Atul; Nair, Kartik J; Whiteside, Benjamin R; Das, Diganta B; Nalluri, Buchi N

2017-08-01

The present study was aimed to investigate the effect of salient microneedle (MN) geometry parameters like length, density, shape and type on transdermal permeation enhancement of Zolmitriptan (ZMT). Two types of MN devices viz. AdminPatch ® arrays (ADM) (0.6, 0.9, 1.2 and 1.5 mm lengths) and laboratory fabricated polymeric MNs (PM) of 0.6 mm length were employed. In the case of PMs, arrays were applied thrice at different places within a 1.77 cm 2 skin area (PM-3) to maintain the MN density closer to 0.6 mm ADM. Scaling analyses was done using dimensionless parameters like concentration of ZMT (C t /C s ), thickness (h/L) and surface area of the skin (Sa/L 2 ). Micro-injection molding technique was employed to fabricate PM. Histological studies revealed that the PM, owing to their geometry/design, formed wider and deeper microconduits when compared to ADM of similar length. Approximately 3.17- and 3.65-fold increase in ZMT flux values were observed with 1.5 mm ADM and PM-3 applications when compared to the passive studies. Good correlations were observed between different dimensionless parameters with scaling analyses. Numerical simulations, using MATLAB and COMSOL software, based on experimental data and histological images provided information regarding the ZMT skin distribution after MN application. Both from experimental studies and simulations, it was inferred that PM were more effective in enhancing the transdermal delivery of ZMT when compared to ADM. The study suggests that MN application enhances the ZMT transdermal permeation and the geometrical parameters of MNs play an important role in the degree of such enhancement.

MHD peristaltic motion of Johnson-Segalman fluid in a channel with compliant walls

International Nuclear Information System (INIS)

Hayat, T.; Javed, Maryiam; Asghar, S.

2008-01-01

A mathematical model for magnetohydrodynamic (MHD) flow of a Johnson-Segalman fluid in a channel with compliant walls is analyzed. The flow is engendered due to sinusoidal waves on the channel walls. A series solution is developed for the case in which the amplitude ratio is small. Our computations show that the mean axial velocity of a Johnson-Segalman fluid is smaller than that of a viscous fluid. The variations of various interesting dimensionless parameters are graphed and discussed

Topology of helical fluid flow

DEFF Research Database (Denmark)

Andersen, Morten; Brøns, Morten

2014-01-01

function for the topology of the streamline pattern in incompressible flows. On this basis, we perform a comprehensive study of the topology of the flow field generated by a helical vortex filament in an ideal fluid. The classical expression for the stream function obtained by Hardin (Hardin, J. C. 1982...... the zeroes of a single real function of one variable, and we show that three different flow topologies can occur, depending on a single dimensionless parameter. By including the self-induced velocity on the vortex filament by a localised induction approximation, the stream function is slightly modified...... and an extra parameter is introduced. In this setting two new flow topologies arise, but not more than two critical points occur for any combination of parameters....

Study of flow past an exponentially accelerated isothermal vertical plate in the presence of chemical reaction

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2010-01-01

Full Text Available Theoretical study of unsteady flow past an exponentially accelerated infinite isothermal vertical plate with variable mass diffusion has been presented in the presence of homogeneous chemical reaction of first order. The plate temperature is raised to Tw and species concentration level near the plate is made to rise linearly with time. The dimensionless governing equations are solved using Laplace-transform technique. The velocity profiles are studied for different physical parameters like chemical reaction parameter, thermal Grashof number, mass Grashof number, a and time. It is observed that the velocity increases with increasing values of a or t. But the trend is just reversed with respect to K.

Analysis of the Response of a 600 kW Stall Controlled Wind Turbine in Complex Terrain

Energy Technology Data Exchange (ETDEWEB)

Cuerva, A.; Bercebal, D.; De la Cruz, S.; Lopez-Diez, S.; Lopez-Roque, V.; Vazquez-Aguado, A.; Marti, I.; Marchante, M.; Navarro, J. [CIEMAT. Madrid (Spain)

1998-12-31

This work presents a detailed analysis of the operating characteristics of a 600 kW rated power wind turbine installed in complex terrain. The description of the experimental set up and analysis system is included. The relationships between parameters that describe the wind turbine response and the environmental conditions are established via high level statistical analysis, fatigue analysis and analysis is the frequency domain. Dimensionless factors are calculated to explain the intrinsic response of the structure before stochastic and deterministic wind conditions, independently from its size and wind intensity. Finally, conclusions are presented regarding the parameters that affect the loading state and power production of the machine. (Author) 12 refs.

Experimental Study of Air Vessel Behavior for Energy Storage or System Protection in Water Hammer Events

Directory of Open Access Journals (Sweden)

Mohsen Besharat

2017-01-01

Full Text Available An experimental assessment of an air pocket (AP, confined in a compressed air vessel (CAV, has been investigated under several different water hammer (WH events to better define the use of protection devices or compressed air energy storage (CAES systems. This research focuses on the size of an AP within an air vessel and tries to describe how it affects important parameters of the system, i.e., the pressure in the pipe, stored pressure, flow velocity, displaced volume of water and water level in the CAV. Results present a specific range of air pockets based on a dimensionless parameter extractable for other real systems.

Thermal efficiency on welding of AA6061-T6 alloy by modified indirect electric arc and current signals digitalisation

International Nuclear Information System (INIS)

Ambriz, R. R.; Barrera, G.; Garcia, R.; Lopez, V. H.

2009-01-01

The results of the thermal efficiency on welding by modified indirect electric arc technique (MIEA) [1] of the 6061- T6 aluminum alloy are presented. These values are in a range of 90 to 94 %, which depend of the preheating employed. Thermal efficiency was obtained by means of a balance energy which considers the heat input, the amount of melted mass of the welding profiles, and welding parameters during the joining, especially of the arc current data acquisition. Also, some dimensionless parameters were employed in order to determine the approximation grade of the melted pool, the heat affected zone (HAZ), and their corresponding values with the experimental results. (Author) 13 refs

Thermal efficiency on welding of AA6061-T6 alloy by modified indirect electric arc and current signals digitalisation; Eficiencia termica en soldadura de la aleacion AA6061-T6 por arco electrico indirecto modificado y digitalizacion de senales de intensidad de corriente

Energy Technology Data Exchange (ETDEWEB)

Ambriz, R. R.; Barrera, G.; Garcia, R.; Lopez, V. H.

2009-07-01

The results of the thermal efficiency on welding by modified indirect electric arc technique (MIEA) [1] of the 6061- T6 aluminum alloy are presented. These values are in a range of 90 to 94 %, which depend of the preheating employed. Thermal efficiency was obtained by means of a balance energy which considers the heat input, the amount of melted mass of the welding profiles, and welding parameters during the joining, especially of the arc current data acquisition. Also, some dimensionless parameters were employed in order to determine the approximation grade of the melted pool, the heat affected zone (HAZ), and their corresponding values with the experimental results. (Author) 13 refs.

Ponderomotive and weakly relativistic self-focusing of Gaussian laser beam in plasma: Effect of light absorption

Energy Technology Data Exchange (ETDEWEB)

Patil, S. D., E-mail: sdpatilphy@gmail.com [Department of Physics, Devchand College, Arjunnagar, Dist.: Kolhapur 591 237 (India); Takale, M. V. [Department of Physics, Shivaji University, Kolhapur 416 004 (India)

2016-05-06

This paper presents an influence of light absorption on self-focusing of laser beam propagation in plasma. The differential equation for beam-width parameter is obtained using the Wentzel-Kramers-Brillouin and paraxial approximations through parabolic equation approach. The nonlinearity in dielectric function is assumed to be aroused due to the combined effect of weakly relativistic and ponderomotive regime. To highlight the nature of propagation, behavior of beam-width parameter with dimensionless distance of propagation is presented graphically and discussed. The present work is helpful to understand issues related to the beam propagation in laser plasma interaction experiments where light absorption plays a vital role.

Plate falling in a fluid: Regular and chaotic dynamics of finite-dimensional models

Science.gov (United States)

Kuznetsov, Sergey P.

2015-05-01

Results are reviewed concerning the planar problem of a plate falling in a resisting medium studied with models based on ordinary differential equations for a small number of dynamical variables. A unified model is introduced to conduct a comparative analysis of the dynamical behaviors of models of Kozlov, Tanabe-Kaneko, Belmonte-Eisenberg-Moses and Andersen-Pesavento-Wang using common dimensionless variables and parameters. It is shown that the overall structure of the parameter spaces for the different models manifests certain similarities caused by the same inherent symmetry and by the universal nature of the phenomena involved in nonlinear dynamics (fixed points, limit cycles, attractors, and bifurcations).

Similarity Theory and Dimensionless Numbers in Heat Transfer

Science.gov (United States)

Marin, E.; Calderon, A.; Delgado-Vasallo, O.

2009-01-01

We present basic concepts underlying the so-called similarity theory that in our opinion should be explained in basic undergraduate general physics courses when dealing with heat transport problems, in particular with those involving natural or free convection. A simple example is described that can be useful in showing a criterion for neglecting…

On the Role of Dimensionless Elastic Fracture Mechanics.

Science.gov (United States)

1985-07-03

34.’ . . . .- . . - . . . - ... - . .. . . . . . -8-.V 6. B.M. Wundt , "A Unified Interpretation of Room Temperature Strength of Notched...207s (1948). D.H. Winne and B.M. Wundt , Application of the Griffith-Irwin theory of crack propagation to the bursting behavior of disks, including... Wundt , A unified interpretation of room-temperature strength of notched specimens as influenced by their size. Metals Engng. Conf., ASME Paper No

Dimensionless energy confinement scaling in W7-AS

International Nuclear Information System (INIS)

Preuss, R.; Dose, V.

2001-01-01

Energy confinement in W7-AS has been analyzed in terms of dimensionally exact form free functions employing Bayesian probability theory. The confinement function was set up as a linear combination of dimensionally exact power law terms as already proposed very early by Connor and Taylor. Generation of this expansion basis is dictated by the basic plasma model which one assumes. Based upon data accumulated in W7-AS, which contains the energy content for a wide variety of variable settings, predictions for single variable scans are made. The scaling functions for density and power scans, respectively, are in quantitative agreement with data collected in W7-AS. The result of a single variable scan is therefore already hidden in the data obtained for arbitrary variable choices and can be extracted from the latter by a proper data analysis. Furthermore, the optimal model for the description of the global transport in W7-AS is identified as the collisional low beta kinetic model. (author)

Dimensionless energy confinement scaling in W7-AS

International Nuclear Information System (INIS)

Preuss, R.; Dose, V.; Linden, W. von der

1999-01-01

Energy confinement in W7-AS has been analyzed in terms of dimensionally exact form free functions employing Bayesian probability theory. The confinement function was set up as a linear combination of dimensionally exact power law terms as already proposed very early by Connor and Taylor. Generation of this expansion basis is dictated by the basic plasma model which one assumes. Based upon data accumulated in W7-AS, which contains the energy content for a wide variety of variable settings, predictions for single variable scans are made. The scaling functions for density and power scans, respectively, are in quantitative agreement with data collected in W7-AS. The result of a single variable scan is therefore already hidden in the data obtained for arbitrary variable choices and can be extracted from the latter by a proper data analysis. Furthermore, the optimal model for the description of the global transport in W7-AS is identified as the collisional low beta kinetic model. (author)

Floating Breakwaters: State-of-the-Art Literature Review.

Science.gov (United States)

1981-10-01

estructure draft (feet) Do 0 structure offset distance for offset breakwater (feet) ) t diameter of scrap tire (feet) 16 SYMBOLS AND DEFINITIONS...mooring line effeL. on roll (degrees) m effective porosity ot poro,,s breakwater (dimensionless) estructure mass (pu::,rJs per second squared per foot...dimensionless) NAf Nyquist frequency (one per second) P load or surface pressure (pounds) estructure porosity (dimensionless) PD dissipated wave power (foot

Study the effect of chemical reaction and variable viscosity on free convection MHD radiating flow over an inclined plate bounded by porous medium

Energy Technology Data Exchange (ETDEWEB)

Ali, M., E-mail: ali.mehidi93@gmail.com [Department of Mathematics, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349 (Bangladesh); Alim, M. A., E-mail: maalim@math.buet.ac.bd; Nasrin, R., E-mail: rehena@math.buet.ac.bd [Department of Mathematics, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Alam, M. S., E-mail: shahalammaths@gmail.com [Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349 (Bangladesh)

2016-07-12

An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocity profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.

Study the effect of chemical reaction and variable viscosity on free convection MHD radiating flow over an inclined plate bounded by porous medium

International Nuclear Information System (INIS)

Ali, M.; Alim, M. A.; Nasrin, R.; Alam, M. S.

2016-01-01

An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocity profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.

Correlation for prediction of growing and detaching bubble contact diameter on a heating wall

International Nuclear Information System (INIS)

Chen Deqi; Pan Liangming; Huang Yanping

2011-01-01

Phenomenal and theoretical analysis on the evolution of bubble contact diameter during bubble growing is presented in this paper, and it was found that the bubble contact diameter is dependent on the bubble growth rate and bubble radius strongly. By analyzing the regarding experimental data published in the literature, the relation between dimensionless bubble contact diameter, and dimensionless bubble growth time is obtained, based on this relation, a correlation relative to dimensionless bubble growth rate and dimensionless bubble radius are proposed for prediction of bubble contact diameter. With proper values of coefficients, a w and n w , this correlation can well predict the bubble contact diameter data published in the literature, with an error within ±20%. (authors)

Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer: the effect of conducting bounding plates

Energy Technology Data Exchange (ETDEWEB)

Ouattara, B; Khouzam, A; Mojtabi, A [Universite de Toulouse (France); INPT, UPS (France); IMFT (Institut de Mecanique des Fluides de Toulouse), Allee Camille Soula, F-31400 Toulouse (France); Charrier-Mojtabi, M C, E-mail: bouattar@imft.fr, E-mail: akhouzam@imft.fr, E-mail: mojtabi@imft.fr, E-mail: cmojtabi@cict.fr [PHASE, EA 810, UFR PCA, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex (France)

2012-06-01

The aim of this study was to investigate the effect of conducting boundaries on the onset of convection in a binary fluid-saturated porous layer. The isotropic saturated porous layer is bounded by two impermeable but thermally conducting plates, subjected to a constant heat flux. These plates have identical conductivity. Moreover, the conductivity of the plates is generally different from the porous layer conductivity. The overall layer is of large extent in both horizontal directions. The problem is governed by seven dimensionless parameters, namely the normalized porosity of the medium {epsilon}, the ratio of plates over the porous layer thickness {delta} and their relative thermal conductivities ratio d, the separation ratio {delta}, the Lewis number Le and thermal Rayleigh number Ra. In this work, an analytical and numerical stability analysis is performed. The equilibrium solution is found to lose its stability via a stationary bifurcation or a Hopf bifurcation depending on the values of the dimensionless parameters. For the long-wavelength mode, the critical Rayleigh number is obtained as Ra{sub cs}=12(1+2d{delta} )/[1+{psi} (2d{delta}Le+Le+1)] and k{sub cs}=0 for {psi}> {psi} {sub uni}> 0. This work extends an earlier paper by Mojtabi and Rees (2011 Int. J. Heat Mass Transfer 54 293-301) who considered a configuration where the porous layer is saturated by a pure fluid.

Dynamically Scaled Model Experiment of a Mooring Cable

Directory of Open Access Journals (Sweden)

Lars Bergdahl

2016-01-01

Full Text Available The dynamic response of mooring cables for marine structures is scale-dependent, and perfect dynamic similitude between full-scale prototypes and small-scale physical model tests is difficult to achieve. The best possible scaling is here sought by means of a specific set of dimensionless parameters, and the model accuracy is also evaluated by two alternative sets of dimensionless parameters. A special feature of the presented experiment is that a chain was scaled to have correct propagation celerity for longitudinal elastic waves, thus providing perfect geometrical and dynamic scaling in vacuum, which is unique. The scaling error due to incorrect Reynolds number seemed to be of minor importance. The 33 m experimental chain could then be considered a scaled 76 mm stud chain with the length 1240 m, i.e., at the length scale of 1:37.6. Due to the correct elastic scale, the physical model was able to reproduce the effect of snatch loads giving rise to tensional shock waves propagating along the cable. The results from the experiment were used to validate the newly developed cable-dynamics code, MooDy, which utilises a discontinuous Galerkin FEM formulation. The validation of MooDy proved to be successful for the presented experiments. The experimental data is made available here for validation of other numerical codes by publishing digitised time series of two of the experiments.

Numerical solutions for magnetohydrodynamic flow of nanofluid over a bidirectional non-linear stretching surface with prescribed surface heat flux boundary

Energy Technology Data Exchange (ETDEWEB)

Mahanthesh, B., E-mail: bmanths@gmail.com [Department of Mathematics, AIMS Institutes, Peenya, 560058 Bangalore (India); Department of Studies and Research in Mathematics, Kuvempu University, Shankaraghatta, 577451 Shimoga, Karnataka (India); Gireesha, B.J., E-mail: bjgireesu@rediffmail.com [Department of Studies and Research in Mathematics, Kuvempu University, Shankaraghatta, 577451 Shimoga, Karnataka (India); Department of Mechanical Engineering, Cleveland State University, Cleveland, OH (United States); Gorla, R.S. Reddy, E-mail: r.gorla@csuohio.edu [Department of Mechanical Engineering, Cleveland State University, Cleveland, OH (United States); Abbasi, F.M., E-mail: abbasisarkar@gmail.com [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)

2016-11-01

Numerical solutions of three-dimensional flow over a non-linear stretching surface are developed in this article. An electrically conducting flow of viscous nanoliquid is considered. Heat transfer phenomenon is accounted under thermal radiation, Joule heating and viscous dissipation effects. We considered the variable heat flux condition at the surface of sheet. The governing mathematical equations are reduced to nonlinear ordinary differential systems through suitable dimensionless variables. A well-known shooting technique is implemented to obtain the results of dimensionless velocities and temperature. The obtained results are plotted for multiple values of pertinent parameters to discuss the salient features of these parameters on fluid velocity and temperature. The expressions of skin-friction coefficient and Nusselt number are computed and analyzed comprehensively through numerical values. A comparison of present results with the previous results in absence of nanoparticle volume fraction, mixed convection and magnetic field is computed and an excellent agreement noticed. We also computed the results for both linear and non-linear stretching sheet cases. - Highlights: • Hydromagnetic flow of nanofluid over a bidirectional non-linear stretching surface is examined. • Cu, Al{sub 2}O3 and TiO{sub 2} types nanoparticles are taken into account. • Numerical solutions have been computed and addressed. • The values of skin-friction and Nusselt number are presented.

Natural convection heat and mass transfer in MHD fluid flow past a moving vertical plate with variable surface temperature and concentration in a porous medium

Directory of Open Access Journals (Sweden)

K. Javaherdeh

2015-09-01

Full Text Available A numerical investigation of two-dimensional steady laminar free convection flow with heat and mass transfer past a moving vertical plate in a porous medium subjected to a transverse magnetic field is carried out. The temperature and concentration level at the plate surface are assumed to follow a power-law type of distribution. The governing non-linear set of equations is solved numerically employing a fully implicit finite difference method. Results are presented to illustrate the influence of different parameters such as Grashof number (Gr, porosity parameter (Kp, magnetic field parameter (Mn and exponents in the power law variation of the surface temperature and concentration, m and n. The dimensionless velocity, temperature and concentration profiles are analyzed and numerical data for the local Nusselt number and Sherwood number are presented. The study accentuates the significance of the relevant parameters.

Conjugate heat transfer of laminar film condensation along a horizontal plate

Energy Technology Data Exchange (ETDEWEB)

Lee, Euk Soo [Pusan National Univesity, Busan (Korea, Republic of)

2006-03-15

This paper proposes appropriate conjugate parameters and dimensionless temperatures to analysis the conjugate problem of heat conduction in solid wall coupled with laminar film condensation flow adjacent to horizontal flat plate. An efficient methods for some fluids are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, Ja{sup *}/Pr, defined by an overall temperature difference, a property ratio {radical}{rho}{sub {iota}}{mu}{sub {iota}} {radical}{rho}{sub {upsilon}}{mu}{sub {upsilon}} and the conjugate parameter {zeta}. The obtained similarity solution reveals the effect of the conjugate parameter, and the results are compared with the simplified solution. The variations of the heat transfer rates as well as the interface temperature and frictions along the plate are shown explicitly.

Investigation of Boiling Heat Transfer of Binary Mixture from Vertical Tube Embedded in porous Media

Institute of Scientific and Technical Information of China (English)

HailongMo; TongzeMa; 等

1996-01-01

Ethanol-water binary mixtures with 7 different mole fractions of ethanol ranging from 0 to 1 were adopted as testing liquids in the experiment.The vertical heating tube was inserted in porous matrix composed of five well sorted glass beads whise diameters range from 0.5 to 4.3mm.Due to the effect of composition,the trend of combination of vapor bubbles was reduced.resulting in the increase of peak heat flux of binary mixture,With the increase of ethanol mole fraction,0.5mm diameter bead of peak heat flux of binary mixture.with the increase of ethanol mole fraction.0.5mm diameter bead had lower value of peak heat flux,while for pure liquid the critical state is difficult to appear,with given diameter of glass bead,there existed an optimum value of mole fraction of ethanol,which was decreased with the increase of bead diameter,A dimensionless heat transfer coefficient was predicted through the introduction of a dimensionless parameter of porous matrix which agreed with the experimental results satisfactorily.

Prediction of Equilibrium States of Kinematic and Thermal Fields in Homogeneous Turbulence Submitted To the Rotation

International Nuclear Information System (INIS)

Chebbi, Besma; Bouzaiane, Mounir; Lili, Taieb

2009-01-01

In this work, effects of rotation on the evolution of kinematic and thermal fields in homogeneous sheared turbulence are investigated using second order closure modeling. The Launder-Reece-Ro di models, the Speziale-Sarkar-Gatski model and the Shih-Lumley models are retained for pressure-strain correlation and pressure-temperature correlation. Whereas classic models are retained for time evolution equations of kinematic and thermal dissipation rates. The fourth order Runge-Kutta method is used to resolve three non linear differential systems obtained after modeling. The numerical integration is carried out separately for several values of the dimensionless rotation number R equal to 0, 0.25 and 0.5. The obtained results are compared to the recent results of Direct Numerical Simulations of G.Brethouwer. The results have confirmed the asymptotic equilibrium behaviors of kinematic and thermal dimensionless parameters. Furthermore they have shown that rotation affects not only kinematic field but also thermal field. The coupling between the Speziale-Sarkar-Gatski model and the Launder-Reece-Rodi model is of a big contribution on the prediction of kinematic and thermal fields

Entropy analysis of convective MHD flow of third grade non-Newtonian fluid over a stretching sheet

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M.M. Rashidi

2017-03-01

Full Text Available The purpose of this article is to study and analyze the convective flow of a third grade non-Newtonian fluid due to a linearly stretching sheet subject to a magnetic field. The dimensionless entropy generation equation is obtained by solving the reduced momentum and energy equations. The momentum and energy equations are reduced to a system of ordinary differential equations by a similarity method. The optimal homotopy analysis method (OHAM is used to solve the resulting system of ordinary differential equations. The effects of the magnetic field, Biot number and Prandtl number on the velocity component and temperature are studied. The results show that the thermal boundary-layer thickness gets decreased with increasing the Prandtl number. In addition, Brownian motion plays an important role to improve thermal conductivity of the fluid. The main purpose of the paper is to study the effects of Reynolds number, dimensionless temperature difference, Brinkman number, Hartmann number and other physical parameters on the entropy generation. These results are analyzed and discussed.

Damage in agitated vessels of large visco-elastic particles dispersed in a highly viscous fluid.

Science.gov (United States)

Bouvier, Laurent; Moreau, Anne; Line, Alain; Fatah, Nouria; Delaplace, Guillaume

2011-01-01

Many food recipes entail several homogenization steps for solid particles in hot or cold viscous liquids, such as pureed fruit and sugar, jam or sauce with mushroom pieces. Unfortunately, these unavoidable processes induce damage to the solid particles. To date, little is known of the extent and nature of the damage caused. Consequently, few clear guidelines are available for monitoring solid particle integrity when mixing solid/liquid suspensions in an agitated tank. In this study, an attempt is made to quantify the impact of various physical parameters including the influence of the rotational speed of the impeller and the processing time on particle attrition, when a suspension of large visco-elastic particles in a highly viscous fluid is mixed under isothermal condition. Pectin gel particles were immerged in a viscous liquid and homogenized for various times and rotational speeds, while the evolution of the particle's morphological parameters was monitored. Then, a set of dimensionless numbers governing the attrition mechanism is established and some empirical process relationships are proposed to correlate these numbers to the morphological characteristics and mass balance ratios. From the conditions observed, it is clear that 2 dimensionless ratios could be responsible for a change in the damaging mechanisms. These 2 ratios are the Froude and impeller rotation numbers. Finally, in the conditions tested, mass balance ratios appear to be mainly sensitive to the impeller rotational number, while the shape ratios are both impacted by the Froude and impeller rotational numbers. Damage to solid particles suspended in a stirred vessel reduce the final product quality in industrial cooking processes. Examples of this are fruit in jam or sauces with mushroom pieces. The attrition phenomenon was measured and the influences of the impeller rotational speed and processing time were evaluated quantitatively in function of dimensionless numbers. This study contributes key

Flow friction and heat transfer of ethanol–water solutions through silicon microchannels

International Nuclear Information System (INIS)

Wu Huiying; Wu Xinyu; Wei Zhen

2009-01-01

An experimental investigation was performed on the flow friction and convective heat transfer characteristics of the ethanol–water solutions flowing through five sets of trapezoidal silicon microchannels having hydraulic diameters ranging from 141.7 µm to 268.6 µm. Four kinds of ethanol–water solutions with the ethanol volume concentrations ranging from 0 to 0.8 were tested under different flow and heating conditions. It was found that the cross-sectional geometric parameters had great effect on the flow friction and heat transfer, and the microchannels with a larger W b /W t (bottom width-to-top width ratio) and a smaller H/W t (depth-to-top width ratio) usually had a larger friction constant and a higher Nusselt number. Entrance effects were significant for the flow friction and heat transfer in silicon microchannels, and decreased with the increase of dimensionless hydrodynamic length L and dimensionless thermal length L + h . When L > 1.0, the hydrodynamic entrance effect on the flow friction was ignorable. For the developed laminar flow in silicon microchannels, the Navier–Stokes equation was applicable. It was also found that the volume concentrations had different effects on the flow friction and heat transfer. Within the experimental range, the effect of volume concentrations on the flow friction was ignorable, and the friction constants of the ethanol–water solutions having different concentrations were the same as those of the pure water. However, volume concentrations had great effect on the convection heat transfer in silicon microchannels. With the increase of the volume concentrations, the Nusselt number of the ethanol–water solutions increased obviously, which was attributed to the combination effect of the increase in the Prantdtl number as well as the volatilization effect of the ethanol. Based on the experimental data, the dimensionless correlations for the flow friction and heat transfer of the ethanol–water solutions in the silicon

Study on the phenomena of natural circulation in LMFBR

International Nuclear Information System (INIS)

Takeda, Hirofumi; Koga, Tomonari

1993-01-01

Decay heat removal with natural circulation is to be introduced to the LMFBR operation under loss of the electric power supply. The natural circulation is highly reliable, but the phenomenon is essentially unstable and subtle, which makes fine prediction difficult. The difficulties of experimental prediction are explained by facts that the phenomena are ruled by the delicate balance between the buoyancy force and the low pressure loss and are influenced by the various parameters such as local geometry, heat capacity and so on. Therefore the similarity rule for the natural circulation has not been fully understood. This study has been conducted to establish the simulation method for the natural circulation phenomena and the detailed phenomena have been reviewed. For the natural circulation in an LMFBR plant, there are no readily available reference velocity and temperature. These values are related only with the heating and cooling rate, the characteristic length and physical properties of the testing fluid. Basic equations were transformed by these values, and dimensionless equations were derived and then two dimensionless numbers, the Gr' number and the Bo' number, were identified. In order to examine the similarity rule for natural circulation we performed experiments using the different scale water models, a 1/20th and a 1/6th model. The temperatures and velocities at typical points were measured in the transient condition with various heating rate as a parameter. Measured temperatures and velocities were transformed to dimensionless forms for comparison and the effects of the Bo' number and the Gr' number were examined. As a result, it was clarified that the effect of the Gr' number is negligibly small but the effect of Bo' number still remained in our experimental range. The Bo' number of an actual plant is within the range of this experiment. Accordingly similitude of the Bo' number becomes important in an experiment to simulate an actual plant. (author)

Light-Induced Hofstadter's Butterfly Spectrum in Optical Lattices

International Nuclear Information System (INIS)

Hou Jingmin

2009-01-01

We propose a scheme to create an effective magnetic field, which can be perceived by cold neutral atoms in a two-dimensional optical lattice, with a laser field with a space-dependent phase and a conventional laser field acting on Λ-type three-level atoms. When the dimensionless parameter α, being the ratio of flux through a lattice cell to one flux quantum, is rational, the energy spectrum shows a fractal band structure, which is so-called Hofstadter's butterfly. (general)

Analysis of performance for centrifugal steam compressor

Energy Technology Data Exchange (ETDEWEB)

Kang, Seung Hwan; Ryu, Chang Kook; Ko, Han Seo [Sungkyunkwan University, Suwon (Korea, Republic of)

2016-12-15

In this study, mean streamline and Computational fluid dynamics (CFD) analyses were performed to investigate the performance of a small centrifugal steam compressor using a latent heat recovery technology. The results from both analysis methods showed good agreement. The compression ratio and efficiency of steam were found to be related with those of air by comparing the compression performances of both gases. Thus, the compression performance of steam could be predicted by the compression performance of air using the developed dimensionless parameters.

Analysis of performance for centrifugal steam compressor

International Nuclear Information System (INIS)

Kang, Seung Hwan; Ryu, Chang Kook; Ko, Han Seo

2016-01-01

In this study, mean streamline and Computational fluid dynamics (CFD) analyses were performed to investigate the performance of a small centrifugal steam compressor using a latent heat recovery technology. The results from both analysis methods showed good agreement. The compression ratio and efficiency of steam were found to be related with those of air by comparing the compression performances of both gases. Thus, the compression performance of steam could be predicted by the compression performance of air using the developed dimensionless parameters

Parcperdue Geopressure--Geothermal Project: Appendix B

Energy Technology Data Exchange (ETDEWEB)

Sweezy, L.R.

1981-10-05

The reservoir models used to perform the drawdown and buildup pressure analyses consist of analytic forms in lieu of the finite difference or numeric simulator types. Analytic models are derived from solutions of the diffusion equation which relate a pressure response with time and distance in the reservoir for a specified flow system. Solutions of the diffusion equation are obtained through mathematical methods such as Laplace transforms, Fourier transforms, Neuman's product techniques and Green's functions. Before an analytic solution is derived, the diffusivity equation is expressed in terms of dimensionless potential (m{sub D}), dimensionless distance (r{sub D}) and dimensionless time (t{sub D}). For the cylindrical coordinate case, the diffusivity equation in dimensionless form for a geopressured system is given.

Fractal corrections of BaTiO3-ceramic sintering parameters

Directory of Open Access Journals (Sweden)

Mitić V.V.

2014-01-01

Full Text Available Morphology of ceramics grains and pores as well as Brownian character of particle dynamics inside ceramics specimen contributes to better understanding of the sintering process. BaTiO3-ceramics, studied in this paper, has light fractal form and it is emanated in three aspects. First, the surface of grains, even in starting green body as well as distribution of grains shows fractal behavior. Second, existence of pores and their distribution follow the rules of fractal geometry. Third, movement of particles inside viscous flow underlies the rule of Brownian motion, which is essentially a fractal category. These three elements, each in its domain influence sintering dynamics, and can be described by dimensionless quantitative factors, αs αp and αm, being normalized to the interval [0,1]. Following sintering process, the associate formulae of Frenkel, Scherer and Mackenzie-Shuttleworth are shown from the angle of view of ceramics fractal dimension changing that approaches to 3. Also, it is shown that the energy balance is not violated after applying fractal correction to quasi equilibrium of the energy emanating from surface area reduction ES and energy adopted by viscous flow Ef .[Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials

Safeguards systems parameters

International Nuclear Information System (INIS)

Avenhaus, R.; Heil, J.

1979-01-01

In this paper analyses are made of the values of those parameters that characterize the present safeguards system that is applied to a national fuel cycle; those values have to be fixed quantitatively so that all actions of the safeguards authority are specified precisely. The analysis starts by introducing three categories of quantities: The design parameters (number of MBAs, inventory frequency, variance of MUF, verification effort and false-alarm probability) describe those quantities whose values have to be specified before the safeguards system can be implemented. The performance criteria (probability of detection, expected detection time, goal quantity) measure the effectiveness of a safeguards system; and the standards (threshold amount and critical time) characterize the magnitude of the proliferation problem. The means by which the values of the individual design parameters can be determined with the help of the performance criteria; which qualitative arguments can narrow down the arbitrariness of the choice of values of the remaining parameters; and which parameter values have to be fixed more or less arbitrarily, are investigated. As a result of these considerations, which include the optimal allocation of a given inspection effort, the problem of analysing the structure of the safeguards system is reduced to an evaluation of the interplay of only a few parameters, essentially the quality of the measurement system (variance of MUF), verification effort, false-alarm probability, goal quantity and probability of detection

The effect of induced magnetic field and convective boundary condition on MHD stagnation point flow and heat transfer of upper-convected Maxwell fluid in the presence of nanoparticle past a stretching sheet

Directory of Open Access Journals (Sweden)

Wubshet Ibrahim

2016-06-01

The numerical results are obtained for velocity, temperature, induced magnetic field and concentration profiles as well as skin friction coefficient, the local Nusselt number and Sherwood number. The results indicate that the skin friction coefficient, the local Nusselt number and Sherwood number decrease with an increase in B and M parameters. Moreover, local Sherwood number -ϕ′(0 decreases with an increase in convective parameter Bi, but the local Nusselt number -θ′(0 increases with an increase in Bi. The results are displayed both in graphical and tabular form to illustrate the effect of the governing parameters on the dimensionless velocity, induced magnetic field, temperature and concentration. The numerical results are compared and found to be in good agreement with the previously published results on special cases of the problem.

Vectoring of parallel synthetic jets: A parametric study

Science.gov (United States)

Berk, Tim; Gomit, Guillaume; Ganapathisubramani, Bharathram

2016-11-01

The vectoring of a pair of parallel synthetic jets can be described using five dimensionless parameters: the aspect ratio of the slots, the Strouhal number, the Reynolds number, the phase difference between the jets and the spacing between the slots. In the present study, the influence of the latter four on the vectoring behaviour of the jets is examined experimentally using particle image velocimetry. Time-averaged velocity maps are used to study the variations in vectoring behaviour for a parametric sweep of each of the four parameters independently. A topological map is constructed for the full four-dimensional parameter space. The vectoring behaviour is described both qualitatively and quantitatively. A vectoring mechanism is proposed, based on measured vortex positions. We acknowledge the financial support from the European Research Council (ERC Grant Agreement No. 277472).

Short-term gas dispersion in idealised urban canopy in street parallel with flow direction

Science.gov (United States)

Chaloupecká, Hana; Jaňour, Zbyněk; Nosek, Štěpán

2016-03-01

Chemical attacks (e.g. Syria 2014-15 chlorine, 2013 sarine or Iraq 2006-7 chlorine) as well as chemical plant disasters (e.g. Spain 2015 nitric oxide, ferric chloride; Texas 2014 methyl mercaptan) threaten mankind. In these crisis situations, gas clouds are released. Dispersion of gas clouds is the issue of interest investigated in this paper. The paper describes wind tunnel experiments of dispersion from ground level point gas source. The source is situated in a model of an idealised urban canopy. The short duration releases of passive contaminant ethane are created by an electromagnetic valve. The gas cloud concentrations are measured in individual places at the height of the human breathing zone within a street parallel with flow direction by Fast-response Ionisation Detector. The simulations of the gas release for each measurement position are repeated many times under the same experimental set up to obtain representative datasets. These datasets are analysed to compute puff characteristics (arrival, leaving time and duration). The results indicate that the mean value of the dimensionless arrival time can be described as a growing linear function of the dimensionless coordinate in the street parallel with flow direction where the gas source is situated. The same might be stated about the dimensionless leaving time as well as the dimensionless duration, however these fits are worse. Utilising a linear function, we might also estimate some other statistical characteristics from datasets than the datasets means (medians, trimeans). The datasets of the dimensionless arrival time, the dimensionless leaving time and the dimensionless duration can be fitted by the generalized extreme value distribution (GEV) in all sampling positions except one.

Generating three-parameter sensor

Directory of Open Access Journals (Sweden)

Filinyuk M. A.

2014-08-01

Full Text Available Generating sensors provide the possibility of getting remote information and its easy conversion into digital form. Typically, these are one-parameter sensors formed by combination of a primary transmitter (PT and a sine wave generator. Two-parameter sensors are not widely used as their implementation causes a problem with ambiguity output when measuring the PT. Nevertheless, the problem of creating miniature, thrifty multi-parameter RF sensors for different branches of science and industry remains relevant. Considering ways of designing RF sensors, we study the possibility of constructing a three-parameter microwave radio frequency range sensor, which is based on a two-stage three-parameter generalized immitance convertor (GIC. Resistive, inductive and capacitive PT are used as sensing elements. A mathematical model of the sensor, which describes the relation of the sensor parameters to the parameters of GIC and PT was developed. The basic parameters of the sensor, its transfer function and sensitivity were studied. It is shown that the maximum value of the power generated signal will be observed at a frequency of 175 MHz, and the frequency ranges depending on the parameters of the PT will be different. Research results and adequacy of the mathematical model were verified by the experiment. Error of the calculated dependences of the lasing frequency on PT parameters change, compared with the experimental data does not exceed 2 %. The relative sensitivity of the sensor based on two-stage GIC showed that for the resistive channel it is about 1.88, for the capacitive channel –1,54 and for the inductive channel –11,5. Thus, it becomes possible to increase the sensor sensitivity compared with the sensitivity of the PT almost 1,2—2 times, and by using the two stage GIC a multifunctional sensor is provided.

Exact solution of thermal radiation on vertical oscillating plate with variable temperature and mass flux

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2010-01-01

Full Text Available Thermal radiation effects on unsteady flow past an infinite vertical oscillating plate in the presence of variable temperature and uniform mass flux is considered. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The plate temperature is raised linearly with time and the mass is diffused from the plate to the fluid at an uniform rate. The dimensionless governing equations are solved using the Laplace transform technique. The velocity, concentration and temperature are studied for different physical parameters like the phase angle, radiation parameter, Schmidt number, thermal Grashof number, mass Grashof number and time. It is observed that the velocity increases with decreasing phase angle ωt.

Free convection boundary layer flow past a horizontal flat plate embedded in porous medium filled by nano-fluid containing gyro-tactic microorganisms

Energy Technology Data Exchange (ETDEWEB)

Aziz, A. [Department of Mechanical Engineering, School of Engineering and Applied Science, Gonzaga University, Spokane, WA 99258 (United States); Khan, W.A. [Department of Engineering Sciences, National University of Sciences and Technology, Karachi 75350 (Pakistan); Pop, I. [Department of Applied Mathematics, Babes-Bolyai University, Cluj-Napoca (Romania)

2012-06-15

The steady boundary layer free convection flow past a horizontal flat plate embedded in a porous medium filled by a water-based nano-fluid containing gyro-tactic microorganisms is investigated. The Oberbeck-Boussinesq approximation is assumed in the analysis. The effects of bio-convection parameters on the dimensionless velocity, temperature, nano-particle concentration and density of motile microorganisms as well as on the local Nusselt, Sherwood and motile microorganism numbers are investigated and presented graphically. In the absence of bio-convection, the results are compared with the existing data in the open literature and found to be in good agreement. The bio-convection parameters strongly influence the heat, mass, and motile microorganism transport rates. (authors)

Effects of hydrodynamic interaction on random adhesive loose packings of micron-sized particles

Directory of Open Access Journals (Sweden)

Liu Wenwei

2017-01-01

Full Text Available Random loose packings of monodisperse spherical micron-sized particles under a uniform flow field are investigated via an adhesive discrete-element method with the two-way coupling between the particles and the fluid. Characterized by a dimensionless adhesion parameter, the packing fraction follows the similar law to that without fluid, but results in larger values due to the hydrodynamic compression. The total pressure drop through the packed bed shows a critical behaviour at the packing fraction of ϕ ≈ 0.22 in the present study. The normalized permeability of the packed bed for different parameters increases with the increase of porosities and is also in consistent with the Kozeny-Carman equation.

Analysis of natural circulation stability in a low pressure thermohydraulic test loop

International Nuclear Information System (INIS)

Jafari, J.; D'Auria, F.; Kazeminejad, H.; Davilu, H.

2002-01-01

This paper discusses an instability study of a natural circulation (NC) loop performed with the aid of Relap5 thermal-hydraulic system code. This loop has been designed and constructed for the analysis of relevant thermohydraulic parameters of a nuclear reactor. In this study, the main parameters for the stability of NC are identified and characterized through the execution of proper code runs. The obtained stability boundary (SB) in the dimensionless Zuber- Sub-cooling plane is compared with the SB reported in referenced literature. The agreement of predicted NC stability boundaries with the results of independent studies demonstrates both the capability of the mentioned code in assessing NC loop stability and the quality of the performed calculations.(author)

Impact of viscosity variation and micro rotation on oblique transport of Cu-water fluid.

Science.gov (United States)

Tabassum, Rabil; Mehmood, R; Nadeem, S

2017-09-01

This study inspects the influence of temperature dependent viscosity on Oblique flow of micropolar nanofluid. Fluid viscosity is considered as an exponential function of temperature. Governing equations are converted into dimensionless forms with aid of suitable transformations. Outcomes of the study are shown in graphical form and discussed in detail. Results revealed that viscosity parameter has pronounced effects on velocity profiles, temperature distribution, micro-rotation, streamlines, shear stress and heat flux. It is found that viscosity parameter enhances the temperature distribution, tangential velocity profile, normal component of micro-rotation and shear stress at the wall while it has decreasing effect on tangential component of micro-rotation and local heat flux. Copyright © 2017 Elsevier Inc. All rights reserved.

Influence of light absorption on relativistic self-focusing of Gaussian laser beam in cold quantum plasma

Science.gov (United States)

Patil, S. D.; Valkunde, A. T.; Vhanmore, B. D.; Urunkar, T. U.; Gavade, K. M.; Takale, M. V.

2018-05-01

When inter particle distance is comparable to the de Broglies wavelength of charged particles, quantum effects in plasmas are unavoidable. We have exploited an influence of light absorption on self-focusing of Gaussian laser beam in cold quantum plasma by considering relativistic nonlinearity. Nonlinear differential equation governing beam-width parameter has been established by using parabolic equation approach under paraxial and WKB approximations. The effect of light absorption on variation of beam-width parameter with dimensionless distance of propagation is presented graphically and discussed. It is found that light absorption plays vital role in weakening the relativistic self-focusing of laser beam during propagation in cold quantum plasma and gives reasonably interesting results.

Optimal design of multistage chemostats in series using different microbial growth kinetics

Energy Technology Data Exchange (ETDEWEB)

Qasim, Muhammad [Petroleum Engineering Technology, Abu Dhabi Polytechnic (United Arab Emirates)

2013-07-01

In this paper, the optimum design of multistage chemostats (CSTRs) was investigated. The optimal design was based on the minimum overall reactor volume using different volume for each chemostat. The paper investigates three different microbial growth kinetics; Monod kinetics, Contois kinetics and the Logistic equation. The total dimensionless residence time (theta Total) was set as the optimization objective function that was minimized by varying the intermediate dimensionless substrate concentration (alfa i). The effect of inlet substrate concentration (S0) to the first reactor on the optimized total dimensionless residence time was investigated at a constant conversion of 0.90. In addition, the effect of conversion on the optimized total dimensionless residence time was also investigated at constant inlet substrate concentration (S0). For each case, optimization was done using up to five chemostats in series.

Mixed convection flow of couple stress nanofluid over oscillatory stretching sheet with heat absorption/generation effects

Directory of Open Access Journals (Sweden)

Sami Ullah Khan

2018-03-01

Full Text Available The aim of this article is to highlight the unsteady mixed convective couple stress nanoliquid flow passed through stretching surface. The flow is generated due to periodic oscillations of sheet. An appropriate set of dimensionless variables are used to reduce the independent variables in governing equations arising from mathematical modeling. An analytical solution has been computed by employing the technique of homotopy method. The outcomes of various sundry parameters like couple stress parameter, the ratio of angular velocity to stretching rate, thermophoresis parameter, Hartmann number, Prandtl number, heat source/sink parameter, Schmidt number described graphically and in tabular form. It is observed that the velocity profile increases by increasing mixed convection parameter and concentration buoyancy parameter. The temperature enhances for larger values of Hartmann number and Brownian. The concentration profile increases by increasing thermophoresis parameter. Results show that wall shear stress increases by increasing couple stress parameter and ratio of oscillating frequency to stretching rate. Keywords: Oscillatory surface, Couple stress fluid, Nanoparticles, Heat absorption/generation

Cosmological Parameters 2000

OpenAIRE

Primack, Joel R.

2000-01-01

The cosmological parameters that I emphasize are the age of the universe $t_0$, the Hubble parameter $H_0 \\equiv 100 h$ km s$^{-1}$ Mpc$^{-1}$, the average matter density $\\Omega_m$, the baryonic matter density $\\Omega_b$, the neutrino density $\\Omega_\

Theory of charged vector mesons interacting with the electromagnetic field

International Nuclear Information System (INIS)

Lee, T.D.; Yang, C.N.

1983-01-01

It is shown that starting from the usual canonical formalism for the electromagnetic interaction of a charged vector meson with arbitrary magnetic moment one is led to a set of rules for Feynman diagrams, which appears to contain terms that are both infinite and noncovariant. These difficulties, however, can be circumvented by introducing a xi-limiting process which depends on a dimensionless positive parameter xi → 0. Furthermore, by using the mathematical artifice of a negative metric the theory becomes renormalizable (for xi > 0)

Levitation of the quantum Hall extended states in the $B\\to$ 0 limit

OpenAIRE

Koschny, Th.; Schweitzer, L.

2004-01-01

We investigate the fate of the quantum Hall extended states within a continuum model with spatially correlated disorder potentials. The model can be projected onto a couple of the lowest Landau bands. Levitation of the $n=0$ critical states is observed if at least the two lowest Landau bands are considered. The dependence on the magnetic length $l_B=(\\hbar/(eB))^{1/2}$ and on the correlation length of the disorder potential $\\eta$ is combined into a single dimensionless parameter $\\hat\\eta=\\e...

Gas evolution from spheres

Science.gov (United States)

Longhurst, G. R.

1991-04-01

Gas evolution from spherical solids or liquids where no convective processes are active is analyzed. Three problem classes are considered: (1) constant concentration boundary, (2) Henry's law (first order) boundary, and (3) Sieverts' law (second order) boundary. General expressions are derived for dimensionless times and transport parameters appropriate to each of the classes considered. However, in the second order case, the non-linearities of the problem require the presence of explicit dimensional variables in the solution. Sample problems are solved to illustrate the method.

e+e- inclusive distributions, jets and 2-dim QCD

International Nuclear Information System (INIS)

Triantafillou, V.V.

1978-02-01

Motivated by the presence of jets, we calculate inclusive distributions of hadrons produced in e + e - collisions in the framework of 1 + 1 dimensional QCD of 't Hooft. The dimensionless quantity 1/sigmasub(tot) dsigma/dz, which is determined solely by the meson wave functions and is independent of all parameters of the theory, agrees well with the existing experimental data. We give also the inclusive distributions for PSI, D, F and a heavy quark mesons in high energy e + e - experiments. (orig.) [de

Similarity in problems related to zero-gravity hydromechanics

International Nuclear Information System (INIS)

Volkov, P K

1998-01-01

On introduction of gravitational acceleration into the calculation of length and velocity scales, a set of dimensionless parameters appears in the mathematical model which enable the behaviour of convection and heat and mass transfer under changing gravitational conditions to be predicted. By directly simulating the equations of motion and heat transfer, the effectiveness of the proposed formulation of conservation laws in treating such phenomena in liquids is demonstrated for both isothermal and non-isothermal cases and under both terrestrial and space conditions. (methodological notes)

Dark energy and the BOOMERANG data.

Science.gov (United States)

Amendola, L

2001-01-08

The recent high-quality BOOMERANG data allow the testing of many competing cosmological models. Here I present a seven-parameter likelihood analysis of dark energy models with exponential potential and explicit coupling to dark matter. The BOOMERANG data constrain the dimensionless coupling beta to be smaller than 0.1, an order of magnitude better than previous limits. In terms of the constant xi of nonminimally coupled theories, this amounts to xiBOOMERANG does not have enough sensitivity to put constraints on the potential slope.

Correlations among Stress Parameters, Meat and Carcass Quality Parameters in Pigs

Science.gov (United States)

Dokmanovic, Marija; Baltic, Milan Z.; Duric, Jelena; Ivanovic, Jelena; Popovic, Ljuba; Todorovic, Milica; Markovic, Radmila; Pantic, Srdan

2015-01-01

Relationships among different stress parameters (lairage time and blood level of lactate and cortisol), meat quality parameters (initial and ultimate pH value, temperature, drip loss, sensory and instrumental colour, marbling) and carcass quality parameters (degree of rigor mortis and skin damages, hot carcass weight, carcass fat thickness, meatiness) were determined in pigs (n = 100) using Pearson correlations. After longer lairage, blood lactate (prigor mortis (p<0.05), suggesting that lactate could be a predictor of both meat quality and the level of preslaughter stress. Cortisol affected carcass quality, so higher levels of cortisol were associated with increased hot carcass weight, carcass fat thickness on the back and at the sacrum and marbling, but also with decreased meatiness. The most important meat quality parameters (pH and temperature after 60 minutes) deteriorated when blood lactate concentration was above 12 mmol/L. PMID:25656214

Bomb parameters

International Nuclear Information System (INIS)

Kerr, George D.; Young, Rebert W.; Cullings, Harry M.; Christry, Robert F.

2005-01-01

The reconstruction of neutron and gamma-ray doses at Hiroshima and Nagasaki begins with a determination of the parameters describing the explosion. The calculations of the air transported radiation fields and survivor doses from the Hiroshima and Nagasaki bombs require knowledge of a variety of parameters related to the explosions. These various parameters include the heading of the bomber when the bomb was released, the epicenters of the explosions, the bomb yields, and the tilt of the bombs at time of explosion. The epicenter of a bomb is the explosion point in air that is specified in terms of a burst height and a hypocenter (or the point on the ground directly below the epicenter of the explosion). The current reassessment refines the energy yield and burst height for the Hiroshima bomb, as well as the locations of the Hiroshima and Nagasaki hypocenters on the modern city maps used in the analysis of the activation data for neutrons and TLD data for gamma rays. (J.P.N.)

Magnetic S-parameter

DEFF Research Database (Denmark)

Sannino, Francesco

2010-01-01

We propose a direct test of the existence of gauge duals for nonsupersymmetric asymptotically free gauge theories developing an infrared fixed point by computing the S-parameter in the electric and dual magnetic description. In particular we show that at the lower bound of the conformal window...... the magnetic S-parameter, i.e. the one determined via the dual magnetic gauge theory, assumes a simple expression in terms of the elementary magnetic degrees of freedom. The results further support our recent conjecture of the existence of a universal lower bound on the S parameter and indicates...

A CALCULATION METHOD OF TRANSIENT MODES OF ELECTRIC SHIPS’ PROPELLING ELECTRIC PLANTS

Directory of Open Access Journals (Sweden)

V. A. Yarovenko

2017-12-01

Full Text Available The purpose of the work is to develop the method for calculating the transient modes of electric ships’ propelling electric plants during maneuver. This will allow us to evaluate and improve the maneuverability of vessels with electric motion. Methodology. The solution to the problems is proposed to be carried out on the basis of mathematical modeling of maneuvering modes. The duration of transient modes in an electric power plant at electric ships’ maneuvers is commensurable with the transient operation modes of the vessel itself. Therefore, the analysis of the electric power plants’ maneuvering modes should be made in unity with all the components of the ship’s propulsion complex. Results. A specified mathematical model of transient regimes of electric ship’s propulsion complex, including thermal motors, synchronous generators, electric power converters, propulsion motors, propellers, rudder, ship’s hull is developed. The model is universal. It covers the vast majority of modern and promising electric ships with a traditional type of propulsors. It allows calculating the current values of the basic mode indicators and assessing the quality indicators of maneuvering. The model is made in relative units. Dimensionless parameters of the complex are obtained. These parameters influence the main indicators of the quality of maneuvering. The adequacy of the suggested specified mathematical model and the developed computation method based on it were confirmed. To do this, the results of mathematical modeling for a real electric ship were compared with the data obtained in the course of field experiments conducted by other researchers. Originality. The mathematical description of a generator unit, as an integral part of an indivisible ship’s propulsion complex, makes it possible to calculate the dynamic operation modes of electric power sources during electric vessels’ maneuvering. There is an opportunity to design the electric ships�

Department of Defense Weapon System Acquisition Policy: A System Dynamics Model and Analysis.

Science.gov (United States)

1982-09-01

dimensionless) PRPRD = Perceived Pressure for R&D (dimensionless) PU - Programs in Progress (programs) RPRD - Raw Pressure for R&D (dimensionless) TDPP - Time...ECAP) TH9 Pressure Ra Pressure_.- for Acquisition ( TDPP ) TH25 4for Acquisition (DPFAO) TH22D (DPPFAO) TH21 US Intelligence \\ - 7 Delay Time / efense...DIBP, DPPFAQ. K) TH22 A CPPFAG.K=DLINF3(RPFAG.KTCPP) TH23 A CPFAQ.K=MAX (DIBPCPPFAQ.K) TH24 C TDPP =12 TH25 C TCPP-24 TH26 CPFAQ Congressional Pressure

Irreversibility analysis of magneto-hydrodynamic nanofluid flow injected through a rotary disk

Directory of Open Access Journals (Sweden)

Rashidi Mohammad Mehdi

2015-01-01

Full Text Available The non-linear Navier-Stokes equations governed on the nanofluid flow injected through a rotary porous disk in the presence of an external uniform vertical magnetic field can be changed to a system of non-linear partial differential equations by applying similar parameter. In this study, partial differential equations are analytically solved by the modified differential transform method, Pade differential transformation method to obtain self-similar functions of motion and temperature. A very good agreement is observed between the obtained results of Pade differential transformation method and those of previously published ones. Then it has become possible to do a comprehensive parametric analysis on the entropy generation in this case to demonstrate the effects of physical flow parameters such as magnetic interaction parameter, injection parameter, nanoparticle volume fraction, dimensionless temperature difference, rotational Brinkman number and the type of nanofluid on the problem.

New bounds on isotropic Lorentz violation

International Nuclear Information System (INIS)

Carone, Christopher D.; Sher, Marc; Vanderhaeghen, Marc

2006-01-01

Violations of Lorentz invariance that appear via operators of dimension four or less are completely parametrized in the Standard Model Extension (SME). In the pure photonic sector of the SME, there are 19 dimensionless, Lorentz-violating parameters. Eighteen of these have experimental upper bounds ranging between 10 -11 and 10 -32 ; the remaining parameter, k-tilde tr , is isotropic and has a much weaker bound of order 10 -4 . In this Brief Report, we point out that k-tilde tr gives a significant contribution to the anomalous magnetic moment of the electron and find a new upper bound of order 10 -8 . With reasonable assumptions, we further show that this bound may be improved to 10 -14 by considering the renormalization of other Lorentz-violating parameters that are more tightly constrained. Using similar renormalization arguments, we also estimate bounds on Lorentz-violating parameters in the pure gluonic sector of QCD

Disorder parameter of confinement

International Nuclear Information System (INIS)

Nakamura, N.; Ejiri, S.; Matsubara, Y.; Suzuki, T.

1996-01-01

The disorder parameter of confinement-deconfinement phase transition based on the monopole action determined previously in SU(2) QCD are investigated. We construct an operator which corresponds to the order parameter defined in the abelian Higgs model. The operator shows proper behaviors as the disorder parameter in the numerical simulations of finite temperature QCD. (orig.)

A simple model for calculating air pollution within street canyons

Science.gov (United States)

Venegas, Laura E.; Mazzeo, Nicolás A.; Dezzutti, Mariana C.

2014-04-01

This paper introduces the Semi-Empirical Urban Street (SEUS) model. SEUS is a simple mathematical model based on the scaling of air pollution concentration inside street canyons employing the emission rate, the width of the canyon, the dispersive velocity scale and the background concentration. Dispersive velocity scale depends on turbulent motions related to wind and traffic. The parameterisations of these turbulent motions include two dimensionless empirical parameters. Functional forms of these parameters have been obtained from full scale data measured in street canyons at four European cities. The sensitivity of SEUS model is studied analytically. Results show that relative errors in the evaluation of the two dimensionless empirical parameters have less influence on model uncertainties than uncertainties in other input variables. The model estimates NO2 concentrations using a simple photochemistry scheme. SEUS is applied to estimate NOx and NO2 hourly concentrations in an irregular and busy street canyon in the city of Buenos Aires. The statistical evaluation of results shows that there is a good agreement between estimated and observed hourly concentrations (e.g. fractional bias are -10.3% for NOx and +7.8% for NO2). The agreement between the estimated and observed values has also been analysed in terms of its dependence on wind speed and direction. The model shows a better performance for wind speeds >2 m s-1 than for lower wind speeds and for leeward situations than for others. No significant discrepancies have been found between the results of the proposed model and that of a widely used operational dispersion model (OSPM), both using the same input information.

Coarse-grained debris flow dynamics on erodible beds

Science.gov (United States)

Lanzoni, Stefano; Gregoretti, Carlo; Stancanelli, Laura Maria

2017-03-01

A systematic set of flume experiments is used to investigate the features of velocity profiles within the body of coarse-grained debris flows and the dependence of the transport sediment concentration on the relevant parameters (runoff discharge, bed slope, grain size, and form). The flows are generated in a 10 m long laboratory flume, initially filled with a layer consisting of loose debris. After saturation, a prescribed water discharge is suddenly supplied over the granular bed, and the runoff triggers a debris flow wave that reaches nearly steady conditions. Three types of material have been used in the tests: gravel with mean grain size of 3 and 5 mm, and 3 mm glass spheres. Measured parameters included: triggering water discharge, volumetric sediment discharge, sediment concentration, flow depth, and velocity profiles. The dynamic similarity with full-sized debris flows is discussed on the basis of the relevant dimensionless parameters. Concentration data highlight the dependence on the slope angle and the importance of the quasi-static friction angle. The effects of flow rheology on the shape of velocity profiles are analyzed with attention to the role of different stress-generating mechanisms. A remarkable collapse of the dimensionless profiles is obtained by scaling the debris flow velocity with the runoff velocity, and a power law characterization is proposed following a heuristic approach. The shape of the profiles suggests a smooth transition between the different rheological regimes (collisional and frictional) that establish in the upper and lower regions of the flow and is compatible with the presence of multiple length scales dictated by the type of contacts (instantaneous or long lasting) between grains.

Reactor similarity for plasma–material interactions in scaled-down tokamaks as the basis for the Vulcan conceptual design

International Nuclear Information System (INIS)

Whyte, D.G.; Olynyk, G.M.; Barnard, H.S.; Bonoli, P.T.; Bromberg, L.; Garrett, M.L.; Haakonsen, C.B.; Hartwig, Z.S.; Mumgaard, R.T.; Podpaly, Y.A.

2012-01-01

Highlights: ► Discussion of similarity scalings for reduced-size tokamaks. ► Proposal of a new set of scaling laws for divertor similarity. ► Discussion of how the new scaling provides fidelity to a reactor. ► The new scaling is used as the basis for the Vulcan conceptual design. - Abstract: Dimensionless parameter scaling techniques are a powerful tool in the study of complex physical systems, especially in tokamak fusion experiments where the cost of full-size devices is high. It is proposed that dimensionless similarity be used to study in a small-scale device the coupled issues of the scrape-off layer (SOL) plasma, plasma–material interactions (PMI), and the plasma-facing material (PFM) response expected in a tokamak fusion reactor. Complete similarity is not possible in a reduced-size device. In addition, “hard” technological limits on the achievable magnetic field and peak heat flux, as well as the necessity to produce non-inductive scenarios, must be taken into account. A practical approach is advocated, in which the most important dimensionless parameters are matched to a reactor in the reduced-size device, while relaxing those parameters which are far from a threshold in behavior. “Hard” technological limits are avoided, so that the reduced-size device is technologically feasible. A criticism on these grounds is offered of the “P/R” model, in which the ratio of power crossing the last closed flux surface (LCFS), P, to the device major radius, R, is held constant. A new set of scaling rules, referred to as the “P/S” scaling (where S is the LCFS area) or the “PMI” scaling, is proposed: (i) non-inductive, steady-state operation; (ii) P is scaled with R 2 so that LCFS areal power flux P/S is constant; (iii) magnetic field B constant; (iv) geometry (elongation, safety factor q * , etc.) constant; (v) volume-averaged core density scaled as n≈n ¯ e ∼R −2/7 ; and (vi) ambient wall material temperature T W,0 constant. It is

Wavenumber Spectrum of Intermediate-Scale Ocean Surface Waves

National Research Council Canada - National Science Library

Hwang, Paul A

2005-01-01

... (wavelengths between 0.02 and 6 m) under various sea-state conditions. The main result of the analysis is that the dependence of the dimensionless wave spectrum on the dimensionless wind friction velocity follows a power-law function...

Mixed Convection Flow of Magnetic Viscoelastic Polymer from a Nonisothermal Wedge with Biot Number Effects

Directory of Open Access Journals (Sweden)

S. Abdul Gaffar

2015-01-01

Full Text Available Magnetic polymers are finding increasing applications in diverse fields of chemical and mechanical engineering. In this paper, we investigate the nonlinear steady boundary layer flow and heat transfer of such fluids from a nonisothermal wedge. The incompressible Eyring-Powell non-Newtonian fluid model is employed and a magnetohydrodynamic body force is included in the simulation. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a second-order accurate implicit finite difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging nondimensional parameters, namely, the Eyring-Powell rheological fluid parameter (ε, local non-Newtonian parameter based on length scale (δ, Prandtl number (Pr, Biot number (γ, pressure gradient parameter (m, magnetic parameter (M, mixed convection parameter (λ, and dimensionless tangential coordinate (ξ, on velocity and temperature evolution in the boundary layer regime is examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate and local skin friction are also investigated.

Uncertainty analysis of flexible rotors considering fuzzy parameters and fuzzy-random parameters

Directory of Open Access Journals (Sweden)

Fabian Andres Lara-Molina

Full Text Available Abstract The components of flexible rotors are subjected to uncertainties. The main sources of uncertainties include the variation of mechanical properties. This contribution aims at analyzing the dynamics of flexible rotors under uncertain parameters modeled as fuzzy and fuzzy random variables. The uncertainty analysis encompasses the modeling of uncertain parameters and the numerical simulation of the corresponding flexible rotor model by using an approach based on fuzzy dynamic analysis. The numerical simulation is accomplished by mapping the fuzzy parameters of the deterministic flexible rotor model. Thereby, the flexible rotor is modeled by using both the Fuzzy Finite Element Method and the Fuzzy Stochastic Finite Element Method. Numerical simulations illustrate the methodology conveyed in terms of orbits and frequency response functions subject to uncertain parameters.

Correlations between skin hydration parameters and corneocyte-derived parameters to characterize skin conditions.

Science.gov (United States)

Masaki, Hitoshi; Yamashita, Yuki; Kyotani, Daiki; Honda, Tatsuya; Takano, Kenichi; Tamura, Toshiyasu; Mizutani, Taeko; Okano, Yuri

2018-03-30

Skin hydration is generally assessed using the parameters of skin surface water content (SWC) and trans-epidermal water loss (TEWL). To date, few studies have characterized skin conditions using correlations between skin hydration parameters and corneocyte parameters. The parameters SWC and TEWL allow the classification of skin conditions into four distinct Groups. The purpose of this study was to assess the characteristics of skin conditions classified by SWC and TEWL for correlations with parameters from corneocytes. A human volunteer test was conducted that measured SWC and TEWL. As corneocyte-derived parameters, the size and thick abrasion ratios, the ratio of sulfhydryl groups and disulfide bonds (SH/SS) and CP levels were analyzed. Volunteers were classified by their median SWC and TEWL values into 4 Groups: Group I (high SWC/low TEWL), Group II (high SWC/high TEWL), Group III (low SWC/low TEWL), and Group IV (low SWC/high TEWL). Group IV showed a significantly smaller size of corneocytes. Groups III and IV had significantly higher thick abrasion ratios and CP levels. Group I had a significantly lower SH/SS value. The SWC/TEWL value showed a decline in order from Group I to Group IV. Groups classified by their SWC and TEWL values showed characteristic skin conditions. We propose that the SWC and TEWL ratio is a comprehensive parameter to assess skin conditions. © 2018 Wiley Periodicals, Inc.

Cosmological Parameters and Hyper-Parameters: The Hubble Constant from Boomerang and Maxima

Science.gov (United States)

Lahav, Ofer

Recently several studies have jointly analysed data from different cosmological probes with the motivation of estimating cosmological parameters. Here we generalise this procedure to allow freedom in the relative weights of various probes. This is done by including in the joint likelihood function a set of `Hyper-Parameters', which are dealt with using Bayesian considerations. The resulting algorithm, which assumes uniform priors on the log of the Hyper-Parameters, is very simple to implement. We illustrate the method by estimating the Hubble constant H0 from different sets of recent CMB experiments (including Saskatoon, Python V, MSAM1, TOCO, Boomerang and Maxima). The approach can be generalised for a combination of cosmic probes, and for other priors on the Hyper-Parameters. Reference: Lahav, Bridle, Hobson, Lasenby & Sodre, 2000, MNRAS, in press (astro-ph/9912105)

Theoretical study of chemical reaction effects on vertical oscillating plate with variable temperature

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2006-01-01

Full Text Available An exact solution to the flow of a viscous incompressible unsteady flow past an infinite vertical oscillating plate with variable temperature and mass diffusion is presented here, taking into account of the homogeneous chemical reaction of first-order. Both the plate temperature and the concentration level near the plate are raised linearly with respect to time. The dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The effects of velocity and concentration are studied for different parameters like phase angle, chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number and time are studied. The solutions are valid only for small values of time t. It is observed that the velocity increases with decreasing phase angle ωt or chemical reaction parameter. .

Mass transfer effects on vertical oscillating plate with heat flux

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2007-01-01

Full Text Available Theoretical solution of unsteady viscous incompressible flow past an infinite vertical oscillating plate with uniform heat flux and mass diffusion is presented here, taking into account of the homogeneous chemical reaction of first-order. The temperature from the plate to the fluid at an uniform rate and the mass is diffused uniformly. The dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The effects of velocity and concentration are studied for different parameters like phase angle chemical reaction parameter, thermal Grashof number, mass Grashof number Schmidt number and time are studied. The so­lutions are valid only for small values of time t. It is observed that the velocity increases with decreasing phase angle ωt or chemical reaction parameter.

Heat and mass transfer of a second grade magnetohydrodynamic fluid over a convectively heated stretching sheet

Directory of Open Access Journals (Sweden)

Kalidas Das

2016-10-01

Full Text Available The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge–Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.

Quasi-equilibria and plasma chemical similarity in non-isothermal reactive plasmas

International Nuclear Information System (INIS)

Miethke, F.; Rutscher, A.; Wagner, H.E.

2000-01-01

With regard to the output of stable products the mode of operation of non-isothermal plasma chemical reactors shows physical and chemical well defined states, which represent limiting cases and may be interpreted as quasi-equilibrium states. The occurrence and the characteristics of these states, meanwhile more than once observed and described, are demonstrated by an instructive model reaction. Within the frame of the so-called Macroscopic Kinetics a central parameter is dominating the reactor operation. This result may be generalized and is linked up to the application of similarity principles for the reactor operation. After the general formulation of such principles, starting from the balance equations of particles and energy, a dimensionless similarity parameter is formulated, characterizing the composition of the effluent gas of the reactor. The applicability of this parameter is demonstrated by experimental examples. (Authors)

Numerical modeling of heat transfer in the fuel oil storage tank at thermal power plant

Directory of Open Access Journals (Sweden)

Kuznetsova Svetlana A.

2015-01-01

Full Text Available Presents results of mathematical modeling of convection of a viscous incompressible fluid in a rectangular cavity with conducting walls of finite thickness in the presence of a local source of heat in the bottom of the field in terms of convective heat exchange with the environment. A mathematical model is formulated in terms of dimensionless variables “stream function – vorticity vector speed – temperature” in the Cartesian coordinate system. As the results show the distributions of hydrodynamic parameters and temperatures using different boundary conditions on the local heat source.

Unsteady natural convection flow past an accelerated vertical plate in a thermally stratified fluid

Directory of Open Access Journals (Sweden)

Deka Rudra Kt.

2009-01-01

Full Text Available An exact solution to one-dimensional unsteady natural convection flow past an infinite vertical accelerated plate, immersed in a viscous thermally stratified fluid is investigated. Pressure work term and the vertical temperature advection are considered in the thermodynamic energy equation. The dimensionless governing equations are solved by Laplace Transform techniques for the Prandtl number unity. The velocity and temperature profiles as well as the skin-friction and the rate of heat transfer are presented graphically and discussed the effects of the Grashof number Gr, stratification parameter S at various times t.

An asymptotic analytical solution to the problem of two moving boundaries with fractional diffusion in one-dimensional drug release devices

International Nuclear Information System (INIS)

Yin Chen; Xu Mingyu

2009-01-01

We set up a one-dimensional mathematical model with a Caputo fractional operator of a drug released from a polymeric matrix that can be dissolved into a solvent. A two moving boundaries problem in fractional anomalous diffusion (in time) with order α element of (0, 1] under the assumption that the dissolving boundary can be dissolved slowly is presented in this paper. The two-parameter regular perturbation technique and Fourier and Laplace transform methods are used. A dimensionless asymptotic analytical solution is given in terms of the Wright function

Continuum theory for nanotube piezoelectricity.

Science.gov (United States)

Michalski, P J; Sai, Na; Mele, E J

2005-09-09

We develop and solve a continuum theory for the piezoelectric response of one-dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in boron-nitride nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and electrostatic interactions. The solutions of the model as these two parameters are varied are discussed. The theory is applied to estimate the electric potential induced along the length of a boron-nitride nanotube in response to a uniaxial stress.

Thermal hydraulic phenomena in corium pools: the BALI experiment

International Nuclear Information System (INIS)

Bonnet, J.M.

1999-01-01

In the framework of severe accident studies, the BALI experiment has been designed to create a data base about heat transfer distribution at corium pool boundaries for in-vessel or ex-vessel configurations. The mechanism investigated is natural convection at high internal Rayleigh number (10 15 to 10 17 ) in cavities with volumetric heating. After a description of the facility and a synthesis of results obtained for in-vessel configurations, the purpose of this paper is to present or extend local or average heat transfer correlations in the prototypic range of dimensionless parameters. (author)

Estimating unsaturated hydraulic conductivity from soil moisture-tim function

International Nuclear Information System (INIS)

El Gendy, R.W.

2002-01-01

The unsaturated hydraulic conductivity for soil can be estimated from o(t) function, and the dimensionless soil water content parameter (Se)Se (β - βr)/ (φ - θ)), where θ, is the soil water content at any time (from soil moisture depletion curve l; θ is the residual water content and θ, is the total soil porosity (equals saturation point). Se can be represented as a time function (Se = a t b ), where t, is the measurement time and (a and b) are the regression constants. The recommended equation in this method is given by

Structuring polymer blends with bicontinuous phase morphology. Part II. Tailoring blends with ultralow critical volume fraction

DEFF Research Database (Denmark)

Lyngaae-Jørgensen, Jørgen; Utracki, Leszek

2003-01-01

A hypothesis providing a guideline for the development of immiscible polymer blends with co-continuous phase structure at very low critical volume fraction of one component is. postulated and experimentally verified. Based on a number of simplifying assumptions the following relation was derived......: phi(cr) = k(lambdagamma)(1-z)/(theta(b)(*))(z) where lambdagamma is a Deborah number and theta(b)(*) is a dimensionless break-up time. The equation parameters, k and z are constant that depend on the flow field hence on the blending equipment. For the studies an internal mixer with Walzenkneter...

Aerosol behaviour in an acoustic field

International Nuclear Information System (INIS)

Malherbe, C.

1985-01-01

The average size of an aerosol submitted to acoustic waves is increased. This results from coagulation of the finest particles on the largest ones. The mechanisms responsible for acoustic agglomeration are mentioned. An experimental apparatus was developed in order to control the evolution of aerosol distribution in an acoustic field. Important deposition on the walls of the agglomeration chamber was observed as a consequence of the acoustically induced turbulent flow. Finally, a dimensionless relationship was established between deposition rates and particle diameters as a function of experimental parameters (aeraulic and acoustic conditions, etc...) [fr

Korteweg de Vries Description of One-Dimensional Superfluid Fermi Gases

International Nuclear Information System (INIS)

Xu Yan-Xia; Duan Wen-Shan

2011-01-01

We study one-dimensional matter-wave pulses in cigar-shaped superfluid Fermi gases, including the linear and nonlinear waves of the system. A Korteweg de Vries (KdV) solitary wave is obtained for the superfluid Fermi gases in the limited case of a BEC regime, a BCS regime and unitarity. The dependences of the propagation velocity, amplitude and the width of the solitary wave on the dimensionless interaction parameter y = 1/(k F a sc ) are given for the limited cases of BEC and unitarity. (physics of gases, plasmas, and electric discharges)

Fractional single-phase-lagging heat conduction model for describing anomalous diffusion

Directory of Open Access Journals (Sweden)

T.N. Mishra

2016-03-01

Full Text Available The fractional single-phase-lagging (FSPL heat conduction model is obtained by combining scalar time fractional conservation equation to the single-phase-lagging (SPL heat conduction model. Based on the FSPL heat conduction model, anomalous diffusion within a finite thin film is investigated. The effect of different parameters on solution has been observed and studied the asymptotic behavior of the FSPL model. The analytical solution is obtained using Laplace transform method. The whole analysis is presented in dimensionless form. Numerical examples of particular interest have been studied and discussed in details.

Flooding in a loop with a vertical and a horizontal tube connected by an elbow

International Nuclear Information System (INIS)

Yan Changqi

1994-01-01

The experimental research of flooding and flow-reverse in a test loop which a vertical and a horizontal tube connected by an elbow is introduced. According to the experimental results, the effects of the elbow on flooding and flow-reverse is analyzed. The experimental results is compared with the results obtained in vertical tubes. The effect of horizontal tube length and hysteresis in de-flooding are analyzed. Dimensionless parameters was used in data process. The correlations for predicting the flooding point, de-flooding point, completed carry up and flow reverse points are given

Use of ultrasound to monitor physical properties of soybean oil

Science.gov (United States)

Baêsso, R. M.; Oliveira, P. A.; Morais, G. C.; Alvarenga, A. V.; Costa-Félix, R. P. B.

2016-07-01

The study of the monitoring physical properties of soybean oil was performed. The pulse-echo method allowed measuring the density and viscosity of the oil in real time and accurately. The physical property values were related to the acoustic time of flight ratio, dimensionless parameter that can be obtained from any reference. In our case, we used the time of flight at 20°C as reference and a fixed distance between the transducer and the reflector. Ultrasonic monitoring technique employed here has shown promising in the analysis of edible oils.

Using of dimensional analysis to determine the parameters of gravity separator table device to minimize impurities in bulk lentils

Directory of Open Access Journals (Sweden)

H Bagheri

2017-05-01

Full Text Available Introduction Lentil (Lens culinaris medic is an important and highly nutritious crop belonging to the family of legumes. Lentil is cultivated worldwide but competition with weeds is a problem affecting production and can reduce yield by more than 80%. The study on the separation of impurities in bulk lentils (Euphorbia helioscopia weed, Wild oat weed and etc. by a gravity separator has an extreme importance. Since no study has been done to date, in this study, the effects of different parameters of a gravity separator (longitudinal and latitudinal slopes, oscillation frequency and amplitude on the separation of foreign matters in lentil seeds were evaluated. A dimensionless number (v/aω which shows ration of air current velocity blown to lentil to the maximum velocity of table oscillation, was considered in ratio of separation. Materials and Methods In this research, lentil samples were taken from farms in Ardebil Province (Bileh-Savar cultivar. A gravity separator apparatus was also used for separating impurities from lentil seeds. A Laboratory Gravity Separator Type LA-K (Westrup A/S Denmark was used to separate impurities from bulk lentils. In this machine, table settings were as follows; longitudinal slope parameters (1°,1.5°, 1.75°, 2° and 2.5°, latitudinal slope (0.5°, 1°, and 1.5°, frequency of oscillation (380, 400, 420 and 450 cycles min-1, and amplitude of oscillation (5 and 7 mm, these settings were all adjustable. Similarly, the instrument had 5 boxes whereby, through proper adjustment, the heavier material was transferred toward the right side of the table and lighter material moved toward the left side. Through proper adjustment of the main parameters of the instrument, the impurities were separated from bulk lentils. Then using an electronic seed counter, five groups of seed which each group containing 100 seeds were counted and selected. Results and Discussion The results of variance analysis of the factorial design with

Untitled

Indian Academy of Sciences (India)

, A, to model input, q},. Sp particle surface area, mi,. T temperature, K,. Tm mean temperature, (T + 6T)/(1 +6),. U overall heat transfer coefficient, J/mº K s, dimensionless temperature, T/T., maximum value of dimensionless temperature. y mean ...

Dictionary of scientific units including dimensionless numbers and scales

National Research Council Canada - National Science Library

Jerrard, H.G; McNeill, D.B

1992-01-01

.... The text includes the most recently accepted values of all units. Several disciplines, which have in the past employed few scientific principles and the dictionary has been extended to include examples of these.

Modeling of similar economies

Directory of Open Access Journals (Sweden)

Sergey B. Kuznetsov

2017-06-01

Full Text Available Objective to obtain dimensionless criteria ndash economic indices characterizing the national economy and not depending on its size. Methods mathematical modeling theory of dimensions processing statistical data. Results basing on differential equations describing the national economy with the account of economical environment resistance two dimensionless criteria are obtained which allow to compare economies regardless of their sizes. With the theory of dimensions we show that the obtained indices are not accidental. We demonstrate the implementation of the obtained dimensionless criteria for the analysis of behavior of certain countriesrsquo economies. Scientific novelty the dimensionless criteria are obtained ndash economic indices which allow to compare economies regardless of their sizes and to analyze the dynamic changes in the economies with time. nbsp Practical significance the obtained results can be used for dynamic and comparative analysis of different countriesrsquo economies regardless of their sizes.

Transient Response and Steady-State Analysis of the Anode of Direct Methanol Fuel Cells Based on Dual-Site Kinetics

Directory of Open Access Journals (Sweden)

Lei Xing

2011-01-01

Full Text Available An intrinsic time-dependent one-dimensional (1D model and a macro two-dimensional (2D model for the anode of the direct methanol fuel cell (DMFC are presented. The two models are based on the dual-site mechanism, which includes the coverage of intermediate species of methanol, OH, and CO (θM, θOH,Ru, and θCO,Pt on the surface of Pt and Ru. The intrinsic 1D model focused on the analysis of the effects of operating temperature, methanol concentration, and overpotential on the transient response. The macro 2D model emphasises the dimensionless distributions of methanol concentration, overpotential and current density in the catalyst layer which were affected by physical parameters such as thickness, specific area, and operating conditions such as temperature, bulk methanol concentration, and overpotential. The models were developed and solved in the PDEs module of COMSOL Multiphysics, giving good agreement with experimental data. The dimensionless distributions of methanol concentration, overpotential, and current density and the efficiency factor were calculated quantitatively. The models can be used to give accurate simulations for the polarisations of methanol fuel cell.

Mathematical method for the study and teaching of stellar and protostellar structure

International Nuclear Information System (INIS)

Doorish, J.F.

1988-01-01

The purpose of this thesis is to develop a relatively simple yet effective method of teaching stellar and protostellar structure. There are four differential equations describing the structure of a star. These equations are linearly approximated in the following form: W = W 0 (1 ± wx). Here, W represents the pressure (P), temperature (T), mass (M), and/or luminosity (L) gradients within the star; W represents some initial value of these parameters expanded inwardly or outwardly from an initial point, r 0 ; and w represents what is called the Motz Dimensionless Variables (MDV) which are directly derivable from the above set of equations. They are dimensionless, so, in the expansion, W has the same units as w 0 . In the set of equations describing the MDV, if the surface of the star is expanded to larger values, representing earlier, and therefore, protostellar stages of the star, by theoretically halting accretion, no dynamical factors need to be considered. The set of equations describing a stellar structure in static equilibrium may then be used. This method was designed for college and early graduate students who have never before encountered the topic of stellar structure

Pore to core scale simulation of the mass transfer with mineral reaction in porous media

International Nuclear Information System (INIS)

Bekri, S.; Renard, S.; Delprat-Jannaud, F.

2015-01-01

Pore Network Model (PNM) is used to simulate mass transfer with mineral reaction in a single phase flow through porous medium which is here a sandstone sample from the reservoir formation of the Pakoslaw gas field. The void space of the porous medium is represented by an idealized geometry of pore-bodies joined by pore-throats. Parameters defining the pore-bodies and the pore-throats distribution are determined by an optimization process aiming to match the experimental Mercury Intrusion Capillary Pressure (MICP) curve and petrophysical properties of the rock such as intrinsic permeability and formation factor. The generated network is used first to simulate the multiphase flow by solving Kirchhoff's laws. The capillary pressure and relative permeability curves are derived. Then, reactive transport is addressed under asymptotic regime where the solute concentration undergoes an exponential evolution with time. The porosity/ permeability relationship and the three phenomenological coefficients of transport, namely the solute velocity, the dispersion and the mean reaction rate are determined as functions of Peclet and Peclet-Damkohler dimensionless numbers. Finally, the role of the dimensionless numbers on the reactive flow properties is highlighted. (authors)

Spreading of blood drops over dry porous substrate: complete wetting case.

Science.gov (United States)

Chao, Tzu Chieh; Arjmandi-Tash, Omid; Das, Diganta B; Starov, Victor M

2015-05-15

The process of dried blood spot sampling involves simultaneous spreading and penetration of blood into a porous filter paper with subsequent evaporation and drying. Spreading of small drops of blood, which is a non-Newtonian liquid, over a dry porous layer is investigated from both theoretical and experimental points of view. A system of two differential equations is derived, which describes the time evolution of radii of both the drop base and the wetted region inside the porous medium. The system of equations does not include any fitting parameters. The predicted time evolutions of both radii are compared with experimental data published earlier. For a given power law dependency of viscosity of blood with different hematocrit level, radii of both drop base and wetted region, and contact angle fell on three universal curves if appropriate scales are used with a plot of the dimensionless radii of the drop base and the wetted region inside the porous layer and dynamic contact angle on dimensionless time. The predicted theoretical relationships are three universal curves accounting satisfactorily for the experimental data. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Effects of rotation on MHD flow past an accelerated isothermal vertical plate with heat and mass diffusion

Directory of Open Access Journals (Sweden)

Muthucumaraswamy R.

2010-01-01

Full Text Available An exact analysis of rotation effects on unsteady flow of an incompressible and electrically conducting fluid past a uniformly accelerated infinite isothermal vertical plate, under the action of transversely applied magnetic field has been presented. The plate temperature is raised to Tw and the concentration level near the plate is also raised to C′w . The dimensionless governing equations are solved using Laplace-transform technique. The velocity profiles, temperature and concentration are studied for different physical parameters like thermal Grashof number, mass Grashof number, Schmidt number, Prandtl number and time. It is observed that the velocity increases with increasing values of thermal Grashof number or mass Grashof number. It is also observed that the velocity increases with decreasing magnetic field parameter.

Numerical study of the interaction between two laminar and coaxial plane jets with variable density in an ambient fluid

Energy Technology Data Exchange (ETDEWEB)

Kriaa, Wassim; Mhiri, Hatem; Le Palec, Georges E-mail: lepalec@unimeca.univ-mrs.fr; Bournot, Philippe

2003-07-01

In this work, we intend to solve the equations governing two laminar isothermal or non-isothermal coaxial plane jets with variable density in an ambient fluid at rest in order to study the initial conditions influence (i.e. the nozzles ejection conditions) on the jet characteristic parameters. A finite difference method is developed to solve the dimensionless Navier-Stokes and energy equations resulting from some assumptions. The discussion about the results relates primarily to the concentration core length according to the nozzles thicknesses ratios. The influences of the gas velocity and temperature resulting from the external nozzle are also examined. This made it possible to deduce correlations of practical use between these parameters in order to apply them in engineering processes.

Methods of Experimental Investigation of Cavitation in a Convergent - Divergent Nozzle of Rectangular Cross Section

Directory of Open Access Journals (Sweden)

Jablonská Jana

2016-08-01

Full Text Available Cavitation is a phenomenon with both positive and negative effects and with dynamic manifestations in hydraulic, food, chemical and other machinery. This article deals with the detection and dynamic behavior of cavitation clouds in water flows through a rectangular cross-section convergent-divergent nozzle. Cavitation was measured by methods applicable in engineering practice. Pressure, flow rate, noise, vibration, and amount of air dissolved in the liquid were measured and cavitation region was recorded with a high-speed camera. Evaluation of acquired images in connection with measured pressure pulsations and mechanical vibrations was performed with the use of the FFT method. In certain cases, dimensionless parameters were used to generalize the measurements. The results will be used to specify multiphase mathematical cavitation model parameters.

Effect of thermal radiation and suction on convective heat transfer of nanofluid along a wedge in the presence of heat generation/absorption

Energy Technology Data Exchange (ETDEWEB)

Kasmani, Ruhaila Md; Bhuvaneswari, M. [Centre for Foundation Studies in Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Sivasankaran, S.; Siri, Zailan [Institute of Mathematical Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2015-10-22

An analysis is presented to find the effects of thermal radiation and heat generation/absorption on convection heat transfer of nanofluid past a wedge in the presence of wall suction. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The resulting system is solved numerically using a fourth-order Runge–Kutta method with shooting technique. Numerical computations are carried out for different values of dimensionless parameters to predict the effects of wedge angle, thermophoresis, Brownian motion, heat generation/absorption, thermal radiation and suction. It is found that the temperature increases significantly when the value of the heat generation/absorption parameter increases. But the opposite observation is found for the effect of thermal radiation.

On the formation of fold-type oscillation marks in the continuous casting of steel.

Science.gov (United States)

Vynnycky, M; Saleem, S; Devine, K M; Florio, B J; Mitchell, S L; O'Brien, S B G

2017-06-01

Asymptotic methods are employed to revisit an earlier model for oscillation-mark formation in the continuous casting of steel. A systematic non-dimensionalization of the governing equations, which was not carried out previously, leads to a model with 12 dimensionless parameters. Analysis is provided in the same parameter regime as for the earlier model, and surprisingly simple analytical solutions are found for the oscillation-mark profiles; these are found to agree reasonably well with the numerical solution in the earlier model and very well with fold-type oscillation marks that have been obtained in more recent experimental work. The benefits of this approach, when compared with time-consuming numerical simulations, are discussed in the context of auxiliary models for macrosegregation and thermomechanical stresses and strains.

Oscillatory conductive heat transfer for a fiber in an ideal gas

Science.gov (United States)

Kuntz, H. L.; Perreira, N. D.

1985-01-01

A description of the thermal effects created by placing a cylindrical fiber in an inviscid, ideal gas, through which an acoustic wave propagates, is presented. The fibers and the gas have finite heat capacities and thermal conductivities. Expressions for the temperature distribution in the gas and in the material are determined. The temperature distribution is caused by pressure oscillations in the gas which, in turn, are caused by the passage of an acoustic wave. The relative value of a dimensionless parameter is found to be indicative of whether the exact or approximate equations should be used in the solution. This parameter is a function of the thermal conductivities and heat capacities of the fiber and gas, the acoustic frequency, and the fiber diameter.

Hydrodynamics of compressible superfluids in confined geometries

International Nuclear Information System (INIS)

Malmi-Kakkada, Abdul N; Valls, Oriol T; Dasgupta, Chandan

2014-01-01

We present a study of the hydrodynamics of compressible superfluids in confined geometries. We use a perturbative procedure in terms of the dimensionless expansion parameter (v/v s ) 2 where v is the typical speed of the flow and v s is the speed of sound. A zero value of this parameter corresponds to the incompressible limit. We apply the procedure to two specific problems: the case of a trapped superfluid with a Gaussian profile of the local density, and that of a superfluid confined in a rotating obstructed cylinder. We find that the corrections due to finite compressibility which are, as expected, negligible for liquid He, are important but amenable to the perturbative treatment for typical ultracold atomic systems. (paper)

Model of observed stochastic balance between work and free time supporting the LQTAI definition

DEFF Research Database (Denmark)

Ditlevsen, Ove Dalager

2008-01-01

A balance differential equation between free time and money-producing work time on the national economy level is formulated in a previous paper in terms of two dimensionless quantities, the fraction of work time and the total productivity factor defined as the ratio of the Gross Domestic Product...... significant systematically balance influencing parameters on the macro economical level than those considered in the definition in the previous paper of the Life Quality Time Allocation Index....... to the total salary paid in return for work. Among the solutions there is one relation that compares surprisingly well with the relevant sequences of Danish data spanning from 1948 to 2003, and also with similar data from several other countries except for slightly different model parameter values. Statistical...

Qualitative internal surface roughness classification using acoustic emission

International Nuclear Information System (INIS)

Mohd Hafizi Zohari; Mohd Hanif Saad

2009-04-01

This paper describes a novel new nondestructive method of qualitative internal surface roughness classification for pipes utilizing Acoustic Emission (AE) signal. Two different flowrate are introduced in a pipe obstructed using normally available components (e.g.: valve). The AE signal at suitable location from the obstruction are obtained and the peak amplitudes, RMS amplitude and energy of the AE signal are obtained. A dimensionless number, the Bangi Number, AB, is then calculated as a ratio of the AE parameters (peak amplitude, RMS amplitude or energy) in low flowrate measurement compared to the AE parameters in high flowrate measurement. It was observed that the Bangi Number, AB obtained can then be used to successfully discriminate between rough and smooth internal surface roughness. (author)

Simulation on Natural Convection of a Nanofluid along an Isothermal Inclined Plate

Science.gov (United States)

Mitra, Asish

2017-08-01

A numerical algorithm is presented for studying laminar natural convection flow of a nanofluid along an isothermal inclined plate. By means of similarity transformation, the original nonlinear partial differential equations of flow are transformed to a set of nonlinear ordinary differential equations. Subsequently they are reduced to a first order system and integrated using Newton Raphson and adaptive Runge-Kutta methods. The computer codes are developed for this numerical analysis in Matlab environment. Dimensionless velocity, temperature profiles and nanoparticle concentration for various angles of inclination are illustrated graphically. The effects of Prandtl number, Brownian motion parameter and thermophoresis parameter on Nusselt number are also discussed. The results of the present simulation are then compared with previous one available in literature with good agreement.

Magnetohydrodynamic pressure drop in a quickly changing magnetic field

International Nuclear Information System (INIS)

Xu, Z.Y.; Chen, J.M.; Qian, J.P.; Jiang, W.H.; Pan, C.J.; Li, W.Z.

1995-01-01

The magnetohydrodynamic (MHD) pressure drop of 22 Na 78 K flow in a circular duct was measured under a quickly changing magnetic field. The MHD pressure drop reduced with time as the magnetic field strength decreased. However, the dimensionless pressure drop gradient varied with the interaction parameter and had a higher value in the middle of the range of values of the interaction parameter. Therefore, a quickly changing magnetic field is harmful to the structural material in a liquid metal self-cooled blanket of a fusion reactor, since the greater pressure drop gradient may cause a larger stress in the blanket. This is even more harmful if the magnetic field strength decreases very quickly or its distribution in space is greatly non-uniform. (orig.)

Broadening of the lower hybrid kparallel spectrum by toroidal effects

International Nuclear Information System (INIS)

Barbato, E.; Romanelli, F.

1990-01-01

Toroidal geometry affects the evolution of k parallel (the component of the wave vector parallel to the magnetic field) along the lower hybrid, (LH) wave trajectories. In this paper such variations are investigated both analytically and numerically. The main parameters governing this phenomenon are found and how k parallel upshift can occur within this scheme is elucidated. As a figure of merit a k parallel - upshift factor is defined and discussed in a dimensionless parameter space in which all the LH experiments can be represented. Finally, a discussion of whether and when toroidal effects can fill the gap between the high phase velocity of the injected LH waves and the electron thermal velocity is presented by analyzing different experimental situations

A Straight-Line Method for Analyzing Residual Drawdowns at an Observation Well

Directory of Open Access Journals (Sweden)

Mesut Çimen

2015-01-01

Full Text Available Determination of the hydraulic parameters (transmissivity and storage coefficients of a confined aquifer is important for effective groundwater resources. For this purpose, the residual drawdowns have been in use to estimate the aquifer parameters by the classical Theis recovery method. The proposed method of this paper depends on a straight-line through the field data and it helps to calculate the parameters quickly without any need for long-term pumping data. It is based on the expansion series of the Theis well function by consideration of three terms, and this approach is valid for the dimensionless time factor u′=S′r2/4Tt′≤0.2. The method can be applied reliably to extensive and homogeneous confined aquifers resulting in different storage coefficients during the pumping and recovery periods S≠S′. It presents a strength methodology for the parameters decision making from the residual data in the groundwater field of civil engineering.

Development of global magnetohydrodynamic instabilities in Z-pinch plasmas in the presence of nonideal effects

International Nuclear Information System (INIS)

Sotnikov, V.I.; Bauer, B.S.; Leboeuf, J.N.; Hellinger, P.; Travnicek, P.; Fiala, V.

2004-01-01

The development of global magnetohydrodynamic (MHD) instabilities in Z-pinch plasmas has been studied with a three-dimensional hybrid simulation model. Plasma equilibria without and with axial sheared flow, and with different values of the parameter ε H , which appears as a coefficient before the Hall term in dimensionless nonideal MHD equations, have been considered. Increasing the parameter ε H leads to larger simulation growth rates for both m=0 sausage and m=1 kink modes. The hybrid simulations do however show that axial sheared flow severely curtails the linear and nonlinear development of both sausage and kink instabilities. In these respects, the hybrid simulations are in qualitative agreement with linear Hall MHD results. Moreover, in the nonlinear stage, long wavelength modes dominate the excited wave spectrum when the parameter ε H is small. For the larger value of the parameter ε H , small-scale structures do however develop nonlinearly in the excited wave spectrum at late times

On the Resolution of Inversion for Orthorhombic Anisotropy

KAUST Repository

Kazei, Vladimir

2017-05-26

We investigate the resolution of elastic anisotropic inversion for orthorhombic media with P-waves by remapping classic radiation patterns into the wavenumber domain. We show analytically that dynamic linearized inversion (linearized reverse-time migration and full-waveform inversion) for orthorhombic anisotropy based on longitudinal waves is fundamentally sensitive to emph{six} parameters only and density, in which the perturbing effects can be represented by particular anisotropy configuration. Singular value decomposition of spectral sensitivities allows us to provide estimates of the number of parameters one could invert in specific acquisition settings, and with certain parametrization. In most acquisition scenarios, a hierarchical parameterization based on the $P$, and $S$-wave velocities, along with dimensionless parameters that describe the anisotropy as velocity ratio in the radial and azimuthal directions, minimizes the tradeoff and increases the sensitivity of the data to velocity compared to the standard (stiffness, density) parametrization. These features yield more robust velocity estimation, by focusing the inversion on a subset of invertible parameters.

Equilibrium magnetization and microstructure of the system of superparamagnetic interacting particles: numerical simulation

International Nuclear Information System (INIS)

Pshenichnikov, A.F.; Mekhonoshin, V.V.

2000-01-01

The Monte Carlo method is used to study the equilibrium magnetization of a 3D system of superparamagnetic particles taking into account the steric and dipole-dipole interparticle interactions. Two types of systems are considered: magnetic fluids and solidified ferrocolloids containing randomly spatially distributed particles with negligible energy of magnetic anisotropy. The results of numerical simulations confirm the universality of Langevin susceptibility as a main dimensionless parameter determining the influence of interparticle interactions on the magnetization of the system for moderate values of the aggregation parameter. The obtained results are in good agreement with theoretical and experimental data. At large values of the aggregation parameter, the clustering of particles in magnetic fluids is observed resulting in a reduction of their magnetization as compared to solidified systems. It is shown that the magnetization of solidified systems can be well described by the modified effective field approximation within the whole investigated range of parameters

On the Resolution of Inversion for Orthorhombic Anisotropy

KAUST Repository

Kazei, Vladimir; Alkhalifah, Tariq Ali

2017-01-01

We investigate the resolution of elastic anisotropic inversion for orthorhombic media with P-waves by remapping classic radiation patterns into the wavenumber domain. We show analytically that dynamic linearized inversion (linearized reverse-time migration and full-waveform inversion) for orthorhombic anisotropy based on longitudinal waves is fundamentally sensitive to emph{six} parameters only and density, in which the perturbing effects can be represented by particular anisotropy configuration. Singular value decomposition of spectral sensitivities allows us to provide estimates of the number of parameters one could invert in specific acquisition settings, and with certain parametrization. In most acquisition scenarios, a hierarchical parameterization based on the $P$, and $S$-wave velocities, along with dimensionless parameters that describe the anisotropy as velocity ratio in the radial and azimuthal directions, minimizes the tradeoff and increases the sensitivity of the data to velocity compared to the standard (stiffness, density) parametrization. These features yield more robust velocity estimation, by focusing the inversion on a subset of invertible parameters.

Correlations among Stress Parameters, Meat and Carcass Quality Parameters in Pigs

Directory of Open Access Journals (Sweden)

Marija Dokmanovic

2015-03-01

Full Text Available Relationships among different stress parameters (lairage time and blood level of lactate and cortisol, meat quality parameters (initial and ultimate pH value, temperature, drip loss, sensory and instrumental colour, marbling and carcass quality parameters (degree of rigor mortis and skin damages, hot carcass weight, carcass fat thickness, meatiness were determined in pigs (n = 100 using Pearson correlations. After longer lairage, blood lactate (p<0.05 and degree of injuries (p<0.001 increased, meat became darker (p<0.001, while drip loss decreased (p<0.05. Higher lactate was associated with lower initial pH value (p<0.01, higher temperature (p<0.001 and skin blemishes score (p<0.05 and more developed rigor mortis (p<0.05, suggesting that lactate could be a predictor of both meat quality and the level of preslaughter stress. Cortisol affected carcass quality, so higher levels of cortisol were associated with increased hot carcass weight, carcass fat thickness on the back and at the sacrum and marbling, but also with decreased meatiness. The most important meat quality parameters (pH and temperature after 60 minutes deteriorated when blood lactate concentration was above 12 mmol/L.

Parameter identification of chaos system based on unknown parameter observer

International Nuclear Information System (INIS)

Wang Shaoming; Luo Haigeng; Yue Chaoyuan; Liao Xiaoxin

2008-01-01

Parameter identification of chaos system based on unknown parameter observer is discussed generally. Based on the work of Guan et al. [X.P. Guan, H.P. Peng, L.X. Li, et al., Acta Phys. Sinica 50 (2001) 26], the design of unknown parameter observer is improved. The application of the improved approach is extended greatly. The works in some literatures [X.P. Guan, H.P. Peng, L.X. Li, et al., Acta Phys. Sinica 50 (2001) 26; J.H. Lue, S.C. Zhang, Phys. Lett. A 286 (2001) 148; X.Q. Wu, J.A. Lu, Chaos Solitons Fractals 18 (2003) 721; J. Liu, S.H. Chen, J. Xie, Chaos Solitons Fractals 19 (2004) 533] are only the special cases of our Corollaries 1 and 2. Some observers for Lue system and a new chaos system are designed to test our improved method, and simulations results demonstrate the effectiveness and feasibility of the improved approach

Parameters of care for craniosynostosis

DEFF Research Database (Denmark)

McCarthy, Joseph G; Warren, Stephen M; Bernstein, Joseph

2012-01-01

A multidisciplinary meeting was held from March 4 to 6, 2010, in Atlanta, Georgia, entitled "Craniosynostosis: Developing Parameters for Diagnosis, Treatment, and Management." The goal of this meeting was to create parameters of care for individuals with craniosynostosis.......A multidisciplinary meeting was held from March 4 to 6, 2010, in Atlanta, Georgia, entitled "Craniosynostosis: Developing Parameters for Diagnosis, Treatment, and Management." The goal of this meeting was to create parameters of care for individuals with craniosynostosis....

Searching fundamental information in ordinary differential equations. Nondimensionalization technique.

Science.gov (United States)

Sánchez Pérez, J F; Conesa, M; Alhama, I; Alhama, F; Cánovas, M

2017-01-01

Classical dimensional analysis and nondimensionalization are assumed to be two similar approaches in the search for dimensionless groups. Both techniques, simplify the study of many problems. The first approach does not need to know the mathematical model, being sufficient a deep understanding of the physical phenomenon involved, while the second one begins with the governing equations and reduces them to their dimensionless form by simple mathematical manipulations. In this work, a formal protocol is proposed for applying the nondimensionalization process to ordinary differential equations, linear or not, leading to dimensionless normalized equations from which the resulting dimensionless groups have two inherent properties: In one hand, they are physically interpreted as balances between counteracting quantities in the problem, and on the other hand, they are of the order of magnitude unity. The solutions provided by nondimensionalization are more precise in every case than those from dimensional analysis, as it is illustrated by the applications studied in this work.

Robust estimation of hydrological model parameters

Directory of Open Access Journals (Sweden)

A. Bárdossy

2008-11-01

Full Text Available The estimation of hydrological model parameters is a challenging task. With increasing capacity of computational power several complex optimization algorithms have emerged, but none of the algorithms gives a unique and very best parameter vector. The parameters of fitted hydrological models depend upon the input data. The quality of input data cannot be assured as there may be measurement errors for both input and state variables. In this study a methodology has been developed to find a set of robust parameter vectors for a hydrological model. To see the effect of observational error on parameters, stochastically generated synthetic measurement errors were applied to observed discharge and temperature data. With this modified data, the model was calibrated and the effect of measurement errors on parameters was analysed. It was found that the measurement errors have a significant effect on the best performing parameter vector. The erroneous data led to very different optimal parameter vectors. To overcome this problem and to find a set of robust parameter vectors, a geometrical approach based on Tukey's half space depth was used. The depth of the set of N randomly generated parameters was calculated with respect to the set with the best model performance (Nash-Sutclife efficiency was used for this study for each parameter vector. Based on the depth of parameter vectors, one can find a set of robust parameter vectors. The results show that the parameters chosen according to the above criteria have low sensitivity and perform well when transfered to a different time period. The method is demonstrated on the upper Neckar catchment in Germany. The conceptual HBV model was used for this study.

Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

Science.gov (United States)

Butlitsky, M A; Zelener, B B; Zelener, B V

2014-07-14

A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1).

Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

Energy Technology Data Exchange (ETDEWEB)

Sun, G.F., E-mail: gfsun82@gmail.com [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); School of Mechanical Engineering, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Bhattacharya, S. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); Dinda, G.P.; Dasgupta, A. [Center for Advanced Technologies, Focus: Hope, Detroit, MI, 48238 (United States); Mazumder, J. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States)

2011-06-15

Highlights: {yields} Orientation relationships among phases in the DMD are given. {yields} Martensite lattice parameters increased with laser specific energy. {yields} Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

International Nuclear Information System (INIS)

Sun, G.F.; Bhattacharya, S.; Dinda, G.P.; Dasgupta, A.; Mazumder, J.

2011-01-01

Highlights: → Orientation relationships among phases in the DMD are given. → Martensite lattice parameters increased with laser specific energy. → Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

Summary of the DREAM8 Parameter Estimation Challenge: Toward Parameter Identification for Whole-Cell Models.

Directory of Open Access Journals (Sweden)

Jonathan R Karr

2015-05-01

Full Text Available Whole-cell models that explicitly represent all cellular components at the molecular level have the potential to predict phenotype from genotype. However, even for simple bacteria, whole-cell models will contain thousands of parameters, many of which are poorly characterized or unknown. New algorithms are needed to estimate these parameters and enable researchers to build increasingly comprehensive models. We organized the Dialogue for Reverse Engineering Assessments and Methods (DREAM 8 Whole-Cell Parameter Estimation Challenge to develop new parameter estimation algorithms for whole-cell models. We asked participants to identify a subset of parameters of a whole-cell model given the model's structure and in silico "experimental" data. Here we describe the challenge, the best performing methods, and new insights into the identifiability of whole-cell models. We also describe several valuable lessons we learned toward improving future challenges. Going forward, we believe that collaborative efforts supported by inexpensive cloud computing have the potential to solve whole-cell model parameter estimation.

Comparison of Parameter Identification Techniques

Directory of Open Access Journals (Sweden)

Eder Rafael

2016-01-01

Full Text Available Model-based control of mechatronic systems requires excellent knowledge about the physical behavior of each component. For several types of components of a system, e.g. mechanical or electrical ones, the dynamic behavior can be described by means of a mathematic model consisting of a set of differential equations, difference equations and/or algebraic constraint equations. The knowledge of a realistic mathematic model and its parameter values is essential to represent the behaviour of a mechatronic system. Frequently it is hard or impossible to obtain all required values of the model parameters from the producer, so an appropriate parameter estimation technique is required to compute missing parameters. A manifold of parameter identification techniques can be found in the literature, but their suitability depends on the mathematic model. Previous work dealt with the automatic assembly of mathematical models of serial and parallel robots with drives and controllers within the dynamic multibody simulation code HOTINT as fully-fledged mechatronic simulation. Several parameters of such robot models were identified successfully by our embedded algorithm. The present work proposes an improved version of the identification algorithm with higher performance. The quality of the identified parameter values and the computation effort are compared with another standard technique.

Charnock's Roughness Length Model and Non-dimensional Wind Profiles Over the Sea

DEFF Research Database (Denmark)

Pena Diaz, Alfredo; Gryning, Sven-Erik

2008-01-01

An analysis tool for the study of wind speed profiles over the water has been developed. The profiles are analysed using a modified dimensionless wind speed and dimensionless height, assuming that the sea surface roughness can be predicted by Charnock's roughness length model. In this form, the r...

Reduction of robot base parameters

International Nuclear Information System (INIS)

Vandanjon, P.O.

1995-01-01

This paper is a new step in the search of minimum dynamic parameters of robots. In spite of planing exciting trajectories and using base parameters, some parameters remain not identifiable due to the perturbation effects. In this paper, we propose methods to reduce the set of base parameters in order to get an essential set of parameters. This new set defines a simplified identification model witch improves the noise immunity of the estimation process. It contributes also in reducing the computation burden of a simplified dynamic model. Different methods are proposed and are classified in two parts: methods, witch perform reduction and identification together, come from statistical field and methods, witch reduces the model before the identification thanks to a priori information, come from numerical field like the QR factorization. Statistical tools and QR reduction are shown to be efficient and adapted to determine the essential parameters. They can be applied to open-loop, or graph structured rigid robot, as well as flexible-link robot. Application for the PUMA 560 robot is given. (authors). 9 refs., 4 tabs

Reduction of robot base parameters

Energy Technology Data Exchange (ETDEWEB)

Vandanjon, P O [CEA Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes et Systemes Avances; Gautier, M [Nantes Univ., 44 (France)

1996-12-31

This paper is a new step in the search of minimum dynamic parameters of robots. In spite of planing exciting trajectories and using base parameters, some parameters remain not identifiable due to the perturbation effects. In this paper, we propose methods to reduce the set of base parameters in order to get an essential set of parameters. This new set defines a simplified identification model witch improves the noise immunity of the estimation process. It contributes also in reducing the computation burden of a simplified dynamic model. Different methods are proposed and are classified in two parts: methods, witch perform reduction and identification together, come from statistical field and methods, witch reduces the model before the identification thanks to a priori information, come from numerical field like the QR factorization. Statistical tools and QR reduction are shown to be efficient and adapted to determine the essential parameters. They can be applied to open-loop, or graph structured rigid robot, as well as flexible-link robot. Application for the PUMA 560 robot is given. (authors). 9 refs., 4 tabs.

Applied parameter estimation for chemical engineers

CERN Document Server

Englezos, Peter

2000-01-01

Formulation of the parameter estimation problem; computation of parameters in linear models-linear regression; Gauss-Newton method for algebraic models; other nonlinear regression methods for algebraic models; Gauss-Newton method for ordinary differential equation (ODE) models; shortcut estimation methods for ODE models; practical guidelines for algorithm implementation; constrained parameter estimation; Gauss-Newton method for partial differential equation (PDE) models; statistical inferences; design of experiments; recursive parameter estimation; parameter estimation in nonlinear thermodynam

A Generic Approach to Parameter Control

NARCIS (Netherlands)

Karafotias, G.; Smit, S.K.; Eiben, A.E.

2012-01-01

On-line control of EA parameters is an approach to parameter setting that offers the advantage of values changing during the run. In this paper, we investigate parameter control from a generic and parameter-independent perspective. We propose a generic control mechanism that is targeted to

Approaches to automatic parameter fitting in a microscopy image segmentation pipeline: An exploratory parameter space analysis.

Science.gov (United States)

Held, Christian; Nattkemper, Tim; Palmisano, Ralf; Wittenberg, Thomas

2013-01-01

Research and diagnosis in medicine and biology often require the assessment of a large amount of microscopy image data. Although on the one hand, digital pathology and new bioimaging technologies find their way into clinical practice and pharmaceutical research, some general methodological issues in automated image analysis are still open. In this study, we address the problem of fitting the parameters in a microscopy image segmentation pipeline. We propose to fit the parameters of the pipeline's modules with optimization algorithms, such as, genetic algorithms or coordinate descents, and show how visual exploration of the parameter space can help to identify sub-optimal parameter settings that need to be avoided. This is of significant help in the design of our automatic parameter fitting framework, which enables us to tune the pipeline for large sets of micrographs. The underlying parameter spaces pose a challenge for manual as well as automated parameter optimization, as the parameter spaces can show several local performance maxima. Hence, optimization strategies that are not able to jump out of local performance maxima, like the hill climbing algorithm, often result in a local maximum.

Approaches to automatic parameter fitting in a microscopy image segmentation pipeline: An exploratory parameter space analysis

Directory of Open Access Journals (Sweden)

Christian Held

2013-01-01

Full Text Available Introduction: Research and diagnosis in medicine and biology often require the assessment of a large amount of microscopy image data. Although on the one hand, digital pathology and new bioimaging technologies find their way into clinical practice and pharmaceutical research, some general methodological issues in automated image analysis are still open. Methods: In this study, we address the problem of fitting the parameters in a microscopy image segmentation pipeline. We propose to fit the parameters of the pipeline′s modules with optimization algorithms, such as, genetic algorithms or coordinate descents, and show how visual exploration of the parameter space can help to identify sub-optimal parameter settings that need to be avoided. Results: This is of significant help in the design of our automatic parameter fitting framework, which enables us to tune the pipeline for large sets of micrographs. Conclusion: The underlying parameter spaces pose a challenge for manual as well as automated parameter optimization, as the parameter spaces can show several local performance maxima. Hence, optimization strategies that are not able to jump out of local performance maxima, like the hill climbing algorithm, often result in a local maximum.

The parameter spreadsheets and their applications

International Nuclear Information System (INIS)

Schwitters, R.; Chao, A.; Chou, W.; Peterson, J.

1993-01-01

This paper is to announce that a set of parameter spreadsheets, using the Microsoft EXCEL software, has been developed for the SSC (and also for the LHC). In this program, the input (or control) parameters and the derived parameters are linked by equations that express the accelerator physics involved. A subgroup of parameters that are considered critical, or possible bottlenecks, has been highlighted under the category of open-quotes Flagsclose quotes. Given certain performance goals, one can use this program to open-quotes tuneclose quotes the input parameters in such a way that the flagged parameters do not exceed their acceptable range. During the past years, this program has been employed for the following purposes: (a) To guide the machine designs for various operation scenarios, (b) To generate a parameter list that is self-consistent and, (c) To study the impact of some proposed parameter changes (e.g., different choices of the rf frequency and bunch spacing)

Equilibrium magnetization and microstructure of the system of superparamagnetic interacting particles: numerical simulation

CERN Document Server

Pshenichnikov, A F

2000-01-01

The Monte Carlo method is used to study the equilibrium magnetization of a 3D system of superparamagnetic particles taking into account the steric and dipole-dipole interparticle interactions. Two types of systems are considered: magnetic fluids and solidified ferrocolloids containing randomly spatially distributed particles with negligible energy of magnetic anisotropy. The results of numerical simulations confirm the universality of Langevin susceptibility as a main dimensionless parameter determining the influence of interparticle interactions on the magnetization of the system for moderate values of the aggregation parameter. The obtained results are in good agreement with theoretical and experimental data. At large values of the aggregation parameter, the clustering of particles in magnetic fluids is observed resulting in a reduction of their magnetization as compared to solidified systems. It is shown that the magnetization of solidified systems can be well described by the modified effective field appr...

MHD effects and heat transfer for the UCM fluid along with Joule heating and thermal radiation using Cattaneo-Christov heat flux model

Energy Technology Data Exchange (ETDEWEB)

Shah, S., E-mail: sajidshah313@yahoo.com; Hussain, S.; Sagheer, M. [Department of Mathematics, Capital University of Science and Technology, Islamabad (Pakistan)

2016-08-15

Present study examines the numerical analysis of MHD flow of Maxwell fluid with thermal radiation and Joule heating by considering the recently developed Cattaneo-Christov heat flux model which explains the time relaxation characteristics for the heat flux. The objective is to analyze the governing parameters such as viscoelastic fluid parameter, Magnetic parameter, Eckert and Prandtl number’s impact on the velocity and temperature profiles through graphs and tables. Suitable similarity transformations have been used to reduce the formulated PDEs into a system of coupled non-linear ODEs. Shooting technique has been invoked for finding the numerical solutions of the dimensionless velocity and temperature profiles. Additionally, the MATLAB built-in routine bvp4c has also been used to verify and strengthen the results obtained by shooting method. From some special cases of the present work, a comparison with the previously published results has been presented.

Phase space analysis for anisotropic universe with nonlinear bulk viscosity

Science.gov (United States)

Sharif, M.; Mumtaz, Saadia

2018-06-01

In this paper, we discuss phase space analysis of locally rotationally symmetric Bianchi type I universe model by taking a noninteracting mixture of dust like and viscous radiation like fluid whose viscous pressure satisfies a nonlinear version of the Israel-Stewart transport equation. An autonomous system of equations is established by defining normalized dimensionless variables. In order to investigate stability of the system, we evaluate corresponding critical points for different values of the parameters. We also compute power-law scale factor whose behavior indicates different phases of the universe model. It is found that our analysis does not provide a complete immune from fine-tuning because the exponentially expanding solution occurs only for a particular range of parameters. We conclude that stable solutions exist in the presence of nonlinear model for bulk viscosity with different choices of the constant parameter m for anisotropic universe.

Identifyability measures to select the parameters to be estimated in a solid-state fermentation distributed parameter model.

Science.gov (United States)

da Silveira, Christian L; Mazutti, Marcio A; Salau, Nina P G

2016-07-08

Process modeling can lead to of advantages such as helping in process control, reducing process costs and product quality improvement. This work proposes a solid-state fermentation distributed parameter model composed by seven differential equations with seventeen parameters to represent the process. Also, parameters estimation with a parameters identifyability analysis (PIA) is performed to build an accurate model with optimum parameters. Statistical tests were made to verify the model accuracy with the estimated parameters considering different assumptions. The results have shown that the model assuming substrate inhibition better represents the process. It was also shown that eight from the seventeen original model parameters were nonidentifiable and better results were obtained with the removal of these parameters from the estimation procedure. Therefore, PIA can be useful to estimation procedure, since it may reduce the number of parameters that can be evaluated. Further, PIA improved the model results, showing to be an important procedure to be taken. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:905-917, 2016. © 2016 American Institute of Chemical Engineers.

Selection and verification of safety parameters in safety parameter display system for nuclear power plants

International Nuclear Information System (INIS)

Zhang Yuangfang

1992-02-01

The method and results for safety parameter selection and its verification in safety parameter display system of nuclear power plants are introduced. According to safety analysis, the overall safety is divided into six critical safety functions, and a certain amount of safety parameters which can represent the integrity degree of each function and the causes of change are strictly selected. The verification of safety parameter selection is carried out from the view of applying the plant emergency procedures and in the accident man oeuvres on a full scale nuclear power plant simulator

GPS User Devices Parameter Control Methods

OpenAIRE

Klūga, A; Kuļikovs, M; Beļinska, V; Zeļenkovs, A

2007-01-01

In our day’s wide assortment of GPS user devices is manufacture. How to verify that parameters of the real device corresponds to parameters that manufacture shows. How to verify that parameters have not been changed during the operation time. The last one is very important for aviation GPS systems, which must be verified before the flight, but the values of parameter in time of repair works. This work analyses GPS user devices parameters control methods.

Systematic of delayed neutron parameters

International Nuclear Information System (INIS)

Isaev, S.G.; Piksaikin, V.M.

2000-01-01

The experimental studies of the energy dependence of the delayed neutron (DN) parameters for various fission systems has shown that the behaviour of a some combination of delayed neutron parameters has a similar features. On the basis of this findings the systematics of delayed neutron experimental data for thorium, uranium, plutonium and americium isotopes have been investigated with the purpose to find a correlation of DN parameters with characteristics of fissioning system as well as a correlation between the delayed neutron parameters themselves. It was presented the preliminary results which were obtained during study the physics interpretation of the results [ru

On the Consistency of Bootstrap Testing for a Parameter on the Boundary of the Parameter Space

DEFF Research Database (Denmark)

Cavaliere, Giuseppe; Nielsen, Heino Bohn; Rahbek, Anders

2017-01-01

It is well known that with a parameter on the boundary of the parameter space, such as in the classic cases of testing for a zero location parameter or no autoregressive conditional heteroskedasticity (ARCH) effects, the classic nonparametric bootstrap – based on unrestricted parameter estimates...... – leads to inconsistent testing. In contrast, we show here that for the two aforementioned cases, a nonparametric bootstrap test based on parameter estimates obtained under the null – referred to as ‘restricted bootstrap’ – is indeed consistent. While the restricted bootstrap is simple to implement...... in practice, novel theoretical arguments are required in order to establish consistency. In particular, since the bootstrap is analysed both under the null hypothesis and under the alternative, non-standard asymptotic expansions are required to deal with parameters on the boundary. Detailed proofs...

Angular circulation speed of tablets in a vibratory tablet coating pan.

Science.gov (United States)

Kumar, Rahul; Wassgren, Carl

2013-03-01

In this work, a single tablet model and a discrete element method (DEM) computer simulation are developed to obtain the angular circulation speed of tablets in a vibratory tablet coating pan for range of vibration frequencies and amplitudes. The models identify three important dimensionless parameters that influence the speed of the tablets: the dimensionless amplitude ratio (a/R), the Froude number (aω2/g), and the tablet-wall friction coefficient, where a is the peak vibration amplitude at the drum center, ω is the vibration angular frequency, R is the drum radius, and g is the acceleration due to gravity. The models predict that the angular circulation speed of tablets increases with an increase in each of these parameters. The rate of increase in the angular circulation speed is observed to decrease for larger values of a/R. The angular circulation speed reaches an asymptote beyond a tablet-wall friction coefficient value of about 0.4. Furthermore, it is found that the Froude number should be greater than one for the tablets to start circulating. The angular circulation speed increases as Froude number increases but then does not change significantly at larger values of the Froude number. Period doubling, where the motion of the bed is repeated every two cycles, occurs at a Froude number larger than five. The single tablet model, although much simpler than the DEM model, is able to predict the maximum circulation speed (the limiting case for a large value of tablet-wall friction coefficient) as well as the transition to period doubling.

HIGH-ENERGY COSMIC-RAY DIFFUSION IN MOLECULAR CLOUDS: A NUMERICAL APPROACH

International Nuclear Information System (INIS)

Fatuzzo, M.; Melia, F.; Todd, E.; Adams, F. C.

2010-01-01

The propagation of high-energy cosmic rays (CRs) through giant molecular clouds constitutes a fundamental process in astronomy and astrophysics. The diffusion of CRs through these magnetically turbulent environments is often studied through the use of energy-dependent diffusion coefficients, although these are not always well motivated theoretically. Now, however, it is feasible to perform detailed numerical simulations of the diffusion process computationally. While the general problem depends upon both the field structure and particle energy, the analysis may be greatly simplified by dimensionless analysis. That is, for a specified purely turbulent field, the analysis depends almost exclusively on a single parameter-the ratio of the maximum wavelength of the turbulent field cells to the particle gyration radius. For turbulent magnetic fluctuations superimposed over an underlying uniform magnetic field, particle diffusion depends on a second dimensionless parameter that characterizes the ratio of the turbulent to uniform magnetic field energy densities. We consider both of these possibilities and parametrize our results to provide simple quantitative expressions that suitably characterize the diffusion process within molecular cloud environments. Doing so, we find that the simple scaling laws often invoked by the high-energy astrophysics community to model CR diffusion through such regions appear to be fairly robust for the case of a uniform magnetic field with a strong turbulent component, but are only valid up to ∼50 TeV particle energies for a purely turbulent field. These results have important consequences for the analysis of CR processes based on TeV emission spectra associated with dense molecular clouds.

Comparison of experimental data with results of some drying models for regularly shaped products

Science.gov (United States)

Kaya, Ahmet; Aydın, Orhan; Dincer, Ibrahim

2010-05-01

This paper presents an experimental and theoretical investigation of drying of moist slab, cylinder and spherical products to study dimensionless moisture content distributions and their comparisons. Experimental study includes the measurement of the moisture content distributions of slab and cylindrical carrot, slab and cylindrical pumpkin and spherical blueberry during drying at various temperatures (e.g., 30, 40, 50 and 60°C) at specific constant velocity ( U = 1 m/s) and the relative humidity φ = 30%. In theoretical analysis, two moisture transfer models are used to determine drying process parameters (e.g., drying coefficient and lag factor) and moisture transfer parameters (e.g., moisture diffusivity and moisture transfer coefficient), and to calculate the dimensionless moisture content distributions. The calculated results are then compared with the experimental moisture data. A considerably high agreement is obtained between the calculations and experimental measurements for the cases considered. The effective diffusivity values were evaluated between 0.741 × 10-5 and 5.981 × 10-5 m2/h for slab products, 0.818 × 10-5 and 6.287 × 10-5 m2/h for cylindrical products and 1.213 × 10-7 and 7.589 × 10-7 m2/h spherical products using the Model-I and 0.316 × 10-5-5.072 × 10-5 m2/h for slab products, 0.580 × 10-5-9.587 × 10-5 m2/h for cylindrical products and 1.408 × 10-7-13.913 × 10-7 m2/h spherical products using the Model-II.

Numerical Calculation of the Peaking Factor of a Water-Cooled W/Cu Monoblock for a Divertor

International Nuclear Information System (INIS)

Han Le; Chang Haiping; Zhang Jingyang; Xu Tiejun

2015-01-01

In order to accurately predict the incident critical heat flux (ICHF, the heat flux at the heated surface when CHF occurs) of a water-cooled W/Cu monoblock for a divertor, the exact knowledge of its peaking factors (f p ) under one-sided heating conditions with different design parameters is a key issue. In this paper, the heat conduction in the solid domain of a water-cooled W/Cu monoblock is calculated numerically by assuming the local heat transfer coefficients (HTC) of the cooling wall to be functions of the local wall temperature, so as to obtain f p . The reliability of the calculation method is validated by an experimental example result, with the maximum error of 2.1% only. The effects of geometric and flow parameters on the f p of a water-cooled W/Cu monoblock are investigated. Within the scope of this study, it is shown that the f p increases with increasing dimensionless W/Cu monoblock width and armour thickness (the shortest distance between the heated surface and Cu layer), and the maximum increases are 43.8% and 22.4% respectively. The dimensionless W/Cu monoblock height and Cu thickness have little effect on f p . The increase of Reynolds number and Jakob number causes the increase of f p , and the maximum increases are 6.8% and 9.6% respectively. Based on the calculated results, an empirical correlation on peaking factor is obtained via regression. These results provide a valuable reference for the thermal-hydraulic design of water-cooled divertors. (paper)

Numerical analysis of a heat-generating, truncated conical porous bed in a fluid-filled enclosure

International Nuclear Information System (INIS)

Chakravarty, Aranyak; Datta, Priyankan; Ghosh, Koushik; Sen, Swarnendu; Mukhopadhyay, Achintya

2016-01-01

Analysis of natural convection in enclosures containing heat generating porous medium has important applications related to geothermal, chemical, thermal and nuclear energy such as in-vessel cooling of debris beds in nuclear reactors, cooling of coal stockpiles etc. The objective of the present numerical study is to characterise the pattern of fluid flow and energy transfer during steady laminar natural convective flow in a cylindrical enclosure with a centrally placed heat generating porous bed. Flow through porous region is modelled using Darcy–Brinkmann–Forchheimer model and local thermal equilibrium is assumed for the porous region. Analysis is carried out for a wide range of Rayleigh number (Ra), Darcy number (Da) and thermal conductivity ratio, as well as for different bed geometries. It is observed that in addition to Ra and Da, the bed geometry also plays a very important role in determining flow field and temperature distribution within the enclosure. Interestingly, a significant change is observed in energy transfer mode from the porous bed corresponding to specific values of bed permeability and bed heat generation rate. This is characterised in terms of Ra and Da. Further, it is observed that this change in energy transfer mode is highly dependent on Ra. - Highlights: • Natural convection is analysed in an enclosure with a heat generating porous bed. • Effect of dimensionless parameters as well as bed geometry has been investigated. • Energy transfer mechanism from porous bed changes with dimensionless parameters. • Bed geometry significantly affects fluid flow and energy transfer in the enclosure.

Inflation and cosmological parameter estimation

Energy Technology Data Exchange (ETDEWEB)

Hamann, J.

2007-05-15

In this work, we focus on two aspects of cosmological data analysis: inference of parameter values and the search for new effects in the inflationary sector. Constraints on cosmological parameters are commonly derived under the assumption of a minimal model. We point out that this procedure systematically underestimates errors and possibly biases estimates, due to overly restrictive assumptions. In a more conservative approach, we analyse cosmological data using a more general eleven-parameter model. We find that regions of the parameter space that were previously thought ruled out are still compatible with the data; the bounds on individual parameters are relaxed by up to a factor of two, compared to the results for the minimal six-parameter model. Moreover, we analyse a class of inflation models, in which the slow roll conditions are briefly violated, due to a step in the potential. We show that the presence of a step generically leads to an oscillating spectrum and perform a fit to CMB and galaxy clustering data. We do not find conclusive evidence for a step in the potential and derive strong bounds on quantities that parameterise the step. (orig.)

EFFECT OF HYDRAULIC AND GEOMETRICAL PROPERTIES ON STEPPED CASCADE AERATION SYSTEM

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VEDHACHALAM RATHINAKUMAR

2017-03-01

Full Text Available Stepped cascade aeration system is commonly used to aerate the water and wastewater to increase the dissolved oxygen during pre and post treatment process. In the present research, experiments were conducted to evaluate the performance of a rectangular Cascade Aeration System with varying flow rates, risers and tread by maintaining constant width of the channel using water collected from reverse osmosis plant. The experiments were carried out with four different risers such as 0.15 m, 0.18 m, 0.225 m and 0.30 m. Each rise was investigated with five different tread of 0.60 m, 0.55 m, 0.50 m, 0.45 m and 0.40 m. Comprehensive experimental investigations were carried out for different hydraulic loading rates of 0.005 to 0.035 m3/s/m2. Results obtained from the experiments reveals that increasing dimensionless discharges promotes more aeration, attains a maximum up to dimensionless discharge= 2.22 and beyond this there was a significant decrease in aeration. In addition, the increased in number of steps significantly enhances air entertainment and surface fall rate in the Stepped Cascade Aeration System. A regression equation was derived by keeping aeration efficiency as response with dimensionless discharge and oxygen saturation concentration as influencing parameters. The dimension less discharge is a function of critical depth of the rectangular channel and step height, whereas oxygen saturation concentration represents the ratio of oxygen deficit and oxygen saturation concentration. Based on the experimental results, the optimum design and/or results such as number of steps (12 numbers and hydraulic loading rate (0.025 m3/s/m2 with fixed tread width of 0.6 m were identified to achieve maximum aeration rate (0.5-0.60 in Aeration system.

PECULIARITIES OF GENERALIZATION OF SIMILAR PHENOMENA IN THE PROCESS OF FISH HEAT TREATMENT

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V. A. Pokhol’chenko

2015-01-01

Full Text Available The theoretical presuppositions for the possibility of generalizing and similarity founding in dehydration and wet materials heating processes are studieded in this article. It is offered to carry out the given processes generalization by using dimensionless numbers of similarity. At the detailed analyzing of regularities of heat treatment processes of fish in different modes a significant amount of experienced material was successfully generalized on the basis of dimensionless simplex (similarity numbers. Using the dimensionless simplex allowed to detect a number of simple mathematical models for the studied phenomena. The generalized kinetic models of fish dehydration, the generalized dynamic models (changing moisture diffusion coefficients, the generalized kinetic models of fish heating (the temperature field changing in the products thickness, average volume and center were founded. These generalized mathematical models showed also relationship of dehydration and heating at the processes of fish semi-hot, hot smoking (drying and frying. The relationship of the results from the physical nature of the dehydration process, including a change in the binding energy of the moisture with the material to the extent of the process and the shrinkage impact on the rate of the product moisture removal is given in the article. The factors influencing the internal structure and properties of the raw material changing and retarding the dehydration processes are described there. There was a heating rate dependence of fish products on the chemical composition the geometric dimensions of the object of heating and on the coolant regime parameters. A unique opportunity is opened by using the generalized models, combined with empirically derived equations and the technique of engineering calculation of these processes, to design a rational modes of heat treatment of raw materials and to optimize the performance of thermal equipment.

Reduced-order model for inertial locomotion of a slender swimmer

Science.gov (United States)

Mahalinkam, Raksha; Gong, Felicity; Khair, Aditya S.

2018-04-01

The inertial locomotion of an elongated model swimmer in a Newtonian fluid is quantified, wherein self-propulsion is achieved via steady tangential surface treadmilling. The swimmer has a length 2 l and a circular cross section of longitudinal profile a R (z ) , where a is the characteristic width of the cross section, R (z ) is a dimensionless shape function, and z is a dimensionless coordinate, normalized by l , along the centerline of the body. It is assumed that the swimmer is slender, ɛ =a /l ≪1 . Hence, we utilize slender-body theory to analyze the Navier-Stokes equations that describe the flow around the swimmer. Therefrom, we compute an asymptotic approximation to the swimming speed, U , as U /us=1 -β [V (Re ) -1/2 ∫-11z lnR (z ) d z ] /ln(1 /ɛ ) +O [1 /ln2(1 /ɛ ) ], where us is the characteristic speed of the surface treadmilling, Re is the Reynolds number based on the body length, and β is a dimensionless parameter that differentiates between "pusher" (propelled from the rear, β 0 ) -type swimmers. The function V (Re ) increases monotonically with increasing Re ; hence, fluid inertia causes an increase (decrease) in the swimming speed of a pusher (puller). Next, we demonstrate that the power expenditure of the swimmer increases monotonically with increasing Re . Further, the power expenditures of a puller and pusher with the same value of |β | are equal. Therefore, pushers are superior in inertial locomotion as compared to pullers, in that they achieve a faster swimming speed for the same power expended. Finally, it is demonstrated that the flow structure predicted from our reduced-order model is consistent with that from direct numerical simulation of swimmers at intermediate Re .

Single-Fiber Reflectance Spectroscopy of Isotropic-Scattering Medium: An Analytic Perspective to the Ratio-of-Remission in Steady-State Measurements

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Daqing Piao

2014-12-01

Full Text Available Recent focused Monte Carlo and experimental studies on steady-state single-fiber reflectance spectroscopy (SfRS from a biologically relevant scattering medium have revealed that, as the dimensionless reduced scattering of the medium increases, the SfRS intensity increases monotonically until reaching a plateau. The SfRS signal is semi-empirically decomposed to the product of three contributing factors, including a ratio-of-remission (RoR term that refers to the ratio of photons remitting from the medium and crossing the fiber-medium interface over the total number of photons launched into the medium. The RoR is expressed with respect to the dimensionless reduced scattering parameter , where  is the reduced scattering coefficient of the medium and  is the diameter of the probing fiber. We develop in this work, under the assumption of an isotropic-scattering medium, a method of analytical treatment that will indicate the pattern of RoR as a function of the dimensionless reduced scattering of the medium. The RoR is derived in four cases, corresponding to in-medium (applied to interstitial probing of biological tissue or surface-based (applied to contact-probing of biological tissue SfRS measurements using straight-polished or angle-polished fiber. The analytically arrived surface-probing RoR corresponding to single-fiber probing using a 15° angle-polished fiber over the range of  agrees with previously reported similarly configured experimental measurement from a scattering medium that has a Henyey–Greenstein scattering phase function with an anisotropy factor of 0.8. In cases of a medium scattering light anisotropically, we propose how the treatment may be furthered to account for the scattering anisotropy using the result of a study of light scattering close to the point-of-entry by Vitkin et al. (Nat. Commun. 2011, doi:10.1038/ncomms1599.

Are calanco landforms similar to river basins?

Science.gov (United States)

Caraballo-Arias, N A; Ferro, V

2017-12-15

In the past badlands have been often considered as ideal field laboratories for studying landscape evolution because of their geometrical similarity to larger fluvial systems. For a given hydrological process, no scientific proof exists that badlands can be considered a model of river basin prototypes. In this paper the measurements carried out on 45 Sicilian calanchi, a type of badlands that appears as a small-scale hydrographic unit, are used to establish their morphological similarity with river systems whose data are available in the literature. At first the geomorphological similarity is studied by identifying the dimensionless groups, which can assume the same value or a scaled one in a fixed ratio, representing drainage basin shape, stream network and relief properties. Then, for each property, the dimensionless groups are calculated for the investigated calanchi and the river basins and their corresponding scale ratio is evaluated. The applicability of Hack's, Horton's and Melton's laws for establishing similarity criteria is also tested. The developed analysis allows to conclude that a quantitative morphological similarity between calanco landforms and river basins can be established using commonly applied dimensionless groups. In particular, the analysis showed that i) calanchi and river basins have a geometrically similar shape respect to the parameters Rf and Re with a scale factor close to 1, ii) calanchi and river basins are similar respect to the bifurcation and length ratios (λ=1), iii) for the investigated calanchi the Melton number assumes values less than that (0.694) corresponding to the river case and a scale ratio ranging from 0.52 and 0.78 can be used, iv) calanchi and river basins have similar mean relief ratio values (λ=1.13) and v) calanchi present active geomorphic processes and therefore fall in a more juvenile stage with respect to river basins. Copyright © 2017 Elsevier B.V. All rights reserved.

Parameter transferability within homogeneous regions and comparisons with predictions from a priori parameters in the eastern United States

Science.gov (United States)

Chouaib, Wafa; Alila, Younes; Caldwell, Peter V.

2018-05-01

The need for predictions of flow time-series persists at ungauged catchments, motivating the research goals of our study. By means of the Sacramento model, this paper explores the use of parameter transfer within homogeneous regions of similar climate and flow characteristics and makes comparisons with predictions from a priori parameters. We assessed the performance using the Nash-Sutcliffe (NS), bias, mean monthly hydrograph and flow duration curve (FDC). The study was conducted on a large dataset of 73 catchments within the eastern US. Two approaches to the parameter transferability were developed and evaluated; (i) the within homogeneous region parameter transfer using one donor catchment specific to each region, (ii) the parameter transfer disregarding the geographical limits of homogeneous regions, where one donor catchment was common to all regions. Comparisons between both parameter transfers enabled to assess the gain in performance from the parameter regionalization and its respective constraints and limitations. The parameter transfer within homogeneous regions outperformed the a priori parameters and led to a decrease in bias and increase in efficiency reaching a median NS of 0.77 and a NS of 0.85 at individual catchments. The use of FDC revealed the effect of bias on the inaccuracy of prediction from parameter transfer. In one specific region, of mountainous and forested catchments, the prediction accuracy of the parameter transfer was less satisfactory and equivalent to a priori parameters. In this region, the parameter transfer from the outsider catchment provided the best performance; less-biased with smaller uncertainty in medium flow percentiles (40%-60%). The large disparity of energy conditions explained the lack of performance from parameter transfer in this region. Besides, the subsurface stormflow is predominant and there is a likelihood of lateral preferential flow, which according to its specific properties further explained the reduced

Multi-Objective Parameter Selection for Classifers

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Christoph Mussel

2012-01-01

Full Text Available Setting the free parameters of classifiers to different values can have a profound impact on their performance. For some methods, specialized tuning algorithms have been developed. These approaches mostly tune parameters according to a single criterion, such as the cross-validation error. However, it is sometimes desirable to obtain parameter values that optimize several concurrent - often conflicting - criteria. The TunePareto package provides a general and highly customizable framework to select optimal parameters for classifiers according to multiple objectives. Several strategies for sampling andoptimizing parameters are supplied. The algorithm determines a set of Pareto-optimal parameter configuration and leaves the ultimate decision on the weighting of objectives to the researcher. Decision support is provided by novel visualization techniques.

Voltage stability, bifurcation parameters and continuation methods

Energy Technology Data Exchange (ETDEWEB)

Alvarado, F L [Wisconsin Univ., Madison, WI (United States)

1994-12-31

This paper considers the importance of the choice of bifurcation parameter in the determination of the voltage stability limit and the maximum power load ability of a system. When the bifurcation parameter is power demand, the two limits are equivalent. However, when other types of load models and bifurcation parameters are considered, the two concepts differ. The continuation method is considered as a method for determination of voltage stability margins. Three variants of the continuation method are described: the continuation parameter is the bifurcation parameter the continuation parameter is initially the bifurcation parameter, but is free to change, and the continuation parameter is a new `arc length` parameter. Implementations of voltage stability software using continuation methods are described. (author) 23 refs., 9 figs.

Study on natural convection characteristics in a narrow annular gap, 2

International Nuclear Information System (INIS)

Naohara, Nobuyuki; Uotani, Masaki; Kinoshita, Izumi; Arazeki, Hideo

1987-01-01

To clarify the characteristics of natural convection in a narrow annular gap at the roof-slab penetration in pool-type LMFBR, experimental study was carried out. Experiment is to investigate the effect of annular gap width. The results are summarized as follows. (1) A chart showing the presence of natural convection was drawn, and it was showed that the natural convection in an annular gap was influenced by gap width. (2) Dimensionless circumferential temperature in annular wall could be rearranged by new parameter taking account of the annular gap width and a characteristics curve was obtained. (author)

Kinetic synergistic transitions in the Ostwald ripening processes

Science.gov (United States)

Sachkov, I. N.; Turygina, V. F.; Dolganov, A. N.

2018-01-01

There is proposed approach to mathematical description of the kinetic transitions in Ostwald ripening processes of volatile substance in nonuniformly heated porous materials. It is based upon the finite element method. There are implemented computer software. The main feature of the software is to calculate evaporation and condensation fluxes on the walls of a nonuniformly heated cylindrical capillary. Kinetic transitions are detected for three modes of volatile substances migration which are different by condensation zones location. There are controlling dimensionless parameters of the kinetic transition which are revealed during research. There is phase diagram of the Ostwald ripening process modes realization.

Inflation and reheating in induced-gravity models

International Nuclear Information System (INIS)

Barr, S.; Segre, G.

1990-01-01

The Planck mass is generated dynamically in induced-gravity models, typically being related to the vacuum expectation value of a scalar field φ, ε 1/2 left-angle φ right-angle=M Pl / √8π , where ε is a dimensionless parameter, typically smaller than one. We discuss in this paper the decay of the φ particle, which is mainly into gravitons, and the consequences this has for models in which the φ field is responsible for inflation. We show in particular that too much energy is stored in φ oscillations and adequate reheating does not occur

Quantum versus classical dynamics in the optical centrifuge

Science.gov (United States)

Armon, Tsafrir; Friedland, Lazar

2017-09-01

The interplay between classical and quantum-mechanical evolution in the optical centrifuge (OC) is discussed. The analysis is based on the quantum-mechanical formalism starting from either the ground state or a thermal ensemble. Two resonant mechanisms are identified, i.e., the classical autoresonance and the quantum-mechanical ladder climbing, yielding different dynamics and rotational excitation efficiencies. The rotating-wave approximation is used to analyze the two resonant regimes in the associated dimensionless two-parameter space and calculate the OC excitation efficiency. The results show good agreement between numerical simulations and theory and are relevant to existing experimental setups.

Physical Processes Controlling Earth's Climate

Science.gov (United States)

Genio, Anthony Del

2013-01-01

As background for consideration of the climates of the other terrestrial planets in our solar system and the potential habitability of rocky exoplanets, we discuss the basic physics that controls the Earths present climate, with particular emphasis on the energy and water cycles. We define several dimensionless parameters relevant to characterizing a planets general circulation, climate and hydrological cycle. We also consider issues associated with the use of past climate variations as indicators of future anthropogenically forced climate change, and recent advances in understanding projections of future climate that might have implications for Earth-like exoplanets.

A simplified analysis for cold storage in porous capsules with solidification

International Nuclear Information System (INIS)

Chen, S.L.; Yue, J.S.

1991-01-01

This paper investigates the thermal performance of a cold storage system utilizing water porous capsules as phase change material. The proposed cold storage system can be used to shift electric demand from periods of high demand to ones of low demand. A simple lump model to determine the thermal characteristics has been developed. The solution of the system equations is found through the Laplace transformation method. Experimental data of temperature profiles obtained in this study for various porosities, coolant flow rates, and inlet coolant temperatures validate the theory. Effects of dimensionless parameters on the charge characteristics were found

Free convection heat and mass transfer in a power law fluid past an inclined surface with thermophoresis

Directory of Open Access Journals (Sweden)

Medhat M. Helal

2013-10-01

Full Text Available The problem of heat and mass transfer in a power law, two-dimensional, laminar, boundary layer flow of a viscous incompressible fluid over an inclined plate with heat generation and thermophoresis is investigated by the characteristic function method. The governing non-linear partial differential equations describing the flow and heat transfer problem are transformed into a set of coupled non-linear ordinary differential equation which was solved using Runge–Kutta shooting method. Exact solutions for the dimensionless temperature and concentration profiles, are presented graphically for different physical parameters and for the different power law exponents 0  0.5.

Magnetohydrodynamic Three-Dimensional Flowof a Second-Grade Fluid with Heat Transfer

Science.gov (United States)

Hayat, Tasawar; Nawaz, Muhammad

2010-09-01

An analysis has been carried out for the heat transfer on steady boundary layer flow of a secondgrade fluid bounded by a stretching sheet. The magnetohydrodynamic nature of the fluid is considered in the presence of Hall and ion-slip currents. The nonlinear mathematical problem is computed by a powerful tool, namely, the homotopy analysis method (HAM). A comparative study between the present and existing limiting results is carefully made. Convergence regarding the obtained solution is discussed. Skin friction coefficients and Nusselt number are analyzed. Effects of embedded parameters on the dimensionless velocities and temperature are examined

Correlation to predict heat transfer of an oscillating loop heat pipe consisting of three interconnected columns

International Nuclear Information System (INIS)

Arslan, Goekhan; Ozdemir, Mustafa

2008-01-01

In this paper, heat transfer in an oscillating loop heat pipe is investigated experimentally. The oscillation of the liquid columns at the evaporator and condenser sections of the heat pipe are driven by gravitational force and the phase lag between evaporation and condensation because the dimensions of the heat pipe are large enough to neglect the effect of capillary forces. The overall heat transfer coefficient based on the temperature difference between the evaporator and condenser surfaces is introduced by a correlation function of dimensionless numbers such as kinetic Reynolds number, c p ΔT/h fg and the geometric parameters

Parametric numerical investigaion of natural convection in a heat-generating fluid with phase transitions

Energy Technology Data Exchange (ETDEWEB)

Aksenova, A.E.; Chudanov, V.V.; Strizhov, V.F.; Vabishchevich, P.N. [Institute of Nuclear Safety Russian Academy Science, Moscow (Russian Federation)

1995-09-01

Unsteady natural convection of a heat-generating fluid with phase transitions in the enclosures of a square section with isothermal rigid walls is investigated numerically for a wide range of dimensionless parameters. The quasisteady state solutions of conjugate heat and mass transfer problem are compared with available experimental results. Correlation relations for heat flux distributions at the domain boundaries depending on Rayleigh and Ostrogradskii numbers are obtained. It is shown that generally heat transfer is governed both by natural circulation and crust formation phenomena. Results of this paper may be used for analysis of experiments with prototypic core materials.

Efficiency of osmotic pipe flows

DEFF Research Database (Denmark)

Haaning, Louise Sejling; Jensen, Kaare Hartvig; Helix Nielsen, Claus

2013-01-01

efficiency of these flows is limited by the presence of “unstirred” concentration boundary layers near the tube walls, and our primary aim is to understand and quantify these layers and their effect on the flow. We measure the outlet flow rate Qout while varying the inlet flow rate Q*, concentration c......We present experiments and theory for flows of sugar or salt solutions in cylindrical tubes with semipermeable walls (hollow fiber membranes) immersed in water, quantifying the strength of the osmotic driving force in relation to the dimensionless parameters that specify the system. The pumping...

Current reversal in a continuously periodic system driven by an additive noise and a multiplicative noise

International Nuclear Information System (INIS)

Wang Canjun; Chen Shibo; Mei Dongcheng

2006-01-01

We study the noise-induce transport and current reversal of Brownian particles in a continuously periodic potential driven by cross correlation between a multiplicative white noise and an additive white noise. We find that directed motion of the Brownian particles can be induced by the correlation between the additive noise and the multiplicative noise. The current reversal and the direction of the current is controlled by the values of the intensity (λ) of the correlated noises and a dimensionless parameter R (R=α/D, D is the intensity of multiplicative noise and α is the intensity of additive noise)

Sea surface stability parameters

International Nuclear Information System (INIS)

Weber, A.H.; Suich, J.E.

1978-01-01

A number of studies dealing with climatology of the Northwest Atlantic Ocean have been published in the last ten years. These published studies have dealt with directly measured meteorological parameters, e.g., wind speed, temperature, etc. This information has been useful because of the increased focus on the near coastal zone where man's activities are increasing in magnitude and scope, e.g., offshore power plants, petroleum production, and the subsequent environmental impacts of these activities. Atmospheric transport of passive or nonpassive material is significantly influenced by the turbulence structure of the atmosphere in the region of the atmosphere-ocean interface. This research entails identification of the suitability of standard atmospheric stability parameters which can be used to determine turbulence structure; the calculation of these parameters for the near-shore and continental shelf regions of the U.S. east coast from Cape Hatteras to Miami, Florida; and the preparation of a climatology of these parameters. In addition, a climatology for average surface stress for the same geographical region is being prepared

Analytical solution for dynamic pressurization of viscoelastic fluids

International Nuclear Information System (INIS)

Hashemabadi, S.H.; Etemad, S.Gh.; Thibault, J.; Golkar Naranji, M.R.

2003-01-01

The flow of simplified Phan-Thien-Tanner model fluid between parallel plates is studied analytically for the case where the upper plate moves at constant velocity. Two forms of the stress coefficient, linear and exponential, are used in the constitutive equation. For the linear stress coefficient, the dimensionless pressure gradient, the velocity profile and the product of friction factor and Reynolds number are obtained for a wide range of flow rate, Deborah number and elongational parameter. The results indicate the strong effects of the viscoelastic parameter on the velocity profile, the extremum of the velocity, and the friction factor. A correlation for the maximum pressure rise in single screw extruders is proposed. For the exponential stress coefficient, only velocity profiles were obtained and compared with velocity profiles obtained with the linear stress coefficient

Heat transfer enhancement by additive in vertical falling film absorption of H2O/LiBr

International Nuclear Information System (INIS)

Cheng Wenlong; Houda, Kouichi; Chen Zeshao; Akisawa, Atsushi; Hu Peng; Kashiwagi, Takao

2004-01-01

The enhancement effects of additive on vertical falling film of water into aqueous lithium bromide (LiBr) were studied by an experimental method. Based on the Navier-Stokes equations of falling film absorption, a new dimensionless parameter, surface renewal number Rn, was introduced, and a semi-empirical equation of enhancement factor of additive was obtained. It was shown that the absorption Marangoni number Ma, the surface Marangoni number M aA , and the surface renewal number Rn enhance the heat transfer of absorption, however the adsorption number Π and the Reynolds number Re weaken the heat transfer of absorption. It was proved that the semi-empirical equation agreed well with the experimental results by introduction of the parameters related to surface tension characters presented by the authors into the equation

Numerical simulation of a fractional model of temperature distribution and heat flux in the semi infinite solid

Directory of Open Access Journals (Sweden)

Anupama Choudhary

2016-03-01

Full Text Available In this paper, a fractional model for the computation of temperature and heat flux distribution in a semi-infinite solid is discussed which is subjected to spatially decomposing, time-dependent laser source. The apt dimensionless parameters are identified and the reduced temperature and heat flux as a function of these parameters are presented in a numerical form. Some special cases of practical interest are also discussed. The solution is derived by the application of the Laplace transform, the Fourier sine transform and their derivatives. Also, we developed an alternative solution of it by using the Sumudu transform, the Fourier transform and their derivatives. These results are received in compact and graceful forms in terms of the generalized Mittag-Leffler function, which are suitable for numerical computation.

Inertial-dissipation methods and turbulent fluxes at the air-ocean interface

DEFF Research Database (Denmark)

Fairall, C. W.; Larsen, Søren Ejling

1986-01-01

The use of high frequency atmospheric turbulence properties (inertial subrange spectra, structure function parameters or dissipation rates) to infer surface fluxes of momentum, sensible heat and latent heat is more practical for most ocean going platforms than direct covariance measurement....... The relationships required to deduce the fluxes from such data are examined in detail in this paper and several ambiguities and uncertainties are identified. It is noted that, over water, data on water vapor properties (the dimensionless functions for the mean profile, the structure function parameter...... and the variance transport term) are extremely sparse and the influence of sea spray is largely unknown. Special attention is given to flux estimation on the basis of the structure function formalism. Existing knowledge about the relevant similarity functions is summarized and discussed in light of the ambiguities...

A New Approach to Designing the S-Shaped Annular Duct for Industrial Centrifugal Compressor

Directory of Open Access Journals (Sweden)

Ivan Yurko

2014-01-01

Full Text Available The authors propose an analytical method for designing the inlet annular duct for an industrial centrifugal compressor using high-order Bezier curves. Using the design of experiments (DOE theory, the three-level full factorial design was developed for determination of influence of the dimensionless geometric parameters on the output criteria. Numerical research was carried out for determination of pressure loss coefficients and velocity swirl angles using the software system ANSYS CFX. Optimal values of the slope for a wide range of geometric parameters, allowing minimizing losses in the duct, have been found. The study has used modern computational fluid dynamics techniques to develop a generalized technique for future development of efficient variable inlet guide vane systems. Recommendations for design of the s-shaped annular duct for industrial centrifugal compressor have been given.

Expanding the catalog of binary black-hole simulations: aligned-spin configurations

Science.gov (United States)

Chu, Tony; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela; SXS Collaboration

2015-04-01

A major goal of numerical relativity is to model the inspiral and merger of binary black holes through sufficiently accurate and long simulations, to enable the successful detection of gravitational waves. However, covering the full parameter space of binary configurations is a computationally daunting task. The SXS Collaboration has made important progress in this direction recently, with a catalog of 174 publicly available binary black-hole simulations [black-holes.org/waveforms]. Nevertheless, the parameter-space coverage remains sparse, even for non-precessing binaries. In this talk, I will describe an addition to the SXS catalog to improve its coverage, consisting of 95 new simulations of aligned-spin binaries with moderate mass ratios and dimensionless spins as high as 0.9. Some applications of these new simulations will also be mentioned.

New fundamental parameters for attitude representation

Science.gov (United States)

Patera, Russell P.

2017-08-01

A new attitude parameter set is developed to clarify the geometry of combining finite rotations in a rotational sequence and in combining infinitesimal angular increments generated by angular rate. The resulting parameter set of six Pivot Parameters represents a rotation as a great circle arc on a unit sphere that can be located at any clocking location in the rotation plane. Two rotations are combined by linking their arcs at either of the two intersection points of the respective rotation planes. In a similar fashion, linking rotational increments produced by angular rate is used to derive the associated kinematical equations, which are linear and have no singularities. Included in this paper is the derivation of twelve Pivot Parameter elements that represent all twelve Euler Angle sequences, which enables efficient conversions between Pivot Parameters and any Euler Angle sequence. Applications of this new parameter set include the derivation of quaternions and the quaternion composition rule, as well as, the derivation of the analytical solution to time dependent coning motion. The relationships between Pivot Parameters and traditional parameter sets are included in this work. Pivot Parameters are well suited for a variety of aerospace applications due to their effective composition rule, singularity free kinematic equations, efficient conversion to and from Euler Angle sequences and clarity of their geometrical foundation.

Three-dimensional saturated-unsaturated flow with axial symmetry to a partially penetrating well in a compressible unconfined aquifer

Science.gov (United States)

Tartakovsky, Guzel D.; Neuman, Shlomo P.

2007-01-01

A new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer. The new solution generalizes that of Neuman (1972, 1974) by accounting for unsaturated flow above the water table. Three-dimensional, axially symmetric flow in the unsaturated zone is described by a linearized version of Richards' equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value (defining the interface between the saturated and unsaturated zones). Unsaturated soil properties are characterized by an exponent κ having the dimension of inverse length or, equivalently, a dimensionless exponent κD = κb, where b is initial saturated thickness. Our treatment of the unsaturated zone is similar to that of Kroszynski and Dagan (1975), who, however, have ignored internal (artesian) aquifer storage. According to Kroszynski and Dagan, aquifers that are not excessively shallow have values of κD (their parameter a) much greater than 10. We find that in such typical cases, unsaturated flow has little impact on early and late dimensionless time drawdown a short distance below the water table. Unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian-dominated to a late water-table-dominated flow regime. Delayed drainage from the unsaturated zone becomes less and less important as κD increases; as κD → ∞, this effect dies out, and drawdown is controlled entirely by delayed decline in the water table as in the model of Neuman. The unsaturated zone has a major impact on drawdown at intermediate time and a significant impact at early and late times, in the atypical case of κD ≤ 1, becoming the dominant factor as κD approaches zero (the soil water retention capacity becomes very large and/or saturated thickness becomes insignificant). Our

Improved Estimates of Thermodynamic Parameters

Science.gov (United States)

Lawson, D. D.

1982-01-01

Techniques refined for estimating heat of vaporization and other parameters from molecular structure. Using parabolic equation with three adjustable parameters, heat of vaporization can be used to estimate boiling point, and vice versa. Boiling points and vapor pressures for some nonpolar liquids were estimated by improved method and compared with previously reported values. Technique for estimating thermodynamic parameters should make it easier for engineers to choose among candidate heat-exchange fluids for thermochemical cycles.

α φ µ π ψ

African Journals Online (AJOL)

ADOWIE PERE

Volumetric flow rate, STB/D r. Radius, ft. D r. Dimensionless radius e r. External radius, ft. eD r. Dimensionless external radius w ... wellbore using the finite element method. Theory: The law of conservation of mass, Darcy's law and the equation of state has been combined to obtain the following partial differential equation:.

Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds

International Nuclear Information System (INIS)

Lee, H.A.; Chien, P.S.J.

1982-10-01

Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups

Analysis of graphite gasification by water vapor at different conversions

International Nuclear Information System (INIS)

Xiaowei, Luo; Xiaoyu, Yu; Suyuan, Yu; Jean-Charles, Robin

2014-01-01

Highlights: • Graphite was gasified at different conversions. • The reaction temperature influences on the dimensionless the reaction rate. • The thickness or radius influence on the dimensionless reaction rate. - Abstract: The gasification rate of porous solids varies with the conversions with the rate increasing to a maximum and then decreasing. Many graphite gasification experiments have illustrated that the maximum gasification rates occur at different conversions for different temperatures and sample geometries. Thus, the gasification rate is related to the conversion, temperature and geometry of the graphite. The influences of those factors were studied for the graphite gasification by water vapor. A theoretical analysis was done on the basis of several logical assumptions. The influence of temperatures on the reaction rate was investigated for plate-like and cylindrical graphite. The effects of thickness for a plate-like graphite sample and of radius for a cylindrical sample on the reaction rate were also studied theoretically. The results reveal that the maximum dimensionless reaction rate decreases with reaction temperature. The plate thickness or the cylinder radius also affects the maximum dimensionless reaction rate

Similarity rules of thermal stratification phenomena for water and sodium

International Nuclear Information System (INIS)

Ohtsuka, M.; Ikeda, T.; Yamakawa, M.; Shibata, Y.; Moriya, S.; Ushijima, S.; Fujimoto, K.

1988-01-01

Similarity rules for thermal stratification phenomena were studied using sodium and water experiments with scaled cylindrical vessels. The vessel dimensions were identical to focus on the effect of differences in fluid properties upon the phenomena. Comparisons of test results between sodium and water elucidated similar and dissimilar characteristics for thermal stratification phenomena which appeared in the scaled vessels. Results were as follows: (1) The dimensionless upward velocity of the thermal stratification interface was proportional to Ri -0.74 for water and sodium during the period when the buoyancy effect was dominant. (2) Dimensionless temperature transient rate at the outlet slit decreased with Ri for sodium and remained constant for water where Ri>0.2. The applicability of the scaled test results to an actual power plant was also studied by using multi-dimensional numerical analysis which was verified by the water and sodium experiments. Water experiments could simulate liquid metal fast breeder reactor flows more accurately than sodium experiments for dimensionless temperature gradient at the thermal stratification interface and dimensionless temperature transient rate at the intermediate heat exchanger inlet

Parameter identifiability and redundancy: theoretical considerations.

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Mark P Little

Full Text Available BACKGROUND: Models for complex biological systems may involve a large number of parameters. It may well be that some of these parameters cannot be derived from observed data via regression techniques. Such parameters are said to be unidentifiable, the remaining parameters being identifiable. Closely related to this idea is that of redundancy, that a set of parameters can be expressed in terms of some smaller set. Before data is analysed it is critical to determine which model parameters are identifiable or redundant to avoid ill-defined and poorly convergent regression. METHODOLOGY/PRINCIPAL FINDINGS: In this paper we outline general considerations on parameter identifiability, and introduce the notion of weak local identifiability and gradient weak local identifiability. These are based on local properties of the likelihood, in particular the rank of the Hessian matrix. We relate these to the notions of parameter identifiability and redundancy previously introduced by Rothenberg (Econometrica 39 (1971 577-591 and Catchpole and Morgan (Biometrika 84 (1997 187-196. Within the widely used exponential family, parameter irredundancy, local identifiability, gradient weak local identifiability and weak local identifiability are shown to be largely equivalent. We consider applications to a recently developed class of cancer models of Little and Wright (Math Biosciences 183 (2003 111-134 and Little et al. (J Theoret Biol 254 (2008 229-238 that generalize a large number of other recently used quasi-biological cancer models. CONCLUSIONS/SIGNIFICANCE: We have shown that the previously developed concepts of parameter local identifiability and redundancy are closely related to the apparently weaker properties of weak local identifiability and gradient weak local identifiability--within the widely used exponential family these concepts largely coincide.