The Experts below are selected from a list of 5151 Experts worldwide ranked by ideXlab platform

Zhangxin Chen - One of the best experts on this subject based on the ideXlab platform.

  • a reduced order model for chemical species transport in a tube with a constant wall concentration
    Canadian Journal of Chemical Engineering, 2018
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    A two-dimensional advection-diffusion model accompanied with a parabolic velocity profile of Poiseuille flow is considered for the chemical species transport in a tube with a constant wall concentration. The Reynolds Decomposition technique is applied to reduce it to an equivalent one-dimensional model for advective-dispersive transport in a tube through which the effective advection coefficient, the dispersion coefficient, and the effective Sherwood number are developed for the problem under study. The derived and the classical Taylor models are also compared in order to find the difference between the two arrangements. The reduced-order model for transport equation shows that the effective advection coefficient increases, whereas the dispersion coefficient in the tube decreases as compared to the classical Taylor equation. The effective Sherwood number for the steady state form of the developed model is found to be only a function of the Peclet number, which varies in the range of 3.215 ≤ Sh ≤ 4. These results find application in design of experiments and improve our understanding of mass transfer in microfluidic devices. This article is protected by copyright. All rights reserved

  • A reduced‐order model for chemical species transport in a tube with a constant wall concentration
    The Canadian Journal of Chemical Engineering, 2017
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    A two-dimensional advection-diffusion model accompanied with a parabolic velocity profile of Poiseuille flow is considered for the chemical species transport in a tube with a constant wall concentration. The Reynolds Decomposition technique is applied to reduce it to an equivalent one-dimensional model for advective-dispersive transport in a tube through which the effective advection coefficient, the dispersion coefficient, and the effective Sherwood number are developed for the problem under study. The derived and the classical Taylor models are also compared in order to find the difference between the two arrangements. The reduced-order model for transport equation shows that the effective advection coefficient increases, whereas the dispersion coefficient in the tube decreases as compared to the classical Taylor equation. The effective Sherwood number for the steady state form of the developed model is found to be only a function of the Peclet number, which varies in the range of 3.215 ≤ Sh ≤ 4. These results find application in design of experiments and improve our understanding of mass transfer in microfluidic devices. This article is protected by copyright. All rights reserved

  • shear dispersion in combined pressure driven and electro osmotic flows in a capillary tube with a porous wall
    Aiche Journal, 2015
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    An analytical expression is derived for the shear dispersion during transport of a neutral nonreacting solute within a coupled system comprised of a capillary tube and a porous medium under the combined effects of pressure-driven and electro-osmotic flows. We use the Reynolds Decomposition technique to obtain a dispersion coefficient by considering a sufficiently low wall or zeta potential that accounts for the combined flows. The coupled dispersion coefficient depends on the Debye–Huckel parameter, Poiseuille contribution fraction, and Peclet number. The developed model also provides a shear dispersion coefficient for an impervious capillary tube (noncoupled system). The ratio of the coupled (porous wall) and noncoupled (impervious) dispersion coefficients reveals that it is essential to include the transport of chemical species from the tube to the porous medium in several important physical situations. These findings have implications for design of chemical species transport in porous microfluidic networks and separation of emulsions in microchannel-membrane systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3981–3995, 2015

Reza S. Abhari - One of the best experts on this subject based on the ideXlab platform.

  • Aerodynamics of wind turbine wakes in flat and complex terrains
    Renewable Energy, 2016
    Co-Authors: Balaji Subramanian, Ndaona Chokani, Reza S. Abhari
    Abstract:

    The wake evolution measured downstream of multi-megawatt wind turbines located in flat and complex terrains are described here. These high-resolution measurements at full-scale Reynolds number conditions are made with an instrumented drone that is equipped with a suite of sensors and detail the characteristics of the mean flow and turbulent kinetic energy in the evolving wake. Reynolds Decomposition yields the nature of turbulent fluctuations in surface layer, and this Decomposition is used to detail the turbulence statistics, degree of anisotropy and friction velocity. These measurements are shown to be suited for the further development of three-dimensional wake models that are currently under intensive development.

Jason Monty - One of the best experts on this subject based on the ideXlab platform.

  • On the use of the Reynolds Decomposition in the intermittent region of turbulent boundary layers
    Journal of Fluid Mechanics, 2016
    Co-Authors: Y. S. Kwon, Nicholas Hutchins, Jason Monty
    Abstract:

    In the analysis of velocity fields in turbulent boundary layers, the traditional Reynolds Decomposition is universally employed to calculate the fluctuating component of streamwise velocity. Here, we demonstrate the perils of such a determination of the fluctuating velocity in the context of structural analysis of turbulence when applied in the outer region where the flow is intermittently turbulent at a given wall distance. A new Decomposition is postulated that ensures non-turbulent regions in the flow do not contaminate the fluctuating velocity components in the turbulent regions. Through this new Decomposition, some of the typical statistics concerning the scale and structure of turbulent boundary layers are revisited.

Morteza Dejam - One of the best experts on this subject based on the ideXlab platform.

  • a reduced order model for chemical species transport in a tube with a constant wall concentration
    Canadian Journal of Chemical Engineering, 2018
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    A two-dimensional advection-diffusion model accompanied with a parabolic velocity profile of Poiseuille flow is considered for the chemical species transport in a tube with a constant wall concentration. The Reynolds Decomposition technique is applied to reduce it to an equivalent one-dimensional model for advective-dispersive transport in a tube through which the effective advection coefficient, the dispersion coefficient, and the effective Sherwood number are developed for the problem under study. The derived and the classical Taylor models are also compared in order to find the difference between the two arrangements. The reduced-order model for transport equation shows that the effective advection coefficient increases, whereas the dispersion coefficient in the tube decreases as compared to the classical Taylor equation. The effective Sherwood number for the steady state form of the developed model is found to be only a function of the Peclet number, which varies in the range of 3.215 ≤ Sh ≤ 4. These results find application in design of experiments and improve our understanding of mass transfer in microfluidic devices. This article is protected by copyright. All rights reserved

  • A reduced‐order model for chemical species transport in a tube with a constant wall concentration
    The Canadian Journal of Chemical Engineering, 2017
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    A two-dimensional advection-diffusion model accompanied with a parabolic velocity profile of Poiseuille flow is considered for the chemical species transport in a tube with a constant wall concentration. The Reynolds Decomposition technique is applied to reduce it to an equivalent one-dimensional model for advective-dispersive transport in a tube through which the effective advection coefficient, the dispersion coefficient, and the effective Sherwood number are developed for the problem under study. The derived and the classical Taylor models are also compared in order to find the difference between the two arrangements. The reduced-order model for transport equation shows that the effective advection coefficient increases, whereas the dispersion coefficient in the tube decreases as compared to the classical Taylor equation. The effective Sherwood number for the steady state form of the developed model is found to be only a function of the Peclet number, which varies in the range of 3.215 ≤ Sh ≤ 4. These results find application in design of experiments and improve our understanding of mass transfer in microfluidic devices. This article is protected by copyright. All rights reserved

  • shear dispersion in combined pressure driven and electro osmotic flows in a capillary tube with a porous wall
    Aiche Journal, 2015
    Co-Authors: Morteza Dejam, Hassan Hassanzadeh, Zhangxin Chen
    Abstract:

    An analytical expression is derived for the shear dispersion during transport of a neutral nonreacting solute within a coupled system comprised of a capillary tube and a porous medium under the combined effects of pressure-driven and electro-osmotic flows. We use the Reynolds Decomposition technique to obtain a dispersion coefficient by considering a sufficiently low wall or zeta potential that accounts for the combined flows. The coupled dispersion coefficient depends on the Debye–Huckel parameter, Poiseuille contribution fraction, and Peclet number. The developed model also provides a shear dispersion coefficient for an impervious capillary tube (noncoupled system). The ratio of the coupled (porous wall) and noncoupled (impervious) dispersion coefficients reveals that it is essential to include the transport of chemical species from the tube to the porous medium in several important physical situations. These findings have implications for design of chemical species transport in porous microfluidic networks and separation of emulsions in microchannel-membrane systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3981–3995, 2015

Khaled J. Hammad - One of the best experts on this subject based on the ideXlab platform.

  • PIV Measurements of Turbulent Flows Over Single and Dual Rectangular Cavities
    Volume 7A: Fluids Engineering Systems and Technologies, 2015
    Co-Authors: Khaled J. Hammad, Kyle W. Saucier, Nicholas C. Koblick
    Abstract:

    Particle Image Velocimetry (PIV) was used to measure the turbulent flow fields over single and dual rectangular cavities. Four sets of PIV measurements were acquired, corresponding to two Reynolds numbers per each cavity configuration. The cavity depth based Reynolds number was varied between 21,000 and 42,000, while the cavity length-to-depth ratio was fixed at four. Galilean Decomposition is used to present instantaneous velocity fields. Turbulent velocity fields are presented using Reynolds Decomposition into mean and fluctuating components. Characteristics of the instantaneous and time-averaged velocity fields corresponding to a single cavity configuration are in agreement with the observations from previous studies. All mean flow field results display a large vortical structure spanning the entire length and height of each cavity. In the case of a dual cavity configuration, the free shear layer and trailing edge regions of the second cavity were found to always display higher streamwise and crosswise flow fluctuations in comparison with the first cavity. Furthermore, a wider free shear layer region is observed in the second cavity, in comparison with the first cavity.Copyright © 2015 by ASME

  • EFFECT OF Reynolds NUMBER ON THE TURBULENT FLOW STRUCTURE IN THE NEAR-WALL REGION OF AN IMPINGING ROUND JET
    ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1 Symposia – Parts A B C and D, 2011
    Co-Authors: Khaled J. Hammad, Ivana Milanovic
    Abstract:

    Time-Resolved Particle Image Velocimetry was used to study the effect of the Reynolds number on the turbulent flow structure of a submerged water jet impinging normally on a smooth and flat surface. A fully developed turbulent jet and a semi-confined flow configuration ensured properly characterized boundary conditions allowing for straightforward assessment of turbulence models and numerical schemes. The Reynolds number based on jet mean exit velocity was 5,000, 10,030 and 15,050 while the pipe-to-plate separation distance was fixed at two diameters. Turbulent velocity fields are presented using Reynolds Decomposition into mean and fluctuating components while Proper Orthogonal Decomposition (POD) analysis identified the most energetic coherent structures in the stagnation and wall-jet regions. NOMENCLATURE D Pipe internal diameter (m) H Pipe-to-plate separation distance (m) L Pipe length (m) Re Reynolds number ( b UD  )

  • Effect of Asymmetric Jet Placement on Turbulent Flow Structure Inside a Jet-Stirred Reactor
    Volume 7: Fluid Flow Heat Transfer and Thermal Systems Parts A and B, 2010
    Co-Authors: Khaled J. Hammad, Ivana Milanovic
    Abstract:

    Particle Image Velocimetry (PIV) was used to investigate the turbulent flow structure inside a jet-stirred cylindrical vessel. The submerged jet issued vertically downward from a long pipe ensuring fully developed turbulent flow conditions at the outlet. The Reynolds number based on jet mean exit velocity was 15,000. The effect of symmetric and asymmetric nozzle placement within the vessel on the resulting flow patterns was also studied. The measured turbulent velocity fields are presented using Reynolds Decomposition into mean and fluctuating components, which, for the selected flow configuration, inflow and boundary conditions, allow for straightforward assessment of turbulence models and numerical schemes. The flow field was subdivided into three regions: the jet, the jet-wall interaction and bulk of vessel. Proper Orthogonal Decomposition (POD) analysis was applied to identify the most energetic coherent structures of the turbulent flow field in the bulk of tank region. The swirling strength vortex identification technique was used to detect the existence and strength of vortical structures in the jet region.Copyright © 2010 by ASME

  • Liquid Jet Impingement on a Free Liquid Surface: PIV Study of the Turbulent Bubbly Two-Phase Flow
    ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting: Volume 1 Symposia – Parts A B and C, 2010
    Co-Authors: Khaled J. Hammad
    Abstract:

    The turbulent two-phase flow arising from the normal impingement of a round free-surface water jet on a horizontal air-water interface was experimentally studied. Due to the weakly viscous nature of the flow system under consideration, external perturbations or small variations in jet inflow conditions can lead to drastically different flow field characteristics under seemingly similar test conditions. In the current study, a fully developed turbulent jet, exiting a long pipe, ensured properly characterized inflow conditions. The study considered two jet inflow conditions; one entrained air and created a bubbly two-phase flow field while the other did not. Particle image velocimetry (PIV) was used to characterize the flow field beneath the interface, with and without air entrainment, for various nozzle-to-interface separation distances. Turbulent velocity fields of the continuous-phase and dispersed-phase were simultaneously measured in the developing flow region and presented using Reynolds Decomposition into mean and fluctuating components. The mean and RMS velocities of the two-phase flow field were compared with velocity measurements obtained under single-phase conditions.Copyright © 2010 by ASME

  • A Time-Resolved PIV Study of Vortical Structures in the Near-Wall Region of an Impinging Round Jet
    Volume 9: Heat Transfer Fluid Flows and Thermal Systems Parts A B and C, 2009
    Co-Authors: Khaled J. Hammad, Ivana Milanovic
    Abstract:

    Time-Resolved Particle Image Velocimetry (TR-PIV) was used to study the vortical structures resulting from a submerged water jet impinging normally on a smooth and flat surface. A fully developed turbulent jet, exiting a long pipe, and a semi-confined flow configuration ensured properly characterized boundary conditions, which allows for straightforward assessment of turbulence models and numerical schemes. The Reynolds number based on jet mean exit velocity was 23,000. The pipe-to-plate separation was varied between 2D and 7.6D. Turbulent velocity fields are presented using Reynolds Decomposition into mean and fluctuating components. Proper Orthogonal Decomposition (POD) analysis was used to identify the most energetic coherent structures of the turbulent flow field. Three velocity gradient-based vortex identification techniques, 2nd invariant Q, λ2 , and swirling strength, were found to perform equally well in identifying vortical structures along the impingement wall. The results clearly demonstrate the shortcomings of local vorticity as a vortex identifier in an impinging jet flow field.Copyright © 2009 by ASME