The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Shu-qing Yang - One of the best experts on this subject based on the ideXlab platform.
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The prediction of turbulence intensities in unsteady flow
2014Co-Authors: Ishraq Alfadhli, Shu-qing Yang, Muttucumaru SivakumarAbstract:This study investigates the distribution of turbulence intensities in unsteady non-uniform flows. Yang and Chow's (2008) work was extended to express this distribution based on the relationship between Reynolds Shear Stress and turbulence intensities in unsteady flow. It was found a self-similarity relationship between Reynolds Shear Stress and turbulence intensities in unsteady flow. This relationship has been developed as empirical equations based on experimental data available in the literature. By applying the self-similarity relationship, good agreements between the measured and predicted turbulence intensities have been achieved.
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Distribution of Reynolds Shear Stress in steady and unsteady flows
13th SGEM GeoConference on WATER RESOURCES. FOREST MARINE AND OCEAN ECOSYSTEMS, 2013Co-Authors: Ishraq Alfadhli, Shu-qing Yang, Muttucumaru SivakumarAbstract:This study investigates the Reynolds Shear Stress distribution in steady and unsteady non-uniform flows. Specifically, it deals with how to express the deviation of this turbulence characteristic from that of uniform flow line; it is found that flow acceleration can well represent the deviation of Reynolds Shear Stress from its standard linear distribution. By connecting the flow acceleration with Reynolds Shear Stress, the study demonstrates empirically that the linear distrubiton of Reynolds Shear Stress can be observed when the flow acceleration is zero; the concave distribution of Reynolds Shear Stress can be observed when the flow acceleration is negative or when the flow velocity is decreased along the channel; the convex distribution of Reynolds Shear Stress can be observed when the flow acceleration is positive or the flow velocity is increased along the channel. These empirical results have been verified using published experimental data and good agreement between the predicted and observed profiles has been achieved.
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Turbulence structures in non-uniform flows
Advances in Water Resources, 2008Co-Authors: Shu-qing Yang, Alex T. ChowAbstract:This study investigates turbulence structures in steady and non-uniform flows. Equations of Reynolds Shear Stress and turbulent velocity fluctuations are derived and their physical interpretations are explained. The theoretical results show that, different from previous studies, the variation of water surface can generate the wall-normal velocity, resulting in deviations of Reynolds Shear Stress and turbulence intensities from those in uniform flows. A self-similarity relationship is found between the Reynolds Shear Stress and turbulence intensities in non-uniform flows. The existence of self-similarity indicates that the effect of non-uniformity does not influence the mixing length. An empirical equation has been proposed to express the relationship based on experimental data available in the literature. Good agreement is achieved between the measured and predicted turbulence intensities by applying the self-similarity relationship.
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Reynolds Shear Stress distributions in a gradually varied flow in a roughened channel
Journal of Hydraulic Research, 2007Co-Authors: Shu-qing Yang, Joong-woo LeeAbstract:The Reynolds Shear Stress distribution in non-uniform flows has been investigated. The theoretical results show that the wall-normal velocity causes the deviation of Reynolds Shear Stress from the standard linear distribution, i.e. , but the sum of Reynolds Shear Stress and the momentum flux, i.e. remains a linear distribution. By connecting the velocity gradient with Reynolds Shear Stress, the study demonstrates theoretically that the linear distribution of Reynolds Shear Stress and semi-logarithmic distribution of velocity (i.e., log-law) can be observed when and only when the wall-normal velocity is zero; the concave distribution of Reynolds Shear Stress and dip-phenomenon can be observed when and only when the wall-normal velocity is downward; the convex distribution of Reynolds Shear Stress can be observed and the wake-law correction is needed when and only when the upflow occurs. The theoretical results are in good agreement with experimental data
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Reynolds Shear Stress distributions in a gradually varied flow in a roughened channel distributions du cisaillement de Reynolds dans un ecoulement graduellement varie dans un canal rugueux
2007Co-Authors: Shu-qing Yang, Joong-woo LeeAbstract:ABSTRACTThe Reynolds Shear Stress distribution in non-uniform flows has been investigated. The theoretical results show that the wall-normal velocity causesthe deviation of Reynolds Shear Stress from the standard linear distribution, i.e. − uv/u 2∗ = 1 − y/h , but the sum of Reynolds Shear Stress andthe momentum flux, i.e. − (uv + u v)/u 2∗ remains a linear distribution. By connecting the velocity gradient with Reynolds Shear Stress, the studydemonstrates theoretically that the linear distribution of Reynolds Shear Stress and semi-logarithmic distribution of velocity (i.e., log-law) can beobserved when and only when the wall-normal velocity is zero; the concave distribution of Reynolds Shear Stress and dip-phenomenon can beobserved when and only when the wall-normal velocity is downward; the convex distribution of Reynolds Shear Stress can be observed and thewake-law correction is needed when and only when the upflow occurs. The theoretical results are in good agreement with experimental data.RESUMELa distribution du cisaillement de Reynolds dans des ecoulements non uniformes a ete etudiee. Les resultats theoriques montrent que la vitesse normalea la partoi produit une deviation du cisaillement de Reynolds par rapport a la distribution lineaire standard, i.e. −
Joseph Klewicki - One of the best experts on this subject based on the ideXlab platform.
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Statistical evidence of anasymptotic geometric structure to the momentum transporting motions in turbulent boundary layers
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2017Co-Authors: Caleb Morrill-winter, Jimmy Philip, Joseph KlewickiAbstract:The turbulence contribution to the mean flow is reflected by the motions producing the Reynolds Shear Stress (uv) and its gradient. Recent analyses of the mean dynamical equation, along with data, ...
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Mesoscaling of Reynolds Shear Stress in Turbulent Channel and Pipe Flows.
AIAA Journal, 2005Co-Authors: Tie Wei, Patrick Mcmurtry, Joseph Klewicki, Paul C. FifeAbstract:Experimental and numerical data of the Reynolds Shear Stress in turbulent channel and pipe flows under a mesonormalization are presented. The mesolength scale associated with this normalization is intermediate to the traditional inner and outer lengths. Justification for the mesoscales is provided by a direct analysis of the mean momentum equation. Specifically, the mesonormalization is revealed through a rescaling that appropriately reflects the physics of an internal mesolayer within which a balance breaking, and subsequent balance exchange of terms in the mean momentum equation takes place. Direct numerical simulation and experimental data are examined and shown to be in good agreement with the new scaling, supporting the new theory.
Tie Wei - One of the best experts on this subject based on the ideXlab platform.
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scaling of the mean transverse flow and Reynolds Shear Stress in turbulent plane jet
Physics of Fluids, 2021Co-Authors: Tie Wei, Daniel LivescuAbstract:Proper scaling for the mean transverse flow and Reynolds Shear Stress in a turbulent plane jet is determined using a scaling patch approach. By seeking an admissible scaling, a key concept in the scaling patch approach, for the mean continuity equation, a proper scale for the mean transverse flow in a turbulent plane jet is found as V ref = − δ d U ctr / d x, where δ is the jet half width and d U ctr / d x is the decay rate of the mean axial velocity at the jet centerline. By seeking an admissible scaling for the mean axial momentum equation, a proper scale for the kinematic Reynolds Shear Stress is found as R u v , ref = U ctr V ref, which is a mix of the velocity scales in the axial and transverse directions. Approximation functions for the scaled mean transverse flow and Reynolds Shear Stress are developed and found to agree well with experimental and numerical data. Similarities and differences between the scales of the mean transverse flow and Reynolds Shear Stress in turbulent plane jets and zero-pressure-gradient turbulent boundary layer flows are clarified.
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Mesoscaling of Reynolds Shear Stress in Turbulent Channel and Pipe Flows.
AIAA Journal, 2005Co-Authors: Tie Wei, Patrick Mcmurtry, Joseph Klewicki, Paul C. FifeAbstract:Experimental and numerical data of the Reynolds Shear Stress in turbulent channel and pipe flows under a mesonormalization are presented. The mesolength scale associated with this normalization is intermediate to the traditional inner and outer lengths. Justification for the mesoscales is provided by a direct analysis of the mean momentum equation. Specifically, the mesonormalization is revealed through a rescaling that appropriately reflects the physics of an internal mesolayer within which a balance breaking, and subsequent balance exchange of terms in the mean momentum equation takes place. Direct numerical simulation and experimental data are examined and shown to be in good agreement with the new scaling, supporting the new theory.
Satya P. Ojha - One of the best experts on this subject based on the ideXlab platform.
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Conditional statistics of Reynolds Shear Stress in flow over 2D dunes in the presence of surface waves
Hydrological Processes, 2013Co-Authors: Satya P. OjhaAbstract:This study presents the analysis of the velocity fluctuations to describe the conditional statistics of Reynolds Shear Stress in flow over two-dimensional dunes in the presence of surface waves of varying frequency. The flow velocity measurements over the dunes are made using a 16-MHz 3D acoustic Doppler velocimeter. The joint probability distributions of the normalized stream-wise and vertical velocity fluctuations at different vertical locations are calculated in the trough region of a selected dune in quasi-steady region of the flow. Third-order moments of the stream-wise and vertical velocity components over one dune length are also calculated throughout the flow depth for understanding the effect of surface waves on relative contributions to the Reynolds Shear Stress due to the four quadrant events. The structure of instantaneous Reynolds Stresses is analysed using quadrant analysis technique. It has been shown that the contributions of second and fourth quadrant events to the Reynolds Shear Stress increase with increase in the frequency of surface waves. In fact, the largest contribution to turbulent Stresses comes from the second quadrant. The cumulant discard method is applied to describe the statistical properties of the covariance term u′w′. Conditional statistics and conditional sampling are used to compare the experimental and theoretical relative contributions to the Reynolds Shear Stress from the four quadrant events. Copyright © 2013 John Wiley & Sons, Ltd.
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CONTRIBUTIONS OF BURST-SWEEP CYCLES TO THE Reynolds Shear Stress OVER THE WAVEFORM STRUCTURES
ISH Journal of Hydraulic Engineering, 2006Co-Authors: B. S. Mazumder Fish, Debasish Pal, Koeli Ghoshal, Satya P. OjhaAbstract:ABSTRACT The purpose of the present paper is to investigate the contributions of turbulent events to the total Reynolds Shear Stress over artificial waveforms and to make a comparative study of turbulence between two types of isolated wave geometries: the scalene triangular shape (STS) and the isosceles triangular shape (ITS). All three components of velocity with fluctuations have been measured using 3-D Micro- Acoustic Doppler Velocimeter (ADV) at the Indian Statistical Institute's (ISI) flume, Calcutta. The motivation of this study is to determine the spatial changes of flow and turbulent events, and to gain better understanding of the physics of flow, which are responsible for the transport of sediment.
Daniel Livescu - One of the best experts on this subject based on the ideXlab platform.
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scaling of the mean transverse flow and Reynolds Shear Stress in turbulent plane jet
Physics of Fluids, 2021Co-Authors: Tie Wei, Daniel LivescuAbstract:Proper scaling for the mean transverse flow and Reynolds Shear Stress in a turbulent plane jet is determined using a scaling patch approach. By seeking an admissible scaling, a key concept in the scaling patch approach, for the mean continuity equation, a proper scale for the mean transverse flow in a turbulent plane jet is found as V ref = − δ d U ctr / d x, where δ is the jet half width and d U ctr / d x is the decay rate of the mean axial velocity at the jet centerline. By seeking an admissible scaling for the mean axial momentum equation, a proper scale for the kinematic Reynolds Shear Stress is found as R u v , ref = U ctr V ref, which is a mix of the velocity scales in the axial and transverse directions. Approximation functions for the scaled mean transverse flow and Reynolds Shear Stress are developed and found to agree well with experimental and numerical data. Similarities and differences between the scales of the mean transverse flow and Reynolds Shear Stress in turbulent plane jets and zero-pressure-gradient turbulent boundary layer flows are clarified.