The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Charles Meneveau - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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Large-eddy simulation study of the Logarithmic Law for second and higher-order moments in turbulent wall-bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models, and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds number experimental boundary layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations $u'^{+}$ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high Reynolds number wall-modeled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a `Townsend-Perry' constant of $A_1\approx 1.25$. The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between $A_p$, the generalized `Townsend-Perry' constants for moments of order $2p$, from experiments and simulations. Both are indicative of sub-Gaussian behavior of the streamwise velocity fluctuations. The near-wall behavior of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness scale $z_0$, the LES grid scale $\Delta$, and sub-grid scale (SGS) mixing length $C_s\Delta$ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity.
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Generalized Logarithmic Law for high-order moments in turbulent boundary layers
Journal of Fluid Mechanics, 2013Co-Authors: Charles Meneveau, Ivan MarusicAbstract:High-Reynolds-number data in turbulent boundary layers are analysed to examine statistical moments of streamwise velocity fluctuations ${u}^{\prime } $ . Prior work has shown that the variance of ${u}^{\prime } $ exhibits Logarithmic behaviour with distance to the surface, within an inertial sublayer. Here we extend these observations to even-order moments. We show that the $2p$ -order moments, raised to the power $1/ p, $ also follow Logarithmic behaviour according to $\langle \mathop{({u}^{\prime + } ){}^{2p} \rangle }\nolimits ^{1/ p} = {B}_{p} - {A}_{p} \ln (z/ \delta )$ , where ${u}^{\prime + } $ is the velocity fluctuation normalized by the friction velocity, $\delta $ is an outer length scale and ${B}_{p} $ are non-universal constants. The slopes ${A}_{p} $ in the Logarithmic region appear quite insensitive to Reynolds number, consistent with universal behaviour for wall-bounded flows. The slopes differ from predictions that assume Gaussian statistics, and instead are consistent with sub-Gaussian behaviour.
Richard J A M Stevens - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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Large-eddy simulation study of the Logarithmic Law for second and higher-order moments in turbulent wall-bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models, and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds number experimental boundary layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations $u'^{+}$ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high Reynolds number wall-modeled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a `Townsend-Perry' constant of $A_1\approx 1.25$. The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between $A_p$, the generalized `Townsend-Perry' constants for moments of order $2p$, from experiments and simulations. Both are indicative of sub-Gaussian behavior of the streamwise velocity fluctuations. The near-wall behavior of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness scale $z_0$, the LES grid scale $\Delta$, and sub-grid scale (SGS) mixing length $C_s\Delta$ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity.
Michael Wilczek - One of the best experts on this subject based on the ideXlab platform.
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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large eddy simulation study of the Logarithmic Law for second and higher order moments in turbulent wall bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds-number experimental boundary-layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations u ′+ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high-Reynolds-number wall-modelled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a ‘Townsend–Perry’ constant of A 1 ≈1.25 . The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between A p , the generalized ‘Townsend–Perry’ constants for moments of order 2p , from experiments and simulations. Both are indicative of sub-Gaussian behaviour of the streamwise velocity fluctuations. The near-wall behaviour of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness length z 0 , the LES grid scale Δ , and subgrid scale mixing length C s Δ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity
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Large-eddy simulation study of the Logarithmic Law for second and higher-order moments in turbulent wall-bounded flow
Journal of Fluid Mechanics, 2014Co-Authors: Richard J A M Stevens, Michael Wilczek, Charles MeneveauAbstract:The Logarithmic Law for the mean velocity in turbulent boundary layers has long provided a valuable and robust reference for comparison with theories, models, and large-eddy simulations (LES) of wall-bounded turbulence. More recently, analysis of high-Reynolds number experimental boundary layer data has shown that also the variance and higher-order moments of the streamwise velocity fluctuations $u'^{+}$ display Logarithmic Laws. Such experimental observations motivate the question whether LES can accurately reproduce the variance and the higher-order moments, in particular their Logarithmic dependency on distance to the wall. In this study we perform LES of very high Reynolds number wall-modeled channel flow and focus on profiles of variance and higher-order moments of the streamwise velocity fluctuations. In agreement with the experimental data, we observe an approximately Logarithmic Law for the variance in the LES, with a `Townsend-Perry' constant of $A_1\approx 1.25$. The LES also yields approximate Logarithmic Laws for the higher-order moments of the streamwise velocity. Good agreement is found between $A_p$, the generalized `Townsend-Perry' constants for moments of order $2p$, from experiments and simulations. Both are indicative of sub-Gaussian behavior of the streamwise velocity fluctuations. The near-wall behavior of the variance, the ranges of validity of the Logarithmic Law and in particular possible dependencies on characteristic length scales such as the roughness scale $z_0$, the LES grid scale $\Delta$, and sub-grid scale (SGS) mixing length $C_s\Delta$ are examined. We also present LES results on moments of spanwise and wall-normal fluctuations of velocity.
Ivan Marusic - One of the best experts on this subject based on the ideXlab platform.
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On the mixing length eddies and Logarithmic mean velocity profile in wall turbulence.
arXiv: Fluid Dynamics, 2020Co-Authors: Michael Heisel, Charitha M. De Silva, Nicholas Hutchins, Ivan Marusic, Michele GualaAbstract:Since the introduction of the Logarithmic Law of the wall more than 80 years ago, the equation for the mean velocity profile in turbulent boundary layers has been widely applied to model near-surface processes and parameterise surface drag. Yet the hypothetical turbulent eddies proposed in the original Logarithmic Law derivation and mixing length theory of Prandtl have never been conclusively linked to physical features in the flow. Here, we present evidence that suggests these eddies correspond to regions of coherent streamwise momentum known as uniform momentum zones (UMZs). The arrangement of UMZs results in a step-like shape for the instantaneous velocity profile, and the smooth mean profile results from the average UMZ properties, which are shown to scale with the friction velocity and wall-normal distance in the Logarithmic region. These findings are confirmed across a wide range of Reynolds number and surface roughness conditions from the laboratory scale to the atmospheric surface layer.
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Defining the eddies responsible for the Logarithmic velocity profile in wall turbulence
arXiv: Fluid Dynamics, 2019Co-Authors: Michael Heisel, Charitha M. De Silva, Nicholas Hutchins, Ivan Marusic, Michele GualaAbstract:Since the introduction of the Logarithmic Law of the wall more than 80 years ago, the equation for the mean velocity profile in turbulent boundary layers has been widely applied to model near-surface processes and parameterise surface drag. Yet the hypothetical turbulent eddies proposed in the original Logarithmic Law derivation and mixing length theory of Prandtl have never been conclusively linked to physical features in the flow. Here, we present evidence that suggests these eddies correspond to regions of coherent streamwise momentum known as uniform momentum zones (UMZs). The arrangement of UMZs results in a step-like shape for the instantaneous velocity profile, and the smooth mean profile results from the average UMZ properties, which are shown to scale with the friction velocity and wall-normal distance in the Logarithmic region. These findings are confirmed across a wide range of Reynolds number and surface roughness conditions from the laboratory scale to the atmospheric surface layer.
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Generalized Logarithmic Law for high-order moments in turbulent boundary layers
Journal of Fluid Mechanics, 2013Co-Authors: Charles Meneveau, Ivan MarusicAbstract:High-Reynolds-number data in turbulent boundary layers are analysed to examine statistical moments of streamwise velocity fluctuations ${u}^{\prime } $ . Prior work has shown that the variance of ${u}^{\prime } $ exhibits Logarithmic behaviour with distance to the surface, within an inertial sublayer. Here we extend these observations to even-order moments. We show that the $2p$ -order moments, raised to the power $1/ p, $ also follow Logarithmic behaviour according to $\langle \mathop{({u}^{\prime + } ){}^{2p} \rangle }\nolimits ^{1/ p} = {B}_{p} - {A}_{p} \ln (z/ \delta )$ , where ${u}^{\prime + } $ is the velocity fluctuation normalized by the friction velocity, $\delta $ is an outer length scale and ${B}_{p} $ are non-universal constants. The slopes ${A}_{p} $ in the Logarithmic region appear quite insensitive to Reynolds number, consistent with universal behaviour for wall-bounded flows. The slopes differ from predictions that assume Gaussian statistics, and instead are consistent with sub-Gaussian behaviour.
Radhakrishnan Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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The importance of higher-order effects in the Barenblatt–Chorin theory of wall-bounded fully developed turbulent shear flows
Physics of Fluids, 1998Co-Authors: Radhakrishnan SrinivasanAbstract:Barenblatt [J. Fluid Mech. 248, 513 (1993)] proposed a Reynolds number (R)-dependent power Law for the mean velocity near the wall in fully developed turbulent shear flows. In an appropriate region, as R→∞, the envelope of the velocity profiles reduces to a Logarithmic Law with an additive constant that is significantly larger than that of the universal Logarithmic Law. This discrepancy is removed upon including a higher-order term in the power-Law exponent. Using the friction (instead of average) velocity in the definition of R destroys the invariance of the nonvanishing higher-order terms of the power Law as R→∞.
