Rare backflow and extreme wall-normal velocity fluctuations in near-wall turbulence

Rare negative streamwise velocities and extreme wall-normal velocity fluctuations near the wall are investigated for turbulent channel flow at a series of Reynolds numbers based on friction velocity up to Reτ = 1000. Probability density functions of the wall-shear stress and velocity components are presented as well as joint probability density functions of the velocity components and the pressure. Backflow occurs more often (0.06% at the wall at Reτ = 1000) and further away (up to y+ = 8.5) from the wall for increasing Reynolds number. The regions of backflow are circular with an average diameter, based on ensemble averages, of approximately 20 viscous units independent of Reynolds number. A strong oblique vortex outside the viscous sublayer is found to cause this backflow. Extreme wall-normal velocity events occur also more often for increasing Reynolds number. These extreme fluctuations cause high flatness values near the wall (F(v) = 43 at Reτ = 1000). Positive and negative velocity spikes appear in p...

[1]  Motoaki Kimura,et al.  Statistical analysis on wall shear stress of turbulent boundary layer in a channel flow using micro-shear stress imager , 1999 .

[2]  D. B. Degraaff,et al.  Reynolds number scaling of the turbulent boundary layer on a flat plate and on swept and unswept bumps , 1999 .

[3]  Michel Stanislas,et al.  Experimental study of eddy structures in a turbulent boundary layer using particle image velocimetry , 2005, Journal of Fluid Mechanics.

[4]  Ivan Marusic,et al.  Hot-wire spatial resolution issues in wall-bounded turbulence , 2009, Journal of Fluid Mechanics.

[5]  Dan S. Henningson,et al.  Simulations of Spatially Evolving Turbulent Boundary Layers up to Reθ = 4300 , 2010 .

[6]  Luca Ridolfi,et al.  An experimental contribution to near-wall measurements by means of a special laser Doppler anemometry technique , 2002 .

[7]  John B. McLaughlin,et al.  Large‐scale computer simulation of fully developed turbulent channel flow with heat transfer , 1991 .

[8]  S. Deutsch,et al.  The structure of Reynolds stress in the near-wall region of a fully developed turbulent pipe flow , 1992 .

[9]  Ramis Örlü,et al.  On the fluctuating wall-shear stress in zero pressure-gradient turbulent boundary layer flows , 2011 .

[10]  Wolfgang Schröder,et al.  Two-Dimensional Visualization of Turbulent Wall Shear Stress Using Micropillars , 2009 .

[11]  Chiang Juay Teo,et al.  Dynamic response of a hot-wire anemometer. Part II: A flush-mounted hot-wire and hot-film probes for wall shear stress measurements , 1998 .

[12]  W. C. Reynolds,et al.  Measurement of turbulent wall velocity gradients using cylindrical waves of laser light , 1991 .

[13]  Ramis Örlü,et al.  On near wall measurements of wall bounded flows-The necessity of an accurate determination of the wall position , 2010 .

[14]  Fazle Hussain,et al.  Coherent structure generation in near-wall turbulence , 2002, Journal of Fluid Mechanics.

[15]  Jens M. Österlund,et al.  Experimental studies of zero pressure-gradient turbulent boundary layer flow , 1999 .

[16]  P. Moin,et al.  Turbulence statistics in fully developed channel flow at low Reynolds number , 1987, Journal of Fluid Mechanics.

[17]  Javier Jiménez,et al.  Scaling of the energy spectra of turbulent channels , 2003, Journal of Fluid Mechanics.

[18]  Richard M. Lueptow,et al.  Wall shear stress and velocity in a turbulent axisymmetric boundary layer , 1994, Journal of Fluid Mechanics.

[19]  John K. Eaton,et al.  A high-resolution laser Doppler anemometer: design, qualification, and uncertainty , 2001 .

[20]  T. J. Hanratty,et al.  Measurements of turbulent flow in a channel at low Reynolds numbers , 1990 .

[21]  P. Spalart,et al.  Numerical study of a separation bubble with heat transfer , 1997 .

[22]  Measurements and scaling of wall shear stress fluctuations , 2003 .

[23]  F. Durst,et al.  On the Difficulties in Resolving the Viscous Sublayer in Wall-Bounded Turbulence , 2004 .

[24]  H. H. Bruun,et al.  Hot-Wire Anemometry: Principles and Signal Analysis , 1996 .

[25]  Ramis Örlü,et al.  The viscous sublayer revisited–exploiting self-similarity to determine the wall position and friction velocity , 2011 .

[26]  The topology of skin friction and surface vorticity fields in wall-bounded flows , 2012 .

[27]  W. Schröder,et al.  Feasability study of wall shear stress imaging using microstructured surfaces with flexible micropillars , 2005 .

[28]  den Jmj Jaap Toonder,et al.  Origin of high kurtosis levels in the viscous sublayer : direct numerical simulation and experiment , 1996 .

[29]  J. Eaton,et al.  Reynolds-number scaling of the flat-plate turbulent boundary layer , 2000, Journal of Fluid Mechanics.

[30]  J. Westerweel,et al.  Effect of Strong External Turbulence on a Wall Jet Boundary Layer , 2007 .

[31]  Neil D. Sandham,et al.  Wall Pressure and Shear Stress Spectra from Direct Simulations of Channel Flow , 2006 .

[32]  F. Durst,et al.  LDA measurements in the near-wall region of a turbulent pipe flow , 1995, Journal of Fluid Mechanics.

[33]  Scaling properties of turbulent pipe flow at low Reynolds number , 2001 .

[34]  W. Schröder,et al.  High Reynolds number turbulent wind tunnel boundary layer wall-shear stress sensor , 2009 .

[35]  Ramis Örlü,et al.  The diagnostic plot - a litmus test for wall bounded turbulence data , 2010 .

[36]  Shinnosuke Obi,et al.  Experimental study on the statistics of wall shear stress in turbulent channel flows , 1996 .

[37]  Joseph Klewicki,et al.  On accurately measuring statistics associated with small-scale structure in turbulent boundary layers using hot-wire probes , 1990, Journal of Fluid Mechanics.

[38]  R. Mathis,et al.  Large-scale amplitude modulation of the small-scale structures in turbulent boundary layers , 2009, Journal of Fluid Mechanics.

[39]  A. Sasoh,et al.  Interactions among baroclinically-generated vortex rings in building up an acting spike to a bow shock layer , 2011 .

[40]  P. Schlatter,et al.  Quantifying the interaction between large and small scales in wall-bounded turbulent flows: A note of caution , 2010 .

[41]  H. Eckelmann,et al.  The fluctuating wall‐shear stress and the velocity field in the viscous sublayer , 1988 .

[42]  den Jmj Jaap Toonder,et al.  Reynolds number effects in a turbulent pipe flow for low to moderate Re , 1997 .

[43]  Helmut Eckelmann,et al.  The structure of the viscous sublayer and the adjacent wall region in a turbulent channel flow , 1974, Journal of Fluid Mechanics.

[44]  E. Krause,et al.  Comparative measurements in the canonical boundary layer at Reδ2≤6×104 on the wall of the German–Dutch windtunnel , 1995 .

[45]  M. Gad-el-Hak,et al.  MEMS-based pressure and shear stress sensors for turbulent flows , 1999 .

[46]  Ramis Örlü,et al.  Assessment of direct numerical simulation data of turbulent boundary layers , 2010, Journal of Fluid Mechanics.

[47]  Mark Sheplak,et al.  Modern developments in shear-stress measurement ☆ , 2002 .

[48]  Dan S. Henningson,et al.  SIMSON : A Pseudo-Spectral Solver for Incompressible Boundary Layer Flows , 2007 .

[49]  John Kim,et al.  DIRECT NUMERICAL SIMULATION OF TURBULENT CHANNEL FLOWS UP TO RE=590 , 1999 .