Turbulence fields in the lee of two‐dimensional transverse dunes simulated in a wind tunnel

The turbulence field of airflow in the lee of a dune has significant impacts on dune dynamics and related processes. We used particle image velocimetry in a wind tunnel simulation to obtain detailed velocity measurements in the lee of two‐dimensional transverse dune models, then used the results to analyse their turbulence fields. The dune models used in this study had a single lee angle of 30°, and a total of six stoss angles: 3°, 5°, 10°, 15°, 20° and 25°. We used vorticity, turbulence intensity, Reynolds stress and turbulent kinetic energy to characterize the turbulence fields. These parameters were functions of stoss angle, wind velocity, distance from the dune crest and height above the ground surface. The stoss angles could generally be divided into two groups based on the profiles of mean velocity, turbulence and Reynolds stress. Stoss angles of 3° and 5° usually had similar profiles, and angles of 15°, 20° and 25° formed a second group with similar profiles. The profiles for the stoss angle of 10° were usually transitional and were intermediate between the two groups. Vorticity, Reynolds stress and turbulent kinetic energy increased monotonically with increasing free‐stream wind velocity, but their variations with respect to the stoss angle were complex. The stoss angles of 15° and 20° had the maximum values of these three parameters, thus these angles may have special significance in dune development given the characteristics of the mean velocity fields and turbulence fields they produce within the lee airflow. It is the streamwise velocity component and its turbulence that determine the surface shear stress. Copyright © 2008 John Wiley and Sons, Ltd.

[1]  Z. Dong,et al.  A wind tunnel simulation of the effects of stoss slope on the lee airflow pattern over a two‐dimensional transverse dune , 2007 .

[2]  M. Baddock,et al.  The geomorphological significance of airflow patterns in transverse dune interdunes , 2007 .

[3]  Ian Livingstone,et al.  Geomorphology of desert sand dunes: A review of recent progress , 2007 .

[4]  D. Parsons,et al.  Numerical modelling of flow structures over idealized transverse aeolian dunes of varying geometry , 2004 .

[5]  Ian J. Walker,et al.  Simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel , 2003 .

[6]  Ian J. Walker,et al.  Dynamics of secondary airflow and sediment transport over and in the lee of transverse dunes , 2002 .

[7]  N. Lancaster,et al.  The effect of unsteady winds on sediment transport on the stoss slope of a transverse dune, Silver Peak, NV, USA , 2000 .

[8]  Ian J. Walker,et al.  Secondary airflow and sediment transport in the lee of a reversing dune , 1999 .

[9]  Sang Joon Lee,et al.  Laboratory measurements of velocity and turbulence field behind porous fences , 1999 .

[10]  G. Butterfield,et al.  Transitional behaviour of saltation: wind tunnel observations of unsteady winds , 1998 .

[11]  Nicholas Lancaster,et al.  Relations between dune morphology, air flow, and sediment flux on reversing dunes, Silver Peak, Nevada , 1997 .

[12]  Nicholas Lancaster,et al.  Sediment flux and airflow on the stoss slope of a barchan dune , 1996 .

[13]  G. Kocurek,et al.  Airflow up the stoss slope of sand dunes: limitations of current understanding , 1996 .

[14]  Andrew Warren,et al.  The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements , 1996 .

[15]  G. Kocurek,et al.  Toward a model for airflow on the lee side of aeolian dunes , 1996 .

[16]  Sean J. Bennett,et al.  Mean flow and turbulence structure over fixed, two-dimensional dunes: implications for sediment transport and bedform stability , 1995 .

[17]  G. Wiggs,et al.  Pulsed-wire anemometry on rough surfaces, with application to desert sand dunes , 1994 .

[18]  M. L. Sweet,et al.  Dune and Dune-Field Development on Padre Island, Texas, with Implications for Interdune Deposition and Water-Table-Controlled Accumulation , 1992 .

[19]  M. L. Sweet,et al.  An empirical model of aeolian dune lee-face airflow , 1990 .

[20]  K. Mulligan.  Velocity profiles measured on the windward slope of a transverse dune , 1988 .

[21]  S. R. McLean,et al.  A Model for Flow Over Two‐Dimensional Bed Forms , 1986 .

[22]  N. Lancaster.  Variations in wind velocity and sand transport on the windward flanks of desert sand dunes , 1985 .

[23]  H. Tsoar,et al.  Dynamic processes acting on a longitudinal (seif) sand dune , 1983 .

[24]  R. Folk.  Rollers and ripples in sand, streams and sky: rhythmic alteration of transverse and longitudinal vortices in three orders , 1976 .

[25]  William H. Snyder,et al.  Similarity criteria for the application of fluid models to the study of air pollution meteorology , 1972 .

[26]  V. Cornish.  On the Formation of Sand-Dunes , 1897 .