Numerical investigation of the influence of topography on simulated downburst wind fields

A, dry, non-hydrostatic sub-cloud model is used to simulate an isolated stationary downburst wind event to study the influence topographic features have on the near-ground wind structure of these storms. It was generally found that storm maximum wind speeds could be increased by up to 30% because of the presence of a topographic feature at the location of maximum wind speeds. Comparing predicted velocity profile amplification with that of a steady flow impinging jet, similar results were found despite the simplifications made in the impinging jet model. Comparison of these amplification profiles with those found in the simulated boundary layer winds reveal reductions of up to 30% in the downburst cases. Downburst and boundary layer amplification profiles were shown to become more similar as the topographic feature height was reduced with respect to the outflow depth.

[1]  J. Hunt,et al.  Turbulent wind flow over a low hill , 1975 .

[2]  Kiyotoshi Otsuka.  Effects of topography on the surface wind of an isolated wet microburst , 2006 .

[3]  Florian R. Menter,et al.  A Scale-Adaptive Simulation Model using Two-Equation Models , 2005 .

[4]  C. Letchford,et al.  Turbulence and topographic effects in simulated thunderstorm downdrafts by wind tunnel jet , 1999 .

[5]  Phillip Paevere,et al.  Measurements of topographic multipliers and flow separation from a steep escarpment. Part I. Full scale measurements , 1997 .

[6]  E. F. Bradley,et al.  Boundary-layer flow over low hills , 1987 .

[7]  J. D. Holmes,et al.  Wind Loading of Structures , 2001 .

[8]  Kenny C. S Kwok,et al.  Physical and numerical modelling of thunderstorm downbursts , 2001 .

[9]  Fred H. Proctor,et al.  Numerical simulations of an isolated microburst. I - Dynamics and structure , 1988 .

[10]  Eric Savory,et al.  Proposed large-scale modelling of the transient features of a downburst outflow , 2007 .

[11]  Abbas A. Alahyari,et al.  Dynamics of experimentally simulated microbursts , 1995 .

[12]  Nam-Ho Kyong,et al.  An experimental and numerical study on the flow over two-dimensional hills , 1997 .

[13]  J. D. Holmes,et al.  Numerical simulation of thunderstorm downdrafts , 1992 .

[14]  Matthew S. Mason,et al.  Impinging jet simulation of stationary downburst flow over topography , 2007 .

[15]  M. Hjelmfelt.  Structure and Life Cycle of Microburst Outflows Observed in Colorado , 1988 .

[16]  A. J. Bowen,et al.  A wind-tunnel investigation of the wind speed and turbulence characteristics close to the ground over various escarpment shapes , 1977 .

[17]  D. Sherman.  The Passage of a Weak Thunderstorn Downburst over an Instrumented Tower , 1987 .

[18]  Jerry M. Straka,et al.  A Three-Dimensional Numerical Analysis of Colliding Microburst Outflow Dynamics , 1996 .

[19]  John McCarthy,et al.  Microburst Wind Structure and Evaluation of Doppler Radar for Airport Wind Shear Detection , 1984 .

[20]  F. Fiedler,et al.  Modification of air flow over an escarpment — Results from the Hjardemål experiment , 1995 .

[21]  T. Fujita.  The Downburst: Microburst and Macroburst , 1985 .

[22]  Shuyang Cao,et al.  Experimental study on roughness effects on turbulent boundary layer flow over a two-dimensional steep hill , 2006 .

[23]  Kenny C. S Kwok,et al.  Measurements of topographic multipliers and flow separation from a steep escarpment. Part II. Model-scale measurements , 1997 .

[24]  D. C. Stevenson,et al.  Wind flow over ridges in simulated atmospheric boundary layers , 1981 .

[25]  Chris Letchford,et al.  Pulsed wall jet simulation of a stationary thunderstorm downburst, Part A: Physical structure and flow field characterization , 2005 .

[26]  Matthew S. Mason,et al.  Numerical simulation of downburst winds , 2009 .