Urban Wake Field Generation Using LES


A. Single Building Wake

A. Single Building Wake

B. Top View of Wake (LES)

B. Top View of Wake (LES)

C. Top View of Wake (RANS)

C. Top View of Wake (RANS)

D. Side View of Wake (LES)

D. Side View of Wake (LES)

E. Side View of Wake (RANS)

E. Side View of Wake (RANS)

 

 

 

 

 

 

 

The manner in which the wake around an urban structure, or group of structures, is simulated numerically can have a significant impact on the resulting flowfield.  Shown in Fig. A are the small vortices within the wake of a single building perpendicular to the freestream wind.  The location and strength of these vortices vary with time making a Large Eddy Simulation (LES) a useful tool in capturing this effect.  However, LES simulations can be time consuming and a common approach in numerical modeling is to use Reynolds Averaged Navier Stokes (RANS) simulations.  The difference between the results can be seen by comparing Figs. B to C and Figs. D to E.  For the LES results, the colors represent the magnitude of the streamwise velocity (red and blue are in opposite directions), while for the RANS results the magnitude of the velocity increases from white to black while the direction is indicated by the arrow.