Comparison of LES and measurements of flow over rough surfaces*

This paper presents simulations of turbulent flow over rough rough surfaces in a wind tunnel.
The simulated problem features a 3 m long section of the wind-tunnel with cross section 0.24 m × 0.25 m with a number of arrangement of roughness elements of several sizes. The measurements are performed with time-resolved PIV.  The computations are performed using the finite difference code ELMM (Extended Large-Eddy Microscale Model). The model uses the immersed boundary method to treat solid obstacles, such as the roughness elements and the turbulence-generating spires. The time-scale subgrid model is used to model the unresolved scales.  A 2-m long section of the tunnel is simulated in a coarse resolution of 2 mm and a nested domain with a higher resolution (1 mm) is located in the area that corresponds to the measurement section. These results are compared to simulations with 1 mm resolution in the entire domain.  The presentation will discuss the numerical method of domain nesting and compare velocity and Reynolds stress profiles, temporal spectra and results of coherent structures detection methods (e.g., wavelet, POD) to compare the structure of the turbulent flow measured and simulated.