CFD Simulations

Recently CFD simulations have been used with realistic inflow turbulence, and the results show potential for complementing wind tunnel testing to better predict wind-induced loads at full-scale. When the boundary conditions are controlled in a more realistic way, by using a virtual boundary-layer wind tunnel as the computational domain and including all the floor roughness elements incorporated in the test model, i.e. ‘apple to apple’ comparison between the CFD and the experimental results, the CFD results are very close to those obtained by physical testing. However, CFD simulations have the advantages of not incorporating instruments and hence eliminating their interference effects on the test object. CFD simulations allow for full-scale modeling, which is a challenge with physical experiments in artificial winds, lacking fully developed turbulence with a realistic integral length scale. Nevertheless, one main shortcoming of a CFD based approach is being computationally costly to predict peak loads on structures under turbulent flows. When a relatively accurate turbulence model like Large Eddy Simulations (LES) is incorporated into the numerical modeling at high Reynolds number, the CFD simulations may need high performance computing capabilities. This challenge, coupled with the costly commercial CFD license for parallel computing is limiting CFD for design wind load evaluation in practice. Wind tunnel experiments still remain an economic choice compared to CFD simulations, for wind load applications. However, concurrent CFD studies provide additional opportunities to explain/augment wind tunnel studies.

CFD simulations allow for full-scale modeling, which is a challenge with physical experiments in artificial winds

 

CFD with LES turbulence closure is implemented on a scale 1:1 prototype building. A proximity study was executed computationally in CFD with LES that suggests new recommendations on the computational domain size, in front of a building model, apart from common RANS-based guidelines (e.g., COST and AIJ). Our findings suggest a location of the test building, different from existing guidelines, and the inflow boundary proximity influences pressure correlation and reproduction of peak loads. The CFD LES results are compared to corresponding pressures from open jet, full scale, wind tunnel, and the ASCE 7-10 standard for roof Component & Cladding design. The CFD LES shows its adequacy to produce peak pressures/loads on buildings, in agreement with field pressures, due to its capabilities of reproducing the spectral contents of the inflow at 1:1 scale.

Selected Publications