Uncertainty plays a significant role in the Benchmark on the Aerodynamics of a Rectangular Cylinder (BARC) with a chord-to-depth ratio of 5. In particular, besides modeling uncertainties and numerical errors, in numerical simulations it is difficult to exactly reproduce the experimental conditions due to uncertainties in the set up parameters, which sometimes cannot be exactly controlled or characterized. In this study, a computational sensitivity analysis and uncertainty quantification (UQ) study to the parametric uncertainties is carried out using probabilistic methods. The following uncertain set-up parameters are investigated in the subsequent uniform ranges: the angle of incidence α (-1o −1o), the free-stream longitudinal turbulence intensity Ix (0.001−0.03), and the free-stream turbulence length scale L (0.1D −5D), D being the cylinder depth. The Stochastic Collocation (SC) method is employed to perform the probabilistic uncertainty propagation of the three set-up parameters. This results in 25 URANS simulations based on the Smolyak sparse grid extension of the level-2 Clenshaw-Curtis quadrature points. The numerical error is estimated by comparing the results from computations on different mesh sizes. The findings are that the considered parameters have the largest impact on the time root mean square (t-rms) of the vertical force coefficient t-rms(cy) and of the surface pressure coefficient t-rms(Cp). These sensitivities are in agreement with previous BARC findings which indicate that those are the most dispersed parameters. There is a very good convergence of the UQ procedure and level 2 is sufficient. This additional UQ information can lead to new insights into the unresolved issues of the BARC flow test case.

17th AIAA Non-Deterministic Approaches Conference 2015

Witteveen, J.A.S, Omrani, P.S. (Pejman Shoeibi), Mariotti, A, & Salvetti, M.V. (2015). Uncertainty quantification of a rectangular 5:1 cylinder. In 17th AIAA Non-Deterministic Approaches Conference. doi:10.2514/6.2015-0663