Unsteady inflow conditions: A variationally based solution to the insurgence of pressure fluctuations

The application of unsteady inflow conditions represents an important aspect when scale resolving turbulence models are adopted in Computational Fluid Dynamics (CFD) analyses. In such context, with reference to Wind Engineering applications, the main concern is often represented by the generation of a synthetic velocity field representative of the turbulent fluctuations impinging on the studied body. Once such synthetic field has been generated, it is applied at the inflow patch. Unfortunately, such operation is not trivial: undesired pressure fluctuations are often generated due to the incompatibility between the applied inflow condition and the flow field found inside the computational domain. In this paper, a procedure able to guarantee a correct application of synthetically generated velocity fields to CFD simulations is described. The procedure, which relies on a variational background, is simple and can be readily implemented in existing codes. Numerical results confirm that, by adopting the proposed corrections, pressure fluctuations are strongly reduced, so confirming the soundness of the proposed approach. An OpenFoam implementation of the method is available for download at https://site.unibo.it/cwe-lamc/en.