Parametric forcing approach for secondary motions formation over inhomogeneous rough surfaces

A set of direct numerical simulations is used to analyse the application of the so-called parametric forcing approach (PFA), which allows computationally cheaper simulations, instead of high-resolution immersed boundary method (IBM) for modelling of a homogeneous and inhomogeneous rough surface.
It is observed that while the PFA delivers excellent agreement for homogeneous case, the agreement between IBM and PFA is rather limited for the inhomogeneous roughness. While secondary motion topology can be successfully reproduced with the PFA approach, the modification of the mean velocity profile and hence integral flow properties cannot be entirely matched between the two approaches.
It is shown that the application of homogeneous forcing to an inhomogeneous configuration might lead to deviation of the introduced forcing in the regions where topographical transition occurs so the global drag is altered.