Hydrodynamic damping in laminar, transient and turbulent regimes: Analytical and computational study

Abstract

A study of oscillating flow over a flat plate using RANS modeling was conducted to investigate hydrodynamic damping and its correlation with the unsteady and oscillating boundary layer. It is found that the predictions with the γ SST turbulence model was more consistent with the experimental results compared to the SST turbulence models. Two distinct damping behaviors were observed in the flow. For Reδ<400, the damping remained constant and matched the laminar solution of Stokes’ second problem. In this scenario, the flow regime was quasi-laminar, and an increase in free-stream velocity did not lead to a rise in the fluid damping coefficient. Conversely, for Reδ>400, the increase in Reδ induced turbulence during the deceleration phase, resulting in an amplification of the phase difference between displacement and wall shear stress, consequently increasing damping. This trend continued at higher values of Reδ and during the quasi-steady regime. The results indicated that the existence of different damping regions, as reported in previous studies, occurred within a range similar to that of Stokes’ second problem. A transition in the boundary layer regime at higher Reδ could be a contributing factor to the variations in damping behavior.