Computational Study of Flow around ۲D and ۳D Tandem Bluff Bodies

Numerical simulations have been carried out to advance our current understanding of flow around two dimensional (۲D) and three dimensional (۳D) square shaped tandem bluff bodies at a Reynolds number of ۲۲,۰۰۰, especially to shed light on the sudden change of the downstream body’s drag coefficient. The Reynolds-Averaged Navier-Stokes (RANS) approach has been employed in the present study and the predicted drag coefficients compare reasonably well with available experimental data. Better understanding of flow fields has been achieved by analyzing streamlines, velocity vectors for both ۲D and ۳D cases in a horizontal plane and a vertical symmetric plane. The sudden jump in drag coefficient of the downstream body for the ۲D case is well captured numerically, which is due to the flow over the upstream body impinging onto the front face of the downstream body at a critical gap size between those two bodies. For the ۳D case the drag coefficient is predicted to increase gradually, consistent with the previous experimental finding. This is due to the fact that the vortical structures formed in the ۳D case are very different, resulting in a reasonably smooth change of the flow field around the upstream body and hence leading to a gradual, not sudden, increase in the drag coefficient of the downstream body.

Keywords:

Tandem bluff bodies , Drag coefficient , RANS , Numerical simulation