Couette-Poiseuille flow based non-linear flow over a square cylinder near plane wall

A numerical study on the flow over a square cylinder in the vicinity of a wall is conducted for different Couette-Poiseuille-based non-uniform flow with the non-dimensional pressure gradient P varying from 0 to 5. The nondimensional gap ratio L (=H /a ) is changed from 0.1 to 2, where H is gap height between the cylinder and wall, and a is the cylinder width. The governing equations are solved numerically through finite volume method based on SIMPLE algorithm on a staggered grid system. Both P and L have a substantial influence on the flow structure, time-mean drag coefficient C_D, fluctuating (rms) lift coefficient (C′_L), and Strouhal number St. The changes in P and L leads to four distinct flow regimes (I, II, III and IV). Following the flow structure change, the C_D , C′_L, and St all vary greatly with the change in L and/or P. The C_D and C′_L both grow with increasing P and/or L. The St increases with P for a given L, being less sensitive to L for a smaller P (< 2) and more sensitive to L for a larger P (> 2). A strong relationship is observed between the flow regimes and the values of C_D , C_L and St. An increase in P affects the pressure distribution more on the top surface than on bottom surface while an increase in L does the opposite.