A Lagrangian roughness model integrated with the vortex method for drag coefficient estimation and flow control investigations around circular cylinder for a wide range of Reynolds numbers

摘要

This paper describes the development of a Lagrangian roughness model to simulate the effect of surface roughness in two-dimensional flow on the proximity of the cylinder, at high Reynolds numbers. The designed numerical model introduces a dynamic disturbance in the vicinity of the wall in addition to the distribution of triangular roughness elements in the body using the panel method, consolidating a refined boundary layer condition. A new discretization strategy for the vorticity field is used to make up a wide range of Reynolds numbers, 2 x 10(4) <= Re <= 6 x 10(5), which also ensures control of turbulence. It is integrated with the discrete vortex method-DVM and the second-order velocity structure function is applied for turbulence closure. The main findings are that numerically the drag coefficient depends on the relative roughness, the Reynolds number and the cutoff width of the characteristic vorticity distribution; the largest reductions in drag are observed for intermediate roughness compared to a smooth surface, reaching 51.6 for a relative roughness of 0.003 and Reynolds number set at 1.0 x 10(5); the core sizes of the discrete vortex need to be generated with different sizes for correct enforcement of the wall influence; it is possible to map the drag crisis under various flow conditions in cylinders with different surfaces, without the use of refined meshes and wall functions, using the DVM. OpenMP is implemented for average reductions of 80 in processing time. The considerable closeness with the experimental results reflects the applicability of the proposed method and the relevance of the two-dimensional approach for predicting unsteady aerodynamic forces on a cylinder with different rough surfaces for engineering purposes.