Technical Papers and Presentations

Flow past a circular cylinder arises in many engineering applications, but there is significantly less work studying flow past a cylinder in a confined domain, such as pipe flow or flow in a plane channel. There are many applications where the scaling of a particular problem requires consideration of wall effects, such as blood flow past medical devices in arteries, flow past cylindrical structures close to walls, etc. Furthermore, while random and unstructured forms of surface roughness have been studied, such as ones that occur in nature, certain forms of structured roughness have not been given sufficient attention. For example, a 3D printed solid sometimes have waviness on its surface due to unwanted vibrations during the printing process, which prompts investigation of the resulting flow effects when consistent sinusoidal ridges are present. The present study uses the CFD Module of COMSOL Multiphysics® simulation software, to investigate flow past a confined circular cylinder with uniformly distributed sinusoidal ridges. We study the two-dimensional flow in three flow regimes, for Reynolds numbers of roughly 20, 200, and 500. In particular, we study the effect of varying the amplitude (the ridge height) and frequency (the total number of ridges) of the sinusoidal waviness. From these simulations, we measure the steady-state recirculation zone length in the laminar case and analyze the time-dependent drag and lift coefficients in the periodic shedding regime. For a fixed channel width and cylinder diameter, we find that changing the number of ridges most significantly influences the flow when a low number of ridges are present (<10), reflecting the fact that the cylinder geometry changes more drastically when there are few ridges. We find that the lift coefficient amplitude and mean drag coefficient tend to be higher with a larger ridge amplitude, whereas the Strouhal number tends to be lower. For a small number of ridges, the effect on the flow due to increased Reynolds number is inconsistent and depends heavily on the precise number of ridges, but for higher numbers of ridges, the trend mimics that of a smooth cylinder. We conclude that in certain cases, a cylinder with a sufficient number of sinusoidal ridges may behave in similar ways as a smooth circular cylinder.