Numerical investigation of two-dimensional laminar flow past various oscillating cylinder

Abstract

Two-dimensional laminar flow over oscillating cylinder is analyzed numerically. Three different cylinder shapes namely circular, square, and ellipse are considered for analysis. Cylinder shapes are set to oscillate at frequency ranged such that frequency ratio (oscillating frequency/natural vortex shedding frequency, fr) varies between 0.8 and 1.2. The oscillation amplitude is varied between 30 and 50% of the cylinder diameter at fixed Reynolds number of 185. Numerical study is carried out using dynamic mesh features of commercial code FLUENT. Simple harmonic motion to the cylinder is applied using user-defined function (UDF) facility of FLUENT. The formation of anticlockwise or clockwise motion vortices from surface of cylinder depends upon geometrical shape of the cylinder as well as frequency ratio of oscillation at extreme positive displacement of the cylinder. Wake pattern mode behind the surface of the cylinder is 2S mode or 2P mode. Elliptical cylinder outperforms square and circular cylinder in terms of drag and lift characteristics. The range of time-averaged drag coefficient is lowest. Drag and lift increase linearly for all amplitude and frequency ratio in elliptical cylinder compared to square and circular cylinder.