Numerical Simulation of Fluid Flow Past an Oscillating Triangular Cylinder in a Channel

The structure of laminar incompressible flow in a two-dimensional horizontal channel past a triangular cylinder undergoing vertical oscillating motion is simulated using the finite element method. The oscillating motion is carried out for a fixed Reynolds number equal to 100 and dimensionless oscillating amplitudes of 0.125, 0.25, 0.5, and 1, while the dimensionless forced oscillation frequencies are chosen from St/4 to 4 St, where St is the natural Strouhal number of a stationary triangular cylinder. The arbitrary Lagrangian-Eulerian kinematics is utilized to simulate the oscillating motion. The present problem is first solved for a stationary triangular cylinder to obtain the natural Strouhal number. Then, the fluid dynamics for an oscillating triangular cylinder are solved in terms of instantaneous drag and lift, mean of drag, and root mean square (RMS) of lift coefficients. Detailed illustrations of flow streamlines and vortices contours are presented. The results indicate that when the oscillating frequency is equal to the natural Strouhal number of the stationary cylinder, the RMS of lift coefficient reaches its maximum and the oscillating amplitude has no effect at high oscillating frequency.