Investigation of Two- and Three-Dimensional Models of Transitional Flow Past a Square Cylinder

The present study is a comparison of two- and three-dimensional models of flow past a square cylinder at a Reynolds number of 250. The models are computational in nature. The governing equations have been solved by the Marker and Cell (MAC) method with higher order spatial and temporal discretization. Essential differences have been observed in the predictions of the two models. Results reveal that the rms values of the aerodynamic forces in the two-dimensional simulation are higher. These are related to higher stochastic fluctuations near the cylinder surface and a shorter spread of the fluctuating fields. The three-dimensional model shows a longer shear layer and the fluctuations are smaller. An interesting observation of the present study is that the fluctuations are the highest at the points of inflexion in the time-averaged velocity profile. The findings of the present study have been discussed with the help of physical reasoning along with the transport equations of velocity fluctuations.