LAUSR

Abstract An improved dynamic modelling approach using CFD is proposed to study the underwater motion of a dropped cylinder. Firstly, validation studies on RANS simulated flow past two dimensional (2D) and three dimensional (3D) cylinders (circular and square sectioned) are carried out. The predicted drag coefficients and pressure distribution for 2D and 3D cylinders are both in good agreement with corresponding experiments. URANS simulated results including quantification of mean surface pressure coefficient, fluid velocity and instantaneous drag coefficient and streamlines are compared between 2D circular cylinder, 3D circular cylinder and 3D square prism. Finally, the CFD predicted drag coefficients are applied to study the free falling of a horizontal cylinder under calm water and current respectively. Both 3D effects and cylinder shape effects are studied and found to greatly affect the motion of the cylinder by changing the drag coefficient.