Experimental Study Of The Hydrodynamic Forces On The Square-section Cylinder

Whenever there is relative motion between a solid body and the fluid in which it is immersed, the body experiences a net force, due to the action of the fluid. The result force can be resolved into components parallel and perpendicular to the direction of flow, the drag and lift forces correspondingly. In the dissertation, the drag and lift forces acting on the square-section cylinder are surveyed in the variable slope flume, and attention is pay to the two followed factors in the drag force.(1) The effect of cylinder shape to the drag force. The total drag acting on a body is comprised of two components--skin-friction drag and pressure drag. Either skin-friction drag or pressure drag may predominate depending on the shape. This dissertation studies the variety relation of the drag and the cylinder shape, and then puts forward the formula for the drag force calculation, considering the effect of shape.(2) The effect of the cylinder's position in water to the drag force. The dissertation has studied the relation between the drag force and the relative position, and the results show that the drag force vertical distribution is similar to the one of velocity. The vertical average velocity is used to calculate the drag force, and the influence of the velocity vertical variety upon the drag force is expressed in the drag coefficient by the relative position parameter, so as to put forward a formula.And then, the formula considering the two parameters together is given. This formula is composed of the parameters of relative position and cylinder shape, therefore, it can be used to calculate the drag forces acting on any size of square-section cylinder at any depth position.