Lift and drag evaluation in translating and rotating non-inertial systems

In this paper relationships have been derived for lift and drag coefficients for cylindrical bodies for two cases. The relative motion between the body and the fluid is assumed to be two-dimensional and to take place in a plane perpendicular to the axis of the body. Three-dimensional effects are ignored, thus limiting the validity of the formulae to low Reynolds number flows. The fluid is assumed to be an incompressible constantproperty Newtonian fluid. In the first case, an inertial system is fixed to a stationary cylindrical body. The motion of the fluid in which the body is placed is an arbitrary function of time not identically zero, e.g. the fluid can have linear and angular acceleration, such as translation, oscillation or rotation. The velocity of the fluid at a single instant is either uniform in space or, in the case of rotation, a linear function of distance from the origin of the system. In the second case, a noninertial system is fixed to an accelerating cylindrical body. The relative flow between fluid and body is kinematically the same as in the first case, but the forces acting upon the bodies differ in the two systems. This is due to the inertial forces that occur in a noninertial system. General formulae are derived for a cylindrical body of arbitrary cross-section and give the relationships between the two systems for each set of coefficients, i.e. the relationship between the lift coefficients for each case, and the same for the drag coefficient. As an example, the relationships are applied to two common cases, a circular and a rectangular cross-section cylinder. r 2004 Elsevier Ltd. All rights reserved.