Generalized Dynamical Model for the Drag Coefficient of Fixed and Moving Cylindrical Bodies

In the current study, we propose a novel reduced-order model for the drag coefficient of a circular cylinder model that can be either fixed or undergoing an oscillatory linear motion in the cross-flow direction, the streamwise direction, or at an arbitrary tilt angle. Thus, the proposed model is not restricted to a single geometric setting of the cylinder. The model establishes a proper nonlinear coupling between the drag coefficient and the lift coefficient, such that the drag coefficient can be restructured using the simple reduced-order model, given the time signal of the lift coefficient. The proposed model is able to capture both the mean component of the drag coefficient, as well as the oscillatory component of it. We derived closed-form expressions to estimate the model parameters from a training dataset. The model was tested and found to be performing satisfactorily under different motion modes. We generated the training data using computational fluid dynamics simulation for a circular cylinder at a low Reynolds number of 300. The computational fluid dynamics solver used was successfully validated by comparison against independent published data. The current study is viewed as a contribution to the fields of nonlinear dynamics, fluid mechanics, and computational mathematics.