Effect of uniform incoming flow on vehicle’s hydrodynamics under the same relative velocity

Abstract

At present, the effect of a uniform stream on the hydrodynamic force or moment under the same relative velocity has been studied mostly in inviscid flow and the results are not consistent. To build the relative motion principle in viscous flow, the relationship of flow fields between the non-stream circumstance and stream circumstance is constructed and the flow field of the steam circumstance is decomposed into the corresponding rest far-field flow and the stream field. Then, hydrodynamic force and moment formulas that are linearly dependent on the distribution of flow field and valid in both viscous and inviscid flow are proposed. Subsequently, the hydrodynamics in the stream circumstances is decomposed according to the flow field decomposition and the uniform stream’s effect is clarified. The correctness of the acquired hydrodynamics transformation formulas is verified by comparing numerical results in both inviscid and viscous flow. At last, the validity of the existing relative motion principle is confirmed or analyzed.