Generation mechanism and aerodynamic characteristic modeling of ground vortex in crosswind condition

Abstract

Numerical investigation of the scaling intake duct has been carried out to analyze the generation mechanisms of ground vortex in crosswind condition and develop a mathematical model for predicting the vortex strength according to the ground vortex aerodynamic characteristic. Combination of different ground clearances and different velocity ratios are considered. Results show that the trailing vortex and ambient vorticity are both the key aspects for the generation of ground vortex in crosswind condition. Ground vortex can be transformed from trailing vortex in crosswind condition even if there is no ambient vorticity which is obviously different from the generation of ground vortex in headwind or quiescent condition. In crosswind condition, ground vortex strength can be intensified by the ambient vorticity. The process of ground vortex formation in crosswind condition can be well illustrated by trailing vortex-ground vortex flow model proposed in this paper. Aerodynamic characteristic of ground vortex show that the vorticity of ground vortex increases to its maximum and then decreases sharply with the increasing of approaching flow velocity which is called aerodynamic self-similarity. Based on this aerodynamic self-similarity, a mathematical model for predicting the ground vortex strength is established and verified. The good agreement between the numerical results and the predicting results shows the accuracy and effectiveness of the mathematical model in some extent.