Experimental investigation on key parameters influencing unsteady aerodynamics of a 3:2 rectangular prism in accelerating flow

Abstract

This study investigates the unsteady aerodynamic characteristics of a 3:2 rectangular prism under accelerating flow. Wind tunnel tests were primarily conducted in the steady flow to establish a baseline for assessing the unsteady effects induced by flow acceleration on the aerodynamic forces. Aerodynamic parameters in the time and frequency domains were compared across different accelerating flow cases to analyze the influence of accelerating flow characteristics on the unsteadiness of aerodynamic forces. The results demonstrate that the lift force exhibits more pronounced unsteady characteristics compared to drag and moment. The unsteady behavior is primarily influenced by the wind attack angle, starting wind velocity, and maximum acceleration. For wind attack angles of 0° or 90°, the accelerating flow primarily reduces the amplitude of lift fluctuations. In contrast, for other wind attack angles, the accelerating flow causes a deviation in the time-varying mean of lift from the quasi-steady value, accompanied by an amplification of lift fluctuations. Furthermore, the increase in the starting wind velocity leads to a decrease in the deviation of aerodynamic lifts, indicating that higher starting wind velocities weaken the unsteady aerodynamic characteristics induced by accelerating flow. On the other hand, the increase in flow acceleration enhances the unsteady effect on aerodynamic lift, especially for accelerating flow with higher starting wind velocities. Moreover, the Strouhal number during the accelerating process is lower than that in the steady flow, and the degree of reduction is also influenced by starting wind velocity and maximum acceleration.