Experimental Investigation on Quasi-Steady and Unsteady Self-Excited Aerodynamic Forces on Cable and Rivulet

Abstract

The aerodynamic forces on the cable and rivulet are usually determined by the quasi-steady method, which cannot take signature turbulence into account. Furthermore, the oscillation of the cable and rivulet might have significant effects on the aerodynamic forces. In this study, a series of wind tunnel tests were carried out to measure the wind pressures on a cable-rivulet test model, which can keep static and moving statuses utilizing a forced vibration system developed at Hunan University. Wind pressures measured on the test model surface were then used to integrate the drag and lift forces of the cable and rivulet. The results show that vertical vibration of the test model has little effect on the pressure distribution on the cable and rivulet and the mean wind pressures are not very sensitive to the vibration of test model. On the other hand, the oscillation of the rivulet on the cable surface seems to significantly amplify the fluctuating pressures. A sudden decrease of the lift coefficient was observed when the rivulet position is close to 60°, which indicates that classical galloping could be evoked. Eight aerodynamic derivatives of the cable and the rivulet were also identified based on the experimental data, and these aerodynamic derivatives can be further used to determine the unsteady self-excited aerodynamic forces on the cable and rivulet. Overall, this study shows that compared with the quasi-steady aerodynamic forces, the unsteady self-excited aerodynamic forces are more consistent with the exact values.