Vortex-induced Resonance Research Articles

On the Control of Instabilities in Fluid-Structure Interaction Problems

Energy dissipation due to sloshing liquid in torus-shaped nutation dampers is studied using the simple potential flow procedure in conjunction with the first order boundary layer correction. This is followed by an extensive test program to assess effectiveness of the dampers in arresting relatively low frequency oscillations frequently encountered in industrial aerodynamics problems. results suggest damping characteristics to be particularly sensitive to physical properties of the liquid used, its height in the torus, damper geometry, and dynamical parameters representing amplitude and frequency. Tests on two and three dimensional structural models in smooth flow and boundary layer wind tunnels, with the models undergoing vortex-induced resonance and galloping instability, suggest that nutation dampers can effectively suppress both forms of instabilities over a wide range of wind speed. The concept is likely to prove effective in tackling industrial aerodynamics, earthquake and ocean engineering problems

Suppression of wind-induced instabilities using nutation dampers

This paper presents the results of experiments conducted to assess the effectiveness of circular ring-type nutation dampers partially filled with liquid. In the beginning, important system parameters are defined and their effect on the damping coefficient established using a simple static stand facility. This is followed by tests on two- and three-dimensional models, in smooth flow and boundary layer tunnels, with the models undergoing vortex-induced resonance and galloping conditions. Results suggest that nutation dampers can effectively suppress both forms of instabilities over a wide range of wind velocity.

Movi-ng-Surface Boundary-Layer Control for Aircraft Operation at High Incidence

The paper studies effectiveness of the moving-surface boundary-layer control on a NACA 63-218 (modified) two-dimensional wing used in the Canadair CL-84, a twin-propeller V/STOL design. Tests with rotating cylinder(s) at the leading edge of the airfoil and/or of the flap show the former to have a significant effect on the maximum lift, stall characteristics, and lift/drag ratio. On the other hand, the advantage gained by the presence of the rear cylinder is relatively small for the slotted flap configuration. The availability of a high value of lift suggests the approach velocity with this form of boundary-layer control is likely to be limited only by the lateraldirectional stability characteristics. The concept presents several possible applications including a mechanism for delaying the vortex-induced resonance of bluff bodies.