Flow Induced Vibration of Large Deflection Filament in Viscous Flow

Abstract

This work presents a numerical simulation of fluid-structure interaction of a highly flexible filament in a flow. A finite element model of nonlinear/large deflection cantilever beam is developed to represent the filament. The flow of Newtonian fluid is considered laminar and two-dimensional. The coupling of fluid-structure is carried out by using the fictitious domain algorithm where the moving boundary conditions are imposed. A no-slip condition is applied to all boundary conditions included on the surface of the moving filament. The structural response is calculated at one time step behind the solution of the Navier-Stokes equations. The additional mass plays an important role in dynamic response especially when the density ratio between the fluid and the filament becomes considerably high. To prevent the numerical instability, the equation of motion needs to be represented in a non-dimensional form by keeping the similarities of flow and dynamic response. A ramp function model is applied to simulate the gradual growth of fluid dynamic loads. In the structural part, a Crank-Nicholson integration algorithm is used in calculating the simultaneous structural response. The validation of the method was carried out through the existing experimental results for low density ratio of flowing fluid and filament material in wind-tunnel test, and for high density ratio in flowing soap test as well.