Numerical Simulation of Hydrodynamics of a Circular Disk Oscillating Near a Seabed

Abstract

This paper studies how the hydrodynamics coefficients of added mass and damping varies when an oscillating disk approaches a seabed. Analysis was performed by OpenFOAM code using the ‘PIMPLE’ algorithm. The simulations considered the flow as laminar and hence no turbulence model was used. Simulations were conducted for a solid disk of 200 mm diameter, 2 mm thick, oscillating at amplitudes varying from 1–48 mm and elevation ‘h’ of the disk from the seabed varying from 0.2–2 times the disk radius. The geometry and parameters used here were the same as that of Wadhwa et al. (2010) [1] and Vu et al. (2008) [2]. The forces on the disk were calculated using a Tool for post-processing force/lift/drag data with function tool available in OpenFOAM. The motions of the disk were restricted to axial (heave) direction. The calculated forces and displacement were analyzed using a Fourier projection to separate the added mass and damping effects. Numerical results were compared with the experiments conducted by Wadhwa et al. (2010) [1] with a sandy bottom. Results show that the added mass and damping increase monotonically with the Keulegan-Carpenter number (KC) up to a critical value, beyond which the behavior becomes random. The critical KC increases linearly with increasing distance from the seabed. The hydrodynamic problem has important applications in structures such as foundation templates and subsea structures oscillating in proximity to the seabed. The computations show vortex lines of the flow, and the influence of the seabed on the flow around the structure.

Hydrodynamic coefficients and pressure loads on heave plates for semi-submersible floating offshore wind turbines: A comparative analysis using large scale models

“…With this ratio and according to the numerical analysis of Ref. [11] the effect of the bottom on the heave plate flow is expected to be negligible.…”

“…Refs. [6,11,19]). The weak dependence with the frequency can be explained by the fact that the depth-radius ratio is quite large, as discussed in section 2.1, which is an indication of a deep water condition operation regime, for which there is no theoretical frequency dependence of hydrodynamic coefficients.…”

Energy harvesting from underwater vibration of an annular ionic polymer metal composite

“…To offer some insight into the effect of fluid damping on the IPMC vibrations, we adapt recent findings in [28] for the oscillations of a rigid solid circular plate in a viscous fluid. Specifically, we estimate the contribution to the loss factor g f from the fluid damping by neglecting the presence of the internal hole in the IPMC and assuming that the IPMC moves rigidly with respect of the quiescent fluid with amplitude jÂðxÞj at the radian frequency x.…”

“…We equate the equivalent structural damping with the damping force in Eqs. (6), (7), and (10) from [28] as follows:…”

Study of the force coefficients on plates using an open source numerical wave tank

“…al, 2007), so that the coefficient C b = (KC)C d /(4) has been used extensively instead in the literature (e.g., Lake et al, 2000;Vu et al, 2004;He et. al, 2007;Tao and Dray, 2008;Wadhwa et al, 2010;Garrido-Mendoza et al, 2013). The expression for C b can be recovered by non-dimensionalizing B with 2 m a for circular disks.…”