Integration Of Spring Physics With The SPH Method For Quasi-Solid To Fluid Interaction Using GPGPU Programming

Turbines used in an unpredictable natural environment can potentially suffer from the impact of surrounding objects or animals. When turbines are placed underwater this problem primarily comes from large flotsam and substantial marine life. In order to consider the implications of this problem on the design of such turbines it is necessary to be able to simulate numerically a quasi-rigid body and its interaction with rigid boundaries whilst it is suspended in fluid. Smoothed Particle Hydrodynamics (SPH) appears well suited to solving this problem, however methods aimed at simulating elastic bodies and those aimed at simulating fluid flows are typically disparate. Combination of the methods therefore requires a methodology to couple them by way of an interface. Alternatively the SPH methods suited to fluid flow simulation could be combined with a particle based method such as a Mass-Spring-Damper (MSD) model to enforce Hookean restrictions on certain particles within an SPH simulation. It is this second possibility which is presented here, where it is shown that the MSD technique neatly combines with a weakly compressible GPGPU (General Purpose Graphics processing Unit) based implementation of the SPH method. Consideration towards the engineering realism of the elastic body represented by the MSD method is given, with a technique to correct a global spring constant and damping coefficient on a per particle basis presented. Simple extension test cases of a two-dimensional elastic square are provided to highlight the effectiveness of the correction method. Results show good correlation to the expected ideal and questions as to the best method to select a global spring constant are also posed and discussed. An illustrative example of the MSD model inter-operating with the SPH method is also provided.