Developing a Moving Particle Semi-Implicit Fluid-Structure Interaction Solver

The study of the way substances interact is the basis for many fields of science and engineering, e.g., how chemicals interact is the basis for chemical engineering. The fluid-structure interaction is one example of the study of substances interactions in fluid dynamics, but it has always been difficult to model – especially with uncompressed, turbulent flow.

Fluid-structure Interaction

An important area of interest in fluid dynamics, fluid-structure interaction is the interaction between a solid body and a fluid. While there are applications where the solid is considered to be a rigid body, mostly there is some deformation.

Examples of its application include wind power, dam construction, and aircraft development. It is widely used in ocean engineering to solve issues like designing marine vessels to handle wave impacts, and design of ocean/coastal structures while taking into account both wind-induced waves and large storm surge waves. It also has interesting applications in biomedical engineering, such as the design of an artificial heart.

Particle Method Numerical Analysis

The particle method, first developed in 1977, is a numerical analysis method used to simulate complex fluid problems. It breaks a fluid down into individual particles and each particle’s motion is calculated based on how it interacts with other particles. It is extremely useful for complex problems but require extra effort by the programmer and extra computing time – leading to a higher cost.

Within the particle method, there is the moving particle semi-implicit (MPS) method. Developed in 1996, it is a Lagrangian mesh-free method. What this means is there is no mesh connecting each node of the simulation. Rather, the simulation is based on the interactions between the particles. Each particle is assigned physical characteristics like mass, velocity, and acceleration. The particles are then, essentially, set free to interact with each other within the model.

Developing a Fluid-Structure Interaction Solver

In order to develop an accurate and useful fluid-structure interaction solver, researchers in a study published in Applied Ocean Research in 2019 used the solution of continuity and Navier-Stokes equations to develop a model they named “Enhanced Multi-resolution MPS-MPS”. The model was tested using a series of situations: fluid sloshing in a rolling tank, a dam break using an elastic plate, and waves hitting a marine panel.

The study found the model was reasonably accurate and consistent at “reproduction of stress/pressure fields from qualitative/quantitative points of views”. Researchers found that by decreasing the resolution of the fluid in the model, the model was still producing acceptably accurate and stable results while lowering computing costs – a big advantage when using a particle method.

Researchers proposed improvements to the solver like extending it to three dimensions and enhancing the reproduced pressure field. They also expressed that developing dynamic merge/split of particles would expand the applicability of the solver. In addition, non-linear constitutive models should be integrated into the solver to enhance the structure model. The study concluded with, “…detailed investigations on time coupling/integration, e.g. application of higher-order time integration schemes for structure phase, as well as determination of optimum timestep will be conducted in our future studies.”