Numerical investigation of anguilliform locomotion by the SPH method

Purpose This paper aims to introduce a numerical investigation of aquatic locomotion using the smoothed particle hydrodynamics (SPH) method. Design/methodology/approach To model this problem, a simple improved SPH algorithm is presented that can handle complex geometries using updatable dummy particles. The computational code is validated by solving the flow over a two-dimensional cylinder and comparing its drag coefficient for two different Reynolds numbers with those in the literature. Findings Additionally, the drag coefficient and vortices created behind the aquatic swimmer are quantitatively and qualitatively compared with available credential data. Afterward, the flow over an aquatic swimmer is simulated for a wide range of Reynolds and Strouhal numbers, as well as for the amplitude envelope. Moreover, comprehensive discussions on drag coefficient and vorticity patterns behind the aquatic are made. Originality/value It is found that by increasing both Reynolds and Strouhal numbers separately, the anguilliform motion approaches the self-propulsion condition; however, the vortices show different pattern with these increments.

Moving particle semi-implicit method with improved pressures stability properties

Moving particle semi-implicit (MPS) method is one of the Lagrangian methods widely used in engineering issues. This method, however, suffers from unphysical oscillations in its original form. In the present study, a modified incompressible MPS method is proposed to suppress these oscillations and is used for simulating free surface problems. To demonstrate the stability of the presented method, different kernel functions are used in the case of numerical dam break modeling as a benchmark simulation. A simple form of definition of curved wall boundaries is suggested which eliminates dummy particles and subsequently saves CPU time. Flow over an ogee spillway is simulated for the first time with the I-MPS method and as a new test case which has several curved lines in its geometry. The comparisons between theoretical solutions/experimental data and simulation results in terms of free surface and pressure show the accuracy of the method.

A Contact SPH Method with High-Order Limiters for Simulation of Inviscid Compressible Flows

In this paper, we study a class of contact smoothed particle hydrodynamics (SPH) by introducing Riemann solvers and using high-order limiters. In particular, a promising concept of WENO interpolation as limiter is presented in the reconstruction process. The physical values relating interactional particles used as the initial values of the Riemann problem can be reconstructed by the Taylor series expansion. The contact solvers of the Riemann problem at contact points are incorporated in SPH approximations. In order to keep the fluid density at the wall rows to be consistent with that of the inner fluid wall boundaries, several lines of dummy particles are placed outside of the solid walls, which are assigned according to the initial configuration. At last, the method is applied to compressible flows with sharp discontinuities such as the collision of two strong shocks and the interaction of two blast waves and so on. The numerical results indicate that the method is capable of handling sharp discontinuity and efficiently reducing unphysical oscillations.

Numerical Simulation on Forced Revolving Moving Boundary Problem Using Incompressible SPH (ISPH)

One forced revolving moving boundary problem model was constructed and simulated by incompressible SPH (ISPH). The dummy particles are used to deal the moving boundary. The tensile instability is avoided by setting a reference pressure. Compared with the results produced by FLUENT, the method was proved to be more practical and effective. The method is applicable to the more complex 3D model.