Rigid-Body Analysis of a Beveled Shape Structure in Regular Waves Using the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) Method

In many cases of wave structure interactions, three-dimensional models are used to demonstrate real-life complex environments in large domain scales. In the seakeeping context, predicting the motion responses in the interaction of a long body resembling a ship structure with regular waves is crucial and can be challenging. In this work, regular waves interacting with a rigid floating structure were simulated using the open-source code based on the weakly compressible smoothed particle hydrodynamics (WCSPH) method, and optimal parameters were suggested for different wave environments. Vertical displacements were computed, and their response amplitude operators (RAOs) were found to be in good agreement with experimental, numerical, and analytical results. Discrepancies of numerical and experimental RAOs tended to increase at low wave frequencies, particularly at amidships and near the bow. In addition, the instantaneous wave contours of the surrounding model were examined to reveal the effects of localized waves along the structure and wave dissipation. The results indicated that the motion response from the WCSPH responds well at the highest frequency range (ω > 5.235 rad/s).

Extraction of New Applicable Dimensionless Relations in the Wedge Impact Problem Using WCSPH Method

Impact problem associated with water entry of a wedge has important applications in various aspects of naval architecture and ocean engineering. In the present study, the 2DOF (2 Degrees of Freedom) wedge impact problem into the water with various wedge deadrise angles and impact velocities is investigated using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. Artificial viscosity and density correction are used to create stability and also to prevent the penetration of fluid particles into the solid boundary. Solving the impact problem is very time-consuming, therefore extracting new mathematical relations can be very useful to calculate some important and applicable parameters in a certain range of wedge angles and impact velocities. In the present research, some new dimensionless applicable relations using the Buckingham π theorem are extracted to investigate important parameters such as acceleration and slamming force in general cases of a wedge impact problem. Then, these mathematical relations are validated by the results obtained from the simulations.

A GPU-Accelerated TLSPH Algorithm for 3D Geometrical Nonlinear Structural Analysis

In this paper, we developed a GPU parallelized Total Lagrangian Formation of Smoothed Particle Hydrodynamics (TLSPH) algorithm for 3D geometrical nonlinear structure analysis. The code was developed using NVDIA CUDA C++. Both the TLSPH and GPU parallelization algorithms are described in detail. Compared to the traditional FEM method for structure analysis, TLSPH method is much easier to be implemented and parallelized. In addition, as a meshless based method, there is no need to mesh the domain for TLSPH method. Also, the computational cost of TLSPH is much lower than the Weakly Compressible Smoothed Particle (WCSPH) method. By introducing GPU acceleration, we have significantly improved the code performance. Two benchmark test cases for 3D geometrical nonlinear structure analysis are carried out. The simulation results are compared with analysis results and the data obtained by Abaqus, which is a popularly-used software for structure analysis based on FEM method. In order to show the efficiency of GPU parallelization, a serial code based on the same TLSPH method is also developed as a reference. Results show GPU parallelization accelerates the code obviously. In summary, the GPU parallelized TLSPH method shows the potential to become an alternative way to deal with 3D geometrical nonlinear structure analysis.

THE HYDRODYNAMIC COEFFICIENTS FOR OSCILLATING 2D RECTANGULAR BOX USING WEAKLY COMPRESSIBLE SMOOTHED PARTICLE HYDRODYNAMICS (WCSPH) METHOD

ABSTRACT: An implementation of the weakly compressible smoothed particle hydrodynamics (WCSPH) method is demonstrated to determine the hydrodynamics coefficients through radiation problem of an oscillating 2D rectangular box. Three possible modes of motion namely swaying, heaving, and rolling are carried out to establish the influence of oscillating motions in predicting the added mass and damping. Both solid boundary and fluid flow are modelled by WCSPH and validated by the potential flow and experimental results. Discrepancies observed at lower frequencies are further investigated using different particle resolutions, different time steps, and extending the domain with longer runtime to demonstrate the performance of WCSPH. Finally, flow separation and vortices are discussed and compared with experimental results. ABSTRAK: Bagi fenomena yang melibatkan radiasi dalam air, segiempat kotak 2D diosilasikan dengan menggunakan simulasi WCSPH untuk memperoleh pekali hidrodinamik. Mod osilasi terbahagi kepada 3 iaitu sway, heave dan roll. Osilasi dengan mengguna pakai kotak akan mempengaruhi pergerakan air dalam menentukan nilai penambahan jisim dan rendaman. Keseluruhan domain air dan sempadan telah dimodelkan dengan menggunakan WCSPH. Semua model tersebut kemudiannya akan dibandingkan melalui keputusan eksperimen dan teori. Jika keputusan melalui kaedah WCSPH ini berbeza, terutama pada frekuensi rendah, penyelidikan lanjut akan dilakukan dengan menggunakan zarah resolusi yang berbeza, langkah masa yang berbeza dan menambah masa domain ujikaji bagi menilai keputusan WCSPH. Akhirnya, kriteria aliran dan kadar pusaran yang terhasil di sekeliling kotak akan dibincang dan dibandingkan bersama keputusan eksperimen.

APPLICATION OF SMOOTHED PARTICLE HYDRODYNAMICS (SPH) IN NEARSHORE MIXING: A COMPARISON TO LABORATORY DATA

A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used to simulate the nearshore flow hydrodynamics. The wave induced dispersion and diffusion are determined for monochromatic waves with significant wave height of 0.12 m and the wave period of 1.2 sec (Sop=5%) based on WCSPH wave dynamics. The hydrodynamics of WCSPH model are compared to the laboratory results obtained from series of LDA measurements. The overall mixing coefficients across the nearshore are determined from WCSPH hydrodynamics. The mixing coefficients obtained are compared with the values determined from a series of fluorometric studies performed in a large-scale facility in DHI, Denmark. The results show that the wave profiles are in good agreement with the experimental data. The WCSPH model is proven to be well capable of estimating the dispersion across the nearshore.

A MODIFIED WAVEMAKER BOUNDARY CONDITION FOR A NUMERICAL WAVE TANK BASED ON THE WCSPH METHOD

In this paper a space-averaged Navier–Stokes approach was deployed to Modified Wavemaker Boundary condition for a numerical wave tank. The developed model is based on the smoothed particle hydrodynamic (SPH) method which is a pure Lagrangian approach and can handle large deformations of the free surface with high accuracy. In this study, the large eddy simulation (LES) turbulent model was coupled with the weakly compressible version of the smoothed particle hydrodynamics (WCSPH) method to Modified Wavemaker Boundary condition for a numerical wave tank. An absorbing wavemaker boundary condition was developed to absorb the second reflecting waves from the wavemaker. The capacity of absorbing secondary reflecting waves and incoming waves in absorbing wavemaker was validated through comparisons of the numerical results with general wavemaker.

Lagrangian simulation and analysis of the power-law fluid mixing in the two-blade circular mixers using a modified WCSPH method

In the present study, we introduce a robust modified Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method in order to examine miscible mixing within a two-blade paddle mixer. Since it has a Lagrangian nature and it is based on particles, Smoothed Particle Hydrodynamics (SPH) is an appropriate and convenient method for simulating the moving boundary problems and tracking the particles in the mixing process. The present study thus introduces a convenient SPH method for modelling the mixing process for the power-law fluids. Two geometries for the mixer are examined and the effects of the power-law index on the fluid mixing are investigated. The results show that the geometric change from circular chamber to twin chamber considerably increases the mixing rate (by at least 49%). The results also indicate that the twin chamber mixer is more efficient for the fluids with higher power-law index.