Sensitivity Analysis of Weakly Compressible Moving Particle Semi-Implicit Method in a Dam-Break Flow Simulation

Lagrangian approaches such as the Moving Particle Semi-Implicit method and Smoothed particle Hydrodynamics are the latest techniques in Computational Fluids Dynamics and have attracted the attention of many researchers. Due to the Lagrangian nature of such practices, they can simulate various problems with large deformations and a variety of boundary conditions which has led to their application in many complex engineering problems. Therefore, the accuracy of the results obtained using these methods is substantial, while various parameters affect the accuracy of the simulation. In this paper, the sensitivity of a dam-break flow simulated by the Weakly Compressible Moving Particle Semi-Implicit method associated with the particle size and Courant number is analyzed. The analysis is performed in two circumstances. First, the Courant number is fixed, and the sensitivity relative to particle size is investigated. Then, sensitivity relative to the Courant number is studied in fixed particle size. In general, it can be concluded that the smaller the particle size and Courant number, the higher accuracy and computational cost

Bingham fluid simulations using a physically consistent particle method

The Bingham fluid simulation model was constructed and validated using a physically consistent particle method, i.e., the Moving Particle Hydrodynamics (MPH) method. When a discrete particle system satisfies the fundamental laws of physics, the method is asserted as physically consistent. Since Bingham fluids sometimes show solid-like behaviors, linear and angular momentum conservation is especially important. These features are naturally satisfied in the MPH method. To model the Bingham feature, the viscosity of the fluid was varied to express the stress-strain rate relation. Since the solid-like part, where the stress does not exceed the yield stress, was modeled with very large viscosity, the implicit velocity calculation was introduced so as to avoid the restriction of the time step width with respect to the diffusion number. As a result, the present model could express the stopping and solid-like behaviors, which are characteristics of Bingham fluids. The proposed method was verified and validated, and its capability was demonstrated through calculations of the two-dimensional Poiseuille flow of a Bingham plastic fluid and the three-dimensional dam-break flow of a Bingham pseudoplastic fluid by comparing those computed results to theory and experiment

SPH simulation of floating structures with moorings

The open-source code DualSPHysics is applied to simulate the interaction of sea waves with floating offshore structures, which are typically moored to the seabed, such as vessels, boats, floating breakwaters and wave energy converters (WECs). The goal is to develop a numerical tool that allows the study of the survivability of floating moored devices under highly energetic sea states, obtaining the optimum mooring layout to increase lifetime. The moorings are modelled by coupling DualSPHysics with MoorDyn, a lumped-mass mooring dynamics model. MoorDyn represents mooring line behaviour subject to axial elasticity, hydrodynamic forces in quiescent water, and vertical contact forces with the seabed. Calculated mooring tensions at the fairlead are added as external forces in order to compute the resulting response and motions of the floating structures in DualSPHysics. The coupled model has been validated against data from scale model tests generated during the experimental campaigns for the European MaRINET2 EsflOWC project. In order to evaluate the accuracy of the coupling implementation with the lumped-mass mooring model, free-surface elevation, motions of the floater and mooring tensions are numerically computed and compared to experimental data. Overall, the results demonstrate the accuracy of the coupling between DualSPHysics and MoorDyn to simulate the motion of a moored floating structure under the action of regular waves. Going forward, this modelling approach can be employed to simulate more complex floating structures such as floating wind turbines, buoys, WECs, offshore platforms, etc

Fluid-elastic structure interaction simulation by using ordinary state-based peridynamics and peridynamic differential operator

The fluid-structure interaction phenomenon is often encountered in the ocean engineering field. In the present work, a non-local numerical model is developed for the simulations of weakly compressible viscous fluid and elastic structure interactions. The peridynamic theory is adopted for both the structure and fluid modelling. The elastic structure is described by using the ordinary state-based peridynamics, while the fluid is modelled by utilizing the peridynamic differential operator. Furthermore, the updated Lagrangian description is adopted for the fluid including the relative deformation gradient expressed by the peridynamic differential operator. The fluid-structure interface and its normal direction are calculated via the gradient of a colour function, which varies with the fluid motion and structure deformation. Besides, the interaction force exerted from fluid to structure is constrained to be always perpendicular to the moving interface. Hence the fluid motion and structural deformation are predicted simultaneously. The validation of the developed model is conducted through the simulation of a water dam break with a rubber gate. The good agreement between the peridynamic and the experiment results demonstrates the capability of the current model for solving fluid-elastic structure interaction problems

DualSPHysics modelling to analyse the response of Tetrapods against solitary wave

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe stability of Tetrapod armour units against solitary waves using Smoothed Particle Hydrodynamics (SPH) method is analysed in this work. To this purpose, the SPH-based DualSPHysics code was coupled with the multiphysics library Project Chrono. Tetrapod units are placed above a submerged mound. DualSPHysics solves the fluid-solid interaction, while Project Chrono solves the Tetrapod-mound interactions based on the contact and material properties of the block surface. The motion of the units during the simulation was compared with the physical model experiments where Tetrapods are made of mortar, and the mound is in PVC. The numerical results expressed as displacements of Tetrapods and damage ratio under different solitary waves are in reasonable agreement with the experiments, proving the capability of the DualSPHysics code to simulate challenging environments under the same numerical framework. The validated tool is then applied to study the stability for different coefficients of friction between mound and Tetrapods aiming at simulating the effects of different materials and surface roughness.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Ministerio de Ciencia e Innovación | Ref. TED2021-129479A-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/ 33

3D ISPH Erosion Model for Flow Passing a Vertical Cylinder

In this paper a 3D incompressible Smoothed Particle Hydrodynamics (ISPH) erosion model is proposed to simulate the scouring process behind a large vertical cylinder. The erosion model is based on the turbidity water particle concept and the sediment motion is initiated when the fluid bottom shear stress exceeds the critical value. The previous 2D SPH sediment initiation model is expanded by combining the effects of both transverse and longitudinal sloping beds in a practical 3D situation. To validate the developed model, a laboratory flume experiment was carried out to study the clear water scouring around a vertical cylinder under unidirectional current, in which high-speed video cameras were used for the real-time monitoring of sediment movement. The 3D ISPH results are compared with the experimental data with good agreement in terms of the scouring patterns and scales. Besides, the computed flow velocity field suggests that both the horseshoe vortices and lee-wake flows around the cylinder have been accurately simulated

SPH based numerical treatment of the interfacial interaction of flow with porous media

In this paper, the macroscopic equations of mass and momentum are developed and discretised based on the Smoothed Particle Hydrodynamics (SPH) formulation for the interaction at an interface of flow with porous media. The theoretical background of flow through porous media is investigated in order to highlight the key constraints which should be satisfied, particularly at the interface between the porous media flow and the overlying free flow. The study aims to investigate the derivation of the porous flow equations, computation of the porosity, and treatment of the interfacial boundary layer. It addresses weak assumptions that are commonly adopted for interfacial flow simulation in particle‐based methods. As support to the theoretical analysis, a 2D weakly compressible SPH (WCSPH) model is developed based on the proposed interfacial treatment. The equations in this model are written in terms of the intrinsic averages and in the Lagrangian form. The effect of particle volume change due to the spatial change of porosity is taken into account and the extra stress terms in the momentum equation are approximated by using Ergun's equation and the Sub‐Particle Scale (SPS) model to represent the drag and turbulence effects, respectively. Four benchmark test cases covering a range of flow scenarios are simulated to examine the influence of the porous boundary on the internal, interface and external flow. The capacity of the modified SPH model to predict velocity distributions and water surface behaviour is fully examined with a focus on the flow conditions at the interfacial boundary between the overlying free flow and the underlying porous media