implicit method

Mesh-free particle (Lagrangian) methods، such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH)، are the newest methods in computational fluid dynamics، which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows، using the new method of weakly compressible MPS (WC-MPS). In the MPS method، pressure is determined by solving Poisson equation. This equation is solved implicitly، which needs too much computer time. In the present research، the WC-MPS method is used to calculate pressure. In this method، as in SPH method، the state equation is used. This equation is solved explicitly، which does not occupy too much computer time. To evaluate the proposed method، the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach، dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow، but the accuracy of Lagrangian approach، especially the WC-MPS، is more than Eulerian approach. The proposed methos had some pressure oscillations، which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit methodMesh-free particle (Lagrangian) methods، such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH)، are the newest methods in computational fluid dynamics، which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows، using the new method of weakly compressible MPS (WC-MPS). In the MPS method، pressure is determined by solving Poisson equation. This equation is solved implicitly، which needs too much computer time. In the present research، the WC-MPS method is used to calculate pressure. In this method، as in SPH method، the state equation is used. This equation is solved explicitly، which does not occupy too much computer time. To evaluate the proposed method، the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach، dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow، but the accuracy of Lagrangian approach، especially the WC-MPS، is more than Eulerian approach. The proposed methos had some pressure oscillations، which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit method

Mesh-free particle (Lagrangian) methods, such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH), are the newest methods in computational fluid dynamics, which have been applied in flow problems with large deformations and inconsistency. The aim of this research was to develop and improve the simulation of open-boundary free-surface flows, using the new method of weakly compressible MPS (WC-MPS). Most studies in the field of Lagrangian models are concerned with closed boundary conditions. This study, introduces a comprehensive method for MPS modeling of cases with inflow and outflow boundaries. Inflow and outflow boundaries are considered and the boundary conditions and recycling of particles are prescribed. The algorithm not only improves the inlet and outlet boundary conditions, but also reduces the pressure fluctuations at boundaries. To evaluate the proposed method, the famous applied flow problem of ogee spillway and steady shallow flow over curved bed is analyzed. The program is written in C language and validations are performed for this code. Comparison of the results of proposed model and physical models showed acceptable accuracy in modeling the free surface flows with open boundary conditions.