The dynamics of laser-produced plasma plume expansion involves complex interactions between the ablated material and ambient air. This study investigates and compares the performance of three OpenFOAM solvers, namely twoPhaseEulerFoam (tPEF), rhoCentralFoam (rCF), and sonicFoam (sF) using an identical initial setup of geometry and parameters. The primary objective of this study is to affirm the applicability and reliability of the tPEF solver in modeling the laser-produced plasmas for multispecies cases. The focus is on the evaluating the tPEF solver’s ability to simulate plasma plume dynamics under atmospheric air pressure. Propagation of plasma shockwave, mesh generation, initial and boundary conditions, and hydrodynamics of single- and multi-phase equations are analyzed. Critical flow variables, such as pressure, velocity, temperature, and density, were monitored spatially and temporally to evaluate the solver performance. The simulation results demonstrate that tPEF produces stable and reliable results that align with physical expectations and previously published data. It was found to be particularly effective in capturing the plume’s hydrodynamic features, including multi-species behavior and interaction with the ambient environment. The findings affirm applicability of tPEF for modeling laser-induced plasma plumes, especially in capturing complex fluid dynamics and species evolution. This study will provide computational foundations essential for specific engineering applications involving pulsed laser ablation of multi-component materials.

Flow separation in overexpanded single expansion ramp nozzles (SERN) involves complex phenomena, such as shock waves, expansion waves, turbulent boundary layers, and shear layers. Computational fluid dynamics plays a crucial role in studying unsteady flow behaviour in supersonic nozzles, allowing for an investigation into the dynamic flow field characteristics. However, the application of OpenFOAM as a numerical tool for studying SERN in the field of compressible flows, particularly in the overexpansion state where the flow field characteristics are more complex, has received relatively less attention. In this study, the flow field characteristics of an overexpanded SERN under different turbulence models are investigated through a combination of experiments and numerical calculations. The qualitative and quantitative predictive performance of two compressible flow solvers in OpenFOAM, namely, rhoCentralFOAM and sonicFOAM, are compared in terms of flow separation pattern and separation pattern transitions within the overexpanded SERN. The ability of rhoCentralFOAM and sonicFOAM to accurately predict complex flow states is evaluated. Results indicate that the numerical simulations conducted using rhoCentralFOAM and sonicFOAM successfully capture flow separation, separated shock waves, separated bubbles and shear layers for two types of restricted shock separation patterns at the same nozzle pressure ratio (NPR), demonstrating agreement with experimental results. However, sonicFOAM initiates the transition in the separation pattern 0. 0773 NPR earlier than rhoCentralFOAM during the whole separation pattern transition process of the SERN. The transition process in sonicFOAM lasts longer and exhibits a greater variation in NPR. SonicFOAM fails to accurately predict certain aspects, such as the pressure rise after the separation bubble, the reattachment shock wave, and tends to overestimat the length of the separation shock length. Consequently, sonicFOAM cannot be recommended as a suitable solver for accurately capturing the separation pattern of an overexpanded nozzle.

Two Krylov subspace iterative methods, GMRES and QMR, were studied in conjunction with several preconditioning techniques for solving the linear system raised from the finite element discretisation of incompressible Navier-Stokes equations for hydrodynamic problems. The preconditioning methods under investigation were the incomplete factorization methods such as ILU (0) and MILU, the Stokes preconditioner, and the Elman-Silvester block triangular preconditioner. It is observed that the GMRES solver with the Elman-Silvester preconditioner provides faster convergence than the other methods studied here.

We discuss  some potential advantages of the  orthogonal symmetric-diagonal reduction in  two main versions of the Schur-QR method  for symmetric positive definite  generalized eigenvalue problems. We also advise and use the appropriate reductions  as preprocessing on  the solvers, mainly  the Cholesky-QR method, of the  considered  problems. We discuss numerical stability of the  methods via providing upper bound for backward error of the computed eigenpairs and via investigating two kinds of  scaled residual errors. We also propose  and apply  two kinds of symmetrizing  which  improve  the stability and the performance  of the methods. Numerical experiments show that the  implemented versions of the Schur-QR method and the preprocessed versions of the Cholesky-QR  method are  usually more stable than the Cholesky-QR method.

In order to increase the performance of a gas centrifuge used in the uranium enrichment industry, the gas flow field inside it is studied and simulated. In the present work, the full Navier-Stokes equations using the CFD method are used to simulate the gas flow inside the rotor. For the CFD method, a density-based implicit coupling solver was developed in OpenFOAM software, which was used to simulate the gas flow inside the rotor. The separation power was improved in a sample rotor by adjusting feed flow parameters, wall pressure, wall temperature gradient, and scoop drag force. The results show that the process variable had an optimal value in which the separation power is maximum. In order to achieve the maximum separation power of 12. 87 kg UF6 SWU/year, the optimum rotor conditions were determined at a feed rate of 90 g/h, wall pressure of 44 torr, the temperature gradient of 25 K, and drag force of 1557 dyne. This study can be considered an important step in improving the performance of centrifuge separation.

Using OpenFOAM, numerical simulations of two-dimensional flow past a stationary and harmonically pitching wind turbine airfoil at a moderate value of Reynolds number (400000) have been carried out in the current study. Wind turbine blades are subject to different oscillating motions due to unsteady flow around them. Therefore, sinusoidal pitching motion as one of the basic motions in an unsteady oscillation is needed to be thoroughly investigated. This helps to reduce the loads on blades occurring due to dynamic stall phenomenon. The aim of this numerical study is to enhance the accuracy in prediction and analysis of unsteady phenomena around an oscillating NACA 6-series airfoil at near-and post-static stall regions. The experimental data possessed by the presenting authors are considered for validation. In most cases as the results demonstrate, the numerical simulation along with turbulence modelling using k-ω-SST with low-Re correction can accurately capture the physical phenomena related to unsteady pitching motion and hence, highly precise aerodynamic coefficients and pressure coefficients around the airfoil will be obtained at different stall-wise regions.

Culvert is one of the main structures in drainage systems at crossing with railways and roads. Flood flows, along with the transport of sediments and floating debris, can cause blockages and backwater, thereby reducing flood flow capacity. The main purpose of this study was to physically model and numerically simulate the effects of different percentages of blockages on culvert hydraulic characteristics. Blockage effects investigated in 21 laboratory experiments. Complementary tests were carried out with the use of OpenFOAM numerical tool box. Three blockage scenarios have been numerically simulated with 20, 40 and 60 percent coverage of inlet area. The numerical model was calibrated using the experimental data. The simulation results of OpenFOAM in different culvert inlet blockages indicated that the LES turbulent model is more adaptive than RAS models. The main flow characteristics were compared with the corresponding simulation results from the trademark FLOW-3D model, and showed good agreement for verification purpose. Results for different flows (i.e. 40, 60 and 100 percent of the design discharge) showed that the increasing rate of upstream water level is not identical, and is higher for the lower discharges. Blockage also intensifies turbulence and shear stress levels in the outlet section. For design discharge, the 40 percent blockage resulted in the increase of shear stresses up to 10 times, which cause severe scour in downstream channel.