Open Source CFD Code Research Articles

Inlet boundary conditions for incompressible LES: A comparative study

In this paper, a comparison between inlet boundary conditions for Large Eddy Simulation is carried out. The geometry considered is the case n. 83 of the Ercoftac database; an incompressible and fully turbulent flow reaches a wall-mounted hump, that is followed by a separation region with recirculation. Three different inflow boundary conditions (fixed velocity profile, plane mapping and synthetic turbulence inlet) have been tested in an open-source CFD code and their influence on mean flow quantities, such as vortex separation and reattachment points, pressure coefficient and turbulence has been analyzed. Results show a satisfying agreement with experiments for the prediction of the mean pressure coefficient and the vortex separation point, despite which, some discrepancies still exist with respect to the channel velocity profiles, vortex size and reattachment point.

Modelling Particulate Removal in Tubular Wet Electrostatic Precipitators Using a Modified Drift Flux Model

Tubular electrostatic precipitators (ESP) have been used in a number of chemical processing industries. The tubular ESPs have many advantages over conventional plate-plate and wire-plate ESPs. The present study is concerned with the numerical modeling of particulate removal in a tubular wet single-stage electrostatic precipitator (wESP). The geometric parameters of a model wESP and the corresponding inlet gas velocities for the wESP are chosen from available experimental data. In addition to the RNG k - ε model for the mean turbulent flow field inside the wESP, the Poisson equation for the electric field, the charge continuity equation and the concentration equation are solved sequentially to obtain a full-fledged solution to the problem under investigation. The proposed drift flux model is implemented in the opensource CFD code OpenFOAM®. The paper discusses the influence of the number of charges acquired by the particles and the corresponding inlet gas velocities on particle concentration distribution within the wESP. Two representative cases with monodispersed particles of 1 μm and 10 μm diameter are considered for the numerical analysis. It is seen from the present analysis that the number of units of charge on particles, the particle size and the inlet gas velocities play a vital role in determining the efficiency of electrostatic precipitation.

외부 유동 해석에 대한 오픈 소스 코드, OpenFOAM의 검증

This paper aims to verify the applicability of OpenFOAM, the widely recognized open source CFD code, to external flows commonly found in aeronautical problems. To this end, several representative flow cases are selected first from subsonic to supersonic flow fields. Then, the computational results obtained from OpenFOAM are systematically compared against available data from experiments and other numerical codes. It was found that the strength and location of shock are well predicted and the effects of boundary conditions on the computed results are reviewed. Subsonic flow with massive separation is selected to validate the prediction capability of OpenFOAM. Based on the current results, the limitation and possibility of OpenFOAM was confirmed and for future study using OpenFOAM was suggested.

Numeric implementation of a nucleation, growth and transport model for helium bubbles in lead–lithium HCLL breeding blanket channels: Theory and code development

Large helium (He) production rates in liquid metal breeding blankets of a DT fusion reactor might have a significant influence in the system design. Low He solubility together with high local concentrations may create the conditions for He cavitation, which would have an impact in the components performance. The paper states that such a possibility is not remote in a helium cooled lithium–lead breeding blanket design. A model based on the Classical Nucleation Theory (CNT) has been developed and implemented in order to have a specific tool able to simulate HCLL systems and identify the key parameters and sensitivities. The nucleation and growth model has been implemented in the open source CFD code OpenFOAM so that transport of dissolved atomic He and nucleated He bubbles can be simulated. At the current level of development it is assumed that void fraction is small enough not to affect either the hydrodynamics or the properties of the liquid metal; thus, bubbles can be represented by means of a passive scalar. He growth and transport has been implemented using the mean radius approach in order to save computational time. Limitations and capabilities of the model are shown by means of zero-dimensional simulation and sensitivity analysis under HCLL breeding unit conditions.

Numerical analysis of flow-induced gas entrainment in roll coating

Gas entrainment by plane liquid jets which plunge into a liquid pool is analyzed by numerical simulations. The numerical model is based on the equations of incompressible newtonian fluids flow. The two-phase flow problem is described with the volume-of-fluid method. The dynamic behaviour of the interface is characterized by two similarity parameters, the capillary number Ca = uη/ σ and the property number Γ = σ( ρ/ η 4 g) 1/3 where u is the velocity, η the dynamic viscosity, σ the interface tension, ρ the density and g the gravitational constant. Numerical simulations are performed with the open source CFD code OpenFOAM. In the simulations the stability of the gas–liquid meniscus is tested for different sets of Ca and Γ. Critical values of Ca which indicate the beginning gas entrainment are deduced from the inspection of the simulation results. The findings of the numerical investigations agree well with corresponding experimental results.

Modeling fine particle dispersion in an inhomogeneous electric field with a modified drift flux model

Dispersion of ultrafine particles (less than 0.1 μm) and accumulation mode particles (0.1–2.5 μm) remains as an area of major concern to microelectronic and semiconductor industry. A possible means of containing the dispersion of particulate pollutants is to subject them to electrostatic precipitation. The present study is concerned with the dispersion of particles in the presence of an inhomogeneous electric field. The widely accepted drift flux model is used to account for the drift flux induced by the inhomogeneous electric field. The mean turbulent flow field for the present analysis is obtained by solving the re-normalization group (RNG) k– ɛ model with the aid of the open source CFD code – Open∇FOAM version 1.5. In addition to the flow field equations, the Poisson equation for the electric field, the charge continuity equation and the particle concentration equation are solved to obtain a complete solution for the present case. A comparison of the concentration field for a particle size of 0.1 μm with and without electric field reveals the impact of electric field on particle concentration distribution. The simulation results are compared with the available experimental data and numerical results.