A New Implicit Numerical Treatment for Non-Linear Turbulence Models and Its Application to Channels With Spatially Periodic Corrugated Walls

2002 ◽  
Author(s):  
Marcelo Assato ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Control Volume ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Numerical Treatment ◽  
Linear Diffusion ◽  
Viscosity Models ◽  
Non Linear ◽  
Diverging Channel ◽  
Spatially Periodic ◽  
Volume Method

This work examines the performance of linear and nonlinear eddy-viscosity models when used to predict the turbulent flow in periodically sinusoidal-wave channels. Two geometries are investigated, namely a converging-diverging channel and a channel with concave-convex walls. The numerical method employed for the discretization of the equations is the control-volume method in a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm is used for correcting the pressure field. The classical wall function and a low Reynolds model are used to describe the flow near the wall. Comparisons between those two approaches using linear and non-linear turbulence models are done. Here, an implicit numerical treatment was proposed for the non-linear diffusion terms of the momentum equations in order to increase the robustness of the solution method.

Turbulent Flow and Heat Transfer in a Porous Chamber

2003 ◽  
Author(s):  
Marcelo Assato ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Turbulent Flow ◽  
Control Volume ◽  
Numerical Technique ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Macroscopic Models ◽  
Flow And Heat Transfer ◽  
Non Linear ◽  
Porosity And Permeability ◽  
Volume Method

This work presents a numerical investigation of turbulent flow past a porous structure in a channel using linear and non-linear eddy viscosity macroscopic models. Parameters such as porosity and permeability of the porous material are varied in order to analyze their effects on the flow pattern, particularly on the damping of the recirculating bubble after the entrance and exit regions. The numerical technique employed for discretizing the governing equations is the control-volume method. The SIMPLE algorithm is used to correct the pressure field. The classical wall function is utilized in order to handle flow calculation near the wall. A discussion on the use of this technique for simulating the flow in question is presented. Comparisons of results simulated with both linear and non-linear turbulence models are shown.

Simulation of Axial Flow in a Bare Rod Bundle Using a Non-Linear Turbulence Model With High and Low Reynolds Approximations

2002 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Marcelo Assato
Keyword(s):  
Control Volume ◽  
Numerical Technique ◽  
Axial Flow ◽  
Simple Algorithm ◽  
Eddy Viscosity Model ◽  
Rod Bundle ◽  
Non Linear ◽  
Fully Developed Turbulent Flow ◽  
Low Reynolds ◽  
Volume Method

This work presents a numerical investigation of fully developed turbulent flow in a triangular sub-channel of a bare rod bundle using a Non-Linear Eddy Viscosity Model (NLEVM). The numerical technique employed for discretizing the governing equations is the control-volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to correct the pressure field. The classical wall function and a low Reynolds model were used in order to handle flow calculations near the wall. In this work, the influence of constants of calibration existing in the non-linear terms of the model is analyzed.

Influence of Micro Trapezoidal-Groove on Behavior of Sliding Tribopairs

2010 ◽  
Vol 37-38 ◽  
pp. 544-549 ◽  
Author(s):  
Pei Yun Zhang ◽  
Yan Hu Zhang ◽  
Xiao Li Wang ◽  
Xi Jun Hua ◽  
Yong Hong Fu
Keyword(s):  
Hydrodynamic Lubrication ◽  
Control Volume ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Tribological Performance ◽  
Control Volume Method ◽  
Supporting Capacity ◽  
Continuity Equations ◽  
Isosceles Trapezoid ◽  
Volume Method

The effect of various micro isosceles-trapezoid grooves on improvement of tribological performance is discussed. It is accomplished through the CFD-approach where the momentum and continuity equations are solved separately, one of low Reynolds turbulence models-Abid index and SIMPLE algorithm in theory of Control Volume Method are adopted. For different width and depth of micro isosceles-trapezoid grooves, the load supporting capacity of oil-film are compared. The results show that the widths has more influence than the depths on hydrodynamic lubrication, and relative parameters change monotonously with the depth of micro-groove. The effect of texturing arc-grooves on improvement of tribological properties is conspicuous if w1= 40μm, w2= 10μm and hp= 10μm for micro isosceles-trapezoid grooves.

A Thermo-Mechanical Model for a Counterflow Biomass Gasifier

2014 ◽  
Vol 354 ◽  
pp. 227-235
Author(s):  
Marcelo J.S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermal Capacity ◽  
Macroscopic Model ◽  
Algebraic Equations ◽  
Medium Permeability ◽  
Mechanical Approach ◽  
Volume Method

This article presents a thermo-mechanical approach to investigate heat transfer between solid and fluid phases in a model gasifier. A two-temperature equation approach is applied in addition to a macroscopic model for laminar flow through a porous moving bed. Transport equations are discretized using the control-volume method and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effects on inter-phase heat transfer due to variation of medium permeability, thermal conductivity and thermal capacity are analyzed. Results indicate that for smaller medium permeabilities, as well as for higher solid-to-fluid thermal capacity and thermal conductivity ratios, enhancement of heat transfer between phases is observed.

Numerical Simulation of Laminar Confined Impinging Jet in a Composite Channel

2008 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Layer ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Local Distribution ◽  
Governing Equations ◽  
Stagnation Region ◽  
Volume Method ◽  
Material Porosity ◽  
Macroscopic Equations

This work shows numerical results for a jet impinging onto a flat plane covered with a layer of a porous material. Porosity of the porous layer is varied in order to analyze its effect on the local distribution of Nu. Macroscopic equations for mass and momentum ae obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that inclusion of a porous layer decreases the peak in Nu avoiding excessive heating or cooling near the stagnation region.

Free convective of a linear heterogeneous liquid in a square cavity at side heating

2020 ◽  
pp. 108-116
Author(s):  
K.V. Moiseev ◽  
◽  
V.S. Kuleshov ◽  
R.N. Bakhtizin ◽  
◽  
...  
Keyword(s):  
Control Volume ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Double Diffusion ◽  
Boussinesq Approximation ◽  
Square Cavity ◽  
Cell Height ◽  
Volume Method ◽  
Dimensional Statement ◽  
Stratified Liquid

In this work the problem of free convection of the Newtonian poorly stratified liquid in the cell warmed up from left and cooled from right with the heat-insulated horizontal boarders is presented. Liquid with small concentration of salt and initial linear stratification on cell height is considered. The model of double diffusion in a Boussinesq approximation is applied to model the process. The problem is solved both in two - and three-dimensional statement by means of a control volume method and a SIMPLE algorithm. It is shown that vortex structures at the layered mode of convection have quasi-two-dimensional character.

Predictive Techniques for Turbulent Oscillatory Flows

1999 ◽  
Author(s):  
P. G. Tucker
Keyword(s):  
Eddy Viscosity ◽  
Oscillatory Flow ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Intensity Measurements ◽  
Viscosity Models ◽  
Non Linear ◽  
Models Comparison ◽  
Normal Wall ◽  
Zonal Models

Abstract The prediction of turbulent oscillatory flow at around transitional Reynolds numbers is considered for an idealized electronics system. To assess the accuracy of turbulence models, comparison is made with measurements. A stochastic procedure is used to recover instantaneous velocity time traces from predictions. This procedure enables more direct comparison with turbulence intensity measurements which have not been filtered to remove the oscillatory flow component. Normal wall distances, required in some turbulence models, are evaluated using a modified Poisson equation based technique. A range of zero, one and two equation turbulence models are tested, including zonal and a non-linear eddy viscosity models. The non-linear and zonal models showed potential for accuracy improvements.

Turbulent Free Convection in a Composite Enclosure

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Viviani T. Magro
Keyword(s):  
Thermal Field ◽  
Control Volume ◽  
Simple Algorithm ◽  
Flow Region ◽  
Porous Matrix ◽  
Porous Substrate ◽  
Local Flow ◽  
Vertical Walls ◽  
Energy Equations ◽  
Volume Method

This paper deals with the problem of heat transfer in square cavities partially filled with porous material. Local flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with the SIMPLE algorithm. Enhancement of convective currents within the porous substrate is detected as the Rayleigh number increases. Thin boundary layers along the cavity vertical walls and stratification of the thermal field are observed for Ra > 109.

scholarly journals Stirred tank simulation using Partially-Averaged Navier-Stokes $$k_u-\epsilon _u$$ turbulence model

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Srimanta Maji ◽  
Akshaya K. Sahu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Power Law ◽  
Control Volume ◽  
Axial Flow ◽  
Simple Algorithm ◽  
Stirred Tank ◽  
Navier Stokes ◽  
Flow Variables ◽  
Volume Method

AbstractIn the present study, simulation of a stirred tank using axial flow impeller has been studied numerically to see the behaviour of flow variables in the entire vessel. It is assumed that the flow is steady state, two dimensional, incompressible and axisymmetric. For simulation, Partially-Averaged Navier-Stokes (PANS) $$k_u-\epsilon _u$$ k u - ϵ u turbulence model has been taken into account. For discretization, control volume method along with upwind and power-law schemes have been taken. The solutions are obtained by using the SIMPLE algorithm. The boundary conditions for impeller are given by using the experimental data. The main objective is to investigate the influence of different filters width $$f_k$$ f k of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model parameter on the characteristic flow variables. The predicted results of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model for different $$f_k$$ f k have been compared with the experimental data at different axial levels of the stirred tank. It has been observed that the power-law scheme gives better agreement with the experimental data. Further, near the impeller region, PANS predicted results are better for smaller $$f_k$$ f k . Also, Reynolds-Averaged Navier-Stokes Shear Stress Transport (SST) $$k-\omega $$ k - ω turbulence model has been tested for comparative study.

Numerical and Experimental Investigation of the Melt Casting of Explosives

2004 ◽  
Author(s):  
Dawei Sun ◽  
Suresh V. Garimella ◽  
Sanjeev Singh ◽  
Neelam Naik
Keyword(s):  
Numerical Model ◽  
Energetic Materials ◽  
Control Volume ◽  
Simple Algorithm ◽  
Solidification Process ◽  
High Viscosity ◽  
Stress Distributions ◽  
Flow Heat ◽  
Volume Method ◽  
The Impact

Melt casting of energetic materials is investigated, and a numerical model formulated for the analysis of the coupled fluid flow, heat transfer, and stress fields involved in this phase-change process. The numerical model is based on a conservative multi-block control volume method. The SIMPLE algorithm is employed along with an enthalpy method approach to model the solidification process. Results from the model are verified against experimental data as well as published numerical results for simplified cases. In the melt casting of RDX-binder mixtures, the very high viscosity of the melt leads to the influence of melt convection being very limited. The impact of different cooling conditions on the velocity, temperature and stress distributions, as well as on the solidification time, are discussed. The model can be used to improve the quality of cast explosives, by optimizing and controlling the processing conditions.

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