Experimental and Numerical Analysis of the air Flow in T-Shape Channel Flow / Eksperymentalna i numeryczna analiza przepływu powietrza przez skrzyżowanie kanałów w kształcie litery T

2013 ◽  
Vol 58 (2) ◽  
pp. 333-348 ◽  
Author(s):  
Janusz Szmyd ◽  
Marian Branny ◽  
Michal Karch ◽  
Waldemar Wodziak ◽  
Marek Jaszczur ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Air Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Laboratory Model ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Rsm Model ◽  
Calculated Velocity ◽  
Real Flow

This paper presents the results of experimental and numerical investigations of air flow through the crossing of a mining longwall and ventilation gallery. The object investigated consists of airways (headings) arranged in a T-shape. Maintained for technological purposes, the cave is exposed particularly to dangerous accumulations of methane. The laboratory model is a certain simplification of a real longwall and ventilation gallery crossing. Simplifications refer to both the object’s geometry and the air flow conditions. The aim of the research is to evaluate the accuracy with which numerical simulations model the real flow. Stereo Particle Image Velocimetry (SPIV) was used to measure all velocity vector components. Three turbulence models were tested: standard k-ε, k-ε realizable and the Reynolds Stress Model (RSM). The experimental results have been compared against the results of numerical simulations. Good agreement is achieved between all three turbulence model predictions and measurements in the inflow and outflow of the channel. Large differences between the measured and calculated velocity field occur in the cavity zone. Two models, the standard k-ε and k-ε realizable over-predict the measure value of the streamwise components of velocity. This causes the ventilation intensity to be overestimated in this domain. The RSM model underestimates the measure value of streamwise components of velocity and therefore artificially decreases the intensity of ventilation in this zone. The RSM model provides better predictions than the standard k-ε and k-ε realizable in the cavity zone.

scholarly journals The Problem of Airflow Around Building Clusters in Different Configurations

2017 ◽  
Vol 64 (3) ◽  
pp. 401-418 ◽  
Author(s):  
Mateusz Jędrzejewski ◽  
Marta Poćwierz ◽  
Katarzyna Zielonko-Jung
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Pressure Measurement ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Complex Model ◽  
Stress Model ◽  
Qualitative Information ◽  
Pressure Coefficients ◽  
Rsm Model

Abstract In the paper, the authors discuss the construction of a model of an exemplary urban layout. Numerical simulation has been performed by means of a commercial software Fluent using two different turbulence models: the popular k-ε realizable one, and the Reynolds Stress Model (RSM), which is still being developed. The former is a 2-equations model, while the latter – is a RSM model – that consists of 7 equations. The studies have shown that, in this specific case, a more complex model of turbulence is not necessary. The results obtained with this model are not more accurate than the ones obtained using the RKE model. The model, scale 1:400, was tested in a wind tunnel. The pressure measurement near buildings, oil visualization and scour technique were undertaken and described accordingly. Measurements gave the quantitative and qualitative information describing the nature of the flow. Finally, the data were compared with the results of the experiments performed. The pressure coefficients resulting from the experiment were compared with the coefficients obtained from the numerical simulation. At the same time velocity maps and streamlines obtained from the calculations were combined with the results of the oil visualisation and scour technique.

scholarly journals CFD Modeling of Hydrocyclones—A Study of Efficiency of Hydrodynamic Reservoirs

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 118 ◽  
Author(s):  
Marvin Durango-Cogollo ◽  
Jose Garcia-Bravo ◽  
Brittany Newell ◽  
Andres Gonzalez-Mancera
Keyword(s):  
Pressure Drop ◽  
Separation Efficiency ◽  
Collection Efficiency ◽  
Saddle Points ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cfd Modeling ◽  
Eddy Simulation ◽  
Discrete Phase ◽  
Rsm Model

The dynamics of hydrocyclones is complex, because it is a multiphase flow problem that involves interaction between a discrete phase and multiple continuum phases. The performance of hydrocyclones is evaluated by using Computational Fluid Dynamics (CFD), and it is characterized by the pressure drop, split water ratio, and particle collection efficiency. In this paper, a computational model to improve and evaluate hydrocyclone performance is proposed. Four known computational turbulence models (renormalization group (RNG) k- ε , Reynolds stress model (RSM), and large-eddy simulation (LES)) are implemented, and the accuracy of each for predicting the hydrocyclone behavior is assessed. Four hydrocyclone configurations were analyzed using the RSM model. By analyzing the streamlines resulting from those simulations, it was found that the formation of some vortices and saddle points affect the separation efficiency. Furthermore, the effects of inlet width, cone length, and vortex finder diameter were found to be significant. The cut-size diameter was decreased by 33% compared to the Hsieh experimental hydrocyclone. An increase in the pressure drop leads to high values of cut-size and classification sharpness. If the pressure drop increases to twice its original value, the cut-size and the sharpness of classification are reduced to less than 63% and 55% of their initial values, respectively.

Study of Turbulence Models in Flows Through Adverse Pressure Gradient System

2005 ◽  
Author(s):  
E. Karunakaran ◽  
V. Ganesan
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Gradient ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Gradient System ◽  
Field Development

This paper is concerned with the study of performance of popular turbulence models used in the CFD analysis. Turbulence models considered for evaluation include the eddy viscosity models and the Reynolds stress model. The recent k-ε-v2-f model recommended for a flow with separation is also studied. Evaluation of the turbulence models in the present study focuses on a three-dimensional flow field development with adverse pressure gradient and flows that simulate wall-bounded turbulence. Numerical calculations are performed using SIMPLE based algorithm. Nowadays, decelerating flow in a diffuser is assessed by numerical simulations and the validation is done with experimental results. A comparison of the numerical results and the experimental data are presented. The main objective of the comparison is to obtain information on how well the numerical simulations representing the flow field with the standard turbulence models, are able to reproduce the experimental data.

Turbulent Three-Dimensional Air Flow and Heat Transfer in a Cross-Corrugated Triangular Duct

2005 ◽  
Vol 127 (10) ◽  
pp. 1151-1158 ◽  
Author(s):  
Li-Zhi Zhang
Keyword(s):  
Heat Transfer ◽  
Air Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Flat Plates ◽  
Wall Functions ◽  
Mean Values ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Rsm Model

Turbulent complex three-dimensional air flow and heat transfer inside a cross-corrugated triangular duct is numerically investigated. Four turbulence models, the standard k‐ε (SKE), the renormalized group k‐ε, the low Reynolds k‐ω (LKW), and the Reynolds stress models (RSM) are selected, with nonequilibrium wall functions approach (if applicable). The periodic mean values of the friction factor and the wall Nusselt numbers in the hydro and thermally developing entrance region are studied, with the determination of the distribution of time-averaged temperature and velocity profiles in the complex topology. The results are compared with the available experimental Nusselt numbers for cross-corrugated membrane modules. Among the various turbulence models, generally speaking, the RSM model gives the best prediction for 2000⩽Re⩽20,000. However, for 2000⩽Re⩽6000, the LKW model agrees the best with experimental data, while for 6000<Re⩽20,000, the SKE predicts the best. Two correlations are proposed to predict the fully developed periodic mean values of Nusselt numbers and friction factors for Reynolds numbers ranging from 2000 to 20,000. The results are that compared to parallel flat plates, the corrugated ducts could enhance heat transfer by 40 to 60%, but with a 2 times more pressure drop penalty. The velocity, temperature, and turbulence fields in the flow passages are investigated to give some insight into the mechanisms for heat transfer enhancement.

Scaled Room Three-Dimensional Computational Fluid Dynamics Simulations

2002 ◽  
Author(s):  
Steven P. O’Halloran ◽  
Mohammad H. Hosni ◽  
B. Terry Beck ◽  
Thomas P. Gielda
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Working Fluid ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamics Simulations

Computational fluid dynamics (CFD) simulations were used to predict three-dimensional flow within a one-tenth-scale room. The dimensions of the scaled room were 732 × 488 × 274 mm (28.8 × 19.2 × 10.8 in.) and symmetry was utilized so that only half of the room was modeled. Corresponding measurements were made under isothermal conditions and water was used as the working fluid instead of air. The commercially available software Fluent was used to perform the simulations. Two turbulence models were used: the renormalization group (RNG) k-ε model and the Reynolds-stress model. The CFD setup is presented in this paper, along with the velocity and turbulent kinetic energy results. The simulation results are compared to previously obtained three-dimensional particle image velocimetry (PIV) measurements made within the same scaled room under similar conditions.

Comparative Assessment of Turbulence Models for Unsteady Turbulent Flow Predictions in Single Rod Channel Configuration

2007 ◽  
Author(s):  
Kaushik Das ◽  
Debashis Basu ◽  
Scott Painter ◽  
Lane Howard ◽  
Steve Green
Keyword(s):  
Axial Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Experimental Results ◽  
Navier Stokes ◽  
Mean Velocity ◽  
Reynolds Averaged Navier Stokes ◽  
Turbulent Models ◽  
Rsm Model ◽  
Channel Configuration

This paper compares different turbulent models for unsteady flow predictions for axial flow in a single rod channel configuration. The numerical analyses are carried out using the Reynolds Averaged Navier Stokes (RANS) equations and three different turbulent models. The predictions are compared with available experimental results. The three models considered in the present work include the RNG (Renormalization group) k-ε model, the realizable k-ε model, and the Reynolds stress model (RSM). With each model, an unsteady approach commonly referred to as URANS (Unsteady Reynolds Averaged Navier Stokes) solution is used. Predicted results are compared with available experimental results. The predicted time-averaged mean velocity and turbulent stresses are in good agreement with the available experimental results. Flow unsteadiness, which is important for determining heat, momentum, and mass transfer in the gap region, is presented through time histories and spectra of flow and turbulent quantities and their influence on the transportation of fluid across the gap is also explored. The effect of inflow unsteadiness on the solution is explored through comparing the flow field for a constant velocity inlet boundary condition as well as time-varying boundary conditions for the RSM model.

Flow Computations of Rib-Roughened Cooling Channels With RANS and Scale Resolving Simulation Models

2017 ◽  
Author(s):  
İlhan Görgülü ◽  
Ender Hepkaya
Keyword(s):  
Numerical Simulations ◽  
Experimental Studies ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Simulation Models ◽  
Reynolds Stress Model ◽  
Industrial Applications ◽  
Test Case ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

In this research, experimental studies conducted by Casarsa [1] were used as test case to validate flow simulation methods. In the numerical simulations, four RANS turbulence models (k-ε, k-ω, V2-f and Reynolds Stress Model) and a URANS model which are widely used in industrial applications were employed for preliminary analyses. In addition, Scale-Adaptive Simulation (SAS), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES) models are conducted to examine the capabilities of Scale Resolving Simulation (SRS) models. All numerical simulations were performed on two different grid resolutions. Relevance of the grid resolutions to the applied SRS methodologies have been assessed both with crude estimations obtained from the RANS simulations and examination of LES solutions. Findings were presented at various parallel and perpendicular planes with respect to the side walls and different over and inter-rib space locations in the form of mean and root mean square (rms) velocity profiles. In all comparisons, SRS results revealed an inarguable superiority over RANS models as expected. Among the SRS models, SAS model has been considered as the most promising industrial purpose model because of providing similar quality results by allowing higher time steps and coarser grid resolutions.

Adaptation of a Combustion Chamber for Gasified Biomass Combustion: Numerical Simulations

2000 ◽  
Author(s):  
Christophe Duwig ◽  
Jan Fredriksson ◽  
Torsten Fransson
Keyword(s):  
Numerical Simulations ◽  
Conversion Rate ◽  
Combustion Process ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Biomass Combustion ◽  
Ammonia Conversion ◽  
No Emissions

Abstract A gas turbine combustor was modified for addition of Low Heating Value (LHV) gas operation while retaining the original diesel option. New fuel inlets were designed and tested through numerical simulations. CFD calculations have been made in order to investigate the new design combustion abilities. A commercial 3D finite-volume Navier-Stokes solver was used. The Eddy Dissipation model was used to simulate the combustion phenomena and the flow fields were given by using k-ε model, Algebraic Stress Models and Reynolds Stress Model. The comparison between predictions using different turbulence models and grids showed some differences. The required grid for having grid independent results was found too CPU expensive. However, comparisons were done to investigate the influence of the turbulence description on the result. This influence was found significant. It was deduced that the mixing controlled the combustion process. The numerical description of quenching of the flame was found to have more influence on the emission predictions than the description of the reacting zone (swirl). Simulations validated the modified design. Successful combustion operating conditions have been predicted in terms of CO emission. Ammonia conversion to NO was also investigated. The conversion rate was found to be between 65 and 73 %. NO emissions have been predicted, as the maximum temperatures in the combustor were over-predicted, ammonia conversion to NO was also over valued. However, the results show that the combustion process of LHV gas within a small combustor volume is achievable. The swirl was found to be an efficient way to promote the combustion process by improving the mixing. High NO emissions have been predicted. It came from the high conversion rate of fuel ammonia into NO.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

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