Prediction of Confined Three-Dimensional Impinging Flows With Various Turbulence Models

1992 ◽  
Vol 114 (2) ◽  
pp. 220-230 ◽  
Author(s):  
T. M. Liou ◽  
Y. H. Hwang ◽  
L. Chen
Keyword(s):  
Richardson Number ◽  
Laser Doppler Velocimetry ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Quantitative Agreement ◽  
Computational Effort ◽  
Main Flow ◽  
Inlet Velocity ◽  
Impinging Flows

This paper deals with three-dimensional, turbulent, confined impinging flows. Various turbulence models are examined with reported laser-Doppler velocimetry data and flow-visualization photographs. The turbulence models considered are the k–ε, k–ε with the Richardson number correction for swirling and recirculating flows (k–ε w/scm), algebraic Reynolds stress (k–ε–A), and modified k–kl models. The k–ε and k–ε–A models are found to be superior to the k–ε w/scm and modified k–kl models in predicting the main flow characteristics. The k–ε–A model provides a better quantitative agreement with the experimental data than can be achieved with the k–ε model, however, less computational effort is spent with the k–ε model than with the k–ε–A model. Also, the effect of the inlet velocity profile on the characteristics of the confined impinging flows is addressed in this study.

scholarly journals Numerical and experimental study on turbulence statistics in a large fan-stirred combustion vessel

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
M. E. Morsy ◽  
J. Yang
Keyword(s):  
Isotropic Turbulence ◽  
Burning Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Initial Pressure ◽  
Dynamics Modeling ◽  
Turbulence Statistics ◽  
Experimental Conditions ◽  
Measured Velocity

Abstract Particle image velocimetry (PIV) has become a popular non-intrusive tool for measuring various types of flows. However, when measuring three-dimensional flows with two-dimensional (2D) PIV, there are some uncertainties in the measured velocity field due to out-of-plane motion, which might alter turbulence statistics and distort the overall flow characteristics. In the present study, three different turbulence models are employed and compared. Mean and fluctuating fields obtained by three-dimensional computational fluid dynamics modeling are compared to experimental data. Turbulence statistics such as integral length scale, Taylor microscale, Kolmogorov scale, turbulence kinetic energy, dissipation rate, and velocity correlations are calculated at different experimental conditions (i.e., pressure, temperature, fan speed, etc.). A reasonably isotropic and homogeneous turbulence with large turbulence intensities is achieved in the central region extending to almost 45 mm radius. This radius decreases with increasing the initial pressure. The influence of the third dimension velocity component on the measured characteristics is negligible. This is a result of the axisymmetric features of the flow pattern in the current vessel. The results prove that the present vessel can be conveniently adopted for several turbulent combustion studies including mainly the determination of turbulent burning velocity for gaseous premixed flames in nearly homogeneous isotropic turbulence. Graphic abstract

scholarly journals CFD Modelling of Naturally Ventilated Double Skin Façades: Comparisons among 2D and 3D Models

2021 ◽  
Vol 65 (2-4) ◽  
pp. 330-336
Author(s):  
Camilla Lops ◽  
Nicola Germano ◽  
Sabino Matera ◽  
Valerio D’Alessandro ◽  
Sergio Montelpare
Keyword(s):  
Energy Requirement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
3D Models ◽  
Computational Effort ◽  
Correct Prediction ◽  
Cfd Modelling ◽  
Double Skin ◽  
Cfd Analyses ◽  
Double Skin Facades

Nowadays, Double Skin Façades (DSFs) are popular technologies adopted for both new and existing buildings. Since their introduction, new configurations and materials started to be tested to improve the DSF energy behaviour and function. Such complex technologies, able to improve comfort conditions of occupied spaces and decrease building energy requirement, are strictly related to the design phase that should be carefully evaluated. The correct prediction of air fluxes inside the DSF cavity, in fact, is highly influenced by the adopted analysis hypothesis and settings. Moreover, the absence of multiple experimental campaigns and empirical validations in the sector represents the major concerns for scientists and researchers. Among the possible numerical approaches for studying DSFs, Computational Fluid Dynamics (CFD) analyses confirm to be the most suitable solution. The CFD modelling activity presented in this paper intends to compare various Double Façade configurations by adopting bi- and three-dimensional domains and different turbulence models. According to the obtained results, 2D simulations can predict airflows inside and around the DSF channel with good approximation and reasonable computational effort. Moreover, the velocity profiles estimated by the turbulence formulations are in good accordance, underling only a few slight variations in proximity to the DSF layers.

A Numerical Study of Turbulent Mixed Convection in a Smooth Horizontal Pipe

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Ahmed Faheem ◽  
Gianluca Ranzi ◽  
Francesco Fiorito ◽  
Chengwang Lei
Keyword(s):  
Richardson Number ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Hollow Core ◽  
Horizontal Pipe ◽  
Fully Developed Flow ◽  
Horizontal Pipes ◽  
Dimensionless Velocity ◽  
Hollow Core Slab

This paper presents a numerical study aimed at identifying a suitable turbulence model to describe the fully developed turbulent mixed convention of air in smooth horizontal pipes. The flow characteristics considered here are relevant to those typically observed in ventilated hollow core slab (VHCS) applications and, because of this, the adopted geometry and boundary conditions are represented by the Reynolds number and Richardson number of about 23,000 and 1.04, respectively. Empirical expressions available in the literature are used as reference to evaluate the accuracy of different turbulence models in predicting the dimensionless velocity (u+) and temperature (T+) profiles as well as the Nusselt number (Nu). Among the turbulence models considered, the standard and realizable k-ε models provide the best overall predictions of u+, T+, and Nu in the fully developed flow, and the former is recommended for the modeling of VHCS systems as it gives slightly better estimates of the Nu values.

The Simulation and Optimization on Flow Field in Intake Port of Engine Based on RE and CFD

2014 ◽  
Vol 1079-1080 ◽  
pp. 926-929
Author(s):  
Dan Han ◽  
Qian Wang ◽  
Bing Huan Li ◽  
Guo Jun Zhang ◽  
Shuo Wang
Keyword(s):  
Flow Field ◽  
Laser Scanning ◽  
Gas Flow ◽  
Gasoline Engine ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Intake Port ◽  
Three Dimensional Model ◽  
Simulation And Optimization

Intake port is an important part of the gasoline engine, its structure will influence the gas flow characteristics which directly affects the performance of the engine [1]. In this paper, three-dimensional CFD calculation and structural optimization were used to research the performance of gasoline engine. Firstly, the method of laser scanning and UG software were used to reverse modeling engine exhaust port and get the three-dimensional model. Secondly, after setting boundary conditions and turbulence models, the air flowing through the intake ports were simulated by FLUENT software respectively. Finally, based on numerical methods, the pressure field, velocity field were shown. The results of the simulation of flow field characteristics analysis show that the simulation and experimental results are in good agreement.

Numerical Prediction of a Multistage Centrifugal Pump Performance With Stationary and Moving Mesh

2015 ◽  
Author(s):  
Alessandro Nocente ◽  
Tufan Arslan ◽  
Torbjørn K. Nielsen
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Transient State ◽  
Computational Effort ◽  
Phase Flow ◽  
Two Phase ◽  
Ansys Fluent ◽  
Performance Report

The present work reviews a comparison between calculations of a steady and unsteady three dimensional (3D) flow past the diffuser channels of a centrifugal pump. The commercial software ANSYS Fluent has been used. The considered domain is one of the three stages, since each has exactly the same design. In the first part, simulations are carried out at the best efficiency point (BEP) both steady and transient state, single phase flow and four different turbulence models. Results are compared with the performance report from the manufacturer. In the second part, only the realizable k-ε turbulence model has been taken into account. The simulations have been repeated for different mass flows and the results were again compared with the data from the manufacturer. The comparison performed in the first part shows that integral quantities results are not sensibly influenced by the turbulence model. The comparison at different mass flow shows that the steady state simulations demonstrated to be a good approximation of the transient state, always containing the error within an acceptable limit. The minor computational effort needed makes it attractive to be used for further investigations which will involve two-phase flow studies on the same pump.

CFD Analysis of Flow and Heat Transfer in a Direct Transfer Preswirl System

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Umesh Javiya ◽  
John W. Chew ◽  
Nicholas J. Hills ◽  
Leisheng Zhou ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Quantitative Agreement ◽  
Wall Turbulence ◽  
Direct Transfer ◽  
Cfd Models ◽  
Flow And Heat Transfer

The accuracy of computational fluid dynamics (CFD) for the prediction of flow and heat transfer in a direct transfer preswirl system is assessed through a comparison of CFD results with experimental measurements. Axisymmetric and three-dimensional (3D) sector CFD models are considered. In the 3D sector models, the preswirl nozzles or receiver holes are represented as axisymmetric slots so that steady state solutions can be assumed. A number of commonly used turbulence models are tested in three different CFD codes, which were able to capture all of the significant features of the experiments. A reasonable quantitative agreement with experimental data for static pressure, total pressure, and disk heat transfer is found for the different models, but all models gave results that differ from the experimental data in some respect. The more detailed 3D geometry did not significantly improve the comparison with experiment, which suggests deficiencies in the turbulence modeling, particularly in the complex mixing region near the preswirl nozzle jets. The predicted heat transfer near the receiver holes was also shown to be sensitive to near-wall turbulence modeling. Overall, the results are encouraging for the careful use of CFD in preswirl-system design.

scholarly journals Simulation and Analysis of a Turbulent Flow Around a Three-Dimensional Obstacle

2019 ◽  
Vol 13 (3) ◽  
pp. 173-180
Author(s):  
Lamia Benahmed ◽  
Khaled Aliane
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Governing Equations ◽  
Complex Behaviour ◽  
Ansys Cfx ◽  
Recirculation Zones ◽  
Volume Method ◽  
Calculation Code

Abstract The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The time-averaged results of contours of velocity vectors <V>, cross-stream <v> and stream wise velocity <u> and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.

CFD Analysis of Flow and Heat Transfer in a Direct Transfer Pre-Swirl System

2010 ◽  
Author(s):  
Umesh Javiya ◽  
John Chew ◽  
Nick Hills ◽  
Leisheng Zhou ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Quantitative Agreement ◽  
Turbulence Modelling ◽  
Wall Turbulence ◽  
Direct Transfer ◽  
Cfd Models ◽  
Flow And Heat Transfer

The accuracy of computational fluid dynamics (CFD) for the prediction of flow and heat transfer in a direct transfer pre-swirl system is assessed through a comparison of CFD results with experimental measurements. Axisymmetric and three dimensional (3D) sector CFD models are considered. In the 3D sector models, the pre-swirl nozzles or receiver holes are represented as axisymmetric slots so that steady state solutions can be assumed. A number of commonly used turbulence models are tested in three different CFD codes, which were able to capture all of the significant features of the experiments. Reasonable quantitative agreement with experimental data for static pressure, total pressure and disc heat transfer is found for the different models, but all models gave results which differ from the experimental data in some respect. The more detailed 3D geometry did not significantly improve the comparison with experiment, which suggested deficiencies in the turbulence modelling, particularly in the complex mixing region near the pre-swirl nozzle jets. The predicted heat transfer near the receiver holes was also shown to be sensitive to near-wall turbulence modelling. Overall, the results are encouraging for the careful use of CFD in pre-swirl-system design.

Non-Equilibrium Turbulence Modelling for Compressor Corner Separation Flows

2021 ◽  
Author(s):  
Wei Sun
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Suction Surface ◽  
Physical Reason ◽  
Corner Separation ◽  
Separation Flows ◽  
Non Equilibrium

Abstract Corner separation is one type of the three-dimensional (3D) separated flows which is commonly observed at the junction of the blade suction surface and endwall of an axial compressor. The commonly used Reynolds-Averaged Navier-Stokes (RANS) turbulence models, namely Spalart-Allmaras (SA) and Menter’s Shear Stress Transport (SST) models, have been found to overpredict the size of corner separation. The physical reason is partly attributed to the underestimation of turbulence mixing between the mainstream flow and the endwall boundary-layer flow. This makes the endwall boundary layer unable to withstand the bulk adverse pressure gradients, and in turn leads to its premature separation from the endwall surface during its migration towards the endwall/blade suction surface corner. The endwall flow characteristics within the compressor stator cascade are then studied to facilitate understanding the physical mechanisms that drive the formation of 3D flow structures, and the physical reasons that lead to RANS modelling uncertainties. It is found that the insufficient near-wall boundary layer mixing is partly due to the failure of both SA and SST models to reasonably model the non-equilibrium turbulence behaviors inside the endwall boundary layer, which is caused by the boundary layer skewness. Based on the understanding of the skew-induced turbulence characteristics and its effect on mixing, a detailed effort is presented towards the physical-based modelling of the skew-induced non-equilibrium wall-bounded turbulence. The source terms in the SA and SST models that control mixing are identified and modified, in order to enhance mixing and strengthen the endwall boundary layer. The improved turbulence models are then validated against the compressor corner separation flows under various operating conditions to prove that the location and extent of the corner separation are more realistically predicted.

Numerical Simulation of Turbulent Flows in Centrifugal Compressor Stages With Different Radial Gaps

2007 ◽  
Author(s):  
Pavel E. Smirnov ◽  
Thorsten Hansen ◽  
Florian R. Menter
Keyword(s):  
Numerical Simulation ◽  
Steady State ◽  
Turbulent Flows ◽  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Detailed Comparison ◽  
Operating Point ◽  
Vaned Diffuser

Numerical simulation of three-dimensional flow in a one-stage centrifugal compressor with a diffuser of variable geometry has been performed using the ANSYS CFX 10 code. The computations were conducted using steady and unsteady flow formulations and employing the RANS two-equation turbulence models. Steady-state flow simulations in the compressor were done for two vaned diffuser geometries with different radial gaps. A detailed comparison with the experimental data reported in the literature for different operating points of the “Radiver” test case compressor is presented and discussed. Good agreement of the computed velocity field with the measurements data is obtained at the impeller exit. Downstream of the diffuser vane, prediction quality depends on the operating point. Transient simulations performed for the best operating point of the compressor did not improve considerably predictions of flow characteristics in the diffuser as compared to the steady-state approach.

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