scholarly journals Numerical simulation of different turbulence models aiming at perdicting the flow and temperature separation in a Ranque-Hilsch vortex tube

2014 ◽  
Vol 18 (4) ◽  
pp. 1159-1171
Author(s):  
Hossein Azizi ◽  
Reza Saleh ◽  
Mohsen Kahrom ◽  
Reza Andalibi
Keyword(s):  
Vortex Tube ◽  
Turbulence Models ◽  
Swirl Flow ◽  
Experimental Results ◽  
Navier Stokes ◽  
Temperature Separation ◽  
Experiment Validation ◽  
Performance Curves ◽  
Mass Fractions ◽  
Flow Phenomena

A computational fluid dynamics (CFD) model is used to compare the effect of different Reynolds Averaged Navier-Stokes (RANS) based turbulence models in predicting the temperature separation and power separation in a Ranque-Hilsch vortex tube. Three first order turbulence models (standard k-?, Renormalized group RNG and shear stress transport (SST) K-? model) together with a second order numerical scheme are surveyed in the present work. The simulations are done in 2D steady, axisymetric with high swirl flow model. The performance curves (hot and cold outlet temperatures and power separation versus hot outlet mass fraction) obtained by using these turbulence models are compared with the experimental results in different cold mass fractions. The aim is to select an appropriate turbulence model for the simulation of the flow phenomena. Because of large discrepancy between 2D and experiment, validation in 3D model is also considered. The performance analysis shows that among all the turbulence models investigated in this study, temperature separation predicted by the Renormalized group RNG model is closer to the experimental results.

scholarly journals An Investigation of Turbulence Modelling in Transonic Fans Including a Novel Implementation of an Implicit κ–ϵ Turbulence Model

1992 ◽  
Author(s):  
Mark G. Turner ◽  
Ian K. Jennions
Keyword(s):  
Turbulence Models ◽  
Algebraic Model ◽  
Turbulence Modelling ◽  
Experimental Results ◽  
Navier Stokes ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Wall Functions ◽  
Solution Methods ◽  
Explicit Solver

An explicit Navier-Stokes solver has been written with the option of using one of two types of turbulence models. One is the Baldwin-Lomax algebraic model and the other is an implicit k-ϵ model which has been coupled with the explicit Navier-Stokes solver in a novel way. This type of coupling, which uses two different solution methods, is unique and combines the overall robustness of the implicit k-ϵ solver with the simplicity of the explicit solver. The resulting code has been applied to the solution of the flow in a transonic fan rotor which has been experimentally investigated by Wennerstrom. Five separate solutions, each identical except for the turbulence modelling details, have been obtained and compared with the experimental results. The five different turbulence models run were: the standard Baldwin-Lomax model both with and without wall functions, the Baldwin-Lomax model with modified constants and wall functions, a standard k-ϵ model and an extended k-ϵ model which accounts for multiple time scales by adding an extra term to the dissipation equation. In general, as the model includes more of the physics, the computed shock position becomes closer to the experimental results.

Numerical Investigation of the Thermo-Hydraulic Characteristics for Annular Vortex Tube: A Comparison With Ranque–Hilsch Vortex Tube

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Milad Khosravi ◽  
Meisam Sadi ◽  
Ahmad Arabkoohsar ◽  
Amir Ebrahimi-Moghadam
Keyword(s):  
Mass Fraction ◽  
Vortex Tube ◽  
Secondary Circulation ◽  
Outlet Section ◽  
Separation Performance ◽  
Outlet Temperature ◽  
Hydraulic Characteristics ◽  
Temperature Separation ◽  
Mass Fractions ◽  
Higher Temperature

Abstract In this work, a new configuration of the vortex tubes (VTs), called annular VTs, is proposed to improve the temperature separation performance. In the proposed configuration, a compartment has been added on the top of the tube wall that the separated hot outlet is repassed inside it over the hot tube. An axisymmetric swirl model of the Ranque–Hilsch (RH) and annual VTs is numerically simulated, and the thermo-hydraulic characteristics of them are compared for cold mass fractions ranging 0.2–0.8. The results illustrated that a small secondary circulation is created near the cold outlet of the RHVT that is not observed in the annular model. This secondary circulation is a destructive mechanism in VTs that results in more mixing and higher temperature in the cold outlet section. Analyzing the results indicates that using annular VT causes up to 12.51% increment of the hot outlet temperature compared to the RHVT model (which occurs at a mass fraction of 0.23). Also, up to 9.23% reduction of the cold outlet temperature is occurred (which occurs at a mass fraction of 0.37). These explanations prove the improvement of the annular VT compared to that of the conventional VTs.

scholarly journals Numerical modeling of the effect of energy-separation in the ranque-hilsch tube

2020 ◽  
Vol 27 ◽  
pp. 00109
Author(s):  
Boris L. Ivanov ◽  
Bulat G. Ziganshin ◽  
Andrey V. Dmitriev ◽  
Maxim A. Lushnov ◽  
Manuel O. Binelo
Keyword(s):  
Gas Flow ◽  
Vortex Tube ◽  
Turbulence Models ◽  
Effect Of Temperature ◽  
Energy Separation ◽  
Hydrodynamic Characteristics ◽  
Two Phase ◽  
Cross Sectional ◽  
Model Calculations ◽  
Temperature Separation

Currently, there are a lot of applications of vortex technologies. The vortex effect is used in gasdynamic cold generators and vortex cooling chambers. Vortex devices are also used as dehumidifiers, separators, for cooling and heating hydraulic fluids, separating two-phase media, gas mixtures, evacuating, etc. Scientists study the applicability of vortex equipment for traditional and freeze-drying of agricultural products. However, the influence of geometric parameters of vortex devices on the productivity and energy efficiency of temperature separation of gas flows is poorly studied. Research aimed at finding opportunities and expanding the field of application of vortex tubes is an urgent task. The paper describes twodimensional and three-dimensional mathematical models of the swirling gas flow arising in a vortex tube. It presents results of its implementation in the Anсs-Fluent software package. Thermodynamic and hydrodynamic characteristics confirm the effect of temperature separation in a vortex tube. The dependences of temperature separation on the swirl angle and inlet pressure were obtained. For a two-dimensional vortex tube model, calculations were carried out using various turbulence models. The influence of the cross-sectional area at the hot gas flow outlet on temperature separation was studied.

A Deterministic Stress Model for Rotor-Stator Interactions in Simulations of Average-Passage Flow

2002 ◽  
Vol 124 (2) ◽  
pp. 550-554 ◽  
Author(s):  
Charles Meneveau and ◽  
Joseph Katz
Keyword(s):  
Turbulence Models ◽  
Navier Stokes ◽  
Stress Model ◽  
Direct Measurements ◽  
Blade Row ◽  
Model Predictions ◽  
Stator Vane ◽  
Inflow Condition ◽  
Flow Phenomena ◽  
Inflow Conditions

A procedure for modeling deterministic stresses for average-passage simulations of flow in multiple blade-row turbomachines is proposed and tested. This method uses the results of several (two or more) steady Reynolds-averaged Navier-Stokes (RANS) simulations with boundary conditions that are representative of different inflow conditions encountered during the passage of a neighboring blade-row. The deterministic stresses are calculated by averaging the steady results while weighting them with the approximate duration of each inflow condition. This approach incorporates important rotor-stator interactions that are neglected in models based on a swept-wake approximation. The model is tested successfully by computing the deterministic stresses in the stator vane passage of a centrifugal pump, and comparing them with direct measurements using PIV data. Remaining discrepancies between model predictions and experimental data are probably linked to the inability of the turbulence models to account for flow phenomena at each phase, such as mid-vane separation.

scholarly journals Computational Fluid Dynamic Prediction and Physical Mechanisms Consideration of Thermal Separation and Heat Transfer Processes Inside Divergent, Straight, and Convergent Ranque–Hilsch Vortex Tubes

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Adib Bazgir ◽  
Nader Nabhani ◽  
Bahamin Bazooyar ◽  
Ali Heydari
Keyword(s):  
Vortex Tube ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Prediction ◽  
Temperature Separation ◽  
Flow Phenomena ◽  
Stream Lines ◽  
Physical Phenomena ◽  
Vortex Tubes

AbstractThe design of Ranque–Hilsch vortex tube (RHVT) seems to be interesting for refrigeration and air conditioning purposes in industry. Improving thermal efficiency of the vortex tubes could increase the operability of these innovative facilities for a wider heat and cooling demand to this end; it is of an interest to understand the physical phenomena of thermal and flow patterns inside a vortex tube. In this work, the flow phenomena and the thermal energy transfer in RHVT are studied for three RHVT: straight, divergent, and convergent vortex tubes. A three-dimensional numerical analysis of swirling or vortex flow is performed, verified, and validated against previous experimental and numerical data reported in literature. The flow field and the temperature separation inside an RHVT for different configuration of straight, five angles of divergent hot tube (1 deg, 2 deg, 3 deg, 4 deg, and 6 deg) and five angle of convergent hot tube (0.5 deg, 0.8 deg, 1 deg, 1.5 deg, and 2 deg) are investigated. The thermal performance for all investigated RHVTs configuration is determined and quantitatively assessed via visualizing the stream lines for all three scenarios.

A Study of Modest CFD Models for the Design of an Annular Diffuser With Struts for Swirling Flow

2008 ◽  
Author(s):  
G. K. Feldcamp ◽  
A. M. Birk
Keyword(s):  
Swirling Flow ◽  
Turbulence Models ◽  
Surface Flow ◽  
Experimental Results ◽  
Navier Stokes ◽  
Cfd Models ◽  
Pressure Distributions ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Visualization Techniques

Cold flow experiments were conducted to study swirling flows in an annular diffuser with various strut configurations. Experimental results at 0°, 20°, and 40° of inlet swirl were obtained. Measured properties included detailed inlet and exit traverses using three and seven hole pressure probes, surface pressure taps on the diffuser wall, and surface flow visualization techniques. Evaluation of the diffuser and strut performance was based on pressure recovery, and detailed pressure distributions. The experimental results have been studied further using Reynolds Averaged Navier Stokes (RANS) based Computational Fluid Dynamics (CFD). These models are of modest size (less than four million volumes). Several turbulence models have been used to predict the performance of the annular diffuser with struts. Both high and low Reynolds number implementations of the turbulence models have been investigated. The results show that modest CFD models can be used with confidence to design these devices.

Development and exploitation of a multipurpose CFD tool for optimisation of microbial reaction and sludge flow

2006 ◽  
Vol 53 (3) ◽  
pp. 101-110 ◽  
Author(s):  
T. Oda ◽  
T. Yano ◽  
Y. Niboshi
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Numerical Models ◽  
Numerical Technique ◽  
Turbulence Models ◽  
Reaction Model ◽  
Experimental Results ◽  
Navier Stokes ◽  
Transfer Model ◽  
The Right

A numerical analysis technique for optimisation of microbial reaction and sludge flow has been developed in this study. The technique is based on the 3D multiphase Navier–Stokes solver with turbulence models. In order to make numerical analyses of the total processes in wastewater treatment plants possible, four numerical models, the microbial reaction model, a sludge settling model, oxygen mass transfer model from coarse bubbles, and a model from fine bubbles, are added to the solver. All parameters included in those models are calibrated in accordance with experimental results, and good agreements between calculated results and experimental results are found. Finally, this study shows that the numerical technique can be used to optimise wastewater treatment plants with an example of the operational optimisation of an intermittent agitation in anoxic reactors by coarse bubbles. With a proper appreciation of its limit and advantages, the exploitation of the CFD efficiently leads us to the right direction even though it is not quantitatively perfect.

scholarly journals RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2348 ◽  
Author(s):  
Omar Mejia ◽  
Jhon Quiñones ◽  
Santiago Laín
Keyword(s):  
Turbulence Models ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Small Scale ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Phenomena ◽  
Water Turbine

Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.

SRANS and URANS CFD Simulations of Turbulent VHTR Lower Plenum Flow

2007 ◽  
Author(s):  
A. Ridluan ◽  
A. Tokuhiro
Keyword(s):  
Nuclear Reactor ◽  
Tube Bundle ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Eddy Simulation ◽  
Flow Phenomena ◽  
Flow Through ◽  
Reynolds Averaged Navier Stokes

Time-dependent and time-independent CFD simulations of the flow through a staggered tube bundle were performed. This flow configuration partially simulates the anticipated flow in the lower plenum of a Very High Temperature Reactor (VHTR) design. To design a nuclear reactor with confidence, one needs strict benchmarking as part of a validation and verification exercise for any and all commercial CFD codes. Thus CFD simulations (FLUENT) of isothermal (at present), periodic flow through a tube bundle using both Steady Reynolds Averaged Navier-Stokes (SRANS) and Unsteady Reynolds Averaged Navier-Stokes (URANS) equations were investigated. Selected turbulence models for a single tube diameter and inlet velocity based Re-number, Re ∼ 1.8 × 104, were investigated. The first-order turbulence models were: a standard k-ε turbulence model, a Renormalized Group (RNG) k-ε model, and lastly, a Shear Stress Transport (SST) k-ε model; the second-order model was a Reynolds Stress Model (RSM). Comparison of CFD simulations against experimental results of Simonin and Barcouda was undertaken at five stations (x, y) locations. Under the SRANS, we found the ability of the models to predict the turbulence stresses (u′u′, v′v′, u′v′) generally marginal to poor. However, upon adapting a concept from Large Eddy Simulation (LES), our URANS simulation with RSM revealed a spatiotemporal, oscillating flow structures in the wake. In contrast, it appears that the URANS with (even a) RNG k-ε model is unable to simulate this flow phenomena. In fact, the data suggests that the RNG k-ε model is too spatiotemporally dissipative. Some aspects of the SRANS versus URANS and using the aforementioned turbulence models will be presented.

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