scholarly journals Numerical Investigation on Influence of Gas and Turbulence Model for Type III Hydrogen Tank under Discharge Condition

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6432
Author(s):  
Moo-Sun Kim ◽  
Joon-Hyoung Ryu ◽  
Seung-Jun Oh ◽  
Jeong-Hyeon Yang ◽  
Sung-Woong Choi
Keyword(s):  
Turbulence Model ◽  
Turbulence Intensity ◽  
Gas Flow ◽  
Transport Model ◽  
Numerical Models ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Hydrogen Gas ◽  
Discharge Temperature ◽  
Compressed Gas

The high-pressure gaseous hydrogen (HPGH2) storage method is widely used owing to the low density of hydrogen gas at ambient temperature and atmospheric pressure. Therefore, rigorous safety analysis of the filling and discharging of compressed gas in a hydrogen tank is required to achieve reliable operational solutions for the safe storage of hydrogen. In this study, the behavior of compressed hydrogen gas in a hydrogen tank was investigated for its discharge. Numerical models for the adaptation of gas and turbulence models were examined. Gas model effects were examined to account for hydrogen gas behavior at the discharge temperature and pressure conditions. Turbulence model effects were analyzed to consider the accuracy of each model: the assessment of the turbulence models was compared in terms of the turbulence intensity. From the study of gas model effect, the Redlich–Kwong equation was found to be one of the realistic gas models of the discharging gas flow. Among the turbulence models, the shear stress transport model and Reynolds stress model predicted the compressed gas behavior more accurately, showing a lower turbulence intensity than those of the realizable and renormalization group models.

Numerical Investigation of Turning Diffuser Performance by Varying Geometric and Operating Parameters

2012 ◽  
Vol 229-231 ◽  
pp. 2086-2093 ◽  
Author(s):  
Normayati Nordin ◽  
Vijay R. Raghavan ◽  
Safiah Othman ◽  
Zainal Ambri Abdul Karim
Keyword(s):  
Numerical Investigation ◽  
Turbulence Model ◽  
Transport Model ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Pressure Recovery ◽  
Maximum Pressure ◽  
Operating Parameters ◽  
Flow Uniformity ◽  
Outlet Pressure

This paper presents a numerical investigation of pressure recovery and flow uniformity in turning diffusers with 90o angle of turn by varying geometric and operating parameters. The geometric and operating parameters considered in this study are area ratio (AR= 1.6, 2.0 and 3.0) and inflow Reynolds number (Rein=23, 2.653E+04, 7.959E+04, 1.592E+05 and 2.123E+05). Three turbulence models, i.e. the standard k-e turbulence model (std k-e), the shear stress transport model (SST-k-W) and the Reynolds stress model (RSM) were assessed in terms of their applicability to simulate the actual cases. The standard k-e turbulence model appeared as the best validated model, with the percentage of deviation to the experimental being the least recorded. Results show that the outlet pressure recovery of a turning diffuser at specified Rein improves approximately 32% by varying the AR from 1.6 to 3.0. Whereas, by varying the Rein from 2.653E+04 to 2.123E+05, the outlet pressure recovery at specified AR turning diffuser improves of approximately 24%. The flow uniformity is considerably distorted with the increase of AR and Rein. Therefore, there should be a compromise between achieving the maximum pressure recovery and the maximum possible flow uniformity. The present work proposes the turning diffuser with AR=1.6 operated at Rein=2.653E+04 as the optimum set of parameters, producing pressure recovery of Cp=0.320 and flow uniformity of su=1.62, with minimal flow separation occurring in the system.

Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart–Shur Correction Term

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Pavel E. Smirnov ◽  
Florian R. Menter
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Transport Model ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Reynolds Stress Transport Model ◽  
Wide Range ◽  
Sst Model ◽  
The One

A rotation-curvature correction suggested earlier by Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) for the one-equation Spalart–Allmaras turbulence model is adapted to the shear stress transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and direct numerical simulations (DNS) data, on the one hand, and with the corresponding results of the original SST model and advanced Reynolds stress transport model (RSM), on the other hand. It is found that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

scholarly journals Effects of Various Modeling Schemes on Mist Film Cooling Simulation

2007 ◽  
Vol 129 (4) ◽  
pp. 472-482 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cooling Effectiveness ◽  
Air Supply ◽  
Cooling Enhancement ◽  
Simulation Results ◽  
Density Ratios ◽  
Cooling Air

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Simulation of a two-dimensional (2D) slot film cooling with a fixed blowing angle and blowing ratio shows a 2% mist (by mass) injected into the cooling air can increase the cooling effectiveness about 45%. The renormalization group (RNG) k-ε model, Reynolds stress model, and the standard k-ε turbulence model with an enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance deteriorates when the plenum is included in the calculation due to the altered velocity profile and turbulence intensity at the jet exit plane. The results of this paper can provide guidance for corresponding experiments and serve as the qualification reference for future more complicated studies with 3D cooling holes, different blowing ratios, various density ratios, and rotational effect.

Analysis of Unsteady Turbulent Merging Jet Flows With Temperature Difference

2002 ◽  
Author(s):  
Geun Jong Yoo ◽  
Won Dae Jeon
Keyword(s):  
Temperature Variation ◽  
Turbulent Flows ◽  
Turbulence Model ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Jet Flow ◽  
Reynolds Stress Model ◽  
Jet Flows ◽  
Test Cases ◽  
Temperature Variance

Suitable turbulence model is required in the course of establishing a proper analysis methodology for thermal stripping phenomena. For this purpose, three different turbulence models of k-ε model, modified k-ε model, and full Reynolds stress model and VLES are applied to analyze unsteady turbulent flows with temperature variation. Four test cases are selected for verification. These are vertical jet flows with water and sodium, parallel jet flow with sodium, and merging pipe flow through T-junction with sodium. The geometries of test cases well represent common places where thermal stripping might be occurred. The turbulence model computation shows overall jet flow characteristics well and good comparison of mean temperature distribution. Temperature variance (θ′2) is rather over-predicted, but location of high temperature variance is matched well with that of the large amplitude of temperature variation of experimental results. Meanwhile, mixing of hot and cold jet flow is found to be not that active.

Influence of Freestream Turbulence Intensity on Cooling Effectiveness

2001 ◽  
Author(s):  
E. Laroche
Keyword(s):  
Turbulence Intensity ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Temperature Fields ◽  
Type Model ◽  
Freestream Turbulence ◽  
Cooling Effectiveness ◽  
Flow Parameters ◽  
Injection Region ◽  
Correct Estimation

The objective of the study is to evaluate the potential of various turbulence models to simulate satisfactorily the influence of freestream turbulence intensity on the development of a cooling film, via a coupled computation, i.e. taking into account the full geometry (plenum, hole and main channel). Isotropic as well as anisotropic turbulence models (for the velocity as well as for the temperature fields) are tested, and an insight on the best suited closure is expected. The question of the respective influences of the various flow parameters (boundary layer characteristics, turbulent length scales, mass blowing ratios…) is also addressed. A low Reynolds number approach gives a correct estimation of the cooling effectiveness after approximately 10 hole diameters, for high or small blowing ratios, and using a k-ε model. The standard k-1 model largely underestimates the mixing in the injection region. The prediction of the injection region still needs to be improved for most configurations, but qualitatively the computation seems more than acceptable, as it exhibits the classically identified counter-rotating vortices that drive the heat transfer phenomena. The study also showed that predicting the influence of the freestream turbulence intensity requires taking into account thermal anisotropies, using an EARSMt (Explicit Algebraic Reynolds Stress Model, t being for Thermal) type model. An increase in freestream turbulence intensity was then shown to diminish the cooling effectiveness for all blowing ratios. The magnitude of the drop has still to be satisfactorily captured.

Evaluation of RANS Approach in Predicting the Physics of Incompressible Turbulent Jets-Into-Crossflows

2007 ◽  
Author(s):  
Khodyar Javadi ◽  
Mohammad Taeibi-Rahni ◽  
Masoud Darbandi
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Numerical Data ◽  
Turbulent Jets ◽  
Reynolds Stress Model ◽  
Shear Stress Transport Model ◽  
Near Wall

This work is conducted with evaluation of different turbulence models capabilities in predicting three dimensional jet-into-crossflow (JICF) interactions. For this purpose, first of all, comprehensive discussions on the near wall flow complexities due to discharge of a jet into a crossflow are presented. In this regards, large scale coherent structures such as: counter rotating vortex pairs (CRVP’s), near wall secondary motions, horseshoe vortices, and wall jets like are discussed. Secondly, the abilities of different turbulence models in predicting such flows (JICF) are evaluated. Our evaluation is based on three points of view including: 1) JICF characteristics, 2) computed location, and 3) sensitivity to different flow variables. In this regard, the turbulence models such as k-ε, k-ω, shear stress transport model (SST), and Reynolds stress model (RSM) are employed. Their related results are compared to credential available experimental/numerical data as well themselves. Since the same basic code with the same grid density as well as numerical discretization scheme is used, it is save to conclude that, any differences in the results are due to the abilities of turbulence models. The flow field computation was governed by Reynolds Averaged Navier-Stokes (RANS) equations performing finite volume method with SIMPLE algorithm over a non-uniform structured grid.

Numerical simulation of the 3D unsteady turbulent flow in a combustion chamber

2011 ◽  
Vol 1 (2) ◽  
Author(s):  
Adrian Stuparu ◽  
Sorin Holotescu
Keyword(s):  
Numerical Simulation ◽  
Combustion Chamber ◽  
Gas Flow ◽  
Bluff Body ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Recirculation Region ◽  
Eddy Simulation ◽  
Large Eddy ◽  
3D Unsteady Flow

AbstractThe influence of turbulence models on the 3D unsteady flow in a combustion chamber with a central bluff body is analyzed. Three different turbulence models are used (realizable k-ε, Reynolds Stress Model and Large Eddy Simulation) and a comparison is made on the evolution of the velocity field over time. The numerical simulation of the gas flow in the combustion chamber was performed using FLUENT 6.3 software and the computational geometry, consisting of a structured mesh with 810,000 cells, was built using the pre-processor GAMBIT 2.4. The extent of the recirculation region behind the bluff body was determined for each turbulence model.

scholarly journals A Numerical Simulation of Turbulent Flow through a Curved Duct

2012 ◽  
Vol 11 (3) ◽  
pp. 169-178
Author(s):  
A K Biswas ◽  
Ashoke K Raman ◽  
A N Mullick
Keyword(s):  
Numerical Simulation ◽  
Turbulence Model ◽  
Experimental Work ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Experimental Results ◽  
Pressure Probe ◽  
Mean Velocity ◽  
Numerical Work ◽  
Flow Through

This paper presents the comparison the results of an experimental work with a numerical work keeping the geometry of the test duct and inlet boundary conditions unaltered. The numerical simulation is validated with the experimental results based on the wall y+ approach for different turbulence models suited for this type of geometry. The experimental work is carried out at mass averaged mean velocity of 40m/s with the measurement of total pressure by a pre-calibrated multi-hole pressure probe and the results presented in the form of a pressure contours in 2-D. For validation of the numerical results Standard k-ε, k-ω and Reynolds Stress Model (RSM) are used to solve the closure problem. The turbulence models are investigated in the commercial CFD code of Fluent using y+ value as guidance in selecting the appropriate grid configuration and turbulence model. Based on the wall y+ values for different turbulence models, it is concluded in the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features and RSM turbulence model predicts the best results while comparing with the experimental results.

scholarly journals NUMERICAL MODELING DISTRIBUTION OF CONTAMINATING SUBSTANCES IN STREET CANYONS

2020 ◽  
pp. 84-92
Author(s):  
А.А. Issakhov ◽  
◽  
Zh.E. Bekzhigitova ◽  
P.T. Omarova ◽  
◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Gas Flow ◽  
Numerical Models ◽  
Turbulence Models ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Street Canyons ◽  
Small Deviations ◽  
Contaminating Substances ◽  
Experimental Values

In this study, we simulated the dynamics of the gas flow near a one-parameter model of the building. To study the gas tracing process, several types of barriers of various heights were applied. Ethylene - С2Н4 was chosen as an indicator gas. Numerical modeling was performed using the time-averaged Navier-Stokes (RANS) equations, with the Boussinesq approximation, by comparing the simulation results with the experimental results of famous authors. According to the results of the study, it was found that the use of the RANS model in conjunction with k-e Realizable (RLZ), kw SST (SST), DES k-e (DES) turbulence models yielded practically comparable results with small deviations, which made it possible to choose k-e Realizable turbulence models. In addition, it was found that with an increase in the height of the barrier, an increase in the retention properties in the region between the structure and the barrier is observed. In general, the numerical results are commensurate with the experimental values, which confirms the correctness of the mathematical and numerical models used. These studies can be applied in the future for a more detailed study of the influence of perpendicular flows of the spread of pollutants within the urban canyon.

Application of Nonlinear Turbulence Models for Marine Propulsors

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Prachakon Kaewkhiaw ◽  
Yodchai Tiaple ◽  
Pramote Dechaumphai ◽  
Varangrat Juntasaro
Keyword(s):  
Turbulence Model ◽  
Flow Characteristic ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Combined Effects ◽  
Marine Propeller ◽  
Efficient Design ◽  
Thrust And Torque ◽  
First Time

The realistic simulation of cavitation on a marine propeller is important for the efficient design of the propeller. However, the flow characteristic that occurred on the marine propeller is complicated and difficult to predict due to the combined effects of turbulence, cavitation, and multiphase phenomena. There is still currently no turbulence model that can predict these combined effects satisfactory. The nonlinear turbulence model is therefore modified and applied to predict the cavitation on a marine propeller for the first time in this work. It is found that the nonlinear turbulence model can predict the cavitation and hence the thrust and torque coefficients much more accurately than the existing Reynolds-averaged Navier–Stokes turbulence models including the Reynolds-stress model.

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