Assessment of Different Turbulence Models in Helically Coiled Pipes Through Comparison With Experimental Data

2012 ◽  
Author(s):  
Marco Colombo ◽  
Antonio Cammi ◽  
Marco E. Ricotti
Keyword(s):  
Turbulent Flow ◽  
Great Influence ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Test Facility ◽  
Wall Functions ◽  
Pressure Drops ◽  
Fully Developed Turbulent Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Helical Geometry

This paper deals with a comprehensive study of fully developed single-phase turbulent flow and pressure drops in helically coiled channels. To the aim, experimental pressure drops were measured in an experimental campaign conducted at SIET labs, in Piacenza, Italy, in a test facility simulating the Steam Generator (SG) of a Generation III+ integral reactor. Very good agreement is found between data and some of the most common correlations available in literature. Also more data available in literature are considered for comparison. Experimental results are used to assess the results of Computational Fluid Dynamics (CFD) simulations. By means of the commercial CFD package FLUENT, different turbulence models are tested, in particular the Standard, RNG and realizable k-ε models, Shear Stress Transport (SST) k-ω model and second order Reynolds Stress Model (RSM). Moreover, particular attention is placed on the different types of wall functions utilized through the simulations, since they seem to have a great influence on the calculated results. The results aim to be a contribution to the assessment of the capability of turbulence models to simulate fully developed turbulent flow and pressure drops in helical geometry.

scholarly journals Performance of Turbulence Models and Near-Wall Treatments in Discrete Jet Film Cooling Simulations

1998 ◽  
Author(s):  
Jeffrey D. Ferguson ◽  
Dibbon K. Walters ◽  
James H. Leylek
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Turbulence Models ◽  
Viscous Sublayer ◽  
Reynolds Stress Model ◽  
Quality Data ◽  
Wall Functions ◽  
First Time ◽  
Near Wall ◽  
Non Equilibrium

For the first time in the open literature, code validation quality data and a well-tested, highly reliable computational methodology are employed to isolate the true performance of seven turbulence treatments in discrete jet film cooling. The present research examines both computational and high quality experimental data for two length-to-diameter ratios of a row of streamwise injected, cylindrical film holes. These two cases are used to document the performance of the following turbulence treatments: 1) standard k-ε model with generalized wall functions; 2) standard k-ε model with non-equilibrium wall functions: 3) Renormalization Group k-ε (RNG) model with generalized wall functions; 4) RNG model with non-equilibrium wall functions: 51 standard k-ε model with two-layer turbulence wall treatment; 6) Reynolds Stress Model (RSM) with generalized wall functions; and 7) RSM with non-equilibrium wall functions. Overall, the standard k-ε turbulence model with the two-layer near-wall treatment, which resolves the viscous sublayer, produces results that are more consistent with experimental data.

Measurement of a Recirculating, Two-Dimensional, Turbulent Flow and Comparison to Turbulence Model Predictions. I: Steady State Case

1983 ◽  
Vol 105 (4) ◽  
pp. 439-446 ◽  
Author(s):  
D. R. Boyle ◽  
M. W. Golay
Keyword(s):  
Steady State ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Scale Model ◽  
Test Facility ◽  
Two Dimensional ◽  
Mean Velocity ◽  
Flow Area ◽  
Flow Measurements

Turbulent flow measurements have been performed in a two-dimensional flow cell which is a 1/15-scale model of the Fast Flux Test Facility nuclear reactor outlet plenum. In a steady water flow, maps of the mean velocity field, turbulence kinetic energy, and Reynolds stress have been obtained using a laser doppler anemometer. The measurements are compared to numerical simulations using both the K–ε and K–σ two-equation turbulence models. A relationship between K–σ and K–ε turbulence models is derived, and the two models are found to be nearly equivalent. The steady-state mean velocity data are predicted well through-out most of the test cell. Calculated spatial distributions of the scalar turbulence quantities are qualitatively similar for both models; however, the predicted distributions do not match the data over major portions of the flow area. The K–σ model provides better estimates of the turbulence quantity magnitudes. The predicted results are highly sensitive to small changes in the turbulence model constants and depend heavily on the levels of inlet turbulence. However, important differences between prediction and measurement cannot be significantly reduced by simple changes to the model’s constants.

CFD Simulation of 5×5 Rod Bundles With Split-Type Spacers

2013 ◽  
Author(s):  
K. Podila ◽  
J. Bailey ◽  
Y. F. Rao ◽  
M. Krause
Keyword(s):  
Cfd Simulation ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Atomic Energy ◽  
Rod Bundles ◽  
Spacer Grid ◽  
Two Phase ◽  
Ansys Fluent ◽  
Computational Fluid Dynamics Cfd ◽  
Canada Limited

Atomic Energy of Canada Limited (AECL) has initiated a program to develop Computational Fluid Dynamics (CFD) capability for simulating single- and two-phase flows in rod-bundles. In the current work, a 5×5 rod assembly with a split-type spacer grid is simulated with ANSYS Fluent 14 using unsteady simulations with a fully conformal hybrid mesh (wall y+∼30). This work represents results of AECL’s recent participation in the OECD/NEA organized CFD benchmarking exercise on the MATiS-H experiment performed at the Korean Atomic Energy Research Institute (KAERI). The sensitivity to turbulence models is tested using the standard k-ε and the Reynolds stress model (RSM). Reasonable agreement is achieved between the calculated and experimental velocity values in the region close to the spacer grid, whereas turbulence intensity values are underpredicted compared to the experiments.

scholarly journals NUMERICAL ANALYSIS OF SWIRL INTENSITY IN TURBULENT SWIRLING PIPE FLOWS

2016 ◽  
Vol 78 (5-10) ◽  
Author(s):  
Bahbibi Rahmatullah ◽  
Khairul Fikri Tamrin ◽  
Nadeem Ahmed Sheikh
Keyword(s):  
Turbulent Flow ◽  
Swirling Flow ◽  
Reynolds Stress Model ◽  
Swirling Flows ◽  
Complex Flow ◽  
Cfd Simulations ◽  
Swirl Intensity ◽  
Computational Fluid Dynamics Cfd ◽  
Computational Resources ◽  
And Control

Swirling flows are often observed in nature such as weather systems, cyclones and tornados. A number of applications use swirling nature of flow for enhanced mixing, heat transport and other transport phenomena. Naturally occurring swirls as well as induced swirls are often usually turbulent in nature. Understanding the flow physics of turbulent swirling flow is important for better understanding and control of processes involving swirling flows. With the increase of computational resources and advancements in turbulent flow modelling, it is now possible to simulate highly complex flow structures. Here turbulent swirling flow induced by guide vanes is studied using Computational Fluid Dynamics (CFD) simulations in a two-dimensional axisymmetric channel. The results for the variation of velocity components are compared with the work of an earlier research. The results are initially compared for the evaluation of best discretisation scheme. It was observed that the second-order and third-order schemes produced similar results. To simulate the turbulent flow two equations (k-ε) model and the five equations Reynolds Stress Model (RSM) are used. The comparison of both models with higher order discretisation schemes shows that the standard k-ε model is incapable of predicting the main features of the flow whilst RSM yields result close to the experimental data.

CFD Analysis for the Turbulent Flow Distribution in a Fuel Assembly with the Split-Type Mixing Vanes by Using the Advanced Scale-Resolving Turbulence Models

2015 ◽  
Vol 752-753 ◽  
pp. 902-907 ◽  
Author(s):  
Gong Hee Lee ◽  
Ae Ju Cheong
Keyword(s):  
Turbulent Flow ◽  
Fuel Assembly ◽  
Turbulence Models ◽  
Measured Data ◽  
Test Facility ◽  
Detached Eddy Simulation ◽  
Axial Velocity Component ◽  
Pressurized Water ◽  
Ansys Cfx ◽  
Significant Difference

In general, the turbulent flow inside PWR (Pressurized Water Reactor) fuel assembly depends on the mixing vane configuration and the pattern of the mixing vane arrangement on the strap of the spacer grid. In this study, in order to examine the turbulent flow structure inside fuel assembly with the split-type mixing vanes, simulations were conducted with the commercial CFD (Computational Fluid Dynamics) software, ANSYS CFX R.14. Two different types of turbulence models, i.e. SAS (Scale-Adaptive Simulation)-SST (Shear Stress Transport) and DES (Detached Eddy Simulation), were used. The predicted results were compared with the measured data from the MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility. Although there were locally differences between the prediction and the measurement, ANSYS CFX R.14 predicted the time averaged velocity field in the reliable level. The predicted horizontal and vertical velocity components were more in agreement with the measured data than the axial velocity component. There was no significant difference in the prediction accuracy of both turbulence models.

Effect of Asymmetric Jet Placement on Turbulent Flow Structure Inside a Jet-Stirred Reactor

2010 ◽  
Author(s):  
Khaled J. Hammad ◽  
Ivana M. Milanovic
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Flow Structure ◽  
Turbulence Models ◽  
Vortex Identification ◽  
Reynolds Decomposition ◽  
Fully Developed Turbulent Flow ◽  
Identification Technique ◽  
Turbulent Flow Structure ◽  
Wall Interaction

Particle Image Velocimetry (PIV) was used to investigate the turbulent flow structure inside a jet-stirred cylindrical vessel. The submerged jet issued vertically downward from a long pipe ensuring fully developed turbulent flow conditions at the outlet. The Reynolds number based on jet mean exit velocity was 15,000. The effect of symmetric and asymmetric nozzle placement within the vessel on the resulting flow patterns was also studied. The measured turbulent velocity fields are presented using Reynolds decomposition into mean and fluctuating components, which, for the selected flow configuration, inflow and boundary conditions, allow for straightforward assessment of turbulence models and numerical schemes. The flow field was subdivided into three regions: the jet, the jet-wall interaction and bulk of vessel. Proper Orthogonal Decomposition (POD) analysis was applied to identify the most energetic coherent structures of the turbulent flow field in the bulk of tank region. The swirling strength vortex identification technique was used to detect the existence and strength of vortical structures in the jet region.

Investigation on the Turbulence Models Effect of a Coal Classifier by Using Computational Fluids Dynamics

2013 ◽  
Vol 465-466 ◽  
pp. 617-621
Author(s):  
Norasikin Mat Isa ◽  
Ahmad Norman Khalis Ahmad Fara ◽  
Nor Zelawati Asmuin
Keyword(s):  
Turbulence Models ◽  
Reynolds Stress Model ◽  
The Other ◽  
Stress Model ◽  
Velocity Data ◽  
Ansys Software ◽  
Air Velocity ◽  
Computational Fluids Dynamics ◽  
Computational Fluids ◽  
Computational Fluid Dynamics Cfd

This study evaluates five turbulence models to determine the best models to be implemented as it representing the turbulent flow inside the lab scale classifier. The models studied are: The standard ƙ-ɛ model, Renormalization-group (RNG) ƙ-ɛ model, Realizable ƙ-ɛ model, Standard k-ω model, and Reynolds stress model (RSM). Through analysis of air flow, the air velocity data can be obtained from computational fluid dynamics (CFD), the result shows that, standard ƙ-ɛ model and Realizable ƙ-ɛ model are found to be more appropriate to use than the other turbulence models. The model validation is conducted by comparing the simulated velocities with experimental data in a lab scale classifier from literature. ANSYS software is selected to be used to run the simulation and analysis.

Measurements and Predictions of a Highly Turbulent Flowfield in a Turbine Vane Passage

2000 ◽  
Vol 122 (4) ◽  
pp. 666-676 ◽  
Author(s):  
R. W. Radomsky ◽  
K. A. Thole
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flow ◽  
Gas Turbine ◽  
Turbulent Kinetic Energy ◽  
Reynolds Stress ◽  
Complex Geometry ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Mean Flow

As highly turbulent flow passes through downstream airfoil passages in a gas turbine engine, it is subjected to a complex geometry designed to accelerate and turn the flow. This acceleration and streamline curvature subject the turbulent flow to high mean flow strains. This paper presents both experimental measurements and computational predictions for highly turbulent flow as it progresses through a passage of a gas turbine stator vane. Three-component velocity fields at the vane midspan were measured for inlet turbulence levels of 0.6%, 10%, and 19.5%. The turbulent kinetic energy increased through the passage by 130% for the 10% inlet turbulence and, because the dissipation rate was higher for the 19.5% inlet turbulence, the turbulent kinetic energy increased by only 31%. With a mean flow acceleration of five through the passage, the exiting local turbulence levels were 3% and 6% for the respective 10% and 19.5% inlet turbulence levels. Computational RANS predictions were compared with the measurements using four different turbulence models including the k-ε, Renormalization Group (RNG) k-ε, realizable k-ε, and Reynolds stress model. The results indicate that the predictions using the Reynolds stress model most closely agreed with the measurements as compared with the other turbulence models with better agreement for the 10% case than the 19.5% case. [S0098-2202(00)00804-X]

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.

scholarly journals Viscous Flow Field Computations for a Transonic Axial-Flow Compressor Blade Using Different Turbulence Models

1997 ◽  
Author(s):  
L. J. Lenke ◽  
H. Simon
Keyword(s):  
Three Dimensional ◽  
Great Influence ◽  
Axial Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Compressor Blade ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Inlet Conditions ◽  
Flow Compressor

New blading concepts as used in modern transonic axial-flow compressors require improved calculation methods. Here the turbulence modelling has great influence. Therefore a quasi-three-dimensional compressor blade with subsonic inlet conditions is calculated using different turbulence models. A low-Reynolds number k-ϵ, the k-ω model and an explicit algebraic Reynolds stress model are considered in this investigation. The results from these calculations in form of comparisons between the predicted isentropic Mach number distributions, profile losses and exit flow angles with experimental data are presented in this paper. They demonstrate the differences between the models in the prediction of the separation behavior of blade surface boundary layer especially which are introduced by shocks. For the high inlet Mach numbers the models differ also in the prediction of losses and deviation angles at design and off-design conditions.

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