scholarly journals INVESTIGATION OF THE GRID MODEL AND TURBULENCE MODEL PARAMETERS INFLUENCE ON QUALITY OF TURBINE ROTOR BLADE TIP CLEARANCE AREA AERODYNAMIC PROCESSES MODELING

2021 ◽  
pp. 67-78
Author(s):  
Diana Popova ◽  
◽  
Denis Popov ◽  
Nikita Samoylenko ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Numerical Methods ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Stage ◽  
Model Parameters ◽  
Grid Model

Aerodynamic processes mathematical modeling is carried out using numerical methods. Now the level of development of software numerical methods of three-dimensional gas-dynamic modeling of processes in turbomachinery makes it possible to determine with high accuracy the main characteristics of units at the design stage. It significantly reduces the time and cost of production. This article proposes a methodology for installation and improving the mathematical and grid model of HPT rotor blade to improve the quality of three-dimensional modeling. Aerodynamic processes mathematical modeling in aircraft turbojet engine blade rows is carried out using numerical methods. Grid model settings and turbulence model significantly affect the results qualitative characteristics and the calculations duration. This article proposes a methodology for grid model constructing based on local intense vortex formation and flow mixing places thickening. The influence of the grid and turbulence models parameters are estimated on the kinetic energy losses amount and secondary flows structure. The design model includes the building geometric model, preparation of the grid model and description of the turbulence model. Influence of grid and BSL and SST turbulence models on results of turbine blade aerodynamic calculation is considered in this article. Basic recommendations for the construction of mathematical and grid models in the ANSYS for uncooled rotor blades have been developed.

Evaluation of Different Turbulence Models Applied in Turbopump’s Hydraulic Turbine

2021 ◽  
Author(s):  
Daniel Ferreira Corrêa Barbosa ◽  
Daniel da Silva Tonon ◽  
Luiz Henrique Lindquist Whitacker ◽  
Jesuino Takachi Tomita ◽  
Cleverson Bringhenti
Keyword(s):  
Boundary Conditions ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Space Shuttle ◽  
Turbulence Models ◽  
Tip Clearance ◽  
Test Facility ◽  
Speed Ratio ◽  
Computational Domain ◽  
Axial Turbine

Abstract The aim of this work is an evaluation of different turbulence models applied in Computational Fluid Dynamics (CFD) techniques in the turbomachinery area, in this case, in an axial turbine stage used in turbopump (TP) application. The tip clearance region was considered in this study because it has a high influence in turbomachinery performance. In this region, due to its geometry and the relative movement between the rotor row and casing, there are losses associated with vortices and secondary flow making the flowfield even more turbulent and complex. Moreover, the flow that leaks in the tip region does not participate in the energy transfer between the fluid and rotor blades, degradating the machine efficiency and performance. In this work, the usual flat tip rotor blade geometry was considered. The modeling of turbulent flow based on Reynolds Averaged Navier-Stokes (RANS) equations predicts the variation of turbine operational characteristics that is sufficient for the present turbomachine and flow analysis. Therefore, the appropriate choice of the turbulence model for the study of a given flow is essential to obtain adequate results using numerical approximations. This comparison become important due to the fact that there is no general turbulence model for all engineering applications that has fluid and flow. The turbomachine considered in the present work, is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME), considering the 3.0% tip clearance configuration relative to rotor blade height. The turbulence models evaluated in this work were the SST (Shear Stress Transport), the k-ε Standard and the k-ε RNG. The computational domain was discretized in several control volumes based on unstructured mesh. All the simulations were performed using the commercial software developed by ANSYS, CFX v15.0 (ANSYS). All numerical settings and how the boundary conditions were imposed at different surfaces are explained in the work. The boundary conditions settings follow the same rule used in the test facility and needs some attention during the simulations to vary the Blade-Jet-Speed ratio parameter adequately. The results from numerical simulations, were synthesized and compared with the experimental data published by National Aeronautics and Space Administration (NASA), in which the turbine efficiency and its jet velocity parameter are analyzed for each turbulence model result. The work fluid considered in this work was water, the same fluid used in the NASA test facility.

scholarly journals Comparison of Three Measures to Promote National Fitness in China by Mathematical Modeling

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Pan Tang ◽  
Daqing Xu ◽  
Qing Dai ◽  
Tingting Huang
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Physical Exercise ◽  
Three Dimensional ◽  
Chinese Government ◽  
Model Parameters ◽  
National Bureau ◽  
Short Period ◽  
Key Parameter

In this paper we established a mathematical model for national fitness in China. Based on a questionnaire and data of the General Administration of Sport of China and the National Bureau of Statistics of China, the dynamics for three classes of people are expressed by a system of three-dimensional ordinary equations. Model parameters are estimated from the data. This study indicated that national fitness put out by the Chinese government is reasonable. By finding the key parameter, the best measure to promote national fitness is put forward. In order to increase the number of people who frequently participate in sport exercise in a short period of time, if only one measure can be chosen, guiding people who never take part in physical exercise will be the best measure.

Aerothermal Study of the Unsteady Flow Field in a Transonic Gas Turbine With Inlet Temperature Distortions

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
S. Salvadori ◽  
F. Montomoli ◽  
F. Martelli ◽  
P. Adami ◽  
K. S. Chana ◽  
...  
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Inlet Temperature ◽  
Phase Lag ◽  
Turbine Stage ◽  
Inlet Conditions ◽  
University Of Florence ◽  
The University

Computational fluid dynamics (CFD) prediction of the unsteady aerothermal interaction in the HP turbine stage, with inlet temperature nonuniformity, requires appropriate unsteady modeling and a low diffusive numerical scheme coupled with suitable turbulence models. This maybe referred to as high fidelity CFD. A numerical study has been conducted by the University of Florence in collaboration with ONERA to compare capabilities and limitations of their CFD codes for such flows. The test vehicle used for the investigation is a turbine stage of three-dimensional design from the QinetiQ turbine facility known as MT1. This stage is a high pressure transonic stage that has an unshrouded rotor, configured, and uncooled with 32 stators and 60 rotor blades. Two different CFD solvers are compared that use different unsteady treatments of the interaction. A reduced count ratio technique has been used by the University of Florence with its code HYBFLOW, while a phase lag model has been used by ONERA in their code, ELSA. Four different inlet conditions have been simulated and compared with focus on the experimental values provided by QinetiQ in the frame of TATEF and TATEF2 EU Sixth Framework Projects. The differences in terms of performance parameters and hot fluid redistribution, as well as the time- and pitch-averaged radial distributions on a plane downstream of the rotor blade, have been underlined. Special attention was given to the predictions of rotor blade unsteady pressure and heat transfer rates.

scholarly journals Improving the quality of design calculations of viscous flow in low-flow centrifugal compressor stages by methods of computational fluid dynamics through reasonable application of different turbulence models

2021 ◽  
pp. 24-30
Author(s):  
S. V. Kartashev ◽  
◽  
Yu. V. Kozhukhov ◽  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Model ◽  
Centrifugal Compressor ◽  
Turbulence Models ◽  
Low Flow ◽  
Solution Stability ◽  
Relative Width ◽  
Computational Domain

The paper considers the issue of improving the quality of the numerical experiment in the calculation of viscous gas in the flowing part of a low-flow centrifugal compressor stage. The choice of turbulence model in creating a calculation model for calculations by methods of computational fluid dynamics is substantiated. As object of research is chosen low-flow stage with conditional flow coefficient Ф=0,008 and relative width at impeller outlet b2 /D2 =0,0133. The issue of qualitative modeling of friction losses in low-flow stages is of fundamental importance and is directly related to the choice of turbulence model. It is shown that the choice of low-Reynolds turbulence models in the case of unloaded and discontinuous low-flow stages can be made from the main common models (SpalartAllmaras, SST, k-ω) based on the economy of calculations, speed of convergence, solution stability and adequacy of the obtained results. For models with wall functions, the quality of the mesh model and the observance of the dimensionless distance to the wall y+ throughout the calculation domain are particularly important. For highReynolds turbulence models, at values of y+=25...50 on all friction surfaces of the computational domain in the optimal mode of operation, the grid independence of the solution for the entire gas-dynamic characteristic is ensured. It is unacceptable for y+ to fall into the transition region of 4...15 between the viscous sublayer and the region of the logarithmic velocity profile

scholarly journals On the “Early-Time” Evolution of Variables Relevant to Turbulence Models for the Rayleigh-Taylor Instability

2010 ◽  
Author(s):  
Bertrand Rollin ◽  
Malcolm J. Andrews
Keyword(s):  
Turbulence Model ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Early Time ◽  
Variable Density ◽  
Taylor Instability ◽  
Turbulent Regime ◽  
Rayleigh Taylor Instability

We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model [1] for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant variables before fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of mixing between two interpenetrating fluids to define the initial profiles for the turbulence model variables. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted profiles for the turbulence model variables and profiles of the variables obtained from low Atwood number three dimensional simulations show reasonable agreement.

Comparison of Various RANS Models for Impinging Round Jet Cooling From a Cylinder

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Ketan Atulkumar Ganatra ◽  
Dushyant Singh
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Target Surface ◽  
Point Of View ◽  
Nozzle Diameter ◽  
Round Jet

The numerical analysis for the round jet impingement over a circular cylinder has been carried out. The v2f turbulence model is used for the numerical analysis and compared with the two equation turbulence models from the fluid flow and the heat transfer point of view. Further, the numerical results for the heat transfer with original and modified v2f turbulence model are compared with the experimental results. The nozzle is placed orthogonally to the target surface (heated cylindrical surface). The flow is assumed as the steady, incompressible, three-dimensional and turbulent. The spacing between the nozzle exit and the target surface ranges from 4 to 15 times the nozzle diameter. The Reynolds number based on the nozzle diameter ranges from 23,000 to 38,800. From the heat transfer results, the modified v2f turbulence model is better as compared to the other turbulence models. The modified v2f turbulence model has the least error for the numerical Nusselt number at the stagnation point and wall jet region.

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.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

2014 ◽  
Vol 30 (6) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Moshizi ◽  
M. H. Nakhaei ◽  
M. J. Kermani ◽  
A. Madadi
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Streamline Curvature ◽  
Sst Turbulence Model ◽  
Stator Blade ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

Aero-Thermal Study of the Unsteady Flow Field in a Transonic Gas Turbine With Inlet Temperature Distortions

2008 ◽  
Author(s):  
Francesco Martelli ◽  
Paolo Adami ◽  
Simone Salvadori ◽  
Kam S. Chana ◽  
Lionel Castillon
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Inlet Temperature ◽  
Phase Lag ◽  
Turbine Stage ◽  
Inlet Conditions ◽  
University Of Florence ◽  
The University

CFD prediction of the unsteady aero-thermal interaction in the HP turbine stage, with inlet temperature non-uniformity, requires appropriate unsteady modelling and a low diffusive numerical scheme coupled with suitable turbulence models. This maybe referred to as high fidelity CFD. A numerical study has been conducted by the University of Florence in collaboration with ONERA to compare capabilities and limitations of their CFD codes for such flows. The test vehicle used for the investigation is a turbine stage of three-dimensional design from the QinetiQ turbine facility known as MT1. This stage is a high pressure (HP) transonic stage that has an un-shrouded rotor, configured un-cooled with 32 stators and 60 rotor blades. Two different CFD solvers are compared that use different unsteady treatment of the interaction. A reduced count ratio technique has been used by the University of Florence with its code HybFlow, while a phase lag model has been used by ONERA in their code, elsA. Four different inlet conditions have been simulated and compared with a focus on the experimental values provided by QinetiQ in the frame of TATEF and TATEF2 EU 6th Framework projects. The differences in terms of performance parameters and hot fluid redistribution, as well as the time- and pitch-averaged radial distributions on a plane downstream of the rotor blade, have been underlined. Special attention was given to the predictions of rotor blade unsteady pressure and heat transfer rates.

Effects of Different Turbulence Models on Three-Dimensional Unsteady Cavitating Flows in the Centrifugal Pump and Performance Prediction

2019 ◽  
Vol 20 (3-4) ◽  
pp. 487-509 ◽  
Author(s):  
Ahmed Ramadhan Al-Obaidi
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Experimental Results ◽  
Centrifugal Pumps ◽  
Operation Condition ◽  
Sst Model ◽  
And Performance ◽  
Turbulent Models

AbstractIn centrifugal pumps, it is important to select appropriate turbulence model for the numerical simulation in order to obtain reliable and accurate results. In this work, ten turbulence models in 3-D transient simulation for the centrifugal pump are chosen and compared. The pump performance is validated with experimental results. The numerical results reveal that the SST turbulence model was closer to the experimental results in predicting head. In addition, the pressure variation trend for the ten models is very similar which increases and then decreases from the inlet to outlet of the pump along the streamline. The SST k-ω model predicts the performance of the pump was more accurately than other turbulent models. Furthermore, the results also found that the error is the least at design operation condition 300(l/min), which is around 1.98 % for the SST model and 2.14 % and 2.38 % for the LES and transition omega model. Within 7.61 %, the errors at higher flow rate 350(l/min) for SST. The error for SST model is smaller as compared to different turbulent models. For the Realizable k-ɛ model, the errors fluctuate were more high than other models.

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