scholarly journals Simulation of transonic flows through a turbine blade cascade with various prescription of outlet boundary conditions

2018 ◽  
Vol 180 ◽  
pp. 02056
Author(s):  
Petr Louda ◽  
Petr Straka ◽  
Jaromír Příhoda
Keyword(s):  
Boundary Conditions ◽  
Turbine Blade ◽  
Turbulence Model ◽  
Numerical Results ◽  
Transition Model ◽  
Computational Domain ◽  
Transonic Flows ◽  
Blade Cascade ◽  
Experimental Configuration ◽  
Sst Turbulence Model

The contribution deals with the numerical simulation of transonic flows through a linear turbine blade cascade. Numerical simulations were carried partly for the standard computational domain with various outlet boundary conditions by the algebraic transition model of Straka and Příhoda [1] connected with the EARSM turbulence model of Hellsten [2] and partly for the computational domain corresponding to the geometrical arrangement in the wind tunnel by the γ-ζ transition model of Dick et al. [3] with the SST turbulence model. Numerical results were compared with experimental data. The agreement of numerical results with experimental results is acceptable through a complicated experimental configuration.

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.

An Unsteady RANS Transition Model With Dynamic Description of Intermittency

2005 ◽  
Author(s):  
Koen Lodefier ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Turbulent Viscosity ◽  
Suction Side ◽  
Transition Model ◽  
Free Stream Turbulence ◽  
Sst Turbulence Model ◽  
Intermittency Factor ◽  
Dynamic Description

A transition model for describing wake-induced transition is presented. It is based on the SST turbulence model by Menter, with the k–ω part in low-Reynolds form according to Wilcox, and two dynamic equations for intermittency: one for near-wall-intermittency and one for free-stream-intermittency. The total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106a test cascade using experimental results for flow with low free-stream turbulence intensity and transition in separated state and for flow with high free-stream turbulence intensity and transition in attached state. The unsteady results are presented in S–T diagrams of the shape factor and wall shear stress on the suction side. Results show the capability of the model to capture the basics of unsteady transition.

scholarly journals Prediction of the Propeller Performance at Different Reynolds Number Regimes with RANS

2021 ◽  
Vol 9 (10) ◽  
pp. 1115
Author(s):  
João Baltazar ◽  
Douwe Rijpkema ◽  
José Falcão de Campos
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Scale Effects ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transition Model ◽  
Sst Turbulence Model ◽  
Propeller Performance ◽  
Selection Of

In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the selection of the turbulence inlet quantities for different flow regimes is discussed. Then, an analysis of the iterative and discretisation errors is made. This work is followed by an investigation of the predicted propeller flow at variable Reynolds numbers. Finally, the propeller scale-effects and the influence of the turbulence and transition models on the performance prediction are discussed. The variation of the flow regime showed an increase in thrust and decrease in torque for increasing Reynolds number. From the comparison between the turbulence model and the transition model, different flow solutions are obtained for the Reynolds numbers between 105 and 106, affecting the scale-effects prediction.

Subsonic Stall Flutter of a Linear Turbine Blade Cascade Using Experimental and CFD Analysis

2020 ◽  
Author(s):  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Jiri Ira ◽  
Ales Macalka ◽  
Petr Eret ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Leading Edge ◽  
Travelling Wave ◽  
Computational Domain ◽  
Steam Turbines ◽  
Suction Surface ◽  
Blade Cascade ◽  
Stall Flutter

Abstract Stall flutter of long blades influences the operation safety of the large steam turbines in off-design conditions. As angles of attack are typically high, a partial or complete separation of the flow from the blade surface occurs. The prediction of stall flutter of turbine blades is a crucial task in the design and development of modern turbomachinery units and reliable design tools are necessary. In this work, aerodynamic stability of a linear turbine blade cascade is tested experimentally at high angle of attack +15°, Ma = 0.2 and the reduced frequency of 0.38. Controlled flutter testing has been performed in a travelling wave mode approach for the torsion with the motion amplitude of 0.5°. In addition, ANSYS CFX with SST k-ω turbulent model is used for URANS simulations of a full-scale computational domain. A separation bubble formed on suction surface near the leading edge has been found in CFD results for each blade. Excellent agreement between the experimental and numerical results in stability maps has been achieved for this case under investigation. This is encouraging and both experimental and numerical techniques will be tested further.

RANS Modelling of Wake Induced Transition With the Dynamic Intermittency Concept

2006 ◽  
Author(s):  
Koen Lodefier ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Free Stream ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Suction Side ◽  
Navier Stokes ◽  
Transition Model ◽  
Navier Stokes Equations ◽  
Free Stream Turbulence ◽  
Sst Turbulence Model

A transition model for describing wake-induced transition is presented based on the SST turbulence model by Menter and two dynamic equations for intermittency: one for near-wall intermittency and one for free-stream intermittency. In the Navier-Stokes equations, the total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106A test cascade for different levels of inlet free-stream turbulence intensity. The unsteady results are presented in space-time diagrams of shape factor, wall shear stress, momentum thickness and intermittency on the suction side. Results show the capability of the model to capture the physics of unsteady transition. Inevitable shortcomings are also revealed.

Reynolds Stress Turbulence Models for Prediction of Shear Stress Terms in Cross Flow Film Cooling — Numerical Simulation

2002 ◽  
Author(s):  
Aliyar Javadi ◽  
Khodayar Javadi ◽  
Mohamad Taeibi-Rahni ◽  
Mohammad Reza Keimasi
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Film Cooling ◽  
Model Comparison ◽  
Transport Model ◽  
Staggered Grid ◽  
Computational Domain ◽  
Sst Turbulence Model

Reynolds stress models are computationally more complex and time consuming but, have the potential of greater accuracy and wider applicability. Turbulent cross flows and film cooling have highly complex characteristics. In this work, we computationally simulated a three-dimensional, separated hole film cooling problem of flow over a flat plate, using Reynolds stress model (RSM) with wall function and zonal (κ-ε)/(κ-ω) turbulence model (shear stress transport model or SST). The Reynolds number of the jet was 4700. Our computational domain included the space above plate plus the film cooling jet channel. In our numerical simulation, the SIMPLE finite volume method with a non-uniform staggered grid was implemented. Our results were compared with Ajersch et al. experimental and numerical work’s (κ-ε turbulence model). Also, they were compared with Keimasi and Taeibi-Rahani’s numerical simulation work (SST turbulence model). Comparison between the measured and computed results show, that RSM/SST turbulence model in our work has better agreement with experimental data in most cases.

Towards Unsteady Simulation of Combustor-Turbine Interaction Using an Integrated Approach

2015 ◽  
Author(s):  
Félix Raynaud ◽  
Ruud L. G. M. Eggels ◽  
Max Staufer ◽  
Amsini Sadiki ◽  
Johannes Janicka
Keyword(s):  
Boundary Conditions ◽  
Acoustic Waves ◽  
Compressible Flows ◽  
Guide Vane ◽  
Integrated Approach ◽  
Numerical Results ◽  
Combustion Model ◽  
Computational Domain ◽  
Jet Engine ◽  
Flamelet Generated Manifold

In this paper a CFD solver with the ability of dealing with both reacting and compressible flows is developed, so that an integrated simulation of the whole system “combustor and turbine” can be performed. To its validation, the combustor-turbine interaction in a jet engine consisting of a Rolls-Royce combustor together with the first high-pressure turbine stage NGV (Nozzle-Guide-Vane) is studied. The unstructured CFD solver follows a pressure-based approach, using a PISO algorithm (Pressure Implicit with Splitting of Operator) recently extended for compressible flows. In order to allow acoustic waves to leave the computational domain, nonreflecting boundary conditions based on the NSCBC method (Navier-Stokes Characteristic Boundary Conditions) have been implemented. The numerical methods have been coupled with the Flamelet Generated Manifold combustion model (FGM) extended for compressible flows. After successfully verifying the NSCBC implementation, various numerical results describing the combustor-turbine interactions of the jet engine are analyzed and discussed in terms of temperature and total pressure fields with and without NGV. It could be shown that the influence of the NGV on the combustor flow is relatively limited. Differences in the combustor flow field are mainly due to spatial and temporal averaging used for the simulation without NGV to calculate the pressure field at combustor outlet. These numerical results demonstrate the ability of the developed numerical model in its steady computation mode to well capture the evolving flow properties in both combustor and turbine components.

Transition Modelling With the SST Turbulence Model and an Intermittency Transport Equation

2003 ◽  
Author(s):  
Koen Lodefier ◽  
Bart Merci ◽  
Chris De Langhe ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Turbulent Viscosity ◽  
Transition Model ◽  
Bypass Transition ◽  
Model Following ◽  
Sst Model ◽  
Sst Turbulence Model ◽  
Transition Modelling ◽  
Intermittency Factor

A transition model for describing bypass transition is presented. It is based on a two-equations k–ω model and a dynamic equation for intermittency factor. The intermittency factor is a multiplier of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al. [1], the start of transition is computed based on local variables. The choice of the Shear-Stress Transport (SST) model instead of a k–ε model is explained. The quality of the transition model, developed on flat plate test cases, is illustrated for cascades.

Adjoint-Based Optimization Method With Linearized SST Turbulence Model and a Frozen Gamma-Theta Transition Model Approach for Turbomachinery Design

2015 ◽  
Author(s):  
Pengfei Zhang ◽  
Juan Lu ◽  
Zhiduo Wang ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Turbulence Model ◽  
Entropy Generation ◽  
Adjoint System ◽  
Optimization Method ◽  
Adjoint Equations ◽  
Transition Model ◽  
Transition Flow ◽  
Flow Optimization ◽  
Sst Turbulence Model ◽  
Continuous Adjoint

In this paper, based on the grid node coordinates variation and Jacobian Matrices, the turbulent continuous adjoint method with linearized turbulence model is studied and developed to fully account for the variation of turbulent eddy viscosity. The corresponding adjoint equations, boundary conditions and the final sensitivities are formulated with a general expression. To implement the adjoint optimization of the transition flow, a flow solver combining the transition model with the turbulence model is employed, and an adjoint optimization framework with linearized SST turbulence model and a frozen Gamma-Theta transition model is established. In order to choose an appropriate objective for the transition flow optimization, four objectives are studied, including the entropy generation, the total pressure loss coefficient, the field integral of turbulent kinetic energy, the area ratio of transition and turbulent regions to the suciton side. And finally the entropy generation is adopted as the objective. Then, the derivation of the adjoint system for the entropy generation optimization is presented. To demonstrate the validity of the adjoint system for transition flow, four shape optimizations for the bypass transitions and the separation-induced transition are implemented. A 2D isentropic case for bypass transitions is conducted to compares the performances of the fully turbulent adjoint system and the frozen Gamma-Theta transition adjoint system, while the other isothermal case is performed to take the aerodynamic and heat transfer issues into account together. The case of separation-induced transition is performed and also consistent well with its flow mechanism. The four optimization results illustrate the effectiveness of the adjoint system for the transition flow optimization, which can improves the performance of overall cascades and the transition region.

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