Unsteady Navier-Stokes Simulation of a Transonic Flutter Cascade Near-Stall Conditions Applying Algebraic Transition Models

2005 ◽  
Vol 128 (3) ◽  
pp. 474-483 ◽  
Author(s):  
Hans Thermann ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Strong Shock ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Transonic Compressor ◽  
Transition Models ◽  
Operating Points

Due to the trend in the design of modern aeroengines to reduce weight and to realize high pressure ratios, fan and first-stage compressor blades are highly susceptible to flutter. At operating points with transonic flow velocities and high incidences, stall flutter might occur involving strong shock-boundary layer interactions, flow separation, and oscillating shocks. In this paper, results of unsteady Navier-Stokes flow calculations around an oscillating blade in a linear transonic compressor cascade at different operating points including near-stall conditions are presented. The nonlinear unsteady Reynolds-averaged Navier-Stokes equations are solved time accurately using implicit time integration. Different low-Reynolds-number turbulence models are used for closure. Furthermore, empirical algebraic transition models are applied to enhance the accuracy of prediction. Computations are performed two dimensionally as well as three dimensionally. It is shown that, for the steady calculations, the prediction of the boundary layer development and the blade loading can be substantially improved compared with fully turbulent computations when algebraic transition models are applied. Furthermore, it is shown that the prediction of the aerodynamic damping in the case of oscillating blades at near-stall conditions can be dependent on the applied transition models.

Unsteady Navier-Stokes Simulation of a Transonic Flutter Cascade Near Stall Conditions Applying Algebraic Transition Models

2005 ◽  
Author(s):  
Hans Thermann ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Strong Shock ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Transonic Compressor ◽  
Transition Models ◽  
Operating Points

Due to the trend in the design of modern aeroengines to reduce weight and to realize high pressure ratios, fan and first stage compressor blades are highly susceptible to flutter. At operating points with transonic flow velocities and high incidences stall flutter might occur involving strong shock-boundary layer interactions, flow separation and oscillating shocks. In this paper, results of unsteady Navier-Stokes flow calculations around an oscillating blade in a linear transonic compressor cascade at different operating points including near stall conditions are presented. The nonlinear unsteady Reynolds-averaged Navier-Stokes equations are solved time-accurately using implicit time-integration. Different Low-Reynolds-Number turbulence models are used for closure. Furthermore, empirical algebraic transition models are applied to enhance the accuracy of prediction. Computations are performed two-dimensionally as well as three-dimensionally. It is shown that, for the steady calculations, the prediction of the boundary layer development and the blade loading can be substantially improved compared with fully turbulent computations when algebraic transition models are applied. Furthermore, it is shown that the prediction of the aerodynamic damping in the case of oscillating blades at near stall conditions can be dependent on the applied transition models.

The Impact of Viscous Effects on the Aerodynamic Damping of Vibrating Transonic Compressor Blades—A Numerical Study

2000 ◽  
Vol 123 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Bjo¨rn Gru¨ber ◽  
Volker Carstens
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Viscous Effects ◽  
Aerodynamic Forces ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
The Impact

A parametric study which investigates the influence of viscous effects on the damping behavior of vibrating compressor cascades is presented here. To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects. The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model. An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behavior is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.

scholarly journals Viscous Flow Computations in Turbomachine Cascades

1990 ◽  
Author(s):  
P.-A. Chevrin ◽  
C. Vuillez
Keyword(s):  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Compressor Cascade ◽  
Navier Stokes Equations ◽  
Transonic Compressor ◽  
Different Types ◽  
Time Marching ◽  
Transonic Turbine

Accurate prediction of the flow in turbomachinery requires numerical solution of the Navier-Stokes equations. A two-dimensional Navier-Stokes solver developed at ONERA for the calculation of the flow in turbine and compressor cascades was adapted at SNECMA to run on different types of grid. The solver uses an explicit, time-marching, finite-volume technique, with a multigrid acceleration scheme. A multi-domain approach is used to handle difficulties due to the geometry of the flow. An H-C grid was used in the calculations. Two turbulence models, based on the mixing length approach, were used. The flow in a transonic compressor cascade, a subsonic and a transonic turbine cascade were computed. Comparison with experiments is presented.

The Impact of Viscous Effects on the Aerodynamic Damping of Vibrating Transonic Compressor Blades — A Numerical Study

2000 ◽  
Author(s):  
Björn Grüber ◽  
Volker Carstens
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Viscous Effects ◽  
Aerodynamic Forces ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
The Impact

A parametric study which investigates the influence of viscous effects on the damping behaviour of vibrating compressor cascades is presented here. To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects. The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model. An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behaviour is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.

scholarly journals Validation of atmospheric boundary layer turbulence model by on-site measurements

2010 ◽  
Vol 14 (1) ◽  
pp. 199-207 ◽  
Author(s):  
Zarko Stevanovic ◽  
Nikola Mirkov ◽  
Zana Stevanovic ◽  
Andrijana Stojanovic
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Linear Models ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Boundary Layer Turbulence ◽  
Askervein Hill ◽  
Neutral Conditions

Modeling atmosperic boundary layer with standard linear models does not sufficiently reproduce wind conditions in complex terrain, especially on leeward sides of terrain slopes. More complex models, based on Reynolds averaged Navier-Stokes equations and two-equation k-? turbulence models for neutral conditions in atmospheric boundary layer, written in general curvilinear non-orthogonal co-ordinate system, have been evaluated. In order to quantify the differences and level of accuracy of different turbulence models, investigation has been performed using standard k-? model without additional production terms and k-? turbulence models with modified set of model coefficients. The sets of full conservation equations are numerically solved by computational fluid dynamics technique. Numerical calculations of turbulence models are compared to the reference experimental data of Askervein hill measurements.

Numerical Simulation of the Boundary Layer Transition in Turbomachinery Flows

2001 ◽  
Author(s):  
Hans Thermann ◽  
Michael Müller ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Separated Flow ◽  
Suction Side ◽  
Boundary Layer Transition ◽  
Test Cases ◽  
Compressor Cascade ◽  
Layer Transition ◽  
Transonic Compressor ◽  
Transition Models ◽  
Transition Modeling

The objective of the presented work is to investigate models which simulate boundary layer transition in turbomachinery flows. This study focuses on separated-flow transition. Computations with different algebraic transition models are performed three-dimensionally using an implicit Navier-Stokes flow solver. Two different test cases have been chosen for this investigation: First, a linear transonic compressor cascade, and second an annular subsonic compressor cascade. Both test cases show three-dimensional flow structures with large separations at the side-walls. Additionally, laminar separation bubbles can be observed on the suction and pressure side of the blades of the annular subsonic cascade whereas a shock-induced separation can be found on the suction side of the blades of the linear transonic cascade. Computational results are compared with experiments and the effect of transition modeling is analyzed. It is shown that the prediction of the boundary layer development can be substantially improved compared to fully turbulent computations when algebraic transition models are applied.

Flow-Induced Vibration Analyses of Stator and Moving Rotor Cascade With Viscosity Effects

2007 ◽  
Author(s):  
Dong-Hyun Kim ◽  
Se-Won Oh ◽  
Yu-Sung Kim ◽  
Oung Park
Keyword(s):  
Stokes Equations ◽  
Turbulence Models ◽  
Dynamic Responses ◽  
Navier Stokes ◽  
Implicit Time ◽  
Flow Induced Vibration ◽  
Fluid Structure ◽  
Fully Implicit ◽  
Direct Integration Method ◽  
The Time Domain

In this study, nonlinear dynamic responses considering fluid-structure interactions have been conducted for a stator-rotor cascade configuration. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed dynamic responses and flutter stability of general stator-rotor cascade configurations. Especially, effects of relative motions of the rotor cascade with respect to the stator cascade are considered in numerical analyses. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming techniques. Unsteady, Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras and SST k-ω turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is typically used for computing the coupled aeroelastic governing equations of the cascade fluid-structure interaction problems. Detailed dynamic aeroelastic responses for different stator-rotor interaction flow conditions are presented to show the physical vibration characteristics in the time-domain.

Development of a 3D Navier Stokes Solver for Application to all Types of Turbomachinery

1988 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Equations Of Motion ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Basic Algorithm ◽  
Navier Stokes Equations ◽  
Transonic Compressor ◽  
Stage Of Development ◽  
Code Performance

This paper describes the current stage of development of a code aimed at solving the 3D Navier-Stokes equations in any type of turbomachinery geometry. The basic algorithm time marches the fully 3D unsteady equations of motion expressed in finite volume form with a two step explicit / one step implicit method. Full multigrid acceleration is used to reduce solution time and maintain code performance on fine meshes. Turbulence modelling is via mixing-length closure and the widely used Baldwin-Lomax model. The generality and robustness of the code is demonstrated by application to five different test cases, three axial and two radial configurations. Also included is a grid independence study which demonstrates near grid independent solutions for transonic compressor cascade flow (albeit with the actual result subject to transition modelling constraints). For two of the axial cases (transonic compressor in cascade, secondary flow in a high speed compressor) and one radial case (Eckardt high speed impellor) sufficient mesh is employed for the predictions to be essentially quantitative. The other two cases (radial inflow turbine with clearance and compressor stator with hub clearance) are really simulations rather than predictions, but are included as the flows are novel and provide much physical insight.

k ‐ ϵ Model for the Atmospheric Boundary Layer Under Various Thermal Stratifications

2005 ◽  
Vol 127 (4) ◽  
pp. 438-443 ◽  
Author(s):  
Cédric Alinot ◽  
Christian Masson
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Similarity Theory ◽  
Turbulence Models ◽  
Boussinesq Approximation ◽  
Momentum Equation ◽  
Navier Stokes ◽  
Production Term

This paper presents a numerical method for predicting the atmospheric boundary layer under stable, neutral, or unstable thermal stratifications. The flow field is described by the Reynolds’ averaged Navier-Stokes equations complemented by the k‐ϵ turbulence model. Density variations are introduced into the momentum equation using the Boussinesq approximation, and appropriate buoyancy terms are included in the k and ϵ equations. An original expression for the closure coefficient related to the buoyancy production term is proposed in order to improve the accuracy of the simulations. The resulting mathematical model has been implemented in FLUENT. The results presented in this paper include comparisons with respect to the Monin-Obukhov similarity theory, measurements, and earlier numerical solutions based on k‐ϵ turbulence models available in the literature. It is shown that the proposed version of the k‐ϵ model significantly improves the accuracy of the simulations for the stable atmospheric boundary layer. In neutral and unstable thermal stratifications, it is shown that the version of the k‐ϵ models available in the literature also produce accurate simulations.

Boundary layer investigations on a highly loaded transonic compressor cascade with shock/laminar boundary layer interactions

2003 ◽  
Vol 217 (4) ◽  
pp. 349-356 ◽  
Author(s):  
L Hilgenfeld ◽  
P Cardamone ◽  
L Fottner
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Suction Side ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Flow Solver ◽  
Transonic Compressor ◽  
Shock System ◽  
The One ◽  
Highly Loaded

Detailed experimental and numerical investigations of the flowfield and boundary layer on a highly loaded transonic compressor cascade were performed at various Mach and Reynolds numbers representative of real turbomachinery conditions. The emerging shock system interacts with the laminar boundary layer, causing shock-induced separation with turbulent reattachment. Steady two-dimensional calculations have been performed using the Navier—Stokes solver TRACE-U. The flow solver employs a modified version of the one-equation Spalart—Allmaras turbulence model coupled with a transition correlation by Abu-Ghannam/Shaw in the formulation by Drela. The computations reproduce well the experimental results with respect to the profile pressure distribution and the location of the shock system. The transitional behaviour of the boundary layer and the profile losses in the wake are properly predicted as well, except for the highest Mach number tested, where large separated regions appear on the suction side.

Sign in / Sign up

Export Citation Format

Share Document