Nonlinear Separated Inviscid-Viscous Analysis of Oscillating Cascade Aerodynamics Using an Inverse Integral Method

1999 ◽  
Vol 121 (1) ◽  
pp. 134-144
Author(s):  
J. M. Wolff ◽  
S. Fleeter
Keyword(s):  
Boundary Layer ◽  
Unsteady Flow ◽  
Unsteady Aerodynamics ◽  
Interaction Model ◽  
Separated Flow ◽  
Integral Boundary ◽  
Data Set ◽  
Flow Solver ◽  
Time Marching ◽  
Viscous Solutions

A mathematical model is developed to analyze the unsteady flow through an harmonically oscillating cascade of airfoils, including separated flow. The model incorporates an inverse integral boundary layer solution with the time-marching Euler analysis NPHASE. An embedded composite grid formulation is incorporated, specifically a deforming C-grid embedded in a Cartesian H-grid, thereby simplifying grid generation. To reduce computational requirements, Fourier series unsteady periodic boundary conditions are implemented. The integral turbulent boundary layer model is closed with steady correlations adopted in a quasi-steady manner. To couple the inviscid and viscous solutions, the viscous effect is modeled in the unsteady Euler solution in a quasi-steady manner by a transpiration boundary condition. An isolated airfoil is used to compare the steady interaction model with experimental data. Then a flat plate cascade is used to verify the unsteady flow solver with linear theory predictions. An experimental unsteady aerodynamics data set of a loaded cascade with separated meanflow executing torsional oscillations compared favorably with the analysis. The code is then utilized to study the effect of flow separation on the unsteady aerodynamics.

scholarly journals Nonlinear Separated Inviscid–Viscous Analysis of Oscillating Cascade Aerodynamics Using an Inverse Integral Method

1997 ◽  
Author(s):  
James M. Wolff ◽  
Sanford Fleeter
Keyword(s):  
Boundary Layer ◽  
Unsteady Flow ◽  
Unsteady Aerodynamics ◽  
Interaction Model ◽  
Separated Flow ◽  
Integral Boundary ◽  
Data Set ◽  
Flow Solver ◽  
Time Marching ◽  
Viscous Solutions

A mathematical model is developed to analyze the unsteady flow through an harmonically oscillating cascade of airfoils, including separated flow. The model incorporates an inverse integral boundary layer solution with the time–marching Euler analysis NPHASE. An embedded composite grid formulation is incorporated, specifically a deforming C–grid embedded in a Cartesian H–grid, thereby simplifying grid generation. To reduce computational requirements, Fourier series unsteady periodic boundary conditions are implemented. The integral turbulent boundary layer model is closed with steady correlations adopted in a quasi–steady manner. To couple the inviscid and viscous solutions, the viscous effect is modeled in the unsteady Euler solution in a quasi–steady manner by a transpiration boundary condition. An isolated airfoil is used to compare the steady interaction model with experimental data. Then a flat plate cascade is used to verify the unsteady flow solver with linear theory predictions. An experimental unsteady aerodynamics data set of a loaded cascade with separated meanflow executing torsional oscillations compared favorably with the analysis. The code is then utilized to study the effect of flow separation on the unsteady aerodynamics.

Predicting Bladerow Interactions Using a Multistage Time-Linearized Navier-Stokes Solver

2003 ◽  
Vol 125 (1) ◽  
pp. 25-32 ◽  
Author(s):  
W. Ning ◽  
Y. S. Li ◽  
R. G. Wells
Keyword(s):  
Unsteady Flow ◽  
Frequency Domain ◽  
Test Data ◽  
Computational Efficiency ◽  
Unsteady Flows ◽  
Navier Stokes ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Flow Solver ◽  
Time Marching

A multistage frequency domain (time-linearized/nonlinear harmonic) Navier-Stokes unsteady flow solver has been developed for predicting unsteady flows induced by bladerow interactions. In this paper, the time-linearized option of the solver has been used to analyze unsteady flows in a subsonic turbine test stage and the DLR transonic counter-rotating shrouded propfan. The numerical accuracy and computational efficiency of the time-linearized viscous methods have been demonstrated by comparing predictions with test data and nonlinear time-marching solutions for these two test cases. It is concluded that the development of efficient frequency domain approaches enables unsteady flow predictions to be used in the design cycles to tackle aeromechanics problems.

Predicting Bladerow Interactions Using a Multistage Time-Linearized Navier-Stokes Solver

2002 ◽  
Author(s):  
W. Ning ◽  
Y. S. Li ◽  
R. G. Wells
Keyword(s):  
Unsteady Flow ◽  
Frequency Domain ◽  
Test Data ◽  
Computational Efficiency ◽  
Unsteady Flows ◽  
Navier Stokes ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Flow Solver ◽  
Time Marching

A multistage frequency domain (time-linearized/nonlinear harmonic) Navier-Stokes unsteady flow solver has been developed for predicting unsteady flows induced by bladerow interactions. In this paper, the time-linearized option of the solver has been used to analyze unsteady flows in a subsonic turbine test stage and the DLR transonic counter-rotating shrouded propfan. The numerical accuracy and computational efficiency of the time-linearized viscous methods have been demonstrated by comparing predictions with test data and nonlinear time-marching solutions for these two test cases. It is concluded that the development of efficient frequency domain approaches enables unsteady flow predictions to be used in the design cycles to tackle aeromechanics problems.

Experimental Investigation on the Loss Production Mechanisms in Transitional Boundary Layers

2020 ◽  
Author(s):  
M. Dellacasagrande ◽  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino
Keyword(s):  
Boundary Layer ◽  
Strain Rate ◽  
Boundary Layers ◽  
Separated Flow ◽  
Reduced Order Model ◽  
Mean Flow ◽  
Order Model ◽  
Data Set ◽  
Reduced Order ◽  
Stress Tensors

Abstract The present paper discusses the results of a large experimental data set describing transitional boundary layers. Time resolved Particle Image Velocimetry (PIV) measurements have been adopted to survey the boundary layer developing over a flat plate under prescribed adverse pressure gradients typical of turbomachinery components. The tests have been performed while varying the pressure gradient, the Reynolds number and the inlet free-stream turbulence intensity (FSTI). Two exemplary cases, referring to bypass and separated flow transition, are discussed by means of principal axis analysis and proper orthogonal decomposition (POD). The POD is used to provide statistical representation of the flow structures and to compute the turbulence production (i.e., the mean flow energy dissipation) due to the dynamical features observed for the different transition types. Reduced order model representations of the flow field are provided and their contribution to the total turbulence kinetic energy production is isolated. This analysis is closed by the inspection of the eigenvectors of the strain rate and Reynolds stress tensors. For the separated flow case, it is shown that the eigenvectors of strain rate and shear tensor are almost perfectly aligned downstream of the maximum displacement of the bubble. The reduced order model reconstruction of the Kelvin-Helmholtz shed vortices provides the largest part of the overall TKE production. For the high FSTI induced transition, the eigenvectors of the shear and stress tensors do not have the same direction. The loss generation is related to the local maximum Reynolds normal stress in the streamwise direction, induced by the boundary layer streaks and their breakdown.

Assessment of DES Models for Separated Flow From a Hump in a Turbulent Boundary Layer

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Daniel C. Lyons ◽  
Leonard J. Peltier ◽  
Frank J. Zajaczkowski ◽  
Eric G. Paterson
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Mean Field ◽  
Separated Flow ◽  
Separation Point ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Flow Solver ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

Separated flow past a hump in a turbulent boundary layer is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-averaged Navier–Stokes (RANS) modeling. The geometry is smooth so the separation point is a function of the flow solution. Comparisons to experimental data show that RANS with the Spalart–Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. Analyses motivate that modeled-stress depletion near the separation point contributes to differences observed in the DES variants. The order of accuracy of the flow solver ACUSOLVE is also documented.

Inviscid-Viscous Coupled Solution for Unsteady Flows Through Vibrating Blades: Part 1—Description of the Method

1993 ◽  
Vol 115 (1) ◽  
pp. 94-100 ◽  
Author(s):  
L. He ◽  
J. D. Denton
Keyword(s):  
Boundary Layer ◽  
Numerical Test ◽  
Unsteady Flows ◽  
Boundary Layer Separation ◽  
Displacement Effect ◽  
Integral Boundary ◽  
Time Resolved ◽  
Boundary Layer Equations ◽  
Momentum Integral ◽  
Viscous Solutions

An efficient coupled approach between inviscid Euler and integral boundary layer solutions has been developed for quasi-3-D unsteady flows induced by vibrating blades. For unsteady laminar and turbulent boundary layers, steady correlations are adopted in a quasi-steady way to close the integral boundary layer model. This quasi-steady adoption of the correlations is assessed by numerical test results using a direct solution of the unsteady momentum integral equation. To conduct the coupling between the inviscid and viscous solutions for strongly interactive flows, the unsteady Euler and integral boundary layer equations are simultaneously time-marched using a multistep Runge–Kutta scheme, and the boundary layer displacement effect is accounted for by a first order transpiration model. This time-resolved coupling method converges at conditions with considerable boundary layer separation.

Nonlinear Harmonic Simulations of the Unsteady Aerodynamics of a Fan Stage Section at Windmill

2013 ◽  
Author(s):  
Guillaume Dufour ◽  
Xavier Carbonneau ◽  
Nicolás García Rosa
Keyword(s):  
Unsteady Flow ◽  
Unsteady Aerodynamics ◽  
Separated Flow ◽  
Lower Side ◽  
Flow Angle ◽  
Periodic Movement ◽  
Grid Convergence ◽  
Flow Through ◽  
Convergence Study ◽  
Flow Effects

In the present study, the unsteady flow through the fan stage of a high bypass ratio turbofan at windmill is studied numerically. The Nonlinear Harmonic (NLH) method is applied to a section (at 70 % of the relative span) of the fan stage. First, steady mixing plane simulations at windmill are used to perform a grid convergence study based on the prediction of the massively separated flow occurring on the lower side of both the rotor and stator due to highly negative angles of attack. The unsteadiness of the flow is then examined for the isolated rotor and stator, showing that, for this 2D case, negligible natural unsteady flow effects arise. This supports the use of the NLH method to account only for deterministic unsteady rotor/stator interactions. NLH simulations are then performed, and the influence of the number of harmonics is assessed, based on the analysis of wakes. Contrasting the results with the nominal operating point simulations shows that less harmonics are needed for the windmilling case: this is due to the much larger wake behind the rotor associated to massive separation at windmill, which is more conveniently represented by Fourier series than the sharp narrow wake of the nominal point. Finally, the unsteady flow pattern is examined: the velocity defect of the rotor wakes, which periodically increases the flow angle on the stator, is shown to trigger a periodic movement of the reattachment point at the trailing edge of the stator, associated with vortex shedding from the lower side of the vane.

Inviscid-Viscous Coupled Solution for Unsteady Flows Through Vibrating Blades: Part 1 — Description of the Method

1991 ◽  
Author(s):  
L. He ◽  
J. D. Denton
Keyword(s):  
Boundary Layer ◽  
Numerical Test ◽  
Unsteady Flows ◽  
Boundary Layer Separation ◽  
Displacement Effect ◽  
Integral Boundary ◽  
Time Resolved ◽  
Boundary Layer Equations ◽  
Momentum Integral ◽  
Viscous Solutions

An efficient coupled approach between inviscid Euler and integral boundary layer solutions has been developed for quasi 3-D unsteady flows induced by vibrating blades. For unsteady laminar and turbulent boundary layers, steady correlations are adopted in a quasi-steady way to close the integral boundary layer model. This quasi-steady adoption of the correlations is assessed by numerical test results using a direct solution of the unsteady momentum integral equation. To conduct the coupling between the inviscid and viscous solutions for strongly interactive flows, the unsteady Euler and integral boundary layer equations are simultaneously time-marched using a multi-step Runge-Kutta scheme, and the boundary layer displacement effect is accounted for by a first order transpiration model. This time-resolved coupling method converges at conditions with considerable boundary layer separation.

Sign in / Sign up

Export Citation Format

Share Document