scholarly journals Numerical Investigation of the Turbulent Wake-Boundary Interaction in a Translational Cascade of Airfoils and Flat Plate

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4478
Author(s):  
Xiaodong Ruan ◽  
Xu Zhang ◽  
Pengfei Wang ◽  
Jiaming Wang ◽  
Zhongbin Xu
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
Fluid Flows ◽  
Leading Edge ◽  
Transition Model ◽  
Boundary Interaction ◽  
Positive Vorticity ◽  
Boundary Layer Interaction ◽  
Rotor Stator Interaction ◽  
Layer Velocity

Rotor stator interaction (RSI) is an important phenomenon influencing performances in the pump, turbine, and compressor. In this paper, the correlation-based transition model is used to study the RSI phenomenon between a translational cascade of airfoils and a flat plat. A comparison was made between computational results and experimental results. The computational boundary layer velocity is in reasonable agreement with the experimental velocity. The thickness of boundary layer decreases as the RSI frequency increases and it increases as the fluid flows downstream. The spectral plots of velocity fluctuations at leading edge x/c = 2 under RSI partial flow condition f = 20 Hz and f = 30 Hz are dominated by a narrowband component. RSI frequency mainly affects the turbulence intensity in the freestream region. However, it has little influence on the turbulence intensity of boundary layer near the wall. A secondary vortex is induced by the wake–boundary layer interaction and it leads to the formation of a thickened laminar boundary layer. The negative-vorticity wake also facilitates the formation of a thickened boundary layer while the positive-vorticity wake has a similar effect, like a calmed region which makes the boundary layer thinner.

Characterization of Shock Wave–Endwall Boundary Layer Interactions in a Transonic Compressor Rotor

1988 ◽  
Vol 110 (3) ◽  
pp. 386-392 ◽  
Author(s):  
D. C. Rabe ◽  
A. J. Wennerstrom ◽  
W. F. O’Brien
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Air Force ◽  
Leading Edge ◽  
Transonic Compressor ◽  
Laser Measurements ◽  
Compressor Rotor ◽  
Boundary Layer Interaction ◽  
Air Force Base

The passage shock wave–endwall boundary layer interaction in a transonic compressor was investigated with a laser transit anemometer. The transonic compressor used in this investigation was developed by the General Electric Company under contract to the Air Force. The compressor testing was conducted in the Compressor Research Facility at Wright-Patterson Air Force Base, OH. Laser measurements were made in two blade passages at seven axial locations from 10 percent of the axial blade chord in front of the leading edge to 30 percent of the axial blade chord into the blade passage. At three of these axial locations, laser traverses were taken at different radial immersions. A total of 27 different locations were traversed circumferentially. The measurements reveal that the endwall boundary layer in this region is separated from the core flow by what appears to be a shear layer where the passage shock wave and all ordered flow seem to end abruptly.

Experimental Study of the Unsteady Boundary Layer Behavior on a Turbine Cascade

1995 ◽  
Author(s):  
M. T. Schobeiri ◽  
K. Pappu ◽  
L. Wright
Keyword(s):  
Boundary Layer ◽  
Turbulence Intensity ◽  
Large Scale ◽  
Turbine Cascade ◽  
Unsteady Boundary Layer ◽  
Unsteady Wake ◽  
Layer Velocity ◽  
Layer Behavior ◽  
Velocity Turbulence ◽  
Further Development

The unsteady boundary layer behavior on a turbine cascade is experimentally investigated and the results are presented in this paper. To perform a detailed study on unsteady cascade aerodynamics and heat transfer, a new large-scale, high-subsonic research facility for simulating the periodic unsteady flow has been developed. It is capable of sequentially generating up to four different unsteady inlet flow conditions that lead to four different passing frequencies, wake structures, and freestream turbulence intensities. For a given Reynolds number, three different unsteady wake formations are utilized. Detailed unsteady boundary layer velocity, turbulence intensity, and pressure measurements are performed along the suction and pressure surfaces of one blade. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity.

Interactions of Separation Bubble With Oncoming Wakes by Large-Eddy Simulation

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
S. Sarkar ◽  
Harish Babu ◽  
Jasim Sadique
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Separation Bubble ◽  
Leading Edge ◽  
Constant Thickness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Past A Cylinder ◽  
Rotor Stator Interaction

The unsteady flow physics and heat transfer characteristics due to interactions of periodic passing wakes with a separated boundary layer are studied using large-eddy simulation (LES). A series of airfoils of constant thickness with rounded leading edge are employed to obtain the separated boundary layer. Wake data extracted from precursor LES of flow past a cylinder are used to replicate a moving bar that generates wakes in front of a cascade (in this case, an infinite row of the model airfoils). This setup is a simplified representation of the rotor–stator interaction in turbomachinery. With a uniform inlet, the laminar boundary layer separates near the leading edge, undergoes transition due to amplification of disturbances, becomes turbulent, and finally reattaches forming a separation bubble. In the presence of oncoming wakes, the characteristics of the separated boundary layer have changed and the impinging wakes are found to be the mechanism affecting the reattachment. Phase-averaged results illustrate the periodic behavior of both flow and heat transfer. Large undulations in the phase-averaged skin friction and Nusselt number distributions can be attributed to the excitation of the boundary layer by convective wakes forming coherent vortices, which are being shed and convect downstream. Further, the transition of the separated boundary layer during the wake-induced path is governed by a mechanism that involves the convection of these vortices followed by increased fluctuations, where viscous effect is substantial.

Interactions of Separation Bubble With Oncoming Wakes by LES

2011 ◽  
Author(s):  
S. Sarkar ◽  
Jasim Sadique
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shear Layer ◽  
Separation Bubble ◽  
Leading Edge ◽  
Flat Plates ◽  
Flow Past A Cylinder ◽  
Periodic Behaviour ◽  
Rotor Stator Interaction ◽  
Multiple Bubbles

The unsteady flow physics and heat transfer characteristics due to interactions of periodic passing wakes with a separated boundary layer are studied with the help of Large-eddy simulations (LES). A flat plate with a semicircular leading edge is employed to obtain the separated boundary layer. Wake data extracted from precursor LES of flow past a cylinder are used to replicate a moving bar that generates wakes in front of a cascade (in this case an infinite row of flat plates). This setup is a simplified representation of the rotor-stator interaction in turbomachinery. With a uniform inlet, the laminar boundary layer separates near the leading edge, undergoes transition due to amplification of the disturbances, becomes turbulent and finally reattaches forming a bubble. In the presence of oncoming wakes, the characteristics of the separated layer have changed and the impinging wakes are found to be the mechanism affecting the reattachment. Phase averaged results illustrate the periodic behaviour of both flow and heat transfer. Large undulations in the phase-averaged skin friction and Nusselt number distributions can be attributed to the excitation of separated shear layer by convective wakes forming coherent vortices, which are being shed and convect downstream. This interaction also breaks the bubble into multiple bubbles. Further, the transition of the shear layer during the wake-induced path is governed by a mechanism that involves the convection of these vortices followed by increased fluctuations.

Hybrid-Grid Simulation of Unsteady Wake-Boundary Layer Interaction on a High Lift Low Pressure Turbine Airfoil

2007 ◽  
Author(s):  
Hong Yang ◽  
Thomas Roeber ◽  
Dragan Kozulovic
Keyword(s):  
Boundary Layer ◽  
Vortex Street ◽  
Transition Model ◽  
Mode Transition ◽  
Suction Surface ◽  
High Lift ◽  
Unsteady Wake ◽  
Boundary Layer Interaction ◽  
Hybrid Grid ◽  
Multi Mode

The unsteady wake-boundary layer interaction on a high lift low pressure (LP) turbine airfoil T106C was investigated by applying the hybrid structured-unstructured RANS solver developed at the DLR. The simulation domain was split into two parts: a translational one with moving bars and a stationary one with turbine airfoils, and in between was a sliding mesh interface. An unstructured grid was generated around the moving bars with particular clustering along the wake path to have a sharp resolution of the shedding vortex street, whereas the stationary blade airfoil subject to the incoming wakes was meshed with a block-structured grid to ease the implementation of the laminar-turbulent transition model around the airfoil. The Wilcox two-equation k-ω turbulence model was applied in conjunction with a multi-mode transition model developed by the authors taking into account several modes of transition, namely natural/bypass, separated-flow and wake-induced transition modes. In this paper, the hybrid-grid modeling is first validated against measurements from the VKI, and then the unsteady flow mechanisms associated with the shedding vortices and the multi-mode transition on the blade airfoil are analyzed. Furthermore, the quasi-steady mixing-plane model on the hybrid grids is also assessed by a comparison with the time-mean of the unsteady state solutions. In particular, different chopping to the incoming vortex street at the blade leading edge is found to have different effects on the separation and transition over the blade suction surface. At the end a composite picture of the boundary-layer development over the suction surface is summarized.

Simulation of blunt-fin-induced shock-wave and turbulent boundary-layer interaction

1985 ◽  
Vol 154 ◽  
pp. 163-185 ◽  
Author(s):  
Ching-Mao Hung ◽  
Pieter G. Buning
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Flat Plate ◽  
High Speed ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Layer Interaction ◽  
Boundary Layer Interaction

The Reynolds-averaged Navier–Stokes equations are solved numerically for supersonic flow over a blunt fin mounted on a flat plate. The fin shock causes the boundary layer to separate, which results in a complicated, three-dimensional shock-wave and boundary-layer interaction. The computed results are in good agreement with the mean static pressure measured on the fin and the flat plate. The main features, such as peak pressure on the fin leading edge and a double peak on the plate, are predicted well. The role of the horseshoe vortex is discussed. This vortex leads to the development of high-speed flow and, hence, low-pressure regions on the fin and the plate. Different thicknesses of the incoming boundary layer have been studied. Varying the thicknesses by an order of magnitude shows that the size of the horseshoe vortex and, therefore, the spatial extent of the interaction are dominated by inviscid flow and only weakly dependent on the Reynolds number. Coloured graphics are used to show details of the interaction flow field.

Predicting Transitional Separation Bubbles

2004 ◽  
Vol 127 (3) ◽  
pp. 497-501
Author(s):  
John A. Redford ◽  
Mark W. Johnson
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Transition Process ◽  
Test Cases ◽  
Transition Model ◽  
Flow Transition ◽  
Free Stream Turbulence ◽  
Attached Flow

This paper describes the modifications made to a successful attached flow transition model to produce a model capable of predicting both attached and separated flow transition. This transition model is used in combination with the Fluent CFD software, which is used to compute the flow around the blade assuming that it remains entirely laminar. The transition model then determines the start of transition location and the development of the intermittency. These intermittency values weight the laminar and turbulent boundary layer profiles to obtain the resulting transitional boundary layer parameters. The ERCOFTAC T3L test cases are used to validate the predictions. The T3L blade is a flat plate with a semi-circular leading edge, which results in the formation of a separation bubble the length of which is strongly dependent on the transition process. Predictions were performed for five T3L test cases for differing free-stream turbulence levels and Reynolds numbers. For the majority of these test cases the measurements were accurately predicted.

Predicting Transitional Separation Bubbles

2004 ◽  
Author(s):  
John A. Redford ◽  
Mark W. Johnson
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Transition Process ◽  
Reynolds Numbers ◽  
Test Cases ◽  
Transition Model ◽  
Flow Transition ◽  
Attached Flow

This paper describes the modifications made to a successful attached flow transition model to produce a model capable of predicting both attached and separated flow transition. This transition model is used in combination with the Fluent CFD software, which is used to compute the flow around the blade assuming that it remains entirely laminar. The transition model then determines the start of transition location and the development of the intermittency. These intermittency values weight the laminar and turbulent boundary layer profiles to obtain the resulting transitional boundary layer parameters. The ERCOFTAC T3L test cases are used to validate the predictions. The T3L blade is a flat plate with a semi-circular leading edge, which results in the formation of a separation bubble the length of which is strongly dependent on the transition process. Predictions were performed for five T3L test cases for differing freestream turbulence levels and Reynolds numbers. For the majority of these test cases the measurements were accurately predicted.

Modelling Unsteady Transition Effects in an Axial Compressor

2008 ◽  
Author(s):  
Adam D. Beevers ◽  
Joao Amaral-Teixeira ◽  
Roger Wells
Keyword(s):  
Boundary Layer ◽  
Axial Compressor ◽  
Leading Edge ◽  
Transition Process ◽  
Transition Model ◽  
Velocity Defect ◽  
Commercial Code ◽  
Stator Blade ◽  
Transition Effects ◽  
Unsteady Effects

Wake induced transition is simulated at mid-span on a C4 stator blade in a 1.5 stage low speed axial compressor using the CFX γ – θ transition model. IGV and rotor wake inputs were created from a succession of Fourier series produced from experimental data. The purpose of the study was to understand the effectiveness of the γ – θ model implemented in a commercial code to predict the unsteady effects of wake induced transition. The γ – θ transition model was found to predict wake-induced transition and the subsequent calmed region caused by the passing wakes. The wake velocity defect creates conditions within the boundary layer such that the high disturbance energy, which is diffused into the boundary layer at the leading edge from the wake, initiates the transition process. This high disturbance energy travels through the boundary layer directly behind the wake.

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