scholarly journals Advances in Unsteady Boundary Layer Transition Research, Part I: Theory and Modeling

2003 ◽  
Vol 9 (1) ◽  
pp. 1-9
Author(s):  
M. T. Schobeiri ◽  
L. Wright
Keyword(s):  
Boundary Layer ◽  
Turbine Blades ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Test Facility ◽  
Transition Model ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

This two-part article presents recent advances in boundary layer research that deal with the unsteady boundary layer transition modeling and its validation. A new unsteady boundary layer transition model was developed based on a universal unsteady intermittency function. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the transition model, an inductive approach was implemented; the approach was based on the results of comprehensive experimental and theoretical studies of unsteady wake flow and unsteady boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under a periodic unsteady wake flow, where the frequency of the periodic unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for unsteady boundary layer investigations. The analysis of the experiment's results and comparison with the model's prediction confirm the validity of the model and its ability to predict accurately the unsteady boundary layer transition.

scholarly journals Advances in Unsteady Boundary Layer Transition Research, Part II: Experimental Verification

2003 ◽  
Vol 9 (1) ◽  
pp. 11-22 ◽  
Author(s):  
M. T. Schobeiri ◽  
L. Wright
Keyword(s):  
Boundary Layer ◽  
Turbine Blades ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Test Facility ◽  
Experimental Investigations ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

This two-part article presents recent advances in boundary layer research into the unsteady boundary layer transition modeling and its validation. This, Part II, deals with the results of an inductive approach based on comprehensive experimental and theoretical studies of unsteady wake flow and unsteady boundary layer flow. The experiments were performed on a curved plate at a zero streamwise pressure gradient under periodic unsteady wake flow, in which the frequency of the periodic unsteady flow was varied. To validate the model, systematic experimental investigations were performed on the suction and pressure surfaces of turbine blades integrated into a high-subsonic cascade test facility, which was designed for unsteady boundary layer investigations. The analysis of the experiment's results and comparison with the model's prediction confirm the validity of the model and its ability to predict accurately the unsteady boundary layer transition.

Modeling Unsteady Boundary Layer Transition on a Curved Plate Under Periodic Unsteady Flow Conditions: Aerodynamic and Heat Transfer Investigations

1999 ◽  
Vol 121 (1) ◽  
pp. 88-97 ◽  
Author(s):  
P. Chakka ◽  
M. T. Schobeiri
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Transition Model ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

A boundary layer transition model is developed that accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the model, comprehensive unsteady boundary layer and heat transfer experimental investigations are conducted. The experiments are performed on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow, where the frequency of the periodic unsteady flow is varied. The analysis of the time-dependent velocities, turbulence intensities, and turbulence intermittencies has identified three distinct quantities as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition model presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting velocity profiles and the heat transfer coefficients are compared with the experimental data.

scholarly journals Modeling Unsteady Boundary Layer Transition on a Curved Plate Under Periodic Unsteady Flow Conditions: Aerodynamic and Heat Transfer Investigations

1997 ◽  
Author(s):  
P. Chakka ◽  
M. T. Schobeiri
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Transition Model ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

A boundary layer transition model is developed that accounts for the effects of periodic unsteady wake flow on the boundary layer transition. To establish the model, comprehensive unsteady boundary layer and heat transfer experimental investigations are conducted. The experiments are performed on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow, where the frequency of the periodic unsteady flow is varied. The analysis of the time dependent velocities, turbulence intensities, and turbulence intermittencies has identified three distinct quantities as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition model presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting velocity profiles and the heat transfer coefficients are compared with the experimental data.

Intermittency Based Unsteady Boundary Layer Transition Modeling: Implementation Into Navier-Stokes Equations

2005 ◽  
Author(s):  
M. T. Schobeiri
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Navier Stokes ◽  
Transition Model ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Navier Stokes Equations ◽  
Unsteady Wake

This paper presents recent advances in boundary layer research that deal with an intermittency based unsteady boundary layer transition model and its implementation into the Reynolds averaged Navier-Stokes equations (RANS). RANS equations are conditioned to include the ensemble averaged unsteady intermittency function. The unsteady boundary layer transition model is based on a universal unsteady intermittency function developed earlier. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. The transition model is the result of an inductive approach analyzing the unsteady data obtained by experiments on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow. To validate this model, systematic experimental investigations were conducted on the suction and pressure surfaces of turbine blades that were integrated into a turbine cascade test facility, which was designed for unsteady boundary layer investigations. This model is implemented into the above mentioned conditioned RANS-equations and calculation results are presented.

scholarly journals Unsteady Wake Effects on Boundary Layer Transition and Heat Transfer Characteristics of a Turbine Blade

1998 ◽  
Author(s):  
M. T. Schobeiri ◽  
P. Chakka ◽  
K. Pappu
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbine Blade ◽  
Boundary Layer Transition ◽  
Wake Flow ◽  
Transition Model ◽  
Heat Transfer Characteristics ◽  
Layer Transition ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

Effect of unsteady wakes on aerodynamic and heat transfer characteristics of a turbine blade in a cascade were analyzed both experimentally and theoretically. Comprehensive aerodynamic data were collected for different wake passing frequencies that are typical of turbomachinery. Hot-wire probes were used for collection of boundary layer data on suction and pressure surfaces of the turbine blade. Heat transfer measurements were made using steady liquid crystal techniques. Boundary layer data were analyzed through intermittency function to get insight into the transition process under unsteady wake flow conditions. The experimental and theoretical results presented in this paper confirm the general validity of the unsteady boundary layer transition model developed by Chakka and Schobeiri (1997). This model is based on a relative intermittency function, which accounts for the effects of periodic unsteady wake flow on the boundary layer transition. Three distinct quantities are identified as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition analysis presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting heat transfer coefficients are compared with the experimental data.

scholarly journals Boundary-Layer Transition Regions on Turbine Blade Suction Surfaces

1984 ◽  
Author(s):  
G. Roberts ◽  
A. Brown
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Boundary Layer Transition ◽  
Transition Model ◽  
Computer Programme ◽  
Layer Transition

This paper describes the results of an experimental investigation into extended boundary-layer transition regions on suction surfaces of four sets of turbine blades in a cascade rig. A transition model is proposed which is tested with some success in a modified version of STAN5, a boundary-layer computer programme.

Numerical Investigation of Unsteady Boundary Layer Transition on a Dynamically Pitching Rotor

2021 ◽  
Author(s):  
Jared A. Carne ◽  
James G. Coder
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Test Facility ◽  
Unsteady Boundary Layer ◽  
Layer Transition ◽  
Transition Prediction ◽  
Turbulent Transition ◽  
Transition Modeling ◽  
German Aerospace ◽  
Laminar Turbulent Transition

Predictions of unsteady boundary layer transition are performed on a four-bladed rotor in axial inflow using a computational fluid dynamics approach. The configuration is based on experiments performed at the German Aerospace Center (DLR) in the 1.6-m × 3.4-m wind tunnel in the rotor test facility (RTG). Simulations are performed using the NASA OVERFLOW 2.3 solver with hybrid RANS/LES and laminar turbulent transition modeling. Solutions are based on a hover tip Mach number of 0.143 with prescribed cyclic pitching conditions. Computational methods and grid generation are described. The rotor flow field is analyzed, and the effect of transition modeling on unsteady boundary layer transition prediction is assessed. Laminar-turbulent transition predictions and rotor performance are compared to experimental measurements obtained at the DLR RTG. A study of sensitivity was performed on freestream turbulence intensity to investigate its effect on predicted rotor transition.

scholarly journals On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

2005 ◽  
Vol 127 (3) ◽  
pp. 503-513 ◽  
Author(s):  
Meinhard T. Schobeiri ◽  
Burak Öztürk ◽  
David E. Ashpis
Keyword(s):  
Boundary Layer ◽  
Test Section ◽  
Separation Zone ◽  
Wake Flow ◽  
Unsteady Boundary Layer ◽  
Flow Conditions ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05°, which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

scholarly journals On the Physics of the Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions

2003 ◽  
Author(s):  
Meinhard T. Schobeiri ◽  
Burak O¨ztu¨rk ◽  
David E. Ashpis
Keyword(s):  
Boundary Layer ◽  
Test Section ◽  
Separation Zone ◽  
Wake Flow ◽  
Unsteady Boundary Layer ◽  
Flow Conditions ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Unsteady Wake ◽  
Unsteady Wake Flow

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05°, which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re = 50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

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