Boundary-Layer Transition Under the Effect of Compressibility for the Correlation Based Transition Model

2008 ◽  
Author(s):  
Ünver Kaynak ◽  
Emre Gürdamar
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Transition Model ◽  
Layer Transition

Modelling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

2013 ◽  
Author(s):  
Florian Herbst ◽  
Andreas Fiala ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Transition Process ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Layer Transition ◽  
Wall Flows

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJ) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semi-empirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, re-calibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

A Boundary Layer Transition Model

1996 ◽  
Author(s):  
Mark W. Johnson ◽  
Ali H. Ercan
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Transition ◽  
Test Cases ◽  
Length Scale ◽  
Transition Model ◽  
Freestream Turbulence ◽  
Layer Transition ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Turbulent Length Scale

A new boundary layer transition model is presented which relates the velocity fluctuations near the wall to the formation of turbulent spots. A relationship for the near wall velocity frequency spectra is also established, which indicates an increasing bias towards low frequencies as the skin friction coefficient for the boundary layer decreases. This result suggests that the dependence of transition on the turbulent length scale is greatest at low freestream turbulence levels. This transition model is incorporated in a conventional boundary layer integral technique and is used to predict eight of the ERCOFTAC test cases. Three of these test cases are for nominally zero pressure gradient and the remaining five are for a pressure distribution typical of an aft loaded turbine blade. The model is demonstrated to predict the development of the boundary layer through transition reasonably accurately for all the test cases. The sensitivity of start of transition to the turbulent length scale at low freestream turbulence levels is also demonstrated.

Modeling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Florian Herbst ◽  
Andreas Fiala ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Transition Process ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Layer Transition ◽  
Wall Flows

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJs) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semiempirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, recalibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

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.

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.

An Improved Boundary Layer Transition Correlation

1992 ◽  
Author(s):  
Ahmad Fasihfar ◽  
Mark W. Johnson
Keyword(s):  
Boundary Layer ◽  
Signal Processing ◽  
Digital Signal ◽  
Boundary Layer Transition ◽  
Transition Model ◽  
Turbulence Level ◽  
Hot Wire ◽  
Layer Transition ◽  
Transitional Boundary Layer ◽  
The Mean

The influence of pressure gradient and freestream turbulence level on boundary layer transition has been studied experimentally using hot wire instrumentation and digital signal processing and analysis. An established transition correlation and recent transition model were found to give acceptable prediction of the experimental results. The digital system was used to conditionally sample the transitional boundary layer data and hence to determine the mean and fluctuating velocity profiles for the laminar and turbulent parts of the boundary layer separately. The turbulent portions were found to correlate well with fully developed turbulent boundary layer profiles, but the laminar portion profiles deviated considerably from those typical of a laminar boundary layer.

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 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.

Sign in / Sign up

Export Citation Format

Share Document