NDLI: Predicting Transition in Turbomachinery: Part I — A Review and New Model Development

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Praisner, T. J. Clark, J. P.
Copyright Year	2004
Abstract	Here we report on an effort to include an empirically based transition modeling capability in a RANS solver. Testing of well-known empirical models from literature for both attached- and separated-flow transition against cascade data revealed that the models did not provide enough fidelity for implementation in an airfoil design system. Consequently, a program was launched to develop models that would provide sufficient accuracy for use in an airfoil design system. As a first step in the effort, accurate modeling of freestream turbulence development was identified as a need for any form of transition modeling capability. Additionally, capturing the effects of freestream turbulence on pre-transitional boundary layers was found to have a significant effect on the accuracy of transition modeling. A CFD-supplemented database of experimental cascade cases (57 with attached-flow transition and 47 with separation and turbulent reattachment) was constructed to explore the development of new correlations. Dimensional analyses were performed to guide the work and appropriate non-dimensional parameters were then extracted from CFD predictions of the laminar boundary layers existing on the airfoil surfaces prior to either transition onset or incipient separation. For attached-flow transition, exploration of the database revealed a distinct correlation between local levels of freestream turbulence intensity, turbulence length scale, and momentum-thickness Reynolds number at transition onset. It was found that the correlation could be recast as a ratio of the boundary-layer diffusion time to a time-scale associated with the energy-bearing turbulent eddies. In the case of separated-flow transition, it was found that the length of a separation bubble prior to turbulent re-attachment was a simple function of the local momentum thickness at separation and the overall surface length traversed by a fluid element prior to separation. Both the attached- and separated-flow transition models were implemented into the design system as point-like trips.
Sponsorship	International Gas Turbine Institute
Starting Page	161
Ending Page	174
Page Count	14
File Format	PDF
ISBN	0791841693
DOI	10.1115/GT2004-54108
e-ISBN	0791837394
Volume Number	Volume 4: Turbo Expo 2004
Conference Proceedings	ASME Turbo Expo 2004: Power for Land, Sea, and Air
Language	English
Publisher Date	2004-06-14
Publisher Place	Vienna, Austria
Access Restriction	Subscribed
Subject Keyword	Turbulence Computational fluid dynamics Bearings Cascades (fluid dynamics) Model development Reynolds number Airfoils Momentum Turbomachinery Separation (technology) Diffusion (physics) Flow (dynamics) Modeling Design Bubbles Fluids Databases Reynolds-averaged navier–stokes equations Dimensional analysis Eddies (fluid dynamics) Boundary layers Testing
Content Type	Text
Resource Type	Article

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