Predictions of time-resolved flowfields are now commonplace within the gas-turbine industry, and the results of such simulations are often used to make design decisions during the development of new products. Hence it is necessary for design engineers to have a robust method to determine the level of convergence in design predictions. Here we report on a method developed to determine the level of convergence in a predicted flowfield that is characterized by periodic unsteadiness. The method relies on fundamental concepts from digital signal processing including the discrete Fourier transform, cross correlation, and Parseval’s theorem. Often in predictions of vane–blade interaction in turbomachines, the period of the unsteady fluctuations is expected. In this method, the development of time-mean quantities, Fourier components (both magnitude and phase), cross correlations, and integrated signal power are tracked at locations of interest from one period to the next as the solution progresses. Each of these separate quantities yields some relative measure of convergence that is subsequently processed to form a fuzzy set. Thus the overall level of convergence in the solution is given by the intersection of these sets. Examples of the application of this technique to several predictions of unsteady flows from two separate solvers are given. These include a prediction of hot-streak migration as well as more typical cases. It is shown that the method yields a robust determination of convergence. Also, the results of the technique can guide further analysis and∕or post-processing of the flowfield. Finally, the method is useful for the detection of inherent unsteadiness in the flowfield, and as such it can be used to prevent design escapes.
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e-mail: john.clark@pr.wpafb.af.mil
e-mail: eric.grover@pw.utc.com
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October 2007
Research Papers
Assessing Convergence in Predictions of Periodic-Unsteady Flowfields
J. P. Clark,
J. P. Clark
Turbine Branch, Turbine Engine Division, Propulsion Directorate,
e-mail: john.clark@pr.wpafb.af.mil
Air Force Research Laboratory
, Building 18, Room 136D, 1950 5th Street, WPAFB, OH 45433
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E. A. Grover
E. A. Grover
Turbine Aerodynamics,
e-mail: eric.grover@pw.utc.com
United Technologies Pratt & Whitney
, 400 Main Street, M∕S 169-29, East Hartford, CT 06108
Search for other works by this author on:
J. P. Clark
Turbine Branch, Turbine Engine Division, Propulsion Directorate,
Air Force Research Laboratory
, Building 18, Room 136D, 1950 5th Street, WPAFB, OH 45433e-mail: john.clark@pr.wpafb.af.mil
E. A. Grover
Turbine Aerodynamics,
United Technologies Pratt & Whitney
, 400 Main Street, M∕S 169-29, East Hartford, CT 06108e-mail: eric.grover@pw.utc.com
J. Turbomach. Oct 2007, 129(4): 740-749 (10 pages)
Published Online: August 9, 2006
Article history
Received:
July 18, 2006
Revised:
August 9, 2006
Citation
Clark, J. P., and Grover, E. A. (August 9, 2006). "Assessing Convergence in Predictions of Periodic-Unsteady Flowfields." ASME. J. Turbomach. October 2007; 129(4): 740–749. https://doi.org/10.1115/1.2720504
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