CFD Validation Of Incompressible Cross-Flow Discharge Coefficients

NAFEMS International Journal of CFD Case Studies

Volume 2, February 2000

ISSN 1462-236X

CFD Validation of Incompressible Cross-Flow Discharge Coefficients

Q. G. Rayer
Rolls-Royce Plc, P.O. Box 31, Derby, DE24 9DH

https://doi.org/10.59972/5xber0cm

Keywords: CFD, Validation, Incompressible, Cross-Flow Discharge Coefficients and Simulation

Abstract

Validation against air systems problems is required to enable Computational Fluid Dynamics (CFD) codes to be confidently used in the design of turbine cooling air systems. CFD calculations of orifice cross-flow discharge coefficients (C_d) have been compared with measurements by Rohde et al [1]. Simulations have been carried out for cases with a low main duct Mach number (M_d ~ 0.25) using incompressible flow modelling. Comparisons have been made of cross-flow discharge coefficients for a range of pressure-head ratios and Mach numbers. Results at a main duct Mach number of 0.07 were obtained using the standard k-ε.: turbulence model which gave agreement to better than 5% for absolute values of pressure-head ratios and discharge coefficients. The trends in the data for pressure-head ratios and Mach numbers were also reproduced. At a higher main duct Mach number of 0.25, the Mach number in the vicinity of the orifice reached 0.8. As expected this rendered incompressible flow modelling unsuitable, resulting in inaccurate determinations of orifice pressure-drops. Work is already in progress to simulate high Mach number cases using a more suitable compressible flow model. The results obtained so far give confidence that CFD will become a valuable tool for evaluating air system losses in novel configurations.

References

[1] Rohde, J E, Richards, H T and Metger, G W (1969), Discharge coefficients for thick plate orifices with approach flow perpendicular and inclined to the orifice axis, NASA Technical Note, NASA TN D-5467, 29 pages.

[2] Rayer, Q G and Snowsill, GD (1998), Validation of FLUENT against incompressible and compressible flow through orifices, IMechE, CFD in Fluid Machinery Design, ISBN 1-86058-165-X, ISSN 1357-9193, S546/010/98, pp. 79-91.

[3] Rayer, Q G and Snowsill, G D (1999), FLUENT validation for incompressible flow through a 0.5 aspect ratio orifice and compressible flow through a sharp-edged slit, NAFEMS Int J CFD Case Studies, Vol 2, in the press May 1999.

[4] Rayer, Q G ( 1999), Computational fluid dynamics guidelines for best working practice, submitted to NAFEMS Int J CFD Case Studies, April 1999.

[5] Hay, N and Lampard, D (1996), Discharge coefficient of turbine cooling holes: a review, Trans ASME, 96-GT-492.

[6] FLUENT (1996), User's guide for FLUENT/UNS and RAMPANT, release 4.0, April 1996, Fluent Incorporated, Centerra Resource Park, 10 Cavendish Court, Lebanon, NH 03766, USA.

[7] Versteeg, HK and Malalasekera, W (1995), An introduction to computational fluid dynamics, Longman Group Ltd., ISBN 0-582-21884-5, 257 pages.

Cite this paper

Q. G. Rayer, CFD Validation of Incompressible Cross-Flow Discharge Coefficients, NAFEMS International Journal of CFD Case Studies, Volume 2, 2000, Pages 19-48, https://doi.org/10.59972/5xber0cm