Journal of Mechanical Science and Technology

The Korean Society of Mechanical Engineers (대한기계학회)
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Frequency Effects of Upstream Wake and Blade Interaction on the Unsteady Boundary Layer Flow

  • Kang, Dong-Jin (School of Mechanical Engineering, Yeungnam University) ;
  • Bae, Sang-Su (School of Mechanical Engineering, Yeungnam University)
  • Published : 2002.10.01
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Abstract

Effects of the reduced frequency of upstream wake on downstream unsteady boundary layer flow were simulated by using a Wavier-Stokes code. The Wavier-Stokes code is based on an unstructured finite volume method and uses a low Reynolds number turbulence model to close the momentum equations. The geometry used in this paper is the MIT flapping foil experimental set-up and the reduced frequency of the upstream wake is varied in the range of 0.91 to 10.86 to study its effect on the unsteady boundary layer flow. Numerical solutions show that they can be divided into two categories. One is so called the low frequency solution, and behaves quite similar to a Stokes layer. Its characteristics is found to be quite similar to those due to either a temporal or spatial wave. The low frequency solutions are observed clearly when the reduced frequency is smaller than 3.26. The other one is the high frequency solution. It is observed for the reduced frequency larger than 7.24. It shows a sudden shift of the phase angle of the unsteady velocity around the edge of the boundary layer. The shift of phase angle is about 180 degree, and leads to separation of the boundary layer flow from corresponding outer flow. The high frequency solution shows the characteristics of a temporal wave whose wave length is half of the upstream frequency. This characteristics of the high frequency solution is found to be caused by the strong interaction between unsteady vortices. This strong interaction also leads to destroy of the upstream wake strips inside the viscous sublayer as well as the buffer layer.

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References

  1. Choi, J. E., Sreedhar, M. K., Stern, F., 1996, 'Stokes Layers in Horizontal Wave Outer Flows,' ASME J. Fluids Engineering, Vol. 118, pp. 537-545 https://doi.org/10.1115/1.2817792
  2. Gissing, J. P., 1969, 'Vorticity and Kutta Con-dition for Unsteady Multi-Energy Flow,' ASME J. Applied Mechanics, Vol. 36, pp. 608-613 https://doi.org/10.1115/1.3564724
  3. Horlock, J., 1968, 'Fluctuating Lift Forces on an Airfoils Moving through Transverse and Chordwise Gusts,' ASME J. Basic Engineering, pp. 494-500
  4. Horwich, E. A., 1993, 'Unsteady Response of a Two Dimensional Hydrofoil Subject to High Reduced Frequency Gust Loading,' M. S. Thesis, Dept. of Ocean Eng., MIT, Cambridge, MA
  5. Kang, D. J., Bae, S. S., and Joo, S. W., 1998, 'An Unstructured FVM for the Numerical Prediction of Imcomressible Viscous Flows,' Transactions of the KSME, Vol. 22, No. 10, pp. 1410-1421
  6. Kang, D. J., Bae, S. S., 1999a, 'Navier-Stokes Simulation of MIT FFX by Using an Unstructured Finite Volume Method,' ASME Turbo -Expo IGTI-99-214
  7. Lee, Y. T., Kirtis, C, Rogers, S. E., Zawadzki, I. and Kwak, D., 1995, 'Steady and Unsteady Multi-Foil Interactions by Navier-Stokes and Euler Calculations,' Unsteady Aerodynamics and Aeroelasticity of Turbomachines, Elsevier Science, pp. 93-107
  8. Paterson, E.G. and Stern, F., 1999, 'Computation of Unsteady Viscous Marine Propulsor Blade Flows-Part 2: Parametric Study,' ASME J. Fluids Engineering, Vol. 121, pp. 121-147
  9. Poling, D. R. and Telionis, D. P., 1986, 'The response of Airfoils to Periodic Disturbances-The Unsteady Kutta Condition,' AIAA J. Vol. 24, No. 2, pp. 193-199 https://doi.org/10.2514/3.9244
  10. Rice, J. Q., 1991, 'Investigation of Flows around a Two-dimensional Hydrofoil in Steady and Unsteady Flows,' M. S. Thesis, Dept. of Ocean Eng., MIT, Cambridge, MA
  11. Tsahalis, D. Th. and Telionis, D. P., 1974, 'Response of Separation to Impulsive Changes of Outer Flow,' AIAA J. Vol 12, pp. 614-619 https://doi.org/10.2514/3.49307
  12. Thomadakis, M. and Leschziner, M., 1996, 'A Pressure Corection Method for the Solution of Incompressible Viscous Flows on Unstructured Grids,' Int. J. Nume. Methd. in Fluids, Vol. 22, pp. 581-601 https://doi.org/10.1002/(SICI)1097-0363(19960415)22:7<581::AID-FLD365>3.0.CO2-RPDF
  13. Stern, F., Hwang, W. S. and Jaw, S. Y., 1989, 'Effects of Waves on the Boundary Layer of Surface Piercing Flat Plate: Experiment and Theory,' J. Ship Research, Vol. 33, pp. 63-68