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Experimental and Analytical Investigation of Cavitation Phenomenon around Cylinder and Hydrofoil and its Effect on Drag Force

Jafari Gavzan, Iraj | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 40730 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Rad, Manouchehr
  7. Abstract:
  8. Cavitation phenomenon is defined as the process of rupturing of liquid by a decrease in pressure at nearly constant temperature and it is a very complex non- linear phenomenon. Therefore the theoretical and numerical analysis of cavitation is very difficult and even impossible. A high speed cavitation tunnel is designed and manufactured for experimental understanding of cavitation. The effects of cavitation on drag force of several models such as circular cylinder, hydrofoil and wedge with after body were studied. There was a sufficient turbulence provided at upstream flow, during the tests of circular cylinder and hydrofoil within Reynolds number 105 to .Boundary layer on the cylinder is turbulent and cavitation inception occurs at about 105o from stagnation, on the surface of mentioned model. After inception, the drag force decreased significantly, when the leading edge of attached cavity establishes at 90 o, the drag force will become maximum value and then this force decreases gradually during the lowering of cavitation number. Several regimes occur from inception to chocking. The cavitation effect on the back pressure at the mentioned Reynolds number and in a wide range of cavitation numbers are also examined. The inception cavitation number with respect to attack angle of hydrofoil is specified and drag forces are measured. The location of cavitation inception of wedges 15o, 30 o and 60 o with variable length after body is found. The nose of these bodies also was roughened by sand paper or chip and tests are performed. During the cavitation inception, drag force increases and then decreases slowly. For all tested models in high speed cavitation tunnel, the near-chocking conditions are approached and the corresponding cavitation numbers are calculated.

  9. Keywords:
  10. Drag Force ; Cavitation ; High Speed WaterTunnel ; Free Turbulence ; Smooth Surface ; Roughened Surface

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