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Numerical Modeling of Unsteady Partial Cavitaion over Axisymmetric Bodies Using Boundary Element Method

Emami, Pedram | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41568 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Seif, Mohammad Saeed
  7. Abstract:
  8. In this thesis, the potential flow including unsteady partial cavitation around axisymmetric bodies are studied using a boundary element method (BEM) based on potential theory. For this purpose the wetted surface of the body and cavity surface are divided (approximated) to panels. Then, by applying the Green’s third identity and expressing this theory in potential flow around every surface, cavitation can be modeled by distributing the source and the dipole rings on cavity/body surface. In order to approaching this goal we introduced dipole rings distribution on the cavity and body surfaces and source rings distribution on the cavity surface. In this work the cavitation number is assumed to be changed with a periodic manner and is supposed to be known. By solving the equation system, source strengths on the cavity surface are acquired and after that by using the kinematic boundary condition over the cavity shape guess, the new cavity shape is acquired and this procedure is done until the algorithm convergence is obtained. The comparison between the numerical results of this method around axisymmetric bodies with experiment and analytical results shows the good capability of this method in simulating the unsteady partial cavitation.In addition of above investigation, numerical modeling of steady partial cavitation over axisymmetric bodies is done, using boundary element method in a similar manner. Although in the potential theory many simplifier hypothesis are used, but the results show that this method can achieve most important cavitation parameters as like as cavity length, cavity shape and pressure coefficient very accurate, specially the advantage of this method respect to the other numerical methods based on the navier-stokes equation is simulating the steady partial cavitation in a very short time about few minutes while for the second one, this time is about few days. So this is the main boundary element method’s advantage.
  9. Keywords:
  10. Boundary Element Method ; Panel Method ; Potential Theory ; Partial Cavitation ; Unsteady Partial Cavitation

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