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Investigation of Flow over a Fin Located Downstream of a Supersonic Jet into Subsonic Crossflow

Hojaji Najafabadi, Mohammad | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42470 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Tayyebi Rahni, Mohammad; Soltani, Mohammad Reza
  7. Abstract:
  8. The problem of jet into a cross flow is one of the classic problems in fluid mechanics and has many engineering applications, such as in vector thrust control systems. Although many works have been done in this field, there have not been enough research in interactions of supersonic jets into compressible subsonic cross flows (specially its interaction with control surfaces downstream). Hence, the purpose of this research is to get better understanding of this interaction and its effects on control surfaces downstream (both numerical and experimental). Some of the individual achievements of this research are the design and manufacturing of supersonic jet system, parametric study of: boundary layer thickness, jet into freestream dynamic pressure ratio (J), and the location of fins. In the numerical section of this research, a home made computer code (finite volume) was prepared, which solves turbulent compressible flows, using AUSM scheme for flux calculations. Also, the Spalart-Almaras turbulence model was used. In the experimental part, a flat plate equipped with pressure holes and a special rake were prepared and used. The freestream and the exhausted jet Mach numbers were held constant (0.7 and 2.5, respectively). The results show that the counter rotating vortex pair (CRVP) gradually penetrates into the freestream and causes the jet plume divides into two parts. Also, it is observed that this penetration increases duo to increasing of J. The results related to the interactions between the jet, the freestream, and the fin downstream (the case where the fin is at the symmetry plane) show that, in the near field of the jet, the pressure coefficient of parts of the fin in contact with the CRVP decreases. While, in the case the fin is in the near field, depending on the distance relative to the symmetry plane with locating the fin on the way of one of the vortices, their path changes and their initial balance is missed. Furthermore, due to the rotation of the fluid, the fin observes flow with different angles of attack changing from positive to negative along the span. In the case where the fin is in the farfield, the flow field is not affectted by the presence of the fin. However, due to the influence of vortices, the fin feels the flow with the same sign of angle of attack
  9. Keywords:
  10. Supersonic Jet ; Numerical Investigation ; Experimental Investigation ; Jet into Cross Flow Interaction ; Winglets ; Subsonic Crossflow

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