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Shock Boundary Layer Interactions - A Multiphysics Approach

Bhide, Kalyani R
http://orcid.org/0000-0002-6954-0406
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543994392025663

Abstract Details

2018, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Shock waves are a major source of drag in supersonic flows as they affect the aero-thermodynamic performance and impose pressure and temperature loads on the structure under consideration. The aim of this work is to address such multiphysics phenomenon and mitigate the losses due to shock waves in a series of low to high aspect ratio rectangular supersonic nozzles with sharp and smooth throats. 3D steady RANS CFD is performed on a baseline converging-diverging nozzle (exit aspect ratio 2 and design Mach number 1.5) with sharp throat and the results are validated with the experimental data. Turbulence model study shows that k-omega SST compares better with the experimental data. A shock wave is present in the baseline nozzle due to the sharp throat. In order to eliminate the sharp throat, a general-purpose curve generator - Gencurve is developed and implemented using Python 3.5. Equivalent smooth nozzle geometries are created using this tool. These show improvements in various performance parameters such as discharge coefficients, thrust coefficients, etc., due to the mitigated shocks and reduced boundary layer thicknesses. The baseline and the equivalent smooth nozzle geometries are further analyzed at design (NPR 3.67) and off-design conditions using multi-physics simulations, which are, for the first time, performed on rectangular supersonic nozzles. This work highlights the significance of Fluid-Thermal-Structural-Interaction (FTSI) simulations as a diagnosis of existing designs (exit aspect ratio 2 with sharp throat) and as a means of preliminary investigation to ensure feasibility of new designs before conducting experimental and field tests. Structural deformation in the baseline design is far less than the boundary layer thickness as the impact of Shock Boundary Layer Interactions (SBLI) is not as severe. FTSI demonstrates that the discharge coefficient of the improved design is 0.99 and its structural integrity remains intact at off-design conditions. This proves the feasibility of the improved design. Although the influence of FTSI is shown for a nozzle, the approach is general and essential in any product design cycle or as a prelude to building prototypes. Investigating low (1, 2, 3) and high (8, 12) aspect ratio nozzles with sharp throats is also a focus of this work. Although the throat shocks are present in these configurations, they become weaker and the shock cell size reduces as the aspect ratio increases. Hence, the magnitude of wall shear stress at the nozzle throat decreases. The boundary layer thickness on nozzle exit plane along the minor axis decreases as the aspect ratio increases. This improves the discharge coefficient due to the less blockage offered by the boundary layer. All jets spread more in the minor axis than in the major axis and eventually become circular a few diameters downstream the nozzle exit. The velocity decay in high aspect ratio nozzles is faster than in the low aspect ratio nozzles. An issue of modeling quarter section of the flow domain using symmetry boundary conditions is also addressed.
Shaaban Abdallah, Ph.D. (Committee Chair)
Milind Jog, Ph.D. (Committee Member)
Kiran Siddappaji, Ph.D. (Committee Member)
91 p.
Aerospace Materials
Rectangular supersonic nozzles; Multiphysics; shock boundary layer interactions; aspect ratio; wall curve; boundary layer

Recommended Citations

Citations

  • Bhide, K. R. (2018). Shock Boundary Layer Interactions - A Multiphysics Approach [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543994392025663

    APA Style (7th edition)

  • Bhide, Kalyani. Shock Boundary Layer Interactions - A Multiphysics Approach. 2018. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543994392025663.

    MLA Style (8th edition)

  • Bhide, Kalyani. "Shock Boundary Layer Interactions - A Multiphysics Approach." Master's thesis, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543994392025663

    Chicago Manual of Style (17th edition)

ucin1543994392025663
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This open access ETD is published by University of Cincinnati and OhioLINK.