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Amgen Scholars: Announcements of Opportunity

Below are Announcements of Opportunity posted by Caltech faculty for the Amgen Scholars program.

Announcements of Opportunity are posted as they are received. Please check back regularly for new AO submissions! Remember: This is just one way that you can go about identifying a suitable project and/or mentor. For additional tips on identifying a mentor click here.

Please remember:

  • Students pursuing Amgen must be U.S. citizens, U.S. permanent residents, or students with DACA status.
  • Students pursuing Amgen must complete the 10-week program from June 21 - August 25, 2023. Students must commit to these dates. No exceptions will be made.
  • Accepted students must live in provided Caltech housing.

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Project:  Stability of shock-induced separated flow
Disciplines:  Aeronautics, Mechanical Engineering
Mentor:  Chih-Yung Wen, Chair Professor of Aeronautical Eng./Dept. Head, (EAS), cywen@polyu.edu.hk, Phone: 852-34002387
Mentor URL:  https://www.polyu.edu.hk/aae/people/academic-staff/ir-prof-wen-chih-yung/  (opens in new window)
Background:  NOTE: This project is being offered by a Caltech alum and is open only to Caltech students. The project will be conducted at Hong Kong Polytechnic University in Hong Kong.

The stability of shock-wave/laminar boundary-layer interactions over canonical configurations will be investigated using global stability analysis (GSA) and direct numerical simulations (DNS). The global stability boundary will be determined over a wide range of flow governing parameters and geometries, which can be correlated with a scaled deflection angle according to triple-deck theory. Beyond a critical angle, the nominally two-dimensional/axisymmetric base flow becomes globally unstable to three-dimensional perturbations. Linear amplification of the leading mode generates pairs of counterrotating streamwise vortices inside the separation region, which may persist downstream of reattachment depending on the shock interaction type. The GSA will be compared with the companion DNS with no upstream disturbances for hypersonic flow over a compression corner. The saturated flow generally exhibits broadband low-frequency unsteadiness. As the flow is further destabilized, the global instability can trigger laminar?turbulent transition in the reattached boundary layer. When the flow is globally stable, the response of the flow to upstream disturbances that are harmonic in time and in the spanwise direction will be further examined using global resolvent analysis (GRA) for hypersonic compression corner flow. The relationship between the preferential spanwise wavelength of the streaks and the deflection angle and the corresponding scaling with the incoming boundary-layer thickness will be investigated with DNS with the incoming flow perturbed by white noise.

Description:  Theoretical analyses using Linear Stability Analysis, GSA, and GRA; Numerical Simulations
References:  1. Cao, S.B., Hao, J.A., Klioutchnikov, I., Wen, C.Y., Olivier, H., Heufer, A., “Transition to Turbulence in Hypersonic Flow over a Compression Ramp due to Intrinsic Instability,” Journal of Fluid Mechanics, Vol. 941, A8, pp. 1-26, Apr. 25, 2022.
2. Hao, J.A., Fan, J.H., Cao, S. B., and Wen, C.Y., “Three-dimensionality of Hypersonic Laminar Flow over a Double Cone,” Journal of Fluid Mechanics, Vol. 935, A8, pp. 1-24, 2022.
3. Hao, J.A., Fan, J.H., Cao, S. B., and Wen, C.Y., “Three-dimensionality of Hypersonic Laminar Flow over a Double Cone,” Journal of Fluid Mechanics, Vol. 935, A8, pp. 1-24, 2022.
4. Cao, S.B., Hao, J.A., Kiloutchnikov, I., Olivier, H., Heufer, A., Wen, C.Y., “Leading-edge Bluntness Effects on Hypersonic Three-dimensional Flows over a Compression Ramp,” Journal of Fluid Mechanics, Vol. 923, A27, pp. 1-15, July, 2021.
5. Hao, J.A., Cao, S.B., Wen, C.Y.*, and Olivier, H., “Occurrence of Global Instability in Hypersonic Compression Corner Flow,” Journal of Fluid Mechanics, Vol. 919, A4, July, 2021.
Student Requirements:  Aerodynamics, CFD, mathematics
Programs:  This AO can be done under the following programs:

  Program    Available To
       SURF    Caltech students only 

Click on a program name for program info and application requirements.

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