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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 18 - August 23, 2024. Students must commit to these dates. No exceptions will be made.
  • Accepted students must live in provided Caltech housing.

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Project:  Experiments on the Cylindrical Crow Instability
Disciplines:  Mechanical Engineering, Applied Physics
Mentor:  Joseph Shepherd, Professor, (EAS),
Mentor URL:  (opens in new window)
AO Contact:  Michael Wadas,
Background:  The Crow Instability (CI) induces the growth of symmetric perturbations along adjacent vortex cores and is responsible for the dissipation of wingtip vortices shed into the wakes of large aircraft [1] and possibly the stimulation of clumps in circumstellar environments like the remnant of Supernova 1987A [2]. The CI has received significant attention in recent years due to its relevance to expanding vortex dipoles, as famously visualized in the experiments of colliding vortex rings by Lim and Nickels [3]. Alignment issues make such experiments notoriously challenging to execute, and the geometry of the expanding dipole that affects the development of the CI is constrained by the properties of initial vortex rings. However, an expanding vortex dipole can also be created using an outward-pointing radial starting jet, circumventing the challenge of precisely aligned vortex ring generators and significantly expanding the achievable parameter space of the vortex dipole geometry. Furthermore, an inward-pointing radial starting jet would enable the unprecedented capability to examine the CI with reversible base flow.
Description:  We seek a student interested in designing an experimental platform to visualize the cylindrical CI, envisioning that initial rapid prototyping could largely be achieved with 3D printing and colored dye for visualization. We have already demonstrated proof of the outward-pointing radial jet concept, but refinement of the concept for controllability and repeatability is required before the platform can produce high-quality data suitable for publication, which, given sufficient contribution, the student is welcome to participate in. The final platform will be used to examine the dynamics of the CI and other vortex-core instabilities, including the transition to turbulence and relevance to circumstellar environments including Supernova 1987A and protoplanetary disks. The student will work closely with postdoctoral scholar Michael Wadas (
References:  [1] Crow, Stability theory for a pair of trailing vortices, AIAA J., 8 12 (1970).
[3] Lim & Nickels, Instability and reconnection in the head-on collision of two vortex rings, Nature, 357 225-227 (1992)
Student Requirements:  Some familiarity with CAD and 3D printing is desired, though not required.
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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