Helicity and its Geometric Evolution in Viscous Vortex Loops
Abstract
The helicity of a laminar vortex ring is prescribed by its geometry in the forms of writhe and twist. In viscous fluids, helicity is not conserved, but nonetheless its evolution is naturally characterized by the geometry and topology of the vorticity field. By generating helical vortices using hydrofoils, we are able to measure their helicity and its evolution over a range of Reynolds numbers. Fully resolved DNS simulations with adaptive mesh refinement provide complementary insight. We present an analytic model for helicity evolution in vortex tubes with a natural geometric interpretation and compare its predictions to experiments and simulations.
This work was funded by U.S. NSF Grant DMR-1351506 and Army Research Office Grant W911NF-18-1-0046. Additional support was provided by the Chicago MRSEC (U.S. NSF Grant DMR 1420709), which is also gratefully acknowledged for access to its shared experimental facilities. Drs. Scalo and Zhao acknowledge the support of the Army Research Oce's Young Investigator Program (ARO-YIP) Award W911NF-18-1-0045. Scalo also acknowledges the support of the U.S. Air Force Research Laboratory (AFRL) DoD Supercomputing Resource Center (DSRC), via allocation under the subproject ARONC00723015.- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- 2020
- Bibcode:
- 2020APS..DFDP18007M