Vortex instabilities and turbulence production in a density-stratified fluid 21-000000033
Abstract
A pair of parallel counter-rotating vortices is one of the most elementary flow configurations in the far wake of both aircraft andunderwater vehicles. Based on the Helmholtz s second theorem, an isolated vortex filament cannot end in a fluid so a high-Reynolds-number vortex line can survive a long distance if there is no instability is present. However, if two counter-rotating vortex lines are close to each other. The mutually-induced flows can trigger a range of complex three-dimensional instabilities, from short-wave-length elliptic instability to low-wave-length Crow instability. These two types of instabilities can significantly accelerate the wake decay through turbulence production. Therefore, any predictive simulations that are designed to capture the wake life time must accurately model the vortex instabilities and turbulence production, particularly in a density-stratified environment. In the proposed framework, a new experimental setup that provides a clean and well-controlled way of generating a pair of counter-rotating vortices in a density-stratified environment is proposed. Along with the setup, three diagnostic methods will be used to simultaneously extract the 3D geometry of vortex cores (bending and distortion) and the induced flows (plane strain and induced turbulence) nearby. The results will be input into the spectrum flux analysis method to understand the dynamic pathways from a coherent pair of vortices to chaotic turbulence in a density-stratified environment. The proposed framework will unveil the underlying physics of vortex decayand generate well-characterized experimental dataset to validate naval hydrodynamic simulations for underwater vehicles. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 06, 2021
- Source ID
- N000142112123
Entities
People
- Rui Ni
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy