Nonlinear Evolution of Unequal Line Vortex Pairs
Abstract
The trailing vortex structures generated by control or lifting surfaces are often created in pairs or may encounter other vortices engendered by their flow configuration. The coupled interactions of these line vortices can lead to vortex merger or cooperative instability that will define the state of the downstream flow and may impose significant unsteady fluid loads on nearby solid structures. Induced stretching of the weaker vortex in unequal vortex pairs drops its core pressure sharply and can cause cavitation inception, which can further complicate the overall vortex dynamics. An engineering model to estimate this inception location for vortex pairs is presently lacking, as is a complete understanding of the coupling of the large-scale dynamics of vortex pairs with the flow field within their cores during the stretching process. These knowledge gaps motivate the present theoretical and computational investigation into the long-time, nonlinear evolution of generalized line-vortex pairs, where the more realistic scenario of vortices emanating from either a fixed or moving location in space is favored over the classical approach assuming infinite vortices. This investigation will conduct large-eddy simulations of isolated and paired vortex configurations in conjunction with theoretical predictionsfor the nonlinear evolution of unequal vortex pairs using the Klein-Majda vortex framework; these efforts will be validated againstavailable experimental data that will connect the fluid mechanics of interest to the conditions for cavitation inception.The overarching basic research objective is a detailed understanding of how the asymmetries of co-rotating and counter-rotating vortex pairs (e.g., unequal vortex strengths, different core sizes, or vortex misalignment) affect the dynamical evolution of the pair until nonlinear saturation or destabilization occurs. A successful research program will initiate a parametric map of the likely mode of instability or breakdown for the vortex pair based on its initial state; inform a predictive model for the location of inception for realistic hydrodynamic configurations that is grounded in basic fluid mechanical principles; and connect the occurrence of extreme stretching events of secondary vortices to nonlinear vortex induction mechanisms, where appropriate. The anticipated practical advantage of these outcomes is the ability to use data that may be produced by low-cost (Reynolds-averaged) computational simulations of hydrodynamic flows as an initial condition or parameter set to inform reliable vortex stability or cavitation susceptibility predictions that would otherwise require immense computational resources.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2023
- Source ID
- N000142312700
Entities
People
- Justin W Jaworski
Organizations
- Lehigh University
- Office of Naval Research
- United States Navy