Compressibility effects on quasistationary vortex and transient hole patterns through vortex merger. (20th August 2019)

• Record Type: Journal Article
• Authors: Mukherjee, Rupak; Gupta, Akanksha; Ganesh, Rajaraman
• Is Part Of: Physica scripta. Volume 94:Number 11(2019)
• Publication Date: 2019-08-20
• Subjects: fluid dynamics -- weakly compressible flow -- vortex merger; Physics -- Periodicals; 530.05
• DOI: 10.1088/1402-4896/ab1a6a
• Languages: English
• ISSNs: 0031-8949

Abstract

Abstract: The effect of compressibility in the process of vortex merging is discussed. In past, in the incompressible limit, it has been observed that the merging of a collection of intense point-like vortices arranged uniformly outside a circular vortex, can lead to quasistationary vortex patch and transient hole pattern inside the patch via nonlinear merger process leading to 'vortex crystals'. Weak compressibility is seen to introduce a natural acoustic scale to the problem. We find that the natural mode is independent of the number of point-like vortices and the amplitude scales linearly with compressibility. Further, it is identified that after a merger, the system exhibits oscillation at a natural frequency together with its harmonics and beats with its own harmonics. The power of the frequency is found to scale as M −2, where M is the Mach number. Also the vortex crystals formed are found to 'melt' faster as compressibility is increased from M = 0 to 0.5.