On the interaction between turbulence and a planar rarefaction
The modeling of turbulence, whether it be numerical or analytical, is a difficult challenge. Turbulence is amenable to analysis with linear theory if it is subject to rapid distortions, i.e., motions occurring on a timescale that is short compared to the timescale for nonlinear interactions. Such an approach (referred to as rapid distortion theory) could prove useful for understanding aspects of astrophysical turbulence, which is often subject to rapid distortions, such as supernova explosions or the freefall associated with gravitational instability. As a proof of principle, a particularly simple problem is considered here: the evolution of vorticity due to a planar rarefaction in an ideal gas. Analytical solutions are obtained for incompressive modes having a wave vector perpendicular to the distortion; as in the case of gradientdriven instabilities, these are the modes that couple most strongly to the mean flow. Vorticity can either grow or decay in the wake of a rarefaction front, and there are two competing effects that determine which outcome occurs: entropy fluctuations couple to the mean pressure gradient to produce vorticity via baroclinic effects, whereas vorticity is damped due to the conservation of angular momentum as the fluid expands. Whether vorticity grows or decays depends uponmore »
 Authors:

^{[1]}
 Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)
 Publication Date:
 OSTI Identifier:
 22357273
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALGORITHMS; ANALYTICAL SOLUTION; ANGULAR MOMENTUM; ASTROPHYSICS; CAPTURE; COMPUTERIZED SIMULATION; ENTROPY; EQUATIONS; EVOLUTION; FLUCTUATIONS; FLUIDS; GALAXY CLUSTERS; GRAVITATIONAL INSTABILITY; MACH NUMBER; PRESSURE GRADIENTS; REYNOLDS NUMBER; SPECTRA; THREEDIMENSIONAL CALCULATIONS; TURBULENCE