Badal Modi

Bio: Badal Modi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Boundary layer & Large eddy simulation. The author has an hindex of 1, co-authored 3 publications receiving 3 citations.

DNS of the thermal effects of laser energy deposition in isotropic turbulence

Abstract: The interaction of a laser-induced plasma with isotropic turbulence is studied using numerical simulations. The simulations use air as the working fluid and assume local thermodynamic equilibrium. The numerical method is fully spectral and uses a shock-capturing scheme in a corrector step. A model problem involving the effect of energy deposition on an isolated vortex is studied as a first step towards plasma/turbulence interaction. Turbulent Reynolds number Reλ = 30 and fluctuation Mach numbers Mt = 0.001 and 0.3 are considered. A tear-drop-shaped shock wave is observed to propagate into the background, and progressively become spherical in time. The turbulence experiences strong compression due to the shock wave and strong expansion in the core. This behaviour is spatially inhomogeneous and non-stationary in time. Statistics are computed as functions of radial distance from the plasma axis and angular distance across the surface of the shock wave. For Mt = 0.001, the shock wave propagates on a much faster time scale compared to the turbulence evolution. At Mt of 0.3, the time scale of the shock wave is comparable to that of the background. For both cases the mean flow is classified into shock formation, shock propagation and subsequent collapse of the plasma core, and the effect of turbulence on each of these phases is studied in detail. The effect of mean vorticity production on the turbulent vorticity field is also discussed. Turbulent kinetic energy budgets are presented to explain the mechanism underlying the transfer of energy between the mean flow and background turbulence.

Direct Numerical Simulation of the Thermal Effects of Plasmas on Turbulent Flows.

Abstract: The thermal effects of plasmas on isotropic turbulence are studied using direct numerical simulations. The temperature ratio of the plasma region to the background region is moderate. Two idealizations of the plasma are considered – spherical and conical. The conical idealization is found preferable in that it approximates the tear–drop shape of the plasma region that is observed experimentally, and produces baroclinic vorticity. The variation of the magnitude of the vorticity with temperature ratio and size of plasma region is examined. A blast wave followed by a region of expansion propagates normal to the axis of the plasma region. The turbulence is observed to be suppressed in the core of the plasma, presumably due to bulk expansion.