IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Numerical simulations of laser energy deposition in air are conducted. Local thermodynamic equilibrium conditions are assumed to apply. Variation of the thermodynamic and transport properties with temperature and pressure are accounted for. The flow field is classified into three phases: shock formation; shock propagation; and subsequent collapse of the plasma core. Each phase is studied in detail. Vorticity generation in the flow is described for short and long times. At short times, vorticity is found to be generated by baroclinic means. At longer times, a reverse flow is found to be generated along the plasma axis resulting in the rolling up of the flow field near the plasma core and enhancement of the vorticity field. Scaling analysis is performed for different amounts of laser energy deposited and different Reynolds numbers of the flow. Simulations are conducted using three different models for air based on different levels of physical complexity. The impact of these models on the evolution of the flow field is discussed. © 2008 Cambridge University Press.

Department of Aerospace Engineering

World University root node

Journal of Fluid Mechanics

Numerical simulation of the fluid dynamic effects of laser energy deposition in air

The thermal effects of laser-induced plasma on isotropic turbulence are studied using direct numerical simulation. Laminar and turbulent simulations are conducted. For the laminar simulations, a tear-drop shaped blast wave propagates into the background becoming spherical in time. Shock radius and jumps in fluid properties at the shock front are compared to experiment. Both short and long time behavior of the plasma is studied. At short times, baroclinic vorticity is generated as a consequence of propagation of the curved shock through the domain. At long times, the flow field forms toroidal vortex rings, as observed in experiments. For the turbulent simulations, turbulence levels get enhanced in regions of compression across the blast wave and suppressed in regions of expansion in the plasma core.

Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting

Direct numerical simulation of the thermal effects in plasma/turbulence interaction

Numerical issues associated with simulating strong blast waves in high temperature flows in a turbulent background have been addressed effectively. Spherical energy deposition in both laminar and turbulent flows is considered. A predictor-corrector based shock capturing scheme is implemented along with a base spectral discretization scheme to simulate strong blast waves generated in the flow. The shock capturing scheme is extended for high temperature flows in equilibrium. Formulation of high temperature eigen vector matrices for 3-D Euler equations is presented for a generalized coordinate system. A logarithm formulation of the continuity equation is used to address stability issues related to very low densities in the core. A non-linear limiter has been implemented to eliminate excessive dissipation of the background turbulence due to shock capturing.

Department of Electrical Engineering

Proceedings of the 16th Australasian Fluid Mechanics Conference, 16AFMC

Numerical simulation of strong blast waves in high temperature turbulent flows

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.