Rakhab Mehta

By R. C. Mehta

Part of the book: Computational Simulations and Applications

By R. C. Mehta

Part of the book: Computational and Numerical Simulations

By Rakhab Chandra Mehta

The present chapter deals with heat transfer analysis around unspiked and spiked bodies at high speeds. A spike attached to a blunt-nosed body drastically alters its flowfield and influences the aerodynamic heating in a high speed flow. The effect of spike length, shape and spike-nose configuration is numerically studied at zero angle of incidence. The numerical analysis describes overall flowfield features over without and with forward facing spike attached to a blunt body at high speed flow. The shock stand-off distance, sonic line, stagnation point velocity gradient and stagnation point heat flux are analyzed and compared with different aerodisk configurations. It is found that the hemispherical aerodisk experiences high wall heat flux as compared to the flat-faced aerodisk. Numerical and experimental studies reveal that the wall heat flux levels are decreased in the presence of the spikes and aerospike as compared to without attached spiked to the blunt-nose basic configuration.

Part of the book: Heat Transfer

By Rakhab C. Mehta

The numerical simulations over several reentry vehicles are carried out by solving time-dependent compressible laminar axisymmetric Navier-Stokes equations for Mach 1.2–6.0. The fluid dynamics equations are discretized in spatial coordinates using integral formulation in conjunction with a finite volume method which reduce to semi-discretized ordinary differential equations. A local time-step is used to achieve steady-state solution. The numerical computation is carried out on a single-block structured computational grid. The flowfield features over the reentry vehicle such as formation of a bow shock wave ahead of the fore-body, expansion fan on the shoulder, and recirculation zone in the base region are well captured in the numerical simulations. Lower pressure acting on the base of the reentry capsule acts as base drag. The base drag coefficient based on maximum cross-section of the reentry capsule must satisfy inequality. The base drag coefficient is a function of several geometrical parameters of the fore-body and back-shell of reentry capsule, boundary layer, formation of free-shear layer in the wake region and freestream Mach number. The purpose of this chapter is to numerically evaluate and tabulate the base pressure and the base drag coefficients of various reentry space capsules at zero angle of incidence.

Part of the book: Hypersonic Vehicles

By Rakhab C. Mehta

A one-dimensional transient heat conduction equation is solved using analytical and numerical methods. An iterative technique is employed which estimates unknown boundary conditions from the measured temperature time history. The focus of the present chapter is to investigate effects of input parameters such as time delay, thermocouple cavity, error in the location of thermocouple position and time- and temperature-dependent thermophysical properties. Inverse heat conduction problem IHCP is solved with and without material conduction. A two-time level implicit finite difference numerical method is used to solve nonlinear heat conduction problem. Effects of uniform, nonuniform and deforming computational grids on the estimated convective heat transfer are investigated in a nozzle of solid rocket motor. A unified heat transfer analysis is presented to obtain wall heat flux and convective heat transfer coefficient in a rocket nozzle. A two-node exact solution technique is applied to estimate aerodynamic heating in a free flight of a sounding rocket. The stability of the solution of the inverse heat conduction problem is sensitive to the spatial and temporal discretization.

Part of the book: Inverse Heat Conduction and Heat Exchangers

By Rakhab Mehta

The computational fluid dynamics analysis is carried out to analyze the shock and flow characteristics of under- and over expanded supersonic free jets emanating from convergent-divergent nozzles. Influence of exit Mach number on shock cell lengths are analyzed with the help of density contours and schlieren images. A parameter based on an exit Mach number is obtained to characterize the pressure variation along the jet axis which shows them independent of the exit to ambient pressure ratio. Impingement flow fields over axisymmetric and wedge deflector are investigated employing numerically and compared with experimental results. Effects of jet expansion ratio and distance between the nozzle to deflector apex has been studied at various expansion ratios and distances. Impingement load is computed at various conditions. Pressure distributions over a surface of wedge and axisymmetric jet deflector are computed and compared between them. Pressure load on a diaphragm of a solid motor during lift-off of a satellite launch vehicle having four liquid engines is numerically simulated.

Part of the book: Simulation Modeling - Recent Advances, New Perspectives, and Applications [Working title]