Aero-Thermodynamics Optimization of Re-Entry Capsule in the Slip Flow Regime

We carry out numerical simulations to optimize the re- entry capsule configurations based on aero-thermodynamic properties such as drag, pressure and heat load. The open source software OpenFOAM is used with the compress- ible computational fluid dynamics (CFD) solver rhoCen- tralFoam. CFD solver is implemented with the first-order Maxwell’s velocity slip and the Smoluchowski temperature jump boundary conditions. We report results for different altitudes and Mach numbers with varying second cone an- gle and bluntness of the re-entry capsule. It is noted that the heat loads are greatly reduced by changing the capsule con- figuration from single to bi-cone. With increasing second cone angle heat loads are enhanced, but the average drag and pressure coefficients found to be least sensitive. How- ever, with increase in bluntness the average value of heat load decrease slightly and the peak value significantly, while drag values exhibit contrasting behaviour

Computational Analysis of Side Jet Interaction With a Super-sonic Cross-flow

We have numerically investigated the interaction of a side jet positioned on the small rocket, with the supersonic cross-flow. An open source CFD tool, OpenFOAM is used to model the complex flow of a jet-atmosphere interaction. The flow fields are computed by the steady 3-dimensional Navier-Stokes solver with k- ! SST turbulence model. Our solver is validated with the experimental pressure data available on the rocket wall and a systematic study is done by varying parameters like jet pressure ratio. Aerothermodynamic coefficients for various flow conditions are reported, and pitching moments and normal forces are found to vary linearly with the jet pressure ratios. Possible contamination of the on-board sensor located on the rocket wall due to impinging plumes is also examined. This study helps in designing effective missile control by selection of the location of jet and pressure ratios

Numerical Analysis of Rarefied Hypersonic and Chemically Reacting Flow-field

We have developed an open source CFD tool, which can simulate high temperature and chemically reacting flow-field in the rarefied regime. It is used to carry out simulations in the intermediate hypersonic flow regime (Mach number range from 8 to 15). Solver is tested with available data for high speed and rarefied flow applications. Heat load values for blunt conical surface and shock standoff distance for sphere are obtained with our solver and good agreement has been exhibited with the experimental data

Aero -thermodyanamic Analysis of Re-entry Capsule in Slip Flow Regime

We carry out numerical simulations to predict the aero-thermodynamic characteristics of a bi-conical re-entry capsule in the slip flow regime. The open source software OpenFOAM(Open Field Operation and Manipulation) is used with the compressible computational fluid dynamics (CFD) solver rhoCentralFoam. CFD solver is implemented with both the conventional no-slip boundary conditions, and also the first-order Maxwell’s velocity slip and the Smoluchowski temperature jump boundary conditions. CFD solver has been vali-dated with the experimental data for the pressure coefficient and density variations on the capsule surface and also validated with surface pressure and temperature and velocity for a flow over flat plate and wedge surface for altitude above 60km and Mach number above 10

EFFECT OF CHEMICAL NON-EQUILIBRIUM ON FLOW PARAMETERS IN THE INTERMEDIATE HYPERSONIC REGIME

The new solver hypersonicIithFoam has been developed in the OpenFOAM framework. OpenFOAM has rhoCentralFoam which is a density based N-S solver, is used as a base solver. Additional features are incorporated to model reacting flows, variable multi-species diffusion and thermodynamic proper- ties of high-temperature air. The solver is implemented to model the transport properties based on a kinetic theory for its widespread applicability. Viscosity and Thermal conductivity are obtained using the model based on Lennard-Jones potential, and Chapman-Enskog diffusivity model is used to compute binary dif- fusion coefficient. Multicomponent mixture properties are calcu- lated based on a mole fraction. All species are assumed to be in thermodynamic equilibrium, so the state of the gas is governed by single equilibrium temperature. The solver is tested with the available experimental data for Heat flux and coefficient of pres- sure Cp distribution over a surface of ELECTRE article. The hy- personic solver is shown significant improvement over a conven- tional compressible solver. Simulations are carried out for the flow over a sphere at different altitudes using both the conven- tional and the hypersonic solver for qualitative and quantitative comparisons. Post shock temperature and peak heat flux values are remarkably reduces due to the implementation of real gas ef- fects and air chemistry. Rarefaction effects become significant from 70 km

Modeling of Knudsen Layer Effects in the Micro-Scale Backward-Facing Step in the Slip Flow Regime

The effect of the Knudsen layer in the thermal micro-scale gas flows has been investigated. The effective mean free path model has been implemented in the open source computational fluid dynamics (CFD) code, to extend its applicability up to slip and early transition flow regime. The conventional Navier-Stokes constitutive relations and the first-order non-equilibrium boundary conditions are modified based on the effective mean free path, which depends on the distance from the solid surface. The predictive capability of the standard ‘Maxwell velocity slip—Smoluchwoski temperature jump’ and hybrid boundary conditions ‘Langmuir Maxwell velocity slip—Langmuir Smoluchwoski temperature jump’ in conjunction with the Knudsen layer formulation has been evaluated in the present work. Simulations are carried out over a nano-/micro-scale backward facing step geometry in which flow experiences adverse pressure gradient, separation and re-attachment. Results are validated against the direct simulation Monte Carlo (DSMC) data, and have shown significant improvement over the existing CFD solvers. Non-equilibrium effects on the velocity and temperature of gas on the surface of the backward facing step channel are studied by varying the flow Knudsen number, inlet flow temperature, and wall temperature. Results show that the modified solver with hybrid Langmuir based boundary conditions gives the best predictions when the Knudsen layer is incorporated, and the standard Maxwell-Smoluchowski can accurately capture momentum and the thermal Knudsen layer when the temperature of the wall is higher than the fluid flow

Design and Development of Mechanical Solar Tracking System

In recent years, the growing global interest in the conservation of environment has provided a fresh motivation for research in the area of solar energy utilization. Already, installation of solar energy extraction devices such as solar panels, solar water heaters, solar cookers etc. is becoming popular in urban buildings. Most of these devices consist of a solar receptor that is kept facing the sun during the day, but the sun moves from east to west and the efficiency of the panel decreases. If one could trap this extra energy source then the efficiency of the solar panel would be increased. A tracking mechanism following the sun would achieve this aim. An attempt has been made to develop a simple yet efficient sun tracking mechanism using a motor, a speed reduction mechanism and real timer. The mechanism has been designed such that the sunrays falling on the panel are always perpendicular to the panel resulting in increase in efficiency of the electricity generation. This report presents, in detail, the design and construction adopted to develop the functional model that was fabricated and tested for performance which yielded the efficiency increase of 28.41% as compared to the conventional stationary panel position

Numerical investigation of a chemically reacting and rarefied hypersonic flow field

Numerical simulations are carried out in the non-continuum flow regime to analyze flow features in the shock layer of a reentry vehicle. A new solver, rarefiedHypersonicFoam, has been developed based on the OpenFOAM platform, which can simulate the intermediate hypersonic reacting flow regime, where chemical non-equilibrium effects are imperative. The solver accommodates features to model air chemistry, multispecies transport, thermodynamic properties of high-temperature air, and non-equilibrium boundary conditions. The solver is validated with ballistic range experimental data for shock standoff distance and heat flux values over a conical reentry vehicle. Results have exhibited good agreement with the experimental data and show significant improvement when compared with the conventional high-speed compressible flow solver. The modified solver is used to analyze hypersonic flow over a bi-conic reentry capsule at different altitudes and velocities in the rarefied hypersonic flow regime. The results show that at lower altitude, chemical reactions absorb a considerable amount of heat compared to higher altitude. The rate of reaction reduces with the decrease in the flow velocity, which results in reduced heat flux values. It is observed that, if only rarefaction effects are considered in the solver, it overpredicts the heat flux values. Therefore, incorporation of chemical reactions while analyzing rarefied hypersonic flow fields is imperative