Single stage to orbit propulsion devices are being developed as part of low cost access to space endeavors. Sea level operation of high area ratio rocket nozzle used in rocket engines leads to an overexpanded flow condition resulting in high side loads. Secondary injection of propellants in high area ratio nozzle is an attractive option to overcome the inefficiency of operation of such nozzles in sea level conditions in addition to the augmentation of thrust. A numerical study on thrust augmentation in high area ratio nozzle by secondary injection of propellants is presented here. The turbulent compressible reacting flow in rocket nozzle with auxiliary injection is simulated using conservation equations for chemical species based on finite rate chemistry model and compressible Navier-Stokes equations with AUSM+-up upwind scheme based unstuctured finite volume solver. An optimized eight step, six species reduced H2-O2finite chemistry reaction model is used to model the supersonic combustion. The indigenously developed solver has an efficient rescaling algorithm to alleviate the effect of stiffness in conventional explicit algorithm for simultaneous solution of reacting flow. The code is validated using the wall pressure and hydrogen concentration values reported for the similar high area ratio rocket nozzle. Accurate prediction of nozzle performance is possible with present turbulent reacting flow simulation as it take care of all losses in nozzle flow. Extensive computations have been performed for the performance estimation of high area ratio rocket nozzle for various prospective auxiliary injection options.
There is an increase in the middle income class in the tropical cities of the global south. Which has lead governments to focus on the provision of sustainable housing stocks. The design of these houses is a concern as they are often designed to maximize occupancy. Based on analysis of existing building design, the standard midrise buildings of Indonesia and Mumbai, India consists of double-loaded buildings to optimize the spaces. In such double-loaded buildings, the occupants living on the leeward side of the building may encounter poor crossventilation. This study aims to determine the optimum void design allowing sufficient cross-ventilation in naturally ventilated multi-story buildings. Computational Fluid Dynamics (CFD) is used to study the ventilation effect of voids with different sizes, windcatcher, and window size. CFD simulations are validated with the help of a Wind Tunnel Experiment (WTE). The results conclude that the provision of a void can increase natural ventilation in the leeward units of the building. The smallest void size showed the highest wind velocities. Provision of windcatcher and bigger-sized window further increased the natural ventilation on the leeward units of the building.
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