Sharif Digital Repository

The purpose of this paper is to design and develop an advanced co-flow fluidic nozzle, based on the Coanda effect concept, for multi-directional thrust vectoring of small jet engines. Recent progress on finding an optimal geometry with a fixed momentum ratio to achieve maximum thrust deflection angle is discussed here. The efficiency of the system is found to be a weakly nonlinear function of the secondary to primary flow momentum as well as three geometric parameters. A useful empirical formulation is derived for thrust vectoring angle, based on a series of tests carried out on different nozzles. An accurate computational fluid dynamics model is also developed and evaluated against the... 

The aim of this study is to investigate the uniform cooling of a hot isothermal heated target surface, using four turbulent impinging air jets. Eight parameters including the width of jets, the space between the inner jets, the space between inner and outer jets, the distance of jets from the plate, the impingement angle of jets, and the overall volumetric flow rate of the cooling air per unit depth of the nozzle are considered as design variables. The normalized standard deviation of the local Nusselt number from the desired Nusselt number is considered as the objective function. An optimization algorithm based on pattern search method is utilized to obtain the optimum array of the jets.... 

The present research paper attempted to utilize a computational investigation for optimizing the fluidic injection angle effects on thrust vectoring. Simulation of a convergent divergent nozzle with shock-vector control method was performed, using URANS approach with Spalart–Allmaras turbulence model. The variable fluidic injection angle is investigated at different aerodynamic and geometric conditions. The current investigation demonstrated that injection angle is an essential parameter in fluidic thrust vectoring. Computational results indicate that optimizing injection angle would improve the thrust vectoring performance. Moreover, dynamic response of starting thrust vectoring would... 

Supersonic gas separator is proposed for methane purification. One-dimensional analysis is performed to examine the design aspects associated with the converging-diverging nozzle and the liquid separation chamber. The results indicate that at low swirl intensities, the separation chamber length is about 100 times of the nozzle throat. Increasing the swirl intensity would lower this length sharply and it will be less than 10 for swirl intensity of unity which is equivalent to a swirl angle of 45°. In addition, a sensitivity analysis of the separator performance to the inlet conditions like the temperature, pressure, and composition of the mixture is carried out. It is observed that increasing... 

In this study, a numerical investigation is carried out to reveal the potential of obtaining uniform cooling on a planar surface by impinging jets in a turbulent flow regime using the SST k−ω turbulence model. Twin turbulent sweeping impinging jets (TTSIJ), as an idealization of an array of jets, are considered for heat transfer with the planar target surface. Unlike other studies that focused on a few effective parameters or limited the impinging jets to certain conditions, in this study, a more general investigation is performed to clarify the effects of all influential parameters on heat transfer. To this end, the effects of 8 design variables namely Reynolds number, the jet-to-target... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

This paper introduces a new methodology for designing and optimizing the performance of hydraulic Cross-Flow turbines for a wide range of operating conditions. The methodology is based on a one-step approach for the system-level design phase and a three-step, successive numerical analysis approach for the detail design phase. Compared to current design methodologies, not only does this approach break down the process into well-defined steps and simplify it, but it also has the advantage that once numerical simulations are conducted for a single turbine, most of the results can be used for an entire class of Cross-Flow turbines. In this paper, after a discussion of the research background, we... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,...