• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.9-17
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• 2008

When the stagnation temperature of the combustion chamber or ambient air increases, the specific heats and their ratio do not remain constant any more, and start to vary with this temperature. The gas remains perfect, except, it will be calorically imperfect and thermally perfect. A new generalized form of the Prandtl Meyer function is developed, by adding the effect of variation of this temperature, lower than the threshold of dissociation. The new relation is presented in the form of integral of a complex analytical function, having an infinite derivative at the critical temperature. A robust numerical integration quadrature is presented in this context. The classical form of the Prandtl Meyer function of a perfect gas becomes a particular case of the developed form. The comparison is made with the perfect gas model for aim to present a limit of its application. The application is for air.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.82-90
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• 2017

The aim of this work is to develop a new computational program to determine the effect of using the gas of propulsion of combustion chamber at high temperature on the shape of the two-dimensional Minimum Length Nozzle giving a uniform and parallel flow at the exit section using the method of characteristics. The selected gases are $H_2$, $O_2$, $N_2$, CO, $CO_2$, $H_2O$, $NH_3$, $CH_4$ and air. All design parameters depend on the stagnation temperature, the exit Mach number and the used gas. The specific heat at constant pressure varies with the temperature and the selected gas. The gas is still considered as perfect. It is calorically imperfect and thermally perfect below the threshold of dissociation of molecules. A error calculation between the parameters of different gases with air is done in this case for purposes of comparison. Endless forms of nozzles may be found based on the choise of $T_0$, $M_E$ and the selected gas. For nozzles delivering same exit Mach number with the same stagnation temperature, we can choose the right gas for aerospace manufacturing rockets, missiles and supersonic aircraft and for supersonic blowers as needed in settings conception.

• Solar Energy
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• v.2 no.1
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• pp.9-16
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• 1982

The problem of transient laminar natural convection in compressible fluid in a rectangular enclosure is considered. The upper and lower boundaries of the enclosure are thermally insulating and the side boundaries are maintained at fixed temperatures. The fluid is considered to be a perfect gas with constant viscosity and thermal conductivity and the formulation differs from the boussinesq simplification in that the effects of variable density are completely retained. The motions are restricted to two dimensions. For incompressible fluid, the natural convection is driven mainly by buoyancy force. But the solutions show that for compressible fluid, the natural convection is driven by pressure and buoyancy forces and the thermally induced motion is acoustic in nature.

• Journal of the Korean institute of surface engineering
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• v.52 no.6
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• pp.357-363
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• 2019

We investigated a synthesis yield and diameter distribution of single-walled carbon nanotubes (SWNTs) with respect to the growth position in a horizontal chemical vapor deposition (CVD) chamber. Thin films and line-patterned Fe films (0.1 nm thickness) were prepared onto ST-cut quartz substrates as catalyst to compare the growth behavior. The line-patterned samples showed higher growth density and parallel alignment than those of the thin film catalyst samples. In addition, line density of the aligned SWNTs at central region of the chamber was 7.7 tubes/㎛ and increased to 13.9 tubes/㎛ at rear region of the CVD chamber. We expect that the enhanced amount of thermally decomposed feedstock gas may contribute to the growth yield enhancement at the rear region. In addition, the lamina flow in the chamber also contribute to the perfect alignment of the SWNTs based on the value of gas velocity, Reynold number, and Knudsen coefficient we employed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.187-194
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• 2020

In this study, computational analyses are carried out to investigate the interference flows and the aerodynamic characteristics of a hit-to-kill intercepter due to lateral jets at medium altitude. In addition, the analyses are performed for air and multi-species gas used in the side jet. The results indicate that the position of the barrel shock are shifted upstream and the structure of the shock wave are changed for the multi-species jet when compared to the air jet. As a result, the high pressure region with multi-species jet moves forward and the pitching moment is higher under the same flow condition. Moreover, the inclusion of high temperature effects makes drastic changes in pressure distribution. The jet width is much bigger, and the jet diffuses over wider range in medium altitude than in low altitude, because of the low density of the freestream.