This paper presents a fundamental gaskinetic study on high speed rarefied jets expanding into vacuum from a cluster of planar exits.Based on the corresponding exact expressions for one planar jet,this paper straightfo...This paper presents a fundamental gaskinetic study on high speed rarefied jets expanding into vacuum from a cluster of planar exits.Based on the corresponding exact expressions for one planar jet,this paper straightforwardly derives the combined multiple jet flowfield solutions of density and velocity components,however,for the combined temperature and pressure solutions,extra attention shall be practiced.Several direct simulation Monte Carlo simulation results are provided and they validate these analytical solutions of rarefied planar jet flows.展开更多
The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, redu...The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, reduced wetted area and parasite drag and good stability and control, which have been supported by independent analyses, design studies and wind tunnel tests. With such foreseen advantages, the present work is carried out to design joined-wing business-jet aircraft and study and investigate its advantages and benefits as compared to the current available conventional business jet of similar size, passenger and payload capacity. In particular, the work searches for a conceptual design of joined-wing configured business-jet aircraft that possesses more superior characteristics and better aerodynamic performance in terms of increased lift and reduced drag, and lighter than the conventional business jet of similar size. Another significant objective of this work is to prove that the added rigidity possessed by the joined wing configuration can contribute to weight reduction.展开更多
This paper presents a detailed analysis of the complex flow beneath two impinging jets aligned with a low-velocity crossflow which is relevant for the future F-35 VSTOL configuration, and provides a quantitative pictu...This paper presents a detailed analysis of the complex flow beneath two impinging jets aligned with a low-velocity crossflow which is relevant for the future F-35 VSTOL configuration, and provides a quantitative picture of the main features of interest for impingement type of flows. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 10^4, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = V/Uo of 22.5. The rear jet is located at S = 6 D downstream of the first jet. The results show a large penetration of the first （upstream）jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The rear jet （located downstream） it is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.展开更多
The present paper reports a numerical study of a spray impinging on a surface through a crossflow. This work is intended to study the influence of the spread/splash transition criteria in the modeling of the spray imp...The present paper reports a numerical study of a spray impinging on a surface through a crossflow. This work is intended to study the influence of the spread/splash transition criteria in the modeling of the spray impingement phenomenon. Several experimental correlations available in the literature are inserted in the same base model and the results are tested against experimental data. It can be concluded that the employment of an accurate transition criteria can improve the quality of the results.展开更多
The Japanese aircraft industry changed its course in approximately 2007. Mitsubishi Heavy Industry （MHI） Co. launched a project in which regional jets （Mitsubishi Regional Jet （MILl）） reentered the airliner manu...The Japanese aircraft industry changed its course in approximately 2007. Mitsubishi Heavy Industry （MHI） Co. launched a project in which regional jets （Mitsubishi Regional Jet （MILl）） reentered the airliner manufacturing market. Honda announced plans to develop, manufacture, and sell small passenger jets, or Honda Jets, in the United States （US） market. This paper summarizes the historical development of the industry using aircraft production statistics and analyzes the patent portfolio strategy from 1995 to 2006, a period in which MHI and Honda accumulated patents for the upcoming market entry. The author uses the following two measurements to evaluate niche widths among aircraft manufacturing companies： the Morishita＇s index and the principal component analysis. The former index is used in population ecology to measure overlapping species. The latter measurement is presented to clarify the validity of the Morishita＇s index. The author identifies MHI as a market leader, Kawasaki Heavy Industry （KHI） Co. as a challenger, Fuji Heavy Industry （FHI） Co. as a follower, and Honda as a nicher in the aircraft patent portfolio strategy in Japan.展开更多
In this paper results of previous researches of two-mode full engine model for Mach number range from 3 to 6 are presented. The main aims of researches are to obtain characteristics of full engine model and its compon...In this paper results of previous researches of two-mode full engine model for Mach number range from 3 to 6 are presented. The main aims of researches are to obtain characteristics of full engine model and its components (the inlet, the combustion chamber and the nozzle) in ramjet and scramjet regimes and to compare these characteristics with the calculation results according to CFD and to approximate (engineering) methods. Tests were carried out without ha supply (cold tests) and with fuel supply (study of ignition and combustion).Hydrocarbon and hydrogen fuel (gaseous or liquid) were used during the tests.展开更多
Pronounced aeroacoustic resonances are exhibited in the flow field where a jet emerges from an orifice or a nozzle and impinges on a solid surface. One instance where such resonances are produced is in a high speed je...Pronounced aeroacoustic resonances are exhibited in the flow field where a jet emerges from an orifice or a nozzle and impinges on a solid surface. One instance where such resonances are produced is in a high speed jet impingement, such as in the space launch vehicle systems, jet-engine exhaust impingement, and in the short take-off and vertical landing （STOVE） aircraft, etc. A highly unsteady flowfield leading to a drastic increase of noise level with very high dynamic pressure and thermal loads are noticed on nearby surfaces results dramatic lift loss, severe ground erosion and hot gas ingestion to the inlet in the jet engines. This highly unsteady behavior of the im- pinging jets is due to a feedback loop between the fluid and acoustic fields. In actual jet flow, the working gas may contain condensable gas such as steam or moist air. In these cases, the non-equilibrium condensation may occur at the region between nozzle exit and an object. The jet flow with non-equilibrium condensation may be quite different from that without condensation. Therefore, in this study, the effect of the non-equilibrium condensation of moist air on the axisymmetric under-expanded supersonic impinging jet on a vertical flat plate was investigated numerically.展开更多
Visualisations by LASER topographies and velocity measurements by LDV have allowed the study of the fiow resulting from the illteraction between a circular jet and a cross boundary layer. This type of fiow is dominate...Visualisations by LASER topographies and velocity measurements by LDV have allowed the study of the fiow resulting from the illteraction between a circular jet and a cross boundary layer. This type of fiow is dominated by the presence of many complex vortices that come from the recombining of the vorticity created in the injection tube and that created aIong the chamber floor.展开更多
Detailed unsteady numerical simulation has been carried out to investigate the mechanism of adjacent syntheticjets and the influence of different phases on the mixing of coaxial jets. The results show the combined jet...Detailed unsteady numerical simulation has been carried out to investigate the mechanism of adjacent syntheticjets and the influence of different phases on the mixing of coaxial jets. The results show the combined jet, formedby coupling the vortex pairs at the orifice of two adjacent actuators, can exhibit better controlling effect. Spanwisepressure difference appears because of the existence of phase difference between the left jet and right jet, whichresults in the variation of the combined jet. When the phase difference is greater than zero, mixing enhancementof coaxial jets can be achieved, but there are maximum phase difference and optimal phase difference. On thecontrary, application of adjacent synthetic jets always leads to the mixing reduction when phase difference is lessthan zero.展开更多
文摘This paper presents a fundamental gaskinetic study on high speed rarefied jets expanding into vacuum from a cluster of planar exits.Based on the corresponding exact expressions for one planar jet,this paper straightforwardly derives the combined multiple jet flowfield solutions of density and velocity components,however,for the combined temperature and pressure solutions,extra attention shall be practiced.Several direct simulation Monte Carlo simulation results are provided and they validate these analytical solutions of rarefied planar jet flows.
文摘The concept of joined-wing aircraft with nonplanar wings as conceived and patented by Wolkovitch is attractive due to various advantages such as light weight, high stiffness, low induced drag, high trimmed CLmax, reduced wetted area and parasite drag and good stability and control, which have been supported by independent analyses, design studies and wind tunnel tests. With such foreseen advantages, the present work is carried out to design joined-wing business-jet aircraft and study and investigate its advantages and benefits as compared to the current available conventional business jet of similar size, passenger and payload capacity. In particular, the work searches for a conceptual design of joined-wing configured business-jet aircraft that possesses more superior characteristics and better aerodynamic performance in terms of increased lift and reduced drag, and lighter than the conventional business jet of similar size. Another significant objective of this work is to prove that the added rigidity possessed by the joined wing configuration can contribute to weight reduction.
文摘This paper presents a detailed analysis of the complex flow beneath two impinging jets aligned with a low-velocity crossflow which is relevant for the future F-35 VSTOL configuration, and provides a quantitative picture of the main features of interest for impingement type of flows. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 10^4, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = V/Uo of 22.5. The rear jet is located at S = 6 D downstream of the first jet. The results show a large penetration of the first （upstream）jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The rear jet （located downstream） it is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.
文摘The present paper reports a numerical study of a spray impinging on a surface through a crossflow. This work is intended to study the influence of the spread/splash transition criteria in the modeling of the spray impingement phenomenon. Several experimental correlations available in the literature are inserted in the same base model and the results are tested against experimental data. It can be concluded that the employment of an accurate transition criteria can improve the quality of the results.
文摘The Japanese aircraft industry changed its course in approximately 2007. Mitsubishi Heavy Industry （MHI） Co. launched a project in which regional jets （Mitsubishi Regional Jet （MILl）） reentered the airliner manufacturing market. Honda announced plans to develop, manufacture, and sell small passenger jets, or Honda Jets, in the United States （US） market. This paper summarizes the historical development of the industry using aircraft production statistics and analyzes the patent portfolio strategy from 1995 to 2006, a period in which MHI and Honda accumulated patents for the upcoming market entry. The author uses the following two measurements to evaluate niche widths among aircraft manufacturing companies： the Morishita＇s index and the principal component analysis. The former index is used in population ecology to measure overlapping species. The latter measurement is presented to clarify the validity of the Morishita＇s index. The author identifies MHI as a market leader, Kawasaki Heavy Industry （KHI） Co. as a challenger, Fuji Heavy Industry （FHI） Co. as a follower, and Honda as a nicher in the aircraft patent portfolio strategy in Japan.
文摘In this paper results of previous researches of two-mode full engine model for Mach number range from 3 to 6 are presented. The main aims of researches are to obtain characteristics of full engine model and its components (the inlet, the combustion chamber and the nozzle) in ramjet and scramjet regimes and to compare these characteristics with the calculation results according to CFD and to approximate (engineering) methods. Tests were carried out without ha supply (cold tests) and with fuel supply (study of ignition and combustion).Hydrocarbon and hydrogen fuel (gaseous or liquid) were used during the tests.
文摘Pronounced aeroacoustic resonances are exhibited in the flow field where a jet emerges from an orifice or a nozzle and impinges on a solid surface. One instance where such resonances are produced is in a high speed jet impingement, such as in the space launch vehicle systems, jet-engine exhaust impingement, and in the short take-off and vertical landing （STOVE） aircraft, etc. A highly unsteady flowfield leading to a drastic increase of noise level with very high dynamic pressure and thermal loads are noticed on nearby surfaces results dramatic lift loss, severe ground erosion and hot gas ingestion to the inlet in the jet engines. This highly unsteady behavior of the im- pinging jets is due to a feedback loop between the fluid and acoustic fields. In actual jet flow, the working gas may contain condensable gas such as steam or moist air. In these cases, the non-equilibrium condensation may occur at the region between nozzle exit and an object. The jet flow with non-equilibrium condensation may be quite different from that without condensation. Therefore, in this study, the effect of the non-equilibrium condensation of moist air on the axisymmetric under-expanded supersonic impinging jet on a vertical flat plate was investigated numerically.
文摘Visualisations by LASER topographies and velocity measurements by LDV have allowed the study of the fiow resulting from the illteraction between a circular jet and a cross boundary layer. This type of fiow is dominated by the presence of many complex vortices that come from the recombining of the vorticity created in the injection tube and that created aIong the chamber floor.
基金National Natural Science Foundation of China for-the support projects Grant No.50806006.
文摘Detailed unsteady numerical simulation has been carried out to investigate the mechanism of adjacent syntheticjets and the influence of different phases on the mixing of coaxial jets. The results show the combined jet, formedby coupling the vortex pairs at the orifice of two adjacent actuators, can exhibit better controlling effect. Spanwisepressure difference appears because of the existence of phase difference between the left jet and right jet, whichresults in the variation of the combined jet. When the phase difference is greater than zero, mixing enhancementof coaxial jets can be achieved, but there are maximum phase difference and optimal phase difference. On thecontrary, application of adjacent synthetic jets always leads to the mixing reduction when phase difference is lessthan zero.
