Comparative Analysis of Aerodynamic Characteristics of F16 and F22 Combat Aircraft using Computational Fluid Dynamics

This paper presents the computational investigation of air flow over an aircraft at realistic speeds while demonstrating the importance of extending the existing analysis to the complete airplane and how pivotal it is in improving its in-flight performance. The study is done for F16 and F22 aircraft using ANSYS Fluent (19.2) to obtain pressure distribution, shear stress distribution and temperature variation on the complete surface of the aircraft. Since the front section of the aircraft is prone to direct initial impact of surrounding environment, this portion is also examined. Here, as the speed is doubled from Mach 1 to Mach 2, a rise in the value of all the three variables is noticed for the F16 aircraft, whereas the pressure distribution for F22 aircraft shows strange behaviour for the highest speed (Mach 2). On comparing the results over the whole surface, it is seen that F16 experiences smaller pressure (29% lower for Mach 1 and 30% for Mach 2), temperature (9.5% lower for Mach 1 and 30% for Mach 2) and shear stress relative to F22 and the stress shows a huge change (90% lower for Mach 1 and 83% for Mach 2). Results of the present study imply that the design of the aircraft highly influences its performance as the parameters discussed touch their limits

Novel concept of tailorable magnetic field and electron pressure distribution in a magnetic nozzle for effective space propulsion

Magnetic nozzle appears to be a practical solution for prolonged space missions. For efficient handling of the spaceship, an in-flight solution to customize the thrust from the magnetic nozzle is essential. Here a new concept of three-thick coils system is proposed for tailoring the magnetic field in-flight in accordance with electron pressure distribution. The role of peak position of the pressure and its axial gradient is also uncovered for realizing higher thrust. About three-fold increase in thrust is observed when the electron temperature is raised to ∼2.5 times of its original value at the exit plane. The set-up is optimized for its best performance and efficient use in the electric space propulsion sector with thrust approaching 5 mN. In particular, this can contribute to the attitude control or the precision pointing of the spacecraft, the technology for removal of space debris and manipulating the ion momentum flux lost to a wall or unsteady laser produced plasma flow in a magnetic nozzle

Tapered coils system for space propulsion with enhanced thrust: a concept of plasma detachment

A concept for plasma detachment in a magnetic nozzle is developed based on the detachment region which is found to decrease with the taper angle of the coils employed in the proposed flexible three coil setup. On tapering the coils while resulting in the same cross-sectional area, the plasma plume outside the throat grows radially that leads to an enhancement in the thrust from 2.67 mN to 5 mN at the final detachment plane for a rise in the taper angle from 0 to 13°. The maximum thrust can reach about 9 mN when the middle coil is shifted closer to the right coil along with increasing middle-to-outer-coil diameter (inner) ratio from 1 to 3. Proposed three-tapered-coils arrangement for a magnetic nozzle turns out to be a robust candidate for space propulsion offering the ability to control plasma detachment and tune thrust in-flight simply via mechanical movements without changing the current

Role of the temporal profile of femtosecond lasers of two different colours in holography

International audienceThe role of the temporal profile of femtosecond lasers in obtaining the holograms isuncovered when two lasers of different colours are used to produce the fringes and recording of holograms. It was shown that the contrast of the time average interference pattern of two short light pulses (pulse duration T ) of different colours is remarkably high for frequency detuning < 2π T (see Odoulov S. et al., Nat. Commun., 6 (2015) 5866). However, we prove that such a continuous range of frequency detuning is not possible but null regions develop and frequency bands are observed for realizing holograms if there is a deviation of the lasers from their Gaussian profiles. The increased pulse duration leads to the generation of additional frequency bands and their narrowing along with higher modulation depth. A shifting of the null regions is noticed for the lasers having different skewness and/or pulse duration

Uncovering remarkable contribution of lasers peak intensity region in holography

International audienceFor the scheme of two colour lasers in interference and holography, we uncover remarkable contribution of focusing region (spread) of the peak intensity of superposing laser beams based on the numerical studies and confirm it by mathematical calculations. The pulses having peak intensity for a wider region create better interference pattern, leading to higher modulation depth. Also, such beams having a stronger intensity gradient enhance the range of frequency detuning (difference), which would ease the experimentation in getting better holograms. A comparison of the results achieved with such beams is done with the most commonly used Gaussian beams for the better understanding of the concept for the advancement in holography