No abstract

The difference of the aerodynamic influence of two engine models -the Flow Through Nacelle (FTN) and With Powered Nacelle (WPN) -on BWB300 airframe is analyzed by using the 3-D unsteady compressible Reynolds-Averaged Navier-Stokes (RANS) computation. The results indicate that at cruise condition, the engine shape is a primary factor affecting the BWB airframe upper fuselage surface flow, the two engine models exhibit a similar aerodynamic influence on the BWB airframe. However, at takeoff condition, the two engine models' aerodynamic influence on the airframe is different, because of the air suction caused by the WPN engine model affecting the airframe upper fuselage surface flow obviously. Moreover, at both cruise and takeoff conditions, the tube formed by the engine and airframe shape changes the surface flow under the engine and the air suction caused by the engine power accelerates the surface flow near the engine. ARTICLE HISTORY

No abstract

Airplane thrust reverser could significantly reduce the landing distance of a conventional civil turbofan. Control of the thrust reverser can be performed by a hydraulic and/or electric system. This study investigates whether this system can be used for blended wing body (BWB) civil airplanes as their engines are located over the wing body. Computational fluid dynamics (CFD) is used to analyze the feasibility of a thrust reverser cascade applied to BWB airplanes. This is selected because of its rapidity and low cost when compared to traditional wind tunnel tests. Analyses are performed on a 300-seating BWB (BWB300) landing configuration. The results show that the thrust reverser cascade can be applied to BWB300. Furthermore, the results also reveal that the probability of foreign object damage problems occurring during the BWB300 landing process when the thrust reverser cascade is working is low. Increasing the reverse mass flow component along the landing reverse direction can increase the thrust reverser efficiency. However, this would also increase the thrust reverser closing velocity. Therefore, when the thrust reverser design is performanced for BWB, a tradeoff between the efficiency and closing veloctiy should be considered.INDEX TERMS Blended wing body, cascade thrust reverser, CFD, landing configuration.

Environmental crosswind can greatly affect the development of aircraft wake vortex pair. Previous numerical simulations and experiments have shown that the nonlinear vertical shear of the crosswind velocity can affect the dissipation rate of the aircraft wake vortex, causing each vortex of the vortex pair descent with different velocity magnitude, which will lead to the asymmetrical settlement and tilt of the wake vortex pair. Through numerical simulations, this article finds that uniform crosswind convection and linear vertical shear crosswind convection can also have an effect on the strength of the vortex. This effect is inversely proportional to the cube of the vortex spacing, so it is more intense on small separation vortex pair. In addition, the superposition of crosswind and vortex-induced velocities will lead to the asymmetrical pressure distribution around the vortex pair, which will also cause the tilt of the vortex pair. Furthermore, a new analysis method for wake vortex is proposed, which can be used to predict the vortex trajectory.