The characteristics of a subsonic nozzle with Fluidic Thrust Vectoring (FTV) in the pitch angle are investigated experimentally using a wind tunnel. The transient response of the FTV nozzle is also tested by mounting it on an aircraft flying at 25m/s. The FTV nozzle is designed so that a secondary jet branched from the main flow is joined at the nozzle throat and the main flow is separated from the nozzle wall surface. The deflection angle and deceleration rate of the main flow are measured with a pitot tube, and flow is visualized using a laser light sheet. The deflection angle without ventilation to the wind tunnel is up to 14deg at 100% throttle. When the FTV nozzle is operated in an air stream of 11m/s in a wind tunnel, the deflection angle is suppressed to 40%. In addition, the flight test demonstrates that the system can be used to control the flight attitude in pitch angle. During flight, there are transient delays of 1.5 seconds in pitch angle and 3 seconds in flight altitude.
General transonic similarity rules and the similarity rules around Mach 1 on the aerodynamic coefficients of quasi-cylindrical bodies including biplanes are developed to extract the characteristic dimensionless quantities for flowfields around transonic biplanes. To verify the similarity rules, numerical simulations of biplane airfoils are performed by solving the Euler equations. Two RAE2822 airfoils are used in the simulations as typical transonic airfoils. The results of the numerical simulations show good agreement with the similarity rules even if there is shock wave interaction between the wings. Furthermore, shock wave patterns are the same when the values of similarity parameters are the same. These results illustrates the potential of the similarity rules for searching wide range of design space and classifying the shock wave patterns. Applying similarity rules to biplane airfoils in transonic flows, the relationship between the distance of the wings in the uniform flow direction and aerodynamic coefficients are numerically investigated. The result show that the lift-to-drag ratio is large when the upper wing is placed upstream of the lower wing.
An external nozzle is one of the altitude compensating nozzle for a wide range operating airframe like RLV (Reusable Launch Vehicle). This paper explores the possibility of simplifying thrust calculations of the external nozzle for a series of flight operations. We focused on a replacement of some 2D thrust calculations with a method at a low computation cost in thrust performance evaluation along a trajectory of RLV equipped with the external nozzle. The replacement is determined by threshold conditions of jet Mach number and slip line angle. Since strict calculation of the threshold conditions takes expensive computational cost, calculating models of the threshold conditions were constructed. These models were able to predict the threshold conditions with an error of 4% or less. Then, the models were applied to the calculation for 2604 nozzle shapes and 191 points along a trajectory of TSTO (Two Stage To Orbit) booster. Thrust calculations of 86% conditions were replaced by the method with low computational cost, so that the models proposed in this work demonstrated the achievement of simplification.
Interaction between a rocket exhaust plume and a flame deflector causes intense acoustic waves during a launch vehicle liftoff. The prediction and the reduction of these waves are quite important for the safe transportation of the payloads. Past studies discussing acoustic phenomena of a supersonic axisymmetric jet impinging on an inclined flat plate reported three types of acoustic waves, and also indicated that interaction between the large scale disturbance at the shear layer and the flowfield can be attributable to the acoustic wave generation. However, the generation mechanism of the acoustic wave perpendicular to the plate has not been clarified. In this study, a supersonic impinging planer jet overlayed with an isolated disturbance is simulated numerically and the resulting acoustic waves are discussed in detail. The numerical result shows three acoustic waves similar to those observed in Akamine et al.'s experiment. These waves seem to be generated from the interaction between the disturbance convected over the shear layer and the near-wall shock structures.
Inverse Vortex Lattice Method (IVLM) was applied to calculate the optimum spanwise lift distributions of nonplanar wings. IVLM is a tool to calculate the circulation distribution which achieves the minimum induced drag for each wing configuration mathematically. It is based on Kroo's method which is using Lifting Line Theory. IVLM takes effects of sweep back angle and airfoil camber into consideration by applying VLM. In this study, IVLM validity is confirmed through evaluating span loadings of rectangular wings and swept back wings with and without winglets. The characteristic of IVLM is also examined and it is indicated that equal intervals are required for spanwise panel divisions to calculate proper twist and lift distributions.
Transonic buffet is self-induced oscillation of shock waves appeared on a suction side of a wing. We simulated the transonic buffet over the NASA Common Research Model (CRM) wing, which is an open geometry, generic transport model, and characterized its variation in spanwise direction. The numerical method employed in this simulation was a zonal detached eddy simulation (ZDES), which is a RANS/LES hybrid method. The numerical results indicate that the frequency spectra of oscillation on the surface pressure were varied in spanwise direction and were categorized into three patterns. In the inboard region, buffet exhibits a periodical oscillation having a single dominant frequency equivalent to the 2D wing. At the mid-span of the wing, the wavefront of shock moves due to the existence of the angle of sweepback. In the outboard, the spectrum exhibits multiple dominant modes due to superposition of two difference sources. One is a periodical oscillation similar to the 2D wing. The other is pressure oscillation propagating from the inboard region.