scholarly journals Effects of forward velocity on noise for a J85 turbojet engine with multi‐tube suppressor from wind tunnel and flight tests

1976 ◽  
Vol 60 (S1) ◽  
pp. S113-S113 ◽  
Author(s):  
J. R. Stone ◽  
J. H. Miles ◽  
N. B. Sargent
2010 ◽  
Vol 114 (1158) ◽  
pp. 485-492 ◽  
Author(s):  
A. Watkins ◽  
M. Thompson ◽  
M. Shortis ◽  
R. Segal ◽  
M. Abdulrahim ◽  
...  

Abstract Aspects of the turbulent wind environment Micro Air Vehicles (MAVs) experience when flying outdoors were replicated in a large wind tunnel. An overview of the facility, instrumentation and initial flight tests is given. Piloting inputs and aircraft accelerations were recorded on fixed and rotary wing MAVs and for some tests, measurements of the approach flow (u,v,w sampled at 1,250Hz at four laterally disposed upstream locations) were made. The piloting aim was to hold straight and level flight in the 12m wide × 4m high × ~50m long test section, while flying in a range of turbulent conditions. The Cooper-Harper rating system showed that a rotary craft was less sensitive to the effects of turbulence compared to the fixed wing craft and that while the fixed wing aircraft was relatively easy to fly in smooth air, it became extremely difficult to fly under high turbulence conditions. The rotary craft, while more difficult to fly per. se., did not become significantly harder to fly in relatively high turbulence levels. However the rotary craft had a higher mass and MOI than the fixed wing craft and further work is planned to understand the effects of these differences.


Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 553 ◽  
Author(s):  
Taimur Ali Shams ◽  
Syed Irtiza Ali Shah ◽  
Ali Javed ◽  
Syed Hossein Raza Hamdani

Airfoil selection procedure, wind tunnel testing and an implementation of 6-DOF model on flying wing micro aerial vehicle (FWMAV) has been proposed in this research. The selection procedure of airfoil has been developed by considering parameters related to aerodynamic efficiency and flight stability. Airfoil aerodynamic parameters have been calculated using a potential flow solver for ten candidate airfoils. Eppler-387 proved to be the most efficient reflexed airfoil and therefore was selected for fabrication and further flight testing of vehicle. Elevon control surfaces have been designed and evaluated for longitudinal and lateral control. The vehicle was fabricated using hot wire machine with EPP styrofoam of density 50 Kg/ m 3 . Static aerodynamic coefficients were evaluated using wind tunnel tests conducted at cruise velocity of 20 m/s for varying angles of attack. Rate derivatives and elevon control derivatives have also been calculated. Equations of motion for FWMAV have been written in a body axis system yielding a 6-DOF model. It was found during flight tests that vehicle conducted coordinated turns with no appreciable adverse yaw. Since FWMAV was not designed with a vertical stabilizer and rudder control surface, directional stability was therefore augmented through winglets and high wing leading edge sweep. Major problems encountered during flight tests were related to left rolling tendency. The left roll tendency was found inherent to clockwise rotating propeller as ‘P’ factor, gyroscopic precession, torque effect and spiraling slipstream. To achieve successful flights, many actions were required including removal of excessive play from elevon control rods, active actuation of control surfaces, enhanced launch speed during take off, and increased throttle control during initial phase of flight. FWMAV flew many successful stable flights in which intended mission profile was accomplished, thereby validating the proposed airfoil selection procedure, modeling technique and proposed design.


This paper describes a transformation in time which reduces the equation governing the acoustic velocity potential, in a steady homentropic potential flow at low Mach number, to an ordinary wave equation. The transformation is applied when the basic flow is a uniform stream flowing past a fixed body. It is shown that, in coordinates fixed in the body, the flow has a very simple effect on the far field generated by a stationary compact sound source. This has important implications for the analysis of noise measurements from wind-tunnel and low-speed flight tests. The method can be extended to cases where the body surface is weakly vibrating.


Author(s):  
Guo-Zheng Song ◽  
Hua Liang ◽  
Wei Biao ◽  
Su Zhi ◽  
Xie Like ◽  
...  

As a new kind of active flow control technology, plasma flow control has a bright future, for its simple structure, fast response, and wide frequency band. The wind tunnel and flight tests were conducted with microsecond dielectric barrier discharge on a glider. For the tests, the microsecond pulse power supply and remote control system were designed and built. In the wind tunnel test, the flow separation on the glider wing surface can be controlled effectively, and static pressure at the leading edge pressure is decreases by 177%. The flow control effects under different pulse frequencies are compared, and the optimal pulse frequency for actuation is found to be 100 Hz. A significant hysteresis effect was observed with microsecond dielectric barrier discharge at small angle of attack (α ≤ 18°), which means the flow control effect can last more than 300 s after turning off the plasma actuation. In the flight test, the maximum roll angle decreases by 7.0°, and the maximum aileron deflection angle decreases by 9.4° with plasma actuation at both sides of the wing, which means the glider becomes more stable with microsecond dielectric barrier discharge. With unilateral actuation, the rolling moment generated by the plasma actuation is larger than that produced by the ailerons with the angle of attack within 12.94° ≤ α ≤ 29.77°, which shows strong rolling control ability of microsecond dielectric barrier discharge. The wind tunnel and flight tests results verified the flow control effect of microsecond dielectric barrier discharge, and paved the way for the plasma flow control technology to practical applications.


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