An Experimental Investigation of a Quad Tilt Rotor in Ground Effect

2003 ◽  
Author(s):  
Anand Radhakrishnan ◽  
Fredric Schmitz
Keyword(s):  
Experimental Investigation ◽  
Ground Effect ◽  
Tilt Rotor

Aerodynamic interference test of quad tilt rotor aircraft in wind tunnel

2019 ◽  
Vol 233 (15) ◽  
pp. 5553-5566 ◽  
Author(s):  
Kun Chen ◽  
Zhiwei Shi ◽  
Shengxiang Tong ◽  
Yizhang Dong ◽  
Jie Chen
Keyword(s):  
Wind Tunnel ◽  
Reference Value ◽  
Ground Effect ◽  
Open Loop ◽  
Force Balance ◽  
Scale Model ◽  
Operating Condition ◽  
Tilt Rotor ◽  
Interference Test ◽  
Aerodynamic Interference

There is an obvious aerodynamic interference problem that occurs for a quad tilt rotor in near-ground hovering or in the conversion operating condition. This paper presents an aerodynamic interference test of the quad tilt rotor in a wind tunnel. A 1:35 scale model of the quad tilt rotor is used in this test. To substitute for the ground, a moveable platform is designed in a low-speed open-loop wind tunnel to simulate different flight altitudes of the quad tilt rotor in hovering or forward flight. A rod six-component force balance is used to measure the loads on the aircraft, and the flow field below the airframe is captured using particle image velocimetry. The experimental results show that the ground effect is significant when the hover height above the ground is less than the rotor diameter of the quad tilt rotor aircraft, and the maximum upload of the airframe is approximately 12% of the total vertical thrust with the appearance of obvious fountain flow. During the conversion operating condition, the upload of the airframe is reduced compared with that in the hovering state, which is affected by rotor wake and incoming flow. The aerodynamic interference test results of the quad tilt rotor aircraft have important reference value in power system selection, control system design, and carrying capacity improvement with the advantage of ground effect.

Experimental Investigation of Pairs of Vortex Filaments in Ground Effect

2008 ◽  
Vol 45 (2) ◽  
pp. 622-629 ◽  
Author(s):  
Linda K. Kliment ◽  
Kamran Rokhsaz
Keyword(s):  
Experimental Investigation ◽  
Ground Effect ◽  
Vortex Filaments

Experimental Investigation of the Effect of Camber on the Aerodynamic Characteristics of Airfoils in Ground Effect

2003 ◽  
Author(s):  
M. R. Ahmed ◽  
G. M. Imran ◽  
S. D. Sharma
Keyword(s):  
Experimental Investigation ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Chord Length ◽  
Wake Region ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Large Defect ◽  
Freestream Velocity ◽  
Ground Clearance

In the present paper, results from an experimental investigation of aerodynamic ground effect on two airfoils are presented. The flow characteristics over a symmetrical airfoil (NACA 0015) and a cambered airfoil (NACA 4415) were studied in a low speed wind tunnel. Experiments were carried out by varying the angle of attack from 0° to 10° and ground clearance from zero to one chord length. Pressure distribution on the surface of the airfoil was obtained with the help of pressure tappings. Mean velocity distributions were obtained over the surface of the airfoil. Profiles of mean velocity and turbulence intensity were obtained in the wake region at 0.5 and 1.0 chord length downstream of the trailing edge. It is found that pressure increases on the lower surface as the ground is approached. The flow accelerates over the airfoil, and a considerably higher mean velocity is observed near the suction peak location. For the symmetrical airfoil, the mean velocity over the surface was found to increase by nearly 30%, while for the cambered airfoil, an increase of nearly 60% was recorded for an angle of attack of 7.5°. The flow was found to separate almost near the trailing edge for angles of attack upto 10°, resulting in a thinner wake region and lower turbulence intensities for the symmetrical airfoil; while for the cambered airfoil, an early separation for an angle of attack of 10° was observed. Measurements in the wake region showed a defect in mean velocity profile at the corresponding values of ground clearance. For lower angles of attack, turbulence levels were higher in the wake region for the symmetrical airfoil, while for an angle of attack of 10°, very large defect in velocity was observed for the cambered airfoil model and the minimum velocity reduced to 20% of the freestream velocity.

An Experimental Investigation of Ground Effect on a Quad Tilt Rotor in Hover

2015 ◽  
Vol 60 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Anand Radhakrishnan Mylapore ◽  
Fredric H. Schmitz
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Static Pressure ◽  
Ground Effect ◽  
Pressure Measurements ◽  
Physical Processes ◽  
Tilt Rotor ◽  
Confidence Levels ◽  
Wing Model ◽  
Power Measurements

The performance of a 0.031 geometrically scaled fuselage/wing model of a Quad Tilt Rotor (QTR) operating in helicopter mode while hovering in-ground effect (IGE) and out-of-ground effect (OGE) was experimentally studied. The effect of ground proximity was tested by varying the height of the model above the ground. Measurements included download on the airframe; thrust, torque, and rpm of the rotors; and static pressures along the centerline of the bottom of the fuselage. Fixedpitch propellers were used to model the rotors. The downwash distributions of the rotors were measured and compared well with large-scale V-22 rotor measurements. Tuft flow visualization was used to identify the physical processes causing changes in the download and static pressure measurements. The uncertainty of the measured quantities was determined to 95% confidence levels. A significant download (9 ± 0.5% of the rotor thrust) was observed in hover, OGE. The download reduced substantially IGE and become an upload (8.5 ± 0.5% of the rotor thrust) when the wheels of the QTR were on the ground. Flow visualization and pressure measurements suggest that the upload IGE is caused by the interaction of the wakes from the four rotors that are turned parallel to the ground and meet under the fuselage. The measured download, coupled with power measurements, indicate that for a given power the available vehicle thrust significantly increases IGE.

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