scholarly journals 309 Boundary-Layer Transition on a Wing in Ground Effect

2008 ◽  
Vol 2008.44 (0) ◽  
pp. 91-92
Author(s):  
Yuichiro Saiki ◽  
Yoshihiro Yamaguchi ◽  
Toshiyuki Arima ◽  
Takuma Kato ◽  
Yasuaki Kohama
Keyword(s):  
Boundary Layer ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Wing In Ground Effect

scholarly journals Forcing Boundary-Layer Transition on a Single-Element Wing in Ground Effect

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Luke S. Roberts ◽  
Mark V. Finnis ◽  
Kevin Knowles
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Single Element ◽  
Trailing Edge ◽  
Layer Transition ◽  
Transition Mechanism ◽  
Edge Separation ◽  
Wing In Ground Effect

The transition from a laminar to turbulent boundary layer on a wing operating at low Reynolds numbers can have a large effect on its aerodynamic performance. For a wing operating in ground effect, where very low pressures and large pressure gradients are common, the effect is even greater. A study was conducted into the effect of forcing boundary-layer transition on the suction surface of an inverted GA(W)-1 section single-element wing in ground effect, which is representative of a racing-car front wing. Transition to a turbulent boundary layer was forced at varying chordwise locations and compared to the free-transition case using experimental and computational methods. Forcing transition caused the laminar-separation bubble, which was the unforced transition mechanism, to be eliminated in all cases and trailing-edge separation to occur instead. The aerodynamic forces produced by the wing with trailing-edge separation were shown to be dependent on trip location. As the trip was moved upstream the separation point also moved upstream, this led to an increase in drag and reduction in downforce. In addition to significant changes to the pressure field around the wing, turbulent energy in the wake was considerably reduced by forcing transition. The differences between free- and forced-transition wings were shown to be significant, highlighting the importance of modeling transition for ground-effect wings. Additionally, it has been shown that while it is possible to reproduce the force coefficient of a higher Reynolds-number case by forcing the boundary layer to a turbulent state, the flow features, both on-surface and off-surface, are not recreated.

305 Boundary-Layer Transition on a Swept Wing in Ground Effect

2009 ◽  
Vol 2009.45 (0) ◽  
pp. 81-82
Author(s):  
Takuma KATO ◽  
Yuichiro SAIKI ◽  
Yoshihiro YAMAGUCHI ◽  
Toshiyuki ARIMA ◽  
Yasuaki KOHAMA
Keyword(s):  
Boundary Layer ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Swept Wing ◽  
Layer Transition ◽  
Wing In Ground Effect

Forcing Boundary-Layer Transition on an Inverted Airfoil in Ground Effect at Varying Incidence

2016 ◽  
Author(s):  
Luke S. Roberts ◽  
Mark Finnis ◽  
Kevin Knowles ◽  
Nicholas J. Lawson
Keyword(s):  
Boundary Layer ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Layer Transition

Measurement of ground effect and boundary-layer transition by towing wind tunnel

2009 ◽  
Vol 41 (2) ◽  
pp. 021408 ◽  
Author(s):  
Shuya Yoshioka ◽  
Satoshi Kikuchi ◽  
Fukuo Ohta ◽  
Takuma Kato ◽  
Jun Song ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Layer Transition

scholarly journals Characteristics of Boundary-Layer Transition and Reynolds-Number Sensitivity of Three-Dimensional Wings of Varying Complexity Operating in Ground Effect

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Luke S. Roberts ◽  
Mark V. Finnis ◽  
Kevin Knowles
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Separation Bubble ◽  
Ground Effect ◽  
Surface Flow ◽  
Boundary Layer Transition ◽  
Single Element ◽  
Suction Surface ◽  
Layer Transition ◽  
Reynolds Number Dependency

The influence of Reynolds number on the aerodynamic characteristics of various wing geometries was investigated through wind-tunnel experimentation. The test models represented racing car front wings of varying complexity: from a simple single-element wing to a highly complex 2009-specification formula-one wing. The aim was to investigate the influence of boundary-layer transition and Reynolds-number dependency of each wing configuration. The single-element wing showed significant Reynolds-number dependency, with up to 320% and 35% difference in downforce and drag, respectively, for a chordwise Reynolds number difference of 0.81 × 105. Across the same test range, the multi-element configuration of the same wing and the F1 wing displayed less than 6% difference in downforce and drag. Surface-flow visualization conducted at various Reynolds numbers and ground clearances showed that the separation bubble that forms on the suction surface of the wing changes in both size and location. As Reynolds number decreased, the bubble moved upstream and increased in size, while reducing ground clearance caused the bubble to move upstream and decrease in size. The fundamental characteristics of boundary layer transition on the front wing of a monoposto racing car have been established.

Helicopter Rotor Boundary Layer Transition Measurement in Forward Flight Using an Infrared Camera

2020 ◽  
Vol 65 (1) ◽  
pp. 2-14 ◽  
Author(s):  
A. D. Gardner ◽  
C. C. Wolf ◽  
J. T. Heineck ◽  
M. Barnett ◽  
M. Raffel
Keyword(s):  
Boundary Layer ◽  
Infrared Camera ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Helicopter Rotor ◽  
Forward Flight ◽  
Layer Transition ◽  
Pitching Airfoil ◽  
Transition Position ◽  
The Difference

Boundary layer transition measurement was demonstrated using differential infrared thermography (DIT) on the top side of a helicopter rotor in forward flight, which detects the difference in the convective heat transfer at the boundary layer transition position. The tests used a FLIR X8500xc SLS long wave infrared camera to observe the DLR EC135 test helicopter rotor. The boundary layer transition was detected for hover out of ground effect (150 ft) and for forward flight at 80 kt (1700 ft). The measured boundary layer transition positions are consistent with previous measurements of the EC135 hovering in ground effect, and with predicted boundary layer transition positions. A method for the analysis of DIT images for a rotor in forward flight is shown, based on computational analysis of a pitching airfoil with varying inflow.

scholarly journals Forcing Boundary-Layer Transition on an Inverted Airfoil in Ground Effect

2017 ◽  
Vol 54 (6) ◽  
pp. 2165-2172 ◽  
Author(s):  
L. S. Roberts ◽  
M. V. Finnis ◽  
K. Knowles ◽  
N. J. Lawson
Keyword(s):  
Boundary Layer ◽  
Ground Effect ◽  
Boundary Layer Transition ◽  
Layer Transition
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