A Small Wind Tunnel Significantly Improved by a Multi-Purpose, Two-Flexible-Wall Test Section

1994 ◽  
Vol 116 (3) ◽  
pp. 419-423 ◽  
Author(s):  
P. Kankainen ◽  
E. Brundrett ◽  
J. A. Kaiser
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Test Section ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Free Data ◽  
Wall Panels ◽  
Testing Data ◽  
Flexible Wall ◽  
Flow Quality

A small open-return wind tunnel has been renovated to include a longer test section with a flexible roof and floor and improved entrance flow quality. The flexible-wall test section allows models with up to 30 percent nominal blockage to be tested, resulting in a significant increase in the maximum attainable Reynolds numbers. Interchangeable rigid side-wall panels allow flexibility of application which is essential for a university wind tunnel facility. Configurations have been developed for automotive, aerodynamic and atmospheric-boundary-layer testing. Data acquisition and wall positioning are at an economical semi-automated level of operation. The flexible-wall concept has been well-documented previously, and provides interference-free data without flow pattern assumptions after a few iterations of the roof and floor shape. Representative data are presented for a circular cylinder and an airfoil.

Design and Performance of a Hypersonic Wind Tunnel

2017 ◽  
Author(s):  
Jesse Maxwell
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Wind Tunnel ◽  
Test Section ◽  
Dynamic Pressure ◽  
Continuous Variation ◽  
Axisymmetric Nozzle ◽  
Aspect Ratios ◽  
Tunnel Design ◽  
Flow Quality

A moveable block planar nozzle wind tunnel design from the University of Michigan in 1955 was shown with previous analysis to operate between Mach 1 and at least Mach 6.3 for mid-size test sections, with continuous variation in Mach number and accounting for limitations governed by supply temperature and pressure, liquefaction, flow rate, and flow quality for a desired dynamic pressure or Reynolds number. The moveable block planar nozzle design allows for continuous variation of Mach number, based on a Method of Characteristics solution to a convergent-divergent nozzle with a boundary layer correction. The present work summarizes the design considerations and hardware performance requirements for such a tunnel in the blowdown configuration, with a comparison between cold and hot operation for various test section sizes and supply conditions. The flow quality is compared between a two planar nozzles and an axisymmetric nozzle for a 12×12[in] test section, the effect of physical scaling on flow quality and boundary layer encroachment is investigated across scales of 1×1” to 12×12” test sections at Mach 5, and the merits of planar nozzle aspect ratios greater than unity are presented and discussed.

Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

2020 ◽  
Vol 32 (12) ◽  
pp. 125120
Author(s):  
María Jiménez-Portaz ◽  
Luca Chiapponi ◽  
María Clavero ◽  
Miguel A. Losada
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Air Flow ◽  
Open Circuit ◽  
Closed Circuit ◽  
Quality Analysis ◽  
Flow Quality

scholarly journals Simulations of the Atmospheric Boundary Layer in a Wind Tunnel with Short Test Section

2013 ◽  
Vol 5 (3) ◽  
pp. 305-314 ◽  
Author(s):  
Luciana Bassi Marinho Pires ◽  
Igor Braga De Paula ◽  
Gilberto Fisch ◽  
Ralf Gielow ◽  
Roberto Da Mota Girardi
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Test Section ◽  
Short Test

Transition detection for laminar flow aircraft using microphones beneath the surface of laser drilled suction panels

2000 ◽  
Vol 214 (3) ◽  
pp. 143-155
Author(s):  
R V Barrett
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
Suction Surface ◽  
Microphone Signal ◽  
High Background ◽  
Low Reynolds Numbers ◽  
High Background Noise ◽  
Suction Flow

The possibility of detecting transition through the very small laser drilled perforations in panels representing the suction surface of a hybrid laminar flow aircraft is examined. The method uses miniature microphones to detect changes to the noise received from the boundary layer. Tests using a flat plate rig in a low-turbulence wind tunnel at Reynolds numbers up to 3.8 million per metre, demonstrate that the boundary layer state can be defined in this manner, most simply through measurement of the root mean square (r.m.s.) of the microphone signal. It is shown that the r.m.s. reaches a peak in the transition zone and that when the boundary layer is fully turbulent the value is still significantly higher than it was before transition. Porosity in the range 0.8-6.4 percent was examined, with nominal hole diameters of 0.06 and 0.10 mm in 0.9 mm thick laser drilled suction surface specimens. Suction flow through the surface was found not adversely to affect the operation of the system. The experiment was limited to low Reynolds numbers because the high background noise in the wind tunnel made detection of the boundary layer element of the signal increasingly difficult to define as speed increased. It is considered that test in flight will be needed to prove fully the validity of the method. A preliminary design of an installation for this purpose is suggested that allows the suction flow to be maintained over the measuring region.

Control of separation in the concave portion of contraction to improve the flow quality

2009 ◽  
Vol 113 (1141) ◽  
pp. 177-182 ◽  
Author(s):  
K. Ghorbanian ◽  
M. R. Soltani ◽  
M. D. Manshadi ◽  
M. Mirzaei
Keyword(s):  
Wind Tunnel ◽  
Pressure Distribution ◽  
Turbulence Intensity ◽  
Test Section ◽  
Adverse Pressure Gradient ◽  
Wind Tunnel Experiments ◽  
Free Stream Turbulence ◽  
Static Pressure Distribution ◽  
Subsonic Wind Tunnel ◽  
Flow Quality

AbstractSubsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip strip. The results confirm the significant impact of the tripped boundary layer on the control of adverse pressure gradient. The trip strip atX/L= 0.115 improves pressure distribution in contraction and reduces turbulence intensity in the test section, considerably.

A new boundary layer wind tunnel

1988 ◽  
Vol 92 (916) ◽  
pp. 224-229
Author(s):  
P. E. Roach
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Test Section ◽  
Gas Turbines ◽  
Large Scale ◽  
Free Stream ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Dimensional Boundary

Summary The procedures employed for the design of a closed-circuit, boundary layer wind tunnel are described. The tunnel was designed for the generation of relatively large-scale, two-dimensional boundary layers with Reynolds numbers, pressure gradients and free-stream turbulence levels typical of the turbomachinery environment. The results of a series of tests to evaluate the tunnel performance are also described. The flow in the test section is shown to be highly uniform and steady, with very low (natural) free-stream turbulence intensities. Measured boundary layer mean and fluctuating velocity profiles were found to be in good agreement with classical correlations. Test-section free-stream turbulence intensities are presented for grid-generated turbulence: agreement with expectation is again found to be good. Immediate applications to the tunnel include friction drag reduction and boundary layer transition studies, with future possibilities including flow separation and other complex flows typical of those found in gas turbines.

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