Closed Circuit Wind Tunnel

Purchase Description

Procurement of Closed-Circuit Wind Tunnel

Requirements:

• This wind tunnel must be a closed circuit, as the operation of an LDV system

requires seed particles to be added to the air stream – in this case, a substance

called Bis(2-ethylhexyl) subacute. The wind tunnel thus needs to be fitted with a

3/8-inch Swagelok bulkhead fitting placed upstream of the test and transitional

sections.

• This wind tunnel must have a maximum operating speed of approximately 50

meters per second (~9900 feet per minute). The test section walls must have 6.85

millimeter (0.27-inch)-thick grooves placed at approximately 75 percent of the total

length of the test section as measured from the entrance in which specialized

nozzle restriction plates can be affixed to adjust the operating range and achieve

an air speed of 0.15 meters per second (~30 feet per minute). The typical

turbulence intensity across this operating range must be less than 1 percent, where

turbulence intensity is defined as the root-mean-square of velocity fluctuations

divided by the average test section velocity.

• This wind tunnel must have a test section size of 101.6 millimeters by 101.6

millimeters (~4 inches by 4 inches). Test section length can vary if the design

meets the following requirements: The test section must have at least two sealable

ports or fittings for the insertion of instruments of various sizes, such as Pitot-static

tubes and hotwire anemometers. These ports or fittings must accommodate the

following instrument diameters: 4.3 mm (~0.188 in); 6.3 mm (0.25 in); 7.9 mm

(0.313 in); 9.5 mm (0.375 in); 10.1 mm (0.4 in); 12.7 mm (0.5 in); 15.9 mm (0.625

in). One port must be located 49.5 mm (1.95 in) from the inlet, centered into the

test section; the other port should be offset from this port by 37.5 mm (1.47 in).

Additionally, the test section sidewalls must be made of optical-quality glass to

minimize interference with laser propagation. The argon-ion continuous-wave laser

used in this application has a max wavelength of 532 nanometers and 500

milliwatts output power.

• The wind tunnel must have a centrifugal fan design. The fan should be isolated

from the rest of the tunnel system to minimize vibration. The fan must be controlled

by a variable-frequency drive (VFD) connected to a motor of appropriate size and

power to meet the air speed requirements listed above. The VFD must be

implemented such that an operator could use computer software or manual input to

control the drive and automate its function. The computer-VFD interface must not

rely on internet or wireless connections, such as Bluetooth or WiFi. This interface

must be programmable via National Instruments’ LabVIEW software.

• Any design submitted must be shown to meet the specific air speed and

turbulence requirements listed above through a quantitative analysis, such as by

computational fluid dynamics (CFD) simulations or other appropriate methods.

1.0 Delivery Requirements

Shipping Address: U.S. Army TMDE Activity, Attn: Michael Tyler, Building 5435,

Redstone Arsenal, AL 35898