Background Image

Subsonic Wind Tunnel Facility

In this Section

The Clarkson University subsonic wind tunnel facility uses an Eiffel type, open circuit wind tunnel consisting of the contraction, test section, diffuser, and power section.  The contraction has a ratio of 8:1 and uses honeycomb with fine screens mounted across the entrance to reduce turbulence and flow irregularities.  The test section measures 1.22 m wide by .91 m tall (48 in. by 36 in.) with a length of 1.67 m (66 in.).  The diffuser section expands the flow downstream of the test section through a 9 m length (354in).  The tunnel power section, located at the diffuser outlet, is a 2.1 m (84 in.) vaneaxial fan with 16 adjustable blades.  Speed control of the 150 HP, 3-phase AC induction motor is through an ABB Variable Frequency Drive (VFD).  The maximum speed obtainable in the tunnel is approximately 70 m/s (~ 150 mph).

In addition to this tunnel, the new wind tunnel at Clarkson University’s Center for Air Resources Engineering and Science (CARES) is a low-speed, Eiffel type open-circuit system capable of producing wind speeds between 2 and 30 mph.  The tunnel will simulate atmospheric conditions for the development of new tools in modeling, measurement, and flow management. 

The 60-foot long tunnel is made of fiberglass reinforced plastic with a balsa wood core for reduced vibration and acoustic attenuation. Air is moved through the tunnel by a large axial fan and impurities are removed from the air through 62 HEPA filters.

The test section dimensions are 48” wide x 36” tall x 60” long.  The ceiling, floor and sidewalls are 1” thick SAR grade acrylic; Air flow rates from less than 1m/s to more than 12 m/s; Inlet air quality is established through 228 sq. ft. of HEPA filter; Fibrous and spherical aerosols ranging from 1 nm to 100 micrometers can be introduced into the air-stream; The tunnel design uses fiberglass reinforced plastic with a balsa wood core for reduced vibration and acoustic attenuation. In 2007, the wind tunnel was outfitted with a removable duct to discharge flow outside the building.  This modification will support experimentation with automotive/diesel emissions without affecting the internal air quality.

 A 3D traversing system (+/- 0.083mm) has been recently built for the two tunnel, and the use of various probes, such as a seven-hole probe or a hot wire probe enable measurements of time averaged and fluctuating velocities and pressures respectively. Equipment availability also includes a 3D stereoscopic PIV System and typical flow visualization techniques.

 Wind Tunnel LDV / PDPA System Capabilities

The pre-configured three-component (3D) LDV system is used to get all three components of velocity, simultaneously. The fiberoptic transceiver probes offer point-and-shoot velocity measurement capability, with large 61 mm collection apertures. The probes are attached to convenient rotating mounts for easy setup. Alignment devices are included for obtaining high coincident data rates. Processing electronics have been pre-selected and configured for a wide range of velocity measurements.

The LDV measuring point can be traversed using a traverse system. The traverse, running under software control, can automatically move the measuring point while optimally selecting the system operating parameters at each location. This provides a fully automated, optimized measurement system for mapping the flow field.

The pre-configured three-component (3D) LDV system is used to get all three components of velocity, simultaneously. The fiberoptic transceiver probes offer point-and-shoot velocity measurement capability, with large 61 mm collection apertures. The probes are attached to convenient rotating mounts for easy setup. Alignment devices are included for obtaining high coincident data rates. Processing electronics have been pre-selected and configured for a wide range of velocity measurements.

The LDV measuring point can be traversed using a traverse system. The traverse, running under software control, can automatically move the measuring point while optimally selecting the system operating parameters at each location. This provides a fully automated, optimized measurement system for mapping the flow field.

•     Non-invasive measurement

•     Measurements independent of the properties of the fluid

•     Velocity dynamic range over 108 possible (10-6 m/s to 102 m/s)

•     Two probe system for better three-component measurements 

•     Versatile probe positioning - separate receiving and transmitting optics can be configured for backscatter or forward scatter applications

•     Fiberoptic probes allow precision placement of receivers when making accurate near-wall and turbulence intensity measurements

•     Flow Size Analyzer (FSA) signal processor automatically optimizes sampling rate for each burst

•     High Doppler frequency resolution (100 MHz)

•     8 Bit analog to digital burst resolution

•     Internal calibration with diode laser

•     FSA software provides power spectrum of velocity field

•     External synchronizer input for triggered data acquisition

•     3 Axis traversing system with a 1250 mm x 1000 mm x 1000 mm range of motion

The wind tunnel can be retrofitted with different size shrouds to test rotors for advanced performance and comparative studies up to 8 feet diameter. The facility is also equipped with electronic load controller to test up to 5 kW, data acquisition system, flow measurements systems. 

Model Fabrication - Stereolithography

Stereolithography is a process of fabricating prototypes using CAD data to build a solid from thin, cross-sectional layers. The layers are formed using a solid-state laser to harden the surface of a photopolymer contained within a vat.  The laser beam is moved in the X-Y directions by a scanner system.  The fast and highly controllable motors which drive mirrors are guided by information from the CAD data.  After a layer is completely traced and for the most part hardened by the laser beam, a table is lowered within the vat a distance equal to the thickness of one layer.  Upon completion the model is elevated from the vat and allowed to drain. Excess resin is removed from exposed surfaces by washing or wiping the surfaces with alcohol. The model is then given a final cure in a cabinet called a Post-Curing Apparatus (PCA), where it is bathed in ultraviolet light.  The additional curing time will harden any resin within a trapped volume and any exposed surfaces before any sanding or polishing is performed. This is particularly useful in that the cost of model construction with internal channels required for such a control technique to be explored is no more challenging to build than a solid object.

http://www.clarkson.edu/rapidprototype/docs/Stereolithography_Pres.ppt

Clarkson is using a Viper Si2 ® SLA system with the epoxy resin, DSM 11120, supplied by DSM Somos of New Castle, DE. The laser beam for the 3D Systems Viper Si2 ® under standard resolution has a diameter of .250 mm (.01 inch) and a build layer capability of .10mm. (.004 inch).  The maximum build volume in normal resolution is a 254mm (10 inch) cube.  Using the high resolution setting, the laser beam has diameter is .075 mm (.003 inch) and a build layer capability of .051mm (.002 inch).  The build volume in high resolution is a square column with 127mm (5 inch) sides and is 254mm (10 inch) tall.