Wind tunnel construction

Evaluation of protective clothing when exposed to toxic and/or corrosive materials in a wind tunnel constructed on-site... 

To a considerable extent, operations research as a formal discipline is occupied with the construction of models. This is closely related to the analysis of alternatives for decision-making. It is generally assumed that it is preferable to have a model to represent an operation, even though it is oversimplified and perhaps imperfect, than to have none. A model may be purely logical or it may be a physical analogue. A mathematical formula is an example of the former, a wind tunnel an illustration of the latter. In both cases, the model provides a ooherent framework for coping with the complexities of a problem. 

Reynolds numbers are of value in the various fields because lesis of models are directly comparable to full-scale results of geometrically similar shapes if the Reynolds ratio for the model equals that of the actual or full-scale project. This has its practical applications in the field of hydrodynamics, in the study of water resistance of hulls or floats, and in the study of water velocities, levee problems, etc., of large rivers. It is used also to establish the best proportions of hydraulic turbines through the use of models. Much of the science of aeronautics rests upon experimental data obtained in wind tunnels. Dangerous inaccuracies might exist in drawing conclusions for actual construction from model tests, unless either the model were, tested at a Reynolds number equal to that of the completed project, or due corrections and allowances were made for the Reynolds number. See also Heat Transfer. 

A wind tunnel is to be constructed to produce flow conditions of Mach 2.8 at Ix = -40°C and p = 0.05 atm. What is the stagnation temperature for these conditions What would be the adiabatic wall temperature for the laminar and turbulent portions of a boundary layer on a flat plate If a flat plate were installed... 

Microfluidics is also a cross-disciplinary subject that uses the methods and principles of microelectronics to construct very small analogs or models of such macroscopic fluidic elements as wind tunnels, valves, or fluidic amplifiers. The natural question that comes to mind is at what dimensional scale does fluid motion depart from the extremely well understood and well established laws of fluid dynamics There is no definitive answer to that question yet since the study of fluid motion in microscale and nanoscale structures is still at an early stage. 

Figure 29.2 shows the schematic diagram of a low-speed, sucfion-type wind tunnel used to simulate the crossflow field at the University of Oklahoma. Overall lengfh of fhe wind tunnel was 1130 cm (38 ), and the test section was 250 cm (8.2 ) long, 58 cm (1.9 ) wide, and 53 cm (1.7 ) high. The inlet section was designed with a contraction ratio of 10. Both side walls of the test section were constructed with 13-mm thick Pyrex glass panels for optical access. The top and bottom panels... 

To test this question, we constructed a three-compartment wind tunnel ( breeze tunnel would be more descriptive) through which air moved at a rate of about 0.3 m /min (Sachs, 1997). Females could be placed upwind or downwind from males, which were always in the center compartment. Partitions between compartments allowed free passage of air and sounds, but prevented direct contact between rats. 

The first indication that the particle size of an aerosol had a significant effect upon the biological behaviour of the material contained in the aerosol came from the work of May and Druett who constructed a vertical wind tunnel into which particles of controlled size could be sprayed into a dynamic airstream. By its use they were able to show that a 1 im diameter droplet of Bacillus anthracis was more effective in creating infection in guinea pigs than in a 12 im particle. Later they reported that a 1 im diameter droplet of Brucella suis was 800 times more effective than a 12 pim diameter droplet. Similar results were obtained with F. tularensis. 

Studies are currently underway to select materials and fabrication methods for construction of glass-epoxy fan blades for the National Transonic Facility wind tunnel at NASA-Langley. Having a span of about 68 cm and an airfoil section of about 0.6 m, they... 

The vertical spindle, three blade machine [Fig. 12.11 and curve (E) in Fig. 12.10] is a high-speed wind turbine having blades in the shape of airfoil sections like an aircraft propeller. However, instead of having vertical blades, they are bowed to form a catenary thus eliminating the bending moments that straight vertical blades would experience. The peak efficiency of the three blade machines is about 42% at a speed ratio of about six. This means that great care of construction is required for these machines, as in the case of conventional two blade horizontal-axis propellers. A 14 ft diameter machine, tested in a wind tunnel, had an output of 0.65 hp at 130 rpm with a wind speed of 18.2 fps. 

A typical wind tunnel used to assay insect behavior to pheromones is shown in Figure 5.3. A more complete description of its design and construction can be found in Miller and Roelofs (1978). Fundamental components are a variable-speed fan to generate an airstream, an expansion duct to lower the velocity of the stream to that appropriate for the test subject, a screen or diffuser to eliminate the circular turbulence generated by the fan, and the tunnel itself with windows for access and observation. The total length usually is 2-3 m. For most insects,... 

Surfaces that are likely to come into contact with test semiochemicals should be made of material that is either disposable or easily cleaned, such as metal, glass, or solvent-resistant, nonporous plastics, such as Plexiglas . The use of porous materials, such as wood, should be confined to parts that do not come into contact with the test semiochemicals (see Baker Linn 1984 for a more detailed discussion of wind tunnel design and construction for specific applications). 

A second investigation (Wentz and Thodos, 1963a, 1963b), carried out at much higher particle Reynolds numbers, involved air, a standard wind tunnel and cubical arrays of 31 mm spheres joined together by means of fine wires. Five such assemblies were constructed, void fractions ranging from 0.48 to 0.88. 

Despite the general outdoor nature of the work, construction workers are not immune from the hazards of airborne contaminants. Although natural wind movement will dilute dust and fumes throughout the site, operatives engaged on particular processes may have a dangerous concentration in their immediate breathing zones unless suitable extraction is provided. This is particularly relevant for work in shafts, tunnels and other confined spaces where forced draught ventilation may have to be provided. 

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