A.1.2.1 Aerodynamic Research and Development

A.1.2.1 Aerodynamic Research and Development

A.1.2.1.1 Wind Tunnel Testing

Wind tunnel testing is essential in any major development process. It gives us data on a scaled down model of our current design.

Drag, lift, and moment characteristics

Dynamic and static stability

Surface pressure distributions

Flow visualization

Wind effects

Heat transfer properties

Acts as a level of redundancy to check against our theoretical methods

We are not using a wind tunnel at the moment since we are in the design phase, but we will be providing data for future work to be done. We need our wind tunnel to be applicable for subsonic, transonic, supersonic, and possibly hypersonic speeds. We also need the wind tunnel to allow for changes in temperature, pressure, and density as we will be moving through different altitudes of our atmosphere where these values will vary and could affect different design parameters.

We also need to take into account the scale effects, flow blockage, presence of the model in the test section, and wall boundary layers. Scale effects: To simulate the real conditions, we must keep the dimensionless parameters constant when building our scaled down model (Reynolds, mach, and prandtl). Blockage: flow blockage occurs in wind tunnels of limited size when testing relatively large models. The blockage is defined as the ratio of the frontal area of the model to the area of the test section. Ideally blockage ratios of less than 5% are necessary for aeronautical testing. The presence of the model in the test section blocks the incoming flow and has the effect of increasing the pressure on the tunnel walls.

Scaled-down model

The size of our scaled down model depends on the wind tunnel we use, and there are definitely a variety of candidates out there for us to use. It needs to take into account the blockage we mentioned earlier. Therefore we investigated 3 different locations, which we chose based on the upper limits of the freestream velocity they could achieve. However, each location also has a different limit to the size of the model we could use in the tunnel and still get useful results.

Location Choices

The three locations are the NASA Glenn Research Center (GRC), located in Cleveland, Ohio, NASALangleyResearchCenter in Hampton, Virginia, and PurdueUniversity in West Lafayette, Indiana. Both Purdue and GRC are able to reach a maximum test section mach number of 6, while Langley is limited to only 5, which could possibly be too low for our particular vehicle. The GRC also provides 10 discrete airspeeds between Mach 1.3 and 6.0 for their 1’x1’ Supersonic Wind Tunnel (SWT) as well as having four more distinct wind tunnels located at the same facility. Table A.1.2.1.1 gives a comparison of the three different tunnels we are looking at, showing parameters which would be important to our future testing.

Table A.1.2.1.1: Hypersonic Wind Tunnel Comparison

Specs
Purdue’s “Quiet” Mach 6 / NASA GRC 1’x1’ SWT / NASA Langley 20 inch SWT
Maximum Test Section Speed (Mach) / 6 / 6 / 5
Simulated Altitude
(km) / -- / 3.35 – 35.05 / --
Test Section Reynolds Number (1/m) / 3e6 – 20e6 / 0.4e6 – 16.5e6 / 5e4 – 20e6
Dynamic Pressure
(kPa) / 616-1862 / 3.83 – 83.8 / 0.191 - 167
Test Section Temperature (K) / 418 / 288.9 - 611 / 297 – 366.48
Maximum Area of the test section (cm2) / 2116 / 929 / 645
Estimated cost
($/hr) / 10 / 34 / --

Purdue’s “Quiet” Mach 6 wind tunnel is the most feasible for testing a scaled down model of our particular launch vehicle. If offers the cheapest running rate, the largest allowable model size, and also proximity since it is located near the main campus in West Lafayette.