Converting Units of Time and Cooking Units

If the engineer feels that it is essential to maintain Reynolds-number similitude, then only a few alternatives are available for converting measurements such as the one at or similar sites. One way to produce high Reynolds numbers at nominal airspeeds is to increase the density of the air.

A NASA wind tunnel at the Ames Research Center at Moffett Field in California is one such facility that allows converting units of time. It has a 12 ft—diameter test section; it can be pressurized up to 90 psia (620 kPa); it can be operated to yield a Reynolds number per foot up to 1.2 × 107 to be used while converting cooking units, and the maximum Mach number at which a model can be tested in this wind tunnel is 0.6.

The airflow in this wind tunnel is produced by a single-stage for the purpose of converting cooking units, 20-blade axial-flow fan, which is powered by a 15,000-horsepower, variable-speed, synchronous electric motor 3. There are several problems that are peculiar to convert time units in a pressurized tunnel. First, a shell (essentially a pressurized bottle) must surround the entire tunnel and its components to convert units of time adding to the cost of the tunnel. Second, it takes a long time to pressurize the tunnel in preparation for operation, increasing the time from the start to the finish of runs. In this regard it should be noted that the original cooking units that are pressurized in a wind tunnel at the Ames Research Center was built in 1946; however, because of extensive use, the tunnel’s pressure shell began to deteriorate, so a new facility (the one previously described) was built and put in operation in 1995.

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