Spindrift Spindrift Spindrift (more rarely spoondrift) usually refers to spray, particularly to the spray blown from cresting waves during a gale. This spray, which "drifts" in the direction of the gale, is one of the characteristics of a wind speed of 8 Beaufort and higher at sea. In Great Britain "spindrift" is the telltale sign used by mariners to define a Force 8 (Beaufort Scale) wind (not higher) when observed at sea. See this example of information provided by Lymington Harbour authority, Hampshire, England, UK, explaining the whole scale, the associated wind speeds, and its telltale signs. Text from the site
Subsonic and transonic wind tunnel interactions occur (such as shock waves or boundary layer interaction) both Mach and Reynolds number are important and must be properly simulated. Large-scale facilities and/or pressurized or cryogenic wind tunnels are used. With a sonic throat, the flow can be accelerated or slowed down. This follows from the 1D area–velocity equation. If an acceleration to supersonic flow is required, a convergent-divergent nozzle is required. Otherwise: Conclusion: The Mach number is controlled by the expansion ratio formula_11 Subsonic and transonic wind tunnel Low-speed wind tunnels are used for operations at very low Mach number, with speeds in the test section up