A blow down facility is a testing facility that relies on charging an energy reservoir (often a tank of pressurized gas) and releasing the energy over a relatively short time to produce test conditions at higher energy release rates than can be maintained continuously. Impulse facilities

Impulse facility

A testing facility that relies on rapid release of stored energy to generate a short period of high enthalpy test conditions for testing of aerodynamic flow, aerodynamic heating and atmospheric reentry, combustion, chemical kinetics, ballistics, and other effects...

 are a special case of blow down facilities that release their energy very rapidly to create very high enthalpy

Enthalpy

Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...

 conditions over very short test times. Contrasting with blow down facilities are continuous facilities

Continuous facility

A continuous facility is a type of testing facility that produces test conditions that can be maintained indefinitely, such as certain types of wind tunnels. In contrast to continuous facilities are blow down facilities that operate only in short bursts at conditions that cannot be maintained...

 that can operate at a certain conditions continuously, such as some types of wind tunnel

Wind tunnel

A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...

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