Pressure gradient the air to make it move as wind. Note that the pressure gradient force points from high towards low pressure zones, it is thus oriented in the opposite direction from the pressure gradient itself. Sound waves and shock waves are events that can induce very large pressure gradients, but these are often transitory disturbances. In acoustics the pressure gradient is proportional to the sound particle acceleration according to Euler's equation. Pressure gradient In atmospheric science (meteorology, climatology and related fields), the pressure gradient (typically of air, more generally of any fluid) is a physical quantity that describes in which direction
High-pressure steam locomotive sealed ultra-high-pressure circuit that simply transferred heat to a high-pressure circuit, by means of heating coils inside a high-pressure boiler. If this latter was fed with ordinary water, scale could form on the outside of the heating coils, but it could not cause overheating because the ultra-HP tubes were quite capable of withstanding their internal steam temperature, though not the firebox flame temperature. The sealed ultra-high-pressure circuit ran at between , depending on the rate of firing. The HP boiler worked at approx , and the low-pressure boiler at . The UHP and HP boilers were of a water tube