Downbursts and the Moody Diagram
Downbursts and the Moody Diagram
Downbursts (which can be further classified as microbursts or macrobursts depending on their size) are violent meteorological phenomena that are commonly produced by derechos. In severity, they are very comparable to tornadoes, although they receive far less attention. Opposed to tornadoes, which produce rotational winds, downbursts funnel air downward until the air reaches the ground, at which point it spreads out in all directions, creating very strong straight-line winds. The nature of a downburst is very similar to that of a fluid traveling through a vertical pipe, and consequently, the Moody diagram (with a different scope), along with the Darcy–Weisbach equation for head loss through pipes, can be used to calculate the velocity of the winds created by the downburst. Using the diameter of the funnel and some given quantities, the friction factor of the "pipe" can be determined using an alteration of the Moody diagram, which can then be used in the Darcy–Weisbach equation with a known head loss (calculated with the height of the storm) to solve for the velocity of the winds.