Burning Question

I was enjoying reading the alumni magazine last night, in bed, about to drift off to sleep, when I came upon the letter “Burning Question,” from Richard Daehler-Wilking ’73 [Letters, March 2012] about the fire in the SU in 1969.

He writes in part: “I stood next to a pumper talking to the fireman in attendance. He took the time to answer my questions, and I distinctly remember being told that with higher pressure (pounds per square inch), the rate of flow (gallons per minute) decreased. I did not know Bernoulli’s principle at the time, so his statement caught me by surprise. I’m sure I doubted it until I next encountered it when teaching physics many years later.”

Well, that woke me up, because as a landscape architect one of the things I do is design landscape irrigation—that’s water flowing through pipes. I think Richard should have kept doubting, because higher pressure does not cause lower flow. Here’s a concise description from Golf Engineering Associates Technical Help Series: “Higher pressure will cause greater flow through any given pipe size, but as the flow increases, the pressure will decrease downstream due to friction loss because water velocities increase as well.”

—David Widelock ’69

Oakland, California