Don’t under predict your water hammer forces.  There are several cautions that should be applied when using the Joukowsky equation as a first approximation of fluid transient pressures.

At the 2018 Pressure vessel and Piping conference in Prauge, Czech Republic Trey W. Walters P.E. of Applied Flow Technology and Robert A. Leishear, Ph.D., P.E. of Leishear Engineering, LLC presented a paper on When the Joukowsky Equation Does Not Predict Maximum Water Hammer Pressures.

Read the paper here: When the Joukowsky equation does not predict maximum water hammer pressures

In the paper, caution is provided for separate phenomenon which can increase pressures greater than those predicted by the Joukowsky equation.  These conditions include reflected waves at tees, changes in piping diameter, and changes in pipe wall material, as well as frictional effects referred to as line pack, and the effects due to the collapse of vapor pockets.

Using AFT Impulse, we predict these phenomenon and avoid non-conservative estimations of water hammer pressure surges.

Questions? gmontgomery@ecedesign.com or leave a comment below.