CE-211 · Compressibility & Water Hammer

🔧 Water-Hammer Valve

Stop the moving water column by closing the valve — but do it gently. Slam it shut and the water's kinetic energy compresses against the closed valve, sending a pressure surge (water hammer) racing back up the pipe. Close fast enough to score, slow enough that the surge stays below the pipe's burst rating.

Pipe length L: 600 m Flow speed V₀: 2.5 m/s

Or hold SPACE. Release to pause closing.

Valve closed 0% Surge Δp 0 kPa Burst limit 0 kPa Time 0.0 s Score —

The physics behind the game

wave speed a = √(K/ρ) • rapid closure: Δp = ρ·a·V₀ (Joukowsky) • slow closure (t_c > 2L/a): Δp ≈ ρ·L·V₀ / t_c

The pressure-wave speed a comes straight from the bulk modulus K of water (~2.06×10⁹ Pa), giving a ≈ 1435 m/s. If you close the valve faster than the pipe period 2L/a, you get the full Joukowsky surge; close it more slowly and the surge falls off as 1/t_c. That's exactly why real pipelines use slow-closing valves, surge tanks and air vessels. Values are illustrative teaching approximations.