Water Hammer Pressure Surge (Joukowsky)
Wave celerity from pipe-fluid coupling, pressure surge dP = rho × a × dV, and rapid-closure flag against 2L/a.
Example
You enter
- Pipe material copper
- Pipe size (Sch 40) 1
- Velocity at closure (fps) 8
- Closure time (s) 0.05
- Run length (ft) 100
- Fluid water
You get
- Wave celerity 4462 fps
- Surge ΔP 481 psi
- Reflection time 2L/a 44.8 ms
- Closure category slow closure (surge attenuated)
Details, formula, and sources
Joukowsky surge: a = sqrt(K/rho) / sqrt(1 + (K × D)/(E × t)); dP = rho × a × dV. Reflection time = 2L/a; rapid closure when t_close < 2L/a.
Joukowsky (1898) classical-fluids result by name; ASCE Manual of Practice 49 by name; manufacturer pipe-elastic-property values from data/plumbing/pipe-elastic-properties.json.
Joukowsky derivation free in published fluid-mechanics texts. ASCE MOP-49 licensed.
Estimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
Field names used by the API: material, pipe_size, velocity_fps, closure_time_s, run_length_ft, fluid, celerity_fps, surge_psi, reflection_time_s, rapid_closure
- Water bulk modulus K 2.19 GPa ≈ 317 800 psi at 60 °FNIST
- Water density rho 1.940 slug/ft³physical fact at 60 °F
- Schedule 40 D / t table data/plumbing/pipe-elastic-properties.json + SCH40_DIMS_INengineering reference