Water-hammer screening calculator

Joukowsky instantaneous velocity-change pressure; wave speed supplied.

fluids-water-hammer.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	surgeMPa
	1
	0.8

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

surge budget1.00 MPa✓ passes

BASELINE INPUTS

density1000 kg/m^3waveSpeed1000 m/svelocityChange1 m/s

CALCULATED

surge1 MPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Water-hammer screening
# Scope: Joukowsky instantaneous velocity-change pressure; wave speed supplied.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

density = 1000 kg/m^3
waveSpeed = 1000 m/s
velocityChange = 1 m/s

surge := density*waveSpeed*velocityChange [MPa]

check surge budget: surge <= 1.5 MPa

scenario alternative: density = 800 kg/m^3

Calculated from your source · not saved

Baseline · Baseline

surge budget1.00 MPa ✓ passes

alternative · alternative

surge budget0.80 MPa ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

surge: surge = density*waveSpeed*velocityChange [MPa]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

density: 1000 kg/m^3
wave speed: 1000 m/s
velocity change: 1 m/s

Calculated

surge: 1 MPa

Assumptions and limits

Joukowsky instantaneous velocity-change pressure; wave speed supplied.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Water-hammer screening. Inputs: velocity change; density; wave speed; closure time. Outputs: pressure-surge screening. Model scope: Single-phase flow unless explicitly configured otherwise. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: velocity change, density, wave speed, closure time
Outputs: pressure-surge screening
Modes: calculate, compare, sweep
Drawing: Flow network and pressure plot

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS