Jet Propulsion

Calculate jet propulsion velocity, flow volume, and thrust force using fluid dynamics equations. Applicable to incompressible flows such as liquids (water) but not gases (air).

Jet Propulsion Calculator

Key Equations

Jet Velocity: v₂ = √(2(p₁ - p₂)/ρ)

Volume Flow: q = A × v₂

Propulsive Force (stationary jet): F = 2A(p₁ - p₂)

Inputs

Calculator

Inputs

Pressure Before Jet (p₁) (Pa)

Ambient Pressure After Jet (p₂) (Pa)

Fluid Density (ρ) (kg/m³)

Orifice Area (A) (m²)

Results

Jet Velocity (v₂)-- m/s

Volume Flow (q)-- m³/s

Propulsive Force (F)-- N

Parameter	Symbol	Value	Unit	Description
Pressure Before Jet	p₁	Input	Pa	Absolute pressure upstream of the jet outlet
Ambient Pressure	p₂	Input	Pa	Atmospheric pressure after the jet
Fluid Density	ρ	Input	kg/m³	Density of incompressible fluid (e.g., water)
Orifice Area	A	Input	m²	Cross-sectional area of jet outlet
Jet Velocity	v₂	Calculated	m/s	Exit velocity from the jet
Volume Flow Rate	q	Calculated	m³/s	Volume of fluid flowing per unit time
Propulsive Force	F	Calculated	N	Thrust force generated by stationary jet

Notes

Valid for incompressible flows only (liquids like water)
For a stationary jet: v₁ = 0
Equations assume constant fluid density
Not applicable for compressible flows (gases like air)

Example

For a garden hose with 15 mm diameter:

Orifice Area: A = π(0.0075)² = 1.77 × 10⁻⁴ m²
Pressure before: p₁ = 4 × 10⁵ Pa
Atmospheric pressure: p₂ = 1 × 10⁵ Pa
Propulsive Force: F = 2 × 1.77 × 10⁻⁴ × (4 × 10⁵ - 1 × 10⁵) = 106 N