Stokes Terminal Velocity Calculator
Estimates creeping-flow settling speed for a small sphere. Changing an entry refreshes both the value and its checking path.
Enter the system data
Terminal velocity
From sample inputs to terminal velocity
The starting example uses Particle radius = 0.0005 m; Particle density = 2500 kg/m³; Fluid density = 1000 kg/m³; Gravitational acceleration = 9.80665 m/s²; Dynamic viscosity = 0.001 Pa·s. Entering those values provides a baseline before testing a different physical condition.
After calculating, rearrange vt = 2r²(ρp-ρf)g / 9μ for one supplied quantity and see whether it returns the original entry. This reverse check is especially helpful when powers, ratios, or reference values are present.
Build the calculation from units
Begin with vt = 2r²(ρp-ρf)g / 9μ and identify the sought quantity before substituting. The sample entries give a concrete calculation that can be repeated by hand.
An explicit symbolic step for stokes terminal velocity helps separate geometry, material properties, and operating values before they combine numerically.
Connecting geometry and material behavior
Estimates creeping-flow settling speed for a small sphere. The inputs describe particle radius, particle density, fluid density, gravitational acceleration, dynamic viscosity, and the reported unit is m/s.
Stokes' law requires a low particle Reynolds number and enough distance from walls and neighboring particles.
On the stokes terminal velocity page, each number stays beside its physical unit. That pairing matters because a converted value placed in an unconverted field can look plausible while changing the model.
What Stokes Terminal Velocity does not include
The stated viscosity and flow quantities must describe the same temperature and flow regime. Transition, turbulence, entrance effects, or nearby walls can invalidate the simplified path to terminal velocity.
Changing the geometry, material state, or boundary condition may require a new equation before recalculating terminal velocity.
An independent route back to the inputs
Reduce the units in vt = 2r²(ρp-ρf)g / 9μ; the surviving dimension must agree with m/s. If it does not, the arithmetic should not be accepted even when the displayed number is finite.
Then vary one measured input by ten percent and predict whether terminal velocity should rise, fall, or remain unchanged. That sensitivity test is independent of merely repeating the same keystrokes.
Carrying terminal velocity into later work
Keep the full calculated terminal velocity for downstream arithmetic, alongside the original measurements. Round only the value presented as the final stokes terminal velocity result.
Record the formula, units, geometry, and material state with terminal velocity. A bare number cannot reveal whether density, pressure reference, flow area, or operating condition was interpreted correctly.
Another useful step from Stokes Terminal Velocity
Related work can continue with laminar pipe pressure drop calculator, fluid drag force calculator, poiseuille flow rate calculator and drag coefficient calculator.
Before following a link, confirm that its idealizations agree with the Stokes Terminal Velocity model.
What to know about Stokes Terminal Velocity
What does the terminal velocity represent?
It is the output of vt = 2r²(ρp-ρf)g / 9μ for the field definitions and units printed on the stokes terminal velocity page.
How can I check the terminal velocity?
Rearrange vt = 2r²(ρp-ρf)g / 9μ to recover one input, and independently confirm that the remaining dimension reduces to m/s.
Must all entries use the displayed units?
Yes. Convert every measurement to the unit beside its field before applying the stokes terminal velocity relationship.
Why could another terminal velocity differ?
A different material state, geometry, reference condition, rounding rule, or model assumption can change the reported terminal velocity.
Can the terminal velocity be negative?
On the stokes terminal velocity page, a negative result is meaningful only when vt = 2r²(ρp-ρf)g / 9μ and its printed sign convention permit it; otherwise it signals an inconsistent physical domain.
How many digits should be retained?
Keep guard digits while terminal velocity feeds another operation, then round to a precision supported by the least certain source measurement.