Fluid Numbers
Subject
A fluid number is actually a ratio, usually named after its creator, of the fluid's inertia to a specified property; i.e. temperature, pressure, viscosity, gravity, velocity, elasticity, etc. enabling the prediction of one property based upon the known magnitude of another.
This ratio (Inertia ÷ Property) can be used, for example, to predict the behaviour of a fullsize body submerged in a fluid based upon the performance of a model, or to calculate its performance across a range of conditions without the need to build a model, e.g. added mass and drag coefficients, which are based upon Reynold’s number.
Calculator
The fluid numbers calculator includes a calculation option for each number, see Options below. You enter as much information as you know, and as soon as it can Fluid Numbers will calculate the unknown(s).
The technical help page for Fluid Numbers takes you through a stepbystep procedure showing you how to use this calculator to relate the performance of a fullsize submarine to that of a model.
For help using this calculator see Technical Help
Fluid Numbers Calculator  Options
All calculation options in this calculator work in the same way. The input and output values are the same. You enter the data you know and Fluid Numbers will fill in the missing value. In other words; you enter: the known values, and Fluid Numbers will calculate: the unknown value
REYNOLDS
Reynolds number is used to predict the behaviour of a fluid based upon viscosity.
You enter: 
and the fluid numbers calculator will provide: 


FROUDE
Froude’s number is used to predict the behaviour of a fluid based upon gravity.
You enter: 
and the fluid numbers calculator will provide: 


EULER
Euler’s number is used to predict the behaviour of a fluid based upon pressure.
You enter: 
and the fluid numbers calculator will provide: 


PRESSURE COEFFICIENT
The pressure coefficient number is used to predict the behaviour of a fluid based upon pressure difference.
You enter: 
and the fluid numbers calculator will provide: 


VELOCITY
The velocity number is used to predict the behaviour of a fluid based upon (rotational) velocity.
You enter: 
and the fluid numbers calculator will provide: 


CAUCHY
Cauchy’s number is used to predict the behaviour of a fluid based upon elasticity.
You enter: 
and the fluid numbers calculator will provide: 


MACH
The Mach number is used to predict the behaviour of a fluid based upon elasticity.
You enter: 
and the fluid numbers calculator will provide: 


STROUHAL
Strouhal’s number is used to predict the behaviour of a fluid based upon vibration frequency.
You enter: 
and the fluid numbers calculator will provide: 


WEBER
Weber’s number is used to predict the behaviour of a fluid based upon surface tension.
You enter: 
and the fluid numbers calculator will provide: 


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