# Reynolds number calculator

## laminar or turbulent flow

### Description

You can use the calculator for all fluids and flow rates without any restriction. The calculator applies to fluid mixtures also, but you have to enter the viscosity of a mixture.

With Reynolds number calculator you can analyze what makes fluid flow regime laminar and what is needed to force the fluid to flow in the turbulent regime.

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Action
Calculation setup
Flow rates and velocity
Reynolds number
Pipe dimensions
Fluid properties

# Exclusive calculator

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#### Description

q - volumetric flow rate
Fluid flow rate in terms of units of volume per unit of time
ṁ - mass flow rate
Fluid flow rate in terms of units of mass per unit of time
V - velocity
Flow velocity in terms of units of distance per unit of time
D - pipe diameter
Internal circular pipe diameter
H - channel height
The height of channel for rectangle shaped pipe
W - channel width
The width of channel for rectangle shape pipe
A - area
Internal pipe cross section area
ρ - fluid density
Mass per unit of volume
T - temperature
Fluid temperature for gas density calculation based on the ideal gas state equation
p - pressure
Fluid pressure at the start of the pipe for gas density calculation based on the ideal gas state equation
R - gas constant
Gas constant in terms of energy per unit of mass and temperature, for gas density calculation using ideal gas state equation
ν - kinematic viscosity
Result of fluid particles colliding to each other and moving at different velocities in terms of area per square unit of time
μ - dynamic viscosity
Result of fluid particles colliding to each other and moving at different velocities in terms of mass per square unit of distance and time
Re - Reynolds number
Dimensionless number representing viscous versus inertial forces ratio

#### Calculation setup

Select value to input. You should enter selected one. The other two will be calculated
q
volumetric flow rate
mass flow rate
V
flow velocity
Select value to input. You should enter selected one. The other one will be calculated. Available only if the gas is selected fluid
ρ
fluid density
T
temperature
Select value to input. You should enter selected one. The other one will be calculated
ν
kinematic viscosity
μ
dynamic viscosity
Select fluid type
liquid
for incompressible fluids
gas
for fluids where ideal gas state equation is used. Enables selection between density and temperature to input.
Select pipe shape
round pipe
full cross section fluid flow
rectangular duct
for rectangle channels and full cross section flow

#### When is this calculator suitable?

You can use the calculator for all fluids and flow rates without any restriction. The calculator applies to fluid mixtures also, but you have to enter the viscosity of a mixture.

#### Calculator description

Reynolds number named after Osborne Reynolds (1842 – 1912), gives the relation between inertial and viscous forces of fluid flow. If inertial forces (flow rate) are much bigger, and Reynolds number is higher than critical, Re > 2320, fluid flow is turbulent, and if viscous forces are big enough in comparison to inertial (flow rate), Reynolds number is lower than critical, Re < 2320, fluid flow is laminar.

For calculation of Reynolds number in closed pipe fluid flow average velocity, fluid viscosity, and internal pipe diameter should be known. Reynolds number is proportional to fluid flow average velocity and pipe diameter and inversely proportional to fluid viscosity.

With Reynolds number calculator you can analyze what makes fluid flow regime laminar and what is needed to force the fluid to flow in the turbulent regime. For example - in pipes with minimal internal diameter it is more likely to have laminar flow regime with small Reynolds number even for a fluid with low viscosity. In fluid flow with temperature change flow regime can change from turbulent to laminar flow regime, as viscosity is changing depending on the fluid temperature.

save/open multiple results
export to Word and Excel
print results
create list of custom fluid properties
resistance factor K for flow in valves and fittings
pipe surface roughness selection
pipe material selection
select between gauge and absolute pressure
compressible isothermal flow
dry air isothermal flow
gas offtake flow
natural gas flow

## Calculator start selection

Read all about available deployments. In any way of utilizing calculator, Internet connection is not required, but nice to have for authentication at least.