Auto Racing Articles: Air Flow Dynamics

Air Flow Dynamics, Reynolds Number
Article courtesy of http://RacingSecrets.com

The Reynolds number is the most important dimensionless number in fluid dynamics providing a criterion for dynamic similarity. It is named after Osbourne Reynolds. Typically it is given as follows:

Re = ρ * v * L / η or
Re = v * L / ν

With

v - fluid velocity
L - characteristic length
η - dynamic fluid viscosity
ν - kinematic fluid viscosity
ρ - fluid density

The Reynolds is used for determing wether a flow is laminar? or turbulent?. Laminar flow within e.g. pipes will occur when the Reynolds number is below the critical Reynolds number of Re_{crit, pipe}=2300 and turbulent flow when it is above 2300 where the Reynolds number is based on the pipe diameter and the mean velocity within the pipe. The value of 2300 has been determined experimentally and a certain range around this value is considered the transition region between laminar and turbulent flow. Please note, that the critical Reynolds number Re_crit depends on the flow type and the definition of the Reynolds number.

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This article courtesy of http://RacingSecrets.com , your racing technology resource.