# Darcy friction factor - Blasius correlation with correction for curved or helically coiled tubes

## Description

In fluid dynamics, the Darcy friction factor formulae are equations that allow the calculation of the Darcy friction factor, a dimensionless quantity used in the Darcy–Weisbach equation, for the description of friction losses in pipe flow as well as open-channel flow.

The Darcy friction factor is also known as the Darcy–Weisbach friction factor, resistance coefficient or simply friction factor; by definition it is four times larger than the Fanning friction factor.

Early approximations for smooth pipes by Paul Richard Heinrich Blasius in terms of the Moody friction factor are given in one article of 1913.

Mishra and Gupta in 1979 proposed a correction for curved or helically coiled tubes, taking into account the equivalent curve radius (Rc).

This Correlation is valid for:

Re_tr < Re < 10^5

6.7 < 2Rc/D < 346.0

0 < H/D < 25.4

The equivalent curve radius (Rc) in the shown formula can be calculated from the formula in:

**See Also:**

## Variables

f | Darcy friction factor (dimensionless) |

Re | Reynolds number (dimensionless) |

D | Pipe's inside diameter (m) |

R_{c} | Equivalent curve radius (m) |