# Hydraulic diameter

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===Estimating the turbulent length-scale=== | ===Estimating the turbulent length-scale=== | ||

- | For fully-developed flow in non-circular ducts the [[turbulent length | + | For fully-developed flow in non-circular ducts the [[turbulent length scale]] can be estimated as <math>0.07 \, d_h</math>. This is as usefull estimation for setting [[turbulence boundary conditions]] for inlets that have fully developed flow. |

===Computing Reynolds number=== | ===Computing Reynolds number=== |

## Latest revision as of 09:58, 17 December 2008

The hydraulic diameter, , is commonly used when dealing with non-circular pipes, holes or ducts.

The definition of the hydraulic diamater is:

## Contents |

## Use of hydraulic diameter

### Estimating the turbulent length-scale

For fully-developed flow in non-circular ducts the turbulent length scale can be estimated as . This is as usefull estimation for setting turbulence boundary conditions for inlets that have fully developed flow.

### Computing Reynolds number

The hydraulic diamater is often used when computing the dimensionless Reynolds number for non-circular ducts.

## Hydraulic diameters for different duct-geometries

Using the definition above the hydraulic diamater can easily be computed for any type of duct-geometry. Below follows a few examples.

### Circular pipe

For a circular pipe or hole the hydraulic diamater is:

Where d is the real diameter of the pipe. Hence, for circular pipes the hydraulic diameter is the same as the real diameter of the pipe.

### Rectangular tube

For a rectangular tube or hole with the width and the height the hydraulic diamter is:

### Coaxial circular tube

For a coaxial circular tube with an inner diameter and an outer diameter the hydraulic diameter is: