Cableizer ®

Diameter (inner) tunnel

For shapes such as squares or rectangular ducts and tunnels where the height and width are comparable, the characteristic dimension for internal-flow situations is taken to be the hydraulic diameter, defined as $D=4*A/P$, where A is the cross-sectional area, and P is the wetted perimeter. The wetted perimeter for a tunnel is the total perimeter of all inner tunnel walls that are in contact with the flow.

For circular tunnels, the diameter is an input value.

Symbol
$Di_{t}$
Unit
m
Formulas
$\frac{4A_{t}}{2w_{t}+2h_{t}}$
Related
$A_{t}$
Cross-sectional area (inner) tunnel [m$^2$]
$h_{t}$
Height (inner) [m]
$w_{t}$
Width (inner) [m]
Used in
$A_{t}$
Cross-sectional area (inner) tunnel [m$^2$]
$d_{t}$
Channel covering [m]
$Do_{t}$
Diameter (outer) tunnel [m]
$h_{t}$
Height (inner) [m]
$\mathrm{Re}_{air}$
Reynolds number air
$T_{tw}$
Thermal resistance wall [K.m/W]