Irregular airway profile with non-rock obstruction

[Customer]

How do I define an airway that has a large longitudinally regular non-rock obstruction, such as a conveyor?  For example, an airway with circular profile (diameter 5m, perimeter pi*5 = 15.71m) with friction factor f = 0.012, carrying a conveyor of cross-sectional area 6.3m^2 (net perimeter (tunnel + conveyor) of 22m).

[Martin Griffith]

There are a number of ways to configure such an airway for air simulations, the clearest one being to enter an irregular shape profile, with the net area and net perimeter. However, it may be better to retain the original unobstructed perimeter of 15.71 m to be used in rock heat transfer calculations for heat simulations.

To achieve the correct resistance for the air simulations, but have the unobstructed perimeter used for heat, set an irregular shape profile. Then enter in for Perimeter, the unobstructed perimeter (15.71 m) and for Area, the net area (0.25 x p x*5^2  - 6.3 = 13.3 m^2). This will underestimate the resistance, since we are using the wrong perimeter; but since resistance is proportional to both perimeter and friction factor, we can adjust the friction factor to give the right resistance. In this case by a factor of net perimeter/unobstructed perimeter = 22/15.71. So we would replace the friction factor with f = 0.012 x 22/15.71 = 0.0168 kg/m^3. This will give the correct air resistance as well as calculate the correct rock surface area for heat calculations.