| SI.Length | dimension | 4*crossArea/perimeter | Characteristic dimension (e.g., hydraulic diameter) |
| SI.Area | crossArea | pi*dimension*dimension/4 | Cross-sectional flow areas |
| SI.Length | perimeter | 4*crossArea/dimension | Wetted perimeters |
| SI.Length | length | 1.0 | Pipe length |
| SI.Height | roughness | 2.5e-5 | Average heights of surface asperities |
| SI.Area[nSurfaces] | surfaceArea | {2*pi*rs_outer[end]*length*nPins} | Area per transfer surface |
| SI.Angle | angle | 0.0 | Vertical angle from the horizontal (-pi/2 < x <= pi/2) |
| SI.Length | dheight | length*sin(angle) | Height(port_b) - Height(port_a) distributed by flow segment |
| SI.Length | height_a | 0 | Elevation at port_a: Reference value only. No impact on calculations. |
| SI.Length[nRegions] | rs_outer | {if i == 1 then 0.01 else rs_outer[i - 1] + 0.001 for i in 1:nRegions} | Outer radius of each region {r_outer[1],...,r_outer[n]} |