Hello everyone. I want to ask you by whose formula is calculated the hydraulic conductivity of round section sewage pipes depending on the filling of the pipe (h/D) in SewerGEMS. It could be by Thormann's , Manning's or someone elses. I'm attaching graph of averaged velocity of numerical results for circular and egg‐shaped cross‐sections with Manning (continuous line) and Thormann‐Franke (dashed line) formulas to let you know what i mean. Thank you.
I'm not exactly sure about your question, but if you are using one of the dynamic wave solvers in SewerGEMS (implicit or explicit), you are using the St. Venant Equations which were derived by Jean Claude Barre de St. Venant c1840. It calculates 1D flow in open channels. The equations cannot be solved analytically so solution usually involved a lot of simplifications such as steady, uniform flow. It wasn't until the coming of digital computers in the 1970's that the St. Venant equations could be used in engineering practice.
The 2D hydraulic elements charts you showed goes back at lest 100 years. I believe you can derive it from a 2D version of St. Venant using steady uniform flow but it has been empirically verified many times. The GVF-convex solver in SewerGEMS uses Manning's equation which does not calculate depth vs. velocity.