Hydraulic solver features
An option that changes a pipe's geometry also changes what the water can do inside it. Hydraulic solver features can affect conveyance, storage, flow, or depth, so each requires explicit selection in addition to the default solver baseline.
True-ellipse hydraulics
| Property | Behavior |
|---|---|
| Default | EPA_LEGACY |
| Opt-in value | TRUE_ELLIPSE |
| Input declaration | CUSTOM_ELLIPSE_MODEL TRUE_ELLIPSE in [OPTIONS] |
| Scope | Custom HORIZ_ELLIPSE and VERT_ELLIPSE sections with positive rise and span |
| Unchanged | Standard catalog ellipse sections |
| Report marker | Custom Ellipse Hydraulics TRUE ELLIPSE (NON-EPA) |
The custom ellipse has two dimensions. It is reasonable to expect both to take
part in the calculation. The EPA-compatible default uses released
custom-ellipse formulas and partial-flow tables. TRUE_ELLIPSE derives full
and partial area, width, wetted
perimeter, hydraulic radius, and section factor from one mathematical ellipse.
Because those quantities feed routing, enabling the feature can change conduit
capacity, depth, velocity, and flow-regime transitions.
Read True-ellipse hydraulics for the motivation, equations, comparison with EPA behavior, selection APIs, modeling implications, and verification evidence.
Return to the solver feature overview.