2D Parameters Dialog (SWMM)

Depth threshold used to determine whether to consider a mesh element wet or dry.

Mesh elements with depth of water below this value will be considered dry and a zero depth will be displayed in the results.

Only mass conservation will be considered in elements with depth below this threshold.

Typical value: 0.001 m

Default value: 0.001 m

Depth threshold used to determine whether to consider momentum in a mesh element or not.

Movement of water will not be calculated for mesh elements with depth of water below this value; only mass conservation will be taken into account.

Typical value: 0.001-0.01 m

Default value: 0.001 m

Velocity threshold.

Mesh elements with water velocity below this value will have velocity reset to zero in terms of momentum calculations.

Typical value: 0 m/s

Default value: 0 m/s

This parameter ensures that the internal timestep used by the 2D engine is within the stability bounds given by the CFL condition (Courant Friedrichs Lewy condition).

Valid values: 0 < TSC < 1

Typical value: 0.95

Velocity threshold limiting the velocities that can be achieved in an element in a 2D simulation.

Mesh elements with water velocity above this value will have velocity reset to the maximum specified.

Typical value: 10 m/s

Weighting factor, θ, for the semi-implicit parameter. Weights the explicit and semi-implicit parts of the numerical scheme used for the time integration of the flow equations.

The higher the value, the more weight given to the implicit part.

Valid values: 0 < θ ≤ 1

Typical value: 0.9

Depth threshold used to determine Time to first inundation for mesh elements.

Time to first inundation is reported as the time (from the start of the simulation) at which water depth in the mesh element first exceeds this threshold.

Default value 0.01m

Used when calculating initial state values for 2D mesh elements from an Initial State Simulation.

Default value: 100

Used when calculating initial state values for 2D mesh elements from an Initial State Simulation.

Default value: 2

Options for using graphics card for carrying out 2D calculations:

• Never - do not attempt to use GPU card for 2D calculations
• If suitable card is available - use GPU card for 2D calculations if suitable card available, otherwise default to CPU (a message will be displayed in the log to indicate if suitable GPU card has not been found)
• Always - always attempt to use GPU card for 2D calculations. An error will occur if a suitable GPU card is not found.