2D Parameters Dialog (InfoWorks)

Depth

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

Momentum

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

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

Ignore rain falling on dry elements

If this option is checked, rainfall and evaporation applied to the 2D mesh will only be applied to 'wet' elements in the mesh.

Default value: unchecked

If this option is checked, the level of bank sections that are lower than adjoining mesh elements will be adjusted by the engine to match the mesh element ground level.

Note that it is possible during mesh generation to adjust the ground level of mesh elements to match the adjoining bank level.

Default value: checked

If this option is checked, the 2D simulation engine will perform calculations at every minor timestep.

If this option is unchecked, 2D calculations will be performed at every run timestep.

Using this option may help in reducing the occurrence of oscillations at banks for some networks.

Default value: unchecked

Timestep Stability Control

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

Maximum Velocity

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

Theta

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

Inundation mapping depth threshold

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

Multiplier to be applied to the run timestep when calculating damage results (flood duration) at Damage Receptors.

Default value: 1

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

See See Initial State Interpolation for details.

Default value: 100

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

See See Initial State Interpolation for details.

Default value: 2

When this option is checked, the 2D engine checks if a local steady state has been reached in each element of the 2D zone. Elements in the 2D zone are put in 'sleep mode' whenever a steady state is reached. The threshold criteria to determine whether an element has reached a steady state is specified in the fields below.

The area becomes active again when any of the threshold criteria specified are exceeded.

This functionality has the potential to speed up simulations, particularly in 2D river applications in cases where 2D zones are large with different flooded areas acting independently.

Default value: unchecked

The time in seconds that an element need to fulfil threshold criteria to be considered in steady state.

Default value: 60 mins

Depth threshold criteria.

Hourly rate of change of depth must not exceed this threshold over Time lag period for element to be considered in steady state.

Default value: 0.001 m

Velocity threshold criteria.

Hourly rate of change of velocity must not exceed this threshold over Time lag period for element to be considered in steady state.

Default value: 0.001 m/s

Water quality threshold criteria.

Hourly rate of change of criteria must not exceed thresholds specified over Time lag period for element to be considered in steady state.

Default value: 0.000

Displayed for on-premise runs

Options for using a graphics card to perform 2D calculations:

• If suitable card is available - Default setting for all new runs.

  Use a GPU card for 2D calculations if a suitable card is available, and the requested 2D options are supported (see Unsupported 2D options below), otherwise default to CPU. A message will be displayed in the log to indicate if suitable GPU card has not been found.

• Never - Do not attempt to use GPU card for 2D calculations. The simulation will be processed using a CPU card. If any of the requested 2D options are not supported (see Unsupported 2D options below) on a CPU card, the simulation will fail.
• Always - Always attempt to use GPU card for 2D calculations. An error will occur if a suitable GPU card is not found or if the requested 2D options are not supported (see Unsupported 2D options below).

Displayed for cloud runs

Options for using a GPU instance to perform 2D calculations:

• If optimal for selected network (recommended) - Default setting for all new runs.

  The software determines if a simulation is suitable to run on a GPU instance, and that the requested 2D options are supported (see Unsupported 2D options below).

  If suitable, a 2D simulation is submitted to a GPU instance, otherwise it will be submitted to a CPU instance. A message is displayed in the simulation log if a 2D simulation fails to run on a GPU instance.

• Never - Never use a GPU instance for 2D simulations. A 2D simulation is submitted to a CPU instance. If any of the requested 2D options are not supported (see Unsupported 2D options below) on a CPU instance, the simulation will fail.
• Always - Always use a GPU instance for 2D simulations. A message is displayed in the simulation log if a 2D simulation fails to run on a GPU instance, or if the requested 2D options are not supported (see Unsupported 2D options below).