- 05 Aug 2022
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# 1D river simulations - additional outputs tab

- Updated on 05 Aug 2022
- 8 Minutes to read

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In this tab, additional outputs and system volume output details are specified.

A 1D river simulation will, by default, always save a standard set of six variables. These are:

Flow

Stage

Froude number

Velocity

Unit mode

Unit state

Pollutant concentrations will be added to this list for a 1D quality simulation.

Some of these default variables will have no meaning for certain units within a model, e.g. velocity in a reservoir.However, there may be additional variables, not on the default list, that are relevant to particular units and of importance to the modeller. To address this issue, an additional results file can be produced by 1D simulations.

#### Additional outputs

Prior to running a simulation a user can select any variable from a list of additional outputs. These will be saved to the supplementary results file, which has the extension .zzx. It should be noted that multiple selections from the list are permissible.

Data will be saved to the .zzx file from all units relevant to the selected variables. When the simulation is complete these data will then be available to be output as comma separated variable format files using Tabular CSV in the same way as the default data.

### Available Variables

The following sections provide definitions of the additional variables that can be saved from an 1D simulation to a zzx file. Any data that is not applicable to the node in question will be given the default null data value of -9999.99.

Variable | Description | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Maximum Stage During Save Interval | This variable is output for all 1D model units. At any time within a simulation this represents the maximum stage that has occurred during the previous save interval. | ||||||||||||

Maximum Flow During Save Interval | This variable is output for all 1D model units. At any time within a simulation this represents the maximum flow that has occurred during the previous save interval. | ||||||||||||

Mean Stage During Save Interval | This variable is output for all 1D model units. At any time within a simulation this is the mean stage over all timesteps within the preceding save interval. | ||||||||||||

Mean Flow During Save Interval | This variable is output for all 1D model units. At any time within a simulation this is the mean flow over all timesteps within the preceding save interval. | ||||||||||||

Conveyance | The conveyance variable applies only to a river section or conduit unit. An array of depths and corresponding conveyance values is calculated for each river section at the beginning of a simulation. During a simulation the conveyance is then calculated by linear interpolation of this relationship at the current depth. | ||||||||||||

dh Convergence | dh convergence is output for all units. It is a measure of the convergence in calculated stage for a selected unit within the model and therefore represents how well the simulation is performing at the selected unit (see Convergence Information). | ||||||||||||

dQ Convergence | dQ convergence is output for all units. It is a measure of the convergence in calculated flows for a selected unit within the model and therefore represents how well the simulation is performing at the selected unit (see Convergence Information). | ||||||||||||

Reservoir / River Volume | Unit volume can be calculated for either a river section or a reservoir unit. For a river section the volume is calculated as the product of average cross-sectional area (of upstream and downstream cross sections) and reach length, and applies to the volume between the node in question and the next node downstream. For a reservoir the volume is calculated by the summing the product of average segment area and segment depth from the user-specified area/elevation relationship over the reservoir depth. This option may be used as an alternative to the "Output approximate system volume" option. | ||||||||||||

Operating rule number | This option applies to structures operating in logical rule mode only. Its value denotes the rule number being applied at the given time. | ||||||||||||

Slot Area | Slot area applies only to a river section unit. A triangular slot can be added to the base of a river section by using the Automated Preissmann Slot option. This aids model stability during periods of low flow. The slot area variable represents the wetted cross-sectional area of the slot. This will be the cross-sectional area of the entire slot when water levels are above the slot height. | ||||||||||||

Slot Volume | Slot volume applies only to a river section unit. A triangular slot can be added to the base of a river section by using the Automated Preissmann Slot option. This aids model stability during periods of low flow. The slot volume variable represents the volume of water contained within the slot. When water levels are above the slot height this will be: Slot cross-sectional area x Reach length For lower water levels the average slot cross sectional area, between upstream and downstream sections is used in the equation. | ||||||||||||

Structure Velocity | Structure velocity is the average flow velocity through or over a hydraulic structure. It is calculated as: Total flow through structure / Total cross-sectional flow area This variable applies to variety of structures and for each structure there are a number of different flow scenarios that affect the calculation of cross-sectional area across the unit. These are shown in the table below:
| ||||||||||||

Surface Area | The surface area variable applies to both river section and reservoir units. The reservoir surface area is calculated by linear interpolation of the user entered depth / surface area relationship. The river surface area applies to the area between the node in question and the next node downstream is calculated as: ((Upstream flow width + Downstream flow width) / 2) x Reach length | ||||||||||||

Wetted Area | The wetted area represents the cross-sectional area and applies only to a river section or conduit unit. | ||||||||||||

Wetted Perimeter | The wetted perimeter is an available output from the river section or conduit unit only. An array of depths and corresponding wetted perimeters is calculated for each river section at the beginning of a simulation. During a simulation the wetted perimeter is then calculated by linear interpolation of this relationship at the current depth. | ||||||||||||

2D Flow | The flow (in cubic meters per second) output between two adjacent river nodes is assigned to the upstream of the two (i.e. the earlier in the data file). A positive value indicates that the direction of flow is into the 1D domain | ||||||||||||

Pump Data | When selecting the Pump Data option, two variables are output to the supplementary results file: ‘Pump power’ and ‘Pump efficiency’. The pump efficiency is calculated during the initial derivation of the four-quadrant pump curve using Suter’s method. Pump power, P is defined as the torque (Nm) multiplied by the angular velocity (rad s Note: the angular velocity is the pump speed (rpm) multiplied by 2π/60. The relationship between efficiency and torque is as follows: Efficiency = ρ g Q h / (T ω) = ρ g Q h /P where ρ is the density, g is acceleration due to gravity, Q is the flow and h is the total head (the difference between the discharge head and the suction head). Note: when the pump is not operating (i.e. Stopped or Off), the pump power will be output as zero. | ||||||||||||

Stream Power per Unit Width | This is calculated as Density of water x acceleration due to gravity x current discharge x bed slope in the "downhill direction" / the current top width This is given in units of kg s^(-3) | ||||||||||||

Stream Power | This is calculated as Density of water x acceleration due to gravity x current discharge x bed slope in the "downhill direction" This is given in units of kg m s^(-3) | ||||||||||||

Average Shear Stress | This is calculated as Density of water x acceleration due to gravity x current wetted area x bed slope in the "downhill direction" / current top width This is given in units of kg m^(-1) s^(-2) |

Hint: The structure of the .zzx file is identical to the results file produced by an Flood Modeller Quality simulation (*.zzc). By changing the extension of a zzx file to '.zzc' (taking care not to overwrite any results from a Quality simulation), the user may view the results graphically from the user interface.

#### System volume

Output approximate system volume - Outputs the approximate storage volumes in channels, reservoirs, and cumulative inflows and outflows to a comma separated (CSV ) file (extension .ivl ).

Volume output interval - The interval (in seconds) at which approximate system volumes are written to the *.ivl file (if the previous option is selected). If left at zero, output will be written for the first and last timesteps . The default value is zero.