Option — ConduitNET Help

Hydraulics Pptions determine how the hydraulic behavior of the pipe network should be analyzed. They include:

Options

Description

Flow Units

Units in which nodal demands and link flow rates are expressed. Choosing liters or cubic meters causes all other units to be SI metric, otherwise US customary units apply. Use caution when changing flow units as it might affect all other data supplied to the project.

Headloss Formula

Formula used to compute head loss as a function of flow rate in a pipe. Choices are:

Hazen-Williams
Darcy-Weisbach
Chezy-Manning

Because each formula measures pipe roughness differently, switching formulas might require that all pipe roughness coefficients be updated.

Specific Gravity

Ratio of the density of the fluid being modeled to that of water at 4 deg. C (unitless).

Relative Viscosity

Kinematic viscosity of the fluid being modeled relative to the viscosity of water at 20 deg. C (1.0 centistokes or 0.94 sq ft/day).

Maximum Trials

Maximum number of trials used to solve the nonlinear equations that govern network hydraulics at a given point in time.A suggested value is 40 or higher.

Accuracy

Convergence criterion used to signal that a solution has been found to the nonlinear equations that govern network hydraulics. Trials end when the sum of all flow changes divided by the sum of all link flows is less than this number. The suggested value is 0.001.

If Unbalanced

Action to take if a hydraulic solution is not found within the maximum number of trials. Choices are STOP to stop the simulation at this point or CONTINUE to use another 10 trials, with no link status changes allowed, in an attempt to achieve convergence.

Default Pattern

ID label of a time pattern to be applied to demands at those junctions where no time pattern is specified. If no such time pattern exists then demands will not vary at these locations.

Demand Multiplier

Multiplier applied to all baseline demands to make total system consumption vary up or down by a fixed amount. E.g., 2.0 doubles all demands, 0.5 halves them, and 1.0 leaves them as is.

Emitter Exponent

Power to which pressure is raised when computing the flow through an emitter device. The textbook value for nozzles and sprinklers is 0.5. This may not apply to pipe leakage.

Status Report

Amount of status information to report after a simulation is made. Choices are

NONE (no status report)
YES (normal status reporting - lists all changes in link status throughout the simulation and if water quality is analyzed, a final mass balance accounting)
FULL (full reporting - normal reporting plus the convergence error from each trial of the hydraulic analysis made in each time period) Full status reporting is only useful for debugging purposes.

CHECKFREQ

This sets the number of solution trials that pass during hydraulic balancing before the status of pumps, check valves, flow control valves and pipes connected to tanks are once again updated. The default value is 2, meaning that status checks are made every other trial. A value equal to the maximum number of trials would mean that status checks are made only after a system has converged. (Whenever a status change occurs the trials must continue since the current solution may not be balanced.) The frequency of status checks on pressure reducing and pressure sustaining valves (PRVs and PSVs) is determined by the DAMPLIMIT option (see below).

MAXCHECK

This is the number of solution trials after which periodic status checks on pumps, check valves flow control valves and pipes connected to tanks are discontinued. Instead, a status check is made only after convergence is achieved. The default value is 10, meaning that after 10 trials, instead of checking status every CHECKFREQ trials, status is checked only at convergence.

DAMPLIMIT

This is the accuracy value at which solution damping and status checks on PRVs and PSVs should begin. Damping limits all flow changes to 60% of what they would otherwise be as future trials unfold. The default is 0 which indicates that no damping should be used and that status checks on control valves are made at every iteration. Damping might be needed on networks that have trouble converging, in which case a limit of 0.01 is suggested.

Below are some typical values that might be used for the status checking parameters:

CHECKFREQ	MAXCHECK	DAMPLIMIT	Remarks
2	10	0	Frequent status checking; tends to produce solutions in the least number of iterations.
10	100	0.01	Less frequent status checking; might be needed for networks that have difficulty in converging.
Max. Trials	Max. Trials	Convergence Accuracy	Status checks made only after convergence is achieved; might produce convergence when other settings fail.

Quality Options select the type of water quality analysis to conduct and control how the calculations are carried out. They include the following:

Parameter
Parameter	Type of water quality parameter being modeled. Choices include: None (no quality analysis), Chemical (compute chemical concentration), Age (compute water age), Trace (trace flow from a specific node). In lieu of Chemical, you can enter the actual name of the chemical being modeled (e.g., Chlorine).
Mass Units	Mass units used to express concentration. Choices are mg/L or ug/L. Units for Age and Trace analyses are fixed at hours and percent, respectively
Relative Diffusivity	Molecular diffusivity of the chemical being modeled relative to that of chlorine at 20 deg. C (0.00112 sq ft/day). Use 2 if the chemical diffuses twice as fast as chlorine, 0.5 if half as fast, etc. Only used when modeling mass transfer for pipe wall reactions. Set to zero to ignore mass transfer effects
Trace Node	ID label of the node whose flow is being traced. Applies only to source tracing
Quality Tolerance	Smallest change in quality that will cause a new parcel of water to be created in a pipe. A typical setting might be 0.01 for chemicals measured in mg/L as well as water age and source tracing.

Note: The Quality Tolerance determines when the quality of one parcel of water is essentially the same as another parcel. For chemical analysis this might be the detection limit of the procedure used to measure the chemical, adjusted by a suitable factor of safety. Using too large a value for this tolerance might affect simulation accuracy. Using too small a value will affect computational efficiency.

Reaction Options select the type of water quality reactions that are included in the analysis.

Options	Description
Bulk Reaction Order	Power to which concentration is raised when computing a bulk flow reaction rate. Use 1 for first-order reactions, 2 for second-order reactions, etc. Use any negative number for Michaelis-Menton kinetics. See Bulk Flow Reaction Rates.
Wall Reaction Order	Power to which concentration is raised when computing a pipe wall reaction rate. Choices are FIRST (1) for first-order reactions or ZERO (0) for constant rate reactions. See Pipe Wall Reaction Rates.
Global Bulk Coefficient	Default bulk reaction rate coefficient (Kb) assigned to all pipes. This global coefficient can be overridden by editing this property for specific pipes. Use positive number for growth, negative number for decay, or 0 if no bulk reaction occurs. Units are concentration raised to the (1-n) power divided by days, where n is the reaction order.
Global Wall Coefficient	Wall reaction rate coefficient (Kw) assigned to all pipes. Can be overridden by editing this property for specific pipes. Use positive number for growth, negative number for decay, or 0 if no wall reaction occurs. Units are ft/day (US) or m/day (SI) for first-order reactions and mass/sq ft/day (US) or mass/sq m/day (SI) for zero-order reactions.
Limiting Concentration	Maximum concentration that a substance can grow to or minimum value it can decay to. Bulk reaction rates will be proportional to the difference between the current concentration and this value. Leave blank if not applicable.
Wall Coefficient Correlation	Factor correlating wall reaction coefficient to pipe roughness. See Wall Reaction - Pipe Roughness Correlation for more details. Leave blank if not applicable.

Times Options set values for the various time steps used in an extended period simulation. (Times can be entered as decimal hours or in hours:minutes notation).

Options	Description
Total Duration	Total length of a simulation. Use 0 to run a single period (snapshot) hydraulic analysis.
Hydraulic Time Step	Time interval between recomputation of system hydraulics. Normal default is 1 hour.
Quality Time Step	Time interval between routing of water quality constituent. Normal default is 5 minutes (0:05 hours).
Pattern Time Step	Time interval used with all time patterns. Normal default is 1 hour.
Pattern Start Time	Hours into all time patterns at which the simulation begins (e.g., a value of 2 means that the simulation begins with all time patterns starting at their second hour). Normal default is 0.
Reporting Time Step	Time interval between times at which computed results are reported. Normal default is 1 hour.
Report Start Time	Hours into simulation at which computed results begin to be reported. Normal default is 0.
Starting Time of Day	Clock time (e.g., 7:30 am, 10:00 pm) at which simulation begins. Default is 12:00 am (midnight).
Statistic	Type of statistical processing used to summarize the results of an extended period simulation. Choices are: NONE (results reported at each reporting time step) AVERAGE (time-averaged results reported) MINIMUM (minimum value results reported) MAXIMUM (maximum value results reported) RANGE (difference between maximum and minimum results reported) Statistical processing is applied to all node and link results obtained between the Report Start Time and the Total Duration. Note: To run a single-period hydraulic analysis (also called a snapshot analysis) enter 0 for Total Duration. In this case entries for all of the other time options, with the exception of Starting Time of Day, are not used. Water quality analyses always require that a non-zero Total Duration be specified.

Energy Options provide default values used to compute pumping energy and cost when no specific energy parameters are assigned to a given pump. They include:

Options	Description
Pump Efficiency	Default pump efficiency (as a percent).
Energy Price	Price of energy per kilowatt-hour. Monetary units are not explicitly represented.
Price Pattern	ID label of a time pattern used to represent variations in energy price with time.
Demand Charge	Additional energy charge per maximum kilowatt usage.