#INFOSEWER

Simulation Options in InfoSewer and H2OMap Sewer


Simulation Options

The Simulation Options dialog box is used to adjust some facet of a model prior to a model run. Simulation options are usually altered to be associated with a given scenario.

For example, suppose the user wishes to specify a peaking equation for one model run that differs from a second peaking equation. This can be accomplished through the Simulation Options where one option can be tied to one scenario while another option is specified for a different scenario.

To create a simulation option, from the Control Center click on the Operation Data tab and select Simulation Options. Click on the New button at the top of the Control Center dialog box and supply a unique name and description for the simulation option. When the OK button is chosen, the following dialog box will appear.

Click on any icon or tab below to learn more.

The General Tab

· Flow Unit – Units of flow measurement (cfs, gpm, mgd, imgd, afd, L/s, L/m, MLd, m3/h, and m3/d).

· Default Diurnal Pattern – Determines which diurnal pattern will be applied to an EPS simulation when a unique pattern has not been assigned to an individual manhole(s).

· Global Loading Multiplier – Used to assign a multiplier in which global loadings are to be multiplied. For example, a MAXDAY EPS model scenario may have a global loading multiplier of 2.5.

· Accuracy – Convergence criterion used to signal that a solution has been found to the nonlinear equations that govern network hydraulics. Trials end when the relative change in pipe flow rates between two successive iterations is less than this number. Suggested value is 0.001.

· Diurnal Pattern Usage – Select whether the pattern will linearly interpolate intermediate values (continuous) or evaluate patterns in a stepwise fashion. Click here to learn more about pattern representation options.

· Default Manhole Sealing Method – Use this to specify the default Manhole cover type for Normal Manholes. Choose Locked to contain flow inside the manhole structure when the water level rises above the rim elevation and choose Unlocked if flow is not contained inside the structure and spills over when the water level rises above the rim elevation. The maximum head possible in the second case is thus the manhole rim elevation

· Maximum number of segments – The maximum number of segments specifies the maximum number of segments a pipe can be divided into during a flow routing and quality analyses. The default value is 100 segments per pipe. The maximum number of segments affects the speed and accuracy of the hydraulic analysis. The smaller the value the faster the computational speed.

· Minimum Travel Distance – Minimum Travel Distance is the smallest length that a pipe segment could assume. Pipes shorter than this value will have only one segment. The default value is 100 ft.

· Minimum Travel Time – Minimum Travel Time establishes the smallest time of travel through a pipe recognized by H2OMAP Sewer. Travel times smaller than this number are set equal to it (travel times through pumps are instantaneous and are not affected by this limit). The default minimum travel time is 1 second.InfoSewerH2OMAP Sewer determines the travel time based on pipe and flow properties, and uses this computed time step for hydraulic calculations during an EPS. The user can assign a desired minimum travel time, and this value is used when calculated travel times are less than the minimum travel time. The maximum allowable value for the minimum travel time is equal to the smaller value of report time step and pattern time step. The minimum travel time affects the speed and accuracy of the water quality analysis (i.e. time of concentration and source tracing). The larger this value is the faster the computational speed.

· Pumped Flow Conservation – Check this option to set the gravity main flow downstream of a pump equal to the pump flow thereby forcing it to be an unpeakable load. If this option is not checked then the gravity main flow downstream of a pump is set equal to the flow entering the wet well. This option can be used only for steady-state analysis and design.

· Flow Attenuation – Check this option to include flow/hydrograph attenuation in the EPS simulation. If this option is not checked then flow attenuation will not be considered in the analysis. Flow attenuation in a sewer collection system is the process of reducing the peak flow rate by redistributing the same volume of flow over a longer period of time as a result of friction (resistance), internal storage and diffusion along the sewer pipes.InfoSewerH2OMAP Seweruses a distributed Muskingum-Cunge flow routing method based on diffusion analogy, which is capable of accurately predicting hydrograph attenuation or peak flow damping effects (peak subsidence). This option can only be used for extended period simulation.

· Unit Hydrograph Adjustment Threshold(%) – The option provides the flexibility whether to adjust ordinates of synthetic unit hydrograph such as Tri-triangular, NRCS Dimensionless, NRCS Triangular and CUHP. Theoretically, volume under a UH has to be drainage area * an inch of rainfall. That may not happen while synthesizing UHs. In case the difference in volume under the synthesized UH and the theoretical volume exceeds the threshold assigned by the user, the model will adjust the UH volume to “match” the theoretical volume.

· Advanced Forcemain Network Support – The checkbox for Advanced Forcemain Network Support allows the simulation of two or more upstream force mains to one or more downstream force main(s) through a junction chamber. The link flows and node depths are solved iteratively to maintain the mass balance and the energy balance of the incoming and outgoing flows. The new network solver is used to calculate the flows in the forcemain pipes and the heads at the junction chambers associated with the force main(s). See Advanced Force Main Network Solution for additional information.

· If the checkbox flag is turned on (checked) then the new Advanced Forcemain Network Support will be used during the simulation.

· If the checkbox flag is turned off (unchecked) then the default force main solution will be used. You will get an error message if there is more than one force main connected to the same junction chamber.

In the example shown below, the upstream force mains are links 947 and FM51, the merging junction chamber is node 52 and the downstream force main is link 53. As you can see in the graph from the Output Report Manager the flow in link 53 is the sum of the flows in links 947 and FM51. This example will only work with the new Advanced Forcemain Network Support feature.

The Peaking Tab

InfoSewerH2OMAP Sewer provides two variations for analyzing and peaking sewer flows. The first method is to peak the base flow while the second method consists of peaking a coverage flow that is based on population. Steady state simulation flows will be peaked depending on which peaking type is specified for the manhole loading. See the Attribute Browser to learn more.

For Peakable Base Flow

· Peaking Factor K – The K value used in a steady state base flow peaking equation.

· Peaking Factor p – The p (rho) value used in a steady state base flow peaking equation.

· Alternative Peaking Curve – The Peaking Curve method is an alternative method to compute flow data (loads) for peak conditions. Any peaking curve can be specified to estimate base flow peaks and model peak flow – base flow relationships. The peaking curve represents the peak flows (Y-axis) as a function of base flows (X-axis). Click here to learn more about setting up a curve

For Peakable Coverage Flow

· Peaking Parameter a – The a value used in a steady state coverage flow peaking equation.

· Peaking Parameter b – The b value used in a steady state coverage flow peaking equation.

· Peaking Parameter c – The c value used in a steady state coverage flow peaking equation.

· Peaking Parameter d – The d value used in a steady state coverage flow peaking equation.

· Peaking parameter e -The e value used in the coverage flow peaking equation indicated below.

· Alternative Peaking Curve – The Peaking Curve method is an alternative method to compute flow (loads) for peak conditions. For peakable coverage flows, the peaking curve represents the peaking multiplier (Y-axis) as a function of Population number or coverage (X-axis).

The Design Tab

· New System – designs a new sewer collection system (i.e., determines size and slope of pipes) given manhole locations, sewer loads, ground elevation at manholes, and various design criteria including capacity (i.e., depth to diameter ratio), velocity, cover depth, and slope.

· Existing System – conducts capacity analysis on an existing system and designs, either a replacement pipe or a duplication pipe, for conduits that fail to meet one or more design criteria including depth to diameter ratio and velocity.

· Velocity Constraints – Sewer pipes are designed to maintain a velocity within the minimum velocity and the maximum velocity values specified here. The minimum velocity should be assigned from the perspective of avoiding sedimentation problems whereas the maximum velocity should be set in such a way that erosion of pipe materials is avoided. It should be noted that the velocities defined here are applied to all pipes in the system for which maximum and minimum velocities are not defined individually. The velocities should be given in ft/sec for US customary units and in meters/sec for SI units. The default values are 10ft/sec (3m/sec) for maximum velocity, and 2 ft/sec (0.6 m/sec) for minimum velocity.

o Maximum Velocity – The global maximum velocity criteria to be used during a steady state design simulation. Maximum velocity criteria can also be assigned to an individual pipe through the pipe constraints button under the Attribute Browser.

o Minimum Velocity – The global minimum velocity criteria to be used during a steady state design simulation. Minimum velocity criteria can also be assigned to an individual pipe through the pipe constraints button under the Attribute Browser.

· Cover Constraints – These constraints limit the depth, measured from the ground elevation, at which the sewer pipes are laid. These values should be defined considering local conditions such as anticipated loading from traffic and buildings, and to prevent freezing in cold regions. Like velocity constraints, the limiting cover depth values assigned here are applied to all pipes in the system for which cover constraints are not assigned. The units are feet and meters for US customary and SI systems, respectively. The default values are 20 ft (6 m) and 3ft (1m) for maximum cover depth and minimum cover depth, respectively.

o Maximum Cover – The global maximum cover criteria to be used during a steady state design simulation. Maximum cover criteria can also be assigned to an individual pipe through the pipe constraints button under the Attribute Browser.

o Minimum Cover – The global minimum cover criteria to be used during a steady state design simulation. Minimum cover criteria can also be assigned to an individual pipe through the pipe constraints button under the Attribute Browser.

· Max. Crown Drop at Manholes – Under normal design condition, crown elevation of a pipe leaving a manhole is set to the minimum crown elevation of pipe(s) entering the manhole. However, pipe velocity resulting from a pipe aligned according to crown elevation matching may exceed the maximum velocity defined for the pipe. In such cases, a drop manhole is used to lower crown elevation of the pipe, thus the pipe slope and the flow velocity. Lowering pipe elevation also leads to lowering invert elevation of the manhole. As the difference in invert elevation of the incoming pipe(s) and invert elevation of the manhole widens, flow falling from the incoming pipes to the manhole may erode the manhole. Maximum crown drop at manhole refers to the maximum allowed difference in crown elevations of the upstream pipe(s) and the downstream pipe to avoid formation of large water falls and subsequent erosion of manhole materials. However, damage cased by water falls coming from small pipes may not be significant. Therefore, it may not be necessary to limit crown drop for small pipes. The Cutoff Diam. refers to pipe diameter beyond (inclusive) which the maximum crown drop constraint has to be considered. Units used for max. crown drop at manhole and cutoff diameter are ft and inch in US customary, and, meter and mm in SI systems. The default values are 3ft and 24 inch for crown drop at manhole and cutoff diameter, respectively, in US customary units, and 1 m and 600 mm for crown drop at manhole and cutoff diameter, respectively, in SI units.

· Manhole Invert Offset – refers to the required offset between the minimum invert elevation of the incoming and the outgoing pipe and invert elevation of the manhole. Units are inch and mm in US customary and SI systems, respectively. The default value is zero.

· Design Manning Coefficient – Refers to Manning’s n for the new sewer pipe. The pipe Manning coefficient that is to be applied to parallel and replacement pipes during a steady state design simulation. The default value is 0.001.

· Default D vs. Min Slope Design Curve: The minimum slope allowed for various conduit sizes is supplied to the model using this curve. X-axis values are pipe diameters and Y-axis values are minimum slope. The curve defined here will be applied to all pipes in the collection system for which D vs. Min Slope Design Curve is not locally defined. A default curve is available for both US customary units and SI units.

· Default D vs. d/D Analysis Criteria Curve – The curve used when evaluating pipes during a steady state analysis. When d/D values for specific diameters exceed these values, the pipe is deemed deficient and a parallel and replacement pipe are recommended in a steady state design simulation.

· Default D vs. d/D Design Curve: Defines maximum allowed carrying capacity for a pipe in terms of depth to diameter ratio for various pipe sizes. X-axis values are pipe diameters and Y-axis values are depth to diameter ratio values.

· Include Existing Pipe in Parallel Design – If this option is checked, then the existing pipe d/D ratio constraint must be satisfied when a new parallel pipe size is determined. This option is only used for steady-state design.

· Design Only Coded Inverts (Invert <= -9999) – This option is provided to allow fixing invert elevation of a newly designed pipe to predefined value, if needed. If this option is checked, pipes that are assigned invert elevation greater than -9999 will have their invert elevations fixed at those values. New invert elevation would be designed only for pipes whose existing invert elevation is less than or equal to -9999.

· Default Pipe Replacement Cost Cu Irve: Used to define pipe cost per unit length of a pipe (i.e., per unit feet for US Customary, and per unit meter for SI units). X-axis values are pipe diameters and Y-axis values are cost per linear length of a pipe. The cost could include pipe cost and many other cost types. Click here to learn more.

· Include Excavation/Reinstatement Cost: Some cost types such as excavation cost and reinstatement cost may be readily defined in terms of unit volumes, not unit length. For such cases, the design model estimates incurred costs based on average cover depth for the pipe, trench width computed based on pipe diameter, and pipe length. This cost provision option is provided to offer the flexibility for modelers who wish to define cost in terms of unit volume, or, for those who want to specify some cost types in unit lengths using the replacement cost curve option previously described, and other cost types in terms of unit volume of a pipe using this option.

· To activate this cost provision option, click on the “Define Cost” button and complete input data on the initiated dialog editor.

· Default Parallel Pipe Cost Curve – The default diameter vs. cost curve that is used for deficient pipes where a parallel pipe is recommended. Click here to learn more.

For information on the report generated by this analysis, click here.

The Quality Tab

 

InfoSewerH20Map Sewer provides seven options for sewage quality analysis in conjunction with a hydraulic simulation. These options are available only for EPS runs, and may be chosen on the Quality panel from the Simulation Options dialog box given above. Please click here for details on how to use the quality module of InfoSewerH20Map Sewer.

The Storm Tab

InfoSewerH20Map Sewer provides comprehensive stormwater modeling capability. This feature is only available for InfoSewerH20Map Sewer. Click here to learn more about the storm tab.

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