Calculation Options Tab
The Calculation Options tab displays the calculation options as they were set for the previous calculation. Note that the fields are not editable from this tab. The tab contains the following information:
Calculation Option Attributes
| Attribute | Description |
|---|---|
| General | |
| Label | Lets you specify a name for the options option. |
| Notes | Lets you enter descriptive text to be associated with the current calculation option. |
| Time Analysis Type | Select whether the analysis is extended period or steady-state. |
| Calculation Type | Select whether to perform an analysis of the current model or to perform an automatic design calculation. This field is only available when the EPS Analysis Type is chosen. |
| Start Time | Select the clock time at which the simulation begins. This field is only available when the EPS Time Analysis Type is chosen. |
| Base Date | Select the calendar date on which the simulation begins. This field is only available when the EPS Time Analysis Type is chosen. |
| Duration | Lets you specify the duration of the simulation. This field is only available when the EPS Analysis Type is chosen. |
| Hydraulic Time Step | Lets you specify the computational time step in hydraulic calculations. This field is only available when the EPS Time Analysis Type is chosen. |
| Hydrologic Time Step | Lets you specify the computational time step in hydrology runoff calculations. This field is only available when the EPS Time Analysis Type is chosen. |
| Reporting Time Step | Output data will be presented at every reporting time step. This field is only available when the EPS Time Analysis Type is chosen. |
| Reporting Time Steps | Edit this collection to specify a custom definition for results ouput, including periods where you want all time steps saved (<All>), a constant reporting period (Constant), or no results at all (None). This field is only available when the Reporting Time Step value is set to Variable. |
| Tractive Stress (Global Minimum) |
Global value for minimum tractive stress in a conduit/channel to ensure self-cleaning. |
| Report Hydrologic Time Step? | If True, hydrographs will be reported in the hydrologic increment. |
| Convex Routing | |
| Peak Flow Ratio | Used when selecting a representative flow rate from the hydrograph to be routed when calculating the C parameter used to perform the routing calculations. |
| Gravity Hydraulics | |
| Maximum Network Transversals | This is the maximum number of iterations that will be performed to achieve the closest approximation of the desired network results. |
| Flow Convergence Test | This value is taken as the maximum relative change in discharge occurring at the system outfall between two successive network solutions. In rational hydrology, system discharge is a function of travel time and hydraulics through the system. Therefore, it is necessary to iterate until the system balances, or a maximum number of trials has occurred. |
| Flow Profile Method | Allows you to choose between a backwater and capacity analysis flow option method. |
| Number of Flow Profile Steps | The gradually varied flow option divides each pipe into internal segments prior to calculation of the hydraulic grade. The default value of option steps is five, and it is recommended that the value entered here be at least five for accuracy. Increasing this number will increase the accuracy of the hydraulic grade calculation, but will increase the calculation time. |
| Hydraulic Grade Convergence Test | The value entered here is taken as the maximum absolute change between two successive iterations of hydraulic grade at any junction or inlet in the system. For a given discharge, the upstream propagation of headlosses through pipes will continue until two successive calculations change by an absolute difference of less than this test value. The Hydraulic Grade Convergence Test value is used in the standard step gradually varied flow profiling algorithm. The calculations is assumed to converge to the solution when the two successive depth iterations are within this absolute test value. |
| Minimum Structure Headloss | This section allows you to specify a minimum structure headloss. If the system calculates a structure headloss that is lower then this value, the value specified in the Minimum Headloss field will be used. This option applies to all structure headloss methods except for the Absolute Method. Absolute headlosses will not be overridden, even if they are less then the value specified in this option. |
| Average Velocity Method | This section allows you to pick the method used to calculate the average travel time velocity. The following four options are available: Actual Uniform Flow Velocity Full Flow Velocity Simple Average Velocity Weighted Average Velocity |
| Structure Loss Mode | Choose either Hydraulic Grade or Energy Grade as the basis for the hydraulic calculations. |
| Save Detailed Headloss Data? | If True, the detailed headloss data will be saved after computation. If False, the detailed headloss data (the AASHTO results for manholes) used in the computations will not be saved, resulting in a smaller results file. |
| Gravity Pressure Interface Options | |
| Extreme Flow Setup | Select an Extreme Flow Setup for the current calculation. |
| Pattern Setup | Select the Pattern Setup for the current calculation. |
| Pressure Hydraulics | |
| Use Controls During Steady State? | When this box is checked, controls will be active during Steady State analyses. |
| Wet Well Increment | Unless a wet well is set to Fixed Level, this is the increment that is used to attempt to balance the wet well level such that the total flow out is greater than the total flow in. |
| Use Pumped Flows? | In a steady state run, in pressure subnetworks, the flow from the network is calculated using pressure equations, the characteristics of the system and number of pumps running. For that flow rate to be passed to the downstream gravity system, the user should set this property to "True". In some cases, the user will not want to use that flow but would rather pass a loading to the downstream system based on upstream loads and appropriate extreme flow factors similar to the way flows are handled in the gravity system. To pass those flows on to the downstream gravity system, the user sets this property to "False". In general, using pumped flows (True) is used when the user wants to look at the peak flows when the pumps are running, while using the loadings (False) gives more of a true picture as one moves far downstream from the pressure system and the effects of pump cycling become diminished. |
| Accuracy | Unitless number that defines the convergence criteria for the iterative solution of the network hydraulic equations. When the sum of the absolute flow changes between successive iterations in all links is divided by the sum of the absolute flows in all links, and is less than the Accuracy value, the solution is said to have converged. The default value is 0.001 and the minimum allowed value is 1.0e-5. |
| Trials | Unitless number that defines the maximum number of iterations to be performed for each hydraulic solution. |
| Use Linear Interpolation for Multipoint Pumps? | If set to true, the engine will use linear interpolation to interpret the pump curve as opposed to quadratic interpolation. |
| Steady State Loading | |
| Steady State Hydrograph Equivalent | Specify how the program should handle hydrographs during a steady state analysis. |
| Headloss Options (AASHTO) | |
| Bend Angle vs. Bend Loss Curve | Opens the Bend Angle vs Bend Loss Curve dialog, allowing you to modify the default curve. |
| Expansion, Ke | Adjustment coefficient used in AASHTO equation to account for expansion of the flow on the exit from incoming pipe. |
| Contraction, Kc | Adjustment coefficient used in the AASHTO equation to account for contraction of the flow on the entrance in the outfall pipe. |
| Shaping Adjustment, Cs | Adjustment coefficient used in the AASHTO equation for junction headloss calculation to account for partial diameter inlet shaping (equivalent to Half and Full in HEC-22). If inlet shaping is used then the headloss is decreased by this factor (50% default). |
| Non-Piped Flow Adjustment, Cn | If non-piped flow accounts for 10% or more of the total structure outflow, a correction factor is applied to the total loss. By default, this value is a 30% increase in headloss (a factor of 1.3) as documented in the AASHTO manual, but can be changed by the user. |
| Headloss Options (HEC-22) | |
| Elevations Considered Equal Within | The maximum elevation distance that pipes entering a node can be separated by and still be considered to be at the same elevation. |
| Consider Non-Piped Plunging Flow | If this value is set to True, plunging correction factor for non-piped flow will be applied during the calculation. |
| Flat Submerged | Benching correction coefficient used for a flat submerged transition structure. |
| Flat Unsubmerged | Benching correction coefficient used for a flat unsubmerged transition structure. |
| Depressed Submerged | Benching correction coefficient used for a depressed submerged transition structure. |
| Depressed Unsubmerged | Benching correction coefficient used for a depressed unsubmerged transition structure. |
| Half Bench Submerged | Benching correction coefficient used for a half bench submerged transition structure. |
| Half Bench Unsubmerged | Benching correction coefficient used for a half bench unsubmerged transition structure. |
| Full Bench Submerged | Benching correction coefficient used for a full bench submerged transition structure. |
| Full Bench Unsubmerged | Benching correction coefficient used for a full bench unsubmerged transition structure. |
| Headloss Options (Generic) | |
| Governing Upstream Pipe Selection Method | Select the method for selecting the upstream pipe when computing the headloss for a structure using the Generic Headloss Method. |
The list of calculation options can be sorted by either of two methods. You can switch between the two sorting methods by clicking the Categorized or Alphabetical buttons above the list pane.