xpdrainage 2017.1 Help Documentation XDH2017v1

PeakThe Pipe Sizing Criteria is the set of parameters required to size pipes/channels along a given network.

Note: Pipe Sizing is performed using Path which has been previously set up.




Peak Flow Calculation

Select the calculation method to be used when sizing the pipes/channels. Choose from:

Rational Method: Flow = Rainfall Intensity x Total Area + Total Base Flow

(UK) Modified Rational Method: Flow = Rainfall Intensity x Total Area * Cr(1.3) + Total Base Flow

Methode de Caquot: Flow is calculated via the Methode de Caquot equations which are considerably more involved that the Rational Method or (UK) Modified Rational Method equations. The method's inputs are the Caquot (Base and Advanced) parameters, selected Desbordes rainfall parameters and the Runoff Path Length and Catchment Slope of the Inflows upstream of the pipes belonging to the auto-sized Flow Path. Further information can be found on the Methode de Caquot page.

Rainfall Source

When Rational Method or (UK) Modified Rational Method is selected from the Peak Flow Calculation list box the Rainfall Source list box lists the currently configured IDF curves and FEH, FSR, ARR and Desbordes rainfalls in the Rainfall Manager. When autosizing pipes / channels the rainfall intensity will be retrieved from the selected rainfall source based upon the Travel Time for the pipe/channel.

When Methode de Caquot is selected from the Peak Flow Calculation list box the Rainfall Source list box lists only the Desbordes rainfalls configured in the Rainfall Manager.

In either case the parameters of the selected Rainfall Source are displayed below the Rainfall Source list box. In addition, if the Methode de Caquot is selected from the Peak Flow Calculation list box the Caquot Base Parameters and Use Shape Correction checkbox are displayed below the parameters of the selected Rainfall Source. To the right of the Base Parameters is a calculation button. Clicking on this displays a separate form which allows the user to modify the Advanced Caquot parameters which in turn recalculates the Base Caquot parameters shown on the Pipe Sizing Criteria form.

Pipes Size Library

The pipe size library is a sequential list of pipe diameters. New pipe libraries can be defined by clicking on the button next to the box.

Minimum Time of Concentration

This is the minimum time that should be applied to each pipes time of concentration. This is in effect applied to the head of each branch line to give an initial time of entry for the inflows.

Maximum Travel Time

This allows the maximum travel time down the system to be capped at the given value. This prevents the Intensity being used to size the pipe/channel reducing to low.

Design Level

Choose Level Soffits (Crowns) or Level Inverts from the list box to design the system with Level Soffits (Crowns) or Level Inverts respectively.

Note: Level Soffits only applies to Pipes as Channel soffits are already aligned to the cover level.

Minimum Cover Depth

The desired depth from the pipe soffit/channel top to the cover level. When ground levels have already been input the program will warn the user when the desired cover to ground level has not been achieved.

When the option is turned on the auto size calculation will attempt to redesign the system and achieve the above cover where it is feasible.

Note: Level Soffits only applies to Pipes as Channel soffits are already aligned to the cover level.

Minimum Slope

The desired minimum slope for a pipe/channel.This is desirable when the ground is flat or is sloping away from the pipes and minimum slopes are required to reduce excavation.  

When the option is turned on the auto size calculation will attempt to redesign the system and achieve the minimum slope where it is feasible.

Minimum Velocity

The desired minimum velocity for a pipe/channel. The program will then choose a pipe diameter and slope with sufficient capacity to give the required Full Bore Velocity.

When the option is turned on the auto size calculation will attempt to redesign the system and achieve the minimum slope where it is feasible.

Note:  Pipe sizes are increased in steps and it may not be possible to achieve exactly the minimum velocity.

 


Workflow - What's next...?

Connect Inflows to your Stormwater Control, specify Inlets or Outlets or connect to another Stormwater Control or Junction.

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