Objects and Methods

Pipeline

This object models fully-pressurized flow through a pipeline.

General Slots

Inflow

Type: SeriesSlot

Units: FLOW

Description: Flow rate at the entrance of the object.

I/O: Can be input, output, or set by propagation across a link

Links: Usually linked to the outflow slot on another object.

Outflow

Type: Series Slot

Units: FLOW

Description: Flow rate at the exit of the object.

I/O: Can be input, output, or set by propagation across a link

Links: Usually linked to the inflow on another object.

User Methods

Pipeline Solution Direction

This method category is used to specify the direction the Pipeline solves (downstream given inflow or upstream given outflow). For basic Simulation runs this does not make a difference and the default method should remain selected. However, in Rulebased Simulation the user may need to limit the Pipeline to downstream solution only.

Solve Upstream or Downstream

This is the default method and should remain selected for basic Simulation. There are no slots or calculations specifically associated with this method. It simply allows all dispatch methods to be active.

Solve Downstream Only

This method may need to be selected in Rulebased Simulations where the Pipeline can solve in the downstream direction only. When this method is selected, only the solveOutflowGivenInflow dispatch method is active.

Head Loss

The user selectable methods for Head Loss include None and Hazen-Williams Equation. None is the default method and makes no other calculations. Hazen-Williams Equation will calculate Inflow Head given Outflow Head or Outflow Head given Inflow Head. The selected method executes from the dispatch method.

None

This is the default method and makes no calculations.

Hazen-Williams Equation

This method calculates Inflow Head given Outflow Head (and other inputs) or Outflow Head given Inflow Head (and other inputs). These inputs include pipe diameter, pipe length, the C Value of the Pipeline, and minor losses within the Pipeline.

In this method, either Inflow Head or Outflow Head must be given (either set as an input, by rules, or set through a link) in order to calculate the other. If Inflow Head is input or set through a link, Outflow Head is calculated. If Outflow Head is input or set through a link, Inflow Head is calculated.

The following slots will be instantiated when using the Hazen-Williams Equation method.

Slots Specific to This Method

Inflow Head

Type: SeriesSlot

Units: Length

Description: Inflow Head of the Pipeline object. This is equal to the total head, which includes pressure, elevation, and velocity components. This value likely comes from a link or is calculated.

I/O: Input or Output

Links: Usually linked to the head slot on another object

Outflow Head

Type: SeriesSlot

Units: Length

Description: Outflow Head of the Pipeline object. This is equal to the total head, which includes pressure, elevation, and velocity components. This value likely comes from a link or is calculated.

I/O: Input or Output

Type: Usually linked to the head slot on another object

Diameter

Type: ScalarSlot

Units: Length

Description: Diameter of the Pipeline. It is assumed constant over its length. It must be greater than zero.

I/O: Input only

Links: not linkable

Velocity

Type: SeriesSlot

Units: Velocity

Description: Velocity of the water within the Pipeline.

I/O: Output only

Links: not linkable

Length

Type: ScalarSlot

Units: Length

Description: Length of the Pipeline. The length must be greater than or equal to zero.

I/O: Input only

Links: not linkable

C Value

Type: ScalarSlot

Units: NoUnits

Description: Hazen-Williams C Value of the Pipeline. The C Value depends on the pipe material, pipe age, tuberculation, lining, etc.... Values can be found in a hydraulics text and vary between 80-150.

I/O: Input only

Links: not linkable

Minor Losses

Type: ScalarSlot

Units: Length

Description: Minor Losses at the Pipeline. The value defaults to zero if less than zero or not input.

I/O: Input only

Links: not linkable

The head loss will be calculated using the Hazen-Williams formula, as follows:

Rh is the hydraulic radius. For a circular pipe:

V is the velocity of the water within the pipeline, as follows:

C is the user input Hazen-Williams C Value of the pipe, as follows:

S is the slope of the energy grade line, as follows:

Note: The empirically-derived Hazen-Williams formula is unit-specific. Published in literature, k for British units is 1.318 and 0.85 for SI units. In RiverWare, the formula uses S.I. units, in which head loss has units of meters, Length has units of meters, Velocity has units of meters/second, the C Value has no units, and Diameter has units of meters. Unfortunately, k =1.318 for British and k = 0.85 for SI are not equivalent when converted. As a result, RiverWare will use the more common and more significant value of k = 1.318. In SI units, this is equivalent to 0.8492.

Rearranging the Hazen-Williams formula, head loss can be solved as follows:

Depending on inputs, Outflow Head or Inflow Head is set to one of the following:

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Dispatch Methods

This object solves for inflow or outflow, whenever the other is known. If the Solve Upstream or Downstream method is selected, then all dispatch methods are active. However, if Solve Downstream Only is selected, then only the solveOutflowGivenInflow method is active.

solveOutflowGivenInflow

Solves for outflow.

Required Knowns

• Inflow

Required Unknowns

• Outflow

If an inflow head is linked, the dispatch method will wait for a value in this slot before solving. The equation for this dispatch method is as follows:

solveInflowGivenOutflow

Solves for Inflow.

Required Knowns

• Outflow

Required Unknowns

• Inflow

If an outflow head is linked, the dispatch method will wait for a value in this slot before solving. The equation for this dispatch method is as follows:

Revised: 06/03/2019