1D Pumps

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Introduction

This post provides a modelling example for a 1D pump using a fixed flow rate and pump curve. For this example we will model a pump in two common situations (2D-2D & 1D-2D).

Pump Attributes

A pump needs to first be digitised in a 1d_nwke layer. The direction of the polyline must go from inlet to outlet as a pump is unidirectional (? Is that true). The attributes required for a pump in your 1d_nwke layer can be found within the 2015 TUFLOW manual.
In the 1d_nwk layer, the following attributes are required:

1. ID = ID of the channel
   
2. Type = "P"
   
3. Len_or_ANA = Nominal length in m (only used for calculating nodal storage if UCS is on)
   
4. US_Invert = Upstream invert level of the channel
   
5. DS_Invert = Downstream invert level of the channel
   
6. Inlet_Type = Used to specify the pump curve in the Depth Discharge database.
   

2D-2D Configuration

Because pumps are zero length channels they do not create automatic nodes at the upstream and downstream end. If you ran the model with just a pump polyline you will get ERROR 1353 - No NA data for Node.To remove this error you will need to digitise a node within a separate 1d nwke layer and give a nominal storage amount in the “Len_or_NA” attribute for the 1d nwke ‘Node’, see the example below.
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To connect the pump to the 2d domain you will also need to digitise an SX connection. In the figure below I have showed both the 1d node and 2d SX points as being separate from each other for illustrative purposes only – they should both be snapped to the end of the pump polyline. SX connections are required at connections to 2D domains to transfer water from the 1D node to the 2D. Without the SX connection, water will build up within the node and cause an instability.
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1D-2D Configuration

Connecting a pump from a 1d network to the 2d domain or vice versa is similar to the configuration above, the only difference is that the connection with a 1d structure does not require a 2d SX connection or 1d nwke ‘Node’. A storage chamber in the 1d network can also be modelled using a 1d_na node with an elevation vs area .csv assigned to the node.
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Estry Control File Setup

Within the *.ecf the following commands and files are at a minimum required to run a pump with no logically control:

Read GIS Network ==..\model\mi\1d_nwke_xxxxx.MIF
Depth Discharge Database ==..\bc_dbase\xxxxx.csv

If you do not specify a Depth-Discharge database then you will be faced with ERROR 1118 – Could not find a y-Q curve.

TUFLOW Operating Control File (.TOC)

Rohan - Fill me out

Depth Discharge Database

The depth discharge database is set up in the same way as a pit inlet database, see 4.5.1.2 in the TUFLOW manual (Amend this section link once the manual is finalised).. Each pump ‘Inlet_type’ must reference a name within the depth discharge database, otherwise ERROR 1118 - Could not find pit inlet type ",a," in the pit inlet database will appear because TUFLOW will use the ‘ID’ field instead of the blank ‘Inlet_type’ field to search the database and it will come up with no information (that seemed to be the case during my testing). The ‘Area (m2)’ column is the area of the pump offtake and ‘Width (m)’ column is the width of the pump offtake (? Is that true). Without information in the Area(m2) or Width(m) columns in the depth discharge database Error 1092 and Error 1093 will appear.

Constant Flow Rate

For constant flow rate pumps, the figure below is an example with a 15 L/s pump with a 50mm offtake. The Name details displayed in cell A2 is what should be referenced in the “Inlet_Type” attribute.

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If you are using the 2013 build of TUFLOW you will need to specify a 1d nwke type of “PO” as well as a .toc file. (this was a bug I found where the 2013 build would stop with an unknown error if you only specified a type “P”)

Pump Curve

The performance of pumps is a function of suction head at the inlet and the level of the discharge location. The resultant total head between the water level at the inlet and outlet is what determines the flow rate through the pump. If the suction level is low the pump will need to provide more energy in the form of pressure to maintain the water elevation at the outlet, the opposite is also true if the water depth at the pump inlet is high.

That being the case it is important that you consider what total head is required to achieve the modeling objectives and what flow rates you may require. Once you have an idea on any limits in total head you can start to research an appropriate pump and then extract the performance curve that is often incorporated as part of the technical specifications. An example is shown below.

Creating a TUFLOW pump curve

The use of pump curves within TUFLOW requires a 2015 or later build due to a previous bug within the 2013 build. The setup of the Depth Discharge database for a pump curve is similar to reading in inflow hydrographs, hyetographs etc, that is; a source .csv, and the two corresponding headings within the 3rd and 4th column.

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Once you have your manufacturer curve for your given pump it is now necessary to create the curve .csv for TUFLOW to read in. The manufacturer specifications will need to be translated into a total head vs pump rate chart, an example is shown below.

Although reading in the depth discharge database is the same process as other boundary conditions within TUFLOW, the curve itself is fundamentally different as you no longer need to start the csv file with 0,0.

1D Check File

Although strictly not a check file, the operation of the pump can be confirmed by opening the *_1d_O.csv which is found within the csv folder where the results are written.

Filename prefix / suffix	Brief Description
_1d_O.csv	This csv displays the status of the pump, whether that is closed or fully open, results for any logic parameter specified in the TOC file and the flow through the pump if it is in operation.

Any further questions please email TUFLOW support: support@tuflow.com