Establishment and application of hydraulic model

Abstract: The establishment, verification standard and thinking of hydraulic model in water supply network were introduced. Taking water supply network of new construction area in Tianjin Binhai HT Zone as an example, the hydraulic model was built, the operational condition of network in different hydraulic operational condition was simulated, it had guiding significance of water supply network optimization operations.

Key words: water supply network ; hydraulic model ; optimization operation; water supply project

Chinese library classification number: TV13document id code: Aarticle number:

The hydraulic model in water supply network was a hydraulic constraint, which guide water distribution system optimization operations. The establishment of hydraulic model in water supply network could improve its credibility and practicality. After having established hydraulic model，We perform hydraulic calculate through inputting dynamic date and static date, and the operation condition of the whole network could be realized in time. It have laid the foundation for realtime management, water quality stimulation and optimization operation network.

1 The elements of influencing model precision

The following are the reasons that responsible for the deviations between calculated value and actual measured value of hydraulic model in network。

① The accuracy of essential/basic date

② The imperfect of simplification/abbreviation in network plot

③ The influence of pump curves

④ The influence of node flow

⑤ The uncertainty of the pipe resistance coefficient

⑥ The uncertainty of the operating conditions

⑦ The measurement error caused by measurement equipment

2 Calibration of Water distribution network model

2.1 Calibration standard

WRC calibration standard[1] conclude five parts, so they are flow monitoring point, pressure monitoring point, boundary, water supply trends, and pressure distribution.

Combined with the actual situation of water supply network in China, the recommended calibration standards of model can be stated as follows[2]:

①Deviations between 100% pressure monitoring point and calculations were distributed between -4m and +4 m. Deviations between 80% pressure monitoring point and calculations were distributed between -2m and +2 m. Deviations between 50% pressure monitoring point and calculations were distributed between -1m and +1 m.

②Deviation for pipes that supply above 1% of the total water supply is among (-5%,+5%), Deviation for pipes that supply above 0.5% of the total water supply is among (-10%,+10%) .

③The calculated water pressure distribution of each node fits the measured one perfectly, low water pressure zone fits the measured one perfectly, and each water supply pressure fits the measured one perfectly.

2.2 Thinking of Calibration

The calibration of microscopic model is a process for complement model, adjustment parameter and hydraulic calculation repeating in this water distribution network.

The thinking of Calibration as follows:

Comparison between calculated and measured value of pressure at amonitoring point, to find out the reasons for the difference, completed and eliminated or minimized the difference value, until there is a permitting between calculated and measured value of model.

3 Maintenance of model

After having established the hydraulic model, it is essential to maintenance the model, because the actual water networks are changed often, especially for the big water distribution network.

The maintenance of model can be stated as the following:

① Changing network topology；

② Changing source of water；

③ Changing large user location；

④ Changing water demand model；

⑤ Changing water network operation condition.

4 Examples of engineering application.

Taking water supply network of new construction area in TianJin Binhai HT Zone as an example, the hydraulic model was built, and the different operational condition of network was simulated according to the principle.

4.1 Introduction of hydraulic models

Fig.1 shows the network topology of hydraulic model in GX Zone, including 202 nodes and 409 pipes. The maximum and minimum pipe diameter were DN800 and DN300.

Fig.1 Hydraulic model of water supply network in GX zone of Tianjin Binhai

4.2 Calibration of hydraulic models

The model was calibrated in actual water supply situation through temporary monitor point. Pressure monitoring points 1 and 2 were located at the northern entrance and central network. Flow monitoring points were located at the northern and southern entrance. Calibrated results: Deviations between whole pressure monitoring point and calculations were distributed between -2m and +2m. Deviations between 50% of pressure monitoring point and calculations were distributed between -1m and +1m. Deviation between 100% of flow monitoring point and calculations was less than 10%, and deviation between 50% of flow monitoring point and calculations was less than 8%.

As we can see from fig.2 to fig.5, comparison between calculated value and measured value were conducted in Pressure monitoring point and Flow monitoring point. Through these steps, hydraulic model was built preliminarily.

Fig.2 Calculated and measured value of Pressure monitoring point One

Fig.3 Calculated and measured value of Pressure monitoring point Two

Fig.4 Calculated and measured value of Flow monitoring point One

Fig.5 Calculated and measured value of Flow monitoring point Two

4.3 Application example

GX zone was the main scope of water works, which lived in the intermediate zone betweenwater and HG Zone. Hydraulic model was applicated when examing the water supply project, mainly examing the working of water supply fromto HG in the condition of water supply. Schematic diagram of location in each region was shown in Fig.6. It contained 13.1 kilometer pipeline in DN1400 and 7 kilometer pipeline in DN1000 fromto GX, and 35.1 kilometer pipeline in DN1000 from GX to HG.

Fig.6 Schematic diagram of location

As we can seen from table1, if no more pressure, the worst adverse point of network was more than 20m. The pressure of network was maintained at about 5m, and the largest water supply quantity was 4.5X104m3/d fromto HG..Then the water supply quantity was 1X104m3/d fromto GX.

5 Conclution

The hydraulic model of water supply network is a hydraulic constraint. The operational condition of network in different hydraulic operational condition could be realized in time with the hydraulic model was built and simulated. It had guiding significance of water supply network optimization operations.

Referring to documentation:

[1] Water Research Center(WRC). Network Analysis – a Code of Practice. Water Research Center, Swindon, United Kingdom, 1989.

[2] 赵洪宾 给水管网系统理论与分析, [M] 北京: 中国建筑工业出版社