Once we have finished the phase of terrain elevation assignment to nodes and pipes as well as the calculation of the average demands in nodes, it is time to carry out the design and calculation of the water distribution network of our project.
Of course, before that, it is important that we explain some aspects to take into account for the realization of the corresponding calculation.
The first thing you should keep in mind is that each water network must have at least one source point. This must correspond to the source of water and the pressure of the system, from which the piezometric operating conditions of the water network can be defined.
In this example network, the source node will be the “N 0” node, here on the right. So we must inform the software that it is from here that the water network will be fed.
We will go to its properties so you can see how easy this is.
I will modify the name to CONNECTION, because I am assuming that this water network will be supplied from an existing one.
Then, going down to the Node Type field and unfolding the list, you will see that in Aqueducts three types of nodes are available.
The simplest node is the one that will be used to define water demands and obtain pressures in the network. Most nodes will be of this type.
The Fixed Head Node is the one that will represent the point or points of water supply in the network. It is assumed, since the calculations are made for a peak flow—that is to say, for a specific moment of a typical day—that from this node a fixed piezometric head is maintained and that, in addition, it has the capacity to introduce to the system a flow equal to the corresponding actual demand.
And the Hydrant node is, in essence, a simple node because, at a certain moment and for certain conditions in the network operation, it will have an associated demand. But we have chosen to separate it from the simple one in such a way as to facilitate the representation of this component in the drawing area as well as to make more versatile the study of demand hypotheses of the networks that you are studying with the software. This we will be seen in detail in another video in this series.
So, in this case, we will change the node type to Fixed Head, entering the corresponding piezometric head value here.
Keep in mind that this fixed head node can, in real terms, be any element, such as a tank, reservoir, and even a pumping station. The important thing is that, for any of these elements, you are able to extract from it the operating piezometric head for the design condition of the system.
For example, if the source were a tank or reservoir, it is common to take the average water elevation in it as piezometric head. Or, if you want to be on the “safety” side, the minimum elevation of water in the tank, although you should not lose sight of the issue that the volume of water is enough to supply the corresponding water demand.
So, we have everything ready to perform the hydraulic calculation of the water distribution network.
At this time, although performing the design is still required—that is, modifying the diameters of some pipes, as they are all currently in 75 millimeters, the value I have defined by default in the Settings tab—I’m going to click the Calculation button to see what we get.
The calculation is carried out successfully and no warning messages, such as the existence of negative pressures, are shown.
If we go to the Nodes and Pipes tables, in the Water Network tab of the main window, you will see the results.
In these tables are highlighted in light red color those nodes or pipe sections that do not meet any of the control conditions we have previously defined. For example, in the case of pipes, we see that there are a number of sections that do not meet the minimum velocity requirement defined in the initial project’s settings.
At this level, we still need to consider the calculation finished, so I better explain how to visualize results through annotations in the drawing area.
In the RESULTS tab we have the button that gives access to the Drawing’s Annotations dialog.
Here you can select for which object, Node or Pipe, the result values will be shown. In this case I want to show only the pipes sections.
I activate the box to enable the list of available properties here on the left.
Select Diameter, Flow, and Velocity to be shown in the drawing area.
In this case, you could enter a prefix for each added property here, but if you leave it blank, that the software has by default will be used. You will see that in a moment.
I click the save button to the right and, finally, I will change the Height of the text.
I click OK, then I’ll click Yes in this dialog, and you will now see the annotations in each pipe section.
Now we can visualize, as long as we make changes in the water distribution network, the results of our design through tables and annotations.
When it comes to the design of water distribution networks, it is necessary that the network be “loaded” with the maximum daily and hourly demands in order to guarantee its operation in the most critical situation.
Thus, since what has been specified or calculated automatically for nodes are average water demands, it is necessary to have a way to apply an increasing factor that allows us, easily, to obtain the demand condition required for design or calculation of the network.
In Aqueducts, to handle such situations, the use of Calculation Hypotheses has been proposed, which allows you to maintain in each project scenarios of demands or operating conditions, as we will explain in another video. In such a way you can evaluate various conditions and make a decision regarding the dimensioning of the network’s components.
When we go to the WATER NETWORK tab, you will see that in the Calculation and Design panel, a Hypothesis is set as current or active: the Base Hypothesis.
In each project this hypothesis will by default exist and it will not be possible to eliminate it from the project, although you can edit it by clicking this button.
Note that the dialog contains three tabs:
From the first tab, the only one in which we can make modifications for the base hypothesis, we will change this increasing Factor or Peak Demand factor to the required value by the local regulations to carry out the design of water networks.
In our case, two point five represents the maximum demand factor for this network’s design.
If we quickly review the Nodes and Pipes tab, we see that they contain the respective lists for the active network’s objects in this project.
Although in the base hypothesis no modification can be made, you will see that it is possible to create additional hypotheses in which you can modify parameters such as the demand or piezometric head of one or more nodes and, for pipes, you can modify parameters such as diameter, friction coefficient, or its operational state; that is, set it as closed or open in the current hypothesis. We will see it in detail in other videos.
Then, to modify the Peak factor, I click the button save to store the changes and I close this dialog.
Observe the flow rate and velocity in the inlet pipe after clicking the calculating button once more.
It is certainly observed that the peak factor has been correctly applied, since both the flow and the velocity have increased in all pipe sections.
If we go to the tables, you will now see that there is a significant number of nodes in which the pressure value is highlighted in red. This is to indicate that its value is below the minimum pressure that we have established in the General Settings of the project, which, as you see here, has been set at 15 meters of water column.
Here, to show you another of the characteristics of the software later, I will change the local head losses calculation method to coefficients, in which case the values we have defined in this table are used.
Returning to what concerns us, the design of the water network, it is clearly necessary that the diameters be modified to not only reduce the high velocities that we have in pipes like these, but also to improve pressures in nodes by reducing head losses.
If this calculation were done manually, you should know that it is required now to modify, one by one, each pipe section diameter, redoing the calculation so as to make the necessary adjustments to achieve the design velocities.
With Aqueducts, if you display the available options under the Design button, from the Calculation and Design panel, you will see that there is the option to let the software, based on the velocity design criteria you have selected in the project settings, perform automatically the assignment of diameters to pipe sections.
In this case, and let’s go back to the general settings, the option of finding the diameter for a fixed velocity is available, but the chosen one is the option of selecting diameters based on a maximum velocity in accordance to values in this table.
The important thing here is that we must indicate the internal diameters that are available in the pipe library we are using in the project. As we see here.
So I will quickly make the modification, deleting the unavailable sizes in the library from the velocities table. Remember, the software will search for the calculated diameter the one that is close to one of the diameters of the corresponding pipe library.
With this done, it only remains that we use the automatic design option.
We see that the diameters are modified quickly to adapt to the capacity related to the specified velocities in each diameter.
If we go back to the nodes table, you will see that now all the pressures are above the minimum one.
Certainly, in terms of minimum velocity, there are pipe sections that cannot comply because they have the minimum diameter.
While others, like these, could have a lower diameter in order to improve the maximum velocity, it is a matter of refining the design according to our specific criteria.
One option available in these tables is to order nodes and pipe sections according to a property.
For example, if I want to sort by diameter, I double click on the header and this dialog is shown.
In this case, with the nominal diameter property pre-selected, you could well change to the one of your preference. I keep ascending order and click OK.
And there we have them. It just remains to make the adjustment to these pipe sections to resolve, if necessary, the issue of low velocities.
But let’s continue knowing what the software has done for us in the calculation and design.
Remember that we have previously modified the method of local head loss calculation by introducing the fittings’ localized head loss coefficients.
If we go to the properties of any pipe section.
We find that, on the one hand, a list of fittings is created with the purpose of generating the lists of materials for the water distribution network. I want to clarify that this is independent of the method you have selected for the head loss calculation; that is, it will be done whenever you click the calculation button.
Now, depending on the selected method, if you go to the list of fittings assigned to this section by clicking this button, you will see that the software has automatically included the corresponding elbow from the parts list with localized head loss coefficient. And, additionally, it has added the respective Tee at its end downstream.
Both pieces will be used to determine the local head loss coefficient to be assigned in the head loss calculation in this pipe section.
Observe the next pipe section that has straight alignment.
Here, only one Tee and one reduction in the downstream node will be required for the head loss calculation.
Let’s now see this pipe section to the extreme.
There is only the 90 degree elbow needed to make the change of alignment.
Since it is not part of the pipeline in the strict sense, this elbow is not shown in the materials list report for this pipe section,
but, if we go to the properties of this node,
we see that it is included in its list of materials.
Keep this in mind: For the purposes of the localized head loss coefficients, only the pipe sections may have assigned accessories.
And, for the purposes of generating lists of materials, both components, nodes and pipes, may have listed the fittings required for the construction of the water network.
Ultimately, these lists in nodes and pipes are those that are consolidated to generate the list of materials you get here in the RESULTS tab.
As you see, the calculation is generated properly, ready to build your project.
The other automatic design option is using constant velocity.
We are going to make the change in the settings and redo the design.
But before this, I will use the global editor to set all the diameters at the minimum, so I guarantee that it starts searching for diameters from the smallest possible in each pipe section.
Here I can select all the sections by clicking the control keys plus the shift and down arrow from the keyboard.
Now, I redo the calculation and design.
The diameters change, as in the case in which we use the table of velocities.
Finally, if we go now to the longitudinal profiles we had created in this project, you will see that the diameter change of the pipe sections is shown.
Of course now, having hydraulic results, we can go to the profile configuration to include in each pipe section some additional information.
For example, diameter, length, type of pipe and bedding class, information generally required in construction drawings.
We return to the profile, and…
we have them there!
Thus you have seen how simple it has been to perform the design as well as the generation of the required information to generate the documents and plans for the project.
Of course there are still other features to explain, and that is why we recommend you keep an eye on the next videos in this series.
Thanks for your attention.