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From CAD User Mechanical Magazine Vol 15 No 02 - FEBRUARY 2002
Haestad takes the guesswork out of modelling water networks with the latest version of its’ WaterCAD hydraulic modelling and analysis package, as explained by David Chadwick
When you turn on a tap at home, you expect water to come gushing out at a certain pressure – not too much so that it blasts out all over your pinny when you are doing the washing up – nor too slow taking ages to fill a flushed loo!
In a typical small community – a small sized town – there is not just on tap that needs a constant water pressure, but 100s of thousands of taps, pipes, valves and pumps, plus a selection of tanks and reservoirs, that form a complete water or hydraulic network. All of which, needless to say, requiring water to flow through them at sufficient pressure to maintain your, and your neighbour’s taps at the right level.
Ensuring an adequate flow of water through such a complicated network is difficult enough, without having to cater for different levels of water requirement – fulfilling current needs through peaks and troughs, as well as catering for projected increases in demand from future housing and commercial developments – not to mention having some form of backup for emergencies – like a major fire.
Haestad, a Connecticut based firm, has been involved in developing CAD based hydraulic modelling and analysis systems to provide accurate simulations for water networks, for many years. Although an American Company, the software is increasingly being used throughout Europe.
Recently, Haestad introduced Version 5 of its’ modelling and analysis software which included a genetical algorithm based calibration system that enables water system modellers to refine networks to provide an optimum solution to the seemingly insurmountable problem of water distribution.
WaterCAD is a water modelling and hydraulic analysis tool that can be laid out using either Haestad by itself, in conjunction with AutoCAD, or developed as a GIS model. It includes scenario management for checking how the system reacts under different conditions. Hydraulic analysis is used to analyse the viability of potable water networks, sewage mains, fire protection systems, raw water pumping and so on.
One of its’ principal features is its’ ability to simulate requirements for excessive water demand.
It also includes Cost Analysis tools and comprehensive reporting – and permits custom data extensions, beyond its’ data sharing capabilities with GIS, SCADA and other databases, ensuring that the results of its’ analysis can be ported to virtually anywhere. And, of course, Calibration – where Haestad’s Darwin Calibrator is used to tweak the system to provide the optimum flow of water.
Laying out the water network model can be accomplished using Haestad by itself, dragging and dropping elements onto the screen. For accurate, scaled models, a DXF map can be used as a background for the development. The software includes useful modelling tools, such as zoom tools, scroll bars and aerial views, for ease of use, and te results can be exported to DXF files.
Alternatively, the network can be created in AutoCAD, using WaterCAD elements in much the same way that you would use AutoCAD elements. AutoCAD enables graphs, profiles, contours and other graphics to be brought into the drawing.
The water network can also be integrated within a GIS system – inside ArcInfor or ArcView, using GIS commands to manipulate the data with complete control over symbols and themes – and bringing in TINs, co-ordinate geometry and network algorithms.
Users can mix scaled or schematic sections in the network, schematics being particularly useful in defining tight areas of drawings, such as complicated junctions and piping areas. The networks are maintained intelligently, so that when junctions are moved, all connecting pipes snap to the new location. Similarly, removal of junctions also sees the disappearance of associed pipework.
Modifications can be made simply by inserting new elements – dragged and placed on top of the existing element 0 changing, e.g., a reservoir with a storage tank. Inserting valves, pumps and other elements into a pipe by clicking on the pipe, splits it into separate lengths, each length developing separate integrity as an element.
Once the network has been lain out, users can use Scenario Management to see how the system reacts to different condtions, assisted by development wizards. Anj unlimited number of system conditions can be described in an ‘inheritance tree’ – actions that have paths designated by ‘parent’ and ‘children’ activities. Any changes to the scenario cascades through the tree. Changes to scenarios are easily accomplished by moving the activities around, and sub models can be merged to provide much larger complex models.
Hydraulic analysis can be used to take a ‘snapshot’ of the model, holding all parameters in a steady state, or results of analysis can be garnered from a simulation performed over an extended period.
The purpose of the analysis is to calculate the pressures and flow through pipes, valves, pumps, and to extend control over these by assigning different status or settings to them, or by allowing changes to be made automatically on a time basis or as a reaction to system hydraulics.
Once the analysis has been performed it can be refined, using Field Observation and further analysis according to the parameters and algorithms in the Haestad’s Darwin Calibrator. Any type of control valve that can be used in the network can be modelled using a general purpose valve element, and the system has been designed to identify the most energy efficient or cost effective solutions to each problem.
WaterCAD 5.0 Developments
Apart from the introduction of the Darwin Calibrator, which we go into more detail with on the next page, WaterCAD 5.0 has numerous new tools and enhancements. One of the most interesting is the ability to remove network elements from the drawing (Active Topology Alternative) so that variations of the model can be assessed. When they are removed, they do not figure in calculations.
Variable speed pumps can be created out of any pumps, and controlled using the pump speed pattern.
Energy costs can be analysed, calculating the amount of electricity required to run the numerous pumps and other electrical elements around the network. The costing system can also, however, be used to calculate variable costs, assessing losses and gains that accumulate through tank level changes.
System Head Curve generation is used to find the appropriate point for inserting pumps. General Purpose Valves, like the pumps, can be used to represent areas that traditionally cause flow determination problems, such as reduced pressure backflow prevention valves, well draw-down behaviour, turbines or other situations with a unique headloss-flow relationship.
Other functions include Demand Pattern Importing, Time Variable Reservoir, Manual Fire Flow Scenarios, Flow Emitters, Totalising Flow Meters and Animation Support – all tools that are designed to provide accurate analysis and assessment of all conditions likely to affect the flow of water through a network. Haestad prides itself on having a fuller set of tools than its’competitors.
In addition to this, Haestad includes a wide number of advanced modelling and reporting tools, enabling users to question the simulation of the water network more accurately. Amongst the tools that have been enhanced in the new version of the software are Element Calculation Messages and Element Graphs that produce a printable list of elements with messages and warnings from the calculation results tab, and the graph that can show multiple element analysis results simultaneously.
Gone, hopefully, are the days when the Water Company sent around its’ workmen to dig a hole I the road, take out a piece of pipe and a valve, replace them with a different sized pipe and fill the whole in – only to return a couple of months later, dig up the new pipe and replace that with another – only because they lacked the means to assess the results before they attempted the repair. It was all performed on a basic ‘dig or miss’ basis, relying on the civil engineers experience, as much as by calculation. Haestad’s WaterCAD software, especially when it is used in conjunction with the Darwin Calibrator, takes as much guesswork out of the equation as you possibly hope for.
The Darwin Calibrator is a fascinating piece of software, and forms a significant part of Version 5.0. It enables users to refine the hydraulic model using Fast Messy Genetic Algorithms. I have devoted a separate page to its’ description. CU
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