Dear Scott PRV considers it's downstream pressure to maintain it fixed. the pressure of upstream is not important for PRV. It just adjusts the pressure of downstream regardless of upstream pressure. Regarding your Wiki here : You wrote: '... With no modulation on the PRV, it is not allowed to change the size of the opening to compensate the loss in pressure upstream of the valve.' or '... the valve will modulate, which will result in higher minimum pressures upstream of the PRV. ... because the valve opening can change to compensate for the loss in pressure [of upstream] caused by the pump shutdown.' Why do you persist on upstream pressure instead downstream pressure at the PRV? have a look at two screenshots to make it more obvious: Both graphs are the HGL at downstream of the PRV, but the first one is before Modulating and the second is after Modulating PRV, and Hydraulic Grade Setting is equal to 48.8m. As you see, the HGL after modulating drops near 47.54m whereas HGL before modulating is more nearer to Hydraulic Grade Setting (48.02 of 48.8). It shows that modulating PRV Makes it's HGL (at downstream) more far from Hydraulic Grade Setting (48.8). I hope to explain my thought obviously. H.
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Forum Post: Modulating PRVs
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Forum Post: RE: Darwin Designer
Hello Simon, Darwin Designer has option of performing multi-objective optimization. See the screenshot below. There is good information about model optimization techniques, in the Advanced Water Distribution Modeling and Management book on pae 644, Appendix D. The book is available here.
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Forum Post: RE: CIVIL STORM
Hello Daniel, i hope that, you have got the CivilStom, by now. Here is the learning resource for you to get started with the CivilStorm as a new user.
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Forum Post: RE: Darwin Designer
Thanks alot
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Forum Post: TCV in WaterCAD
Ref :- Hi Regarding Victor's question, Assume a pipeline with a TCV. Coefficient Type is 'Discharge Coefficient' (Cv). initial Cv= 0.25 Fully Open Cv: 0.5 Valve Type is Globe Pattern (Valve Settings) is Fixed. Run the model. How Q and Relative Closure of the TCV are calculated? What is the role of Cv in calculation of Q and Relative Closure? I know how a TCV operates and how Headloss, Cv and relation between relative closure and opening area in various kinds of valves are considered. Then my question is about how of calculating Q and Relative Closure in TCV? I mean when the software knows Cv initially, Cv fully open,diameter, valve type and other hydraulic characteristics of the model, How does it do to calculate a) Flow and B) relative Closure and C) relation between relative Closure and Cv? About C): How does Cv affect on Relative Closure mathematically and based on formula? Increasing in Cv results in decreasing Relative Closure. But what is the formula which is followed?
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Forum Post: RE: Negative pressure at pump
Hello Sameh, I have moved your post to the Haestad | Hydraulics and Hydrology forum. A negative pressure at a pump means that the hydraulic grade at either side of the pump is below the physical elevation. Take a look at a profile view for a better visual - it might be due to the upstream boundary condition elevation (reservoir or pump). You can read more about this in the following article in our wiki: Troubleshooting negative pressures at pumps, junctions, & other node elements
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Wiki Page: Why don't my CivilStorm results for peak flow don't closely match my StormCAD results for peak flow?
Applies To Product(s): Bentley CivilStorm, Bentley StormCAD, Bentley SewerGEMS Version(s): 08.11.XX.XX, 10.00.XX.XX Environment: N\A Area: Layout and Data Input Subarea: N\A Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem My CivilStorm results for peak flow don't closely match my StormCAD results for peak flow. What's the reason for this? Problem ID#: 78320 Solution The difference in the peak flows is because there is a difference between the rational method used in StormCAD (STMC) and the modified rational method being used in CivilStorm (CSD) for this model. Rational method (STMC), as you may know, determines the flow via the Q = CiA formula and it uses the Tc to determine the intensity. The modified rational method (CSD), however, uses the Q = CiA to find the flow, but the intensity is determined from the global storm event duration (Components > Global Storm Events). If you look up the duration list in the global storm events dialog box on your IDF curve, in the Storm Event dialog, you'll see that for the given storm you're looking at the intensity is probably not the same as the intensity that you were getting in StormCAD for the same storm event. This explains the reason that you are seeing a lesser flow at the peak in CSD vs. STMC. One option that you might want to consider using to work around this issue is the unit hydrograph method. Another difference that should be pointed out is that STMC is a peak flow steady state modeling software, which models the peak flow at one moment in time, whereas CSD models flow over time. CSD therefore needs to develop hydrographs from them to route flow through the system. STMC is ideally used to design systems (using the standard straight rational method) where overflow is not intended vs. CSD is used to analyze system (using a hydrograph method) especially when you need to account for overflow volume through routing.
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Wiki Page: How is flow calculated in StormCAD?
Applies To Product(s): Bentley SewerGEMS, Bentley CivilStorm, Bentley StormCAD Version(s): 08.11.XX.XX Environment: N/A Area: Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem How is flow calculated in StormCAD? Solution Similar to a time of concentration, a system time (or controlling time) is the amount of time it takes for all contributing parts of the storm sewer to reach a given location. This includes a catchment's time of concentration, and pipe travel times. When combining rational loads, the controlling time is the greatest of the individual loads' system times. This system time is used as the duration of the storm when determining peak intensity, and therefore peak flow. To avoid unreasonably low storm durations and unreasonably high rainfall intensities, many regulatory agencies impose minimum storm durations, typically 5 or 10 minutes. StormCAD allows you to specify a minimum storm duration and uses this as the controlling time when the computed time is too low. In these cases, StormCAD carries the computed system time throughout the system, but continues to calculate intensity based on the minimum allowed time (until the system time rises above the minimum). For example, consider a catchment at I-1 with a time of concentration of 4 minutes, and a minimum allowable duration of 5 minutes: I-1 Catchment time of concentration: 4.0 minutes StormCAD computes flow based on: 5.0 minutes P-1 Pipe travel time: 0.5 minutes J-1 System time (4.0 + 0.5): 4.5 minutes StormCAD computes flow based on: 5.0 minutes P-2 Pipe travel time: 1.0 minutes O-1 System time (4.5 + 1.0): 5.5 minutes StormCAD computes flow based on: 5.5 minutes This 5.5 minutes is used as the duration in the intensity vs. duration equation used to calculate i in determining the flow using: Q = I ( CA )
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Wiki Page: Unaccounted for flow in SewerGEMS
Applies To Product(s): Bentley SewerGEMS Version(s): 08.11.xx.xx Environment: N\A Area: Calculations Subarea: N\A Original Author: Jesse Dringoli, Bentley Technical Support Group Problem When computing a model with the Explicit (SWMM) calculation engine, what could be causing additional, unaccounted for flow to appear directly downstream of a force main (pressure pipe network)? Problem ID#: 41795 Solution There are several things that could be causing this. Here are some general suggestions: 1) Consider using the variable time step calculation option by selecting "True" for "Use Variable Time Step?". This will allow the program to lower the routing timestep if necessary, which could provide more accurate results in this situation. 2) If your pumps have a fast cycle (turn on/off quickly) try using a small calculation timestep, such as 5 seconds or less. 3) Try choosing "Keep" for the "Inertial Terms" calculation option. This will use all of the terms in the St. Venant equation for partial flow. 4) Consider checking the model results with SewerGEMS' native Implicit calculation engine. Note that you can check the mass balance between two nodes in a network by looking at the Node Inflow Summary table in the SWMM5 output file, which appears after computing the model. This will show the lateral flow and total inflow at each node.
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Forum Post: Lock pipes in waterGEMS.
Hi All, I want to design a water distribution network which is having some existing old pipes, while designing i generally use global edit function, due to which the attributes of existing pipes are changing. I want know that is their any option in WaterGEMS by which i can lock all attributes of existing pipes. (other than making pipe active and inactive. Thanks.
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Forum Post: How to select junctions connected to any particular ( 100mm ) diameter pipes?
Hi All, I am designing a water distribution network in which i want to select all junctions connected to 100mm and 150mm dia pipes. My network contains more that 3000 nodes, so selecting manually is very difficult. Is their any option or predefined query in waterGEMS to perform this action. Thanks.
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Forum Post: RE: Lock pipes in waterGEMS.
Nawnit, We don't currently have an feature to lock existing attributes of elements, but based on the description of what you're trying to accomplish the following wiki on globally editing a selection set of elements should resolve what you're attempting to accomplish. communities.bentley.com/.../8603.how-can-i-globally-edit-certain-elements-in-a-flextable-such-as-from-a-selection-set I'll put in an enhancement for a feature that locks existing attributes for elements. Regards, Mark
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Wiki Page: Analyzing concentration of multiple constituents, or a multi-point trace
Product(s): Bentley WaterGEMS, WaterCAD Version(s): 08.11.03.19 Environment: N\A Area: Modeling Subarea: N\A Problem Is is possible to run a multi-point trace analysis, where more than one source can be selected? Or, is it possible to track concentration of multiple constituents? Problem ID#: 81530 Solution This can be done with the Water Quality Batch Run tool, available starting with WaterCAD and WaterGEMS V8i SELECTseries 3 (08.11.03.17). See Also What's new in WaterCAD and WaterGEMS V8i SELECTSeries 3?
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Wiki Page: I'm seeing zero or N/A for water quality results (trace, age or constituent)
Product(s): Bentley WaterGEMS, WaterCAD Version(s): 08.11.XX.XX Environment: N\A Area: Calculations Problem After setting up a trace, age or constituent analysis, I'm not seeing any calculated trace, age or constituent results. Solution 1) Confirm that the Calculation Type in the calculation options is set appropriately. If it's set to "hydraulic only", water quality results will not be computed. 2) Make sure the model is successfully computing. If you see red messages in the User Notification window after computing the model, there may be issues preventing the model from computing, which will need to be addressed first. 3) When viewing the water quality results, ensure that you're either looking at the maximum or minimum, or a graph. If you're only looking at the "Trace (Calculated)", "Age (Calculated)" or "Concentration (Calculated)" field for an element directly after computing a model, that will be showing you the result at time zero. Either use the Time Browser and step through time to see the calculated result change, or right click the element(s), choose Graph and select the water quality result in question. 4) Ensure that the respective alternative has been set up correctly, or for Age, make sure there is a source of fresh water. For an age analysis, the calculated age represents how long the water at that element has been in the system. In a model where there is no source of "fresh" water (a reservoir), the age of the water on all nodes will be the same. However, by adding a reservoir to the system, age will start to vary on different nodes. For a Constituent analysis, make sure the constituent alternative is set up correctly with the right constituent, make sure that alternative is assigned to the right scenario, and make sure the constituent itself is set up correctly. Confirm the correct units and values entered. For a Trace analysis, make sure the trace alternative is set up with the correct For an Age analysis, ensure that there is a source of fresh water. With Age, the calculated age represents how long the water at that element has been in the system. In a model where there is no source of "fresh" water (a reservoir), the age of the water on all nodes will be the same. However, by adding a reservoir to the system, age will start to vary on different nodes. Note : if you need to analyze multiple trace sources or multiple constituents, use the Water Quality Batch Run feature. See Also How can I troubleshoot my model when my water age results don't appear correct? Water age results in a pipe are different than the age in a downstream junction Age (Calculated) vs. Age (Minimum) vs. Age (Maximum) Is WaterGEMS capable of modeling the formation of constituents in networks? The concentration at the stop node directly after a constituent source in a tank is decreasing rapidly How to find volume of water coming from a trace element? Analyzing concentration of multiple constituents, or a multi-point trace
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Forum Post: RE: Hydraulic modeling - required data
Re: "Do you mean by "measuremet informations" geodetical data (like cross-sections) or hydrological data?" If you use one of Bentley Hydraulics and Hydrology products such as CivilStorm or PondPack, the pond element needs to have a defined elevation-area or elevation-volume curve, along with an outlet structure (weir, orifice, etc). These products have an easy-to-use interface for laying out or importing this information. For pond outlets, you can enter the size and elevation of the various components. The software will develop an elevation-flow-tailwater (EQTW) rating curve to simulate the pond water level over time based on the inflow hydrograph and the downstream hydraulics. Re: "The ability to transform and capture floods is the main question." I assume your question is regarding the data necessary to accurately model these ponds and to ensure that they do not flood and that they attenuate the flow down to pre-development conditions. Having the geometry/dimensions of the ponds will be important, as they have an impact on the effectiveness. A larger pond will be able to store more water without overflowing. The pond outlet is also important, as it effects the outflow. Too much outflow and you won't meet predevelopment target flow rates. Too little outflow and the pond may flood or will be oversized. If the ponds are existing, you should be able to extract the information from a terrain model if you have it. If the ponds are proposed, you could propose a size and use the PondMaker tool in PondPack and CivilStorm to size the pond to meet your goals. HEC-HMS may be able to perform a similar analysis, though I'm not familiar with it. Free software will have its disadvantages, though. PondPack and CivilStorm are more modern, easier to use, have more features, and are supported by Bentley staff like myself.
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Wiki Page: Can I model fluids other than Water?
Applies To Product(s): Bentley WaterGEMS, Bentley HAMMER, Bentley WaterCAD Version(s): 08.11.XX.XX Environment: N/A Area: Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem Can I model fluids other than Water? Solution Yes, and the steps below describe how to do this. Please note that only Newtonian liquids are valid, and you might need to adjust your pump definitions if the viscosity of your fluid differs from water. Furthermore, as Hazen-Williams friction method is an empirically based formula, its calculated friction losses are only applicable to Water @ 20 deg C. It should not be used for other liquid types (and you should use Darcy-Weisbach instead). 1) Go to Analysis > Calculation Options and click on the calculation option that you'll be using for this analysis to access the properties 2) Go to the Hydraulics section towards the bottom of the properties window and click the ellipsis button on the right side of the liquid label cell as seen below. 3) This opens the Liquid Libraries for the Engineering Library and you can select the liquid that you'd like to use from there. Note that on the right hand side of the window the liquid properties like Kinematic Viscocity, temperature, Vapor Pressure, and the bulk modulus of elasticity are displayed. 4) After you create or decide on one of these use the select button to choose that liquid. 5) If you'd like to create a new liquid with different characteristics go to Components > Engineering Libraries and expand the liquid library. Left click on the 'Liquid library.xml' label as shown in the screen shot below and then click the 'Add Item' option. Finally, enter your data and name the new liquid. Click close when done. A note on Temperature Change in HAMMER Note that only one liquid temperature can be set for a given simulation run. This is notable in a case where you have a significant change in temperature in the network being analyzed, such as for a heat supply network. From the HAMMER Help topic “Bentley HAMMER V8i Theory and Practice”, With Bentley HAMMER V8i, you can analyze drinking water systems, sewage forcemains, fire protection systems, well pumps, and raw-water transmission lines. You can change the specific gravity of the fluid to model oil or slurries, for example. Bentley HAMMER V8i assumes that changes in other fluid properties, such as temperature, are negligible. It does not currently model fluids with significant thermal variations, such as can occur in cogeneration or industrial systems. So, unless you can make a valid, conservative assumption, then the transient results may be skewed if you have a significant change in temperature. One approach is to try a sensitivity analysis: do several model runs, varying the liquid properties for multiple temperatures. If there’s no notable difference in transient response, then you might conclude that HAMMER can model their situation OK. Or, if there is a clear separation between the segments of the network at two different temperatures, you may be able to do two separate model runs.
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Forum Post: RE: How to set the pumps of a fire network?
Hello Joao, It sounds like you are having issue computing the initial conditions calculation part of HAMMER. If that is the case, the first thing I would do is confirm that the input for the Discharge to Atmosphere elements is accurate. If you do not know the typical flow and pressure drop, the orifice equation can be used to help find this. Otherwise you can look at the following link, which has information on troubleshooting steps that you can try: communities.bentley.com/.../8769.troubleshooting-network-unbalanced-or-cannot-solve-network-hydraulic-equations-user-notification . One thing I will mention is that HAMMER basically takes an initial result for the system to apply it to the transient run. The pumps are controlled by an operating rule or, in the case of the "Shut down after time delay" transient pump type, a time value at which the pumps will stop operating. You will not need to necessarily run an EPS run to do this. If you were running a pump shut down analysis, you could just run a steady state analysis with the pump on at a critical time. You would need to make sure accurate demands, tank level, and other element statuses are there too. This would simplify matters somewhat and may allow you to compute your model. If this doesn't help, we will need to see a copy of the model files. There are two options for sharing your model on Communities, whichever you choose please be sure to zip your files first. The first option is to attach the zip file containing your model to your reply on the forum using the Advanced Reply Editor (you'll find the link below and to the right of the reply box). If your data is confidential please use the instructions in the link below to send it via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley employees. Please be sure to reply on this thread with the name of the file after it has been uploaded. communities.bentley.com/.../7079.be-communities-secure-file-upload If you upload the files to Sharefile, please post here with the name of the files so that we know they are available. Regards, Scott
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Forum Post: RE: Use of Hydropneumatic bladder tank initial volume
Scott, I determined the problem was with the pumps and not the hydropneumatic tank. In the steady state analyses, I determined the pump speed required to match the demands and pressure setpoint and used this in the pumps’ initial settings. Pump Type is “Variable Speed/Torque”. I then set up a pattern [Operational (Transient, Pump)] for the pump speeds with the starting multiplier equal to the initial speed determined from the steady state analyses with subsequent changes in speed to accommodate demand changes. However, the pattern should have the starting multiplier equal 1 and the subsequent multipliers be equal to the ratio of subsequent speed to initial speed. This allowed the pumps to run stably until the pattern changes it. Thank you for your time and response. Lindle Lindle D. Willnow, P.E. Technical Leader III, Hydraulic Modeling AECOM Water Direct +1- 978 -905-3228 Mobile +1-978-609-4116 Cisco 1233228 lindle.willnow@aecom.com AECOM 250 Apollo Drive Chelmsford, Massachusetts 01824 Front Desk +1-978-905-2100 aecom.com
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Forum Post: RE: Use of Hydropneumatic bladder tank initial volume
Hi Lindle, I'm glad to hear that you were able to resolve the problem. The below article is related to this situation with the relative speed mismatch with the initial operating rule multiplier: communities.bentley.com/.../16427.initial-surge-occurs-when-the-initial-relative-speed-factor-is-less-than-1-0
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Forum Post: RE: How to select junctions connected to any particular ( 100mm ) diameter pipes?
Hello Nawnit, First crate a selection set of pipes with diameters 100 mm & 150 mm. Set a filter in pipe flex table for 100mm & 150 mm diameter pipes and create a selection set of those pipes. Or crate a query for pipes with diameters 100 mm & 150 mm and create a selection set of those pipes. After creating the selection set, please select those pipes in the drawing and open Network Navigator tool and click on the query, Network Navigator>Netowork Trace>Find adjacent nodes, this will select the adjoining nodes of the pipes 100 mm & 150 mm diameters. Please make sure that you have selected the pipes in drawing before running this query. Below is the video for the same. (Please visit the site to view this video)
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