If you're interested in using the same calculation options in multiple models, I would recommend using Seed files. Basically you would set up the calculation options the way you'd like, plus other things like units, libraries/catalogs, color coding, annotations, etc, then save as a Seed file. When you want to start a new project, you would "open from seed" , essentially starting from a template. More on that here: Save Time using Engineering Libraries, Shared Flextables and Seed Files
↧
Forum Post: RE: Hammer-Calculation Options
↧
Wiki Page: Troubleshooting unstable SewerGEMS and CivilStorm results using the implicit solver
Applies To Product(s): SewerGEMS, CivilStorm Version(s): 08.11.XX.XX, 10.XX.XX.XX Area: Modeling Original Author: Mark Pachlhofer, Bentley Technical Support Group Problem How do you troubleshoot SewerGEMS or CivilStorm results using the implicit solver? Solution If your hydraulic model provides unexpected results or high continuity error (mass balance), try the following steps: 1. Check the model for data entry problems: Use the Validate command and look at the warnings and/or errors that are reported. Fix as many as you can while keeping in mind the goal of the model is to make it resemble what you have in the field as closely as possible. When you Calculate the model, validation routines are performed that are not included during a Validate operation. Review the warnings and/or errors that are returned after calculating the model too. Examine Graphs and Profiles. Create Flow plots at splits and at pump discharge areas and look for jagged peaks in the plot. Use the Hydraulic Reviewer to pinpoint areas of volume deviation, to pinpoint areas of the model to check first. Common data problems: Conduits or Channels: I ncorrect channel or conduit slopes : Reasonable slopes are generally small and rarely negative. You can view slopes along a reach visually by using the Profiles feature. You can find unusually large or negative slopes through User Notifications and FlexTable reports. You can Color Code link elements by Slope and look for excessive values. If the model has parallel conduits connected by a flat (slope value of 0) conduit, try making that conduit Inactive. I nc orrect Channel or Conduit size : Look for unusual size changes along a reach. Color code drawing by Diameter to look for this type of discrepancy and or create numerous profiles for an even better visual of your pipe sizes. This will help you locate bottlenecks in the system that could be causing calculation problems. You will also see user notifications if the diameter decreases as you move downstream. A mix of very long and very small pipes . Eliminate or combine short pipes because their effect on routing is small. Break exceptionally long pipes into mutliple pipes that are each roughly the same length as other pipes in the network. Very low flows : If flows are less than 0.01 cfs (0.001 m3/s), depths may fall below accuracy tolerances. Consider omitting dry pipes from the model (or combine/skeletonize them out) Pumps and pressure pipes: Pumps operating at or near the shutoff point defined on the pump curve When pumps operate at or near the shutoff head point on their curve review downstream results for accuracy. In the past there have been cases where graphs of the hydraulic grade would show large jumps that were out of the range of the normal pump operating points. To resolve this adjust the pump curve by reducing the flow or head accordingly to produce a curve that operates near the point the pump is running at in the model. The new pump curve can be tested using the SewerCAD (GVF-Convex solver) because the pump calculations are done using the pressure solver, which is more stable for pump calculations than the implicit solver. Pumps using a multiple point pump curves that have large differences between flow or head values on the pump curve. Pumps that cycle on and off very quickly - check the on/off elevations and wetwell size/operating range. Make sure the pump curve is sized appropriately for the wetwell size. Use a small calculation timestep if fast pump cycling is needed. Manifolded pumps (pressure pipes combining together). This may require a small calculation timestep. The Implicit solver tends to be better than the Explicit (SWMM) solver with this. Unnecessary check valves on pressure pipes. Users commonly use the option to have a check valve on pressure pipes that are directly downstream of a pump, but this is unnecessary because pumps already have built in check valves. Keeping them can cause unnecessary difficulty for the solver. Parallel pumps - the short pipes adjacent to the pump may need to be designated as Virtual. Try toggling the "is virtual?" setting. Ponds and pond outlet structure s: Flow control structures on relatively small storage nodes (ponds, wet-wells). Consider combining ponds, modeling as manhole storage or using a very small calculation timestep. Unusually small ponds compared to their inflow. Consider modeling as a manhole with downstream conduit start control structure, or use a very small calculation timestep. Significant backwater/tailwater effects against an upstream pond outlet structure. If a backup occurs and acts as tailwater for an upstream pond outlet, this can be extremely challenging to solve. A very small calculation timestep may be necessary, the Explicit (SWMM) solver may need to be used (with a very small Routing Step). Or, consider changing the model layout or otherwise resolving the downstream backup to prevent this challenging situation. Conduit control structures : Using a start control structure tends to be more stable than a stop control structure Use a smaller calculation timestep in cases where a large change in flow can occur with a small change in head, such as when using a weir. Significant backwater/tailwater effect against a conduit control structure can be challenging to solve. A very small calculation timestep may be necessary, the Explicit (SWMM) solver may need to be used (with a very small Routing Step). Consider using an approximate pond (representing the ponded area upstream of the control) with pond outlet structure, which might work better in some situations Storm Data: Make sure the storm data entered has labels and the data entered is correct. Verify data input in the following other challenging situations Flow splits at weirs and orifices that are dry at certain points during an extended period simulation. Hydrograph rapidly changes within a short time (minutes). Very sharp flood waves - check catchment runoff hydrographs to make sure they are correct. Near-critical slopes. Significant and abrupt changes in the conduit size, shape and/or slope. Looped networks. Significant backwater conditions. System inflows vastly exceeding the system capacity resulting in mass flooding. 2. Simplify where possible Dynamic solvers tend to be complex, and little changes can sometimes make a big difference. What you should keep in mind when creating a dynamic model is to keep things as simple as possible and only model what you really need to study. In other words, if there are some conduits that can be left out because they won't have a significant effect on what you are studying or don't provide a lot of flow (near-dry) don't put them in the model or take the flow they would produce and add it to another node element as an inflow. With dynamic modeling less is better than more. If you're working with a very large model, you may have a much easier time splitting it into smaller subsections if possible. Then, work on the sections one by one. Trying to troubleshoot results in a very large model can be cumbersome and overwhelming. Examples 1) Parallel conduits with the exact same physical properties . Instead of putting both conduits in the model you might model this as one conduit with 2 barrels. 2) A pond with an outlet structure. Let's say the outlet structure was made up of a 24 inch orifice and a weir at the very berm of the pond. After going through the outlet structure the water goes into a 24 inch conduit. Assuming the water never gets up to the level of the weir what you could do to simply this situation is set the Pond Outlet Structure property for "Has control structure?" = 'No'. In this situation, this can be done because the conduit was the same size as the orifice, so the conduit will act as the controlling structure for incoming water. 3) A wet well with a sanitary load. Remove the sanitary load that is directly on the wet well and add it to a manhole upstream of the wet well or create a dummy manhole directly upstream and connect it to the wet well. Before: After: 3. Adjust the calculation options to reduce the continuity error Default values for calculation options will work for the majority of cases, but some systems need small adjustments to converge. When the calculation is moving very slowly (you can observe that the model is stuck at certain times) or the results show apparent instabilities, it is an indication that the model is experiencing difficulties in converging to a stable and robust result. Try adjusting calc options in the order below. This is an iterative process and only one option should be adjusted at a time to see whether it gives better results or worse results. If the choice provides better results see if you can adjust it again more in the same direction to provide even better results than the first choice. For example, if changing the computational distance at 50 ft provides a continuity error of 25% and adjusting to 10 feet provides a continuity error or 15% then try to adjust it further to 5 feet to see if you can reduce the continuity even more. The goal with this is to get the continuity for the model under 5% and the lower the error the more accurate your results. Initial conditions: Options include warm start or transitional start. Try both and see if one gives better results for your system. Calculation Option Suggested Range of Values Computational Distance 5 ft - 75 ft Calculation Time Step 0.005 hr - 0.025 hr NR Weighting Coefficient 0.7 - 0.990 Relaxation Weighting Coefficient 0.6 - 0.990 NR Iterations 5 - 20 LPI Coefficient 1.0 - 15.0 Most of the time you can get the continuity error under 5% using the 4 options above. If you still need to adjust things after that continue in the order below. Try an NR Weighting Coefficient value of between 0.9 and 0.99 with the default Computational Distance and Calculation Time Step. Set NR back to default and try reducing the Computational Distance value. Set Computational Distance back to default and try reducing the Calculation Time Step value. Keep the Calculation Time Step the same and repeat the above steps. Try increasing the the NR Iterations to 20. Try increasing the LPI Coefficient to a value over 5.0. You do not need to go higher than 15. Note: There is no absolute rule on whether the time step, LPI Coefficient, or the NR weighting coefficient should be changed or to what specific value; normally you should reduce the time step and increase the NR coefficient but sometimes the opposite can also help. 4. Isolate problems areas: Isolate the problem area by incrementally deleting small sections of your model and re-computing. This may help you narrow down the source data that the engine has trouble with. It may expose data entry issues or areas that are exhibiting common modeling difficulties. 5. Determine at what time step the problem occurs. Look for what is happening at that time. Is a weir beginning to overflow? Is it the first time a large pump comes on? Sometimes it's easiest to look at your user notifications for the time or locate the problem on a profile and slide the time browser bar to that location before examining the model. 6. Switch to using the Explicit (SWMM) numerical solver (Analysis > Calculation Options > Click on the active option to open the properties). If there are problems when using the SWMM engine, try changing the Routing Method from Dynamic Wave (default) to Kinematic Wave or Uniform Flow. These methods do not handle backups as accurately as dynamic wave, but they tend to be more stable. If the results are still not stable with the SWMM solver (as seen in the summary output text report), try reducing the Routing Time Step calculation option. Suggested value range: 1.0 sec - 30 sec. Smaller values tend to yield more stable results. Note: Headlosses at nodes are ignored during periods of supercritical flow. Troubleshooting unstable SewerGEMS and CivilStorm model results using the Explicit SWMM Solver See Also Pinpoint Mass Balance Problems with the Hydraulic Reviewer
↧
↧
Forum Post: RE: SewerCAD Shapefile Background and Relation to Ground Elevation
Dustin, The Terrain Model feature is what you might have been thinking of. This is similar to background layers in that it is inserted and draped over the model, but Terrain Models can be set to automatically update ground elevations of elements. It is also similar to the Trex tool that Mark mentioned, but you can visualize it in the model (like a background layer) and set it to automatically update ground elevations as elements are added or moved. You can read more about it in the article that Mark linked to, and here: communities.bentley.com/.../16887.using-downstream-trace-with-digital-terrain-models
↧
Forum Post: RE: Sewergems Infiltration (L/s/ha) and
Hamid, The RTK method is often used to allocate Infiltration (I&I) to nodes in the model based on area data. With the Explicit (SWMM) solver, the SWMM RTK method is loaded at manholes. With the Implicit solver, it is configured in catchment areas. You can read more about this in the Help and in this article: How do you enter the SWMM RTK information into a SewerGEMS or CivilStorm model? If you do not wish to use the RTK method, you could consider the Projection by land use method in Loadbuilder. This will assign manhole loads based on area data and flow per area. More on this here: How do each of the Loadbuilder methods work?
↧
Forum Post: SewerGEMS+ Extreme load factor+DIversion
Hi I am analyzing an existing complex sanitary system which has a diversion on the system and Harmon factor to be applied to it and surcharge to be check for the wet weather. I prefer to go with the implicit option to calculate the diversion automatically (instead of rating curve table), but the issue is the implicit don't apply the extreme factor. Actually there are lots of diversion structures in the system and I don't want to go with rating curve table and steady state.
↧
↧
Forum Post: Surge vessel failure
Dears: how i can model Surge vessel failure in bently hammer. thanks
↧
Forum Post: RE: Surge vessel failure
What exactly do you mean by "failure"? Did the tank rupture, did it run dry, did somebody close the fill/drain line?
↧
Forum Post: RE: Surge vessel failure
Dear Tom: there is a request to study the follwing criteria for possible surge scenarios; The minimum and maximum surge pressure shall be calculated reflecting the most critical unscheduled events as listed below: Power failure of pumping station (trip of all pumps) Unscheduled closure of control valves Unscheduled closure of isolation valves In addition, operational load cases as listed below shall be investigated to allow definition of the sequences for flow increase / decrease, etc.: Startup of the system Shut down of the system Surge vessel failure it is not defined what is the surge failure?
↧
Forum Post: criteria for surge analysis
Dear: kindly, it is required to study the follwing criteria for surge analysis in Sudia Arabia project; To verify the surge vessels volume, two relevant critical cases, as part of the transient analysis, shall be considered: 1)Pump power failure assuming that the air volume is -5% in combination with n=κ=1.4 (isentropic condition is most critical regarding minimum pressure along the pipeline).? for this requirement; i dont understand what exactly meant by the air volume is -5%, is it the air voulme in the vessel 5% of the total volume. in addition, what is the purpose for the -ve sign. furthermore, the n vaule = 1.4 is it for the exponent of the gas law? Pump power failure assuming that the air volume is considered to be +5% in combination with n=1.0, (isotherm condition is most critical regarding blow out of the surge vessel). for this requirement; i dont understand what exactly meant by the air volume is +5%, is it the air voulme in the vessel 5% of the total volume. in addition, what is the purpose for the +ve sign. many thanks
↧
↧
Forum Post: RE: Surge vessel failure
OK, so you are not looking at failure of a surge tank but controlling the effects of failures using a surge tank. It is not something we can quickly cover in a forum but there are many sources to help you. Start with the in-product help in HAMMER. Then work through the Quick Start lessons that come with HAMMER. We also have a lot of wikis that address specific issue in transient analysis. For you problem, you may want to start with communities.bentley.com/.../24920.initial-surge-or-transient-event-after-adding-a-surge-tank-to-a-model You may also want to check out this webinar. www.bentley.com/.../mitigating-risks-of-transients-using-water-hammer-analysis These will teach you the basics of running a transient analysis. To become really competent, you should take our training classes learn.bentley.com/.../ViewLearningPathDetails There is also a chapter on transient analysis in our book Advanced Water Distribution Modeling and Management store.bentley.com/.../9781934493014--Advanced-Water-Distribution-Modeling-and-Management With these sources, you should become an expert in transient analysis. Best wishes
↧
Forum Post: RE: SEWERGEMS FLOW DIVERSION
Hello Hamid, I only see the .STSW file in the zip you attached to your post. The hydraulic model data is stored in the .STSW.SQLITE file, so that will need to be included as well in order to open the model. See article below for sending a model file: Sharing Hydraulic Model Files on the Haestad Forum Based on the screenshot, I'm not quite clear on the problem. The flow in the two upstream pipes (45.6 + 5.8) is roughly equal to the flow in the two downstream pipes (29.4 + 22) Could you elaborate on the problem? Are you expecting more flow to go toward the left vs toward the bottom? Tailwater effects and slopes may have an impact there. Plus, you may need to look at a time a few hours into the simulation, after the pipes have filled. (sometimes results in the first hour or so is impacted by this) If you're seeing unstable results at a split, you may need to try a control structure on one or more of the downstream conduits or use the SWMM solver with a small routing step. More on this subject here: Modeling a flow split (diversion) in SewerGEMS or CivilStorm
↧
Forum Post: RE: SEWERGEMS FLOW DIVERSION
Thanks Jesse for your reply, As you can see I have added the sanitary flow and labeled th sanitary population for aech pipe as the clinet requsted. The model is just for existing dry weather, I hvae to chack it for existing wet weather ( means 5 L/s/ha infiltration) and get the surcharge level too. I wanted to go with the implicit option to software caculate the diversion automatically, but the thing is I am not able to bring the extreme load factor, means the flows are not the same. Please help me in this case.
↧
Forum Post: RE: SewerGEMS+ Extreme load factor+DIversion
Hamid, Extreme flow factors / peaking factors are a steady state concept, typically used for pipe sizing in sewers. The implicit solver solver provides you with an unsteady simulation. You could consider using the Implicit solver to construct the diversion rating table to use with the Convex solver, so you could then use it with the Extreme flow methods in steady state. You can read about how to do that in this article: Modeling a flow split (diversion) with the SewerCAD or StormCAD numerical solver Another option would be to consider using the Implicit solver with a multiplier applied to sanitary loads. You could use a new sanitary loading alternative with the scenario in question and global edit the loading information in the sanitary load control center.
↧
↧
Forum Post: RE: SewerGEMS+ Extreme load factor+DIversion
But If I go with option 2, I need to have the load distribution on MH-13 already to get the load multiplear.
↧
Forum Post: RE: SewerGEMS+ Extreme load factor+DIversion
Jesse, I just used implicit to get the rating curve table and set the calculation time to 1min. So, just select both four pipes in Mh-13, right click and went to Graph and chose Flow (first option) but seems that the incoming flow from time 0 to 0.4 hours is more! I will appreciate you if you could help me to develop the table. Best Regards, Hamid
↧
Forum Post: SCADA connect with excel
Hi! I want to add real-time SCADA signals, but I've got a problem. Due to strict security protocols of our company, I have no direct access to operational data. Although, I can generate reports ( .XLSX format), which are near real-time (considering the 10-15min hydraulic timesteps). I can see that, when I establish a SCADA signal connection to a .XLSX file, it is opened for good, so no external software can write that specific file until watercad is closed or scada signal is deleted. This behaviour prevents me to overwrite/update the .xls report that contains my signal data. Do you know any workaround for this issue? What I was thinking about (but not sure if it can resolve the issue): - create an access database - Link my excel sheet to the database - establish scada connect to the access database file Best regards, Attila BIBOK
↧
Forum Post: RE: SCADA connect with excel
Hi Attila, Even though I have been using Excel for 20 years I would still not call myself an expert, but my feeling is that Excel doesn't really support concurrent access all that well. The problem with SCADA signals is that we can't really tell when they will need to open the SCADA connection, thus cannot guarantee any particular window where the connection will be closed to allow another user to update data. What you describe as a potential work around should work because Access allows concurrent access to data, but if you try it and run into any issues, be sure to write back and let us know. We are committed to help users establish robust work flows around these kinds of use cases. Kind Regards, Wayne.
↧
↧
Forum Post: RE: SCADA connect with excel
Hi Wayne, Thank you for your answer. I'm going to look into the aforementioned workaround. Best regards,
↧
Forum Post: RE: criteria for surge analysis
Hello Sawsan, Re: "what exactly meant by the air volume is -5%" If it is referring to a hydropneumatic tank, maybe it means that you should simulate the tank with 5% less air volume than normal, but you'd need to know what that baseline normal air volume is. It may be best to ask the reviewing agency (or whomever provided the requirements) for clarification. Re: " the n vaule = 1.4 is it for the exponent of the gas law? " Yes, that seems to be referring to the exponent in the gas law. For a transient analysis in HAMMER, it is hard-coded as 1.4 for air valve calculations, but can be changed for hydropneumatic tank calculations - see "gas law exponent" property for a hydropneumatic tank node. More on this can be found in this article: Modeling Reference - Hydropneumatic Tanks Re: " what exactly meant by the air volume is +5% " My comment on this one is the same as -5% - I would suggest confirming with whomever established the requirements. Maybe in this case it means you should simulate the initial gas volume 5% greater than normal.
↧
Forum Post: RE: Surge vessel failure
Surge vessel" could refer to either the surge tank node element which is open to the atmosphere, or the hydropneumatic tank element which uses pressurized gas to attain a hydraulic grade much higher than the physical top of the tank. You can read a lot more about the latter in this article: Modeling Reference - Hydropneumatic Tanks If by "surge vessel failure" you mean that you need to simulate what happens if something breaks in the tank, then you'll need to consider exactly what will physical happen and think about the hydraulic impact. As with your other post, I would suggest checking with whomever made the requirement for clarification. The requirement may be to check what happens if the tank is essentially not functioning at all, which would mean setting up a scenario in HAMMER with the surge tank inactive (is active = false) or a valve next to it fixed in the closed position.
↧