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Document Type: FAQ Product(s): Bentley HAMMER Version(s): V8 XM Original Author: Jesse Dringoli, Bentley Technical Support Group
Document Type: FAQ
Product(s): Bentley HAMMER
Version(s): V8 XM
Original Author: Jesse Dringoli, Bentley Technical Support Group
Yes. HAMMER V8 XM uses the same file format as WaterGEMS/CAD V8 XM, so you can directly open the files. All 3 programs conveniently use a .wtg and .wtg.mdb file to store the model data.
HAMMER uses the Method Of Characteristics.
Typically, you should run a transient simulation for the maximum and minimum demand hours for each of the development conditions (network and demand points) under consideration.
No, currently they are not considered. If you need to study the effects of transient forces (X/Y/Z) on a pipe with vertexes, you should consider replacing the bends (vertexes) with junctions.
The transient results are viewed in the Transient Results Viewer, located under the Analysis menu. The amount of results included in here is determined by the report period, report points and "generate animation data" settings, under Analysis > Calculation Options > Transient calculation option
The starting conditions of the model before a transient occurs are defined in one of two ways. First, you can invoke the WaterGEMS steady state solver (Analysis > Compute initial conditions) to calculate them for you, based on the demands, boundary conditions and other element attributes. This is the same solver that Bentley WaterCAD and WaterGEMS use. The transient solver then uses the computed flows and hydraulic grades as the starting conditions.
Alternatively, you can define your own starting conditions (flow and head) by choosing "true" for the attribute called "specify initial conditions?" in the transient calculation options (Analysis > Calculation options.) When doing this, the transient solver will no longer use the head/flow computed by the "compute initial conditions", but instead will use the head and flow values that you must enter in, in the "transient (initial)" section of each element's properties. Note that if you want to slightly modify some computed initial conditions, you can copy them over to the user defined initial conditions fields first by using the "copy initial conditions" tool (under the Tools menu) and then alter them as you see fit.
First, enter a number for the "Report period" attribute of an element. This represents how often the results will be saved for. For example, a report period of '10' means that results will be shown at every 10 timesteps. Make sure text reports are enabled in the transient calculation options. Now, when you compute initial conditions, extended results will be displayed, under Report > Transient Analysis Reports > Transient Analysis Detailed Report. Scroll down to the bottom to see a table of data for the element(s) with a report period.
Follow the steps below. Note that this assume you are using Microsoft Office 2007 edition. The process may be different for other versions.
1) Copy/paste the text from the .rpt file pertaining to your particular graph into a separate .txt file in Notepad. This is the table of extended transient results seen at the bottom of the transient analysis detailed report.
2) Open Microsoft Excel and start a new spreadsheet (the process is likely different with older versions of Excel)
3) Click the "Data" tab, choose "From Text" and select your file.
4) Choose "Fixed width", then "next"
5) Set up the field widths so that the columns of data are separated appropriately
6) Set up a line graph with the appropriate columns (Time, plus whatever attribute you'd like to graph. For example, volume of air for a hydropneumatic tank)
The pressure reducing / pressure sustaining / flow control properties of these valves are only used during the initial conditions calculation. This is because HAMMER assumes that during the transient event, these valves cannot react quickly enough to the changes in flow/pressure. If you are running a long transient simulation and need to model the effects of these valves, you'll need to use an operating rule on the valve to close them.
No, the controls that you enter under Components > Controls only apply to the initial conditions calculation. To control elements during the transient simulation, you'll need to use configuration in the individual equipment (such as closure time for the check valve node) or operating rules (such as the pattern of time vs. relative closure for a valve).
These controls only apply to the initial conditions calculations (steady state or EPS), not the transient simulation. If you need to control things during the transient, you must use the options seen in the properties of the various transient elements. For example, an operating rule for a TCV valve or the time delay until shutdown for a pump.
The deviation mentioned here is based on a percentage, which you can see by the units, under analysis > transient timestep options. Basically, based on the time step, Hammer tries to have a wave be able to travel from one end of the pipe to the other end in even multiples of the time step. Therefore, Hammer will try to adjust the length of the pipe to allow this to happen. By default, if it has to adjust the length more than + or - 50% (the default option at the bottom right of the transient timestep options window), then you get that warning. Basically the best scenario is to have all your pipe lengths the same length, however, that is usually not possible. So you just have to get them close. You can also adjust the time step to be smaller and that usually helps. Or you could possibly ignore the warning if the results make sense and look correct to you - it`s your judgment. You can certainly make some adjustments, go back to the Timesteps, click the update button and see the new max/mean adjustment. You can also change the timestep as previously mentioned and check the new max/mean using the same update button as well as choose between adjusting wave speed or length. Typically this is just a trade-off between accuracy and run time. The smaller you make the timestep, the better the accuracy (less adjustment will need to be made), but the longer the transient run will take to complete.
For more information, see Bentley Technical Support KnowledgeBase.
First, run the Initial Condition analysis and record the velocity in the pipe downstream of the check valve. Let's assume it is 4 ft/second.
Next, run the transient simulation and open the Transient Results Viewer. Plot a time history graph of flow in the pipe downstream of the check valve and measure the time from when the pump turns off until the flow curve crosses the x-axis (i.e. when flow reaches zero). Let's assume it is 2 seconds.
So the deceleration of the water column is 4 ft/second / 2 seconds = 2 ft/s^2.
This is an average deceleration rate, which is typically what valve manufacturers provide.
The Transient Results Viewer displays transient results in graph form and also can animate hydraulic grade in a profile.
The "Paths (Profiles)" pulldown at the top allows you to select a profile (defined in the main user interface under View > Profiles) and then either plot or animate it. The "plot" will provide the minimum/maximum transient envelope. The "animate" button will allow you to see the hydraulic grade profile as it changes over time. This is useful to understand how certain transient inducing events affect the system as a whole. If the animate button is grayed out, make sure "generate animate data" is set to "true", in your transient calculation options. To reduce the amount of profiles available, go to View > Profiles, right click on the ones you'd like to omit from the transient results viewer and deselect "transient report path".
The "Time Histories" pulldown at the bottom of the Transient Results Viewer displays end points that are available to graph. The amount of endpoints listed are determined by the "report points" option in the transient calculation options. Note that transient simulation results are available at the ends of the pipes where they meet a node element. For example, the upstream side of a pipe or the downstream side of a pump. For time histories, you can plot the head, pressure, flow, air/vapor volume and force (if you've chosen to compute transient force.)
In general, you can right click on the frame/axis of the plotted profile, select "format data" and see the names of the various plotted lines in the dropdown.
For an animated profile, check the below diagram:
For a plotted head envelope:
Solid black line - physical elevations Dashed black line (or solid orange line if a pressure plot) - Initial conditions head Solid red line - maximum transient head Dashed blue line - Minimum transient head Red line at top - Max vapor/air volume Dashed yellow line - vapor pressure (as a reference)
Note: The Young's Modulus and Poisson's ratio are only necessary if you need to use the automatic wave speed calculator tool, under Tools > Wave Speed Calculator.
If you would like to create a new engineering library (xml file) instead of altering the default MaterialLibrary.xml, simply right click on "Material Libraries", choose "create library", choose a location to save the file, then repeat steps 2-4 above, replacing 'MaterialLibrary.xml' with the name of your library.
The "Elevation" represents the water surface elevation and the "Elevation (inlet/outlet invert)" represents the invert of the pipe that attaches the reservoir to the system. Pressure at the reservoir location is determined by the difference between these values.
Natively there is no direct way to do this with the Transient Results Viewer. However, you can do it using the below process. This is useful in cases where you'd like to compare transient profile/time series results between scenarios.
1) Open time history graph (or profile plot) number 1 2) Right click in the middle of the graph and choose Save As > HAMMER graph - save the .grp file somewhere 3) Close graph (or profile plot) number 1 and go to File > open and reopen it 4) Right click on the frame of the graph and choose "copy data" 5) Open graph (or profile plot) number 2, right click on the frame and choose "paste data (+)".
Note: you may have to adjust the Y axis scale if the pasted data doesn't fit in graph number 2.
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