I have an issue with my Hydraulic Model.
I have analysed my model with two different approaches.
Used user-defined gutter-> Conventional-> Max Gutter depth 0
Used max gutter depth 0.06 m in this case(global edit in Catchbasin FlexTables)
Now the issue is, in second case it looks like the network is not capturing the full flow from the catchments. I checked the total flow from catchment contributing to a pipe and checked the flow in the pipe, they are not matching. In case 1 its matching.
I want to know if I had done a mistake. Please help me through this.
Case 1 Images:
Case 2 Images:
Check the capture efficiency of the catch basins in the second case. What is the inlet location you have set for the second case? Is the inlet "On Grade" or "In Sag"? If the inlet is "In Sag" it will capture 100% of the flow. However, it is also possible to have full capture with "On Grade" inlets. We would need to take a look at your model to see the results and identify if there is some data input problem.
Please share the model files (.stsw and .stsw.sqlite) for our testing. See the article below for details on sharing model files on the forum;
Sharing Hydraulic Model Files on the OpenFlows | Hydraulics & Hydrology Forum
Bentley Technical Support
I have uploaded the files for two cases. Please have a look
I have taken a look at the model files and I see that in both cases all of the flow is captured, but the ponded area that you have chosen to add above the rim is causing the inlet inflow to be attenuated in the case where the inlet type is set to Catalog Inlet. You can see this by graphing "Flow (total in)" along with "Flow (total out)" for the catchbasin.
I believe the reason why this does not happen when the inlet type is set to full capture is because in this case, the gutter is not considered, so the ponded area above the gutter does not come into play, and thus the catchment runoff enters directly into the catchbasin. (if overflow later occurs, the ponded area would be considered).
In the case where the inlet type is set to catalog inlet, gutter hydraulics are enabled, and the program considers the impact of the ponded area. Catchment runoff first enters the ponded area and then becomes attenuated as it enters the inlet, similar to pond hydraulics with outlet structures. I am discussing this internally with our developers to confirm that this is indeed expected behavior. In the meantime, please confirm if you intended to have a large ponded area above the inlet.
Jesse DringoliTechnical Support Manager, OpenFlows ProductsBentley Communities Site AdministratorBentley Systems, Inc.
I have changed the Ponded area at inlets to lower value(50m2) and the flow values are almost matching. But two new issues raised.
1. There is huge overflow loss in 10-Year Scenario and
2. The Hydraulic Profile is looking bad in few places of network. I have attached one image for your reference. Check the maximum HGL of first inlet.
I am unable to understand where it went wrong. Please help me through this.
This is the overflow from the catch basins. Due to less storage area (50 sqm) now, there is overflow at the catch-basins which is causing the high HGL values. Try to use the gutter element in parallel to your catch-basins to capture the overflow.
Basically what is happening is that once the storage area for your "In Sag" inlets is getting filled up; its overtopping with overflow and hence the high HGL values.
When increasing the storage area/Ponded area to higher value(say 500 m2) the overflow is decreasing but the inlets are not capturing the all the flow from catchment. This is the query actually I posted in this thread. Previously the Ponded area is around 1500m2. Upon Jesse Dringoli suggestion, I have reduced the ponded area to 50m2 and the Max HGL is increasing. You suggested to use gutter element. I have already defined gutter. Do you want me to draw the gutter in the entire network?
Are you using catalog inlets in this case? Can you provide an updated copy of the model? I've done some testing in a small example model and I'm currently discussing with our developers the general topic of how the ponded area option is handled in various situations with the SWMM solver.
Generally speaking models with excessive surcharging/overflow tend to be challenging for the numerical solver, requiring additional finesse to achieve stable results. I'd like to get a clear understanding of your current specific situation to make sure we can focus on that use case. If you're able to set up a small cut-down version of the model that demonstrates the issue, that would be ideal.
Yes, I am using Catalog inlet. I have trimmed the model with lesser number of Conduits. I have uploaded the new model in Bentley secure server. This time I have used Ponded area of 500 m2 for the inlets and 5000 for the Manholes. Still I have overflow losses in 10 Year Scenario. Also the total flow from the catchment is not entering into the system. Please look the images below. Also look at one of the profile. Max hgl is way above.
Hi Kartheek, thanks for providing the new, smaller model.
In the example case you highlighted with catchbasin P4-IN248-15, you are only comparing the peak flow values, which do not necessarily indicate loss of flow. As mentioned earlier, the introduction of the ponded area introduces attenuation (like a pond), flattening the peak but with the same volume. To see this, graph the catchment flow together with the catchbasin outflow:
For the example case you highlighted with Profile-1, that covers a different part of the network. If you graph hydraulic grade for one of the catchbasins such as P4-IN236-5 for example, you can see that the high HGL happens for brief periods of time due to what may instability (fine tuning of the calculation options may be necessary)
With that said, after discussing this with our development team, it was found that the combination of ponded area surface storage along with a catalog inlet, is not a valid combination and will lead to the unexpected overflow. You will need to select full capture in this case to see valid results for the in-sag inlet with ponded area. Note that in this case, if you have a gutter connected downstream, any overflow (from the subsurface network spilling out of the rim) will travel down the gutter. If you global edit the inlet type to catalog inlet in your smaller example model, you will no longer see overflow (lost to the system) and the high HGL you saw in that profile example will no longer occur.
If I use full capture inlet instead of Catalog inlet spread value is not populated (Its showing N/A). But the spread value is to be shown in the model as it is client requirement. Is there a way to get spread values when using Full Capture inlets and used Defined gutter?
For an in-sag inlet, the spread is calculated based on the weir or orifice equation using the dimensions of a catalog inlet, to find the depth and spread necessary to "push" all of the incoming approach flow into the opening. When the inlet type is set to full capture, this information is not available so the depth and spread are not calculated.
I will be discussing this further with our development team as I see that the SWMM solver has a requirement of using a surface storage method with an in-sag inlet. (yet this will cause overflow as mentioned). We'll get back to you as soon as possible.
Note that if you use the Implicit solver instead of the SWMM solver, you can use a catalog inlet in-sag without a surface storage method selected, and any overflow will go down the downstream gutter.