SWMM-USERS Digest - 21 Dec 2009 to 22 Dec 2009 (#2009-140)

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Dec 23, 2009, 12:00:11 AM12/23/09

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There are 10 messages totalling 929 lines in this issue.

Topics of the day:

1. Conduit under tidal influence (3)
2. SWMM input files inadvertenly hidden from Windows
3. SWMM input files inadvertenly hidden from Windows -- follow up
4. Flow Instability in pipes.
5. Multiple Box Culvert Inlet Outlet losses (3)
6. SWMM input files inadvertently hidden from Windows

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Date: Tue, 22 Dec 2009 01:46:24 -0700
From: Robert Dickinson <Robert.E....@US.MWHGLOBAL.COM>
Subject: Re: Conduit under tidal influence

Hi Francisco,

A few suggestions:

1. Use a Hot Restart File to control any initial condition instabilities in your HGL,
2. You can use local head losses for entrance, average and exit losses during pressure flow and they will be calculated automatically based on the equation K*v^2/(2g) where K is your entrance, exit or average loss coefficient,
3. You can use the BOTH option and the variable time step to help control initial condition instabilities, or use a smaller time step during the simulation.

I hope this helps.

Best and Kind Regards,
Robert E Dickinson
Technical Engineering Specialist
MWH Soft, Inc
9340 Pontiac Drive Tel: 813-712-0664
Tampa, Florida, 33626 Alt: 813-494-2919
USA
robert.d...@mwhsoft.com
www.mwhsoft.com

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of Francisco Araujo
Sent: Monday, December 21, 2009 1:59 PM
To: SWMM-...@listserv.uoguelph.ca
Subject: [SWMM-USERS] Conduit under tidal influence

Hello all,
I'm modeling a stormwater conduit that's under tidal influence. I just wanted to test the worst possible condition so I set a fixed type tide at 2 meters at the outfall with no flap gate, and inserted 3 constant flows in 3 different nodes, adding up to 6.03 CMS. The outfall is completely "drowned": IE=-1.69, square conduit with 2 meters side.
The simulation ran well, and I had a continuity error 0.05%.
I noticed some initial instability in the early moments of the simulation with the HGL peaking causing some unexpected floods in upstream nodes, and then the HGL stabilized to the expected level. Then I tried a different approach, releasing the flows 15 min after the start of the simulation in order to allow for the conduit to fill with tidal water, before it had to handle the flows. I noticed some peaks in the HGL when the conduit was filling, causing floods, well over the 2 meters of set tide, and the flows hadn't even "kicked in".
Basically I'm having difficulty interpreting the results in the early moments of simulation. Are the peaks caused by actual hydraulic effects? Should I neglect these early peaks and focus on the results of the simulation, after the HGL has stabilized (asking for a report only on later stages of the simulation)?
On the other hand, is it possible to introduce local head losses in SWMM, such as curves, once I'm working with (slightly) pressurized flow? Does SWMM calculate them automatically?
I hope my questions are clear enough.
Thanks in advance,
Best regards,
Francisco Araujo

------------------------------

Date: Tue, 22 Dec 2009 08:17:16 -0600
From: Gene Rovak <gro...@HORNERSHIFRIN.COM>
Subject: SWMM input files inadvertenly hidden from Windows

I encountered an unusual problem recently and wonder if someone else has
dealt with it.

Using SWMM on a Vista-equipped laptop, I went to transfer recently created
input files to a flashdrive but did not see the files when using Windows
Explorer (or [start] / [computer]). This began last month; earlier files are
visible and available to move using Windows.

As long as I remain within SWMM, there is no problem, but emailing or
transferring my recent SWMM files directly through Windows without SWMM has
become impossible on this particular computer. It's not terribly difficult
to work around, but requires accessing the file through SWMM and then using
[save as] to place it somewhere else. I.e. not impossible, but it is an
irritant have to start SWMM just to be able to move them.

Since they're not accessible through Windows, I can't even look to see the
file attributes (e.g. 'hidden' or other restriction). But I wondered if
there is an unknown (to me) SWMM setting that might have set the files to
hidden.

Gene L. Rovak, P.E., CFM
Horner & Shifrin, Inc.

------------------------------

Date: Tue, 22 Dec 2009 08:22:47 -0600
From: Gene Rovak <gro...@HORNERSHIFRIN.COM>
Subject: Re: SWMM input files inadvertenly hidden from Windows -- follow up

One thing to add. Even within SWMM, using the file open icon to bring up the
active directory that shows the needed files, and right-clicking a
particular file to "open with" Wordpad results in message to the effect of
"Windows cannot find this file ."

------------------------------------------

I encountered an unusual problem recently and wonder if someone else has
dealt with it.

Gene L. Rovak, P.E., CFM
Horner & Shifrin, Inc.

------------------------------

Date: Tue, 22 Dec 2009 09:22:31 -0500
From: Sheila Reeves <sre...@RKK.COM>
Subject: Re: Flow Instability in pipes.

From: Sheila Reeves [mailto:sre...@rkk.com]
Sent: Tuesday, December 22, 2009 9:21 AM
To: 'SWMM-USERS'
Subject: Flow Instability in pipes.

I am having some issues with flow instability in some pipes of particular
interest to my study. How can I go about resolving flow instabilities
within pipes? The overall model continuity error is -0.005. The routing
timestep is set to 1 sec. I was reading in the Users Guide to PCSWMM on pg
190 and it was saying that numerical instabilities under Dynamic Wave flow
routing can be reduced by

1) Reducing the routing time step - this has already been done in my
model as it is down to 1 sec

2) Utilizing the variable time step option with a smaller time step
factor - I am using this tool but not sure how sensitive this is. I have
tried it at 100% and 75% and get similar results

3) Selecting to ignore the inertial terms of the momentum equation -
have not done this as I don't understand the ramifications of doing this. I
currently have them dampened. I tried this but it did not help the
instability.

4) Selecting the option to lengthen short conduits -I have conduit
lengthening timestep of 2 sec but have also tried it at 4, 6, and 10 but it
did not help the instability.I am playing with the conduit lengthening tool
to help make my model more stable. The manual says to use 0 for no
lengthening, but it does not specify a typical or max value. I would like
to know what values are considered low, moderate, or high to get a sense for
how sensitive the tool is.

OI have also tried making the nodes in the area of this instability a
storage node that is 5 ft in diameter to simulate a manhole. but this didn't
help either.

AAny suggestions would be very much welcomed!

Sheila

"RK&K" and "RK&K Engineers" are registered trade names of Rummel, Klepper & Kahl, LLP, a Maryland
limited liability partnership. This message contains confidential information intended only for
the person or persons named above. If you have received this message in error, please immediately
notify the sender by return email and delete the message. Thank you.

------------------------------

Date: Tue, 22 Dec 2009 10:53:33 -0500
From: Bill James <bi...@COMPUTATIONALHYDRAULICS.COM>
Subject: Re: Multiple Box Culvert Inlet Outlet losses

See also:
"Minor Loss Coefficients for Storm Drain Modeling with SWMM" at

http://www.computationalhydraulics.com/Publications/Papers/PapersForPurchase
Info.asp?paperid=R225-23&index=0&ret=filter=search%2Bq=coefficients&rethint=
search

-Bill James

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of
Heineman, Mitchell
Sent: Monday, December 21, 2009 8:55 PM
To: SWMM-...@listserv.uoguelph.ca
Subject: Re: [SWMM-USERS] Multiple Box Culvert Inlet Outlet losses

Kuhan - I typically use US Highway Administration Hydraulic Engineering
Circular No. 22, URBAN DRAINAGE DESIGN MANUAL to obtain values of this
sort. Table 7-5b. Coefficients for Culverts; Outlet Control, Full or
Partly Full should have what you're looking for.

This, various other helpful documents, on-line calculators, etc for SWMM
modeling are referenced at www.dynsystem.com/netstorm/cdmuswmm.htm

Mitch Heineman, P.E., D. WRE, BCEE
Associate | Collector Systems and Surface Water Subdiscipline Leader
CDM
50 Hampshire Street
Cambridge MA 02139

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of
Kuhan Kuhanesan
Sent: Monday, December 21, 2009 8:27 PM
To: SWMM-...@listserv.uoguelph.ca
Subject: [SWMM-USERS] Multiple Box Culvert Inlet Outlet losses

Hi,

In SWMM, I am modelling a culvert crossing a small creek consisting of
five large box culverts (RCBCs) each 3.3m wide and 1.8m depth. What
are the best values for the inlet and outlet loss factors to be used to
model these multiple box culverts? Any references please?

Thanks

Regards

Kuhan Kuhanesan
Drainage Engineer

------------------------------

Date: Tue, 22 Dec 2009 09:10:55 -0700
From: Robert Dickinson <Robert.E....@US.MWHGLOBAL.COM>
Subject: Re: Conduit under tidal influence

Hi Franciso,

I should have been more explicit in my recommendation of a hot start file. In your case since the backwater influence from your non tide gate outfall is so important you need to make a hot start file based solely on the tidal boundary condition without any inflows and then use this hot start file in another model run with the inflows active in the model. You flows at the beginning of the simulation will then be stable (in reality the flows you were seeing were just the flow coming into the network from the boundary condition). Additionally, since reverse flow is so important in your model you should use the KEEP option in dynamic flow so the program uses the full St. Venant equation to calculate the flows.

Best and Kind Regards,
Robert Dickinson
SW/WW Technical Engineering Specialist
MWH Soft, Inc
9340 Pontiac Drive Tel: 813-712-0664
Tampa, Florida, 33626 Alt: 813-494-2919
USA
robert.d...@mwhsoft.com
www.mwhsoft.com

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of Robert Dickinson
Sent: Tuesday, December 22, 2009 3:46 AM
To: SWMM-...@listserv.uoguelph.ca
Subject: Re: [SWMM-USERS] Conduit under tidal influence

Hi Francisco,

A few suggestions:

I hope this helps.

------------------------------

Date: Tue, 22 Dec 2009 09:35:00 -0700
From: Robert Dickinson <Robert.E....@US.MWHGLOBAL.COM>
Subject: Re: SWMM input files inadvertently hidden from Windows

Hi Gene,

I was able to duplicate this by making a file hidden using Vista properties. I then could reopen it using SWMM 5 but it would be invisible and not usable using Windows Explorer. However, if you go to Vista's Folder Options and tell it to view hidden files then you can copy and paste the hidden files. There is no feature in SWMM 5 to make the files hidden. It may have been your flash drive software that made the files hidden originally - just a guess.

Best and Kind Regards,
Robert Dickinson
SW/WW Technical Engineering Specialist
MWH Soft, Inc
9340 Pontiac Drive Tel: 813-712-0664
Tampa, Florida, 33626 Alt: 813-494-2919
USA

robert.d...@mwhsoft.com
www.mwhsoft.com

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of Gene Rovak
Sent: Tuesday, December 22, 2009 9:17 AM
To: SWMM-...@listserv.uoguelph.ca
Subject: [SWMM-USERS] SWMM input files inadvertenly hidden from Windows

I encountered an unusual problem recently and wonder if someone else has
dealt with it.

Gene L. Rovak, P.E., CFM
Horner & Shifrin, Inc.

------------------------------

Date: Tue, 22 Dec 2009 17:27:07 +0000
From: Francisco Araujo <f...@COBA.PT>
Subject: Re: Conduit under tidal influence

Hi Robert,
You were explicit enough, I assure you. I was going to send you an e-mail to put you up to date on how things were going.
So here's how it stands:
You told me you ran the simulation without external flows for 22 hours in order to get a 0 cms flow from the tide. I can't seem to get a 0 flow, and I simulated it for 3 months!! After 24 hours I had a flow of a bit less than 0.03 cms. I took that as an acceptable value and created the hotstart file.
Then I used that hotstart file in the model with the external flows. It seems to be working much better.
I was studying the values from the Status Report and I found some things I'm having difficulty to interpret, though:
I'm getting some floods in upstream nodes - where the external flows enter - with duration under a minute at around 12 minutes of simulation. This is strange because the time table I constructed for each external flow only has a non-zero value at 15 min. The last zero value was at 10 min. It could make sense if SWMM does a linear increase of flow from 0 at 10 minutes to the maximum flow at 15 min. Is it the case?
Another strange value I'm getting is that the maximum flow on conduit 2 is at 12:00 and in the remaining conduits is at 00:15, when the flows "kick in". I can't find a logical answer for that.
I'm using the Keep Inertial Terms option now. I had a continuity error of 0.004%.
I really thank you for your help on this issue Robert, you've been very kind.
Warmest regards,
Francisco

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of Robert Dickinson
Sent: ter�a-feira, 22 de Dezembro de 2009 16:11
To: SWMM-...@listserv.uoguelph.ca
Subject: [?? Probable Spam] Re: [SWMM-USERS] Conduit under tidal influence

Hi Franciso,

Hi Francisco,

A few suggestions:

I hope this helps.

------------------------------

Date: Wed, 23 Dec 2009 11:46:45 +1100
From: Kuhan Kuhanesan <Kuhan.K...@D2G.COM.AU>
Subject: Re: Multiple Box Culvert Inlet Outlet losses

Hi,

Thanks for your suggestions. But, the problem is little more complicated
with the multi-cell box culvert, as the cells have varying invert
elevations, and also utilise precast link slabs. As such the vertical
walls also vary in thicknesses.

The invert of the two centre barrels 3300W x 2400H match the invert of
the creek and the other three barrels 3300W x 1800H are elevated 600mm
above the creek invert. The wing walls are located at the outer barrels.

In SWMM modelling, the five barrels are divided into two sets of box
culverts with standard inlet and outlet energy loss coefficients of 0.5
and 1.0 respectively.

What is the energy loss coefficient for the lower barrels and higher
barrels? We would prefer not to use 0.5 and 1.0 for all barrels, as the
flow patterns differ for each barrel. I think by using 0.5 and 1.0 for
all barrels, we may be over-estimating upstream afflux.

Comments are welcome.

Kuhan Kuhanesan
Drainage Engineer

P 07 3280 9395
F 07 3280 9111
E Kuhan.K...@d2g.com.au

Chalk Street, Redbank Q 4301
PO BOX 505, Booval Business Centre Q 4304
Safe Work, Safe Travel, Safely Home
lThink before you print, embrace the green office l
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-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of
Bill James
Sent: Wednesday, December 23, 2009 1:54 AM
To: SWMM-...@listserv.uoguelph.ca
Subject: Re: [SWMM-USERS] Multiple Box Culvert Inlet Outlet losses

See also:
"Minor Loss Coefficients for Storm Drain Modeling with SWMM" at

http://www.computationalhydraulics.com/Publications/Papers/PapersForPurc
hase
Info.asp?paperid=R225-23&index=0&ret=filter=search%2Bq=coefficients&reth
int=
search

-Bill James

This, various other helpful documents, on-line calculators, etc for SWMM
modeling are referenced at www.dynsystem.com/netstorm/cdmuswmm.htm

Mitch Heineman, P.E., D. WRE, BCEE
Associate | Collector Systems and Surface Water Subdiscipline Leader
CDM
50 Hampshire Street
Cambridge MA 02139

Hi,

Thanks

Regards

Kuhan Kuhanesan
Drainage Engineer

------------------------------

Date: Tue, 22 Dec 2009 20:29:10 -0800
From: Neil Jordan <NJo...@EXPONENT.COM>
Subject: Re: Multiple Box Culvert Inlet Outlet losses

Non-prismatic hydraulically complex structures can sometimes be modeled
outside SWMM, then converted to an equivalent structure that can be
modeled inside. Suggest HEC-RAS open channel with "lid" function to
provide the top of the structure.

Neil M. Jordan, P.E.

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@listserv.uoguelph.ca] On Behalf Of
Kuhan Kuhanesan
Sent: Tuesday, December 22, 2009 4:47 PM
To: SWMM-...@listserv.uoguelph.ca
Subject: Re: [SWMM-USERS] Multiple Box Culvert Inlet Outlet losses

Hi,

In SWMM modelling, the five barrels are divided into two sets of box
culverts with standard inlet and outlet energy loss coefficients of 0.5
and 1.0 respectively.

Comments are welcome.

Kuhan Kuhanesan
Drainage Engineer

P 07 3280 9395
F 07 3280 9111
E Kuhan.K...@d2g.com.au

See also:
"Minor Loss Coefficients for Storm Drain Modeling with SWMM" at

http://www.computationalhydraulics.com/Publications/Papers/PapersForPurc
hase
Info.asp?paperid=R225-23&index=0&ret=filter=search%2Bq=coefficients&reth
int=
search

-Bill James

This, various other helpful documents, on-line calculators, etc for SWMM
modeling are referenced at www.dynsystem.com/netstorm/cdmuswmm.htm

Mitch Heineman, P.E., D. WRE, BCEE
Associate | Collector Systems and Surface Water Subdiscipline Leader
CDM
50 Hampshire Street
Cambridge MA 02139

Hi,

Thanks

Regards

Kuhan Kuhanesan
Drainage Engineer

------------------------------

End of SWMM-USERS Digest - 21 Dec 2009 to 22 Dec 2009 (#2009-140)
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