Results vary depending on which tab is current

[jfalkowski]

Hydraflow Storm Sewers Extension 2008 has been driving me nuts for the past couple of days. I finally realized what it was doing but I am not sure why. Try this on any of your 2008 files and see if you have similar results.

Depending on which tab I am on when I run a system I get varying results. Run an analysis w/design, starting the HGL at normal with the ‘plan’ tab current and view your DOT results. Pay particular attention to the Total Flow, System Tc and Intensity at the end line.

Make no changes to the system but make your ‘Pipes’ tab current. Re-run the system again using analysis w/design, starting HGL at normal and see if your Q, Tc, and Intensity changed.

The Plan tab results produce higher flow rates due to a shorter Tc and slightly higher intensity.
The Pipes tab produces lower flow rates with a higher Tc and lower intensity.

Can someone explain this one to me?

Jon

[Anonymous]

This is a defect but belive will be fixed on the next release...

Traditionally, when computing flows for the Rational Method, we assume a pipe velocity in order to compute Tc so that we can compute Q. We have to assume a velocity at this point because we don’t yet know the flow depth. Hydraflow will, however, first assume a velocity equal to the Design Velocity as set in the Codes, say 3 ft/s. Then it computes the Q. Next is uses that Q to better define a pipe velocity. A bit more accurate than usual.

When computing from the Plan View Tab and using the Interactive Feature, the program uses this more sophisticated method. Otherwise, it still assumes the Design Velocity. This difference in velocity is affecting the pipe travel time, Tc and thus Q. This difference is extremely minor but can be more significant on larger systems. The EMS method is best for those.

[jfalkowski]

I am using the 08 version. I assume it was not fixed in 09 either. Are you referring to release 2010 and where are you getting this information? Thanks,

Jon

[Matt.Anderson]

I think 08 and 09 - Civil 3d versions are the same Hydraflow release calculations.

[kspear]

When going to Help>About in both 2008 & 2009 extensions of Storm sewers, they are different versions, slightly. I think 2008 was v 6.057 and 2009 is v6.066. I guess that subtle change makes the difference in the calculations. 🙂

I wish they would notate changes / improvement details for each version somewhere. That might resolve some of this confusion.

[kspear]

Terry, is the resolution in 2009 or 2010?

[Matt.Anderson]

Kevin -

The defect is that when using Design w/Interactive from any tab OTHER than the PLAN view - Design Velocity is assumed.

The work around would be to Design from the Plan View Tab, and finish up the design with EMS.

I would assume the resolution would be 2010.

Matthew Anderson, PE


> {quote:title=kspear wrote:}{quote}Terry, is the resolution in 2009 or 2010? This is a defect but belive will be fixed on the next release... Traditionally, when computing flows for the Rational Method, we assume a pipe velocity in order to compute Tc so that we can compute Q. We have to assume a velocity at this point because we don't yet know the flow depth. Hydraflow will, however, first assume a velocity equal to the Design Velocity as set in the Codes, say 3 ft/s. Then it computes the Q. Next is uses that Q to better define a pipe velocity. A bit more accurate than usual. When computing from the Plan View Tab and using the Interactive Feature, the program uses this more sophisticated method. Otherwise, it still assumes the Design Velocity. This difference in velocity is affecting the pipe travel time, Tc and thus Q. This difference is extremely minor but can be more significant on larger systems. The EMS method is best for those.