Stochastic analysis of a piping system... 2

[rtk350]

I need to complete a stochastic analysis of a rural water pipeline and was wondering if anyone could point me in the direction of a software package that could do that.

I've currently got a WaterCAD model, but realize it would take a lot of work to set up the parameters and settings to create something resembling a stochastic analysis.

Any advice would be appreciated.

Ryan

 

[RWF7437]

What is a stochastic analysis of a rural water pipe and why would anyone do one ?

 

[rtk350]

Definition: An analysis related to a process involving a randomly determined sequence of observations, each of which is considered as a sample of one element from a probability distribution.

Basically a simulation of users randomly turning their taps on and off to determine the effects on flows, pressures, etc.

 

[RWF7437]

and why would anyone do one ?

 

[rtk350]

With such a large system we want to ensure that a ‘true’ simulation doesn’t have any negative impacts on the system as a whole; particularly in terms of water age, chlorine residuals and pipe type/class/diameter.

 

[RWF7437]

I’ll try to give you a long answer because I don’t have time for a short one.

Unless your “large system” is very unusual a stochastic analysis is unlikely to be very useful. Here are a few of the reasons:

1. In most public water systems, demands are NOT random but are somewhat predictable. Domestic demands are most often diurnal with peak flows occurring early in the morning and later around supper time. At night, these flows often drop to near zero.
2. Industrial demand will also follow a pattern closely related to each industry’s workshifts or similar scheduled operations.
3. Fireflows are usually the largest system demands. While fires may be random events, the critical locations of fire demands may be predicted based on Code required flow and such factors as whether the demand can occur at the top of a hill or alongside an undersized main where pressure and capacity are low.
4. Water quality analyses can be done using these same demand patterns, rather than assuming a completely random series of events.
5. If you don’t have demand patterns for your system you can either develop them from a pressure survey or you can infer them from similar nearby systems which do have such records.
6. Your time and effort are probably better spent calibrating your system model rather than attempting a random sampling approach which may be of academic interest....unless this IS homework, of course.

 

[bimr]

http://www.ewisa.co.za/literature/files/079.pdf

http://library.wrds.uwyo.edu/wrp/85-38/85-38.pdf

 

[BigInch]

If you build it, they will come.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[quark]

I'll try to give you a long answer because I don't have time for a short one.

That beats my previous (all time) favorite posts.