Method of Characteristics or Bond Graph
Method of Characteristics or Bond Graph
(OP)
Hi all
I am looking to purchase a hydraulics surge analysis software for my company, and have narrowed it down to Flowmaster and Amesim. One uses Method of Characteristcs and the other Bond Graph method... and of course both say their method is better :)
Does anyone know the advantages and disadvantages of each? and any feedback on the software mentioned
Thank you in advance
Simba
I am looking to purchase a hydraulics surge analysis software for my company, and have narrowed it down to Flowmaster and Amesim. One uses Method of Characteristcs and the other Bond Graph method... and of course both say their method is better :)
Does anyone know the advantages and disadvantages of each? and any feedback on the software mentioned
Thank you in advance
Simba





RE: Method of Characteristics or Bond Graph
For example, Winsys, the process simulator can do pipeline analysis, but IMO does not offer ease and convenience to pipeline designers in entering data and building typical flow models for pipeline and the liquids handling facilities. So for work light on process and heavy on liquid handling facilities, I would most definately and totally go with Flow-*whatever*. For work involving little liquid handling relative to the process load, great use WinSim. I don't have experience with your alternate Amesim, but it looks heavy on the systems modeling capability and light on the convenience of use for specific liquid handling systems. Its not to say it can't do it and do it well, but that's not my point. My point is how easily and efficiently the package will allow you to do your job of analysis, interpretation and flexibility of presenting the results. I think its probably going to be Flowmaster.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Method of Characteristics or Bond Graph
Flowmaster does seem the more user friendly. But if Bond graph method is a better way to modelling transients in systems then i think accuracy of results overides any easy use benefits.
Can you advise me on the main benefits of each method?
Thanks again
RE: Method of Characteristics or Bond Graph
I2I
RE: Method of Characteristics or Bond Graph
validation against experimental results.
what are the limitations of Method of characteristcs and similiarly Bond Graphs? things like variable timestep and modelling discontinuities are some i have researched but other issues would be greatly appreciated
Thank you
RE: Method of Characteristics or Bond Graph
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Method of Characteristics or Bond Graph
I agree with you. Even those with some experience misinterpret results. With compressible flow, I have found many individuals using moc programs in which the individual and program cannot calculuate correct results.
ie, sudden rupture of a high pressure pipe line with compressible flow. You'd be supprised at answers for the instantenous pressure at pipe exit.
Regards
RE: Method of Characteristics or Bond Graph
I2I
RE: Method of Characteristics or Bond Graph
The point of purchasing the software is to reduce the number of experiments in the future, but we need to trust the results and comparing them to our past experimental data for validation is one way of building our confidence in any software.
Cheers
RE: Method of Characteristics or Bond Graph
Because the experimental data is much more expensive than a stack of computer runs. If you even get to run transient tests, you are lucky; more likely you will calibrate your current job's computer simulations based upon either lab-generated experiments (for which you have a lot of data but the case modelled is rather simple, and there aren't very many of these cases to model, so..), or field failures (for which you will have limited data, many assumptions, etc.).
FWIW, I have no idea what the "Bond Graph" method is, but would agree with BigInch that it probably works just fine, and the choice of software is more about how easily it can be used for your anticipated work situation. The Method of Characteristics is well known, and described in a number of gas- and fluid-dynamics texts. To quote from a book on my shelf, Fluid Transients in Systems, Wylie, B. and Streeter, V., Prentice-Hall, 1993:
"For rapid transients in liquid pipeline systems the mehod of characteristics is generally considered to be the numerical method by which others may be judged for accuracy and efficiency. Other methods are available and in certain situations there are valid reasons to consider their use."
Personally, my fluid dynamics software consists of several dozen spreadsheets, some ancient fortran code that I occasionally dust off, some compiled codes that I can dust off if I ever need to, and some 20+ years of experience that lets me (usually) predict on the back of an envelope what the computer eventually tells me. Then we go try it in the real world, and Ma Nature grades my work.
RE: Method of Characteristics or Bond Graph
The MOC method of simulation, without cavitation, is a reliable method and accurate solution. However after cavitation occurs the reliability of predictions deceases significantly.
The discrete cavity model is offer by AFT's Impulse (WYlie et all pgs 66-67) 1993. This does have its drawbacks as significant non physical pressure spikes may occur as the bubbles collapse. Significant engineering judgement is then required to interpret results.
Geoff