help--how to build stock and flow diagram with pipeline dela

accesschen · Post by **accesschen** » Thu Sep 24, 2009 5:17 am

hi,all friends.
how to build stock and flow diagram with pipeline delay.

best regards.

Post by **Administrator** » Thu Sep 24, 2009 7:40 am

Have you looked at the DELAY FIXED and DELAY MATERIAL functions?

accesschen · Post by **accesschen** » Thu Sep 24, 2009 8:41 am

pls show me an illustration of picuture

accesschen · Post by **accesschen** » Thu Sep 24, 2009 8:44 am

how can i draw a rate variable with two valves?

Post by **Administrator** » Thu Sep 24, 2009 8:57 am

Connect the two with a normal arrow, then right click on the little circle on the arrow. You can now change the arrow appearance.

Is this what you want to do?

Tony.

accesschen · Post by **accesschen** » Thu Sep 24, 2009 9:38 am

I do it as follows:
first, draw two rate variables;
next, delete the right part of one rate variable and the left part of the other rate variable, thus only two valves are left.
third, use an arrow links the two valves, and change the type of the arrow to be a bold line.

but a question occurs, the bold line linked between the two valves can be curved, but a sample I saw from http://www.public.asu.edu/~kirkwood/sysdyn/SDRes.htm doesn't show this feature. I don't know why it shows this difference. Could you tell me it in detail?

[Edited on 9-24-2009 by accesschen]

[Edited on 9-24-2009 by accesschen]

bob@vensim.com · Post by **bob@vensim.com** » Thu Sep 24, 2009 10:52 am

A cascaded delay should appear exactly as the molecule for the same - see below. If you want to use discrete delays instead of the normal exponential drain on each intervening level then there needs to be an arrow from flowingIn to movingToLevel2 and so on with the equation something like

movingToLevel2 = DELAY FIXED(flowingIn, delay time,flowingIn)

You might study the molecules for more examples, though none of these use discrete delays.

accesschen · Post by **accesschen** » Thu Sep 24, 2009 12:40 pm

thank you for your kindness.
I only wonder how to draw this type of two linked valves .
the attachment model can be seen from the website http://www.public.asu.edu/~kirkwood/sys ... ork4-1.mdl

[Edited on 9-24-2009 by accesschen]

bob@vensim.com · Post by **bob@vensim.com** » Fri Sep 25, 2009 10:41 am

Tony already told you how to do this. Use the Delete tool to remove the unneeded clouds then the rate tool to connect the two valves. After that right click on the arrow head and uncheck the arrowhead option.