New user, simple questions

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nesheim
Junior Member
Posts: 14
Joined: Mon Apr 30, 2018 12:12 pm
Vensim version: PLE

New user, simple questions

Post by nesheim »

I am new to Vensim and could use some help.

Lets say I have a part, call it bearing. It starts off with a 100% condition. I set a rate, call it wear. It starts off with 1 (0-100 min-max). Simulation steps are in weeks.
So far, simulating gives a linear slope of the bearing condition. From here on I get stuck:

I want to introduce a level, call it oil level. It starts off at 100, and is empty at 0. As this level goes down, I want the "wear" to increase exponentially. This should result in that the bearing condition no longer remains linear.

+ What does the "auxiliary" do? How does it work compared to constant or level.

Thanks
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Administrator
Super Administrator
Posts: 4573
Joined: Wed Mar 05, 2003 3:10 am

Re: New user, simple questions

Post by Administrator »

It might be better to take a step back and go through some of the tutorials.

http://www.public.asu.edu/~kirkwood/sysdyn/SDRes.htm
On this page you will find a really good Vensim PLE tutorial.
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391

Units are important!
http://www.bbc.co.uk/news/magazine-27509559
tomfid
Administrator
Posts: 3806
Joined: Wed May 24, 2006 4:54 am

Re: New user, simple questions

Post by tomfid »

wear rate = EXP(k*oil level) is not what you want, because it's increasing in oil level. You might try something like
wear rate = normal wear rate*EXP( wear sensitivity*(oil level - critical oil level) )
with wear sensitivity < 0.

Another alternative would be to use a lookup, like
wear rate = normal wear rate*effect of oil on wear( oil level/normal oil level )
nesheim
Junior Member
Posts: 14
Joined: Mon Apr 30, 2018 12:12 pm
Vensim version: PLE

Re: New user, simple questions

Post by nesheim »

it works, thanks guys.
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