Ventana software support forum

Dear Experts I have restructured the model to ensure unit consistency, although some of the equations where valid, i had to re-write them to get them consistent units.However, I still keep receiving the floating point error message when trying to run the simulation. Am I over looking something? What...

Originally posted by grockson Originally posted by grockson Dear Experts, I have attached the governing equations responsible for the differential equations( earlier quote). The Floating error computing still persist after the unit check. The power functions posses a change to, how do i represent t...

[quote] Originally posted by grockson Dear Experts, I have attached the governing equations responsible for the differential equations. The Floating error computing still persist after the unit check. The power functions posses a change to, how do i represent them well. The equation are standardized...

Dear Experts,

Could you assist me to manage the above subject in my model.

Hope to hear from you soon, with you suggestions and comments.

Sincerely,

George Rockson

Dear Bob,

What I am currently using is a PLE, I have recommended the Software for purchase by my university, but this could take some time ( Typical of Africa). I will continue to review the equations, option and fine-tune the equation

Dear Bob,

Who do I locate this; switching to Runge-Kutta 4 (cause I am a beginner)? Hope to here from you.

Dear Bob,

You are right in this respect, and that is what I have been doing. Unfortunately, the values keep exploding in both the negative and positive directions. I will keep trying.

Thanks

[Edited on 5-16-2008 by grockson]

Monod type differenctial equations Dear Bob, I could assume that CO2 should also have a d/dt. how do i represent such a flow system. Also CO2 feeds equation 7 in the attached document which explains the conceptual model. I which to keep temperature(T) constant for the time being. Even without the CO...

Hi Bob, Were the equations enough to explain my goal?

Hope to hear from you.

George

I have detailed the equation as mush as possible. The temperature terms have been left out to make it look simple, although temperature is affecting the microbial growth rates. The units have also been attached although, i tried to use a simpler unit system. Home it meet you interest to discuss or m...

Dear all, Could any one ( Bob) assist with this workbench

I having a problem with unit check on a differential equation i am trying to test.
Attached is the workbench for the model

I having a problem with unit check on a differential equation i am trying to test.
How do I post the diagram for you to see what I have been about.

Thanks you, I will pass this information
on.

Bod. What version of Vensim would you recommend for my University, especially for use by PhD and Graduate student and the area of Environmental and Agricultural Engineering.

Thanks

Thanks so much, I will work around it and keep in touch.

My Vensim PLE is geeting interesting (with some fun)

Bob, so how do i represent this in terms of level, rate, etc. I am doing my best to understand Vensim PLE application.

Dear Bob, I am a beginner in modelling, and I was introduced to VENSIM PLE by a friend at the University of Western Ontario. I am a grad student in Ghana. I have beed struggling with how to apply differential equation in this respect on a model. [dy(1)/dt]=a(1)*y(1) [dy(2)/dt]=a(2)*y(2)-b(2)*y(2) a,...

Originally posted by bob@vensim.com If a variable depends on other it has the equation a = f(b,c) The simulation of the model would give the trajectory a(t) - A partial differential equation has the form da/db = f1(a,b,c) db/dc = f2(a,b,c) and so on. For a lumbep system of differential eqautions (i...