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-   -   some very basic questions (http://www.cfd-online.com/Forums/fluent/38828-some-very-basic-questions.html)

bomario December 4, 2005 22:13

some very basic questions
 
i was using Fluent Flow Lab for the first time today for an assignment. I was modeling a pipe, 0.1 m diameter and 20 m long. There was a template already set up that had all the values in it that we were supposed to use. The assignment required changing the inlet velocity (using guess and check) to obtain values of Reynolds number ranging from 200 to 1000. Then create the mesh (meduim density), iterate it, and plot the Frictional function. This produces a plot showing the friction vs. x (distance on the pipe). Then compare the fully developed frictional function to the theoretical, f=64/R.

My answers for each of the Reynolds numbers were very close to the theoretical so i think i did it right.

My questions are: 1. Why do i have to close and restart flowlab each time i want to do a different reynolds number. If i just went back and changed my geometery, it would keep showing the old frictional plot and not generate a new one.

2. What do the (x/D) values in the "start" window mean? i left these as the default, but i'm not sure if i was supposed to change them.

3. What does iterate do? the tutorial i was given did not mention this function, but i had to do the iteration first to get the right answer.

4. Not exactly sure what fully developed means? Does this mean when the frictional value stops changing--thats what i think i means. Is there an exact point, or do you just go by looking at it?

THANKS



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