Hello, good morning. First of all, let me introduce myself. I am student who is currently conducting a thesis research on underwater flow simulation on submarines. I am quite new to FLUENT software. The establishment of this forum website provides some relieve to me as there is a channel for me to voice my problem regarding the utilization of this software. I am currently in a state of confusion over the correct setting of reference values for my three dimensional model by using FLUENT software. For example, if I assume that the flow of fluid is in the positive direction that is from left to right of the wind tunnel, what would be the right setting of area and length? I hope that your authority would kindly provide me with essential answers to brighten me up on this kind of problem. Any assistance and co-operation from your authority is greatly welcomed. Thank you.

The reference values, in general, don't matter too much. They are used in the calculation of particular quantities (for example, heat transfer coefficient is related to the reference temeperature and Reynolds number is related to the reference length). You can run the simulation with any reference values set as they won't actually affect the flow field. When you come to process the results though, you need to set the appropriate values for whatever variable you want to output - the fluent manual is very good and will tell you exactly how each quantity is calculated.

"Correct" settings for length and area etc. depends on what you are interested in - if you need to look at loss of the tunnel itself, length could be the hydraulic diameter. More likely though, you're looking at a model placed within the tunnel and so it should be a characteristic length of the model itself.

Anyway, hope that helps. But do look at the fluent manual, there's a wealth of info there.