Hi everyone,

I'm trying to figure out a way to represent airflow through my roaster so I can understand and record what I'm doing. Basically, I want to figure out how the airflow is changing as I close the damper.

I'm thinking I don't need to figure it out in absolute manner, but just normalized from 0 to 100%.

My roaster has a fairly normal damper: it is a flat plate that rotates from parallel to the airflow to completely perpendicular, blocking the exhaust pipe. I want to relate the angle of the plate to the percent of airflow.

Here's what I'm thinking. I can do the math for the simplest model, but if anyone has any numbers or equations for the more complex models I would appreciate it. Models, from simplest to most complex.

1. The plate blocks airflow proportional to its cross section. This would be a simple sine function.

2. The above, with calculations for the angle of the plate and how that affects airflow around the plate

3. The above, with calculations for friction, laminar vs. turbulent flow, etc. at this point, it may be better to go to empirical data?

I know that fluid dynamics is a pretty extensively studied field, and I'm guessing the answers are out there somewhere. I have my old college textbooks, but that was a while ago. Can anyone here help me out or have some thoughts?