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Old 03-19-2002, 04:50 PM
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Default Reynolds number question.

I have a question. I observed that a scale Cessna and full version of this same airplane have different Reynold numbers, primarily due to different characteristic lengths. Thus, I concluded that scale cessna and model cessna will have diffrenet dynamic behaviour. Can someone explain to me exactly how this dynamic behaviour is different?

What I am trying to get at, is to compare the behaviour of the small plane to its real size counterpart especially the plane behaviour during windy conditions. I am trying to get a "seat of the pants" grip on whether the scale 182 responds to a 15 mph wind in the same fashion as the real one.

This question stems from a comment that I heard at the field. Someone said that us flying at 15 mph is like the real pilots flying the real plane at multiple of that wind speed. The person said that to find out what wind corresponds to the 15 mph wind for a model, you multiply the wind speed by the scale factor. So assuming the model Cessna is a 1/4 scale, it gives the full scale wind of 60 mph. I am almost sure this is wrong, becuase the individual did not give me any theoretical or mathematical explanation. That is why I started to look at some underlying theories.

I apologize for my naive tone of post, but I am not a mechanical or aeronautical engineer and I do not know anything about fluid dynamics. This is why I hope that someone knowledgeable will be able to explain this to me.

Thank you