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15.7: Display Distribution of Reynolds Number

The term Reynolds number is often found in context with airfoil polars. The Reynolds number is a measure for the flow characteristics of an airfoil. It can be computed with following simple formula:

Re = c* v * 69930
c chord in m
v velocity (airspeed) in m/s

The flow characteristics of an airfoil for a large aircraft and an airfoil for a model airplane are equal, if the Reynolds numbers are equal. This happens only rarely in practice.

Small Reynolds numbers (60.000-300.000), typically found in model flight, bring along the following problems:
1) The range for the angle of attack is small.
2) The viscous drag is considerable bigger than with large aircrafts.
3) Bubble formation might occur, which changes the airfoil contour and produces additional drag.
If one plans to build a model of a large aircraft to scale, one has to bother about the right airfoil choice. An airfoil that works well with construction of large aircrafts might become a nightmare when used for a model airplane. The Reynolds number is obviously an important fact to deal with, if one intends to construct airplanes.

Select this button to display the distribution of the Reynolds numbers in the 2D-graphic.



The picture below illustrates this function.



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