| dc.description |
The problem of free molecule flow over concave surfaces is
investigated, and general equations formulated for the lift, drag, and
heat transfer characteristics of such surfaces. The effect of multiple
reflections is taken into account by use of the Clausing integral equation
to determine the redistribution of molecular flux over the surface. It
is assumed that emission of molecules from the surface is purely diffuse,
and that the reflected molecules are perfectly accommodated to the surface
conditions.
The equations obtained are solved for the cases of (i) an infinitely
long circular cylindrical arc and (ii) a section of a spherical surface,
at hyperthermal velocities. It is found that under the above conditions
the local heat transfer characteristics are the same as those of the
corresponding convex surface, the total heat transfer being independent
of the geometry of the surface. As drag devices, the concave surfaces
examined prove only slightly more effective than a flat plate at similar
incidence, and as a generator of lift the cylindrically cambered plate is
significantly inferior to the flat plate at similar incidence. |
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