Near the front stagnation point on a blunt body of revolution whose axis is aligned with an oncoming flow, there is an axially symmetric flow that is analogous to the plane stagnation point flow illustrated on the left side of figure 11.10 and described by equations 11.42--11.43. The stream function and velocity components of the axially symmetric flow can be given as:
where the constant , having the dimensions of reciprocal time, can be related to
the pressure distribution near the stagnation point, as shown below.
Figure 11.23: The streamlines of the flow near an axisymmetric stagnation point for equal
increments in with the axial dimension vertical.
The streamlines of this flow are plotted in figure 11.23 with the z-axis
vertical for comparison with the plane stagnation point flow illustrated on the left side
of figure 11.10. The stagnation point of the flow (
) is located at the
origin,
, where the streamline
that comes from
bifurcates to
run along the r-axis. The streamlines farther from the z-axis are more closely
spaced in axisymmetric flow than in plane flow.
The pressure distribution in the vicinity of the stagnation point may be related to the
stagnation pressure at the stagnation point
by utilizing Bernoulli's
equation between any point
and the stagnation point:
If we differentiate equation 11.83 twice with respect to r, we find:
The constant is thus related to the second derivative of
.