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Flow at a Stagnation Point

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 .



Annica Warrick
Thurs July 11 15:24:48 EST 1996