Citation
Chapman, Dean R. (1948) Base pressure at supersonic velocities. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd12122008143236
Abstract
The existing theories of base pressure are described in detail and are shown to be unsatisfactory. An "exact" analysis is then made of the base pressure in an inviscid fluid, both for twodimensional and axiallysymmetric flow. It is shown that for a given body there are, in general, an infinite number of possible solutions satisfying all necessary boundary conditions. For the particular case of inviscid flow about projectileshaped bodies only one solution is possible, but it corresponds to zero base drag. This latter result is generalized and the following conjecture made: it is impossible for a steady axiallysymmetric inviscid supersonic flow to converge toward, and to meet the axis at a finite (nonzero) angle.
Since the inviscidfluid theory does not adequately describe the conditions in a real fluid, an approximate theory for base pressure in a viscous fluid is developed. This latter theory is based in part on the inviscidflow calculations and in part on dimensional analysis. It includes the effects of Mach number, Reynolds number, body shape, and type of boundarylayer flow. A comparison of the theory with the available experimental data indicates satisfactory agreement.
It is shown that under certain conditions the airfoil contour for minimum profile drag in a viscous fluid necessarily has a blunt trailing edge. Approximate calculations indicate that very substantial reductions in profile drag are possible by designing airfoils with blunt trailing edges. Consideration is briefly given to the interference of a support rod on base pressure measurements in a supersonic wind tunnel.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Degree Grantor:  California Institute of Technology 
Division:  Engineering and Applied Science 
Major Option:  Aeronautics 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Thesis Committee: 

Defense Date:  1 January 1948 
Record Number:  CaltechETD:etd12122008143236 
Persistent URL:  http://resolver.caltech.edu/CaltechETD:etd12122008143236 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  4979 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  12 Jan 2009 
Last Modified:  26 Dec 2012 03:13 
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