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Theoretical Solutions for the Jet Flap Diffuser


Morel, Jean-Pierre Georges (1969) Theoretical Solutions for the Jet Flap Diffuser. Engineer's thesis, California Institute of Technology. doi:10.7907/Y75H-MC77.


This study proposes a jet sheet as an alternative to a rigid diffuser for a momentum propulsor. This appears attractive technically. The diffuser shape can be tailored by modulating jet momentum and angle and can be switched off in forward flight since its main function is increasing thrust/power ratio at static speeds. Theoretical analysis for a steady inviscid incompressible flow predicts impressive thrust augmentations. Taking into account the energy required to feed the jet sheet, it appears that in some cases propulsor thrust can be more than doubled. It could be applied to ducted fans, jet engines and seems particularly attractive for ejector thrust systems. A first approach of the study of the flow is made in the planar and axisymmetric cases by assuming that the velocity is uniform in each section. For the planar problem a linearized solution is presented. A conformal mapping transforms it into a half-plane boundary value problem of the Riemann-Hilbert-Poincare type. It is solved by combining Filbert Transforms, asymptotic expansion and a digital computer program. Then the nonlinear two-dimensional problem is presented with some references to the way it could be solved.

Item Type:Thesis (Engineer's thesis)
Subject Keywords:(Aeronautical Engineering)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lissaman, Peter B. S.
Thesis Committee:
  • Unknown, Unknown
Defense Date:28 May 1969
Record Number:CaltechETD:etd-11152005-140840
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4573
Deposited By: Imported from ETD-db
Deposited On:16 Nov 2005
Last Modified:03 May 2024 21:27

Thesis Files

PDF (Morel_jp_1969.pdf) - Final Version
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