REPORT ON MEETING WITH DR. HAZEN, PRINCETON UNIVERSITY, ON 4 FEBRUARY 1958

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03642A001300040016-6
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 3
• Document Creation Date: December 22, 2016
• Document Release Date: June 14, 2012
• Sequence Number: 16
• Publication Date: March 7, 1958
• Content Type: MEMO

Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040016-6
? CONFIDENTIAL W
March 7, 1958
Subject: Report on Meeting with Dr. Hazen, Princeton University, on
4 February 1958
He has conducted much research in aerodynamics and has a
smoke tunnel at the University of Princeton which has proven very useful for
qualitative information on flow patterns. He was very interested in the proposed
blimp program. and stated that immediate and practical results can be obtained
in the area of flow separation control.
Considerable work has been done by Pfenninger on low-drag laminar boundary layer
stabilization. A considerable number of flight tests have been made with a B-57
in which 15 or 20 foot length bodies have been mounted in front of the fuselage
and measurements of flow made along this body.
Hazen indicated that turbulence and separation problems, particularly at low
altitudes, arise mainly because of the waviness and roughness of the skin. Even
0.002 inch particles cause breakdown of the flow. Waviness has been shown to be
the major problem, though this has been shown only in the two dimensional case.
At altitudes, the maintenance of flow problems are much reduced. Pfenninger's
work, using suction slotted on a section over the after part of thewing, has given
laminar flow up to Reynolds numbers of 36 x 106. To obtain 36 x 1;6 Reynolds num-
bers, he used 42 suction, slots between the 40% chord and the trailing edge of the
wing.
In tests made by Amos Smith at North A~perican Aviation, he was able to get laminar
flow up to a Reynolds number of 8 x 10 using a slotted configuration with suction.
Hazen pointed out that a slot, unless very carefully made, can in itself cause
the breakdown of the flow.
Hazen felt quite optimistic about preventing flow separation on the after portion
of a blimp. He was more pessimistic regarding the maintenance of laminar flow on
an operational vehicle, although he stated that Dr. Raspet at Mississippi State
College has been successful in maintaining laminar flow on a Piper Aircraft.
Apparently, in a Northrup presentation (at WADC) last year, Pfenninger made a
lengthy presentation on his scheme of boundary layer and separation control. In
order to reduce the wake drag on aircraft, the boundary layer should be kept just
on the verge of going through transition. At the trailing edge of the wing, it
should just go into turbulence.
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 Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040016-6
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March 7, 1958
The concept the Reynolds number is misleading when based on frontal diameters
or body lengths. The Reynolds number should be based either on the displacement
thickness or on the length of run.
Hazen pointed out that the work we have proposed is in an area in which much
is unknown and that work certainly needs to be done. Separation control is an
area in which immediate and practical results could be obtained. He felt that
boundary layer control to achieve laminar flow would require 10 to 100 times
as much power as the suppression of separation.
The smoke tunnel at Princeton might be very useful in determining flow patterns
on scale models if the concept of crude models which will give only qualitative
data is accepted.. Such a tunnel shows the gross flow behavior, including such
phenomenon as the shedding of vortices. It might be best for preliminary inves-
tigations because qualitative information could be obtained for the three dimen-
sional case, which to date has not been solved.
Hazen also discussed some work on submarine periscope oscillations which were
reduced substantially through the use of an external perforated (leading and
trailing edges) shield surrounding the periscope. Apparently, such an arrangement
gave a drag that was pretty much the same as that without the external shield but
eliminated the oscillation problem. A flat plate attached to the trailing edge
along the axis of symmetry did not offer the same stabilizing influence as the
above scheme. In some cases, if the plate were separated from the body by a
body diameter, it did have a stabilizing influence.
Boundary layer control on the control surfaces might be effective in giving proper
control without putting the control surfaces into the air stream. The work of
Lippisch on the "Aerodyne" was discussed. Hazen pointed out that Lippisch used
electronic stabilization and that the craft had no natural stability. The effect
on stability of power failure, which would eliminate boundary layer suction, should
be very carefully considered.
Clauser at Johns Hopkins apparently has been doing considerable work on boundary
layer control under adverse pressure gradients and is a foremost authority in
this field.
David Taylor Model Basin work has shown that elaborate laminar shapes have not
been worthwhile. They have conducted tests of a Goodyear design, with a laminar
shape and a single suction slot.
Work now in progress (sponsored by BuAer and ONR) will show where drag improvement
is possible on present airships. However, Hazen reiterated that the gains possible
through the control of separation would be extremely worthwhile and that this work
should be done.
The detection of turbulent flow by the stethoscope method was discussed. The
transition of the flow from a laminar to a turbulent condition generates audio
frequencies which can be detected from the inside of a blimp by the use of a
stethoscope placed to the skin.
Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040016-6
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040016-6
?
CONFIDENTIAL
To: Frank Coy
lp
March 7, 1958
Literature on boundary layer and boundary layer control was discussed. The
works of Schlichting and Pfenninger apparently are the best sources of informa-
tion at the present time. The Princeton series does not have a volume on this
subject yet.
The work of Gus Raspet has been done mainly at sea level conditions. He has
had po problems in maintaining the laminar flow to Reynolds numbers of 3 or 4
x 10 He will have data on full scale blimp flight tests in approximately 12
to 18 months on a currently sponsored ONR program.
Copies to:
L
Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040016-6