Computer programs predict effect of slipstream-wing flow interaction on aerodynamic characteristics of deflected slipstream and tilt aircraft. One program calculates lift distribution, lift, and drag of wing in wide slipstream. Results permit development of simplified lifting surface theory for circular jet

Jameson, A.

English

NASA Technical Reports Server

February 1971
	 Brief 71-10030 
NASA TECH BRIEF
	 i - A  
_4V A mes Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Lift Distribution in a Rectangular Jet 
The problem: 
There is an apparent need for VSTOL aircraft to 
relieve air traffic congestion. One of the most promis-
ing methods of reducing take-off and landing distances 
is to use propellers or ducted fans to augment the 
airflow over the wing at low speeds. It is necessary to 
be able to predict the effect of slipstream-wing flow in-
teraction on the aerodynamic characteristics of de-
flected slipstream and tilt aircraft. 
The solution: 
Two programs have been developed for the pre-
diction of slipstream-wing flow interaction. The first 
of these calculates the lift distribution, lift and drag 
of a wing in a wide slipstream, such as might be 
produced by several propellers. 
How it's done: 
To restrict the complexity of the calculations, it 
is desirable to use the simplest possible analytical 
models. Two models of a wide slipstream have been 
found to be amenable to analysis: a rectangular jet 
and an elliptic jet. The rectangular jet is particularly 
suitable for an analysis of the static case, when the 
aircraft is in a hovering condition. The situation of the 
blown part of the wing is then similar to that of a wing 
in an open wind tunnel, making it possible to draw 
upon existing theories of wind tunnel interference. The 
distinguishing features of the present case are that the 
wing may span the entire jet and that the aspect ratio 
of that part of the wing which is in the jet may be small. 
These features make it desirable to allow for both 
the spanwise and the chordwise variation of the inter-
ference downwash. With a rectangular jet it is possible 
to satisfy the boundary condition for the static case 
at every point of the jet surface throughout its length 
by introducing images, so that a lifting surface theory 
can be readily developed.
Unfortunately, this theory is exact only for the 
static case, since it is no longer possible to satisfy the 
boundary conditions at the surface of a rectangular jet 
by introducing images when the aircraft has forward 
speed. Using an elliptic jet as a model of the slipstream, 
it is possible, however, to develop a simple lifting line 
theory which is valid throughout the speed range. 
From the results of this analysis, it is then possible to 
determine a correction factor for the effect of forward 
speed on the rectangular jet. In this way, an approxi-
mate lifting surface theory is obtained for the whole 
speed range. By using the results of calculations for a 
square jet to estimate the chordwise variation of the 
interference downwash, it is also possible to develop 
a simplified lifting surface theory for a circular jet. 
Notes: 
1. This program was written in FORTRAN IV for 
use on either the IBM-360 or IBM- I 130 computer. 
2. Inquiries concerning this innovation may be di-
rected to: 
COSMIC 
Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B71-10030 
Patent status: 
No patent action is contemplated by NASA. 
Source: Antony Jameson of

Vehicle Technology Department

Grumman Aerospace Corporation

under contract to

Ames Research Center

(ARC-10424) 
Category 09 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000030 2020-03-17T02:17:11+00:00Z


Lift distribution in a rectangular jet

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