A method for visualizing off-surface flows is provided. The method consists of releasing a gas with infrared absorbing and emitting characteristics into a fluid flow and imaging the flow with an infrared imaging system. This method allows for visualization of off-surface fluid flow in-flight. The novelty of this method is found in providing an apparatus for flow visualization which is contained within the aircraft so as not to disrupt the airflow around the aircraft, is effective at various speeds and altitudes, and is longer-lasting than previous methods of flow visualization

Alderfer, David W.

Daryabeigi, Kamran

Manuel, Gregory S.

Obara, Clifford J.

English

NASA Technical Reports Server

US005200621A 
United States Patent 1193 [11] Patent Number: 5,200,621 
Manuel et al. [45] Date of ,Patent: Apr. 6, 1993 
[54] OFT-SURFACE INFRARED FLOW 
VISUALIZATION 
[75] Inventors: 
[73] Assignee: 
Gregory S. Manuel, Norfok Kamran 
Daryabeigi, Virginia Beach; Clifford 
J. 0- Yorktown; David W. 
Alderfer, Newport News, all of Va 
The United States of America 16 
represented by the Administrrr tor of 
the Nationnl Aeronautics and Space 
Administrrr tion, Washington, D.C. 
[21] Appl. No.: 
[22] Filed: 
[51] Int. C l . 5  .... 
808,302 
Dec. 16,1991 
................. GOlM 19/00; GOlM 9/06 
[52j U.S. a. ................................. 2~330, 250/338.5; 
250/340; 244/204, 73/147 
[58] Field of Search ....................... 244/136, 204, 207; 
73/147; 250/330, 334, 338.5, 340 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,693,015 9/1912 Funk, Jr. ............................. 250/564 
3,869,909 3/1915 Hale et al. ............................. 13/147 . 
3,911,244 8/1916 Stone ..................................... 13/147 
4,493,211 1/1985 Weinstein .............................. 73/141 
4,896,532 1/1990 Schmalz ................................ 13/141 
5,105,191 4/1992 Keedy ................................. 346/968 
. FOREIGN PATENT DOCUMENTS 
579681 8/1946 United Kingdom ................ 244/136 
Primary Examiner-Constantine Hannaher 
Assistant Examiner-Edw2d J. Glick 
Attorney, Agent, or Finn-George F. Helfrich 
A method for visualizing off-surface flows consists of 
releasing a gas with infrared absorbing and emitthg 
characteristics into a fluid flow and imaging the flow 
with an infrared imaging system. This method allows 
for visualization of off-surface fluid flow in-flight. 
[57l ~ . ABSTRACT 
5 Claims, 1 Drawing Sheet 
28 20 
https://ntrs.nasa.gov/search.jsp?R=19930012848 2020-03-24T07:30:13+00:00Z
U.S. Patent Apr. 6, 1993 5,200,621 
FIG. 1 
5,200,62 1 
1 2 
It is another object of the present invention to visual- 
ize an unlimited number of off-surface flow phenomena 
It is yet another object of the present invention to 
Additional objects and advantages of the present 
OFF-SURFACE INFRARED FLOW 
VISUALIZATION during a single flight. 
ORIGIN OF THE INVENTION 
employees of the United states Government and in the 
performance of a NASA contract and is subject to the 
provisions of Section 305 of the National Aeronautics 
(72 Stat. 435; 42 USC 2457). 
5 accomplish the foregoing objects in a simple manner. 
The invention herein was jointly made by invention are apparent from the drawings and specifics- 
tion which follow. 
SUMMARY OF THE INVENTION 
and additional objects are obtained by providing a 
method for visualizing off-surface fluid flow in which 
an infrared absorbing and emitting gas is released into 
15 the off surface area to be visualized and imaging the 
 his method may 
in 
flight, all of the components are located on board the 
2. Discussion of the Related Art aircraft and the gas is released from within the aircraft. 
The visualization of off-surface flow fields plays an 20 One examDle of an infrared absorbing and emitting gas 
and S P m  Act of 1958, as amended, Public Law 85-568 According to the present invention, the foregoing 
BACKGROUND OF THE INVENTION 
1. Technical Field of the Invention 
The present invention relates generally to flow visu- 
&tion, and more PdCularlY to Off-Surf- flow VkU- 
with an infrared -ging 
be used in a wind m e 1  or in flight. When 
alization using infrared imaging. 
important role in the analysis of aerodynamic ciaracter- 
istics observed during flight and wind-tunnel testing of 
aircraft co&igurations. Visualization can help provide a 
more complete qualitative understanding of important 
off-surface flow phenomena such as vortical flow for- 
mation, location, and breakdown. Without visualiza- 
tion, off-surface flow-field characteristics can be very 
difficult to understand. 
One type of off-surface flow, wingtip vorticity, oc- 
curs when the different air pressures of the upper and 
lower wing surfaces circulate about the wingtip area. 
This induced drag airflow causes the air to spiral past 
the wingtips and ultimately to form vortices behind the 
wing. In flight under high atmospheric humidity these 
vortices become visible, trailing downstream from near 
the wingtips, because of condensation of water vapor in 
the low-pressure vortex cores. This is an unsatisfactory 
method of visualizing off-surface flows because it only 
occurs at the wing-tips under particular atmospheric 
conditions. 
Active techniques to view in-flight vortical flows 
involve introducing smoke into the flow. One current 
smoke flow visualization technique consists of utilizing 
a smoke bomb explosive device that lasts one minute. It 
is small in size and is mounted external to the aircraft 
surface. Being of an explosive nature, the smoke bomb 
must have electrical leads connected to it for detona- 
tion. This technique is active for a very short time per- 
iod thus allowing for the visualization of only one vor- 
ticity pattern per flight and is not practical at high 
speeds. Additionally, the smoke bomb, because it is 
mounted to the outside of the aircraft, disrupts the flow 
phenomenon to be visualized. 
Another current smoke flow visualization technique 
consists of a large apparatus powered by aircraft electri- 
cal current that heats kerosene to its burning point to 
create smoke. This apparatus must be located near the 
is sulfur hexafluoride. The infrard imaging system 
consists of an infrared imager;an image control unit, a 
video tape cassette recorder, and an image monitor. The 
infrared imager operates in the wavelength range of 8 to 
BRIEF DESCRIPTION OF THE DRAWING 
FIG. 1 is a cross-sectional view of an aircraft. 
DETAILED DESCRIPTION OF THE 
INVENTION 
This method was tested in a singleengine, low-wing, 
light airplane 10 equipped with an infrared imaging 
system comprised of an Inframetrics 600 infrared 
35 imager 12, an image control unit 14, a video tape cas- 
sette recorder 16, and an h . g e  monitor 18. Other on- 
board equipment included a video camera and video 
tape cassette recorder, and a gas flow-seeding system. 
Because wingtip vorticity is a well understood aerody- 
40 namic phenomenon and its off-surface location is refer- 
ence to the wingtip is well known, the wingtip vortex 
was selected as the off-surface phenomenon for evalua- 
tion of the infrared technique. 
The Inframetrics 600 imager 12 was mounted in the 
45 rear cabin to provide a field of view downstream of the 
airplane's left wingtip 24). A filter was utilized to limit 
the spectral response of the system to 8 to 12 pm. The 
infrared imager 12 consisted of a single detector made 
of semiconductor materials. The detector was liquid 
50 nitrogen cooled to 195.5" C. for improved thermal scn- 
sitivity. The imager's lens focused the field of view on 
the detector, and rotating prisms and galvanometers 
provided the horizontal and vertical scan of the field of 
view across the detector. The lens used on the image 
55 scanner produced a lateral field of view of about 3.8 m 
at the left wingtip 20. The rear cabin window was re- 
moved because plastic does not transmit infrared radia- 
tion in the wavelength tested. 
25 12 pm. 
30 
point of smoke injection, and because of its large S k  is 
impractical for many applications. 
It is accordingly an object of the present invention to 
visualize off-surface flow phenomena. 
It is another object of the present invention to visual- 
ize off-surface flow phenomena using a method which is 
located entirely within the aircraft. 
It is another object of the present invention to visual- 
ize off-surface flow phenomena at various speeds and 
altitudes. 
The output of the system was a monochrome video 
60 signal which was displayed in flight on the image moni- 
tor 18 and recorded on 0.5-hch VHS cassette tape. 
The gas seeding system consisted of two sulfur hexa- 
fluoride (SF6) gas cylinders 22 mounted to a pallet 24, 
two flow control valves, two flow meters, and two 
65 digital flow meter displays. For safety considerations, 
the pallet enclosed the gas cylinders and incorporated a 
vent tube to the outside of the airplane. Flow control 
valves controlled the gas flow from the pallet 24 and 
5,2OO,62 1 
3 4 
flow meters measured the gas flow rate. The outputs of investigated the minimum SF6 flow rate to visualize the 
the gas flow meters were shown on digital displays. The vortex. The SF6 flow rate to the wingtip nozzle 28 was 
gas flow meter displays, the image control unit 14 and adjusted in flight via the flow control valve which was 
monitor 18 were located in front of the experimenter in accessible to the experimenter in the co-pilot seat. Four 
the CO-pilOt Position. The image control Ulit iS the Con- 5 backgrounds were mted-h, water, clouds/hme, 
tr01 unit for the imaging system. It is used to enter and and clear sky. Of these a clear sky provided excel- 
send operator commands to the imager concerning, for lent infrared images of the -gtip vortex. Unlimited 
e m P 1 e *  the of filter to be elmtrooptical visibility was not required, but rather an absence of 
zoom, desired gain and offset for the imager digitizer clouds. 
and pertinent parameters such as the temperature of the 10 
surroundings and the emissivity. The image contro1 unit tiom with various gas flow rates with a clear sky back- 
also receives the image data from the imager, performs ground dowed that the *sF6 gas n d e d  to 
A,, evaluation ofairplane anitude and velocity 
Processing convert image data to vis& the vortex at an indicated airspeed of 120 knots 
was J1 m3/-, independent of altitude. At an indie video Output which Can then be On standard TV monitors and recorded on standard 15 
VCRs. Two 1.9cm lines 26 were routed from the gas 
cylinder pallet 24 to flow meters and on to the two left 
wingtip nozzles 28 through the internal wing lines 26. 
cylinders 22. SF6 gas was chosen because it is inexpen- 20 
sive and is not hiumful to the environment. Any infra- 
within the aircraft into an area to'be visualized; and der 22 dispensed approximately 7.26 kg of SF6 at an 
operating pressure of 2070 kpa. The combined output of system* 
the two cylinders 22 produced a maximum gas flow rate 25 fluid flow Of 
of 0.57 m3/min. The gas flow rate decreased as the gas Claim 1 wherein the infrared abrbindemitting gas is 
was dispensed. Gas output was maintained for approxi- Sulfur h~xafluoride. 
mately 15 minutes. 3. The method for visualizing off-surface fluid flow of 
The flight tests were conducted over a speed range Claim 1 wherein the infrared imaging System consists of 
from 60-130 knots indicated airspeed and a pressure 30 an infrared imager, an image control unit, a video tape 
altitude range of 75 to 2750 meters during daylight cassette recorder, and an image monitor. 
conditions. The left wingtip vortex was seeded with the 4. The method for visializing off-surface fluid flow Of 
SF6 to determine the optimum conditions for infrared claim 3 wherein the infrared h a f i g  system is located 
imaging of the vortical flow. The response of the hfra- on board the aircraft. 
red imager 12 to different backgrounds was assessed. 35 5. The method for visualizing off-surface flows of 
The sF6 gas flow rate for the initial evaluation of differ- claim 3 wherein the infrared- imager operat ?s in the 
ent background conditions was at the maximum flow wavelength range of 8 to 12 pm. 
of 8o knots, o.06 m3,- was the mini- 
mum required to visualize the vortex with the infrared 
imaging system. 
what is claimed is: 
1. A method for vis.g off-surfm fluid flow on The SF6 gas was contained in commercial size D 
an aircraft in fight compeing 
red absorbing and emitting gas may be Used. J&h cylin- releasing an infrared abrbing/emitting gas from 
the area with an infrared 
2. The method for visualizing 
rate of approximately 0.57 m3/min. Later flight tests * * * * *  
45 
55 
65 


Off-surface infrared flow visualization

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