A method is provided for visualizing aerodynamic flow effects on a test surface. First, discrete quantities of a sublimating chemical such as naphthalene are distinctively colored via appropriate dyes or paints. Next, a uniform layer of the sublimating chemical having a particular color is applied to the test surface. This layer is covered with a second uniform layer of a different colored sublimating chemical, and so on until a composite of multi-colored layers is formed having a discrete thickness. Friction caused by an airflow results in the distinctly colored layers being removed in proportion to such aerodynamic flow characteristics as velocity and temperature, resulting in a multi-colored portrait which approximates the air flow on the underlying test surface

Jensen, Ronald N.

English

NASA Technical Reports Server

United States Patent [19] [ i i ]  Patent Number: 5,070,729 
Jensen [45] Date of Patent: Dec. 10, 1991 
[54] MULTI-COLORED LAYERS FOR 
VISUALIZING AERODYNAMIC FLOW 
EFFECT'S 
[75] Inventor: Ronald N. Jensen, Hampton, Va. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 621,144 
[22] Filed: Dec. 3,1990 
[51] lat. c 1 . 5  .............................................. COlM 9/00 
[52] U.S. c1. ...................................... 73/14? 116/201; 
1 16/207 
[58] Field of Search ................... 73/147; 116/201, 207 
1561 References Cited 
U.S. PATENT DOCUMENTS 
3,787,874 1/1974 Urban .............................. 116/117 R 
3,835,703 9/1974 Bush ...................................... 73/147 
3,890,835 6/1975 Dotzer et al. ......................... 73/147 
3,913,393 10/1975 Facy ...................................... 73/105 
4,259,431 3/1981 Opitz et al. ........................... 73/147 
4,346,166 8/1982 Montag et al. ........................ 73/147 
4,350,757 9/1982 Montag et al. ........................ 73/147 
4,380,170 4/1983 Dotzer et al. ......................... 73/147 
4,727,751 3/1988 Holmes et al. ........................ 73/147 
4,915,975 4/1990 Watson ................................ 116/201 
Primary Examiner-Donald 0. Woodiel 
Attorney, Agent, or Firm-Kevin B. Osborne 
[571 ABSTRACT 
A method is provided for visualizing aerodynamic flow 
effects on a test surface. First, discrete quantities of a 
sublimating chemical such as naphthalene are distinc- 
tively colored via appropriate dyes or paints. Next a 
uniform layer of the sublimating chemical having a 
particular color is applied to the test surface. T h i s  layer 
is covered with a second uniform layer of a different 
colored sublimating chemical, and so on until a compos- 
ite of multi-colored layers is formed having a discrete 
thickness. Friction caused by an airflow results in the 
distinctly colored layers being removed in proportion 
to such aerodynamic flow characteristics as velocity 
and temperature, resulting in a multi-colored portrait 
which approximates the airflow on the underlying test 
surface. 
8 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19920012345 2020-03-24T07:08:21+00:00Z
5,070,729 
MULTI-COLORED LAYERS FOR VISUALIZING 
AERODYNAMIC FLOW EFFECTS 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the U.S. Government and may be manufac- 
tured and used by the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 
BACKGROUND O F  THE INVENTION 
1. Technical Field of the Invention 
The present invention relates generally to the visual- 
ization of aerodynamic flow effect and more particu- 
larly to the use of multi-colored layers to aid in such 
visualization. 
2. Discussion of the Related Art 
It is often useful to visualize air flow across a particu- 
lar surface to study specific aerodynamic effects. For 
example, viscous media such as oil or heavy gases are 
placed in test surfaces during wind tunnel tests. The 
deformations experienced by the applied media approxi- 
mate air flow patterns. These methods are expensive 
and are often messy. In addition, they often ignore the 
effects of isolated small areas of the test surface such as 
around a rivet head or where fluid separates from the 
surface. Also, sublimating chemicals of known mass 
have been applied to test surfaces, subjected to an air- 
flow, and then removed and weighed. The difference 
between the pre- and post-test masses is indicative of the 
amount of heat transfer between the air flow and the 
test surface. However, this method does not permit 
visualization of the flow. 
OBJECTS OF THE INVENTION 
It is accordingly an object of the persent invention to 
provide an improved visualization of aerodynamic flow 
effects. 
It is another object of the present invention to pro- 
vide such a visualization method which is simple and 
economicial. 
It is a further object of the present invention to visual- 
ize aerodynamic flow in discrete quantities. 
It is yet another object of the present invention to 
visualize the aerodynamic flow on small surface areas 
such as around a rivet head or where fluid separates 
from the surface. 
Additional objects and advantages of the present 
invention are apparent from the specification which 
follows. 
SUMMARY O F  THE INVENTION 
The foregoing and additional objects are obtained by 
a method of visualizing aerodynamic flow efforts ac- 
cording to the present invention. First, discrete quanti- 
ties of a sublimating chemical such as naphthak,::,e are 
distinctly colored. Next, a uniform layer of one p.;ticu- 
lar color of sublimating chemical is applied to the test 
surface. This layer is covered with another uniform 
layer of a different color of sublimating chemical, and 
so on until a composite of multi-colored layers is formed 
on the test surface having a desired thickness. Friction 
caused by an airflow results in the distinctly colored 
layers being removed in proportion to such aerody- 
namic flow characteristics as velocity and temperature, 
resulting in a multi-colored portrait which approxi- 
mates an air flow on the underlying test surface. 
DETAILED DESCRIPTION OF THE 
PREFERRED EMBODIMENTS 
The present invention utilized multi-colored layers of 
a substance applied to a particular selected test surface. 
The substance consists of a particular chemical com- 
pound that sublimes from the surface as the airflow in a 
10 wind tunnel reaches the particularized temperature and 
velolcity parameters of the specific test. Discrete quan- 
tities of the sublimating chemical are colored or dyed 
with respective identifying colors via such coloring 
agents as dyes, paints, ect. This colorization can be 
15 accomplished by any known method so long as the 
color of a resulting colored substance will not mix with 
the color of another colored substance when applied as 
discussed below. 
Once the discrete quantities of different colored sub- 
20 stances are prepared, one colored substance is applied 
to the test surface to form a first layer of uniform thick- 
ness. Next, a second uniform layer of different colored 
sublimating chemical is applied to cover the first layer. 
This application step is repeated as often as necessary to 
25 form a multi-layered, individually colored composite 
having a desired thickness. Each respective layer 
should be of uniform thickness to form a quantitized 
layer for visualization of the airflow; however, the re- 
spective layer may or may not be of equal thickness. A 
30 scaling process can be performed which correlates the 
thickness of a particular layer with the pressure and/or 
temperature conditions necessary to completely remove 
this layer from its position in the composite. The indi- 
vidual layers should be as thin as possible to permit a 
35 more detailed and exact portrait of the airflow. Also, 
the total thickness of the composite should be main- 
tained below a certain maximum value to avoid generat- 
ing any significant flow disturbances, Le., the composite 
should approximate a two-dimensional body. Finally, 
40 any selected color pattern for the layer may be utilized 
so long as adjoining layers are differently colored. 
Once the desired multi-colored layers are applied, the 
test surface is placed in a wind tunnel and subjected to 
airflow. As air flows over the composite, the resulting 
45 friction between the air and the uppermost layer causes 
this layer to be removed. The number of layers re- 
moved depends on specific localized air flow character- 
istics such as velocity and temperature. The applied 
composite thus results in a multi-colored portrait which 
50 substantially corresponds to the aerodynamic flow ef- 
fects on the underlying test surface. This portrait allows 
one to visualize the effects of friction, shock waves, and 
turbulent boundary layer transitions. 
This methods can be used to test small surface areas 
55 such as around a rivet head or where fluid separates 
from the surface since the application of the colored 
sublimated chemical may be quantitatively controlled. 
Also, the method can be used to visualize test surfaces 
both on a model in a wind tunnel or on the aecrody- 
60 namic surface of an an aircraft. 
A particular sublimating chemical for use in the pres- 
ent invention is naphthalene, which is relatively inex- 
pensive and often used in mothballs. Solid naphthalene 
is heated to form a liquid. Liquids are then mixed with 
65 respectively colored dyes such as oil-based paint. The 
colored naphthalene is then applied to the test surface in 
discrete layers by dipping, spraying or any other con- 
ventional method allowing the chemical to solidify 
5 
. 
5,070,729 
3 4 
between the application of the respective layers. The 
formed composite is then subjected to an airflow and 
the resulting airtlow portrait examined. 
Many modifications, improvements and substitutions 
will become apparent to one of skill in the art without 5 ite Of more than two different colored layers of subli- 
departing from the spirit and scope of the present inven- 
tion as described in the specification and defined in the 3. The ViSUaliZatiOn method according to C h h  2, 
following claims. 
2. The visualization method according to claim 1, 
futher comprising applying additional different colored 
uniform layers of sublimating chemical to said second 
layer ofcohred sublimated chemical to form a ComWs- 
mated 
wherein said coloring step comprises mixing discrete 
quantities of the sublimating chemical with oil-based 
4. The visualization method according to claim 2, 
wherein each layer is of the same thickness. 
5. The visualization method according to claim 1, 
wherein the sublimating chemical is naphthalene. 
6, ne visualized methods according to claim 5, 
wherein said coloring step comprises mixing discrete 
What is claimed is: 
1. A method for visualizing aerodynamic flow effects lo paints Of different cO1Ors’ 
coloring discrete quantities of a sublimating chemical 
applying a first uniform colored layer of the subiimat- 
on a test surface, comprising the steps of: 
different colors; 
ing chemical to the test surface; 
the sublimating chemical to the first applied layer 
to form a Composite Of layers Of different colored 
sublimated chemicals; and 
subjecting the test surface and composite to an air- 
flow, whereby the layers of the composite are re- 
moved by the airflow to create a portrait of the 
aerodynamic flaw effects on the underlying test 
applying a second, different colored uniform layer of quantities of the sublimating chemical with oil-based 
of different colors. 
7. The visualization method according to claim 1, 
20 wherein said coloring step comprises mixing discrete 
quantities of the sublimating chemical with oil-baed 
paints of different colors. 
8. The visualization method according to claim 1, 
wherein each layer is of the same thickness. * * * * *  surface. 25 
30 
35 
40 
45 
50 
55 
60 
65 


Multi-colored layers for visualizing aerodynamic flow effects

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