A system is disclosed for detecting the laminar to turbulent boundary layer transition on a surface while simultaneously taking pressure measurements. The system uses an accelerometer for producing electrical signals proportional to the noise levels along the surface and a transducer for producing electrical signals proportional to pressure along the surface. The signals generated by the accelerometer and transducer are sent to a data reduction system for interpretation and storage

Hood, W. R.

English

NASA Technical Reports Server

United States Patent [191 
Hood 
SCANNING 
VALVE 
11 11 4,188,823 
[45] Feb. 19, 1980 
25 
DETECTION OF THE TRANSITIONAL 
LAYER BETWEEN LAMINAR AND 
TURBULENT FLOW AREAS ON A WING 
SURFACE 
Inventor: William R. Hood, Hampton, Va. 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Appl. No.: 964,009 
Filed: Nov. 27,1978 
Pnt. C1.2 .............................................. GOlM 9/00 
U.S. Cl. ..................................... 73/14? 73/205 L 
Field of Search ...................... 73/147, 205 L, 180 
References Cited 
U.S. PATENT DOCUMENTS 
PRESSURE 1 28 
TRANSDUCER 
2,519,015 8/1950 Bensen ................................... 73/180 
2,523,481 9/1950 Rabenhorst ............................ 73/147 
2,761,315 9/1956 Anderson Jr. et al. ................ 73/180 
AUDIO 
AMPLIFIER 
- 7 
AUDIO 
OUTPUT 
2,871,698 2/1959 Bagby .................................... 73/147 
2,957,345 10/1960 Cheney .................................. 73/147 
200838 10/1967 U.S.S.R. .................................... 73/147 
FOREIGN PATENT DOCUMENTS 
Primary Examiner-Donald 0. Woodiel 
Attorney, Agent, or Firm-William H. King; John R. 
Manning; Howard J. Qsborn 
C571 ABSTRACT . 
A system is disclosed for detecting the laminar to turbu- 
lent boundary layer transition on a surface while simul- 
taneously taking pressure measurements. The system 
uses an accelerometer for producing electrical signals 
proportional to the noise levels along the surface and a 
transducer for producing electrical signals proportional 
to pressure along the surface. The signals generated by 
the accelerometer and transducer are sent to a data 
reduction system for interpretation and storage. 
. 
7 Claims, 1 Drawing Figure 
c--- 
AIR FLOW 
https://ntrs.nasa.gov/search.jsp?R=19800011742 2020-03-21T02:29:51+00:00Z
U.S. Patent Feb. 19, 1980 4,188,823 
30 
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AIR FLOW 
PRESSURE 28 
TRANSDUCER 
4 
V 
AUDIO 
AMPLIFIER 
SCANNING 
VALVE 
AUDIO 
OUTPUT 
l l  
i 
DATA ACQUISITION SYSTEM 
f 2 7  
31 
f 
1 
AUDIO 1 Y E  1 
32 
4,188,823 
1 
DETECI'ION OF THE TRANSITIONAL LAYER 
BETWEEN LAMINAR AND TURBULENT FLOW 
AREAS ON A WING SURFACE 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
The lift and drag properties of a wing are determined 
in wind tunnel tests. This is done by measuring the 
pressure upon the wing surface at various points along 
the wing. In order to alter the wing shape to improve 
the lift thereof it is helpful to know the location of the 
transition between the laminar and turbulent flow areas 
of the wing. This is so because in general laminar flow 
over the wing results in lift whereas turbulent flow 
results in drag. Thus, it is desirable to encourage laminar 
flow and discourage turbulent flow over most of the 
wing surface. 
A method of measuring the pressure on the wing 
involves placing orifices at various points on the wing 
from the leading to the trailing edges. Pressure trans- 
ducers are connected to the orifices via pneumatic 
tubes. The present method of detecting the transition 
between the laminar and turbulent flow areas requires 
an individual to enter the tunnel and listen to the noise 
at each of the orifices using a stethoscope. Since the 
noise level of laminar flow regions is relatively low 
compared to that of turbulent flow regions the transi- 
tion between the two areas can be found rather accu- 
rately. However, there are several limitations imposed 
by this method. Firstly, an operator must be physically 
in the tunnel to connect his stethoscope to the orifices 
along the wing surface. Therefore, measurements can- 
not be made if the environment in the tunnel is hostile 
(e.g., the pressure is above or below atmospheric pres- 
sure) or if the space within the tunnel is limited. Se- 
condly, the pressure measurements cannot be taken 
while the operator is listening to the noise since the 
stethoscope (essentially an open tube) introduces a leak 
into the system. Thirdly, the noise levels cannot be 
recorded and correlated. 
It is therefore an object of the present invention to 
provide a system for detecting the transition between 
laminar and turbulent flow areas on a test surface that 
does not require an operator to enter the wind tunnel. 
Another object of the present invention is to provide 
a system for detecting the transition between laminar 
and turbulent flow areas on a test surface that provides 
an electrical output to permit data input to a multitude 
of systems, such as a computer for data reduction and 
storage. 
An additional object of the present invention is to 
provide a system for detecting the transition between 
laminar and turbulent flow areas on a test surface that 
allows pressure measurements to be taken simulta- 
neously with noise level measurements. 
The foregoing and other objects of the invention and 
many of the advantages attendant therewith will be- 
come auuarent when the claims and descriDtion con- 
SUMMARY OF THE INVENTION 
The present invention is an improved method of de- 
termining the transitional layer between laminar and 
5 turbulent flow areas on a wing surface. The invention 
essentially consists of replacing the stethoscope of the 
previous method with an accelerometer that is con- 
nected to the orifices placed upon the wing. The accel- 
erometer produces an electrical signal that is propor- 
10 tional to the noise level at the selected orifice in the 
wing surface. A scanivalve is used to selectively con- 
nect the accelerometer to a plurality of orifices creating 
a number of signals that can be recorded and graphed to 
yield a picture of the noise levels along the wing. From 
15 this picture the transition layers can be'found easily. 
BRIEF DESCRIPTION OF THE DRAWING 
The sole FIGURE is a schematic view depicting the 
components of the system and their relationship to each 
DETAILED DESCRIPTION OF THE 
INVENTION 
20 other. 
The invention can be understood best by referring to 
25 the accompanying drawing. As shown in the FIGURE, 
orifices 11 through 16 (many more are usually used), 
generally referred to as orifices 17, have been supplied 
to a wing surface 18. Pneumatic tubes 19 through 24, 
(tubes 19, 20 and 24 are not shown) extend from the 
3 0  inside of orifices 17 to a scanning valve 25. A pneumatic 
tube 26 extends from scanning valve 25 to an acceler- 
ometer 27 and a pressure transducer 28. Accelerometer 
27 and pressure transducer 28 produce electrical signals 
proportional to the noise level and pressure, respec- 
35 tively, at the orifices 17. Any suitable data acquisition 
system 29 is connected to both pressure transducer 28 
and accelerometer 27 to record the signals therefrom. 
Accelerometer 27 is also connected via an audio ampli- 
fier 30 to an audio output 31 to an audio tape 32 and to 
Airflow designated by arrows 33 is passed over wing 
surface 18. Scanning valve 25 is adjusted so that a pneu- 
matic tube extending from orifice 11 is connected via a 
pneumatic tube to accelerometer 27 and to pressure 
45 transducer 28. As air passes over orifice 11 the pressure 
and noise level thereat are thereby measured by pres- 
sure transducer 28 and accelerometer 27. Data acquisi- 
tion system 29 records the measurements. The noise 
may also be heard via audio output 31 and recorded by 
50  audio tape 32. Scanning valve 25 is then adjusted such 
that the pneumatic tube extending from orifice 12 is 
connected via a pneumatic tube to pressure transducer 
28 and to accelerometer 27. The pressure and noise 
measurements are thusly taken for orifice 12. In the 
55 same manner scanning valve 25 subsequently connects 
each of the remaining orifices one at a time to the mea- 
suring and recording apparatus. The laminar to turbu- 
lent boundary can be determined easily by visual in- 
spection of the resulting graph. 
It is seen, therefore, that this invention aids greatly in 
the determination of the laminar to turbulent boundary 
on a wind tunnel test model. Additionally, the invention 
allows both pressure and boundary layer measurements 
to be taken simultaneously. 
It is to be understood that the specific description of 
the invention contained herein is illustrative onlv and 
40 data acquisition system 29. 
60 
65 
I I  
tained herein are considered in conjunction with the 
accompanying drawings. 
that the actual invention is not so limited. Modifications 
and variations of the invention will be apparent to one 
4,188,823 
3 4 
skill& in the art. Such changes which are apparent to 
not depart from the spirit and scope of the appended 
claims and are intended to be included therein. 
What is new and desired to be secured by Letters 
Patent of the United States is: 
1. A device for determining the laminar to turbulent 
boundary layer transition on a surface the combination a scanning for connecting 
10 said orifices to said accelerometer and said pressure comprising: transducer. 
6. A device as in claim wherein =id acquisition 
surface and subjected to an airflow; 
a speaker connected to said amplifier for producing 
electrical signals proportional to the noise levels at 15 an audio output; and 
=id a recording means for recording the signals produced 
by said accelerometer, pressure transducer and airflow; amplifier. 
signals proportional to the Pressures at said orifices 20 ary layer transition on a surface subjected to an airflow 
upon the wing surface; and 
acquisition means for automatically collecting and providing orifices at various points along said surface; 
storing the signals produced by said noise detecting Pneumatically connecting said Orif ices  to a location 
remote to the environment of said surface; means and said pressure detecting means. 
producing audio frequency electrical signals at said 
remote location that are proportional to the noise 2. A device as in claim 1 wherein said noise detecting 
means comprises an accelerometer connected to said levels at said orifices; and 
orifice and an audio amplifier connected to the output 
of the accelerometer. 
3. A device as in claim 2 wherein said Pressure detect- 
those skilled in the art in light of the above teachings do ing means comprises a pressure transducer connected to 
said orifices. 
4. A device as in claim 3 including: 
pneumatic tubes extending from said orifices connect- 
ing said orifices to said accelerometer and said 
pressure transducer. 
5 
5. A device as in claim 4 including: 
a wing surface having orifices positioned along its 
noise detecting means for producing audio frequency 
along said wing surface caused by said 
means comprises 
Pressure detecting for producing 7. A method of detecting laminar to turbulent bound- 
comprising the steps of: 
25 
recording said audio frequency electrical signals. ' * * * * *  
30 
35 
40 
45 
50 
55 
60 
65 


Detection of the transitional layer between laminar and turbulent flow areas on a wing surface

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