Both oscillating and steady flows were applied to a single plexiglass resonator cavity with colored dyes injected in both the orifice and grazing flow field to record the motion of the fluid. For oscillatory flow, the instantaneous dye streamlines were similar for both the short and long-neck orifices. The orifice flow blockage appears to be independent of orifice length for a fixed amplitude of flow oscillation and magnitude of the grazing flow. The steady flow dye studies showed that the acoustic and steady flow resistances do not necessarily correspond for long neck orifices

Baumeister, K. J.

Rice, E. J.

English

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https://ntrs.nasa.gov/search.jsp?R=19760020430 2020-03-22T14:45:56+00:00Z
NASA TECHNICAL
MEMORANDUM
(NASA-f!1-X-7 ? U CC) 	 FL(W VISUALIZATICb
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FLOW VISUALIZATION IN LONG NECK HELMHOLTZ
RESONATORS WITH GRAZING FLOW
by Kenneth J. Baumeister and Edward J. Rice
Lewis Research Center
Cleveland, Ohio 44135
TECHNICAL PAPER to be presented at
the Third Aero-Aco,
	 ,s Conference
sponsored by the American Institute of Aeronautics
and Astronautics
Palo Alto, California, July 20-23. 1976
 
IN.
JUL
RECEIVED
f, NASA STI FACII ilt
a INPUT 8RA.NL
dIUW VIOUALIZAY;',:: III LON(; NECK
HIiLI•iFOLTL LESDIMORS WITH GRAZING IlVd
Kenneth •', baumciater and Edward J. Rice
Stational Aeronautics and pace Administration
Lewis Rq noarch Center
Cleveland, Ohio 441',%
Ahntract
1'oth oncillutia iS and steady flown were applied
to a cinrlu Ple;:i glow- resonator cavity with ^•ol-
ored dyes in,iectcd in both the orifice and Cra.•cinC
flaw fieli to r000rl the motion of the fluid. For
)ncllLitory flow, the in:=tantaneous dye :.tremallnee
were similar for both the short and lon:•-hock or-
ifice.,
	 he orifico floe blovkarc appoarc to to in-
donendent of on Tice 1en,,th for a fixed amplitu]e
of ]low oscillation ant ma gnitude of the rrazine
plow, '!lie ate:.:dy flow -ye rtualea showed that the
se7uatle and steady i'i.ow resistencec du not necec-
nurily correoponr Tor lonl7, neck orifices.
Introduction
Either oscillating or steady flow can be ap-
plied to the resonator through the valvim , chown in
Fitt. 1. The oscillatory flow was intended to aim-
ulate acoustic oscillations while the steady flow
wan intended to simulnte a common method of mean-
uring, the resistive portion of the resonator im-
pedance. The flow oscillations to the resonator
cavity arc driven by a nervo-controlled hydraulic-
ally operated Vinton, as shown in dig. 1, i'he Sds-
ton could to oscillated from U.1 to 50 hortz. For
the purpose of these experiments, the frequency was
cat at 2 hertz. At higher frequoncion (;;renter
than 10 Iiz), the equipment had a tendency to vi-
brate. At frequencies lower than 2^. hertz, the re-
oultim, pulse was not sinusoidal. This lattur ef-
fect war thought to occur because of recunaree in
the fluid line.%
ry
m
w
.cepite 4oncideraUa research dur : the last
aoca,e, there in ::till mvch unknown uot-erning the
dechanlem of acoustic crer;y dionipation by a roco-
orrtor in the preccnco of eraainc flow. More de-
tailea information in needed re,,ard'lnC the physical
flaw interaction proce.0 oocurrin,; near the mouth of
a 1 :elx bolt:: resonator in the pronence of ,crazing
flea. 'lu uncertain the nature of the flow process
for hint •. neck resonators, a vioual study of the of-
fact of ,%razin,, flow on the oscillatory flow in a
lon, < neck orifice has been performed in a plexiglaso
flow channel with a ninCle side branch Heliftholtz
reconator using water an the fluid media and cO.-
cred dyes to trace the fluid motion..
In this investigation, both oscillatory and
steady flow were applied to the back cavity of the
long neck resonator. The motion of the dyes and
thus the fluid are recorded by a hiCf- speed aware,
Individual motion-picture frames are presented in
thin report to illustrate the flow regimes, The
motion picture from which the still photoLmapho in
thin re port were taken may be obtained by contacting
the authors,.
f,rraratus and Procedure
Figure 1 is a schematic diagram of the tent up-
paratus, ; he apparatus is essentially a once-
throu <h water flow system, fhe main channel is
9O cm long with a reetanirular crocc section 2,54 em
by S cm, F.etaila of the short neck resonator cav-
ity are shown in ar, 2, while details of the lour
neck resonator cavity are shown in 1.11.	 For
both so-so, the orifice hole is a square 1.27 by
1.27 em. The square ;;eometry rather than a circular
one was chosen for cane in photographing the flow.
The short neck resonator has a lergth to diameter
(hydraulic) ratio of 0,5 while the LJD of the long
neck resonator is 4.
'Three different color dyes can be injected in-
to the flow field (see Pig. 1). The dye flows un-
der the action of Gravity to the dye injection lo-
cations marked in :'1gs, 2 and P. 'fhe needle valves
shown in Fir„ 1 were adjusted to prevent ,jettin¢ of
the dye co as to minimize any disturbance to the
flow field. Water soluble dyes were used.
For convenience, the oscillatory+ flow vac ap-
plied to the reconator cavity rather than the main
:stream• In this munner, the magnitude of the flow
oscillation in the orifice could be precisely cun-
trolled by varying the stroke or the piston, it
wan fvand experimentally In ref, 1, that the same
type of flow profiles in the orifice occurred
whether the flow oscillation was introduced in the
back cavity or in the main stream. Uoin g thir: pro-
cedure allows the resonator cavity to be full of
water with no need for an air bubble to provide
compliance,
The Crazing flow was measured with a turblr,e
flovrmoter and the frequency of the piston was clop
measured, The high-speed motion-picture corera wan
positioned adjacent to the resonator cavity. 'f he
velocity field in the orifice and in the main water
channel can be determined from the high-speed no-
tion pictures by following the movement of the dye,.
In the entrance region of the main flow chan-
nel, a system of screens and baffle;: was added to
produce an initially uniform velocity profile in the
flow channel. From velocity profile meacuremento
reported in ref. l,. the "boundary layer" extends
approximately 0.3 cm from the wall. This t',Ivan a
ratio of boundary thickness to orifice diameter
(hydraulic) of around 0.25, which iz -mall compared
to the corresponding ratio in actual flow ducts.
Although this may change the magnitude of the renic-
tance, it should not chance the general character-
ictfes of the flow regimes.
Durint a run, the Crazing flow velocity in the
main channel wau first cot. Ilext, the frequency
(2 Hz) and amplitudes of the resonator Slow per-
turbation were set. Y} pally, the valves to the dye
reservoirs were opened. Srhen desired, a high-speed
motion-picture -amera recorded the flow patterns,
Generally, the camera was run at .00 framed per
second.
Scaling Considerations
The intent of thin ::turfy was to provide a vis-
ualization and hence a better underntandin of the
air flow process in a resonator orifice in the
REPRODUCT(3ILITY OF TIII•,3
ORIGINAL .Pa G1,1
 i5 POOR.
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1
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f	 R
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T
presence of a grazing steady flow. It is important
to consider whother the water system simulates an
air system.
Aased on the wek of Thurston and Har rovc(Z)
and Ingard and Iaing^l) , Hersh and Rogers ( I ) pro-
vide convincing evidence that air-water bimilitude
exists for the resistance and reactance Tor flow in
the orifice. Reference 1 also discusses this topic
an well as presenting come numerical examples,
outside the hole, similarity of the air-water
cyotem with Crazing flow may be inferred because
grazing flow Reynolds numbera bated on the diarn-
etern of the orifices are similar. Finally, the
or+.rice to ; =ing stream momentum ratios are aim-
ilar thus implying dynamic force similarity.
Orifice Flow Visualization
The following several flruren summarize the
oscillatory flow and steady flow regimes for a
.simulated resonator. orifice. The figures contain
single frames taken from a motion picture study.
All the photographic cequencen are for Slow in the
orifice in the presence of a grazing flood. Photo-
rrapho of oscillating orifice flow in the aboence
of grazing  flwa can be round in ref. 1.
Photographs for oacillatory flow for a short
and then a long neck orifice will be presented and
compared. Noxt, photoCrapho for oteady flow, into
both the short and long neck orifice will be pre-
ce.ted and related to the oscillatory flow. The
steady flow in of interest since measurements on a
steady floor system ue a practical way of eatimat-
inC the orifice - stance to an oscillating
flow(5),
oscillatory ilod ReRirnec
The oscillatory flow regimen are illustrated
in Fire. 4 and 5 which shows one cycle with both
inflow and outflow to a short and Song neck orifice.
As documented in refs. 1 and 4, the resistance due
to Crazim; flow may be viewed qualitatively as an
orifice blockage effect which is evident in the
sequences in Fire, 4 and S.
In contract, in the long neck orifice ( Fig. b)
the entering fluid at the top of the orifice is
directed downward by the action of a small eddy
formed at the lower lip of the orifice. Partial
dissipation occurs during the turning process, how-
ever, sane of the kinetic energy will be directed
back into the main stream of the crazing flow dur-
ing the outflow cycle, Recall, in the short neck
orifice all the kinetic energy was dissipated in the
back cavity. Therefore, the acoustic rocictunce
may be a function of the length to dlernater ratio
of the orifice.
On the outflow portion of the eyele t the or-
ifiw flow is seen to encounter the large axial
momentum of the Crazing flow which must be dis-
placed before the orifice flow can emorge. In both
the chart and long neck resonator, the outflow
streamlines look similar. The streamlines leaving,
the orifice turn downstream in parallel with the
grazing flow.
One striking difference between the osofllat-
ing flow in the short and long neck orifice in the
presence of an oscillating slug in the neck of the
lone orifice. In the motion-picture study of this
oscillating slug, a red dye was used to mark the
position of the slue an a function of time. To
make this slug visible in a black and white photo-
graph,. a large concentration of the red dye wan ad-
ded in the rear of the orifice, an shown in Fir.
The inertia of the slug accounts for the increase in
reactance that theory predicts for the long neck
orifice.
Steady Flow Regimes
Zorumoki and Parrott ( 5) found for short neck
orifices that the instantaneous resistance is in-
dependent of frequency and in, therefore, equiv-
alent to the flow resistance of the orifice. The
flow resistance is defined as the ratio of the
steady pressure drop across a material to the gt@ady
velocity through the material. Feder and Lean C
also chow a close correspondence between the aeouc-
tic and steady flow resistances in the presence of
a [gazing fled.
Short Neck
For the short neck orifice an shown in Fig. 4,
during the inflow portion of the cycle ( t =. 0 to
0.21 sec) the axial momentum (vertical) of the
grazing flow makes it difficult for the fluid to
negotiate the turn into the orifice. This results
in a large separation or dead flow region at the
lower side of the orifice which effectively reduces
the area of inflow. The inflow region in seen to
be limited to the small channel at the top of the
orifice. For a long neck orifice, similar results
are shown in Fig. 5 during the inflow portion of the
cycle (t - 0 to 0.228 sec).
In the short neck orifice, the kinetic rnergy
of the entering jet of fluid is diss ipated in the
back cavity. At the beginning of flow reversal In
Fig, 4 ( t = o.23r sec), new flow from the resonator
cavity is pushed outward through the lower or dead-
water portion of the orifice area while the inertia
of the fluid which had just entered the orifice
near the upper surface continues to carry that fluid
back int.; :he resonator cavity, Therefore, for
short neck o,it 'ices, the resonator cavity acts as
the sour^e of fluid for the outflow portion of the
flow osci", . 4.-n cycle.
Ucing Fig. 4 as a basin for modeling the flow
fields of a short neck resonator, Fig. C presents
schematics of the three flow regimes associated with
one oscillation cycle. The flow fields of the
steady inflow and outflow from the resonator -lately
approximate the instantaneous flow fields of the
resonator due to an oscillatory flopr field, as seen
in I'ie. 4, Figure 7(a) shown a photograph of the
flow field for a typical. inflow setting, In Fitj-
7(a) the back cavity was filled with dye and the
Inflow is shown by the clear region near the top of
the orifice. The streamline represented by the
outer edge of the dye closely approximates the dye
streamlines seen in Fig. 4 at t = 0 . 122 and 0.178
seconds. Therefore, the steady flow visualization
confirms the earlier obnervationo made by Zorumcki
and Parrott ( 5 ) for inflow to the orifice. Similar
results occur for outflow.
Unfortunately, the treamlinon associated with
oscillatory flow near transition from inflow to
outflow can riot be duplicated with a steady flow
experiment. The advantage of oscillating flo pr vis-
ualization over that of steady flow can be seen by
r
X45'
the cequeney t o 0,170 to 0.31? ascends in Fig, 4,
At t s 0,170 coeondo, hint velocity inflow enters
at the top of the orifice while a dead region so-
aura at the bottom. As tine progroccoo, tho pros-
aura drop acroas the orifice changes to a higher
pressure on the left of the orifice than on the
ri&h (favors outflow), The hirh velocity jet re-
giono cannot be iratodiately stopped and reversed.
The dead rogior can, however, be more quickly ac-
celerated to furm an outflow. Thus there is an In-
start in the cycle where inflow exists on the top
of the orifice and outflow exists on the bottom
such that the not flow through the orifice is sere.
Around this zero flow condition, a resistance-tire
(or net flow) history should be produced which is
continuous. In effect, the two-dimensional quality
of the dynamic flows will remove the discontinuity
of resistance at zero through f }}ow which was ob-
served by Budoff and Zorumski( 7 / and Rogers and
Hersh g)
Lon- deck
The atealy streamlines in a long neck orifice
do not match, in general, the instantaneous dye
trace patterns in the two orifice under the con-
ditions of an oscillatory flow, az Been by comparing
the dye traces in Figs. 7(b), (v ), and (d) to the
dye lines in Fir. 5. I'or relatively low inflow, as
zh mo in IIC. 7(b), the flow reattaches to the low-
er orifice wall. Consequently, the cteady flow re-
oistance measurement cannot be assumed equal to the
inotaneouc oscillatory flow resistance.
For the larger inflow rates (Pig, 7(e) and (d),
separation secure in the long; neck and the resonator
back proccure in felt at the vectream enhance at
the orifice, Under these conditions, the cteady
flow resistance ndght approximate the instantaneous
inflow resistance.
Summary of Results
By means of colored dye traces, photographic
sequences illustrate the detailed structure of an
oscillating orifice flow with and without the pres-
ence of a grazing flow field, Specifically, the
following maJor results were found:
1. For flow into the resonator with grazing
flow, the orifice flora area blooko.Ce appears to be
independent of orifice length for a fixed amplitude
of flow oscillation and magnitude of the Crazing
flow, For short neck resonators, all the entering
kinetic enerrar is dissipated in the resonator cav-
ity; however, long; neck reconatorc return come of
the entering kinetic energy back to the grazing
flow field. Therefore, the acoustic resistance may
be a function of the length to diameter ratio of the
orifice,
2. As chovm in the photographic sequences, at
the crossover from inward to outward flow, flan
exists simultaneously inward and outward in dif-
ferent parts of the orifice. Thus, no discontinuity
in resistance will exist in an osei;latinr syztem
when the average jet velocity approcuhcz zero from
either the inflow or outflow directic
3. For long neck resonators, the instantaneous
fluid streamlines for oscillatory flow do not, in
general, match the steady etreamlires in the name
orifice. Therefore, the acoustic and steady flow
resistance do not necessarily correspond.
References
1, Baumoicter, K. J. and Rise, J,: "Visual Ctudy of
the Effect of Grazing Slow on the Oscillatory
Flo,, in a Resonator Orifice," M X-3200, Cept.
lO'rb, RAGA.
2. Thurston, G. B„ Hargrove, Jr„ L. E., and
Cook, W. D„ "Nonlinear properties of Circular
Orifices," .wet Acoustics Cocinty of America.
Vol, 20, 1967, pp. 9112-1001.
S. Ingard, U. and Icing, H., "Acoustic Nonlinearity
of an urifico," Jet Acoustics Society of
America. Vol. 42, IU,17, pp. n-17.
4. I[orsh, A. 0, and Rogers, T., "Fluid mmebmnical
godol of the Acoustic Impedance, of Cmall
Orifices," AIM Faper 75-4%, Hampton, ±a.,
197,.
,. 7.orumski, W. E. and Pv,rrott, T. L., "Nonlinear
Acoustic Theory for Rigid loroua 11aterial.o,"
'fit D-e19c, June 1971, NAM,
r. Fewer, E., slid Dean, L. W., "Analytical and
Experimental Otudies For Predicting Noire At-
tenuation in Acoustically Treated Ducto for
Turbofan Engineo,." CE-1576 1 Copt. Lars,. IWA.
7. Budoff, :1., and 7.orumaki, W. E., "Pio:r i;ccictanco
of perforated Flatco in Tangential cloa," TIt
X-26ul, uct. 1971, NASA,
0. Rogers, T., and Iferoh, A. G., "The Effect of
Grazing Flow on the Steady Otate Resistance wf
Cquare-Edged Orifices," AIM leper 7L-406,
Hampton, Va., 1975,
qBlue Yellow
	 Red	 i
rDye
-	
--	 reservoir
mp On-off	 -
valve -.
 -Needle
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Yraulic
I	 i	  	in
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I	 I
Frosted
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ing piston of i	
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frequency ^-esorifice
plitude tam 	 si r
l
I
i	 High-speed camera
-Water I	 ------__--_ .	 (900 to test section)
reservoir
plexlglass
flow channel
Osculating
i_
Baffle and screen
------------------flow
Steady flow
	
Turbine	 I	 City water main
flowmeter-- -_l 	 grazing flow
Drain
Figure 1. - Apparatus schematic for visualizing oscillatory flow In resonator orifice in presence of grazing flow,
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CAVITY	 I
	
11	 s _
•	 V1,
t • 0	 t-0.061 sec	 t-0. 122 sec
Start of	 Beginning of 	 Inflow
cvcle	 inflow
^	 I
r^
,L
1-0.178	 t=0.236	 t	 0.312
Inflow	 Beginning of	 Outflow
flow reversal
P
t=0. 364 sec	 t-0.44 sec	 t=0,5sec
Outflow	 End of outflow
	
Beginning of
new cycle
Figure 4. - Flow regimes with 0.3-meter-per-second grazing flow and inter-
mediate amplitude oscillating orifice flow at 2 hertz.
k
BACK CAVIT', 
V.
t - 6 SEC; START OF CYCLE
G'
1
t - 0.164 SEC; INFLOW
t-0.110!
OF INFLOV
t - 0.22E
I - 0.278 SEC; FLOW
REVERSAL
1-i
t - 0.390 SEC; OUTFLOW
11k.
1	 `f
t - 0.348 SEC; OUTFLOW
Y
^	 r
t - 0.442 SEC; OUTFLOW
t^^-- ,
I - 0.5 SEC; BEGINNING OF
NEW CYCLE
Figure 5. Flow regimes with 0.3 meter-per-second grazing
flow and moderately high amplitude oscillating flow at
2 hertz.
leis, .
* LONG NECK - LOW INFLOW.
t
GRAZING
FLOW
INFLOW	 TRANS IS) ION	 OUTFLOW
figure 6. -Oscillatory orifice flow regimes with grazing flow.
MN
n
.A
BACK
CAUIT'
i
i
(a) SHORT NECK.
(c ►
 LONG NECK - MODERATE	 Ids LONG NECK - I ARGE INFLOW.
INFLOW.
Figure 7. - Steady flow into short and long neck resonator cavities.
NASA-Lewis


Flow visualization in long neck Helmholtz resonators with grazing flow

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