h ydrodynamic properties of annular cavitator
DESCRIPTION
H ydrodynamic Properties of Annular Cavitator. Presenter: Ming-dong LIN. College of Aerospace Sci. & Tech. N ational U niversity of D efense T echnology Changsha, CHINA. 1. Backgrounds. 2. Numerical Method. 3. Results & Discussion. 4. Conclusion. Contents. CAV2012, Singapore. - PowerPoint PPT PresentationTRANSCRIPT
Hydrodynamic Properties of Annular Cavitator
College of Aerospace Sci. & Tech. National University of Defense TechnologyChangsha, CHINA
Presenter: Ming-dong LIN
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Contents
1. Backgrounds
2. Numerical Method
3. Results & Discussion
4. Conclusion
CAV2012, Singapore
LOGO
CAV2012, Singapore
Backgrounds
Fully Wetted Drag V∝ 3
Propellor
Low speed (<70Kn)
Navigation styles underwater
Supercavitating
Drag V∝ 2
Rocket propulsed
Ultrahigh speed (>200Kn)
Revolution
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Backgrounds
Studies of supercavitating flow Logvinovich (IHM, Ukraine) proposed the theorem of
Independence of Caivity Section Expension, which is testified by many experiments.
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BackgroundsStudies of supercavitating flow
Kunz, Lindau, et.al (APL, The Pennsylvania State University, US) improved numerical method for both partial and fully developed supercavities, and coupled the flow simulation with the vehicle trajectory.
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Backgrounds
Studies of supercavitating flow Hydrodynamic properties of different cavitators
were tested by Kuklinski (NUWC, US).
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Backgrounds
Critical technologies of long distance supercavitating flight Supercavitating hydrodynamics
Water ramjet propulsion system
Advanced motion control strategy
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LOGO
CAV2012, Singapore
Backgrounds
Hydrodynamic properties
of annular cavitator?
Supercavity
water ramjetannular cavitator
with water injectionof “Shkval-E”
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LOGONumerical Method
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A. Governing equations The continuity, momentum equations of mixture:
The continuity equation of the vapor:
The mixture property:
( )( ) 0m
mt
u
T T( )( ) [ ( )]m
m m mpt
u
u u u u g
( )( )v v
v v m mt
u
m l l v v
1l v
LOGONumerical Method
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B. Rayleigh-Plesset cavitation model2
2B BB 2
B
3 2( )2
v
l v
p pd R dRR
dt dt R
ve v
B
3 2 ,3
nuc l v
l
p pm C p p
R
v
c vB
3 2 ,3
v v
l
p pm C p p
R
C. Standard turbulence model
( ) ( ) [( ) ]tm m k m
k
k vk k Gt
1 2( ) ( ) [( ) ] ( )tm m k mv C G C
t k
k
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Numerical Method Vehicle model
Computational gridsvehicle
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2m
10cm 20cm
100 /inv m s 0.2p MPa
500,000 grids
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Numerical MethodComputation setting
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Case Pout[MPa] Dtube[cm] Case Pout[MPa] Dtube[cm]
1 4.0 2.0 5 3.0 4.0
2 4.0 3.0 6 3.5 4.0
3 4.0 4.0 7 4.0 4.0
4 4.0 5.0 8 4.5 4.0
Table 1. Differenct CFD models and boundary conditions
LOGOResults & Discussions
Hydrodynamicproperties of
annular cavitator Cavitysize
Pressure field
Injectingflow
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Drag
LOGOResults & Discussions
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Pressure field
0 1 2 3 4 50
1
2
3
4
5
6
Pre
ssur
e (M
Pa)
r (cm)
Case 0 Case 1 Case 2 Case 3 Case 4
0 1 2 3 4 50
1
2
3
4
5
6
Pre
ssur
e (M
Pa)
r (cm)
Case 0 Case 5 Case 6 Case 7 Case 8
Pressure distributions on cavitator surface
Stagnation ring moves outward
Stagnation ring is stable
LOGOResults & Discussions
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Drag
Case Fcav[N] Ftube[N] Ftotal[N] Increment[%]
0 30608 0 30608 01 30260 1565.4 31825.4 3.982 28720 3408 32128 4.973 26480 5870 32350 5.694 23480 8886 32366 5.745 26740 5488 32228 5.296 26640 5676 32316 5.587 26480 5870 32350 5.698 26260 6076 32336 5.65
Table 2. Forces acted on cavitator region
Increasewith
tube size
Increasewith outlet
pressure
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Injecting flow
1 2 3 4 5 60
20
40
60
80
100 Mass flow Velocity
Tube Diameter (cm)
Mas
s flo
w (k
g/s)
10
20
30
40
50
60
Velocity (m
/s)2.5 3.0 3.5 4.0 4.5 5.0
0
20
40
60
80
100 Mass flow Velocity
Pressure Out (MPa)
Mas
s flo
w (k
g/s)
10
20
30
40
50
60
Velocity (m
/s)
Mass flow and velocities in different cases
LOGOResults & Discussions
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Cavity size
Decreasewith
tube size
Increasewith outlet
pressure
LOGOConclusions
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Pressure distribution changes significantly on cavitator surface which results in the increase of the drag.
The injecting flow is proportional to the tube size, and decreases with the outlet pressure.
Compare with disk, the annular cavitator generates smaller cavity. The cavity size decreases with the tube size and increases with the outlet pressure.
College of Aerospace Science and TechnologyNational University of Defense Technology