Ocean Engineering Group (OEG)/EWRE
Transcript of Ocean Engineering Group (OEG)/EWRE
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Ocean Engineering Group (OEG)/EWRE (August 24, 2017)
Spyros A. Kinnas
Professor and Director of OTRC’s UT Office
(Offshore Technology Research Center)
(Google: Kinnas Home Page – check courses and
OE Theses/Dissertations)
Research in the area of computational hydrodynamics with
applications on the prediction of performance and design of high-
speed marine propulsors or turbines, modeling of cavitating or
separated flows, and wave/body interaction.
Facilities:
•CHL (Computational Hydrodynamics Laboratory) in ECJ 8.502
Teaching:
•CE358: Introductory Ocean Engineering (Fall ’17 - 11-12:30, Tu & Th)
•CE319F: Elementary Fluid Mechanics
•CE380P.4: Boundary Element Methods (Fall ’17 - 12:30-2:00, Wed & Fri)
•CE380T: Computational Environmental Fluid Mechanics (Spring’18 – tent.)
•CE397-32: Theory of Propellers and Turbines (Fall ’18 – tent.)
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Fuel-Efficient marine propulsors …Must comply with new EEDI (Energy Efficiency Design Index)
regulations on CO2 emissions from newly built ships
Contra-rotating props Ducted prop8/24/2017- OEG @ UT Austin
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…and some water-turbines
(used to generate energy from ocean currents)
Twin turbines (each 0.6 MW)
pulled out of the sea for
maintenance
8/24/2017- OEG @ UT Austin
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For high-speed propellers
cavitation is often inevitableSheet
CavityTip vortex
•Cavitation can accelerate erosion of blades, produce
noise, or result in sudden loss of thrust
•However, allowing for some cavitation can increase
efficiency8/24/2017- OEG @ UT Austin
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Rotating components interacting with stationary ones
(propeller) (rudder)
Tip vortex
8/24/2017- OEG @ UT Austin
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Two methods to model flow
BEM can only handle the inviscid part of the flow (i.e. NOT
very close to boundaries). The effects of viscosity are
included via coupling with integral boundary layer methods
FVM needs a very large number of cells to resolve the
whole domain (especially the boundary layer) within
acceptable accuracy
Boundary Element (or Panel) Method
(addressed in CE380P.4)
Finite Volume Method
(addressed in CE380T)
8/24/2017- OEG @ UT Austin
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
0.4
0.5
0.6
0.7
0.8
0.9
0.2 0.4 0.6 0.8 1
Full wake alignment
Exp
RANS
PSF-2 wake
Advance ratio (J)
Torq
ue
Co
eff
icie
nt
(KQ
)
RANS failed beyond this point
We want a model
which can improve
our existing method
by this much!
Panel method : 5 mins on a Laptop
RANS: 8 hrs on 24 CPUs.
Correct position of
“force-free” trailing wake
improves prediction of performance
PREDICTION OF PROPELLER PERFORMANCE AT HIGH
LOADING (TIAN & KINNAS, INT. JOURNAL OF ROTATING MACHINERY, 2012)
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Ocean Eng. Group, CAEE
University of Texas at Austin
A VISCOUS VORTICITY EQUATION (VISVE) MODEL FOR
PROPELLER AT OFF-DESIGN WITH LEADING EDGE VORTEX (LEV)
8/24/2017- OEG @ UT Austin
Tip vortex
Leading edge vortex (LEV)
Tian, PhD
OEG/UT 2014
Tian & Kinnas;
SMP’15
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Ocean Eng. Group, CAEE
University of Texas at Austin
NEW METHOD FOR EVALUATION OF LE SEPARATION
2D hydrofoil at high angle of attack
8/24/2017- OEG @ UT Austin
x
y
0 0.2 0.4 0.6 0.8 1
-0.4
-0.2
0
0.2
0.4
Navier-Stokes Domain
VISVE Domain
This region is
NOT necessary
and will be
replaced.
# of layers of
cells can also
be reduced.
60k cells
7k cells (can be
reduced further)
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Ocean Eng. Group, CAEE
University of Texas at Austin
RESULTS
2D hydrofoil at high angle of attack
8/24/2017- OEG @ UT Austin
VISVE Navier-Stokes (RANS)
t=0.3s
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
J=0.3
RESULTS (VORTICITY STRENGTH IS SHOWN IN COLOR)
A Square Tip Propeller (left) and a Round Tip Propeller (right)
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Ocean Eng. Group, CAEE
University of Texas at Austin
APPLICATION ON DUCTED PROPELLERS
CORRELATION OF OUR METHODS WITH RANS SOLVERS
(STAR-CCM+ & FLUENT)
8/24/2017- OEG @ UT Austin
(Kinnas, Su, Du, Kim; SNH 2016)
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
Mesh conditions in fully 3-D viscous simulation
Polyhedral cells and hexahedral cells are
respectively utilized in the rotating region
and static region.
Periodic interfaces are applied, making only
a quarter of the whole domain necessary for
the simulation.
mesh of periodic domain
mesh around blade station r/R=0.60mesh around duct
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
Correlation of pressure distribution (J_s=0.5) at different
radial sections r/R=0.5927 (left), and r/R=0.9305 (right
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
Comparison of running times
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Ocean Eng. Group, CAEE
University of Texas at Austin 8/24/2017- OEG @ UT Austin
Ship Hull – Propeller – Rudder Interaction(Su & Kinnas, Journal of Ship Research, 2017 – in press)
Propeller Inflow
Propeller Thrust &
Torque Prediction
Axial Velocity/Ship Speed
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New design method produces more efficient turbines
(Menendez, MS, OEG 13, Menendez & Kinnas JSR’14)
Fully Aligned Wake (FWA)
Non- or partially
aligned wake
8/24/2017- OEG @ UT
Austin
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Deepwater Systems
OFFSHORE PLATFORMS
Fixed
Platform
(FP)
(to 1650 ft) Compliant
Tower
(CT)
(1500-3000 ft)Sea Star
(SStar)
(600-3000 ft)
Floating
Production
Systems
(FPS)
(1500-6000 ft)
Tension
Leg
Platform
(TLP)
(1500-7000 ft)
Subsea
System
(SS)
(to 7000 ft)
SPAR
Platform
(SP)
(2000-10,000 ft)
Source: Bureau of Ocean Energy Management
Currents
Waves
8/24/2017- OEG @ UT
Austin
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Experiment and simulation of flow around cylinder subject to wave
(G. Wang; MS, OEG, 2015)
UT’s flume and Particle Image
Velocimetry (PIV) system
8/24/2017- OEG @ UT
Austin
Simulation of viscous flow inside
flume (using ANSYS/Fluent)
• Reynolds-Averaged Navier-
Stokes (RANS)
• Large Eddy Simulation (LES)
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8/24/2017- OEG @ UT
Austin
Measured vs. predicted
velocity over time
Direction of inflow
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8/24/2017- OEG @ UT
Austin
Measured vs. computed
time averaged velocities
(Reynolds stresses)
LES appears to do a much
better job than RANS in
simulating the viscous
flow
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2017-18 Opportunities in OEG:
10 hour grader (for CE358 class - committed)
MS Thesis in OE on the topics listed
(unfunded) – Requires strong background in
Fluid Mechanics, Advanced Calculus, and
Computational Methods