1. STAR-CCM+ Validations and Applications at NSWCCD
Minyee Jiang,
Naval Surface Warfare Center at Carderock, US NAVY
STAR Global Conference
Berlin Germany March 7, 2017
DISTRIBUTION A. Approved for public release: distribution unlimited.

2. Outline Validation: Application:
NSWCCD Wedge Drop Impact Load Analysis
USNA Planing Hull Validation
Athena Semi-Planing Hull Validation
Application:
SPPC free surface / wave impact
Project Sponsor: Dr. Robert A. Brizzolara, ONR Code 333, US NAVY
03/07/2017

3. Wedge Drop Impact Load Analysis
Goal: Validate CFD tools for slam load prediction
Pressure gauge
Strain gauge
vertical drops 6” and 10” from water surface
03/07/2017

4. Geometry (Computational Model)
Pressure gauge
Strain gauge
center
circular area of pressure gauge d=0.14” ( in2)
square area of strain gauge 1.26”X1.26” (1.588 in2)
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5. Computational Grid Most resolved domain has 19M cells panels
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6. Chosen Time Step and Its Effect on Maximum Impact Load on the Wedge (psi)
dt = second
Peak impact Load (psi)
1e-3 s
3.245
1e-4 s
10.38
1e-5 s
22.30
The smallest time step was chosen because the sample rate in the drop test is 20K Hz, therefore time step smaller than 1e-5 second is not included in this study.
03/07/2017

7. Instantaneous pressure contours
Maximum pressure
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8. Pressure Wave Propagation
Early Stage of impact
Late Stage of impact
Bow shape wave front
Vertical wave front
03/07/2017

9. Instantaneous Flow Detail (free surface)
Free Surface (red is water)
Velocity Magnitude Plot
Vmax = 24+ m/s
Spread
Maximum pressure
Maximum pressure
03/07/2017

10. Comparison of the Pressure Distribution on the Wedge (Pressure Gauge)
center
Finer Mesh near the pressure gauges
Row Average
03/07/2017

11. Comparison of the Pressure Distribution on the Wedge (Strain Gauge)
center
Row Average
03/07/2017

12. USNA Planing Hull Validation
Performed RANS simulations of three planing hulls in calm water to validate STAR-CCM+ capabilities to predict forces, moments, sinkage, trim, and wet length.
Compared STAR-CCM+ results against test data.
03/07/2017
DISTRIBUTION A. Approved for public release: distribution unlimited.

13. USNA Test Setup Turbulence Model: k-ω SST
Volume of Fluid (VOF) was used in the two-phase flow computations
Trim-mesh topology was used for all simulations in this task for better mesh control near the free surface
Beam: 1.48 feet
For heavy displacement (55 lb)
For light displacement (30 lb)
Mesh size: 6.5M cell full boat
03/07/2017

14. USNA Wet Area and Spray
USNA 15 degree 20 fps
STAR-CCM+
03/07/2017

15. Heave and Trim Comparison CFD vs. USNA Test Data
The predicted trim angles for the free run cases have the same trend with the measured data. The deviation is about 0.5 degrees for all speeds
The predicted heave for the free run cases also agrees with the measured data with about 0.2 inch deviation from the measured data
03/07/2017

16. Force Comparison CFD vs. USNA Test Data
Heavy Displacement
V=30 fps
KG at 5.29” from keel
Lift (lb) agrees well for all angles
Roll moment (lb-in) agrees well for small heel angles but deviates from test data at heel angles greater than 15 degrees.
Insufficient mesh near the boat, which did not capture the detail of the spread may have caused large deviation for the high heel angles.
03/07/2017

17. Wet Length Comparison CFD vs. USNA Test Data
The wet length prediction for the Lk (keel), Lc (starboard) and Lc (port) agree quite well.
The wet length is calculated from the transom to the most forward wetted point on the hull.
03/07/2017

18. Experimental and Computational Comparisons of the R/V Athena in Calm Water
Evan J. Lee, Anne M. Fullerton, Jayson S. Geiser, Christine C. Schleicher, Craig F. Merrill, Charles R. Weil, Minyee Jiang, Van Lien, Jason R. Morin
(Naval Surface Warfare Center Carderock Division)
Fredrick Stern, Maysam Mousaviraad
(IIHR – Hydroscience and Engineering, University of Iowa)
September 15, 2016
Distribution A: Distribution Unlimited

19. Objective
Current structural design methods for high speed naval craft rely heavily on empiricism. Though these methods have been employed reliably for a number of years, it is likely that an unknown level of conservatism exists in both global and local impact loads to ensure the vessel’s structural design is robust.
Provide a CFD validation data set for semi-planing craft.
Resistance, sinkage, and trim measurements of a semi-planing craft in calm water over a range of displacement and semi-planing speeds
Evaluate CFD predictions in their ability to predict calm water performance
Develop an improved understanding of the dynamic response of semi-planing and planing craft in a seaway
03/07/2017

20. Outline Objective Model Test CFD Comparison of CFD and Experiments
Conclusions
03/07/2017

21. Model 5365
The publicly releasable high speed, semi-planing hull form Naval Surface Warfare Center Carderock Division (NSWCCD) Model 5365 (R/V Athena) was chosen to facilitate public release of results
Model 5365 is a 8.25 scale model of the R/V Athena
R/V Athena is a converted PG-84 Asheville-class patrol gunboat which is operated out of Naval Surface Warfare Center - Panama City Division as a high speed research vessel
03/07/2017

22. Model Parameters Model Speed m/s Fr 1.0 0.14 1.6 0.22 1.9 0.25 2.2
0.29
3.2
0.43
4.6
0.62
6.3
0.84
03/07/2017

23. CFD CFDShip-Iowa STAR-CCM+ University of Iowa NSWCCD Free Surface
Single-phase level-set
Turbulence Model
Blended k-ε/k-ω
Ship Motion
Curvilinear dynamic overset grids
NSWCCD
Free Surface
Volume of Fluid
Turbulence Model
k-ω
Ship Motion
Morphing and overset grids
Codes selected for comparison used to study verification and validation process
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24. Resistance
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25. Trim Angle
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26. Sinkage at the Towpost
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27. Conclusions
The agreement between the predictions of STAR-CCM+ and CFDShip-Iowa is encouraging, and supports using these codes to predict performance in waves for future work.
03/07/2017

28. SPPC Ship Load Prediction in the Wave Field of Multiple Irregular Waves Combination
Goal: To demonstrate the application of STAR-CCM+ (RANS code) to local impact pressure predictions on the Semi-Planing Patrol Craft (SPPC) for design evaluations.
Generate single/multiple direction irregular wave fields
Use appropriate time step to determine peak impact loads
03/07/2017
DISTRIBUTION A. Approved for public release: distribution unlimited.

29. Motions/Loads for matrix cases
Wave Field Generation
LAMP
STAR-CCM+
Motions/Loads for matrix cases
Critical Wave Events
Strong waves created with LAMP (2D, potential flow code)
Critical events are chosen to be mapped into STAR-CCM+ (3D, RANS)
This process is now automatic.
It has been verified by comparing the wave elevation at inlet and CG position
At the inlet boundary, wave field agreed from the beginning of the simulation.
As waves propagated into the computational domain, in this case, it took about 10 seconds for these waves to develop before reasonable wave field is generated at the c.g. location. Small discrepancy is expected in the numerical model.
03/07/2017

30. Irregular Wave Creation for Multiple Wave Direction
LAMP output to STAR-CCM+
Java Script
STAR-CCM+ input file
03/07/2017

31. Multiple Directions Wave Field and Wave Profile
Wave field with multiple wave directions
Wave profile at y plane
03/07/2017

32. Time Step Determination
General Process in determining local impact loads in STAR-CCM+
Based on previous time step study for the wedge drop and other combatant craft, an appropriate time step size is dt = s.
Run through the simulations using a fairly larger time step (0.01s) to identify the peak impact events.
Restart at files saved for every second to simplify rerun process.
To capture peak impact load more accurately time step size is gradually reduced (to preserve a stable solution) from 0.01s to s during rerun impact event.
The smallest time step is used for a short duration before and after the peak impacts occur.
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33. The Time Step Used During Impact
Simulation Time
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34. SPPC in Waves Impact load on the breakwater
Time history of pitch and roll angles
03/07/2017

35. Conclusion
STAR-CCM+ has been evaluated as a numerical tool for predicting wave impact loads.
Series of validation projects have been conducted and agreement with experimental data is appropriate.
Newer versions have the feature to generate complex critical wave fields for predicting wave impact to the vessels.
In the current project, static structural analysis has been performed after CFD calculations have been completed.
Explicit coupling with ABAQUS has been done in a separate study.
Implicit coupling between STAR-CCM+ and ABAQUS can be performed as well.
03/07/2017