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.

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

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

Geometry (Computational Model) Pressure gauge Strain gauge center circular area of pressure gauge d=0.14” (0.0154 in2) square area of strain gauge 1.26”X1.26” (1.588 in2) 03/07/2017

Computational Grid Most resolved domain has 19M cells panels 03/07/2017

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

Instantaneous pressure contours Maximum pressure 03/07/2017

Pressure Wave Propagation Early Stage of impact Late Stage of impact Bow shape wave front Vertical wave front 03/07/2017

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

Comparison of the Pressure Distribution on the Wedge (Pressure Gauge) center 4 3 2 1 Finer Mesh near the pressure gauges Row Average 03/07/2017

Comparison of the Pressure Distribution on the Wedge (Strain Gauge) center 1 2 3 4 Row Average 03/07/2017

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.

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

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

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

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

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

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

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

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

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

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

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 03/07/2017

Resistance 03/07/2017

Trim Angle 03/07/2017

Sinkage at the Towpost 03/07/2017

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

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.

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

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

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

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 = 0.0005s. 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 0.0005s during rerun impact event. The smallest time step is used for a short duration before and after the peak impacts occur. 03/07/2017

The Time Step Used During Impact Simulation Time 03/07/2017

SPPC in Waves Impact load on the breakwater Time history of pitch and roll angles 03/07/2017

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