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cDynamics AS NAFEMS Nordic 2018 Presentation

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cDynamics AS NAFEMS Nordic 2018 Presentation

  1. 1. Fluid-Structure Interaction Analysis of Composite Bow Foil MARINE || COMPOSITES || RENEWABLES || SUBSEA
  2. 2. CDYNAMICS COMPANY INTRO • Located in Kristiansand, Norway • Founded in 2015 as a supplier of analysis services to marine industry • 5 co-workers • Expertise in composites and fluid dynamics • Applicable skills in CFD and FEA to any engineering problem http://cdynamics.no/
  3. 3. Wavefoil • Retractable bow foil that dampens heave and pitch motion • Decreases fuel consumption in head-on waves. Eirik Bøckmann, Phd thesis 2015 wavefoil.com
  4. 4. Project objectives • Structural dimensioning of Wavefoil against slamming loads • Find importance of hydroelasticity by comparing three approaches: 1. Quasi-static: Quasi-static structural analysis using pressure from rigid structure CFD 2. Dynamic (One-way coupling): Dynamic structural analysis using pressure from rigid structure CFD 3. FSI (two-way coupling): Dynamic analysis where structural deformation affects the fluid pressure.
  5. 5. • Free body drop: Vertical DOF is free. • Large mass of ship -> nearly constant velocity impact at 6 m/s • Flat water surface • 10 deg deadrise angle FSI model setup – CFD model
  6. 6. Property Value Software StarCCM+ Timestep 2.5e-5 - 1e-4 s Cell size at foil 10 mm Mesh size 500000 cells Viscous regime Laminar Co-simulation Implicit Mesh motion Overset+morphing Equation of state Compressible (both air and water) FSI model setup – CFD model
  7. 7. Time step convergence 0 0.2 0.4 0.6 0.8 1 1.2 0.00E+00 2.00E-05 4.00E-05 6.00E-05 8.00E-05 1.00E-04 1.20E-04 Verticalforce/CFL Timestep [s] Vertical force CFL 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 0.035 0.037 0.039 0.041 0.043 0.045 0.047 Verticalforce[MN] Time [s] dt=1e-4 dt=2.5e-5 dt=1e-5 • CFL < 1 gives sufficient accuracy on forces (average of pressure)
  8. 8. Property Value Software Abaqus Element size ~20 mm No. of elements 23000 Element type Linear quadrilateral Non-linear geometry No Timestep 1e-4 s Boundary condition: vertical direction is free. Other DOFs are fixed -> conservative FSI model setup – FEA model
  9. 9. Foil structure E-glass=22.9 mm E-glass=30.4 mm E-glass=37.8 mm 3m
  10. 10. Validation of FSI model • FSI setup with StarCCM+ and Abaqus in co-simulation is validated against drop tests of cantilever plates by Panciroli et al. 2012. Experimental setup from Panciroli et al. 2012
  11. 11. Validation of FSI model • FSI setup with StarCCM+ and Abaqus in co-simulation is validated against drop tests of cantilever plates by Panciroli et al. 2012.
  12. 12. Validation of FSI model Experimental data from Panciroli et al. 2012 -0.002 -0.0015 -0.001 -0.0005 0 0.0005 0.001 0.0015 0.002 0.0025 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Strain[%] Time[s] FSI (CFD) Experiment (Panciroli) • FSI setup with StarCCM+ and Abaqus in co-simulation is validated against drop tests of cantilever plates by Panciroli et al. 2012.
  13. 13. Results - compressible air effects • FSI versus quasi-static yields reduction of bending moment of 50% • Dynamic vs quasi-static yields reduction of bending moment of 50% -0.9 -0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06 0.065 Verticalforce[MN] Time [s] Quasi-static Quasi-static (incompressible air) • Compressible air effects are relevant • Part of Hull adjacent to foil needs to be included in CFD model
  14. 14. • FSI approach renders vertical force about 40% of quasi-static • Dynamic approach gives spurious oscillations because of no damping -0.9 -0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06 0.065Verticalforce[MN] Time [s] Quasi-static FSI Dynamic Results – vertical force
  15. 15. • FSI bending moment about 40% of quasi-static • Dynamic bending moment about 60% of quasi-static • Incompressible air effects yields only 10% difference to FSI bending moment -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06 0.065 Bendingmoment[MNm] Time [s] Quasi-static FSI (two-way coupling) Dynamic (One-way coupling) FSI (incompressible) Results – bending moment
  16. 16. Results
  17. 17. Tsai-Wu utilization for FSI approach Tsai-Wu utilization for Quasi-static approach Results – Tsai-Wu
  18. 18. The role of hydroelasticity Hydroelasticity parameter: R = 𝑙𝑜𝑎𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (𝑟𝑖𝑔𝑖𝑑 𝑠𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒) 𝑝𝑒𝑟𝑖𝑜𝑑 𝑜𝑓 1𝑠𝑡 𝑑𝑟𝑦/𝑤𝑒𝑡 𝑚𝑜𝑑𝑒 R < 1-2: hydroelastic effects are relevant (Faltinsen 1999, Bereznitski 2001) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 Normalizedresponse R Theoretical dynamic response (DAF) Quasi-static Faltinsen 1999 Panciroli 2001
  19. 19. The role of hydroelasticity Dry mode 1: 34Hz Hydroelasticity parameter: R = 𝑙𝑜𝑎𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (𝑟𝑖𝑔𝑖𝑑 𝑠𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒) 𝑝𝑒𝑟𝑖𝑜𝑑 𝑜𝑓 1𝑠𝑡 𝑑𝑟𝑦/𝑤𝑒𝑡 𝑚𝑜𝑑𝑒 R < 1-2: hydroelastic effects are relevant (Faltinsen 1999, Bereznitski 2001)
  20. 20. The role of hydroelasticity -0.9 -0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 0.02 0.022 0.024 0.026 0.028 0.03 0.032 0.034 0.036 0.038 0.04 0.042 0.044 0.046 0.048 0.05 0.052 0.054 0.056 0.058 0.06 0.062 0.064 Verticalforce[MN] Time [s] Quasi-static Duration=5-10 ms R=0.2-0.3 Hydroelasticity parameter: R = 𝑙𝑜𝑎𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (𝑟𝑖𝑔𝑖𝑑 𝑠𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒) 𝑝𝑒𝑟𝑖𝑜𝑑 𝑜𝑓 1𝑠𝑡 𝑑𝑟𝑦/𝑤𝑒𝑡 𝑚𝑜𝑑𝑒 R < 1-2: hydroelastic effects are relevant (Faltinsen 1999, Bereznitski 2001)
  21. 21. The role of hydroelasticity 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 Normalizedresponse R Theoretical dynamic response Quasi-static Faltinsen 1999 Panciroli 2001 FSI (bending moment) Dynamic (bending moment) Dynamic (tip deformation) Hydroelasticity parameter: R = 𝑙𝑜𝑎𝑑 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (𝑟𝑖𝑔𝑖𝑑 𝑠𝑡𝑟𝑢𝑐𝑡𝑢𝑟𝑒) 𝑝𝑒𝑟𝑖𝑜𝑑 𝑜𝑓 1𝑠𝑡 𝑑𝑟𝑦/𝑤𝑒𝑡 𝑚𝑜𝑑𝑒 R < 1-2: hydroelastic effects are relevant (Faltinsen 1999, Bereznitski 2001)
  22. 22. Conclusions • FSI and dynamic analysis of Wavefoil yield considerable reduction in laminate utilization compared to quasi-static analysis -> – Lighter structure – Easier production • Compressible air effects are only minor in FSI approach • Dynamic approach can be a good trade-off between CPU time/cost and accuracy
  23. 23. THANK YOU FOR YOUR TIME MARINE || COMPOSITES || RENEWABLES || SUBSEA post@cdynamics.Contact

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