Fluid structure interaction analysis: vortex shedding induced vibrations
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This document summarizes Nicolò Di Domenico's master's thesis analyzing fluid structure interaction and vortex shedding induced vibrations. It investigates these phenomena for a NACA 0009 hydrofoil using computational fluid dynamics and finite element analysis with a radial basis function mesh morphing technique. The analysis captures lock-in and lock-off behavior for the hydrofoil by evaluating frequencies, lift coefficients, and turbulent kinetic energy at different inlet velocities, matching experimental data. The radial basis function method allows simulations to be run around 12 times faster than a traditional two-way fluid structure interaction approach.
Fluid structure interaction analysis: vortex shedding induced vibrations
- 1. University of Rome Tor Vergata Engineering macro-area Master thesis in mechanical engineering Advisor: Prof. Marco Evangelos Biancolini Co-Advisor: Andy Wade (ANSYS-UK) Tobias Berg (ANSYS-Sweden) Candidate: Nicolò Di Domenico Fluid structure interaction analysis: vortex shedding induced vibrations.
- 2. ‹N›Nicolò Di Domenico 2 AEROELASTICITY «The study of the mutual interaction that takes place within the triangle of the inertial, elastic, and aerodynamic forces acting on structural members exposed to an airstream, and the influence of this study on design». (Collar, 1947)
- 3. ‹N›Nicolò Di Domenico 3 AEROELASTICITY «The study of the mutual interaction that takes place within the triangle of the inertial, elastic, and aerodynamic forces acting on structural members exposed to an airstream, and the influence of this study on design». (Collar, 1947) Static phenomena
- 4. ‹N›Nicolò Di Domenico 4 AEROELASTICITY «The study of the mutual interaction that takes place within the triangle of the inertial, elastic, and aerodynamic forces acting on structural members exposed to an airstream, and the influence of this study on design». (Collar, 1947) Static phenomena Dynamic phenomena
- 5. ‹N› 5 VORTEX SHEDDING «Big whorls have little whorls, Which feed on their velocity; And little whorls have lesser whorls, and so on to viscosity». (L.F.Richardson) Nicolò Di Domenico
- 6. ‹N› 6 VORTICES INDUCED VIBRATIONS Fluctuant vortices affect the pressure field: side forces, moments; noise. Periodic stress System dynamic response + Takoma narrow bridge, US, 1940 Nicolò Di Domenico
- 7. ‹N›7 VORTICES INDUCED VIBRATIONS Fluctuant vortices affect the pressure field: side forces, moments; noise. Periodic stress System dynamic response + Fatigue and instability problems Lock in Takoma narrow bridge, US, 1940 Nicolò Di Domenico
- 8. ‹N› 8 WORK GOALS • NACA 0009 hydrofoil analysis; • Obtain a good fluid structure coupling; • Simplify the fsi approaches; • Validate the case study with experimental results. Nicolò Di Domenico
- 9. ‹N› 9 NACA 0009 HYDROFOIL • Thickness law: Nicolò Di Domenico
- 10. ‹N› 10 TOOLS AND METHODS RBF Morph ANSYS Mechanical System Coupling ANSYS FluentANSYS Fluent Nicolò Di Domenico
- 11. ‹N›11 TOOLS AND METHODS FSI: two way RBF MorphANSYS Mechanical System Coupling ANSYS Fluent ANSYS Fluent • Bidirectional process; • Mesh regeneration. • Radial Basis Functions; • Modal theory; • Only one analysis software; • Mesh morphing. FSI: modal superposition Nicolò Di Domenico
- 12. ‹N› 12 MULTI MORPH MODAL SUPERPOSITION • Modal analysis: 1133.8 Hz 1587.1 Hz 3660.9 Hz Nicolò Di Domenico
- 13. ‹N› 13 • Modal analysis • RBF Morph: 1. Source points definition and their displacement Points: 11052 MULTI MORPH MODAL SUPERPOSITION Interpolating function: FEM CFD Nicolò Di Domenico
- 14. ‹N›14 • Modal analysis • RBF Morph: 1. Source points definition and their displacement Points: 11052 MULTI MORPH MODAL SUPERPOSITION Interpolating function: FEM CFD Nicolò Di Domenico
- 15. Polinomial correction for the rigid motions compatibility ‹N›15 • Modal analysis • RBF Morph: 1. Source points definition and their displacement Points: 11052 MULTI MORPH MODAL SUPERPOSITION Interpolating function: FEM CFD Nicolò Di Domenico
- 16. ‹N› 16 • Modal analysis • RBF Morph: 2. Deformation’s volume and morphing effect Radius 0,15 m # Points 557 Lencap > Lala MULTI MORPH MODAL SUPERPOSITION Range of action and interest area around the source points: Mesh morphing Nicolò Di Domenico
- 17. ‹N› 17 • Modal analysis • RBF Morph • Fluid dynamics analysis: Inlet Wall Outlet RANS SST k-ω model Time step 2e-5 Iterations per time step 5 Number of time step 10000 Boundary conditions Velocity 12÷22 m/s Pressure 101325 Pa Density 998 kg/m3 Temperature 288,15 K Kinematic viscosity 10-6 mm2/s MULTI MORPH MODAL SUPERPOSITION Nicolò Di Domenico
- 18. ‹N› 18 MULTI MORPH MODAL SUPERPOSITION RBF Morph is fully integrated in Fluent and at any time step it resolves the equation in modal form Dynamic model it follows Journal file Nicolò Di Domenico
- 20. ‹N› • Water added mass effect and damping of the medium; • Free oscillations induced by an initial deformation; • RANS SST k-ω: stationary fluid. 20 MODES ANALYSIS UNDER WATER Air case Water case Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 1133.8 Hz 1587.1 Hz 3660.9 Hz 3917.7 Hz 5936.6 Hz 6789.6 Hz Mode 1 Mode 2 Mode 3 Mode 4 891.9 Hz 1118.8 Hz 1619.6 Hz 2902.7 Hz Nicolò Di Domenico
- 21. ‹N› 21 LOCK IN • Probe coordinates (0.08000 m, 0.03788 m, 0.1125 m); • Dominant frequency 909.91 Hz; • Inlet velocity16 m/s. Nicolò Di Domenico
- 22. ‹N› 22 LOCK IN • Reynolds number • Lift coefficient Nicolò Di Domenico Turbulent kinetic energy (t=0,2s)
- 23. ‹N› 23 LOCK OFF • Probe coordinates (0.08000 m, 0.03788 m, 0.1125 m); • Dominant frequency 1209.9 Hz; • Inlet velocity 22 m/s. Nicolò Di Domenico
- 24. ‹N› 24 LOCK OFF • Reynolds number • Lift coefficient Nicolò Di Domenico Turbulent kinetic energy (t=0,2s)
- 25. ‹N› 25 RESULTS ANALYSIS Nicolò Di Domenico
- 26. ‹N› 26 RESULTS ANALYSIS Experimental data Lock In • Cref ≅ 16 m/s • fs ≅ 900 Hz Lock Off • Cref ≅ 22 m/s • fs ≅ 1200 Hz Nicolò Di Domenico
- 27. ‹N› 27 DATA COMPARISON: LOCK IN RBF MorphTwo way 35 h to simulate 0.1s of the phenomenon on a calculator with 144 cores 37 h to simulate 0.2s of the phenomenon on a calculator with da 32 cores Nicolò Di Domenico
- 28. ‹N› 28 DATA COMPARISON: LOCK OFF RBF MorphTwo way 35 h to simulate 0.1s of the phenomenon on a calculator with 144 cores 37 h to simulate 0.2s of the phenomenon on a calculator with da 32 cores Nicolò Di Domenico
- 29. ‹N› 29 CONCLUSIONS • Good fluid structure coupling in terms of induced vibrations; • With the same calculator RBF Morph allows a speed up factor ≈ 12 compared to the two way method; • General approach to calculate natural frequencies under water; • The modal superposition method with mesh morphing detects the renonance physics; • Boundary conditions strongly affect the vortex shedding phenomen; Nicolò Di Domenico
- 30. ‹N› 30 FUTURE DEVELOPMENTS • Overcome the limits of the RANS model (strong influence of the turbulent model); • Wake control (CFD): numerical solutions to reduce the phenomenon, trying to limit the drag penalty; • Wake control (FEM): numerical solutions focused on the shape optimization of the bodies affected by these phenomena; • Industrial numerical applications: mesh morphing requires less computational costs than remeshing; • Perform the experiment in laboratory, using different material and holding the initial geometry (i.e. Orthotropic materials). Nicolò Di Domenico
- 31. THANK YOU FOR THE ATTENTION