REDE TEMTICA DE ESTRUTURAS SUBMARINAS Riser Dynamics experiments

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Riser Dynamics: experiments with small scale models Celso P. Pesce Escola Politécnica University of São Paulo Ten-Years Anniversary Celebration Workshop April 29 -30, 2013, Rio de Janeiro, Brazil LIFE&MO - Laboratório de Interação Fluido-Estrutura e Mecânica Offshore NDF – Núcleo de Dinâmica e Fluidos LMC – Laboratório de Mecânica Computacional TPN – Tanque de Provas Numérico IPT – Instituto de Pesquisas Tecnológicas Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Context • R&D Project: – Nonlinear Dynamics of Risers: hydroelastic and contact nonlinear interactions • Program (ANP): – Petrobras - Submarine Structures Research Network – Petrobras – Arquimedes Research Network • Duration: – 24 + 12 months (03/2010 – 02/2013) Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Research Team • USP: – Leading researchers: Celso Pesce, LIFE&MO Clóvis Martins, LIFE&MO Carlos Mazzilli, LMC André Fujarra, TPN – Experiments: Guilherme Franzini, Rodolfo Gonçalves Felipe Rateiro, Rafael Salles – Analytical and Numerical Models Fernanda Takafuji, Nicolau Galan Neto Guilherme Monticelli, Eduardo Malta • Catenary riser model at TPN-Lab Petrobras: – Pedro Mendes, CENPES – Ricardo Franciss, CENPES Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Objectives • Further researches on Non-Linear Dynamics of Risers, with emphasis on nonlinear interactions of hydro-elastic and contact natures, through analytical, numerical and nonlinear dynamics techniques. • To estabilish methodology for small scale riser model experiments • To conduct experiments with small scale riser models in a towing tank, in a ocean basin and in a recirculating water channel, observing and analysing nonlinear dynamic interactions. • Giving Petrobras R&D team new insights on global dynamics analysis procedures and aiming at improving the design methodology of this kind of structures. Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Riser dynamics state-of-art in 2009 -10 • Structural dynamics: – Formulation and numerical methods: • • On going Nonlinear boundary conditions at riser top: Nonlinear boundary conditions a TDZ: – Riser-soil elastic interaction: – Riser-soil nonlinear contact interaction: OK on going – Clashing and impact loading: on going – Instabilities and post-critical behavior: ongoing Riser dynamics: • concomitant and intervenient actions - of VIV and motions Hydroelastic interactions: imposed by the floating unit - have not been fully explored, – VIV: on going deserving special efforts towards further understanding. • Fundamentals: still open • • Mitigation: Multiple scales nonlinear interactions: – Wake interferences and instabilities: – Internal flow interactions: Escola Politécnica on going still open on going Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Project Scope 1. Mathematical modeling of riser dynamics through reduction order techniques, using the concept of nonlinear modes. 2. Analysis of dynamic responses to parametric excitations and internal resonances, caused by multiple scale interactions of motions imposed by the floating unity and VIV. 3. Typical case studies, with focus on nonlinear riser dynamics. 4. Dynamic experiments with small scale riser models. Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Focus: Experimental Task #4 4. Dynamic experiments with small scale riser models: a. Fundamental experiments: VIV of rigid and flexible cylinders mounted on a modulated stiffness apparatus OK b. Small scale riser modeling methodology OK c. Experiments with a semi-immersed vertical riser model in the NDF recirculating water channel OK d. Experiments with a catenary riser model in TPN-HC Basin; OK e. Experiments with a vertical riser model in IPT towing tank; OK f. Experiments with a catenary riser model in IPT towing tank OK Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Focus: Experimental Task #4 4. e Experiments with a vertical riser model in IPT towing tank : a. VIV experiments – relative current induced by towing i. Excitation up to the fourth vibration mode ii. Spanwise spectral and time amplitude analysis iii. Modal decomposition analysis b. Dynamic response to pure sinusoidal vertical displacement imposed to the top – no current i. Excitation at integer and fractionary frequency ratios ii. Spanwise spectral and time amplitude analysis iii. Subharmonic and parametric excitations c. Concomitant top displacement and current i. Excitation at integer and fractionary frequency ratios ii. Spanwise spectral and time amplitude analysis iii. Subharmonic and parametric excitations Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Focus: Experimental Task #4 4. f Experiments with a catenary riser model in IPT towing tank : Two configurations – longitudinal and transversal to towing a. VIV experiments – relative current induced by towing i. Excitation up to the fourth vibration mode ii. Spanwise spectral and time amplitude analysis iii. Modal decomposition analysis b. Dynamic response to pure sinusoidal vertical displacement imposed to the top – no current i. Excitation at integer and fractionary frequency ratios ii. Spanwise spectral and time amplitude analysis iii. Subharmonic and parametric excitations c. Concomitant top displacement and current i. Excitation at integer and fractionary frequency ratios ii. Spanwise spectral and time amplitude analysis iii. Subharmonic and parametric excitations Lab de Interação Fluido-Estrutura e Mecânica Escola Politécnica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Focus: Task #4 Comprehensive experimental Matrix • Vertical Riser Model: ~ 250 experimental runs! • Catenary Riser Model: ~750 experimental runs! – – Longitudinal: ~450 Transversal: ~ 300 In fact, experimental material for many years of analysis. . . • Total: - ~1000 experimental runs!! • HUGE EXPERIMENTAL DATA BASIS!! – – Phenomenology Theoretical (numerical and analytical) models benchmarking Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Focus: Experimental Task #4 • State-of-the-art instrumentation: – – • Syncronized underwater and Aerial Optical Tracking Systems: • Elastica tracked all along the riser span: – Vertical: 42 reflective targets – Longitudinal Catenary: 49 reflective targets – Transversal Catenary: 34 reflective targets. • ~ 120, 000 is the total number of cartesian coordinates time series!!! Plus: tension, towing speed, films, etc. . . Combined Analysis: – – Spanwise Fourier spectral analysis Spanwise-time amplitude analysis Modal amplitude analysis Hilbert-Huang spectral analysis Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

Table 1: Data Summary REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Innovative Riser model Made up of silicon rubber tube filled in with stainlesssteel microspheres! 1600, 00 1400, 00 1200, 00 EA (N) Rateiro et al ISOPE 2012 1800, 00 1000, 00 800, 00 600, 00 400, 00 200, 00 0 0, 5 e = 0. 1% 1 f (Hz) e = 0. 5% 1, 5 e = 1. 0% 2 Axial rigidity tests Bending stiffness tests Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Innovative Riser model This concept enabled to achieve geometric, structural and dynamic similarity with a 8 in SCR Data Internal diameter (mm) External diameter (mm) Weight in water (N/m) Axial rigidity, EA (k. N) Bending stiffness, EI (Nm²) Flexural length, λf (mm) Added mass, a=ma/m Escola Politécnica Scaled (1: 100) 1. 826 2. 191 0. 726 2. 362 1. 20 E-03 71. 0 0. 522 Designed model 15. 800 22. 200 7. 308 1. 910 8. 86 E-02 61. 0 0. 520 As built 15. 800 22. 200 7. 308 1. 0 - 1. 6 5. 60 E-02 49. 0 0. 520 Rateiro et al ISOPE 2012 Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS [. Model similarity and nondimensional group Number Froude Number Reynolds Number Not matched Strouhal Number Keulegan. Carpenter Number Structural Damping Reduced Velocity Reduced Shedding Frequency Reduced Mass Added Mass Bending Stiffness Axial Stiffness Rateiro et al ISOPE 2012 Escola Politécnica Soil Stiffness Symbol and definition Representation Dynamic motion in waves Viscous forces Vortex shedding frequency Inertial forces vs. drag forces Linear structural damping Normalized velocity in VIV Vortex shedding normalized frequency Riser mass vs. displaced mass Added mass vs. riser mass Bending vs. geometrical stiffness Axial vs. geometrical stiffness Soil vs. bending and geometrical stiffness Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS State-of-the-art measuring system • Syncronized Underwater and Aerial Optical Tracking Systems: Elastica tracked all along the riser span: Vertical: 42 reflective targets Longitudinal Catenary: 49 reflective targets Transversal Catenary: 34 reflective targets. Vertical driving mechanism Aerial cameras Submerged cameras ~ 120, 000 is the total number of cartesian coordinates time series!!! Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Experimental set up Vertical model “Transversal” Catenary model “Longitudinal” Catenary model Towed false bottom Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS IPT – Towing Tank 200 x 6 x 4 m Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Riser model dynamics Illustrative Analysis Results: Vertical Riser Model L= 2552 mm D=22. 2 mm L/D=115 m*=3. 48 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Riser Model Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: decaying tests Scalograms Spanwise amplitude vs time Modal decomposition 1 st mode z=3. 4% Spanwise amplitude spectrum 2 nd mode z=1. 7% Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: driven by top motion Transversal motion caused by vertical motiont at top: Az/L=1%; Az/D=1. 15 subharmonics f. T : f 1 Escola Politécnica 1: 3 1: 2 2: 3 Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: driven by top motion Transversal motion caused by vertical motiont at top: Az/L=1%; Az/D=1. 15 Mathieu type bifurcations 1: 1 Escola Politécnica 2: 1 3: 1 Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV Current only: classical VIV In-line: Ax/D Collapse into a single curve Cross: Ay/D Modal reduced velocity Modal Amplitude response Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV Multi-modal response Single mode response (1 st mode) Ay/D Ax/D Vr = 5. 6 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV 3 rd mode at 4 th frequency!! 2 nd mode response Ay/D Ax/D Vr =12. 2 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV + imposed motion Ay/D VIV 1 st mode response at lock-in peak VIV + 1: 3 1 st mode reinforced VIV + 1: 1 1 st mode and superharmonic: 1 -1/3 1 st , 2 nd and 3 rd modes VIV + 3: 1 Vr = 5. 6 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV + imposed motion Ay/D VIV 1 st mode response at lock-in peak VIV + 1: 3 1 st mode reinforced VIV + 1: 1 1 st mode and fractionary superharmonic: 1 -1/3 1 st , 2 nd and 3 rd modes VIV + 3: 1 Vr = 5. 6 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Vertical Model: VIV + imposed motion Ay/D VIV + 1: 1 2 nd mode response at lock-in peak VIV + 1: 3 1 st and 2 nd mode plus fractionary harmonics VIV + 3: 1 2 nd mode and fractionary harmonics 2 nd and 3 rd modes and cascade of frequencies: chaos Vr = 12. 2 Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary model dynamics Escola Politécnica D=22. 2 mm Illustrative Analysis Results: m*=3. 48 Catenary Riser Model Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: general characteristics Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: experimental conditions • Two configurations: LONGITUDINAL and TRANSVERSAL to the towing tank • Experiments under vertical motion imposed to the top: – 4 amplitudes; exciting frequencies covering large typical range • Experiments under current only (VIV): – By the DORSE and INTRADORSE – 0 < Vr 1 = U/f 1 D < 27 • Experiments under current and vertical motion at top: – By the. DORSE and INTRADORSE – 0 < Vr 1 = U/f 1 D < 27 – 4 amplitudes; 3 exciting frequencies covering 3 first natural frequencies Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Models: static configurations and targets Longitudinal Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Models: static configurations and targets Transversal Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Models: natural frequencies (Hz) Mode 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 POLIFLEX 0, 42 0, 70 0, 83 1, 10 1, 25 1, 52 1, 68 2, 13 2, 12 2, 59 2, 56 3, 07 3, 05 -- Experimental 0, 42 0, 72 0, 87 1, 15 1, 26 --1, 79 1, 66 2, 23 2, 22 2, 73 2, 56 3, 02 3, 19 3, 80 Longitudinal Escola Politécnica (Hz) Plane out in out in out Mode POLIFLEX 1 0, 42 2 0, 72 3 0, 84 4 1, 09 5 1, 26 6 1, 44 1 st mode is 7 1, 67 out-of-plane 8 1, 69 9 2, 13 10 2, 14 11 2, 56 12 2, 59 13 3, 05 14 3, 51 15 -- Experimental 0, 43 0, 76 0, 85 1, 18 1, 25 -1, 66 1, 77 2, 24 2, 27 2, 74 2, 71 3, 18 -3, 22 Plane out in in out in Transversal Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top VSIV: Vortex Self-Induced Vibration 2 p A/D=10 Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top 2 p A/D=10 Exciting frequency = 1 st natural frequency Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top VSIV: Vortex Self-Induced Vibration Trajectories evolve from single to multiple laces 2 p A/D=20 Trajectories measured all along the elastic line !! Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top 2 p A/D=20 Exciting frequency = 1 st natural frequency Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top Analogous to Dominant response frequencies and transversal amplitude fundamental studies with 2 p A/D=5 2 p A/D=10 rigid cylinders Lock-in V*= fe A/f. N 1 D Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: vertical motion at top Dominant response frequencies and transversal amplitude 2 p A/D=20 2 p A/D=30 Steped lock-in V*= fe A/f. N 1 D Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current by the dorse VIV Vr = 6 Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current by the dorse Vr = 6 Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current by the dorse VIV Vr = 10 Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current by the dorse Vr = 10 Rich spectrum Nitid travelling waves Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current by dorse and intradorse Dominant response frequencies and transversal amplitude Intradorse Dorse V r 1 Longitudinal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current + motion at top VSIV & VIV 2 p A/D=10 Vr = 6 Longitudinal Catenary: current by the dorse Exciting frequency = 1 st natural frequency Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current + motion at top Vr = 6 2 p A/D=10 First natural freq. Rich spectral content Longitudinal Catenary Escola Politécnica Exciting frequency = 1 st natural frequency Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: perpendicular current Dominat frequencies and amplitudes 1 st 2 nd 3 rd normal Inline = binormal tangent horizontal vertical V r 1 Transversal catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: perpendicular current VIV Vr = 12 Tranversal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: perpendicular current Vr 1 = 12 Binormal (inline) Rich composition 2 nd mode (inplane) Transversal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current + motion at top VSIV & VIV 2 p A/D=10 Vr = 12 Tranversal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Catenary Model: current + motion at top Rich composition, including low frequencies Vr = 12 2 p A/D=10 Binormal (inline) 1 st (out-ofplane) and 2 nd (inplane) modes Transversal Catenary Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Remarks Comprehensive experimental Matrix • Vertical Riser Model: ~ 250 experimental runs! • Catenary Riser Model: ~750 experimental runs! – – Longitudinal: ~450 Transversal: ~ 300 • Total: - ~1000 experimental runs!! • HUGE EXPERIMENTAL DATA BASIS!! – – – Phenomenology Theoretical (numerical and analytical) models benchmarking Concomitant and intervenient actions - of VIV and motions imposed by the floating unit – were experimentally explored. Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Conclusions • The Riser Dynamics project enabled: – Further researches on Non-Linear Dynamics of Risers, with emphasis on nonlinear interactions of hydro-elastic and contact natures, through analytical, numerical and nonlinear dynamics techniques. – To estabilish new methodology for small scale riser model experiments – To conduct innovative experiments with small scale riser models in a towing tank, in a ocean basin and in a recirculating water channel, observing and analysing nonlinear dynamic interactions. • This will provide Petrobras R&D team new insights on global dynamics analysis procedures, aiming at improving the design methodology of this kind of structures. • The main analysis results shall be eventually published, providing new knowledge and benchmarking material to the scientific community. Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica

REDE TEMÁTICA DE ESTRUTURAS SUBMARINAS Acknowledgments • The research team acknowledges: – Petrobras Submarine Structures and Arquimedes Networks – ANP – Petroleum National Agency – IPT – Technological Research Institute of São Paulo State – And, at Escola Politécnica: • TPN and NDF staffs and • Profs. Kazuo Nishimoto and Julio Meneghini Escola Politécnica Lab de Interação Fluido-Estrutura e Mecânica