Ankit Aggarwal, T. Martin, S. Shirinov, H. Bihs, A. Kamath
The interest towards offshore wind energy has grown manifolds in the last few decades. Jacket structures are one of the most widely used substructures in the offshore wind turbine installations for intermediate water depths. Offshore structures are exposed to breaking waves. The interaction of breaking waves with the jackets is quite complicated due to the multiple vertical, horizontal and diagonal members. In the present study, a numerical investigation of the wave hydrodynamics and wave forces exerted by regular breaking waves on a jacket is performed. The open-source CFD code REEF3D is used for this purpose, which raises the possibility to model the breaking process physically. The conducted model-scale laboratory experiments have been performed in the past such that a direct comparison is presented.
{"title":"Numerical Study of Breaking Waves and Associated Wave Forces on a Jacket Substructure for Offshore Wind Turbines","authors":"Ankit Aggarwal, T. Martin, S. Shirinov, H. Bihs, A. Kamath","doi":"10.1115/omae2019-95233","DOIUrl":"https://doi.org/10.1115/omae2019-95233","url":null,"abstract":"\u0000 The interest towards offshore wind energy has grown manifolds in the last few decades. Jacket structures are one of the most widely used substructures in the offshore wind turbine installations for intermediate water depths. Offshore structures are exposed to breaking waves. The interaction of breaking waves with the jackets is quite complicated due to the multiple vertical, horizontal and diagonal members. In the present study, a numerical investigation of the wave hydrodynamics and wave forces exerted by regular breaking waves on a jacket is performed. The open-source CFD code REEF3D is used for this purpose, which raises the possibility to model the breaking process physically. The conducted model-scale laboratory experiments have been performed in the past such that a direct comparison is presented.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115412411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tiechao Bai, Yongfeng Wu, Peng Wei, Shuang Wang, Liwei Liu
Design requirements for submarines regarding resistance, maneuverability, stability and stealth tighten with each new generation. Fully understanding the hydrodynamics of the vessels is key if performance requirements need to be met. In this paper, the numerical simulation with three different turbulent models, Reynolds averaged Navier-Stokes (RANS) Realizable k-ε model, RANS SST (Menter’s Shear Stress Transport) k-ω model and the large eddy simulation (LES) are used to simulate the self-propulsion of DARPA SUBOFF submarine under V = 2.755m/s, and the simulation results are compared and analyzed. The comparisons show that the RANS method can be used to simulate the drag and pressure of submarine self-propulsion accurately. The surface pressure of LES is more accurate for fine flow field, the simulation of self-propelled parameters is less as accurate might because the mesh is not refine enough.
{"title":"Numerical Simulation of Submarine Self-Propulsion Based on Different Turbulent Simulation Models","authors":"Tiechao Bai, Yongfeng Wu, Peng Wei, Shuang Wang, Liwei Liu","doi":"10.1115/omae2019-95874","DOIUrl":"https://doi.org/10.1115/omae2019-95874","url":null,"abstract":"\u0000 Design requirements for submarines regarding resistance, maneuverability, stability and stealth tighten with each new generation. Fully understanding the hydrodynamics of the vessels is key if performance requirements need to be met. In this paper, the numerical simulation with three different turbulent models, Reynolds averaged Navier-Stokes (RANS) Realizable k-ε model, RANS SST (Menter’s Shear Stress Transport) k-ω model and the large eddy simulation (LES) are used to simulate the self-propulsion of DARPA SUBOFF submarine under V = 2.755m/s, and the simulation results are compared and analyzed. The comparisons show that the RANS method can be used to simulate the drag and pressure of submarine self-propulsion accurately. The surface pressure of LES is more accurate for fine flow field, the simulation of self-propelled parameters is less as accurate might because the mesh is not refine enough.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125175106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Duan, Hongsen Zhang, Huang Limin, Jianyu Liu, Shao Wenbo, Guanzhou Cao, Zhang Shi
In response to the gradually stringent carbon emission requirements of the International Maritime Organization (IMO), the energy-saving methods of the shipping industry have received increasing attention. Today how to reduce fuel consumptions so as to lower carbon emissions to improve the economic and environmental benefits of ships has become a hot topic. As one of the most easily implemented energy-saving methods, trim optimization has caught more and more researchers’ eyes. In this paper, a commercial CFD software STAR-CCM+ was adopted to analyze the influence of trim on the resistance performance of VLCC ship mainly with fixed model method under various typical conditions of the design draft and the ballast draft respectively. The grid convergence was studied at the design draft and the typical numerical simulations were verified by the experimental results before carrying out various numerical simulations of trim optimization. Seven different kinds of trim conditions, which correspond to the changing process of the full scale ship from trimming by stern 4m to bow 4m, were simulated with 3 different speeds of design draft and ballast draft. The changes of total resistance, frictional resistance and residual resistance were analyzed to explore the effect of trims on the ship’s resistance. The variation of ship’s wetted surface area and waterplane area under different trim angles were studied. It was found that under the condition of low Froude number, both the simulation of free trim and sink method and the fixed model method can achieve good accuracy with the method of fixed model reducing the simulation time obviously. Both conditions of the design draft and ballast draft had a certain reduction effect of total resistance for trimming by bow properly, of which the change of frictional resistance is dominant in the decrease of total resistance at design draft while the change of residual resistance is the main cause at ballast draft. The optimum trims were found and the optimal total resistance reduction effects were evaluated. The optimal total resistance reduction effect increased with speed whether at the design or the ballast draft and the reduction effects were more obvious at ballast draft. Meanwhile, it was found that the changes of wetted surface area and the waterplane area with different trims were close to the variation tendency of the frictional resistance.
{"title":"Numerical Simulation of Trim Optimization on Resistance Performance Based on CFD Method","authors":"W. Duan, Hongsen Zhang, Huang Limin, Jianyu Liu, Shao Wenbo, Guanzhou Cao, Zhang Shi","doi":"10.1115/omae2019-96181","DOIUrl":"https://doi.org/10.1115/omae2019-96181","url":null,"abstract":"\u0000 In response to the gradually stringent carbon emission requirements of the International Maritime Organization (IMO), the energy-saving methods of the shipping industry have received increasing attention. Today how to reduce fuel consumptions so as to lower carbon emissions to improve the economic and environmental benefits of ships has become a hot topic. As one of the most easily implemented energy-saving methods, trim optimization has caught more and more researchers’ eyes.\u0000 In this paper, a commercial CFD software STAR-CCM+ was adopted to analyze the influence of trim on the resistance performance of VLCC ship mainly with fixed model method under various typical conditions of the design draft and the ballast draft respectively. The grid convergence was studied at the design draft and the typical numerical simulations were verified by the experimental results before carrying out various numerical simulations of trim optimization. Seven different kinds of trim conditions, which correspond to the changing process of the full scale ship from trimming by stern 4m to bow 4m, were simulated with 3 different speeds of design draft and ballast draft. The changes of total resistance, frictional resistance and residual resistance were analyzed to explore the effect of trims on the ship’s resistance. The variation of ship’s wetted surface area and waterplane area under different trim angles were studied. It was found that under the condition of low Froude number, both the simulation of free trim and sink method and the fixed model method can achieve good accuracy with the method of fixed model reducing the simulation time obviously. Both conditions of the design draft and ballast draft had a certain reduction effect of total resistance for trimming by bow properly, of which the change of frictional resistance is dominant in the decrease of total resistance at design draft while the change of residual resistance is the main cause at ballast draft. The optimum trims were found and the optimal total resistance reduction effects were evaluated. The optimal total resistance reduction effect increased with speed whether at the design or the ballast draft and the reduction effects were more obvious at ballast draft. Meanwhile, it was found that the changes of wetted surface area and the waterplane area with different trims were close to the variation tendency of the frictional resistance.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116359544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
René Bettencourt Rauffus, A. Maximiano, L. Eça, G. Vaz
Simulations are carried out for a simplified lifeboat drop test case, which consists of a captive axisymmetric generic lifeboat shape (bullet), that penetrates the water surface at a constant velocity and angle of attack. The quantities of interest are the body fixed longitudinal force FX, vertical force FZ, and pitch moment MYY.This case was previously used in a verification and validation exercise [1]. Here, a step forward in complexity is taken, as the previous numerical model is now supplemented with the eddy-viscosity based turbulence model k–ω SST. Both approaches are then used to simulate two different cases: Case 1 with minimal wake effects; and Case 3 with flow separation and significant wake. The results are compared with the experimental data. The numerical uncertainty is estimated for both models. It is seen that for Case 1 the difference between both models is mostly within the comparison uncertainty, except for the longitudinal force FX, where the turbulent flow predicts a larger force, improving the comparison with the experiments. The loads predicted with turbulent flow stayed mostly within 6 % of the laminar flow. For Case 3 small differences between both models are found during/after the wake collapse stage. However, this difference is often within the comparison uncertainty. A reasonable agreement is found with the experimental data, except for FZ after the bow wake collapse. The turbulent flow improves slightly on the laminar approach regarding the agreement with the experiments, however it can be argued if this difference justifies the increased computational cost of the turbulence model.
{"title":"CFD Analysis of a Captive Bullet Entry in Calm Water With and Without Turbulence","authors":"René Bettencourt Rauffus, A. Maximiano, L. Eça, G. Vaz","doi":"10.1115/omae2019-96099","DOIUrl":"https://doi.org/10.1115/omae2019-96099","url":null,"abstract":"\u0000 Simulations are carried out for a simplified lifeboat drop test case, which consists of a captive axisymmetric generic lifeboat shape (bullet), that penetrates the water surface at a constant velocity and angle of attack. The quantities of interest are the body fixed longitudinal force FX, vertical force FZ, and pitch moment MYY.This case was previously used in a verification and validation exercise [1]. Here, a step forward in complexity is taken, as the previous numerical model is now supplemented with the eddy-viscosity based turbulence model k–ω SST. Both approaches are then used to simulate two different cases: Case 1 with minimal wake effects; and Case 3 with flow separation and significant wake. The results are compared with the experimental data. The numerical uncertainty is estimated for both models. It is seen that for Case 1 the difference between both models is mostly within the comparison uncertainty, except for the longitudinal force FX, where the turbulent flow predicts a larger force, improving the comparison with the experiments. The loads predicted with turbulent flow stayed mostly within 6 % of the laminar flow. For Case 3 small differences between both models are found during/after the wake collapse stage. However, this difference is often within the comparison uncertainty. A reasonable agreement is found with the experimental data, except for FZ after the bow wake collapse. The turbulent flow improves slightly on the laminar approach regarding the agreement with the experiments, however it can be argued if this difference justifies the increased computational cost of the turbulence model.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131676251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Increased waterborne trade has led to the construction of ever larger ships and barges as oversized modules are transported by sea. The provision of tugs for towing such vessels has become a serious issue, especially in restricted areas often characterized by coastal regions of limited water depth. Wind loads are most relevant for towing operations because large forces act on the sail area and submerged hull of the towed vessels, such as construction barges when carrying oversized modules or fully laden containerships. Systematic steady and unsteady numerical simulations were performed using a RANS-based field method to predict wind and current forces and moments acting on representative construction barges, containerships, tankers, and passenger ships. Aero- and hydrodynamic computations were carried out separately. Aerodynamic computations considered various deck load configurations to represent realistic loading conditions; hydrodynamic computations accounted for finite water depth. Agreement with available wind tunnel experimental data was generally favorable. Our purpose was to provide a reference for wind and current loads on different barge and ship types. The objective was not to investigate flow details needed for, e.g., smoke propagation, helicopter landing, etc. This has been covered by other researchers.
{"title":"Wind and Current Loads on Barges and Ships","authors":"O. E. Moctar, T. Schellin, J. Neugebauer","doi":"10.1115/omae2019-95716","DOIUrl":"https://doi.org/10.1115/omae2019-95716","url":null,"abstract":"\u0000 Increased waterborne trade has led to the construction of ever larger ships and barges as oversized modules are transported by sea. The provision of tugs for towing such vessels has become a serious issue, especially in restricted areas often characterized by coastal regions of limited water depth. Wind loads are most relevant for towing operations because large forces act on the sail area and submerged hull of the towed vessels, such as construction barges when carrying oversized modules or fully laden containerships. Systematic steady and unsteady numerical simulations were performed using a RANS-based field method to predict wind and current forces and moments acting on representative construction barges, containerships, tankers, and passenger ships. Aero- and hydrodynamic computations were carried out separately. Aerodynamic computations considered various deck load configurations to represent realistic loading conditions; hydrodynamic computations accounted for finite water depth. Agreement with available wind tunnel experimental data was generally favorable.\u0000 Our purpose was to provide a reference for wind and current loads on different barge and ship types. The objective was not to investigate flow details needed for, e.g., smoke propagation, helicopter landing, etc. This has been covered by other researchers.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124945985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes a numerical procedure for the prediction of the wind load on various types of commercial ships, such as LNGC, oil tanker and container ship. As the size of vessels increases, wind load is playing a more important role when sailing in an open sea and mooring at harbors. To estimate wind load, 3D steady RANS CFD simulation is performed and validated with experimental results obtained from wind tunnel tests. The effect of turbulence source is studied to maintain the turbulence intensity profile at the test section of the wind tunnel and the boundary layer mesh is also investigated to improve the accuracy. The discrepancy in force and moment coefficients between CFD results and wind tunnel tests is reduced and the comparison results show good agreements.
{"title":"Development and Validation of CFD Analysis Procedure for Predicting Wind Load on Commercial Ships","authors":"Sang-Hun Lee, Seihwan Kim, D. Kim, Young-Bum Lee","doi":"10.1115/omae2019-95410","DOIUrl":"https://doi.org/10.1115/omae2019-95410","url":null,"abstract":"\u0000 This paper describes a numerical procedure for the prediction of the wind load on various types of commercial ships, such as LNGC, oil tanker and container ship. As the size of vessels increases, wind load is playing a more important role when sailing in an open sea and mooring at harbors. To estimate wind load, 3D steady RANS CFD simulation is performed and validated with experimental results obtained from wind tunnel tests. The effect of turbulence source is studied to maintain the turbulence intensity profile at the test section of the wind tunnel and the boundary layer mesh is also investigated to improve the accuracy. The discrepancy in force and moment coefficients between CFD results and wind tunnel tests is reduced and the comparison results show good agreements.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114662913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xueshen Xie, Yuxiang Wan, Qing Wang, Hao Liu, D. Feng
A numerical simulation of the hydrodynamic interaction and attitude of a ship and two ships of different sizes navigating in parallel in waves were carried out in this paper. The study of the two ships navigating in parallel is of great significance in marine replenishment. This paper used in house computational fluid dynamics (CFD) code to solve unsteady RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations. URANS equations are solved by finite difference method and PISO algorithm. Structured grid with overset technology have been used to make computations. Turbulence models used the Shear Stress Transport (SST) k-ω model. The method used for free surface simulation is single phase level set. In this paper, two DTMB 5415 with different scales are selected for simulation analysis. This paper analyzed the impact of the big ship on the small ship when the two ships were navigating in parallel. This paper also analyzed the relationship between interaction and velocity between hulls, which has certain guiding significance for the ship’s encounter on the sea.
{"title":"Numerical Simulation of Ship-Ship Interactions in Waves","authors":"Xueshen Xie, Yuxiang Wan, Qing Wang, Hao Liu, D. Feng","doi":"10.1115/omae2019-95737","DOIUrl":"https://doi.org/10.1115/omae2019-95737","url":null,"abstract":"\u0000 A numerical simulation of the hydrodynamic interaction and attitude of a ship and two ships of different sizes navigating in parallel in waves were carried out in this paper. The study of the two ships navigating in parallel is of great significance in marine replenishment. This paper used in house computational fluid dynamics (CFD) code to solve unsteady RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations. URANS equations are solved by finite difference method and PISO algorithm. Structured grid with overset technology have been used to make computations. Turbulence models used the Shear Stress Transport (SST) k-ω model. The method used for free surface simulation is single phase level set. In this paper, two DTMB 5415 with different scales are selected for simulation analysis. This paper analyzed the impact of the big ship on the small ship when the two ships were navigating in parallel. This paper also analyzed the relationship between interaction and velocity between hulls, which has certain guiding significance for the ship’s encounter on the sea.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126509703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Slender offshore structures of a cylindrical cross section, such as drilling and production risers, are susceptible to vortex-induced vibrations (VIV) when exposed to water currents. The present work presents an experimental investigation of the suppression of VIV of a circular cylinder by means of three different types of helical strakes: (i) a strake with continuous blades, (ii) a strake with serrated blades (or fins) and (iii) a strake with serrated blades individually twisted in relation to the incoming flow. By altering the blade geometry to produce the twisted-bladed strake, it was possible to keep the same level of suppression of the cross-flow vibration achieved by conventional strakes, but reducing drag in 15%. Experiments have been conducted in a recirculating water channel at moderate Reynolds numbers.
{"title":"Laboratory Investigation of Helical Strakes With Serrated and Twisted Fins to Suppress VIV","authors":"G. Assi, Tommaso Crespi","doi":"10.1115/omae2019-95129","DOIUrl":"https://doi.org/10.1115/omae2019-95129","url":null,"abstract":"\u0000 Slender offshore structures of a cylindrical cross section, such as drilling and production risers, are susceptible to vortex-induced vibrations (VIV) when exposed to water currents. The present work presents an experimental investigation of the suppression of VIV of a circular cylinder by means of three different types of helical strakes: (i) a strake with continuous blades, (ii) a strake with serrated blades (or fins) and (iii) a strake with serrated blades individually twisted in relation to the incoming flow. By altering the blade geometry to produce the twisted-bladed strake, it was possible to keep the same level of suppression of the cross-flow vibration achieved by conventional strakes, but reducing drag in 15%. Experiments have been conducted in a recirculating water channel at moderate Reynolds numbers.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124623401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuwang Xu, Jungao Wang, H. Ren, Mengmeng Zhang, Shixiao Fu
To investigate the VIV characteristics and to further develop the corresponding numerical predictions of a steel catenary riser under out-of-plane current, a large-scale model of a steel catenary riser was towing in an ocean basin at various speeds and directions. Fiber Bragg grating strain sensors are instrumented on the riser model to measure both in-plane and out-of-plane responses. The vortex-induced vibration responses of the steel catenary riser under out-of-plane current, i.e., the oscillating amplitude, the response frequency, and the traveling wave phenomenon, are compared with those under the in-plane current.
{"title":"Vortex Induced Vibration of a Steel Catenary Riser Under Out-of-Plane Current: An Experimental Study","authors":"Yuwang Xu, Jungao Wang, H. Ren, Mengmeng Zhang, Shixiao Fu","doi":"10.1115/omae2019-96112","DOIUrl":"https://doi.org/10.1115/omae2019-96112","url":null,"abstract":"\u0000 To investigate the VIV characteristics and to further develop the corresponding numerical predictions of a steel catenary riser under out-of-plane current, a large-scale model of a steel catenary riser was towing in an ocean basin at various speeds and directions. Fiber Bragg grating strain sensors are instrumented on the riser model to measure both in-plane and out-of-plane responses. The vortex-induced vibration responses of the steel catenary riser under out-of-plane current, i.e., the oscillating amplitude, the response frequency, and the traveling wave phenomenon, are compared with those under the in-plane current.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132940355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. B. Reddy, A. Magee, R. Jaiman, Jing Liu, Wei Xu, A. Choudhary, A. Hussain
In this paper, we present a data-driven approach to construct a reduced-order model (ROM) for the unsteady flow field and fluid-structure interaction. This proposed approach relies on (i) a projection of the high-dimensional data from the Navier-Stokes equations to a low-dimensional subspace using the proper orthogonal decomposition (POD) and (ii) integration of the low-dimensional model with the recurrent neural networks. For the hybrid ROM formulation, we consider long short term memory networks with encoder-decoder architecture, which is a special variant of recurrent neural networks. The mathematical structure of recurrent neural networks embodies a non-linear state space form of the underlying dynamical behavior. This particular attribute of an RNN makes it suitable for non-linear unsteady flow problems. In the proposed hybrid RNN method, the spatial and temporal features of the unsteady flow system are captured separately. Time-invariant modes obtained by low-order projection embodies the spatial features of the flow field, while the temporal behavior of the corresponding modal coefficients is learned via recurrent neural networks. The effectiveness of the proposed method is first demonstrated on a canonical problem of flow past a cylinder at low Reynolds number. With regard to a practical marine/offshore engineering demonstration, we have applied and examined the reliability of the proposed data-driven framework for the predictions of vortex-induced vibrations of a flexible offshore riser at high Reynolds number.
{"title":"Reduced Order Model for Unsteady Fluid Flows via Recurrent Neural Networks","authors":"S. B. Reddy, A. Magee, R. Jaiman, Jing Liu, Wei Xu, A. Choudhary, A. Hussain","doi":"10.1115/omae2019-96543","DOIUrl":"https://doi.org/10.1115/omae2019-96543","url":null,"abstract":"\u0000 In this paper, we present a data-driven approach to construct a reduced-order model (ROM) for the unsteady flow field and fluid-structure interaction. This proposed approach relies on (i) a projection of the high-dimensional data from the Navier-Stokes equations to a low-dimensional subspace using the proper orthogonal decomposition (POD) and (ii) integration of the low-dimensional model with the recurrent neural networks. For the hybrid ROM formulation, we consider long short term memory networks with encoder-decoder architecture, which is a special variant of recurrent neural networks. The mathematical structure of recurrent neural networks embodies a non-linear state space form of the underlying dynamical behavior. This particular attribute of an RNN makes it suitable for non-linear unsteady flow problems. In the proposed hybrid RNN method, the spatial and temporal features of the unsteady flow system are captured separately. Time-invariant modes obtained by low-order projection embodies the spatial features of the flow field, while the temporal behavior of the corresponding modal coefficients is learned via recurrent neural networks. The effectiveness of the proposed method is first demonstrated on a canonical problem of flow past a cylinder at low Reynolds number. With regard to a practical marine/offshore engineering demonstration, we have applied and examined the reliability of the proposed data-driven framework for the predictions of vortex-induced vibrations of a flexible offshore riser at high Reynolds number.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127852203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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