In situations where the calculation of ocean wave propagation and impact on offshore structures is required, fast numerical solvers are desired in order to find relevant wave events in a first step. After the identification of the relevant events, Computational Fluid Dynamics (CFD) based Numerical Wave Tanks (NWT) with an interface capturing two-phase flow approach can be used to resolve the complex wave structure interaction, including breaking wave kinematics. CFD models emphasize detail of the hydrodynamic physics, which makes them not the ideal candidate for the event identification due to the large computational resources involved. In the current paper a new numerical wave model is represented that solves the Laplace equation for the flow potential and the nonlinear kinematic and dynamics free surface boundary conditions. This approach requires reduced computational resources compared to CFD based NWTs. In contrast to existing approaches, the resulting fully nonlinear potential flow solver REEF3D::FNPF uses a σ-coordinate grid for the computations. Solid boundaries are incorporated through a ghost cell immersed boundary method. The free surface boundary conditions are discretized using fifth-order WENO finite difference methods and the third-order TVD Runge-Kutta scheme for time stepping. The Laplace equation for the potential is solved with Hypres stabilized bi-conjugated gradient solver preconditioned with geometric multi-grid. REEF3D::FNPF is fully parallelized following the domain decomposition strategy and the MPI communication protocol. The model is successfully tested for wave propagation benchmark cases for shallow water conditions with variable bottom as well as deep water.
{"title":"REEF3D::FNPF: A Flexible Fully Nonlinear Potential Flow Solver","authors":"H. Bihs, Weizhi Wang, T. Martin, A. Kamath","doi":"10.1115/omae2019-96524","DOIUrl":"https://doi.org/10.1115/omae2019-96524","url":null,"abstract":"\u0000 In situations where the calculation of ocean wave propagation and impact on offshore structures is required, fast numerical solvers are desired in order to find relevant wave events in a first step. After the identification of the relevant events, Computational Fluid Dynamics (CFD) based Numerical Wave Tanks (NWT) with an interface capturing two-phase flow approach can be used to resolve the complex wave structure interaction, including breaking wave kinematics. CFD models emphasize detail of the hydrodynamic physics, which makes them not the ideal candidate for the event identification due to the large computational resources involved. In the current paper a new numerical wave model is represented that solves the Laplace equation for the flow potential and the nonlinear kinematic and dynamics free surface boundary conditions. This approach requires reduced computational resources compared to CFD based NWTs. In contrast to existing approaches, the resulting fully nonlinear potential flow solver REEF3D::FNPF uses a σ-coordinate grid for the computations. Solid boundaries are incorporated through a ghost cell immersed boundary method. The free surface boundary conditions are discretized using fifth-order WENO finite difference methods and the third-order TVD Runge-Kutta scheme for time stepping. The Laplace equation for the potential is solved with Hypres stabilized bi-conjugated gradient solver preconditioned with geometric multi-grid. REEF3D::FNPF is fully parallelized following the domain decomposition strategy and the MPI communication protocol. The model is successfully tested for wave propagation benchmark cases for shallow water conditions with variable bottom as well as deep water.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"32 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":"131455458","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}
Yunxing Zhang, W. Duan, K. Liao, Shan Ma, Guihua Xia
The numerical simulation of wave breaking problem is still a tough challenge, partly due to the large grid number and CPU time requirement for capturing the multi-scale structures embedded in it. In this paper, a two-dimensional two-phase flow model with Adaptive Mesh Refinement (AMR) is proposed for simulating solitary wave breaking problems. Fractional step method is employed for the velocity-pressure decoupling. The free surface flow is captured with the Volume-of-Fluid (VOF) method combined with Piecewise Linear Interface Calculation (PLIC) for the reconstruction of the interface. Immersed boundary (IB) method is utilized to account for the existence of solid bodies. A geometric multigrid method is adopted for the solution of Pressure Poisson Equation (PPE). Benchmark case of advection test is considered first to test the VOF method. Then the solitary wave propagation problem is utilized to validate the model on AMR grid as well as analyze the efficiency of AMR. Furthermore, the solitary wave past a submerged stationary stage problem is simulated to validate the combined IB-VOF-AMR model. All the numerical results are compared with analytic solutions, experimental data or other published numerical results, and good agreements are obtained. Finally, the influence of stage height on the occurrence of wave breaking is analyzed. The locations of wave breaking are summarized for different stage heights.
{"title":"Numerical Simulation of Solitary Wave Breaking With Adaptive Mesh Refinement","authors":"Yunxing Zhang, W. Duan, K. Liao, Shan Ma, Guihua Xia","doi":"10.1115/omae2019-95224","DOIUrl":"https://doi.org/10.1115/omae2019-95224","url":null,"abstract":"\u0000 The numerical simulation of wave breaking problem is still a tough challenge, partly due to the large grid number and CPU time requirement for capturing the multi-scale structures embedded in it. In this paper, a two-dimensional two-phase flow model with Adaptive Mesh Refinement (AMR) is proposed for simulating solitary wave breaking problems. Fractional step method is employed for the velocity-pressure decoupling. The free surface flow is captured with the Volume-of-Fluid (VOF) method combined with Piecewise Linear Interface Calculation (PLIC) for the reconstruction of the interface. Immersed boundary (IB) method is utilized to account for the existence of solid bodies. A geometric multigrid method is adopted for the solution of Pressure Poisson Equation (PPE).\u0000 Benchmark case of advection test is considered first to test the VOF method. Then the solitary wave propagation problem is utilized to validate the model on AMR grid as well as analyze the efficiency of AMR. Furthermore, the solitary wave past a submerged stationary stage problem is simulated to validate the combined IB-VOF-AMR model. All the numerical results are compared with analytic solutions, experimental data or other published numerical results, and good agreements are obtained. Finally, the influence of stage height on the occurrence of wave breaking is analyzed. The locations of wave breaking are summarized for different stage heights.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"39 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":"129956760","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}
Ye Lu, P. Temarel, Qiu Jin, You-sheng Wu, Xin-yun Ni, C. Tian
Nowadays, more and more 20,000 twenty-foot equivalent unit (TEU) class ultra large container ships (ULCS) have been built in service across the worldwide. It is paramount that hydroelastic specialists become paying close attention to structural responses and loads predictions due to up to a 400m length of the ships. First of all, mesh convergence by finite element analysis is necessary to determine in the numerical calculation. In this paper, based on the three-dimension linear frequency domain hydroelasticity theory, the hydrodynamic meshes convergence is discussed when modelling the hull surface of the ULCS. Ascribe to the Sunway TaihuLight, rank 3 in the current TOP500 supercomputer list, the Message Passing Interface and the multi-level parallel programming model are used aimed to the wetted panels, the wave frequencies and so on. Several sets of different global grid density and grid distribution along the ship’s length for the containership are calculated to compare the hydrodynamic coefficients such as added mass, damping, wave exciting force, ship motions and exterior loads with several typical service speeds in the head regular wave. It has been concluded that sensitivity of numerical modelling converges to a stable state with increasing the panel numbers per ship. Therefore, one set of grid division optimised, and superposed elastic modes numbers are recommended in the hydroelastic analysis of numerical hydroelastic prediction of springing and whipping.
{"title":"Numerical Convergence on the Hydroelasticity of a Large Containership","authors":"Ye Lu, P. Temarel, Qiu Jin, You-sheng Wu, Xin-yun Ni, C. Tian","doi":"10.1115/omae2019-95200","DOIUrl":"https://doi.org/10.1115/omae2019-95200","url":null,"abstract":"\u0000 Nowadays, more and more 20,000 twenty-foot equivalent unit (TEU) class ultra large container ships (ULCS) have been built in service across the worldwide. It is paramount that hydroelastic specialists become paying close attention to structural responses and loads predictions due to up to a 400m length of the ships. First of all, mesh convergence by finite element analysis is necessary to determine in the numerical calculation. In this paper, based on the three-dimension linear frequency domain hydroelasticity theory, the hydrodynamic meshes convergence is discussed when modelling the hull surface of the ULCS. Ascribe to the Sunway TaihuLight, rank 3 in the current TOP500 supercomputer list, the Message Passing Interface and the multi-level parallel programming model are used aimed to the wetted panels, the wave frequencies and so on. Several sets of different global grid density and grid distribution along the ship’s length for the containership are calculated to compare the hydrodynamic coefficients such as added mass, damping, wave exciting force, ship motions and exterior loads with several typical service speeds in the head regular wave. It has been concluded that sensitivity of numerical modelling converges to a stable state with increasing the panel numbers per ship. Therefore, one set of grid division optimised, and superposed elastic modes numbers are recommended in the hydroelastic analysis of numerical hydroelastic prediction of springing and whipping.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"1 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":"130501250","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}
Qing Wang, Xuanshu Chen, Liwei Liu, Xianzhou Wang, Ming-jun Liu
The dangerous situation caused by the breakage of the ship will pose a serious threat to crew and ship safety. If the ship’s liquid cargo or fuel leaks, it will cause serious damage to the marine environment. If damage occurs accompanied by roll and other motions, it may cause more dangerous consequences. It is an important issue to study the damaged ship in time-domain. In this paper, the motions of the damaged DTMB 5512 in calm water and regular beam waves are studied numerically. The ship motions are analyzed through CFD methods, which are acknowledged as a reliable approach to simulate and analyze these complex physical phenomena. An in-house CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for solving RANS equations coupled with six degrees of freedom (6DOF) solid body motion equations. RANS equations discretized by finite difference method and solved by PISO algorithm. Level set was used for free surface simulation. The dynamic behavior of model was observed in both intact and damaged condition. The heave, roll and pitch amplitudes of the damaged ship were studied in calm water and beam wave of three wavelengths.
{"title":"Numerical Simulation of Damaged Ship’s Motion in Beam Waves","authors":"Qing Wang, Xuanshu Chen, Liwei Liu, Xianzhou Wang, Ming-jun Liu","doi":"10.1115/omae2019-96791","DOIUrl":"https://doi.org/10.1115/omae2019-96791","url":null,"abstract":"\u0000 The dangerous situation caused by the breakage of the ship will pose a serious threat to crew and ship safety. If the ship’s liquid cargo or fuel leaks, it will cause serious damage to the marine environment. If damage occurs accompanied by roll and other motions, it may cause more dangerous consequences. It is an important issue to study the damaged ship in time-domain. In this paper, the motions of the damaged DTMB 5512 in calm water and regular beam waves are studied numerically. The ship motions are analyzed through CFD methods, which are acknowledged as a reliable approach to simulate and analyze these complex physical phenomena. An in-house CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for solving RANS equations coupled with six degrees of freedom (6DOF) solid body motion equations. RANS equations discretized by finite difference method and solved by PISO algorithm. Level set was used for free surface simulation. The dynamic behavior of model was observed in both intact and damaged condition. The heave, roll and pitch amplitudes of the damaged ship were studied in calm water and beam wave of three wavelengths.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"100 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":"128103839","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}
In ship model tests, a model-ship correlation line (e.g., the ITTC57 formula) is used to calculate the frictional resistance of both the ship and its scaled model. However, this line is designed for deep water and the effects of water depth is not considered. Research has been conducted to improve the correlation line in shallow water, but studies of the extremely shallow water case (depth/draft, h/T < 1.2) are rare. This study focuses on the friction of two ship types in extremely shallow water, where the ship’s boundary layer cannot develop freely. The physical details are analyzed based on the data generated with Computational Fluid Dynamics (CFD) calculations. The results show that for certain ship types at the same Reynolds number, the frictional resistance becomes smaller when the water is shallower. The geometry of the ship, in addition to the Reynolds number, becomes essential to the prediction of ship’s friction in extremely shallow water. Therefore, this scenario is different from intermediate shallow and deep water, and the prediction method should be considered separately. The data and analysis shown in this study can help to improve the understanding and prediction of ship’s frictional resistance in extremely shallow water.
{"title":"A Study of Ship’s Frictional Resistance in Extremely Shallow Water","authors":"Q. Zeng, R. Hekkenberg, C. Thill","doi":"10.1115/omae2019-95076","DOIUrl":"https://doi.org/10.1115/omae2019-95076","url":null,"abstract":"\u0000 In ship model tests, a model-ship correlation line (e.g., the ITTC57 formula) is used to calculate the frictional resistance of both the ship and its scaled model. However, this line is designed for deep water and the effects of water depth is not considered. Research has been conducted to improve the correlation line in shallow water, but studies of the extremely shallow water case (depth/draft, h/T < 1.2) are rare. This study focuses on the friction of two ship types in extremely shallow water, where the ship’s boundary layer cannot develop freely. The physical details are analyzed based on the data generated with Computational Fluid Dynamics (CFD) calculations. The results show that for certain ship types at the same Reynolds number, the frictional resistance becomes smaller when the water is shallower. The geometry of the ship, in addition to the Reynolds number, becomes essential to the prediction of ship’s friction in extremely shallow water. Therefore, this scenario is different from intermediate shallow and deep water, and the prediction method should be considered separately. The data and analysis shown in this study can help to improve the understanding and prediction of ship’s frictional resistance in extremely shallow water.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"372 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":"121745365","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}
The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, CFD simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were employed in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Further investigations into the roughness effect on the pressure and velocity field, surface pressure and wall shear stress, and propeller vortices were examined.
{"title":"An Investigation Into the Effect of Biofouling on Full-Scale Propeller Performance Using CFD","authors":"Soonseok Song, Y. Demirel, M. Atlar","doi":"10.1115/OMAE2019-95315","DOIUrl":"https://doi.org/10.1115/OMAE2019-95315","url":null,"abstract":"\u0000 The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, CFD simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were employed in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Further investigations into the roughness effect on the pressure and velocity field, surface pressure and wall shear stress, and propeller vortices were examined.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124581295","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}
Vortex around ships is easy to cause noise, vibration and fatigue of propellers. In addition, the complexity and variability of vortex will also have a greater impact on sensors and detection equipment installed on the surface of the vehicle. It is necessary to carry out corresponding research. In this paper, the fluctuating pressure was numerically analyzed using improved DDES model. And applying overset grids to better capture vortices around submarine sail. The numerical study of a three-dimensional unsteady vortex structure was performed for calculation. There were two vortex tubes and some broken small vortices behind the sail. The simulation results showed that trailing vortices behind sail slightly swept up and the distance between two vortex tubes became larger.
{"title":"The Vortex and Wall Fluctuating Pressure Around Submarine Sail Based on DDES Method","authors":"R. Luo, Yue Sun, Hang Zhang, Jin Zhan, X. Cai","doi":"10.1115/omae2019-96018","DOIUrl":"https://doi.org/10.1115/omae2019-96018","url":null,"abstract":"\u0000 Vortex around ships is easy to cause noise, vibration and fatigue of propellers. In addition, the complexity and variability of vortex will also have a greater impact on sensors and detection equipment installed on the surface of the vehicle. It is necessary to carry out corresponding research. In this paper, the fluctuating pressure was numerically analyzed using improved DDES model. And applying overset grids to better capture vortices around submarine sail. The numerical study of a three-dimensional unsteady vortex structure was performed for calculation. There were two vortex tubes and some broken small vortices behind the sail. The simulation results showed that trailing vortices behind sail slightly swept up and the distance between two vortex tubes became larger.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127897431","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}
Induced vibrations are multi-dimensional oscillations in a marine riser, suspended wire or other slender structures, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. In previous OMAE papers, we have shown how sustained actions evolve physical changes in slender structures. Using nonlinear physics-based simulations, we showed how these structural changes fundamentally determine the nature of the vibrations that any sustained action (including flowing fluid around the structure) can induce. In this paper, we step back to focus on a classical laboratory experiment, whereby the structure has been constrained to function as a simple mass-on-spring oscillator. In this unchanging structure, we show how the geometric physics of the fluid drag load induce Vortex-Induced Vibrations (VIV). We show how these vibrations naturally grow in time to maximum amplitude.
{"title":"The Evolutionary Geometric Physics of Vortex-Induced Vibrations","authors":"R. Zueck","doi":"10.1115/omae2019-95548","DOIUrl":"https://doi.org/10.1115/omae2019-95548","url":null,"abstract":"\u0000 Induced vibrations are multi-dimensional oscillations in a marine riser, suspended wire or other slender structures, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. In previous OMAE papers, we have shown how sustained actions evolve physical changes in slender structures. Using nonlinear physics-based simulations, we showed how these structural changes fundamentally determine the nature of the vibrations that any sustained action (including flowing fluid around the structure) can induce. In this paper, we step back to focus on a classical laboratory experiment, whereby the structure has been constrained to function as a simple mass-on-spring oscillator. In this unchanging structure, we show how the geometric physics of the fluid drag load induce Vortex-Induced Vibrations (VIV). We show how these vibrations naturally grow in time to maximum amplitude.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121077552","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}
Zhiheng Li, Jiawei Yu, D. Feng, Jiang Kaijun, Yujie Zhou
The virtual propeller model can achieve the rapid numerical prediction of the ship self-propulsion performance through viscous flow, which used the improved body-force method. The two-dimensional lift coefficient CL and the drag coefficient CD are very important parameters in this method, which are generally obtained by the potential flow methods and cannot incorporate viscous effects. This study will perform a fully nonlinear unsteady RANS (Reynolds Average Navier-Stokes) simulation to get the KP505 open-water characteristics and then divide its blade into several parts to get the lift coefficient CL and the drag coefficient CD on each one. Then fitting by multivariate regression method, the relationship between CL, CD and propeller parameters is obtained. The Unsteady Blade Element Theory (UBET) is coupled with RANS in house CFD code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) to calculate the flow around the propeller. RANS equations are solved by the finite difference method and PISO arithmetic. have been made using structured grid with overset technology. The results show that comparing with the EFD data, the maximum differences of the result of the improved body-force method are 4.32% and 2.7% for the thrust coefficient and the torque coefficient respectively near the propeller operating point.
虚拟螺旋桨模型采用改进的体力法，实现了船舶在粘性流动中自推进性能的快速数值预测。二维升力系数CL和阻力系数CD是该方法中非常重要的参数，这些参数一般是通过势流法获得的，不能考虑粘性效应。本研究将对KP505进行完全非线性非定常RANS (Reynolds Average Navier-Stokes)模拟，得到其开放水域特性，并将其叶片分成若干部分，得到每个部分的升力系数CL和阻力系数CD。然后用多元回归方法进行拟合，得到了螺旋桨参数与船型的关系。将非定常叶片单元理论(UBET)与RANS内部CFD代码HUST-Ship(船舶水动力非定常模拟技术)相结合，计算螺旋桨周围的流动。采用有限差分法和PISO算法求解RANS方程。采用结构网格叠加技术制作。结果表明:与EFD数据相比，改进的体力法在螺旋桨工作点附近的推力系数和扭矩系数的最大差异分别为4.32%和2.7%;
{"title":"Research on the Improved Body-Force Method Based on Viscous Flow","authors":"Zhiheng Li, Jiawei Yu, D. Feng, Jiang Kaijun, Yujie Zhou","doi":"10.1115/omae2019-95887","DOIUrl":"https://doi.org/10.1115/omae2019-95887","url":null,"abstract":"\u0000 The virtual propeller model can achieve the rapid numerical prediction of the ship self-propulsion performance through viscous flow, which used the improved body-force method. The two-dimensional lift coefficient CL and the drag coefficient CD are very important parameters in this method, which are generally obtained by the potential flow methods and cannot incorporate viscous effects. This study will perform a fully nonlinear unsteady RANS (Reynolds Average Navier-Stokes) simulation to get the KP505 open-water characteristics and then divide its blade into several parts to get the lift coefficient CL and the drag coefficient CD on each one. Then fitting by multivariate regression method, the relationship between CL, CD and propeller parameters is obtained. The Unsteady Blade Element Theory (UBET) is coupled with RANS in house CFD code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) to calculate the flow around the propeller. RANS equations are solved by the finite difference method and PISO arithmetic. have been made using structured grid with overset technology. The results show that comparing with the EFD data, the maximum differences of the result of the improved body-force method are 4.32% and 2.7% for the thrust coefficient and the torque coefficient respectively near the propeller operating point.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114294764","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}
In deep sea oil exploitation, offshore platforms will move periodically in the water under the combined effects of waves, currents and winds. The relatively oscillatory flow is generated between the riser connected to the platform and the water. Vortex-induced Vibration (VIV) features of a single cylinder in the oscillatory flow are more complicated than that in the uniform flow. In this paper, numerical investigations on VIV of a flexible cylinder with different aspect ratios exposed to the oscillatory flow are carried out by the in-house CFD solver viv-FOAM-SJTU, which is developed based on the open source toolbox OpenFOAM. The flexible cylinder is forced to oscillate harmonically in the in-line direction in the still water and is allowed to freely vibrate in the cross-flow direction. Firstly, comparisons on referred experiments and simulations are conducted to verify the validity of the solver. Then, the modal decomposition analysis method and the Fast Fourier Transform (FFT) method are used to obtain the dominant vibration modes and frequencies of the cylinder in the following simulations.
{"title":"Vortex-Induced Vibration of a Flexible Cylinder Experiencing Oscillatory Flow With Different Aspect Ratios","authors":"D. Deng, Lei Wu, D. Wan","doi":"10.1115/omae2019-95522","DOIUrl":"https://doi.org/10.1115/omae2019-95522","url":null,"abstract":"\u0000 In deep sea oil exploitation, offshore platforms will move periodically in the water under the combined effects of waves, currents and winds. The relatively oscillatory flow is generated between the riser connected to the platform and the water. Vortex-induced Vibration (VIV) features of a single cylinder in the oscillatory flow are more complicated than that in the uniform flow. In this paper, numerical investigations on VIV of a flexible cylinder with different aspect ratios exposed to the oscillatory flow are carried out by the in-house CFD solver viv-FOAM-SJTU, which is developed based on the open source toolbox OpenFOAM. The flexible cylinder is forced to oscillate harmonically in the in-line direction in the still water and is allowed to freely vibrate in the cross-flow direction. Firstly, comparisons on referred experiments and simulations are conducted to verify the validity of the solver. Then, the modal decomposition analysis method and the Fast Fourier Transform (FFT) method are used to obtain the dominant vibration modes and frequencies of the cylinder in the following simulations.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131787642","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：