Hendrik Wrenger, B. Sainte-Rose, C. Goniva, R. Hilbert
Results of a flume experiment and numerical model of plastic accumulation in front of a plate are presented. The single phase CFD-DEM model formed a successful benchmark case to model plastic accumulation inside an ocean cleanup system. A fixed wooden plate was placed in a steady cross flow and plastic was released upstream of it. We recorded the evolution of the plastic accumulation profiles under slowly increasing plastic load. Experimental parameters were the flow velocity, draft of the plate (varying the plate Froude number) as well as three different types of plastic particles. The accumulation of oil in front of barriers and parallels to the phenomena of plastic accumulation were reviewed. As a second part of the project we used the open source CFD-DEM code CFDEM® to reproduce the flume experiment. It couples the discrete element method (DEM) software LIGGGHTS® and the open source computational fluid dynamics (CFD) software OpenFOAM®. A linear relationship of the relative depth of the accumulation with the Froude number of the plate was found for a given type of particle and reproduced in the numerical model. We identified limitations of the experimental setup, calibration experiments and the single phase CFD-DEM approach and outlined the steps for further research.
{"title":"Plastic Accumulation in Front of a Plate in Cross Flow: Model Scale Test and CFD-DEM Modelling","authors":"Hendrik Wrenger, B. Sainte-Rose, C. Goniva, R. Hilbert","doi":"10.1115/omae2019-96095","DOIUrl":"https://doi.org/10.1115/omae2019-96095","url":null,"abstract":"\u0000 Results of a flume experiment and numerical model of plastic accumulation in front of a plate are presented. The single phase CFD-DEM model formed a successful benchmark case to model plastic accumulation inside an ocean cleanup system.\u0000 A fixed wooden plate was placed in a steady cross flow and plastic was released upstream of it. We recorded the evolution of the plastic accumulation profiles under slowly increasing plastic load. Experimental parameters were the flow velocity, draft of the plate (varying the plate Froude number) as well as three different types of plastic particles. The accumulation of oil in front of barriers and parallels to the phenomena of plastic accumulation were reviewed.\u0000 As a second part of the project we used the open source CFD-DEM code CFDEM® to reproduce the flume experiment. It couples the discrete element method (DEM) software LIGGGHTS® and the open source computational fluid dynamics (CFD) software OpenFOAM®.\u0000 A linear relationship of the relative depth of the accumulation with the Froude number of the plate was found for a given type of particle and reproduced in the numerical model. We identified limitations of the experimental setup, calibration experiments and the single phase CFD-DEM approach and outlined the steps for further research.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"20 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":"133858438","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-Induced Vibration (VIV) is one of the main sources of fatigue damage for long slender risers. Typical VIV assessment of risers is conducted using semi-empirical software tools in which the sectional hydrodynamic coefficients are derived from forced oscillation model tests on short rigid risers. The Steel Lazy Wave Riser (SLWR) with buoyancy sections is an attractive concept for improving fatigue performance in deep water developments, but there is limited model test data available for the hydrodynamic coefficients on SLWR’s. In Part I of the present study (Jang & Kim, 2019), CFD simulations are successfully validated against forced-oscillation model tests. In this paper, the feasibility of using CFD simulations for VIV response of a long flexible SLWR has been studied based on the CFD modeling practice developed in Part I. The CFD simulation is coupled with a simple structural model of the riser, and the structural equations of motions are solved via modal analysis. The simulation results capture all excitation frequencies measured from the model tests.
涡激振动是细长隔水管疲劳损伤的主要来源之一。利用半经验软件工具对立管进行了典型的VIV评估，其中截面水动力系数是由短刚性立管的强迫振荡模型试验得出的。带有浮力部分的钢制懒波隔水管(SLWR)是改善深水开发中疲劳性能的一个有吸引力的概念，但SLWR的水动力系数的模型试验数据有限。在本研究的第一部分(Jang & Kim, 2019)中，CFD模拟成功地针对强迫振荡模型试验进行了验证。本文基于第一部分的CFD建模实践，研究了利用CFD模拟长柔性SLWR涡激振动响应的可行性。将CFD模拟与立管的简单结构模型相结合，通过模态分析求解结构运动方程。仿真结果捕获了从模型试验中测量到的所有激励频率。
{"title":"Numerical Investigation for Vortex-Induced Vibrations of Steel-Lazy-Wave-Risers: Part II — CFD Study on Long Flexible Riser","authors":"Hyunchul Jang, Jang-Whan Kim","doi":"10.1115/omae2019-96404","DOIUrl":"https://doi.org/10.1115/omae2019-96404","url":null,"abstract":"\u0000 Vortex-Induced Vibration (VIV) is one of the main sources of fatigue damage for long slender risers. Typical VIV assessment of risers is conducted using semi-empirical software tools in which the sectional hydrodynamic coefficients are derived from forced oscillation model tests on short rigid risers. The Steel Lazy Wave Riser (SLWR) with buoyancy sections is an attractive concept for improving fatigue performance in deep water developments, but there is limited model test data available for the hydrodynamic coefficients on SLWR’s. In Part I of the present study (Jang & Kim, 2019), CFD simulations are successfully validated against forced-oscillation model tests. In this paper, the feasibility of using CFD simulations for VIV response of a long flexible SLWR has been studied based on the CFD modeling practice developed in Part I. The CFD simulation is coupled with a simple structural model of the riser, and the structural equations of motions are solved via modal analysis. The simulation results capture all excitation frequencies measured from the model tests.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"142 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":"114242166","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}
Dan pang, Huili Xi, Zhongbing Zhou, G. Tang, Lin Lu
This article presents numerical results of flow-induced rotary oscillation of a circular cylinder with rigid splitter plate in steady flow. Different from the previous examinations with freely rotatable assembly which mainly considered linear restoring force, the rotary oscillation of the structure in this work is modelled by a Duffing oscillator with both linear and nonlinear restoring force, denoted by dimensional k and ε, respectively. Numerical simulations were carried out for various reduced velocities Ur ∈ [9 to 15] and ε ∈ [0 to 20] at a relatively low Reynolds number. Our previous investigations of a purely linear oscillator (i.e., ε = 0) show that the equilibrium position of the rotary oscillation is not parallel to the free stream as the reduced velocity exceeds a critical value, that is, bifurcation occurs. The present numerical studies suggest that, for a specific reduced velocity Ur, the increase in the nonlinear stiffness ε can eliminate the undesirable bifurcation. The numerical results also suggest that both odd and even-number lift frequency components appear for bifurcate cases, while only odd-number lift frequencies are observed for non-bifurcate cases. The dynamic mode decompositions for the wake flow corresponding to each lift frequency are presented.
{"title":"Numerical Investigation of Steady Flow-Induced Rotary Response of Circular Cylinder With Splitter Plate","authors":"Dan pang, Huili Xi, Zhongbing Zhou, G. Tang, Lin Lu","doi":"10.1115/omae2019-95584","DOIUrl":"https://doi.org/10.1115/omae2019-95584","url":null,"abstract":"\u0000 This article presents numerical results of flow-induced rotary oscillation of a circular cylinder with rigid splitter plate in steady flow. Different from the previous examinations with freely rotatable assembly which mainly considered linear restoring force, the rotary oscillation of the structure in this work is modelled by a Duffing oscillator with both linear and nonlinear restoring force, denoted by dimensional k and ε, respectively. Numerical simulations were carried out for various reduced velocities Ur ∈ [9 to 15] and ε ∈ [0 to 20] at a relatively low Reynolds number. Our previous investigations of a purely linear oscillator (i.e., ε = 0) show that the equilibrium position of the rotary oscillation is not parallel to the free stream as the reduced velocity exceeds a critical value, that is, bifurcation occurs. The present numerical studies suggest that, for a specific reduced velocity Ur, the increase in the nonlinear stiffness ε can eliminate the undesirable bifurcation. The numerical results also suggest that both odd and even-number lift frequency components appear for bifurcate cases, while only odd-number lift frequencies are observed for non-bifurcate cases. The dynamic mode decompositions for the wake flow corresponding to each lift frequency are presented.","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":"133129367","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}
Shuang Wang, Ju Wei, Xuanshu Chen, Liwei Liu, Zhiguo Zhang
As a type of the ship stability failure modes, parametric rolling has attracted more attention from many researchers in recent years because of a series of accidents due to ship instability, especially the instability of container ship. Parametric rolling is a complex nonlinear stochastic dynamic problem, which is often accompanied by large amplitude vertical motions of ships. At present, there are many difficulties in the research of ship parameter rolling, mainly including the nonlinearity of parameter rolling motion, the random variation of wetted area of the hull surface up to the incident wave waterline and the coupling effect of rolling, pitching and heaving. Nowadays, the potential flow theory is a common method to predict parametric rolling, but this method may generate results with low accuracy in some conditions. This paper describes a numerical simulation method based on in-house CFD code HUST-Ship to analyze parametric rolling motion of KCS (KRISO Container Ship) container ship model. The paper studies the occurring conditions of parametric rolling motion of KCS model and reveals the mechanism of parametric rolling.
{"title":"Numerical Simulations of KCS Parametric Rolling in Head Waves","authors":"Shuang Wang, Ju Wei, Xuanshu Chen, Liwei Liu, Zhiguo Zhang","doi":"10.1115/omae2019-95563","DOIUrl":"https://doi.org/10.1115/omae2019-95563","url":null,"abstract":"\u0000 As a type of the ship stability failure modes, parametric rolling has attracted more attention from many researchers in recent years because of a series of accidents due to ship instability, especially the instability of container ship. Parametric rolling is a complex nonlinear stochastic dynamic problem, which is often accompanied by large amplitude vertical motions of ships. At present, there are many difficulties in the research of ship parameter rolling, mainly including the nonlinearity of parameter rolling motion, the random variation of wetted area of the hull surface up to the incident wave waterline and the coupling effect of rolling, pitching and heaving. Nowadays, the potential flow theory is a common method to predict parametric rolling, but this method may generate results with low accuracy in some conditions. This paper describes a numerical simulation method based on in-house CFD code HUST-Ship to analyze parametric rolling motion of KCS (KRISO Container Ship) container ship model. The paper studies the occurring conditions of parametric rolling motion of KCS model and reveals the mechanism of parametric rolling.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"2010 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":"123923158","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 horizontal motions of a moored offshore structure in waves are dominated by the resonance phenomena that occur at the natural frequencies of the system. Therefore, the maximum excursions of the structure depend on both the wave loads and the damping in the system. At present, potential flow calculations are employed for predicting the wave loads on offshore structures. However, such methods cannot predict hydrodynamic damping which is dominated by viscous effects. Therefore, the current practice in the industry is to obtain the low-frequency damping based on model testing. Nowadays, CFD simulations also have the potential to predict the low-frequency viscous damping of offshore structures in calm water. To obtain confidence in the accuracy of CFD simulations, a proper validation of the results of such CFD calculations is essential. In this paper, the flow around a forced surging or swaying LNGC is calculated using the CFD code ReFRESCO. The objective is to assess the accuracy and applicability of CFD for predicting the low-frequency viscous damping. After a description of the code and the used numerical methods, the results are presented and compared with results from model tests. Both inertia and damping coefficients are analyzed from the calculated hydrodynamics loads. Extensive numerical studies have been carried out to determine the influence of grid resolution, time step and iterative convergence on the flow solution and on the calculated damping. The numerical uncertainty of the results are assessed for one combination of amplitude and period for the surge motion. The CFD results are compared to experimental results indicating that the calculated damping coefficients agree within 5% for both surge and sway motion.
{"title":"URANS Predictions of Low-Frequency Damping of a LNGC","authors":"Frederick Jaouen, A. Koop, Lucas Vatinel","doi":"10.1115/omae2019-95171","DOIUrl":"https://doi.org/10.1115/omae2019-95171","url":null,"abstract":"\u0000 The horizontal motions of a moored offshore structure in waves are dominated by the resonance phenomena that occur at the natural frequencies of the system. Therefore, the maximum excursions of the structure depend on both the wave loads and the damping in the system. At present, potential flow calculations are employed for predicting the wave loads on offshore structures. However, such methods cannot predict hydrodynamic damping which is dominated by viscous effects. Therefore, the current practice in the industry is to obtain the low-frequency damping based on model testing. Nowadays, CFD simulations also have the potential to predict the low-frequency viscous damping of offshore structures in calm water. To obtain confidence in the accuracy of CFD simulations, a proper validation of the results of such CFD calculations is essential.\u0000 In this paper, the flow around a forced surging or swaying LNGC is calculated using the CFD code ReFRESCO. The objective is to assess the accuracy and applicability of CFD for predicting the low-frequency viscous damping. After a description of the code and the used numerical methods, the results are presented and compared with results from model tests. Both inertia and damping coefficients are analyzed from the calculated hydrodynamics loads. Extensive numerical studies have been carried out to determine the influence of grid resolution, time step and iterative convergence on the flow solution and on the calculated damping. The numerical uncertainty of the results are assessed for one combination of amplitude and period for the surge motion. The CFD results are compared to experimental results indicating that the calculated damping coefficients agree within 5% for both surge and sway motion.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"49 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":"124279010","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}
Bo-qian Yan, Shuangqiang Wang, Guiyong Zhang, Qihang Xiao, Peng Wang
Flow control is an attractive topic in consideration of its significance associated with drag reduction or vibration suppression in fluid-structure interaction (FSI) system. A circular cylinder with a flexible plate in the wake region has been investigated numerically. An immersed smoothed point interpolation method (IS-PIM) has been employed to solve this FSI system. The splitter plate with the same length as the cylinder diameter is placed horizontally in the wake region. The drag variation of the circular cylinder and the behavior of the vorticities have been studied with regard to different locations of the detached plate. A comparative study of the rigid plate control has been presented. It shows that the effect of the flexible plate control is inferior to the rigid plate control because the flow field of the former is more complicated than the latter. When the flexible plate is far from the cylinder relatively, it would produce an opposite effect.
{"title":"The Investigation of a Circular Cylinder With a Detached Flexible Plate Using Immersed Smoothed Point Interpolation Method","authors":"Bo-qian Yan, Shuangqiang Wang, Guiyong Zhang, Qihang Xiao, Peng Wang","doi":"10.1115/omae2019-95610","DOIUrl":"https://doi.org/10.1115/omae2019-95610","url":null,"abstract":"\u0000 Flow control is an attractive topic in consideration of its significance associated with drag reduction or vibration suppression in fluid-structure interaction (FSI) system. A circular cylinder with a flexible plate in the wake region has been investigated numerically. An immersed smoothed point interpolation method (IS-PIM) has been employed to solve this FSI system. The splitter plate with the same length as the cylinder diameter is placed horizontally in the wake region. The drag variation of the circular cylinder and the behavior of the vorticities have been studied with regard to different locations of the detached plate. A comparative study of the rigid plate control has been presented. It shows that the effect of the flexible plate control is inferior to the rigid plate control because the flow field of the former is more complicated than the latter. When the flexible plate is far from the cylinder relatively, it would produce an opposite effect.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"1696 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":"129392479","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}
Peng Zhou, Liwei Liu, Lixiang Guo, Qing Wang, Xianzhou Wang
This paper presents CFD simulation results of the stern flap effect with different lengths for hydrodynamic performance of catamaran moving in calm water, including resistance and sailing attitude. Inhouse viscous CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for the study. The catamaran with/without stern flap with different lengths were studied. The trim and sinkage of the catamaran were solved coupled with flow solver. Experimental studies in calm water were conducted to validate the numerical method. The comparison of hydrodynamic performance of catamaran with stern flaps of different lengths was made. The results show that the stern flap can reduce the sailing attitude and has influence for the resistance of catamaran at high-speed.
{"title":"Numerical Study on the Effect of Stern Flap for Hydrodynamic Performance of Catamaran","authors":"Peng Zhou, Liwei Liu, Lixiang Guo, Qing Wang, Xianzhou Wang","doi":"10.1115/omae2019-96819","DOIUrl":"https://doi.org/10.1115/omae2019-96819","url":null,"abstract":"\u0000 This paper presents CFD simulation results of the stern flap effect with different lengths for hydrodynamic performance of catamaran moving in calm water, including resistance and sailing attitude. Inhouse viscous CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for the study. The catamaran with/without stern flap with different lengths were studied. The trim and sinkage of the catamaran were solved coupled with flow solver. Experimental studies in calm water were conducted to validate the numerical method. The comparison of hydrodynamic performance of catamaran with stern flaps of different lengths was made. The results show that the stern flap can reduce the sailing attitude and has influence for the resistance of catamaran at high-speed.","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":"129264859","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 this paper, the dam-break problem is numerically simulated using two-phase moving particle semi-implicit (MPS) method. Firstly, the two-phase MPS method is extended from single-phase MPS method. The present method treats the multiphase system as a multi-density and multi-viscosity fluid, and a single set of equations could be used for the whole system. The interaction between particles of different phases is considered through the applications of inter-particle viscosity and density smoothing technique. The two-phase MPS method is then successfully applied to violent dam-break problem. The numerical results obtained by single-phase and two-phase method are both compared with experimental results in the open literature. The characteristics of air cavity are analyzed, including the pressure inside the cavity and the cavity shape deformation.
{"title":"Two-Phase MPS Method for Dam-Break Flows","authors":"Xiao Wen, D. Wan","doi":"10.1115/omae2019-95518","DOIUrl":"https://doi.org/10.1115/omae2019-95518","url":null,"abstract":"\u0000 In this paper, the dam-break problem is numerically simulated using two-phase moving particle semi-implicit (MPS) method. Firstly, the two-phase MPS method is extended from single-phase MPS method. The present method treats the multiphase system as a multi-density and multi-viscosity fluid, and a single set of equations could be used for the whole system. The interaction between particles of different phases is considered through the applications of inter-particle viscosity and density smoothing technique. The two-phase MPS method is then successfully applied to violent dam-break problem. The numerical results obtained by single-phase and two-phase method are both compared with experimental results in the open literature. The characteristics of air cavity are analyzed, including the pressure inside the cavity and the cavity shape deformation.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"554 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":"115965968","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}
Numerical Ventilation (NV) is a well-known problem that occurs when the Volume of Fluid method is used to model vessels with a bow that creates a small, acute entrance angle with the free surface. These are typical of both planing hulls and yachts. There is a general lack of discussion focusing upon Numerical Ventilation available within the public domain, which is attributable to the fact that it only affects such a niche area of naval architecture. The information available is difficult to find, often fleetingly mentioned in papers with a different focus. Numerical Ventilation may be considered one of the main sources of error in numerical simulations of planing hulls and as such warrants an in-depth analysis. This paper sets out to bring together the available work, as well as performing its own investigation into the problem to develop a better understanding of Numerical Ventilation and present alternate solutions. Additionally, the success and impact of different approaches is presented in an attempt to help other researchers avoid and correct for Numerical Ventilation. Interface smearing caused by the simulations inability to track the free surface is identified as the main source of Numerical Ventilation. This originates from the interface between the volume mesh and the prism layer mesh. This study looks into the interface to identify strategies that minimise Numerical Ventilation, presenting a novel solution to prism layer meshing that was found to have a positive impact. Through the implementation of a modified High Resolution Interface Capture (HRIC) scheme and the correct mesh refinements, it is possible to minimise the impact of Numerical Ventilation to a level that will not affect the results of a simulation and is acceptable for engineering applications.
{"title":"Strategies to Minimise Numerical Ventilation in CFD Simulations of High-Speed Planing Hulls","authors":"Angus Gray-Stephens, T. Tezdogan, S. Day","doi":"10.1115/OMAE2019-95784","DOIUrl":"https://doi.org/10.1115/OMAE2019-95784","url":null,"abstract":"\u0000 Numerical Ventilation (NV) is a well-known problem that occurs when the Volume of Fluid method is used to model vessels with a bow that creates a small, acute entrance angle with the free surface. These are typical of both planing hulls and yachts. There is a general lack of discussion focusing upon Numerical Ventilation available within the public domain, which is attributable to the fact that it only affects such a niche area of naval architecture. The information available is difficult to find, often fleetingly mentioned in papers with a different focus. Numerical Ventilation may be considered one of the main sources of error in numerical simulations of planing hulls and as such warrants an in-depth analysis. This paper sets out to bring together the available work, as well as performing its own investigation into the problem to develop a better understanding of Numerical Ventilation and present alternate solutions. Additionally, the success and impact of different approaches is presented in an attempt to help other researchers avoid and correct for Numerical Ventilation.\u0000 Interface smearing caused by the simulations inability to track the free surface is identified as the main source of Numerical Ventilation. This originates from the interface between the volume mesh and the prism layer mesh. This study looks into the interface to identify strategies that minimise Numerical Ventilation, presenting a novel solution to prism layer meshing that was found to have a positive impact. Through the implementation of a modified High Resolution Interface Capture (HRIC) scheme and the correct mesh refinements, it is possible to minimise the impact of Numerical Ventilation to a level that will not affect the results of a simulation and is acceptable for engineering applications.","PeriodicalId":345141,"journal":{"name":"Volume 2: CFD and FSI","volume":"3 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":"126236014","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 present study is concerned with predicting the resistance and vertical motions of the surface combatant DTMB5512 ship model in regular head waves. A series of numerical simulations are performed for various wave lengths, heights and different ship speeds. Computations are performed by making use of the ISIS-CFD solver of the commercial software Fine™/Marine provided by NUMECA, where the discretization in space is based on finite volume method using unstructured grid. The unsteady Reynolds-Averaged Navier-Stokes equations are numerically solved while the turbulence is modeled by making use of the k-ω SST model. The free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. Computed results are validated through direct comparisons with the experimental data provided by IIHR test cases. For the sake of numerical results verification, a grid convergence study is performed on four computational grids and a time step convergence test is also included. Validation of the numerical results shows a reasonable agreement with the experimental data.
本文研究了水面战舰DTMB5512舰模在常规头浪中阻力和垂直运动的预测问题。在不同波长、不同高度和不同航速条件下进行了一系列数值模拟。利用NUMECA提供的商业软件Fine™/Marine的ISIS-CFD求解器进行计算，其中空间离散是基于使用非结构化网格的有限体积法。对非定常reynolds - average Navier-Stokes方程进行了数值求解，并利用k-ω海表温度模型对湍流进行了模拟。自由表面通过基于流体体积(VOF)方法的空气-水界面捕获。通过与IIHR测试用例提供的实验数据的直接比较，验证了计算结果。为了验证数值结果，在四个计算网格上进行了网格收敛性研究，并进行了时间步长收敛性测试。数值计算结果与实验数据吻合较好。
{"title":"Numerical Simulation for Predicting Ship Resistance and Vertical Motions in Regular Head Waves","authors":"A. Bekhit, A. Lungu","doi":"10.1115/omae2019-95237","DOIUrl":"https://doi.org/10.1115/omae2019-95237","url":null,"abstract":"\u0000 The present study is concerned with predicting the resistance and vertical motions of the surface combatant DTMB5512 ship model in regular head waves. A series of numerical simulations are performed for various wave lengths, heights and different ship speeds. Computations are performed by making use of the ISIS-CFD solver of the commercial software Fine™/Marine provided by NUMECA, where the discretization in space is based on finite volume method using unstructured grid. The unsteady Reynolds-Averaged Navier-Stokes equations are numerically solved while the turbulence is modeled by making use of the k-ω SST model. The free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. Computed results are validated through direct comparisons with the experimental data provided by IIHR test cases. For the sake of numerical results verification, a grid convergence study is performed on four computational grids and a time step convergence test is also included. Validation of the numerical results shows a reasonable agreement with the experimental data.","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":"130726053","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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