The suitability of computational fluid dynamics (CFD) for marine renewable energy research and development and in particular for simulating extreme wave interaction with a wave energy converter (WEC) is considered. Fu...The suitability of computational fluid dynamics (CFD) for marine renewable energy research and development and in particular for simulating extreme wave interaction with a wave energy converter (WEC) is considered. Fully nonlinear time domain CFD is often considered to be an expensive and computationally intensive option for marine hydrodynamics and frequency-based methods are traditionally preferred by the industry. However, CFD models capture more of the physics of wave-structure interaction, and whereas traditional frequency domain approaches are restricted to linear motions, fully nonlinear CFD can simulate wave breaking and overtopping. Furthermore, with continuing advances in computing power and speed and the development of new algorithms for CFD, it is becoming a more popular option for design applications in the marine environment. In this work, different CFD approaches of increasing novelty are assessed: two commercial CFD packages incorporating recent advances in high resolution free surface flow simulation;a finite volume based Euler equation model with a shock capturing technique for the free surface;and meshless Smoothed Particle Hydrodynamics (SPH) method. These different approaches to fully nonlinear time domain simulation of free surface flow and wave structure interaction are applied to test cases of increasing complexity and the results compared with experimental data. Results are presented for regular wave interaction with a fixed horizontal cylinder, wave generation by a cone in driven vertical motion at the free surface and extreme wave interaction with a bobbing float (The Manchester Bobber WEC). The numerical results generally show good agreement with the physical experiments and simulate the wave-structure interaction and wave loading satisfactorily. The grid-based methods are shown to be generally less able than the meshless SPH to capture jet formation at the face of the cone, the resolution of the jet being grid dependent.展开更多
The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon ...The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.展开更多
The hydrodynamic damper is a device to decrease the motion of armament carrier by use of the water resistance. When hydrodynamic damper rushes into the water channel with high velocity, it is a complicated flow phenom...The hydrodynamic damper is a device to decrease the motion of armament carrier by use of the water resistance. When hydrodynamic damper rushes into the water channel with high velocity, it is a complicated flow phenomenon with fluid-structure interaction, free surface and moving interface. Numerical simulation using the Smoothed Particle Hydrodynamics （SPH） method coupled with the Finite Element （FE） method was successfully conducted to predict the dynamic characteristics of hydrodynamic damper. The water resistance, the pressure in the interface and the stress of structure were investigated, and the relationship among the peak of water resistance, initial velocity and actual draught was also discussed. The empirical formula was put forward to predict the water resistance. And it is found that the resistance coefficient is commonly in the range of 0.3 ≤ C ≤ 0.5, when the initial velocity is larger than 50 m/s. It can be seen that the SPH method coupled with the FE method has many obvious advantages over other numerical methods for this complicated flow problem with fluid-structure interaction.展开更多
文摘The suitability of computational fluid dynamics (CFD) for marine renewable energy research and development and in particular for simulating extreme wave interaction with a wave energy converter (WEC) is considered. Fully nonlinear time domain CFD is often considered to be an expensive and computationally intensive option for marine hydrodynamics and frequency-based methods are traditionally preferred by the industry. However, CFD models capture more of the physics of wave-structure interaction, and whereas traditional frequency domain approaches are restricted to linear motions, fully nonlinear CFD can simulate wave breaking and overtopping. Furthermore, with continuing advances in computing power and speed and the development of new algorithms for CFD, it is becoming a more popular option for design applications in the marine environment. In this work, different CFD approaches of increasing novelty are assessed: two commercial CFD packages incorporating recent advances in high resolution free surface flow simulation;a finite volume based Euler equation model with a shock capturing technique for the free surface;and meshless Smoothed Particle Hydrodynamics (SPH) method. These different approaches to fully nonlinear time domain simulation of free surface flow and wave structure interaction are applied to test cases of increasing complexity and the results compared with experimental data. Results are presented for regular wave interaction with a fixed horizontal cylinder, wave generation by a cone in driven vertical motion at the free surface and extreme wave interaction with a bobbing float (The Manchester Bobber WEC). The numerical results generally show good agreement with the physical experiments and simulate the wave-structure interaction and wave loading satisfactorily. The grid-based methods are shown to be generally less able than the meshless SPH to capture jet formation at the face of the cone, the resolution of the jet being grid dependent.
基金The work described in this paper is supported by the National Natural Science Foundation of China(Grant Nos.52278455 and 52311530685)the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(21SG24)+1 种基金the International Cooperation Project of Science and Technology Commission of Shanghai Municipality(No.22210710700)the Fundamental Research Funds for the Central Universities.
文摘The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.
文摘The hydrodynamic damper is a device to decrease the motion of armament carrier by use of the water resistance. When hydrodynamic damper rushes into the water channel with high velocity, it is a complicated flow phenomenon with fluid-structure interaction, free surface and moving interface. Numerical simulation using the Smoothed Particle Hydrodynamics （SPH） method coupled with the Finite Element （FE） method was successfully conducted to predict the dynamic characteristics of hydrodynamic damper. The water resistance, the pressure in the interface and the stress of structure were investigated, and the relationship among the peak of water resistance, initial velocity and actual draught was also discussed. The empirical formula was put forward to predict the water resistance. And it is found that the resistance coefficient is commonly in the range of 0.3 ≤ C ≤ 0.5, when the initial velocity is larger than 50 m/s. It can be seen that the SPH method coupled with the FE method has many obvious advantages over other numerical methods for this complicated flow problem with fluid-structure interaction.
