In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, m...In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, mooring system, and floaters are solved by the Runge-Kutta fifth-order method. For the verification of the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and experimental results, it can be found that the simulated and experimental results agree well in each condition. Then, the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed. According to the simulated results, it can be found that with the increase of submerged depth of grid, the forces acting on mooring lines and bridle lines increase, while the forces on grid lines decrease; the horizontal motion amplitudes of floating collar decrease obviously, while the vertical motion amplitudes of floating collar change little. When the direction of incident wave propagation changes, forces on mooring lines and motion of net cage also change accordingly. When the propagation direction of incident wave changes from 0° to 45°, forces on the main ropes and bridle ropes increase, while the forces on the grid ropes decrease. With the increasing propagation direction of incident wave, the horizontal amplitude of the forces collar decreases, while the vertical amplitude of the floating collar has little variation.展开更多
The finite volume method has been successfully applied in several engineering fields and has shown outstanding performance in fluid dynamics simulation. In this paper, the general framework for the simulation ofnear-w...The finite volume method has been successfully applied in several engineering fields and has shown outstanding performance in fluid dynamics simulation. In this paper, the general framework for the simulation ofnear-wellbore systems using the finite volume method is described. The mathematical model and the numerical model developed by the authors are presented and discussed. A radial geometry in the vertical plane was implemented so as to thoroughly describe near-wellbore phenomena. The model was then used to simulate injection tests in an oil reservoir through a horizontal well and proved very powerful to correctly reproduce the transient pressure behavior. The reason for this is the robustness of the method, which is independent of the gridding options because the discretization is performed in the physical space. The model is able to describe the phenomena taking place in the reservoir even in complex situations, i.e. in the presence of heterogeneities and permeability barriers, demonstrating the flexibility of the finite volume method when simulating non-conventional tests. The results are presented in comparison with those obtained with the finite difference numerical approach and with analytical methods, if possible.展开更多
An Eulerian flux-form advection scheme, called the Two-step Shape-Preserving Advection Scheme （TSPAS）, was generalized and implemented on a spherical icosahedral hexagonal grid （also referred to as a geodesic grid...An Eulerian flux-form advection scheme, called the Two-step Shape-Preserving Advection Scheme （TSPAS）, was generalized and implemented on a spherical icosahedral hexagonal grid （also referred to as a geodesic grid） to solve the transport equation. The C grid discretization was used for the spatial discretization. To implement TSPAS on an unstructured grid, the original finite-difference scheme was further generalized. The two-step integration utilizes a combination of two separate schemes （a low-order monotone scheme and a high-order scheme that typically cannot ensure monotonicity） to calculate the fluxes at the cell walls （one scheme corresponds to one cell wall）. The choice between these two schemes for each edge depends on a pre-updated scalar value using slightly increased fluxes. After the determination of an appropriate scheme, the final integration at a target cell is achieved by summing the fluxes that are computed by the different schemes. The conservative and shape-preserving properties of the generalized scheme are demonstrated. Numerical experiments are conducted at several horizontal resolutions. TSPAS is compared with the Flux Corrected Transport （FCT） approach to demonstrate the differences between the two methods, and several transport tests are performed to examine the accuracy, efficiency and robustness of the two schemes.展开更多
Variable distributed energy resources (DERs) such as photovoltaic (PV) systems and wind power systems require additional power resources to control the balance between supply and demand. Battery energy storage systems...Variable distributed energy resources (DERs) such as photovoltaic (PV) systems and wind power systems require additional power resources to control the balance between supply and demand. Battery energy storage systems (BESSs) are one such possible resource for providing grid stability. It has been proposed that decentralized BESSs could help support microgrids (MGs) with intelligent control when advanced functionalities are implemented with variable DERs. One key challenge is developing and testing smart inverter controls for DERs. This paper presents a standardized method to test the interoperability and functionality of BESSs. First, a survey of grid-support standards prevalent in several countries was conducted. Then, the following four interoperability functions defined in IEC TR 61850-90-7 were tested: the specified active power from storage test (INV4), the var-priority Volt/VAR test (VV) and the specified power factor test (INV3) and frequency-watt control (FW). This study then out-lines the remaining technical issues related to basic BESS smart inverter test protocols.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50809014)the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA100301)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.200801411094)
文摘In this paper, the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory, and then the motion equations of floating system, net system, mooring system, and floaters are solved by the Runge-Kutta fifth-order method. For the verification of the numerical model, a series of physical model tests have been carried out. According to the comparisons between the simulated and experimental results, it can be found that the simulated and experimental results agree well in each condition. Then, the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed. According to the simulated results, it can be found that with the increase of submerged depth of grid, the forces acting on mooring lines and bridle lines increase, while the forces on grid lines decrease; the horizontal motion amplitudes of floating collar decrease obviously, while the vertical motion amplitudes of floating collar change little. When the direction of incident wave propagation changes, forces on mooring lines and motion of net cage also change accordingly. When the propagation direction of incident wave changes from 0° to 45°, forces on the main ropes and bridle ropes increase, while the forces on the grid ropes decrease. With the increasing propagation direction of incident wave, the horizontal amplitude of the forces collar decreases, while the vertical amplitude of the floating collar has little variation.
文摘The finite volume method has been successfully applied in several engineering fields and has shown outstanding performance in fluid dynamics simulation. In this paper, the general framework for the simulation ofnear-wellbore systems using the finite volume method is described. The mathematical model and the numerical model developed by the authors are presented and discussed. A radial geometry in the vertical plane was implemented so as to thoroughly describe near-wellbore phenomena. The model was then used to simulate injection tests in an oil reservoir through a horizontal well and proved very powerful to correctly reproduce the transient pressure behavior. The reason for this is the robustness of the method, which is independent of the gridding options because the discretization is performed in the physical space. The model is able to describe the phenomena taking place in the reservoir even in complex situations, i.e. in the presence of heterogeneities and permeability barriers, demonstrating the flexibility of the finite volume method when simulating non-conventional tests. The results are presented in comparison with those obtained with the finite difference numerical approach and with analytical methods, if possible.
基金supported by the National Natural Science Foundation of China(Grant No.41505066)the Basic Scientific Research and Operation Foundation of Chinese Academy Meteorological Sciences(Grant Nos.2015Z002,2015Y005)the National Research and Development Key Program:Global Change and Mitigation Strategies(No.2016YFA0602101)
文摘An Eulerian flux-form advection scheme, called the Two-step Shape-Preserving Advection Scheme （TSPAS）, was generalized and implemented on a spherical icosahedral hexagonal grid （also referred to as a geodesic grid） to solve the transport equation. The C grid discretization was used for the spatial discretization. To implement TSPAS on an unstructured grid, the original finite-difference scheme was further generalized. The two-step integration utilizes a combination of two separate schemes （a low-order monotone scheme and a high-order scheme that typically cannot ensure monotonicity） to calculate the fluxes at the cell walls （one scheme corresponds to one cell wall）. The choice between these two schemes for each edge depends on a pre-updated scalar value using slightly increased fluxes. After the determination of an appropriate scheme, the final integration at a target cell is achieved by summing the fluxes that are computed by the different schemes. The conservative and shape-preserving properties of the generalized scheme are demonstrated. Numerical experiments are conducted at several horizontal resolutions. TSPAS is compared with the Flux Corrected Transport （FCT） approach to demonstrate the differences between the two methods, and several transport tests are performed to examine the accuracy, efficiency and robustness of the two schemes.
文摘Variable distributed energy resources (DERs) such as photovoltaic (PV) systems and wind power systems require additional power resources to control the balance between supply and demand. Battery energy storage systems (BESSs) are one such possible resource for providing grid stability. It has been proposed that decentralized BESSs could help support microgrids (MGs) with intelligent control when advanced functionalities are implemented with variable DERs. One key challenge is developing and testing smart inverter controls for DERs. This paper presents a standardized method to test the interoperability and functionality of BESSs. First, a survey of grid-support standards prevalent in several countries was conducted. Then, the following four interoperability functions defined in IEC TR 61850-90-7 were tested: the specified active power from storage test (INV4), the var-priority Volt/VAR test (VV) and the specified power factor test (INV3) and frequency-watt control (FW). This study then out-lines the remaining technical issues related to basic BESS smart inverter test protocols.
