Direct time-domain simulation of floating structures has advantages:it can calculate wave pressure fields and forces directly; and it is useful for coupled analysis of floating structures with a mooring system. A time...Direct time-domain simulation of floating structures has advantages:it can calculate wave pressure fields and forces directly; and it is useful for coupled analysis of floating structures with a mooring system. A time-domain boundary integral equation method is presented to simulate three-dimensional water wave radiation problems. A stable form of the integration free-surface boundary condition (IFBC) is used to update velocity potentials on the free surface. A multi-transmitting formula (MTF) method with an artificial speed is introduced to the artificial radiation boundary (ARB). The method was applied to simulate a semi-spherical liquefied natural gas (LNG) carrier and a semi-submersible undergoing specified harmonic motion. Numerical parameters such as the form of the ARB, and the time and space discretization related to this method are discussed. It was found that a good agreement can be obtained when artificial speed is between 0.6 and 1.6 times the phase velocity of water waves in the MTF method. A simulation can be done for a long period of time by this method without problems of instability, and the method is also accurate and computationally efficient.展开更多
Due to the continuous low temperature during the early-nursery period in most tobacco-growing areas in Guizhou Province, the tobacco seed germinate slow-ly, the nursery period is prolonged, the quality of tobacco seed...Due to the continuous low temperature during the early-nursery period in most tobacco-growing areas in Guizhou Province, the tobacco seed germinate slow-ly, the nursery period is prolonged, the quality of tobacco seedlings are not that good, the transplanting is delayed, etc. A comparative test of intensive closed-type floating-seedling system and conventional floating-seedling system was carried out in this study. The results showed that the intensive closed-type floating system could shorten significantly the nursery period; enhance the growth of tobacco seedlings;improve significantly the appearance of agronomic traits, such as number of leaves, stem height, stem diameter, fresh weight of leaves, etc; increase slightly the chloro-phyl content in seedlings. However, the root fresh weight and root vigor of seedlings nursed with the intensive closed-type float system were lower than that of seedlings nursed with the conventional float system. The intensive closed-type float system had a certain application potential in tobacco production.展开更多
An innovative hydrodynamic theory and numerical model were developed to help improve the efficiency, accuracy, and convergence of the numerical prediction of wave drift forces on two side-by-side deepwater floating bo...An innovative hydrodynamic theory and numerical model were developed to help improve the efficiency, accuracy, and convergence of the numerical prediction of wave drift forces on two side-by-side deepwater floating bodies. The wave drift forces were expressed by the double integration of source strength and the corresponding Green function on the body surface, which is consistent with the far field formula based on momentum conservation and sharing the advantage of near field calculations providing the drift force on each body. Numerical results were validated through comparing the general far field model and pressure integral model, as well as the middle field model developed usin^z the software HydroStar.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.10572041,50779008 and the 111 Project
文摘Direct time-domain simulation of floating structures has advantages:it can calculate wave pressure fields and forces directly; and it is useful for coupled analysis of floating structures with a mooring system. A time-domain boundary integral equation method is presented to simulate three-dimensional water wave radiation problems. A stable form of the integration free-surface boundary condition (IFBC) is used to update velocity potentials on the free surface. A multi-transmitting formula (MTF) method with an artificial speed is introduced to the artificial radiation boundary (ARB). The method was applied to simulate a semi-spherical liquefied natural gas (LNG) carrier and a semi-submersible undergoing specified harmonic motion. Numerical parameters such as the form of the ARB, and the time and space discretization related to this method are discussed. It was found that a good agreement can be obtained when artificial speed is between 0.6 and 1.6 times the phase velocity of water waves in the MTF method. A simulation can be done for a long period of time by this method without problems of instability, and the method is also accurate and computationally efficient.
基金Supported by Research on and Application of Flue-cured Tobacco Float System in Guizhou Province(2013-08)~~
文摘Due to the continuous low temperature during the early-nursery period in most tobacco-growing areas in Guizhou Province, the tobacco seed germinate slow-ly, the nursery period is prolonged, the quality of tobacco seedlings are not that good, the transplanting is delayed, etc. A comparative test of intensive closed-type floating-seedling system and conventional floating-seedling system was carried out in this study. The results showed that the intensive closed-type floating system could shorten significantly the nursery period; enhance the growth of tobacco seedlings;improve significantly the appearance of agronomic traits, such as number of leaves, stem height, stem diameter, fresh weight of leaves, etc; increase slightly the chloro-phyl content in seedlings. However, the root fresh weight and root vigor of seedlings nursed with the intensive closed-type float system were lower than that of seedlings nursed with the conventional float system. The intensive closed-type float system had a certain application potential in tobacco production.
基金Supported by National Natural Science Foundation of China (51079032)
文摘An innovative hydrodynamic theory and numerical model were developed to help improve the efficiency, accuracy, and convergence of the numerical prediction of wave drift forces on two side-by-side deepwater floating bodies. The wave drift forces were expressed by the double integration of source strength and the corresponding Green function on the body surface, which is consistent with the far field formula based on momentum conservation and sharing the advantage of near field calculations providing the drift force on each body. Numerical results were validated through comparing the general far field model and pressure integral model, as well as the middle field model developed usin^z the software HydroStar.
