Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and...Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）.展开更多
In this paper, the buoyancy, kinetic properties and stability of air floated structures have been studied by theoretical and experimental methods. The equations for calculation of the buoyancy of the air floated buoy ...In this paper, the buoyancy, kinetic properties and stability of air floated structures have been studied by theoretical and experimental methods. The equations for calculation of the buoyancy of the air floated buoy are derived according to the Boyler law and the equilibrium equations of the air floated structure are established. Through simplification of the air floated structure as a single freedom rigid body and spring system, the natural period of heaving and some kinetic properties are discussed. In the stability analysis, the formulas for calculation of the meta centric height are presented. The theoretical results are in good agreement with the data observed from the model test and prototype test. The air buoyancy decrease coefficient presented in this paper has a large influence on the floating state, stability and dynamic properties of the air floated structure. The stability of the air floated structure can also be judged by the parameter of meta centric height, and calculations show that the air floated structure is less stable than the conventional float.展开更多
In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform ba...In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform based on a model test simultaneously. Furthermore, the dynamic equivalence between the truncated and full-depth mooring system is still a tuff work. However, the wind and current loads can be tested accurately in wind tunnel model. Furthermore, the wave can be simulated accurately in wave tank test. The full-scale mooring system and the all environment loads can be simulated accurately by using the numerical model based on the model tests simultaneously. In this paper, the air gap response of a floating platform is calculated based on the results of tunnel test and wave tank. Meanwhile, full-scale mooring system, the wind, wave and current load can be considered simultaneously. In addition, a numerical model of the platform is tuned and validated by ANSYS AQWA according to the model test results. With the support of the tuned numerical model, seventeen simulation cases about the presented platform are considered to study the wave, wind, and current loads simultaneously. Then, the impact analysis studies of air gap motion regarding the length, elasticity, and type of the mooring line are performed in the time domain under the beam wave, head wave, and oblique wave conditions.展开更多
It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up a...It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.展开更多
为了更好探测识别与跟踪空飘球,考虑到空飘球运动与环境风的高度相关性,综合应用雷达探测定位、风场反演技术提出一种预测空飘球轨迹并判断其载荷的方法。基于当下主流的速度平面处理方法提出双体积单元风场反演方案。方案中,通过建立...为了更好探测识别与跟踪空飘球,考虑到空飘球运动与环境风的高度相关性,综合应用雷达探测定位、风场反演技术提出一种预测空飘球轨迹并判断其载荷的方法。基于当下主流的速度平面处理方法提出双体积单元风场反演方案。方案中,通过建立空飘球流体力学分析下的动力学模型实现空飘球在空轨迹的预测;引入轨迹惯性度(degree of inertia,DOI)和质阻比计算空飘球空载状态下理论轨迹与实际轨迹的差异,分析其自身空飘属性与携带载荷状况。通过仿真实验验证所提方法,结果表明所提风场反演方法各方向风场反演平均绝对误差在0.1以下,轨迹预测误差小于0.162,且在随机观测误差下展现了较好的鲁棒性;通过DOI值能有效判断空飘球带载有无的情况且判断结果受风场观测误差影响较小,相较于空载状态,载荷质量增加1%时DOI值增加16倍,并能较好表现空飘球与载荷之间的质量分布关系,且当载荷质量占比7%以上时DOI判据更为有效;同时通过DOI值能用于判断空飘球是否具备自主动力,根据仿真结果可以认为DOI值大于202,表明空飘球可能具备自主动力。展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51309179)the National High Technology Research and Development Program of China(863 Program,Grant No.2012AA051705)+2 种基金the International S&T Cooperation Program of China(Grant No.2012DFA70490)the State Key Laboratory of Hydraulic Engineering Simulation and Safety(Tianjin University)the Tianjin Municipal Natural Science Foundation(Grant No.13JCYBJC19100)
文摘Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）.
文摘In this paper, the buoyancy, kinetic properties and stability of air floated structures have been studied by theoretical and experimental methods. The equations for calculation of the buoyancy of the air floated buoy are derived according to the Boyler law and the equilibrium equations of the air floated structure are established. Through simplification of the air floated structure as a single freedom rigid body and spring system, the natural period of heaving and some kinetic properties are discussed. In the stability analysis, the formulas for calculation of the meta centric height are presented. The theoretical results are in good agreement with the data observed from the model test and prototype test. The air buoyancy decrease coefficient presented in this paper has a large influence on the floating state, stability and dynamic properties of the air floated structure. The stability of the air floated structure can also be judged by the parameter of meta centric height, and calculations show that the air floated structure is less stable than the conventional float.
文摘In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform based on a model test simultaneously. Furthermore, the dynamic equivalence between the truncated and full-depth mooring system is still a tuff work. However, the wind and current loads can be tested accurately in wind tunnel model. Furthermore, the wave can be simulated accurately in wave tank test. The full-scale mooring system and the all environment loads can be simulated accurately by using the numerical model based on the model tests simultaneously. In this paper, the air gap response of a floating platform is calculated based on the results of tunnel test and wave tank. Meanwhile, full-scale mooring system, the wind, wave and current load can be considered simultaneously. In addition, a numerical model of the platform is tuned and validated by ANSYS AQWA according to the model test results. With the support of the tuned numerical model, seventeen simulation cases about the presented platform are considered to study the wave, wind, and current loads simultaneously. Then, the impact analysis studies of air gap motion regarding the length, elasticity, and type of the mooring line are performed in the time domain under the beam wave, head wave, and oblique wave conditions.
基金Sponsored by Science and Technology Project of Liaoning Province(Grant No.L2013113)the Fundamental Research Funds for the Central Universities(Grant No.N140703002)
文摘It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.
文摘为了更好探测识别与跟踪空飘球,考虑到空飘球运动与环境风的高度相关性,综合应用雷达探测定位、风场反演技术提出一种预测空飘球轨迹并判断其载荷的方法。基于当下主流的速度平面处理方法提出双体积单元风场反演方案。方案中,通过建立空飘球流体力学分析下的动力学模型实现空飘球在空轨迹的预测;引入轨迹惯性度(degree of inertia,DOI)和质阻比计算空飘球空载状态下理论轨迹与实际轨迹的差异,分析其自身空飘属性与携带载荷状况。通过仿真实验验证所提方法,结果表明所提风场反演方法各方向风场反演平均绝对误差在0.1以下,轨迹预测误差小于0.162,且在随机观测误差下展现了较好的鲁棒性;通过DOI值能有效判断空飘球带载有无的情况且判断结果受风场观测误差影响较小,相较于空载状态,载荷质量增加1%时DOI值增加16倍,并能较好表现空飘球与载荷之间的质量分布关系,且当载荷质量占比7%以上时DOI判据更为有效;同时通过DOI值能用于判断空飘球是否具备自主动力,根据仿真结果可以认为DOI值大于202,表明空飘球可能具备自主动力。
