跃移砂粒起跳的受力机制   总被引：4，自引：1，他引：3  

贺大良  刘大有 《中国沙漠》1989,9(2):14-22

根据作者拍摄的高速电影摄影实验发现, 沙粒起跳后垂直加速度均为负值, 亦即沙粒跳离地面后再无大于重力的、向上的外力作用于其上, 从而排除了八种起跳学说中的五种有关非接触力的起动学说, 即: 升力起动说、压差起动说、湍流起动说, 负压起动说和涡旋起动说。在余下的三种有关接触力的起动学说中, 作者估算后认为: 跃移起跳是斜面飞升与冲击碰撞相结合作用的结果。在凸凹不平的地面上滚动的沙粒只需很小的速度(厘米/秒量级)就可离地而去, 并从风中获取更多的能量。在地面上滚动或在空中飞行的沙粒, 以不同的角度冲击其它颗粒, 能以锐角和钝角反弹飞开。运动沙粒的动能只需有1/10转换为转动动能, 就可使沙粒获得数百以至上千转/秒的转速。  相似文献   

利用网格划分软件和缓坡方程计算港内波浪场     

谭丽  滕斌  赵明 《海洋工程》2004,22(4):107-114

提出了一套可方便应用于波浪场计算的方法。该方法包含了准确的边界输入输出技术,简便的地形输入技术,高质量的计算网格生成以及加速查寻、排序的数据结构。应用双曲型缓坡方程计算了港湾内的波浪场,数值计算时提出了处理建筑物表面部分反射边界条件的方法。将计算结果与边界元方法的结果和实验值进行了比较,证明该方法应用于波浪场可得到较理想的结果。对大连港区内的波浪折射绕射进行了计算,表明本方法可以应用于实际港口的波浪场计算中。  相似文献   

下导风工程的风洞实验研究——[1]平面上的实验     

刘贤万  凌裕泉  贺大良  陈福生 《中国沙漠》1982,2(4):14-21

下导风工程是由栅栏工程发展而来的,它应用于防治风沙、风雪对道路(铁路、公路)的危害,国内外已做过不少工作^[1][2][3]。但是,在风洞中进行系统的实验研究还很少。我们从1969年开始,先后对下导风工程防治道路风沙(雪)危害,进行了一系列的风洞模似实验研究,取得了初步成果。  相似文献   

Efficient Simulation of Freak Waves in Random Oceanic Sea States   总被引：1，自引：0，他引：1  

张运秋  胡金鹏  张宁川 《中国海洋工程》2009,23(1)

Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum.The evolution of initial random wave trains is numerically carried out within the framework of the modified fourorder nonlinear Schruedinger equation (mNLSE),and some involved influence factors are also discussed.Results show that if the sideband instability is satisfied,a random wave train may evolve into a freak wave train,and simultaneously the setting of the Phillips parameter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves.The way to increase the generation efficiency of freak waves thsough changing the involved parameters is also presented.  相似文献   

2-D Numerical Simulation of Natural Gas Hydrate Decomposition Through Depressurization by Fully Implicit Method   总被引：1，自引：0，他引：1  

宋永臣  梁海峰 《中国海洋工程》2009,23(3):529-542

Natural gas hydrate, as a potential energy resource, deposits in permafrost and marine sediment with large quantities. The current exploitation methods include depressurization, thermal stimulation, and inhibitor injection. However, many issues have to be resolved before the commercial production. In the present study, a 2-D axisymmetric simulator for gas production from hydrate reservoirs is developed. The simulator includes equations of conductive and convective heat transfer, kinetic of hydrate decomposi...  相似文献   

Reliability-Based Full-Life Cycle Optimum Design of Offshore Jacket Platform     

王立成  宋玉普 《中国海洋工程》2004,18(1):47-58

Based on the consideration of operation environment and structural property, an optimnm design model of offshore jacket platform is developed in this paper, namely, the reliability-based full-life cycle optimum design model. In this model, the time-dependent reliability assessment method for structural members is established by combination of the decrease, of sectional size and performance deterioration of material. The initial investment, maintenance cost and failure loss cost are assembled into the model. The total cost of the platform structure system in its full service period is chosen as the objective function, and the initial reliabilities of the layer elements partitioned in advance are taken as the design variables. Different models are obtained, depending on whether the system reliability eonstraint is considered or not. This optimum design model can result in the lowest full-life cost and the optimal initial layer reliability of an offshore jacket platform in the design of marine structures. The feasibility of this model is illustrated with an actual jacket platform in the Liaodong Gulf as an example.  相似文献   

Simulation of Fully Nonlinear 3-D Numerical Wave Tank   总被引：6，自引：0，他引：6  

张晓兔滕斌  宁德志 《中国海洋工程》2004,18(1):59-68

A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order bouodary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.  相似文献