边界层

An asymptotic series solution is constructed by the perturbation technique of deflection type for buckling and postbuckling behaviors of the cylindrical shells under external pressure.

考虑到边界效应对中短圆柱壳的影响及边值问题摄动解的一致性，详细研究了该圆柱壳端部边界层方程和奇异摄动解，以便与中部正则摄动解相匹配。

But in 1744,d\'Alembert found that if we consider the fluid as no viscosity,the results of the theoretical analysis are different from the experiment.

实验表明粘性流体的运动，在区域内部趋向于理想流体的流动，在边界附近表现为边界层的流动。

In this paper, a least-square collocation formulation for solving Helmholtz equation with Dirichlet and Neumann boundary conditions was established.

对于Helmholtz方程问题，其微分方程和边界条件可表示为法应用于Helmholtz方程问题的研究，建立了 Helmholtz方程问题的最小二乘配点格式，分别研究了Hdmholtz方程的波传播问题和边界层问题。

The transformation method of solution, initial and boundary conditions of the 3DB LE are discussed.

讨论了边界层方程组的变换与求解，以及方程组求解的边界条件与起始条件的确定方法。

Magnetopause is the boundary layer formed by the interaction of solar wind with magnetosphere, and current flows upon it.

磁层顶是由经过舷激波的太阳风和地磁层相互作用而形成的边界层，其上有电流流动。

As the tetrahedral grids exist in the majority area, the pentahedral prism grids are adopted near the boundary, which meets the SST model's requirement of mesh in the boundary layer. Pressure recovery factors under different number of grids are calculated so as to decrease the error from coarse mesh, then the suitable number of grids is obtained.

流场大部分区域为四面体网格，在边界附近采用加密的五面体棱柱型网格，满足了SST模型对边界层网格的要求；为了减少网格过粗引起的汁算误差，还通过计算不同网格数下尾水管的压力恢复系数来优选出合适的网格数目。

It is found that the information entropy and exponent of power spectrum are two powerful indexes to distinguish the atmospheric turbulence in boundary layer and the explanation for difference ...

结果表明，信息熵和功率谱指数是区别稳定层结和不稳定层结大气边界层湍流特征的指标，对造成两者之间的差别做出了对应的解释。

Based on Prandtl's momentum transportation, this paper calculates in detail the physical quantities such as eddy viscosities, and ratio of eddy viscosity to motion viscosity, total stresses with respect to relative position in three regions of viscous sub-layer, buffer layer, and main turbulent stream for non-Newtonian fluid flowing turbulently in ducts, which according to Karman's three layer models and measurement of fluid parameters in evaluation apparatus, discusses the influence of polymer drag reduction on flowing properties of non-Newton fluid, analyzes quantitatively principle of turbulent reduction phenomenon and condition of increasing reduction rate.

摘要以普兰德动量传递理论为基础，按照卡门的三层模型，通过室内模拟环道用0号柴油及加入减阻剂在圆管内的流动参数的测定，计算了非牛顿型流体管内湍流边界层的层流内层、过渡层、湍流中心的涡流粘度，涡流粘度与运动粘度比、总应力随相对位置的变化等定量参数，探讨了高分子减阻剂对非牛顿流体流动特性的影响，对湍流减阻现象的机理与增大减阻率的条件进行了定量分析。

As the viscosity of the fluid,such as water and air,is in general small,the viscous force seems to be ignored while compared with other forces,such as inertia force, gravity and press force.

实际流体流动时，由于流体受粘性的影响，在流体表面附近会形成沿法线方向速度变化较快的薄层，这一层我们称之为边界层。

When the gas flux is constant, the ratio of reduced resistance is improved with the increase of the water stream velocity. However, the relationship between the gas flux and the ratio of reduced resistance is more complex. When the water stream velocity is constant, if the gas flux is small in contrast, the effectiveness of reduced resistance is not obvious. But when the gas flux increased, the jetted gas will form """"archform"""" which will augment the shape resistance. In this condition, resistance could not be reduced and could even be increased, if the gas flux continues to be increased. So that there needs setting a baffle called step, which introduces the jetted gas into the turbulence boundary layer. In this case, the shape resistance may be fairly great. Besides, the waterline of model has also some effect on the ratio of reduced resistance, which acts on the size of wave. If waterline is deep, the wave could not affect the deployment of microbubble layer, so there is almost no effect on ratio of reduced resistance. However, the wave would affect distributing of microbubble layer under the model so that the gas could leak out from the two sides of model and directly affect the ratio of reduce resistance if the waterline is very small. Whether installing the dashplate or not has also the great influence on the effectiveness the ratio of reduced resistance. From the results of experiment, conclusion is that adding dashplate will greatly improve the effectiveness of reduced resistance.

当喷气量一定时，水流速度增大，减阻率提高；喷气量与减阻率之间的关系比较复杂，速度一定时，如果喷气量较小，减阻效果就比较差，但当喷气量增大的话，喷射出的气体就会形成一个&拱度&，增加了船模的形状阻力，在这种情况下最好采取断阶喷气，把气体引入到湍流边界层中，在这种情况下，船模的形状阻力比较大；船模的吃水对减阻率也有一定的影响，主要表现在波浪大小上，如果吃水较深，波浪影响不到微气泡层的分布，对减阻率不会造成太大影响，如果吃水较浅，波浪就会影响到微气泡层在船模底部的覆盖情况，可能会有部分微气泡从船模两侧泄漏，这样就直接影响到了减阻效果；是否安装压浪板，对减阻率也有较大的影响，从试验结果可以看出，在船模尾部加设了压浪板时，减阻效果明显得到改善。

Since historical times,England ,where the early inhabitants were Celts, has been conquered three times .

从有历史以来，英国，在此地早期居住的是凯尔特人，已经被征服了三次。

Bluetooth OBEX File Transfer Enables the sending and receiving of files on your phone via Bluetooth.

蓝牙OBEX文件移动允许经过蓝牙传送和接受文件。。。。