鸟语还是很捉急啊
Internal flowFirst,considering a fully developed flow in pipe,we judge whether the flow is laminar or turbulent.if the Reynolds number is less then 2300,there is laminar flow.over 4000,there is turbulent flow.between them ,the flow state depend on the practical condition.(Re equal that average flow velocity multiply characteristic length of the geometry and divide by kinematic viscosity of the fluid.)Relying on no-slip condition and newton friction law,we can obtain that the laminar velocity profile is parabolic.so we can use boundary condition to get the maximum velocity double the average velocity.then we can derive the pressure loss and head loss.the drop loss is determined by the terms of the Reynolds number、fluid dynamic pressure ,pipe length and diameter.Turbulent flow contains some eddies.it have not orderly velocity profile.but we can obtain a time-average velocity profile in the axial direction from experimental date.we generally use the one-seven power-law velocity profile to approximates many practice flow. Different from laminar flow,the drop loss also depend on the relative roughness of the pipe. In practice,we usually use empirical formula or Moody chart to determine the friction factor and then to calculate the drop loss ,head loss or to solve other types of fluid flow problem.When Fluid flow past fittings like valve、inlet,outlet,this fittings will cause additional loss,are called minor loss.in practice,we use this fittings can get its loss coefficient from relevant standards or product specifictions.If fittings are too close,it may be loss accuracy. In this case,we must rely on experience or experiment to have a acceptability result .easy！
内部流动
首先，考虑管道中充分发展的流动，判断是层流还是湍流，雷诺数小于2300为层流，超过4000为湍流，两者之间的流动状态取决于实际条件。（等于平均流速乘以几何特征长度并除以流体的运动粘度。）依靠无滑移条件和牛顿摩擦定律，我们可以得到层流速度剖面是抛物线的，所以我们可以使用边界条件得到最大速度为平均速度的两倍，然后我们可以推导出压力损失和水头损失。水滴损失由雷诺数、流体动压、管道长度和直径等项决定。
湍流中含有一些涡流，其速度分布不规则，但从实验数据我们可以得到轴向的时均速度分布。我们一般使用一七次幂律速度分布来近似许多实际流动。与层流不同，水滴损失还取决于管道的相对粗糙度。在实践中，我们通常使用经验公式或穆迪图来确定摩擦系数，然后计算水滴损失、水头损失或解决其他类型的流体流动问题。
当流体流过阀门、入口、出口等管件时，该管件会造成额外的损失，称为小损失。在实际使用中，我们使用该管件可从相关标准或产品规范中得到其损失系数。如果配件太近，可能会损失精度。在这种情况下，我们必须依靠经验或实验才能得出可接受的结果。
首先，是学过流体力学的初步概念，看见一些数字，名词，脑袋里面马上有‘草图’，
横向相关词汇，靠混世道，比如‘啦米内’，层叠，热压机也是这个，总之，一个是基本概念，一个是词汇，没有概念硬读，很苦，鸟语词汇忒少，也苦，
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