25
个编辑
更改
跳到导航
跳到搜索
第45行：
第45行： − + − + − + − − * 飞机飞行时经视宁历过'''<font color="#ff8000"> 晴空湍流Clear-air turbulence</font>'''，以及'''<font color="#ff8000"> 天文视宁度astronomical seeing</font>'''不佳（通过大气看到的图像模糊）。
→Examples of turbulence
* Smoke rising from a [[cigarette]]. For the first few centimeters, the smoke is [[Laminar flow|laminar]]. The smoke [[Plume (fluid dynamics)|plume]] becomes turbulent as its [[Reynolds number]] increases with increases in flow velocity and characteristic lengthscale.
* Smoke rising from a [[cigarette]]. For the first few centimeters, the smoke is [[Laminar flow|laminar]]. The smoke [[Plume (fluid dynamics)|plume]] becomes turbulent as its [[Reynolds number]] increases with increases in flow velocity and characteristic lengthscale.
* 烟雾从一支香烟上升起。最初的几厘米，烟雾是层流。'''<font color="#ff8000"> 雷诺数Reynolds number </font>'''随着流速和特征长度增加，烟雾羽流（[[Plume (fluid dynamics)|plume]]）变成了湍流。
* 烟雾从一支香烟上升起。最初的几厘米，烟雾是层流。'''<font color="#ff8000"> 雷诺数（Reynolds number ）</font>'''随着流速和特征长度增加，烟雾羽流（[[Plume (fluid dynamics)|plume]]）变成了湍流。
* Flow over a [[golf ball]]. (This can be best understood by considering the golf ball to be stationary, with air flowing over it.) If the golf ball were smooth, the [[boundary layer]] flow over the front of the sphere would be laminar at typical conditions. However, the boundary layer would separate early, as the pressure gradient switched from favorable (pressure decreasing in the flow direction) to unfavorable (pressure increasing in the flow direction), creating a large region of low pressure behind the ball that creates high [[form drag]]. To prevent this, the surface is dimpled to perturb the boundary layer and promote turbulence. This results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag.
* Flow over a [[golf ball]]. (This can be best understood by considering the golf ball to be stationary, with air flowing over it.) If the golf ball were smooth, the [[boundary layer]] flow over the front of the sphere would be laminar at typical conditions. However, the boundary layer would separate early, as the pressure gradient switched from favorable (pressure decreasing in the flow direction) to unfavorable (pressure increasing in the flow direction), creating a large region of low pressure behind the ball that creates high [[form drag]]. To prevent this, the surface is dimpled to perturb the boundary layer and promote turbulence. This results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag.
* 流体流过高尔夫球。 （假设高尔夫球静止，而空气在上面流动，最容易的理解。）如果高尔夫球是光滑的，则在典型条件下，球体前部的'''<font color="#ff8000"> 边界层（boundary layer）</font>'''会出现层流。 但是，因为压力梯度会从顺压（压力沿流动方向减小）切换到逆压（压力沿流动方向增大），边界层会提前分离，从而在球后形成一个大低压区，产生较高的型阻（[[form drag]]）。 为了避免这种情况，可以在球的表面制造凹槽以扰动边界层并促进湍流。 这会产生较高的表面摩擦，但会进一步移动边界层分离点，从而导致阻力减少。
* 流体流过高尔夫球。 （假设高尔夫球静止，而空气在上面流动，最容易的理解。）如果高尔夫球是光滑的，则在典型条件下，球体前部的'''<font color="#ff8000"> 边界层（ [[boundary layer]] ）</font>'''会出现层流。 但是，因为压力梯度会从顺压（压力沿流动方向减小）切换到逆压（压力沿流动方向增大），边界层会提前分离，从而在球后形成一个大低压区，产生较高的型阻（[[form drag]]）。 为了避免这种情况，可以在球的表面制造凹槽以扰动边界层并促进湍流。 这会产生较高的表面摩擦，但会进一步移动边界层分离点，从而导致阻力减少。
*[[Clear-air turbulence]] experienced during airplane flight, as well as poor [[astronomical seeing]] (the blurring of images seen through the atmosphere).
*[[Clear-air turbulence]] experienced during airplane flight, as well as poor [[astronomical seeing]] (the blurring of images seen through the atmosphere).
*[[Clear-air turbulence]] experienced during airplane flight, as well as poor [[astronomical seeing]] (the blurring of images seen through the atmosphere).
* 飞机飞行时经历过'''<font color="#ff8000"> 晴空湍流（Clear-air turbulence）</font>'''，以及'''<font color="#ff8000"> 天文视宁度（astronomical seeing）</font>'''不佳（通过大气看到的图像模糊）。
* Most of the terrestrial [[atmospheric circulation]].
* Most of the terrestrial [[atmospheric circulation]].