WIND WAVES AND SWELL
WIND WAVES AND SWELL
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风浪和海浪
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
R. Wiegel
中科院分区：
文献类型：
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作者：
R. Wiegel
吹过水面的风产生波浪。一般来说，风速越高，所刮的风就越大，刮的时间越长，平均波浪也就越高越长。在产生它们的风的作用下仍然存在的波浪被称为风浪或海。它们是强迫波而不是自由波。它们在前进的方向上是可变的（Arthur, 1949）。它们在传播方向上是不规则的。由于风在水面上的剪切应力，水流是旋转的，正如对水中染料的观察所表明的那样，它是相当湍流的。当波浪离开产生区域后，它们的特征变得有些不同，主要是平滑，失去了粗糙的外观，因为在大波浪上的大量小波浪和白浪和浪花消失了。当没有风暴时，海浪被称为巨浪。图1显示了一些在实验室拍摄的波浪在风的作用下仍然上升的照片，以及同样的波浪系统在离开风洞的有风部分后的照片。可以看出，自由运行的涌浪比风段的波浪更平滑。涌浪的运动几乎是无旋转和无湍流的，除非涌浪冲进其他区域，那里的水处于湍流运动中。湍流是流体的特性，而不是波动的特性。当波浪从产生区域传播了一段距离后，由于空气阻力、内摩擦以及在遇到其他风暴区域时大规模的湍流散射，它们损失了一些能量，而由于水重力波的色散和角传播特性，剩余的能量已经扩散到更大的区域。所有这些机制都会导致能量密度的降低。这样，波浪的高度就会降低。此外，由于其色散特性，各分量波周期趋于分离，即最长的波引导波主体，最短的波形成波主体的尾部。最后，涌浪可能穿过有风的地区，在旧的涌浪上增加新的风浪，可能直接增加或减少旧的涌浪的大小。
Winds blowing over the water surface generate waves. In general the higher the wind velocity, the larger the fetch over which it blows, and the longer it blows the higher and longer will be the average waves . Waves still under the action of the winds that created them are called wind waves, or a sea. They are forced waves rather than free waves. They are variable in their direction of advance (Arthur, 1949). They are irregular in the direction of propagation. The flow is rotational due to the shear stress of the wind on the water surface and it is quite turbulent as observations of dye in the water indicates. After the waves leave the generating area their characteristics become somewhat different, principally they are smoother, losing the rough appearance due to the disappearance of the multitude of smaller waves on top of the bigger ones and the whitecaps and spray. When running free of the storm the waves are known as swell. In Fig. 1 are shown some photographs taken in the laboratory of waves still rising under the action of wind and this same wave system after it has left the windy section of the wind-wave tunnel. It can be seen thati-the freely running swell has a smoother appearance than the waves in the windy section. The motion of the swell is nearly irrotational and nonturbulent, unless the swell runs into other regions where the water is in turbulent motion. Turbulence is a property of the fluid rather than of the wave motion. After the waves have travelled a distance from the generating area they have lost some energy due to air resistance, internal friction, and by large scale turbulent scattering if they run into other storm areas, and the rest of the energy has become spread over a larger area due to the dispersive and angular spreading characteristics of water gravity waves. All of these mechanisms lead to a decrease in energy density. Thus, the waves become lower in height. In addition, due to their dispersive characteristic the component wave periods tend to segregate in such a way that the longest waves lead the main body of waves and the shortest waves form the tail of the main body of waves. Finally, the swell may travel through areas where winds are present, adding new wind waves to old swell, and perhaps directly increasing or decreasing the size of the old swell.