Surface wave

Surface waves are interface waves on the free surface of a body or on its phase boundary layer (e.g. water surface ). They are neither purely transverse nor purely longitudinal waves and can be differentiated according to the aggregate state of the media on whose surface they spread:

on a solid surface: seismic waves , surface acoustic waves
on a liquid surface: gravity waves , capillary waves
on a gaseous surface: gravity waves .

Surface waves in liquids

Gravity waves south of the Strait of Messina . One recognizes the higher speed of propagation with increasing wavelength

On the surface of liquids, gravity and surface tension can act as repulsive transverse forces, which take on the role of the shear module . This results in transverse surface waves, the propagation of which is generally difficult to describe.

The liquid particles on the surface are not transported by the wave, but remain stationary apart from a small movement along a circle-like path with a radius that corresponds to half the wave height. Each volume element of the liquid thus runs through a curve on the water surface that can be approximated by a circle around a fixed center on the median plane.

The wave speed depends on

the acceleration due to gravity

{\ displaystyle g}

the surface tension in N / m ${\ displaystyle \ sigma}$

the density

{\ displaystyle \ rho}

the ratio of liquid height to wavelength : ${\ displaystyle h}$ ${\ displaystyle \ lambda}$

{\ displaystyle v_ {ph} = {\ sqrt {\ left ({\ frac {g \ cdot \ lambda} {2 \ pi}} + {\ frac {2 \ pi \ cdot \ sigma} {\ rho \ cdot \ lambda}} \ right) \ cdot \ tanh \ left (2 \ pi \ cdot {\ frac {h} {\ lambda}} \ right)}}}

with the hyperbolic tangent function .

Since the speed depends on the wavelength, these surface waves show a dispersion .

On the part of protophysics , the term 'transversal' was rejected as a generic term in connection with surface waves.

Shapes of water waves

shape	period	root cause
Capillary waves	up to 1 s	Wind , sound , ultrasound ; small obstacle when flowing ( shooting or flowing )
ordinary gravity waves	1 to about 12 seconds	Wind; Flow obstruction, turbulence
Swell , infralateral waves	0.5 to 5 min	ordinary gravity waves, wind
Seiches , tsunami	5 minutes to several hours	Earthquake , wind and changes in air pressure
Tidal waves	12 or 24 hours	Moon , sun (each the gravitational pull)
Transgeidal waves (long period waves)	> 24 hours	Moon Sun; Storms

literature

Demtröder Experimentalphysik Volume 1 - Springer Verlag - ISBN 978-3662464144
Stöcker - Paperback of Physics - ISBN 978-3817118601

Individual evidence

↑ Bruno Thüring : Introduction to the Protophysics of the Wave . 1978, Berlin: Duncker and Humblot, p. 141.

[1] Bruno Thüring : Introduction to the Protophysics of the Wave . 1978, Berlin: Duncker and Humblot, p. 141.