java_waves/seiche.html at main · meouda/java_waves · GitHub

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<!-- Mirrored from homepages.cae.wisc.edu/~chinwu/Coastal_Java/seiche.html by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 14 Oct 2020 15:22:11 GMT -->
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   <TITLE> CACR Seiche Calculator</TITLE>
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<img src="cacr.mini.gif" ALIGN="LEFT">
 <P><FONT COLOR="#0000FF"><center><FONT SIZE=+4>University of Delaware</font>
<font size=+3> Seiche Calculator</center></FONT></P>


<p><HR WIDTH="100%"></P></CENTER>

<CENTER><P><APPLET code= Seiche-2.html archive="seiche.jar" width=600 height=250> This application requires a Java-enhanced browser to use.  Sorry.</APPLET></P></CENTER>

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<font color="#000000">
Seiching is the formation of standing waves in water body, due to wave formation and subsequent reflections from the ends. These waves may be incited by earthquake motions (similar to the motions caused by shaking a glass of water), impulsive winds over the surface, or due to wave motions entering the basin.  The various modes of seiching correspond to the natural frequency reponse of the water body.

<p> In this example, a rectangular basin (of infinite width) with given length and depth is seiching in accordance with the mode that you specified (greater than zero).  The period of seiching (T) is determined by finding the correct length wave that will fit in the basin  for the given  water depth  (based on linear water wave theory).  The percent refers to the difference between the seiching period predicted by the dispersion relationship versus that usually used: shallow water theory.
<p>
As an example, try a basin of length 100 m, a depth of 20 m, and a mode number of two.  Note that the water surface motion is out of phase with the velocities (shown with white lines). Also notice that the water motions do not have the elliptical orbits as progressive waves do (as in the Linear Kinematics applet).  Under a node (no displacement of the water surface), the velocity is always horizontal, while under an antinode (max. displacement), the velocity  is vertical.

<p>
In the figure, you will notice that the number of modes corresponds to the number of nodal points (points of no motion of the water surface).
<p>
There are an infinite number of seiching modes possible, from the lowest (mode 1) to infinity.  The period of oscillation decreases with mode number. Realistically, the lower modes probably occur in nature, as frictional damping affects the higher modes preferentially (higher frequency).


 <p> The seiching calculations for linear  theory are given in Chapter 4 and 5 of Dean and Dalrymple, <b>Water Wave Mechanics for Engineers and Scientists,</b> World Scientific Press.)
<P><FONT COLOR="#FF0000">Comments: <a href="mailto: rad@udel.edu"> Robert Dalrymple</a></FONT></P>
<br>Center for Applied Coastal Research<br>
University of Delaware, Newark DE 19716<br>USA
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