Acoustic mode beam effects of nonlinear internal gravity waves in shallow water </head> <body bgcolor="#B6CFCB">  <img src="http://acoustics.whoi.edu/sw06/images/masthead_img.jpg"> <br> <br> <font color="navy" style="font-size: 18px; font-family: Arial, Helvetica, sans-serif"> Acoustic mode beam effects of nonlinear internal gravity waves in shallow water<br>Timothy Duda, Ying-Tsong Lin, and James F. Lynch</font> <font color="navy" style="font-size: 12px; font-family: Arial, Helvetica, sans-serif"> <b> <br><br><p> Ducting of sound between short-wavelength nonlinear internal gravity waves in costal environments has been demonstrated by substantial evidence. The ducting takes a unique form for each of the acoustic normal modes. Some consequences of this are examined here using three-dimensional parabolic equation modeling and theory. For a pair of waves having a broadband 200-Hz source placed between (i.e., in the duct), strong interference patterns within the duct are developed for each mode after a few kilometers. Some of the energy escapes at high angle with respect to the duct direction. Termination of the internal wave duct, an observed feature, results in beams of energy unique to each mode to radiate outward. Specific cases having water depths of order 80 m and propagation distances of 20 to 30 km are examined. Situations where one or more modes are completely absent at selected positions are compared with similar events observed in the field. </font> <br> <br> <P><p> Back to the <a href="http://acoustics.whoi.edu/sw06/index.html"> main WHOI SW06 home</a> <p><p> <hr> <center> <table> <tr> <td rowspan="2"> <a href="http://www.whoi.edu"> <img src="http://acoustics.whoi.edu/images/whoi-logo.gif" alt="WHOI logo" align="middle" border="0" height="65" width="65"> </a> </td> <td> <i><font size="-1"> <a href="http://acoustics.whoi.edu/copyright-whoi.html"> © Woods Hole Oceanographic Institution<br> </a> <a href="http://www.washington.edu"> © University of Washington </a> </font></i> </td> <td rowspan="2"> <a href="http://www.washington.edu"> <img src="http://acoustics.whoi.edu/sw06/images/125px-University_of_Washington_Seal.png" alt="University of Washington Seal" align="middle" border="0" height="65" width="65"> </a> </td> </tr> <tr><td> <i><font size="-1"> Last updated July 2008 </font></i> </td></tr> </table> <br> <a href="http://www.onr.navy.mil"> <img src="http://acoustics.whoi.edu/images/onrsmall.gif" alt="ONR logo" border="0"> </a> </center> </body> </html>