In this study, on the basis of observation data of water temperature and salinity at the center of Uranouchi
Bay for about one-year, stratification strength and vertical mixing during the stratification period were evaluated
in terms of energy amount. Then their energy amounts were examined comparatively with the tidal energy
amount of the bay. These results are described as follows :
1) Stratification strength reaches the maximum of 180 Jm-3 in August. This is equivalent to the energy
amount that the tide works on the bay for about two hours.
2) The vertical mixing energy is as much as l/260-1/2600 of the mean tidal power of the bay.
3) The energy amount that increases stratification strength is l/250 of the mean tidal power of the bay.
On the basis of observation data of water temperature and salinity at the center of Uranouchi Bay throughout
nearly one year, it is shown that the Brunt-Vaisala frequency N is not zero or a constant, but the N has an exponential
distribution. In this case, intemal waves are described with Bessel's function. On the basis of this result,
the flow characteristics of intemal tidal waves are described.
The experiments were conducted using a circulating water chamel in order to clarify the characteristic movement
of the trolling depressor. A three component load cell measured the tension of the line from the trolling
depressor. The length of the line and the flow speed were changed between 0.5m and 1.4m, and 0.4m/s and 1.6
m/s, respectively. The movement of the trolling depressor was recorded through CCD cameras onto videotapes.
The three component displacement of the point where the line was knotted to the trolling depressor was
estimated by the tension of the line. The periods of the x and z component's displacement were similar and about
0.4 seconds. The period of the y component's displacement was about 0.8 seconds and twice as long as that of
the x and z component's. It was clear that the locus of the point where the trolling depressor was knotted was
similar to the number '8' on thexy, yz and xz planes.