522 



Currents in a Strait 

 Table 140. Slope of the boundary layer {given in m/30 km) 



The magnitude of these values is similar to those actually found in the Bosphorus 

 which average about 34 m. In the case of a south-west wind the slope is steeper than 

 for a north-east wind, which agrees with the theoretical result. Figure 240 shows the 



20 



V, cm/sec 

 40 60 



80 



100 



20 



E 



£40 



Q. 



a> 

 O 



60 



V, cm/sec 

 20 40 60 80 100 



20 



E 

 i 40 



60 



Fig. 240. Vertical current distribution in the upper and lower current for a certain wind 



direction at the sea surface of the sea strait (in the lower current: , in the case of 



clinging to (Haften); , in the case of gliding (Gleiten); , for a medium 



friction of the water at the sea bottom). 



current profile in the upper and lower current (omitting signs). These values are also 

 in agreement in all cases with those observed in the Bosphorus and the wind effect 

 was also of a similar kind. 



The theory is based on two water bodies that are homogeneous over a cross- 

 section at right angles to the strait. In nature they will be stratified and the cross-sectional 

 area can vary considerably along the length of the strait. Furthermore, mixing at the 

 internal boundary surface will tend to spread the discontinuity surface into a density 

 transition layer. The current boundary surface will then no longer coincide with the 

 lower limit of the upper water since there is no longer any sharp boundary. Then 

 conditions become so complex that they can no longer be handled mathematically. 



