Turbulent Diffusion of Temperature and Salinity 



When a thermal experiment was to be conducted, the top 4 cm 

 of the cell was filled with water having a temperature several degrees 

 above room temperature. A thin piece of balsa wood was floated on 

 the top of the bottom layer and warm water introduced through a small 

 nozzle directed perpendicularly to the top of the balsa wood. This 

 procedure deflects the downward nnomentum of the warm water flow 

 to the horizontal and filling was accomplished with a minimum of 

 vertical mixing with the cooler more dense water below. When a 

 salinity diffusion experiment was to be conducted, a top layer of pure 

 water was introduced the same way. In this case the bottom water 

 contained the salt solution. 



A repeatable amount of turbulence was introduced by mechani- 

 cally moving a stiff insulated wire back and forth at the interface 

 between the two layers at a controlled rate and for a controlled 

 length of time. The wire is shown in Fig, 1 at the 4 cm level where 

 the interface was located when the cell was filled. (The cell is 

 empty in Fig. 1.) The top of the "L" shaped wire is coupled to a 

 mechanical system outside the picture. It is the bottom part of the 

 "L" that was rotated back and forth laterally at the interface pro- 

 ducing turbulence when desired. Table I gives the specifications 

 for generating the amounts of turbulence that were used. 



Table I. Specifications of the Turbulence Generator 



Turbulence No. Mixer Dimensions ^^, t^ ^ ^^^ 

 Swing Per Sec 



- 



1 1.8 mna diam, 7 cm long 10,8° 2,5 



2 " " 5.4 



When a thermal experiment was being conducted, the center 

 sensor was used. It consists of a two element copper- cons teintan 

 thernnopile with junctions 2 cm apart. The upper junction was 

 placed 1 cm above and the other 1 cm below the interface of the 

 upper warm and the lower cooler water. The output of this sensor 

 was 30 microvolts for each degree difference in temperature. It 

 was connected to a small commercial micro-voltmeter and recorder 

 which gave a time record of the temperature difference, 1 cm above 

 and 1 cm below the interface. The record of vertical temperature 

 difference decay, with time, gives data related to the effect of mole- 

 cular diffusion when no turbulence Js introduced. The vertical tem- 

 perature difference decay, with controlled amounts of turbulence, 

 was recorded by using a succession of carefully timed turbulent 

 pulses interspaced with short intervals of quiescence. 



When a salinity diffusion experiment was being conducted the 

 two sensors on the right in Fig. 1 were used. They are identical 



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