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We take our clear square 16” x 16” tank and position it on the center of the turntable. Then we place our tall narrow rectangular tank (which we will use here as a water tower to provide fluid to the experiment proper via a siphon) inside the large square tank and push it flush against the side. Then, to represent the effect of the earth’s sphericity on Taylor Columns, we create a sloping bottom by dropping in a rectangular plastic sheet cut to fit inside the large tank whilst abutting up to the tower at an angle. The whole arrangement can be seen in Fig.1.
We now (i) pour water into the tower until about 80% full and (ii) fill the large square tank until water completely covers the slanted bottom to a depth (at the shallowest point) of about 2 inches. To transfer water from the storage container to the water in the tank of variable depth, we use a siphon arrangement through a diffuser (porous pot), as can be seen in Fig. 2 and 3.
Fig. 1: Experimental setup with water before dye is added to the holding tank
The thin (1/4”) tube from the diffuser is threaded through holes in a clamp – see Fig.2 – and through a control valve, which is used to set the rate of flow of water.
To charge the siphon system we submerge the porous pot along with its tubing in the water of the tower. When the hose etc is completely filled with water, tighten the valve to block any flow of water. Ensuring that the open end of the tube remains submerged, take the diffuser out of the tower, attach the arrangement to the tower with the clamp and let the diffuser hang down in to the water at the shallow end of the tank, as can be seen in Fig.3. The porous diffuser should be almost completely submerged in the water of the large tank and the tubing should be completely full of water (no air bubbles). If it is not, try flushing by opening the valve until all bubbles are expelled. If this does not work, repeat the charge procedure again.
Finally, add dye to the water in the tower and stir until it is evenly tinted.
Fig. 2: Clear tubing threaded through the clamp. A small control valve is used to regulate the flow.
Now we set the turntable rotating at a speed of order 10rpm. Before beginning the experiment proper, we check to see if the fluid is in solid body rotation by verifying that paper dots dropped onto the surface of the water remain stationary when viewed in the rotating frame. At this point, the system should look like Fig.3.
Fig. 3: Beginning of the experiment with the dye slowly seeping out of the diffuser
Now that the system is in solid body rotation, we can begin the experiment. We carefully open the valve (one or two turns is usually sufficient) allowing the dyed water to begin flowing through the diffuser into the container. Typical flow rates are about two ml a second.
Fig.4 shows the dye entering the container at the beginning of the experiment along the poleward wall of the container, at the shallow end of the tank.
Fig. 4: Dye entering the tank through the diffuser in the top right hand side of the container forming a ÔnorthernÕ boundary current.