FLOODING & SINKING • The intake of the water during the flooding phase is powered by the pressure exerted by the weight of all the water directly above the valve. Therefore, as the tower sinks deeper, this pressure will increase, due simply to there being an increasing weight of water above it. The rate of fill will therefore increase as well.
• The inlet valves will have to be placed below the surface of the water, so as to make the best possible use of this pressure. They must, however, not be too deep, as that would make it difficult to operate them whilst out at sea.
• Moreover, as the pressure forces acting on the inlet valve do increase, both the speed of the water and its Dynamic Pressure (pressure exerted by the water in its direction of travel) will do the same. The flow of water will therefore exert substantial frictional forces on the concrete material surrounding the edge of the valve as it passes through, making it susceptible to wear. As such, the need to line the inside of the valves with a hard, wear-resistant material, such as Tungsten-Carbide becomes apparent, in order to mitigate this.
• However, whilst all this is going on, the Static Pressure of the water (the pressure exerted outwards against the insides of the valve) will in fact decrease. This is because, in moving faster through the valve, each individual water molecule effectively spends less time in contact with its inside faces, and so less pressure overall is exerted in this direction. Intrinsically, this has the effect of leading to the implosion of any bubbles that may exist in the water, in turn leading to a process called Cavitation, whereby material is gradually ripped away from the sides of the valve. Again, lining is therefore necessary so as to prevent this.
Engineering Education Scheme: The Report | Flooding & Sinking
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