Hydrodynamic Studies Of Tide Gauges

When tide gauges of the float and well type are situated such that there is a flow past them, an error is introduced into their readings as a result of the flow. The hydrodynamics of the flow are considered and a relationship is developed for the well orifice pressure coefficient Cp , in terms of a Reynolds number, Froude number and two geometric ratios. The relationship is investigated by model test on various tidewell end-shapes and orifice configuration. The Cp value and hence expected changes in level in the well are compared. The types giving least error from this effect are found to be the shrouded cone and the standard American gauge. Concern is shown regarding the magnitude of this error and several alternatives for eliminating it are suggested.