Study of waves & velocity over different substrate

Eduardo Infantes Oanes used three Nortek Vector Velocimeters while conducting research with IMEDEA (CSIC-UIB) in Mallorca, Balearic Islands, Spain.

The invasive algae Caulerpa taxifolia and Caulerpa racemosa have shown the great influence that the substratum type has on the abundance of these species. An experiment was designed to evaluate growth and persistence of these algae on diferent substrata. Three Nortek Vectors were used to measure simultaneous vertical profiles on three substrata (rock, sand and dead rhizome of Posidonia oceanica) to characterize flow reduction at the boundary layer and the friction coeficient. The Vectors were mounted in a downlooking position on a stainless steel bottom fixed structures.

Wave height was also obtained using the Vector pressure sensor. Mean wave conditions were propagated to the shore using a physical model and near-bottom orbital velocities calculated. These results were compared with wave height and bottom velocties measured with the Vectors.  Bottom velocity measurements on dead rhizome were lower (1.5 ± 0.2 cm s^-1) than on sand (2.2 ± 0.2 cm s^-1). The friction coefficient of dead rhizome was higher (1.04 E-01) than sand (2.33 E-02). These results could contribute to understanding the process of invasion by predicting which substrata would be more susceptible to be invaded.