Salvaging velocity measurements corrupted by nearby instruments

Sveinn Ó. Pálmarsson, S. Geoffrey Schladow,Derek A. Fong

Limnol. Oceanogr. Methods 3:263-274 (2005) | DOI: 10.4319/lom.2005.3.263

ABSTRACT: A methodology is presented for salvaging velocity measurements that have been corrupted by the interference of nearby instruments. The method iteratively filters out spikes in the data that are not coherent with the median-filtered velocity in spatial and temporal dimensions. An example is given for a data set from a benthic boundary layer, found to be corrupted by vortex shedding from nearby instruments co-located for sampling of scalars with the velocity field. The effectiveness of the method is demonstrated by the reduction in energy at high frequencies and the reasonable flow velocities produced. This procedure provides realistic estimates of shear stress and other properties of the flow. Weaknesses of the method are the subjective determination of the size of the filter window, the criterion for sample deletion, and boundary conditions.