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E. Mollo-Christensen

Abstract

An obstacle in a boundary-layer flow creates a disturbance upwind of the obstacle, consisting of a stationary vortex extending downstream on both sides of the obstacle. This flow disturbance may interfere with observation of wind profiles or fluxes. The distance of the vortex from the obstacle is of the order of the obstacle width or height, whichever is the smaller, and for obstacles which do not possess an obvious length scale, the separation distance is of the order of the boundary-layer displacement thickness. Observation from ship-mounted booms or from oil platforms should be designed so as to avoid the upstream disturbance in the boundary layer. Illustrations and examples given are taken from wind tunnel tests of R/V Flip.

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Graig E. Dorman
and
Erik Mollo-Christensen

Abstract

We report on observations of near-surface Velocity, temperature, stress, buoyancy, and surface wave fluctuations, including successive short-time averages of coherences, phases, autospectra, and probability densities of the variables. There appear to be short-duration events where the momentum exchange exceeds the average by 102. These events are characterized by the high energy content in capillary waves, and velocity and temperature fluctuations; they are separated by relatively quiesent periods. Energy transfer between components is discernible as is a tendency to logarithmico-normal distribution in the occurrence of measures of fluctuations.

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E. Mollo-Christensen
,
N. E. Huang
,
L. F. Bliven
, and
S. R. Long

Abstract

A wave sensor, consisting of parallel, evenly spaced capacitance wires, whose output is the sum of the water surface deflections at the wires, has been built and tested in a wave tank. The probe output simulates Bragg scattering of electromagnetic waves from a water surface with waves; it can be used to simulate electromagnetic probing of the sea surface by radar. Our study establishes that the wave probe, called the “Harp” for short, will simulate Bragg scattering, and that it can also be used to study nonlinear wave processes.

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