Values Of Flow Speed Research Articles

Sortable silt variations on the continental slope of Campos Basin (SW Atlantic): Implications of oceanographic processes

An indirect way to measure the speed of bottom currents granulometric parameters such as the proxy sortable silt (SS‾). This proxy is associated with the sedimentation process and can estimate paleocurrents. This study aims to evaluate the range of the near-bottom current flow speed through the SS‾ and related to oceanographic processes in the southeastern Brazilian continental slope. The SS‾ values ranged from 17.08 to 26.23 μm, presenting a mean value of 19.87 μm. The flow speed values were obtained using Ledbetter's (1986) and Miller and Komar (1977) formulas, varying from a minimum of 0.07 and 0.21 m s−1 to a maximum of 0.24 and 0.26 m s−1. The changes in bottom velocities observed in the Campos Basin are influenced by off-shelf export of the sediment, hydrodynamic parameters (Brazil Current, Intermediate Western Boundary Current, and the Deep Western Boundary Current), and the geomorphological characteristics (island, ravine, and halokinesis movement).

Mathematical modelling of aerosol sampling with thin-walled probes at yaw orientation with respect to the wind

A study is made of the sampling characteristics of a thin-walled sampler at orientations with respect to the flow direction ranging from 0° to 90°. A mathematical method is adopted to model the situation, and various values of flow speed and suction rate are considered. For orientations greater than 0° the sampler can be regarded as blunt, as the sampler walls cause the flow to become distorted, causing the flow behaviour in the vicinity of the sampling inlet to be more complicated than for the case in which the orientation is 0°. The method adoped here gives an accurate description of the flow field near the sampler, allowing an investigation to be made of the behaviour of the flow under different conditions. The paths of the particles in the flow are traced and the limiting particle trajectories, separating the sampled and unsampled particles, determined. For orientations of 0° these limiting trajectories are known to enclose a circular region in the undisturbed flow, this is shown not to be the case for orientations greater that 0°. The shape enclosed by the limiting streamlines is investigated for various situations and is found to approximate well to an ellipse. Values of the aspiration efficiency of the sampler are also determined to compare them with experimental data.