Dual-plane stereoscopic PIV measurement of vortical structure in turbulent channel flow on sinusoidal riblet surface

Vortical structure in wall turbulence over a sinusoidal riblet surface is investigated by means of a dual-plane stereoscopic particle image velocimetry (DPS-PIV) measurement. The experiment is made in a channel flow at a friction Reynolds number of 150. The lateral spacing of the adjacent walls of the sinusoidal riblet varies in the streamwise direction and 12% of the drag reduction rate has been confirmed. The DPS-PIV measurement system consists of four high-speed CCD cameras. The laser sheets are provided on streamwise and wall-normal planes and separated 0.5 mm in the spanwise direction to each other. The profiles of the velocity statistics in the flat case show a good agreement with previous data. Since all velocity components can be measured on adjacent laser sheets simultaneously, an instantaneous velocity deformation tensor can be obtained and vortical structures can be identified by a second invariant of the tensor i.e., the Q value. The probability of Q value in the riblet side is almost unchanged from that of the flat side. The analysis of the tracking of vortical structures by using the Q value is performed. As similar to a pathline analysis in a previous study, we confirmed that the riblet surface prevents the vortical structure hitting the wall and vortical structures follow the upward and downward flows induced by the sinusoidal riblet surface

Biomonitoring the genotoxic potential of the air on Tradescantia pallida var. purpurea under climatic conditions in the Sinos River basin, Rio Grande do Sul, Brazil

Abstract The present study evaluated the genotoxic effects of the atmospheric air on Tradescantia pallida var. purpurea in urban areas with different intensities of vehicular traffic and in riparian forest fragments in the Sinos River Basin (Rio Grande do Sul, Brazil), considering the influence of climatic conditions prevailing in these environments. Bimonthly, from May 2012 to March 2013, cuttings with flower buds were exposed for 8 h in urban and riparian forest environments in the municipalities of Caraá, Taquara and Campo Bom in the upper, middle and lower sections, respectively, of the Sinos River Basin. Simultaneously, negative controls were made and climatic data were recorded. Micronuclei (MCN) frequencies were determined in young tetrads of pollen mother cells and expressed as MCN/100 tetrads. Significantly higher MCN frequencies were observed in buds exposed in urban and riparian forest environments in Taquara (up to 7.23 and 4.80, respectively) and Campo Bom (up to 4.90 and 4.23, respectively) than in buds exposed in Caraá (up to 2.90 and 2.50, respectively), in the majority of samplings, and in relation to the negative control (up to 1.93) in all months. Over the course of the period monitored, there were significant variations in MCN frequencies at all sampling points, with the exception of the urban environment in Caraá. For the urban environments, relation between the MCN frequency, vehicular traffic and mean temperature was observed. For the riparian forest fragments, there was no association between MCN frequency and climatic factors. Tradescantia pallida var. purpurea can be considered a useful tool to point out areas with increased atmospheric pollution, since the exposure of plants under severe climatic conditions is avoided to minimize their negative influence on the formation of micronuclei