فهرست مطالب vallejo

The effect of a hydrophobic coating on the flow through circular pipes with Newtonian fluids has been investigated. Velocity fields inside a pipe were experimentally determined by the particle image velocimetry (PIV) technique. The test fluid presented a viscosity of about sixty times higher than water viscosity. Two glass pipe configurations were used: one uncoated and another covered with an extremely hydrophobic commercial product. Comparisons between coated and uncoated pipes were made at similar Reynolds (Re) numbers, all in the laminar regime (70-250). Results show that the hydrophobic effect consists in an observable slip velocity at the wall, with a reduction in shear rate near the pipe boundary. Pressure drop values were estimated from a modified Hagen-Poiseuille equation, taking into consideration the non-zero velocity at the boundary for both set of experiments, and the results show a 20% reduction in the pressure drop for the hydrophobic wall compared with the uncoated pipe case.

The anatomical and epidermal characteristics, as well as the physiological response, of 'Colombia' ecotype cape gooseberry plants treated or untreated with foliar applications of kaolin at 2 irrigation levels (well-irrigated plants vs. water-stressed plants) were evaluated. Relative Water Content (RWC), stomatal density, and chlorophyll index were reduced under water stress. Water stress increased leaf temperature and trichome density. In water-stressed plants, the foliar application of kaolin decreased transpiration rates, leaf temperature, trichome density, and leaf thickness. Kaolin also improved the plant height, total plant dry mass, water-use efficiency, and increased stomatal density in water-stressed plants. The results suggest that kaolin may be a useful tool to mitigate the negative effects of water stress and may improve the efficient use of water in cape gooseberry plants with especial water conditions.