Hydro-Geochemistry and Water Quality Index Assessment in the Dakhla Oasis, Egypt

Water quality is crucial to the environmental system and thus its chemistry is important, and can be directly related to the water’s source, the climate, and the geology of the region. This study focuses on analyzing the hydrochemistry of specific locations within the Dakhla Oasis in Egypt. A total of thirty-nine groundwater samples representing the Nubian Sandstone Aquifer (NSSA) and seven surface water samples from wastewater lakes and canals were collected for analysis. Key parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) were measured on-site, while major ions and trace elements (Fe+2 and Mn+2) were analyzed in the laboratory. The water quality index (WQI) method was imployed to assess the overall water quality. Hydro-chemical facies were investigated using Piper’s, Scholler’s, and Stiff diagrams, revealing sodium as the dominant cation and chloride, followed by bicarbonate as the dominant anion. The hydro-chemical composition indicates that Na–Cl constitutes the primary water type in this study. This points to the dissolution of evaporates and salt enrichment due to intense evaporation resulting from the region’s hyper-aridity. In groundwater samples, the order of hydro-chemical facies is HCO3 − > Cl− > SO4−2 > Na+ > Ca+2 > K+ > Mg+2, while in wastewater samples, it is Cl− > Na+ >SO4−2 > HCO3− > Ca+2 > Mg+2 > K+. When considering iron and manganese parameters, the water quality index (WQI) values suggest that most groundwater samples exhibit excellent to good quality but become poor or very poor when these elements are included. This study could prove valuable for water resource management in the Dakhla Oasis

Special Libraries, April 1933

Volume 24, Issue 3https://scholarworks.sjsu.edu/sla_sl_1933/1002/thumbnail.jp

Effect of transverse gust velocity profiles

A large variety of gusts that develop in the atmospheric boundary layer affect aerial vehicles. This study, performed in water tow tanks, compares the response of a flat plate wing to transverse vertical gusts with a top-hat and a sine-squared velocity profile at Reynolds numbers of 20,000–30,000. Experiments are performed for a wide range of gust ratios (0.5–1.5) and angles of attack (0–20 deg). Force measurements for a sine-squared gust show a smoother increase in lift and a lower peak compared with a top-hat gust for the same gust ratio. Linear models are found to work reasonably well predicting the force response for the sine-squared gust, whereas the top-hat gust exhibits significant nonlinear effects at the largest gust ratios. This nonlinear behavior is linked to high levels of circulation shed from the wing edges and the development of nonplanar wakes. Nevertheless, the gust momentum inflow on the wing is directly linked to many characteristics of the lift response, independently of gust velocity profile. In addition, the lift response for the two gusts is found to increase with angle of attack until the wing inclination is large enough to produce a separated wake before gust entry

Wing-gust interactions: The effect of transverse velocity profile – invited –

The flow field and force produced during a wing-gust encounter have been compared between a top-hat and a sine-squared transverse gusts. Experiments are performed at Reynolds number between 20 000 and 30 000 in a water tow tank. Both gusts are generated by disturbing the flow in a section of the tank at different velocities, resulting in gust ratios, GR, equal to 0.5, 0.75, 1.0, and 1.5. Time-resolved force and flow field measurements are analysed and compared with linear theories. The force results show a smoother increase in lift for the sine-squared gust accompanied by a lower maximum lift. The specific range of GRs was selected to capture the non-linear behaviour of the top-hat gust on lift. However, for the same gust ratios, the sine-squared gusts remained in the linear regime. As a result, Küssner’s theory is found to accurately predict the loads resulting from the sine-squared gust for a larger range of gust ratios than the top-hat gust. The non-linear behaviour of the top-hat gust on the lift force is linked to higher levels of circulation shed from the wing edges and the development of non-planar wakes. It is concluded that the gust shape is a critical parameter determining the wing-gust encounter characteristics