The effect of liquid viscosity on the polygonal instabilities observed within hollow vortex core

The dynamics of liquid vortices generated by rotating a flat disc near the bottom of a cylindrical tank is investigated experimentally. Several former investigations have found that the main parameters affecting the flow behaviour are incorporated in two non-dimensional numbers: Reynold's number and the aspect ratio. Despite some evidence of the important role of fluid viscosity on the polygonal pattern instability behaviour observed within the hollow vortex core, a systematic study has not yet been carried out. This thesis examines the role of viscosity in the development, evolution, wave speed propagation and the overall transition of vortex core instabilities. The data analysis was performed using the digital image processing technique. Increasing the viscosity of the fluid by mixing glycerol with tap water at room temperature, was found to significantly decrease the polygonal patterns' limits of endurance and distort their geometry until all mode shapes were eventually destroyed and never recognized, beginning with high mode shapes progressively until the lower polygonal patterns are reached. Increasing the fluid viscosity to 22 times that of water resulted into an up to 25% augmentation of the maximum polygonal pattern speed. In all cases, the pattern speed ( f p ) was found to be almost 1/3 the disc speed (f d ), which confirms the pure water results obtained by Vatistas et al. (2008). The effect of varying the viscosity on the transitional processes between subsequent polygonal patterns is also addressed in this thesis. Alike to the case of pure water, the transition between polygonal patterns is found to occur in two stages: a quasi-periodic phase followed by frequency locking

Mixing Within Patterned Vortex Core

The video shows the flow dynamics within inner and outer regions of a vortex core. The observed phenomena mimic a transport process occurring within the Antarctic vortex. The video shows two distinct regions: a strongly mixed core and broad ring of weakly mixed region extending out the vortex core boundaries. The two regions are separated by a thin layer that isolates the weakly and strongly mixed regions; this thin layer behaves as barrier to the mixing of the two regions. The video shows that the barriers deplete when a swirl of the vortex core increases and the vortex core espouses a triangular pattern.Comment: 62nd Annual Meeting of the APS Division of Fluid Dynamics, Fluid Dynamics Vide

Facile synthesis of copper nitroprusside chitosan nanocomposite and its catalytic reduction of environmentally hazardous azodyes

Abstract One of the biggest issues affecting the entire world currently is water contamination caused by textile industries’ incapacity to properly dispose their wastewater. The presence of toxic textile dyes in the aquatic environment has attracted significant research interest due to their high environmental stability and their negative effects on human health and ecosystems. Therefore, it is crucial to convert the hazardous dyes such as methyl orange (MO) azo dye into environmentally safe products. In this context, we describe the use of Copper Nitroprusside Chitosan (Cu/SNP/Cts) nanocomposite as a nanocatalyst for the chemical reduction of azodyes by sodium borohydride (NaBH4). The Cu/SNP/Cts was readily obtained by chemical coprecipitation in a stoichiometric manner. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy were applied to investigate chemical, phase, composition, and molecular interactions. Additionally, Scanning electron microscope (SEM) was used to examine the nanomaterial's microstructure. UV–vis spectroscopy was utilized for studying the Cu Nitroprusside Chitosan's catalytic activity for the reduction of azodye. The Cu/SNP/Cts nanocomposite demonstrated outstanding performance with total reduction time 160 s and pseudo-first order constant of 0.0188 s−1. Additionally, the stability and reusability study demonstrated exceptional reusability up to 5 cycles with minimal activity loss. The developed Cu/SNP/Cts nanocomposite act as efficient nanocatalysts for the reduction of harmful Methyl orange azodye