Particle Concentration In Liquid Research Articles

Fountains as potential sources of aerogenic risk for urban populations

Introduction. Fountains (office and outdoor), being small decorative structures used to improve the parameters of the human life environment, in the process of their work during the generation of a water jet, determine the creation of spray and aerosol fractions, thereby allowing the loss of a certain volume of liquid when air moves and wind carryover. The biological safety of the operation of such hydraulic structures depends on the composition of the microflora of the water in the main reservoir of the fountain, especially in the warm season. Materials and methods. For the period 2010-2020, the study of the composition of the microflora of water in the main reservoirs of the existing fountains and in the sedimented spray-aerosol mixture formed during the operation of these hydraulic structures was carried out. Results. At water temperatures above +18 °C and the absence of a disinfection system or its regular complete replacement, fountains were found to have a significant level of contamination with bacterial and fungal pathogens, including mycobacterium tuberculosis; the number of microorganisms of the E. coli group in office and open city fountains. The amount of Clostridial flora and streptococci in open fountains significantly exceeds the standard indicators (p <0.05). Limitations. When studying the trends in concentration of liquid particles in the air, the methodology of K.Y. Kondratiev et al. (1988) and V.M. Khvata et al. (1991) was used. The studies were carried out in accordance with the Interstate standard “Water. Methods of sanitary and bacteriological analysis for field conditions” GOST 24849-2014, 2016. Conclusion. The microflora of the operating fountain, in the absence of disinfection of water or its regular replacement, is characterized by a high titer of bacteria of the E. coli group, streptococci, staphylococci, mycobacterium tuberculosis, mold and yeast fungi. The one of the conditions for the excessive growth of these microorganisms in this hydraulic system is the water temperature above 18 °C. In the sedimented aerosol near the active fountain, a bacterial and fungal spectrum of pathogenic microorganisms similar to the water is found. Fountains (external and office) can be considered as sources of aerogenic household infection of the population of modern cities, which requires strict adherence to sanitary norms and rules that ensure the biological safety of these hydraulic structures.

Estimation of Acoustic Energy and Performance Characterization of Acoustic Concentrator

Among many methods of particle concentration in liquid, acoustic concentrator uses ultrasonic standing wave to concentrate microparticles in liquid. In order to determine its performance on particle concentration, estimation of acoustic energy density inside the concentrator is important since energy density is the main contributing factor in calculating the primary acoustic radiation force acting on the particles. The balance between the primary radiation force and hydrodynamic force acting on the particles inside the acoustic concentrator determine the performance of the acoustic concentrator. Therefore, this study focuses on the measurement of acoustic energy density inside the h-shaped acoustic concentrator and characterization of performance of the concentrator. First, energy density is estimated by curve-fitting the experimental particle position in the ultrasonic field with one-dimensional theoretical position. Second, two-dimensional acoustic and hydrodynamic fields are determined using two-dimensional simulation model in COMSOL Multiphysics. Integrating the governing equation for particle motion in the balance of acoustic and hydrodynamic forces result in the particle trajectory and it is compared with the experimental observation. The results would provide deeper insight into the operation of acoustic concentrator and the detailed phenomenon of particle motions inside the concentrator.

1043 ON SYNTHETIC JET ACTUATOR USING BUBBLE PRODUCED BY ELECTRIC DISCHARGE

Over the last decade, synthetic jets adequate for micro machinery have received attention as substitutes for continuous jets. The development of synthetic jet actuators with, for example, a diaphragm, a piston, or a speaker cone, instead of mechanical drivers, is required for the downsizing of flow control systems in fluid machines. In this study, an experimental prototype of a synthetic jet actuator using the nonlinear oscillation of bubbles produced by iterative electric discharge is proposed. Numerical simulations clarify the fundamental flow characteristics of the synthetic jets produced by ideal bubble oscillation. The discharge conditions include the influence of the metal particle concentration in liquid on bubble generation. The onset condition based on the non-dimensional stroke of the synthetic jet and the relation between the bubble motion and the change of the jet velocity with time are discussed. Especially, the influence of T* (the ratio of driving time of a bubble to the down time) on the unsteady flow pattern and the time-averaged jet structure is investigated. In addition, the flow characteristics of a synthetic jet with down time are compared with that of a normal synthetic jet with equivalent velocity.