scholarly journals Effect of H2O2 Antiseptic on Dispersal of Cavitation-Induced Microdroplets

2021 ◽  
pp. 002203452110275
Author(s):  
T. Roy ◽  
G. Damoulakis ◽  
J. Komperda ◽  
F. Mashayek ◽  
L.F. Cooper ◽  
...  
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Fluid Dynamic ◽  
Pathogen Transmission ◽  
Working Fluid ◽  
Feed Stream ◽  
High Speed Imaging ◽  
Aqueous Hydrogen Peroxide ◽  
Free Standing ◽  
Dental Procedures

The persisting outbreak of SARS-CoV-2 has posed an enormous threat to global health. The sustained human-to-human transmission of SARS-CoV-2 via respiratory droplets makes the medical procedures around the perioral area vulnerable to the spread of the disease. Such procedures include the ultrasonic dental cleaning method, which occurs within the oral cavity and involves cavitation-induced sprays, thus increasing the risk of pathogen transmission via advection. To understand the associated health and safety risks for patients and clinicians, it is critical to understand the flow pattern of the spray cloud around the operating region, the size and velocity distribution of the emitted droplets, and the extent of fluid dispersion until ultimate deposit on surfaces or escape through air vents. In this work, the droplet size and velocity distributions of the spray emerging from the tip of a free-standing common ultrasonic dental cleaning device were characterized via high-speed imaging. Deionized water and 1.5% and 3% aqueous hydrogen peroxide (H2O2) solutions were used as working fluids, with the H2O2—an established oxidizing agent—intended to curb the survival of virus released in aerosols generated from dental procedures. The measurements reveal that the presence of H2O2 in the working fluid increases the mean droplet size and ejection velocity. Detailed computational fluid dynamic simulations with multiphase flow models reveal benefits of adding small amounts of H2O2 in the feed stream of the ultrasonic cleaner; this practice causes larger droplets with shorter residence times inside the clinic before settling down or escaping through air vents. The results suggest optimal benefits (in terms of fluid spread) of adding 1.5% H2O2 in the feed stream during dental procedures involving ultrasonic tools. The present findings are not specific to the COVID-19 pandemic but should also apply to future outbreaks caused by airborne droplet transmission.

Characterization of Superheated Liquid Jet Atomisation With Phase Doppler Anemometer (PDA) and High-Speed Imaging

2006 ◽  
Author(s):  
Dilek Yildiz ◽  
Patrick Rambaud ◽  
Jeroen van Beeck ◽  
Jean-Marie Buchlin
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Initial Conditions ◽  
Particle Diameter ◽  
Superheated Liquid ◽  
High Speed Imaging ◽  
Two Phase ◽  
Phase Doppler Anemometer ◽  
Geometrical Effects ◽  
Initial Storage

A flashing phenomenon is often met in liquid propulsion of safety fields in industrial environments. This violent evaporation occurs when a liquid finds itself suddenly in a thermodynamic non-equilibrium and becomes superheated. To investigate theoretically the source processes and validate models for design and safety assessments, knowledge of accurate and reliable data such as distribution of droplet size, velocity and temperature in the closest field of flashing occurrence is mandatory. In this present work, an experimental study is undertaken in order to characterize the two-phase jet after a sudden accidental release and aims to quantify the effects of initial conditions such as initial storage pressure, temperature, geometrical effects of the release points etc on the spray characteristics. To fulfil this goal, a laser-based optical technique like Phase Doppler Anemometry (PDA) is used to obtain information for particle diameter and velocity evolution in this harsh environment. Cases for different initial pressures, temperatures and orifice diameters are studied and the droplet size and velocity evolution are presented in function of initial parameters.

scholarly journals Numerical Study of Turbulent Air and Water Flows in a Nozzle Based on the Coanda Effect

2019 ◽  
Vol 7 (2) ◽  
pp. 21
Author(s):  
Youssef El Halal ◽  
Crístofer Marques ◽  
Luiz Rocha ◽  
Liércio Isoldi ◽  
Rafael Lemos ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Coanda Effect ◽  
Water Flows ◽  
Operational Principle ◽  
Coandǎ Effect ◽  
Marine Applications

In the present work it is performed a numerical study for simulation of turbulent air and water flows in a nozzle based on the Coanda effect named H.O.M.E.R. (High-Speed Orienting Momentum with Enhanced Reversibility). The main purposes of this work are the development of a numerical model for simulation of the main operational principle of the H.O.M.E.R. nozzle, verify the occurrence of the physical principle in a device using water as working fluid and generate theoretical recommendations about the influence of the difference of mass flow rate in two inlets and length of septum over the fluid dynamic behavior of water flow. The time-averaged conservation equations of mass and momentum are solved with the Finite Volume Method (FVM) and turbulence closure is tackled with the k-ε model. Results for air flow show a good agreement with previous predictions in the literature. Moreover, it is also noticed that this main operational principle is promising for future applications in maneuverability and propulsion systems in marine applications. Results obtained here also show that water jets present higher deflection angles when compared with air jets, enhancing the capability of impose forces to achieve better maneuverability. Moreover, results indicated that the imposition of different mass flow rates in both inlets of the device, as well as central septum insertion have a strong influence over deflection angle of turbulent jet flow and velocity fields, indicating that these parameters can be important for maneuverability in marine applications.

DROPLET SIZE AND VELOCITY MEASUREMENTS IN A CRYOGENIC JET FLAME OF A ROCKET-TYPE COMBUSTOR USING HIGH-SPEED IMAGING

2016 ◽  
Vol 26 (5) ◽  
pp. 411-438 ◽  
Author(s):  
Nicolas Fdida ◽  
Lucien Vingert ◽  
Arnaud Ristori ◽  
Yves Le Sant
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Velocity Measurements ◽  
High Speed Imaging ◽  
Jet Flame

Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2

2012 ◽  
Author(s):  
Rene Pecnik ◽  
Enrico Rinaldi ◽  
Piero Colonna
Keyword(s):  
Critical Point ◽  
Gas Turbine ◽  
Supercritical Co2 ◽  
High Speed ◽  
Power Plants ◽  
Compressible Flows ◽  
High Efficiency ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Maximum Pressure

The merit of using supercritical CO2 (scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal and nuclear energy conversion. Among the challenges which must be overcome in order to successfully bring the technology to the market, the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development. This paper reports a three-dimensional CFD study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor-liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility [1]. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier-Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. The CFD code has been validated on test cases which are relevant for this study, see Ref. [2,3]. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures [4]. Among the available models, the one based on reference equations of state for CO2 [5,6] has been selected, as implemented in one of the sub-libraries [7]. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology. A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid-vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.

scholarly journals Mechanisms of Atomization from Rotary Dental Instruments and Its Mitigation

2020 ◽  
pp. 002203452097964
Author(s):  
A. Sergis ◽  
W.G. Wade ◽  
J.E. Gallagher ◽  
A.P. Morrell ◽  
S. Patel ◽  
...  
Keyword(s):  
High Speed ◽  
Light Sheet ◽  
Care Providers ◽  
High Speed Imaging ◽  
Current Crisis ◽  
Worst Case ◽  
Tooth Contact ◽  
Dental Instruments ◽  
Dental Procedures ◽  
The Impact

Since the onset of coronavirus disease 2019, the potential risk of dental procedural generated spray emissions (including aerosols and splatters), for severe acute respiratory syndrome coronavirus 2 transmission, has challenged care providers and policy makers alike. New studies have described the production and dissemination of sprays during simulated dental procedures, but findings lack generalizability beyond their measurements setting. This study aims to describe the fundamental mechanisms associated with spray production from rotary dental instrumentation with particular focus on what are currently considered high-risk components—namely, the production of small droplets that may remain suspended in the room environment for extended periods and the dispersal of high-velocity droplets resulting in formites at distant surfaces. Procedural sprays were parametrically studied with variables including rotation speed, burr-to-tooth contact, and coolant premisting modified and visualized using high-speed imaging and broadband or monochromatic laser light–sheet illumination. Droplet velocities were estimated and probability density maps for all laser illuminated sprays generated. The impact of varying the coolant parameters on heating during instrumentation was considered. Complex structured sprays were produced by water-cooled rotary instruments, which, in the worst case of an air turbine, included droplet projection speeds in excess of 12 m/s and the formation of millions of small droplets that may remain suspended. Elimination of premisting (mixing of coolant water and air prior to burr contact) resulted in a significant reduction in small droplets, but radial atomization may still occur and is modified by burr-to-tooth contact. Spatial probability distribution mapping identified a threshold for rotation speeds for radial atomization between 80,000 and 100,000 rpm. In this operatory mode, cutting efficiency is reduced but sufficient coolant effectiveness appears to be maintained. Multiple mechanisms for atomization of fluids from rotatory instrumentation exist, but parameters can be controlled to modify key spray characteristics during the current crisis.

Design of a Centrifugal Turbo Compressor With the Working Fluid Water for the Operation in a Hybrid Sorption/Compression Heat Pump Cycle

2016 ◽  
Author(s):  
Thomas Eckert ◽  
Leo Dostal ◽  
Martin Helm ◽  
Christian Schweigler
Keyword(s):  
Heat Pump ◽  
High Speed ◽  
Fluid Dynamic ◽  
Pressure Ratio ◽  
Lithium Bromide ◽  
High Volume ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Working Fluid ◽  
Turbo Compressor

In various applications the use of sorption chillers and heat pumps is limited by the available temperature level of the driving heat source or the heat sink for export of reject heat. These constraints can be overcome by integrating an efficient high-speed transonic turbo compressor into the internal cycle of a thermally driven water/lithium bromide absorption heat pump. The operation in a hybrid heat pump with the refrigerant water implies specific challenges for the design of the compressor: Saturation pressures in the sub-atmospheric range, low vapor density, high volume flows and a targeted pressure ratio of 3 result in high impeller tip speeds with machine Mach numbers close to 1. Here the authors present a theoretical design study based on a numerical simulation of a centrifugal compressor, targeted at the given operating conditions. Evaluation of the results is conducted with regard to the relevant thermodynamic and fluid mechanic figures. The optimization of the impeller geometry comprises both fluid dynamic behavior and structural stability.

Experimental Measurement of In-Plane Rolling Nonpneumatic Tire Vibrations Using High-Speed Imaging

2019 ◽  
Vol 47 (3) ◽  
pp. 196-210
Author(s):  
Meghashyam Panyam ◽  
Beshah Ayalew ◽  
Timothy Rhyne ◽  
Steve Cron ◽  
John Adcox
Keyword(s):  
High Speed ◽  
Image Correlation ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
High Speed Imaging ◽  
Correlation Algorithm ◽  
Mode Decomposition ◽  
Series Of Experiments ◽  
Plane Deformations ◽  
Dominant Frequencies

ABSTRACT This article presents a novel experimental technique for measuring in-plane deformations and vibration modes of a rotating nonpneumatic tire subjected to obstacle impacts. The tire was mounted on a modified quarter-car test rig, which was built around one of the drums of a 500-horse power chassis dynamometer at Clemson University's International Center for Automotive Research. A series of experiments were conducted using a high-speed camera to capture the event of the rotating tire coming into contact with a cleat attached to the surface of the drum. The resulting video was processed using a two-dimensional digital image correlation algorithm to obtain in-plane radial and tangential deformation fields of the tire. The dynamic mode decomposition algorithm was implemented on the deformation fields to extract the dominant frequencies that were excited in the tire upon contact with the cleat. It was observed that the deformations and the modal frequencies estimated using this method were within a reasonable range of expected values. In general, the results indicate that the method used in this study can be a useful tool in measuring in-plane deformations of rolling tires without the need for additional sensors and wiring.

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