scholarly journals Effect of air pockets in drug delivery in jet injections

2021 ◽  
Author(s):  
Pankaj Rohilla ◽  
Emil Khusnatdinov ◽  
Jeremy Marston
Keyword(s):  
Volumetric Flow Rate ◽  
Temporary Increase ◽  
Air Bubbles ◽  
Spray Formation ◽  
Free Jet ◽  
Product Loss ◽  
Exit Speed ◽  
Pass Through ◽  
Entrapped Air ◽  
Air Pockets

Needle-free jet injections are actuated by a pressure impulse that can be delivered by different mechanisms, and the resultant jets are (102) m/s. Here, we report on the effect of entrapped air bubbles since filling procedures for pre-filled ampoules can induce bubbles, especially for viscous fluids. We use spring-piston devices as the principal actuation mechanism and vary both the location and size of the initial bubble. We find that the bubble location does have a statistically significant (p < 0.05) effect on the jet exit speed, based upon the volumetric flow rate. However, we reveal subtle features such as intermittent atomization when the gas pockets pass through the orifice and de-pressurize, which leads to spray formation and a temporary increase in jet dispersion, both of which can lead to product loss during an injection. These results have implications for the development of prefilled ampoules for jet injection applications.

Entrapment, stability, and persistence of air bubbles in soil water

Soil Research ◽  
1969 ◽  
Vol 7 (2) ◽  
pp. 79 ◽  
Author(s):  
AJ Peck
Keyword(s):  
Hydraulic Conductivity ◽  
Moisture Content ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Equilibration Time ◽  
Air Bubbles ◽  
Air Entrapment ◽  
Water Characteristics ◽  
Spherical Bubbles ◽  
Entrapped Air

Air bubbles in soil water affect both hydraulic conductivity and moisture content at a given capillary potential. Consequently changes in the volume of entrapped air, which are not included in the specification of relationships between hydraulic conductivity, moisture content, and capillary potential, will affect all soil-water interactions. Current understanding of the process of air bubble entrapment during infiltration suggests that, in nature, significant air entrapment will often occur. It is shown that infiltrating water can dissolve only a very small volume of air, much less than the amount usually entrapped. Air bubbles in saturated soils are unstable since their pressure must exceed atmospheric, resulting in a diffusive flux of dissolved air from bubbles to menisci contacting the external atmosphere. However, stable bubbles are possible in unsaturated soils. Bubbles which are constrained by pore architecture to non-spherical shapes are usually stable, and spherical bubbles can be stable when the magnitude of the capillary potential exceeds about 3 bars. An approximate analysis of the characteristic time of bubble equilibration indicates that, in an example, it is of order 104 sec, but it may be greater or less by at least a factor 10. Since the equilibration time will be often at least as large as the period of significant soil temperature changes, it cannot be assumed that the entrapped air in a field soil is in an equilibrium state. In such circumstances unstable bubbles may be quasi-permanent. It is suggested that the slow growth of entrapped bubbles may account for the anomalously slow release of water observed in some outflow experiments. Changes of entrapped air volume may also account for the reported dependence of soil-water characteristics on the magnitude of the steps of capillary potential.

The Pore-network Modelling of the Infiltration Experiments Performed on Unsaturated Coarse Sands

2021 ◽  
Author(s):  
Tomáš Princ ◽  
Michal Snehota
Keyword(s):  
Hydraulic Conductivity ◽  
Network Model ◽  
Pore Network ◽  
Pore Network Model ◽  
Air Bubbles ◽  
Network Modelling ◽  
Air Content ◽  
Pore Network Modelling ◽  
X Ray Computed ◽  
Entrapped Air

&lt;p&gt;The research focused on the simulation of the previous experiment described by Princ et al. (2020). The relationship between entrapped air content (&lt;em&gt;&amp;#969;&lt;/em&gt;) and the corresponding satiated hydraulic conductivity (&lt;em&gt;K&lt;/em&gt;) was investigated for two coarse sands, in the experiment. Additionally the amount and distribution of air bubbles were quantified by X-ray computed tomography.&lt;/p&gt;&lt;p&gt;The pore-network model based on OpenPNM platform (Gostick et al. 2016) was used to attempt simulation of a redistribution of the air bubbles after infiltration. Satiated hydraulic conductivity was determined to obtain the &lt;em&gt;K&lt;/em&gt;(&lt;em&gt;&amp;#969;&lt;/em&gt;) relationship. The results from pore-network model were compared with the results from experiments.&lt;/p&gt;&lt;p&gt;Gostick et al. (2016). Computing in Science &amp; Engineering. 18(4), p60-74.&lt;/p&gt;&lt;p&gt;Princ et al. (2020). Water. 12(2), p1-19.&lt;/p&gt;

A New Method for Performance Measurement of PPV Fans for Fire Fighting Under Realistic Conditions

2020 ◽  
Author(s):  
Michael Steppert ◽  
Philipp Epple ◽  
Michael Steber ◽  
Stefan Gast
Keyword(s):  
Design Process ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Navier Stokes ◽  
Analytical Relation ◽  
Positive Pressure ◽  
Flow Rates ◽  
Free Jet ◽  
Actual Flow Rate ◽  
Coefficient Of Discharge

Abstract PPV Fans (Positive Pressure Ventilation Fans) are used in firefighting to remove smoke from a burning building, so that fire fighters can have a clear view inside the house and injured people do not have to breathe toxic smoke. This can be done by placing a PPV fan in a distance of about two meters in front of a door of the burning building. On another, carefully chosen position in the building, e. g. a window, a door or at the roof an opening has to be created, where the smoke can leave the building. The same volumetric flow rate of gas that is blown into the building by the PPV fan has to leave the building at a chosen opening. Because the gas entering the building is air and the gas leaving the building is a mixture of smoke and air, the smoke concentration in the building can be reduced. To test the performance of such PPV fans, a test building with a door in the first floor and a window in the 3rd floor has been built. To measure the volumetric flow rate of the smoke and air mixture through the window in the 3rd floor that is leaving the building, a flow meter nozzle was designed. The design process was done using the commercial Navier Stokes solver Star CCM+, where three nozzle designs, such as a nozzle with constant velocity increase, a quarter circle nozzle and a non-curved nozzle were investigated for different volumetric flow rates. Also, a rounding at the window, where the nozzle is placed, was investigated to prevent flow detachment and shock losses at the inlet of the nozzle. The volumetric flow rate through the nozzle can be calculated, by measuring the pressure at the nozzle wall (before the contraction) and applying Bernoulli’s law, the continuity equation and assuming atmospheric pressure at the free jet flow at the end of the nozzle. The so calculated volumetric flow rate was compared with the actual flow rate, given by the numerical CFD simulations. With these values, the nozzle specific coefficient of discharge for several volumetric flow rates has been calculated and a function fitting was done to get obtain analytical relation between pressure and volumetric flow rate. The detailed design process of the three nozzles, the numerical results of the CFD studies and the determination of the nozzle specific coefficients of discharge are shown and discussed in detail in this work.

Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jane Alexander ◽  
Pedro J. Lee ◽  
Mark Davidson ◽  
Huan-Feng Duan ◽  
Zhao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Wave Speed ◽  
Numerical Models ◽  
Diagnostic Process ◽  
Air Pocket ◽  
Fluid Transients ◽  
Entrapped Air ◽  
Air Pockets ◽  
The Given ◽  
Potential Tool

Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modeling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modeling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time-delay errors. The time-delay error could be partially overcome by combining the two models.

scholarly journals The Morphology of Ice and Liquid Brine in the Environmental SEM: A Study of the Freezing Methods

2019 ◽  
Author(s):  
Ľubica Vetráková ◽  
Vilém Neděla ◽  
Jiří Runštuk ◽  
Dominik Heger
Keyword(s):  
Time Lapse ◽  
Solute Concentration ◽  
Environmental Scanning ◽  
Air Bubbles ◽  
Ice Recrystallization ◽  
Naturally Occurring ◽  
Polycrystalline Ice ◽  
Entrapped Air ◽  
The Impact

Abstract. The microstructure of polycrystalline ice with a threading solution of brine controls its numerous characteristics, including the ice mechanical properties, ice-atmosphere interactions, sea-ice albedo, and (photo)chemical behavior in/on the ice. Ice samples were previously prepared in laboratories to study various facets of ice-impurities interactions and (photo)reactions to model natural ice-impurities behavior. We examine the impact of the freezing conditions and solute (CsCl used as a proxy for naturally occurring salts) concentrations on the microscopic structure of ice samples via an environmental scanning electron microscope. The method allows us to observe in detail the ice surfaces, namely, the free ice, brine puddles, brine-containing grain boundary grooves, individual ice crystals, and imprints left by entrapped air bubbles at temperatures higher than −25 °C. The amount of brine on the external surface is found proportional to the solute concentration and is strongly dependent on the sample preparation method. Time-lapse images in the condition of slight sublimation reveal sub-surface association of air bubbles with brine. With rising temperature (up to −14 °C), the brine surface coverage increases to remain enhanced during the subsequent cooling and until the final crystallization below the eutectic temperature. The ice recrystallization dynamics identifies the role of surface spikes in retarding the ice boundaries propagation (Zeener pining). The findings thus quantify the amounts of brine exposed to incoming radiation, available for the gas exchange, and influencing other mechanical and optical properties of ice. The results have straightforward implications for artificially prepared and naturally occurring salty ices.

On the Hydraulics of Downward Sloping Pipes With Entrapped Air Pockets

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
H. A. Warda ◽  
E. M. Wahba ◽  
E. N. Ahmed
Keyword(s):  
Hydraulic Jump ◽  
Open Channel ◽  
Numerical Results ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Dynamics Model ◽  
Computational Fluid Dynamics Model ◽  
Air Pocket ◽  
Entrapped Air ◽  
Air Pockets

Abstract In this study, air–water flow in a downward sloping pipe subsequent to the entrapping of an air pocket is investigated both numerically and experimentally. A transient, two-dimensional computational fluid dynamics model is applied to study the different possible flow regimes and their associated phenomena. The numerical model is based on the Reynolds-averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) method. Both numerical and experimental investigations provide visualization for the hydraulic jump, the blowback regime, and the full gas transport regime. The numerical results predict that the flow structure in the pipe downstream the toe of the hydraulic jump is subdivided into three distinct regions including the jet layer, the shear zone, and the circulation region, which agrees qualitatively with the previous investigations of the hydraulic jump characteristics in open channel flow. Numerical results are in reasonable agreement with the experimental measurements of the circulation length and the hydraulic jump head loss.

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