scholarly journals The design, instrumentation, and validation of a multiphase shock tube facility

2017 ◽  
Author(s):  
◽  
Constantine Gregory Avgoustopoulos
Keyword(s):  
Shock Tube ◽  
Quantitative Data ◽  
Velocity Difference ◽  
Gas Cylinder ◽  
First Case ◽  
Experimental Apparatus ◽  
Large Particles ◽  
Particle Imaging ◽  
Atwood Number ◽  
Number Of Particles

This paper investigates the experimental work in Shock Driven Multiphase Instabilities (SDMI). SDMIs occur when an interface consisting of a particle seeded gas is instantaneously accelerated and begins mixing. SDMIs have similar flow morphologies to the Richtmyer-Meshkov Instability (RMI), however, the driving force inducing this flow is very different. SDMIs occur when there is a relative velocity difference between surrounding gas and the moving particles. This results to a shear at the edges and ultimately leads to rollups that are similar to a RMI. To investigate this phenomena, a shock tube facility was designed, calibrated, and tested to perform experiments. The experimental data was qualitatively compared to simulations performed, as well as to literature of similar experiments. Quantitative data was analyzed using Particle Imaging Velocimetry (PIV) to understand the flow of the instability. The flow morphologies observed in experiments have similar behavior to those performed in simulations. Additionally, the qualitative observations of experiments performed in this lab are also in agreement with experimental literature. Two different effective Atwood numbers are investigated in this study. The first case looks at a gas cylinder interface with an effective Atwood number of -0.01 and a gas Atwood number of -0.02, shocked with a Mach 1.66 shock wave. The observations show a dominating instability resulting in the gas Atwood number. What ends up happening is the smaller particles are pulled into the vortex and the large particles separate and trail behind. The second case looks at the same gas cylinder perturbation but with an effective Atwood number of 0.03 and a gas Atwood number of 0, shocked at Mach 1.66. The higher Atwood number was achieved by modifying the experimental apparatus slightly to deliver a greater number of particles to the shock tube. The experiments observed show that there is agreement with literature and simulations. Certain unusual filaments begin forming at late times, 4.0ms after shock. This was thought to only appear in a pure RMI. In the case of a SDMI, these filaments are a result of colliding particles.

scholarly journals Experimental investigation of cylindrical converging shock waves interacting with a polygonal heavy gas cylinder

2015 ◽  
Vol 784 ◽  
pp. 225-251 ◽  
Author(s):  
Ting Si ◽  
Tong Long ◽  
Zhigang Zhai ◽  
Xisheng Luo
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
High Speed ◽  
Initial Conditions ◽  
Laser Sheet ◽  
Imaging Method ◽  
Gas Cylinder ◽  
Diaphragmless Shock Tube ◽  
Converging Shock Waves ◽  
Heavy Gas

The interaction of cylindrical converging shock waves with a polygonal heavy gas cylinder is studied experimentally in a vertical annular diaphragmless shock tube. The reliability of the shock tube facility is verified in advance by capturing the cylindrical shock movements during the convergence and reflection processes using high-speed schlieren photography. Three types of air/SF6 polygonal interfaces with cross-sections of an octagon, a square and an equilateral triangle are formed by the soap film technique. A high-speed laser sheet imaging method is employed to monitor the evolution of the three polygonal interfaces subjected to the converging shock waves. In the experiments, the Mach number of the incident cylindrical shock at its first contact with each interface is maintained to be 1.35 for all three cases. The results show that the evolution of the polygonal interfaces is heavily dependent on the initial conditions, such as the interface shapes and the shock features. A theoretical model for circulation initially deposited along the air/SF6 polygonal interface is developed based on the theory of Samtaney & Zabusky (J. Fluid Mech., vol. 269, 1994, pp. 45–78). The circulation depositions along the initial interface result in the differences in flow features among the three polygonal interfaces, including the interface velocities and the perturbation growth rates. In comparison with planar shock cases, there are distinct phenomena caused by the convergence effects, including the variation of shock strength during imploding and exploding (geometric convergence), consecutive reshocks on the interface (compressibility), and special behaviours of the movement of the interface structures (phase inversion).

scholarly journals ANALYSIS OF COVID-19 CONTAMINATION AND DEATHS CASES IN BRAZIL ACCORDING TO THE NEWCOMB-BENFORD

2021 ◽  
Vol 39 (4) ◽  
pp. 522-535
Author(s):  
Carlos Roberto Souza CARMO ◽  
Fernando de Lima CANEPPELE ◽  
Fábio Caixeta NUNES
Keyword(s):  
Information Systems ◽  
Quantitative Data ◽  
Descriptive Statistics ◽  
Absolute Deviation ◽  
First Case ◽  
The Moment ◽  
Benford Law

The use of the Newcomb-Benford Law in assessing the quality of health and / orepidemiological information systems can allow relevant decisions to be made to improve these systems. In this context, this research aimed to carry out an assessment of the conformity of theinformation regarding the number of cases of contamination and deaths by COVID-19 in Brazil according to the Newcomb-Benford Law, from the moment of the occurrence of the first case of the disease and from the first death by COVID-19 in the country until the month of September 2020. With the aid of descriptive statistics and the use of metrics related to the Z test and themean absolute deviation it was possible to observe that, both from a national and longitudinal perspective as for the transversal-state perspective, the quantitative data referring to the cases of contamination by the coronavirus and the deaths that occurred as a result of COVID-19 did not present the expected behavior according to the Newcomb-Benford Law. Due to the lack of conformity in relation to the Newcomb-Benford Law, it is suspected that some level of conformity specific to this type of data has occurred, in the Brazilian context, since there are already studies that suggest the existence of proper levels of conformity for certain types of data.

scholarly journals Enhancement of Cleanliness and Deposition Rate by Understanding the Multiple Roles of the Showerhead Electrode in a Capacitively Coupled Plasma Reactor

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 999
Author(s):  
Ho Jun Kim
Keyword(s):  
Deposition Rate ◽  
Complex Geometry ◽  
Plasma Reactor ◽  
Three Dimensional ◽  
Multiple Roles ◽  
Capacitively Coupled ◽  
Large Particles ◽  
Capacitively Coupled Plasma ◽  
Physical Phenomena ◽  
Number Of Particles

Increasing the productivity of a showerhead-type capacitively coupled plasma (CCP) reactor requires an in-depth understanding of various physical phenomena related to the showerhead, which is not only responsible for gas distribution, but also acts as the electrode. Thus, we investigated how to enhance the cleanliness and deposition rate by studying the multiple roles of the showerhead electrode in a CCP reactor. We analyzed the gas transport in a three-dimensional complex geometry, and the SiH4/He discharges were simulated in a two-dimensional simplified geometry. The process volume was installed between the showerhead electrode (radio frequency powered) and the heater electrode (grounded). Our aim of research was to determine the extent to which the heated showerhead contributed to increasing the deposition rate and to reducing the size of the large particles generated during processing. The temperature of the showerhead was increased to experimentally measure the number of particles transported onto the heater to demonstrate the effects thereof on the decrease in contamination. The number of particles larger than 45 nm decreased by approximately 93% when the showerhead temperature increased from 373 to 553 K.

Interference and diffraction experiment using 3D printing and Arduino

2021 ◽  
Vol 57 (2) ◽  
pp. 025011
Author(s):  
P A Paixão ◽  
V M C Remonatto ◽  
L B Calheiro ◽  
D D Dos Reis ◽  
A M B Goncalves
Keyword(s):  
Quantitative Data ◽  
Low Cost ◽  
Position Sensor ◽  
Linear Stage ◽  
Light Passing ◽  
Experimental Apparatus ◽  
Physics Laboratories ◽  
3D Printed ◽  
Double Slit Experiment ◽  
Slit Experiment

Abstract Here, we present a 3D printed experimental apparatus that students can use to acquire interference and diffraction quantitative data from light passing through a single or double-slit experiment. We built a linear screw stage with a multiturn potentiometer connected to its leadscrew as a position sensor. Using an Arduino, we collected light intensity data (from a photodiode mounted in the linear stage) as a function of position. The apparatus is a low-cost and compact alternative with data acquisition to optics physics laboratories.

scholarly journals Some experiments concerning the counting of scintillations produced by alpha particles.—Part III. Practical applications

1929 ◽  
Vol 122 (789) ◽  
pp. 335-352 ◽  
Keyword(s):  
Numerical Aperture ◽  
Alpha Particles ◽  
Resolving Power ◽  
Applied Physics ◽  
Practical Applications ◽  
First Case ◽  
Definition Of ◽  
At Will ◽  
Number Of Particles

There are two important characteristics of the microscope or any other optical system used for scintillation counting, which may influence the number observed, namely, the numerical aperture and the magnification. In order to show clearly the role of each factor it seemed desirable to investigate how the percentage of the number of particles observed varied with the numerical aperture in two cases where the magnification was widely different. The first case chosen was the counting of scintillations with a microscope of magnification 50, where the numerical aperture could be varied at will by placing stops on the objective. Stops of black paper which fitted the objective and could be easily interchanged in the dark were used. The numerical aperture corresponding to each objective stop was measured in the usual way (see, for example, ‘Dictionary of Applied Physics,’ vol. 4, p. 205 (1923)). The importance of the numerical aperture is not due to its influence on resolving power, but to its influence on the fraction of the light from a scintillation which enters the objective. From the definition of numerical aperture it follows that the fraction of the light entering the objective from the object viewed is ½ (1 — √ 1— ( n.a ) 2 ).

scholarly journals Electrospray sample injection for single-particle imaging with x-ray lasers

2019 ◽  
Vol 5 (5) ◽  
pp. eaav8801 ◽  
Author(s):  
Johan Bielecki ◽  
Max F. Hantke ◽  
Benedikt J. Daurer ◽  
Hemanth K. N. Reddy ◽  
Dirk Hasse ◽  
...  
Keyword(s):  
Generation X ◽  
Room Temperature ◽  
Protein Structure Determination ◽  
High Temporal Resolution ◽  
X Ray ◽  
Free Sample ◽  
Large Particles ◽  
Particle Imaging ◽  
Single Particle Imaging ◽  
Initial Droplet Size

The possibility of imaging single proteins constitutes an exciting challenge for x-ray lasers. Despite encouraging results on large particles, imaging small particles has proven to be difficult for two reasons: not quite high enough pulse intensity from currently available x-ray lasers and, as we demonstrate here, contamination of the aerosolized molecules by nonvolatile contaminants in the solution. The amount of contamination on the sample depends on the initial droplet size during aerosolization. Here, we show that, with our electrospray injector, we can decrease the size of aerosol droplets and demonstrate virtually contaminant-free sample delivery of organelles, small virions, and proteins. The results presented here, together with the increased performance of next-generation x-ray lasers, constitute an important stepping stone toward the ultimate goal of protein structure determination from imaging at room temperature and high temporal resolution.

Thickness and volume measurements of a Richtmyer–Meshkov instability-induced mixing zone in a square shock tube

1997 ◽  
Vol 349 ◽  
pp. 67-94 ◽  
Author(s):  
G. JOURDAN ◽  
L. HOUAS ◽  
J.-F. HAAS ◽  
G. BEN-DOR
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Cross Section ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Mixing Zone ◽  
Laser Absorption ◽  
Shock Wave Mach Number ◽  
Atwood Number ◽  
Absorption Technique

A simultaneous three-directional laser absorption technique for the study of a shock-induced Richtmyer–Meshkov instability mixing zone is reported. It is an improvement of a CO2 laser absorption technique, using three detectors during the same run, through three different directions of the test section, for the simultaneous thickness measurement of the mixing zone near the corner, near the wall and at the centre of a square-cross-section shock tube. The three-dimensional mean front and rear shapes of the mixing zone, its thickness and volume are deduced from the experimental measurements. The cases when the shock wave passes from a heavy gas to a light one, from one gas to another of similar densities and from a light gas to a heavy one, are investigated before and after the mixing zone compression by the reflected shock, for different incident shock wave Mach numbers. It is shown that the mixing zone is strongly deformed by the wall boundary layer when it becomes turbulent. Consequently, the thickness of the mixing zone is not constant along the shock tube cross-section, and the measurement of the mean volume of the mixing zone appears to be more appropriate than its mean thickness at the centre of the shock tube. The influence of the incident shock wave Mach number is also studied. When the Atwood number tends to zero, we observe a limit-like regime and the thickness, or the volume, of the mixing zone no longer varies with the incident shock wave Mach number. Furthermore, a series of experiments undertaken with an Atwood number close to zero enabled us to define a membrane-induced minimum mixing thickness, L0, depending on the initial configuration of the experiments. From the experimental data, a hypothesis about the mixing zone thickness evolution law with time is deduced on the basis of L0. The results are found to follow two very different laws depending on whether they are considered before or after the establishment of the plenary turbulent regime. However, no general trend can be determined to describe the entire phenomenon, i.e. from the initial conditions until the turbulent stage.

Direct Imaging of Nanoparticle Embedding into PS Films

2002 ◽  
Vol 734 ◽  
Author(s):  
J.H. Teichroeb ◽  
J.A. Forrest
Keyword(s):  
Annealing Time ◽  
Sample Surface ◽  
Nano Particles ◽  
Silicon Substrates ◽  
Force Microscopy ◽  
Atomic Force ◽  
First Case ◽  
Large Numbers ◽  
20 Nm ◽  
Number Of Particles

ABSTRACTNon-contact Atomic Force Microscopy (AFM) was used to study the embedding of 10 nm and 20 nm gold nano-particles into the surface of polystyrene films spin-coated onto silicon substrates. The rate of embedding was determined by measuring the apparent nanosphere height as a function of annealing time. This was accomplished by two different methods. In the first case, each image (after a specific annealing time) is acquired at a different spot on the sample surface. In this case a fairly large (∼40) number of particles were imaged in order to have acceptable statistics. A second method involved the use of a kinematic mounting hot stage that allowed the same spot on the sample to be imaged at each time. This allows the same final precision without the same necessity for imaging large numbers of particles. The results indicate that sub nm resolution is easily obtainable with either technique.

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