A Study on Gap Influence on Slamming Experiment

2012 ◽  
Author(s):  
C. W. Park ◽  
J. Y. Shin ◽  
S. H. Kwon ◽  
J. Y. Chung ◽  
S. B. Lee ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Gap Effect ◽  
High Speed Camera ◽  
Tank Wall ◽  
Central Location ◽  
The Difference

This study presents an investigation of gap effect on slamming experiment. Two gaps were considered; a gap between transverse side of a model and tank wall and a gap between longitudinal end and end of a model. The deadrise angle was fixed 0°. The pressure was measured at the central location and compared. Three different drop heights were chosen to see the difference. A High speed camera was used to record the flow field. Therefore pressure at the center, and flow field around corner of the specimen were analyzed to investigate the gap effect in slamming experiment. The results showed that there was clear influence of the gap in slamming experiment.

Investigation of the effect of viscosity on slug flow in airlift tubular membranes in search of a sludge surrogate

2010 ◽  
Vol 61 (7) ◽  
pp. 1801-1809 ◽  
Author(s):  
N. Ratkovich ◽  
C. C. V. Chan ◽  
P. R. Bérubé ◽  
I. Nopens
Keyword(s):  
Activated Sludge ◽  
Carboxymethyl Cellulose ◽  
Slug Flow ◽  
High Speed ◽  
Vertical Tube ◽  
High Speed Camera ◽  
Flow Rates ◽  
The Difference ◽  
Newtonian Liquids ◽  
Tubular Membranes

The behaviour of three different liquid-gas slug flows (water, carboxymethyl cellulose and activated sludge) in a vertical tube was studied using a high speed camera (HSC). Experiments were performed using different flow rates and two tube diameters (6.3 and 9.9 mm). The observed difference in behaviour of the ascending gas slugs can be explained by the difference in viscosity of the fluids (Newtonian and non-Newtonian). Moreover, it was observed that the degree of coalescence of gas slugs is lower for non-Newtonian liquids and they behave like a succession of slugs without actually coalescing into a single larger gas slug. Finally, gas slug rising velocities were also extracted, but no subsequent difference in the rising velocities of the different fluids was found.

Air Flow Field and Fiber Motion in a Swirl Die Melt-Blowing Process

2013 ◽  
Vol 690-693 ◽  
pp. 2861-2865
Author(s):  
Sheng Xie ◽  
Yuan Sheng Zheng ◽  
Yong Chun Zeng
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Air Flow ◽  
High Speed Camera ◽  
Important Process ◽  
Melt Blowing ◽  
Spiral Motion ◽  
Fiber Motion ◽  
Fiber Path ◽  
The Relationship

Melt blowing is an important process for producing nanofibrous nonwovens. Compared to another technology for producing nanofibrous nonwovens, electrospinning, melt blowing applies high-speed air flow field to attenuate the extruded polymer jet. In this study, the air flow field of a swirl die melt-blowing process was simulated by CFD software, Fluent 6.3. The swirling air profile was shown. Meanwhile, a high-speed camera was used to capture the fiber path below a single-orifice melt-blowing swirl die. The spiral motion of the fiber was revealed. The relationship between the fiber path and the air flow field was discussed. This paper shows the relationship between the fiber path and the air flow field in a swirl die melt-blowing process.

Experimental Visualization Study on the Explosion Process of Gasoline Vapor in Narrowly-Confined Space

2013 ◽  
Vol 791-793 ◽  
pp. 2108-2111 ◽  
Author(s):  
Jian Jun Liang ◽  
Yang Du ◽  
Yi Hong Ou ◽  
Xin Sheng Jiang ◽  
Hai Bing Qian ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Data Acquisition ◽  
High Speed ◽  
Development Stage ◽  
High Speed Camera ◽  
Confined Space ◽  
Vapor Explosion ◽  
Gasoline Vapor ◽  
Explosion Process

In this paper, experimental study on gasoline vapor explosion was conducted with data acquisition technology of high-speed camera. In the experiments, the flame behaviors and the flow field movements were shot by the high-speed camera, the space pressure were recorded by high-speed dynamic tester, and the explosion process were analyzed refinedly and intuitively. Studies have shown that according to variations of flame behaviors and pressure characteristics, process of gasoline vapor explosion can be divided into four stages: the ignition stage, the development stage, the intensification stage and the plume stage.

An Experimental Study of Influence of Slits in Throat Position on Suppression of Cavitation Instabilities in Liquid Propellant Rocket Inducer

2019 ◽  
Author(s):  
Moena Kanamaru ◽  
Yoshito Kamikura ◽  
Satoshi Kawasaki ◽  
Takashi Shimura ◽  
Iga Yuka
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Pressure Fluctuation ◽  
High Speed ◽  
Cavity Length ◽  
High Speed Camera ◽  
Liquid Propellant ◽  
Suppression Effect ◽  
Suction Performance ◽  
Propellant Rocket

Abstract Experiments of an inducer with symmetric slits were conducted. The purpose of the study is to explore the suppression effect on cavitation instabilities by slits. The slits are located in a throat position in each blade and it means symmetric slits. The experiments are done through measuring pressure fluctuation in the flow field and shaft displacement and visualization using high speed camera. In this study, the head performance, the suction performance, the cavity length and the occurrence range and the strength of the cavitation instabilities are compared with the results of inducer without slit. As a result, the slit in throat position does not give bad effect on head performance, improves suction performance, and has a relation to suppression of oscillation of cavitation instabilities because of the suppression effect of cavity length, although the occurrence range of super-synchronous rotating cavitation unfortunately increases because the cavity develops slowly.

Flow Field, Spray Distribution and Pilot Flame Stabilization in a Centrally Staged Combustor

2020 ◽  
Author(s):  
Bo Wang ◽  
Guangming Ren ◽  
Xiaohua Gan ◽  
Yuzhen Lin
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Stability Boundary ◽  
Critical Time ◽  
Flame Stabilization ◽  
Cycle Duration ◽  
High Speed Camera ◽  
Double Root ◽  
Fuel Distribution ◽  
Spray Distribution

Abstract Centrally staged lean premixed prevaporized low emission combustor has achieved great commercial success in the past decade. Pilot flame characteristics is with key importance to centrally staged combustor, which is considered not entirely up to the design of pilot stage, but also influenced by the flow field and fuel distribution of the combustor. The flow field and fuel distribution behaviors in centrally staged combustor are not very clear since the role of LRZ is unknown, as well as the pilot flame stabilization mechanism. The goal of this paper is to study the flow field, spray distribution and pilot flame stabilization in centrally staged combustor. This paper designs a comparison scheme of the dome lip for study. Particle image velocimetry, Planar Mie scattering measurements and high-speed camera experiments are conducted to get an in depth understanding on the flow field, spray distribution characteristics and pilot flame stabilization in a centrally staged combustor. The flow field with a 3.0 mm lip incline is quite different. Two PRZs forms, one connected with the LRZ and the other at the outlet of pilot stage. Pilot flow no longer joins to the main flow but flows alone in the center. It seems like it is the decoupling pilot stage air cutting PRZ into two PRZs. The pilot spray has a conical boundary and it is probably formed by the high velocity main air flow. A considerable number of fuel droplets are involved in LRZ with the lip incline. Two shapes of pilot flame are observed, the V-shaped flame and double root flame. High-speed camera has captured the flame stabilization process close to LBO. As for the V-shaped pilot flame, the central flame root performs an extinction/relight cycle close to LBO. The cycle duration time is much longer than the critical time of swirl cup methane flame previously reported. As for the double root pilot flame, the central flame root is lighted before the lip flame root and it is the central flame that plays the leading role in stabilizing the whole flame. The lip flame root can weaken the quench effect of main air and broaden the flame stability boundary. A relatively large lip height is recommended for the consideration of the LBO performance.

THE KINEMATIC DIFFERENCES OF THREE TYPES OF CROUCHED POSITIONS DURING A SPRINT START

2016 ◽  
Vol 16 (07) ◽  
pp. 1650099 ◽  
Author(s):  
YO CHEN ◽  
KUANG-YA WU ◽  
YU-JU TSAI ◽  
WEN-TIEN YANG ◽  
JIA-HAO CHANG
Keyword(s):  
Repeated Measures ◽  
High Speed ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Step Length ◽  
Linear Velocity ◽  
High Speed Camera ◽  
Starting Position ◽  
The Difference ◽  
The Ideal

This study identifies the optimal crouched starting positions (elongated, medium, or bunched) from push-off to the first two steps. Seven elite sprinters were recruited as participants in this study (aged: 21[Formula: see text][Formula: see text][Formula: see text]2 years). A high-speed camera (250[Formula: see text]Hz) was used to collect motion-based images on a sagittal plane. Kwon3D (software) was used to analyze the center of mass (COM) movement, step length, foot linear velocity, take-off angle, and trunk angle. Participants were tested in a 60[Formula: see text]m sprint for bunched, medium, and elongated starting positions. A one-way analysis of variance (ANOVA) ([Formula: see text]) with repeated measures was performed to determine the difference in kinematics in the three crouched starting positions. The LSD comparison was applied to examine differences among pairs of means. Our results indicated that the medium starting position demonstrated a greater first step length and foot linear velocity when compared to the bunched starting position. In the first step toe-off, a lower COM vertical velocity was observed in the medium starting position when compared with the elongated starting position. This study concluded that the medium starting position was the ideal starting position.

scholarly journals Polarity symmetry of leaders in moist air

2021 ◽  
Author(s):  
Shengxin Huang ◽  
Weijiang Chen ◽  
Zhong Fu ◽  
Weidong Shi ◽  
Nianwen Xiang ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
High Speed ◽  
High Speed Camera ◽  
Moist Air ◽  
Macroscopic Behavior ◽  
Outstanding Problem ◽  
The Difference ◽  
Insight Into ◽  
Bidirectional Development

Abstract The most important physics underlying lightning is the leader discharge. The presence or absence of space stems/leaders in leader steps is the key to the polarity asymmetry of leaders, which describes the difference in macroscopic behavior between positive and negative leaders and is a long-term consensus among lightning physicists. It is generally believed that negative leader steps are led by space stem, and there is no space stem/leader in positive leader discharges. Here we report the emergence of the space stem and the bidirectional development of the space leader in positive leader steps in moist air, using a high-speed camera with unprecedented spatial-temporal resolution. The lifetime of space stem/leader in positive leader steps is shorter than that in negative leader steps, causing the uncover of space stem/leader in previous studies. The bidirectional development of space leaders in positive leader steps may be an important source for VHF radiations, illuminating insight into the outstanding problem that how positive lightning leaders produce VHF radiation.

Investigation on Jet Breakup of High-Viscous Fuels for Entrained Flow Gasification

2016 ◽  
Author(s):  
Thomas Müller ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Alexander Sänger ◽  
Tobias Jakobs ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Liquid Jet ◽  
Liquid Viscosity ◽  
High Speed Camera ◽  
Entrained Flow ◽  
Jet Breakup ◽  
Entrained Flow Gasification

The present study focuses on the atomization behaviour of liquids in external mixing twin fluid nozzles and investigates a wide range of viscosities as well as different nozzle geometries at a gas to liquid ratio (GLR) typically used in entrained flow gasification. In a first stage experiments were performed using water and water-glycerol-mixtures as Newtonian model fuels with liquid viscosity up to 400 mPa s. Jet breakup was investigated qualitatively using a high speed camera as well as using a PIV and LDA-System for detailed quantitative investigation of the flow field. Two different primary instabilities flapping and pulsating mode were detected which are dependent on operating conditions of the nozzle (e.g. GLR) and rheological properties of the liquid phase (e.g. liquid viscosity) as well as nozzle geometry. For better interpretation of the phenomena occurring during jet breakup a frequency-analysis of the primary instabilities was performed using the pictures of the high speed camera. In addition, compressible large eddy simulations (LES) were preformed to describe the experimental observations and to capture the morphology of the primary breakup as well as the important flow field characteristics. The numerical simulations were conducted by means of the open source CFD software OpenFOAM. A Volume of Fluid (VOF) approach was used to track the unsteady evolution and breakup of the liquid jet. Comparison of experimental and numerical results shows a good agreement concerning breakup frequency, velocity fields and morphology. The breakup frequency varied in a range of 430 to 757 Hz depending on operating condition and nozzle geometry. Based on these results a more detailed understanding of the physics leading to liquid jet breakup and finally atomization process will be available.

scholarly journals Visualization of water droplet deformation and breakup in a continuously accelerating flow field

2017 ◽  
Author(s):  
Adelaida Garcia-Magariño ◽  
Suthyvann Sor ◽  
Angel Velazquez
Keyword(s):  
High Resolution ◽  
Flow Field ◽  
High Speed ◽  
High Speed Camera ◽  
Breakup Process ◽  
Droplet Deformation ◽  
Direct Illumination ◽  
Accelerated Flow ◽  
Accelerating Flow ◽  
Fine Tune

A new specific direct illumination technique is proposed for studying the deformation and breakup process ofdroplets that are exposed to a continuously increasing flow field. This type of flow field is in contrast to the traditional shock-tube experiments where droplets are suddenly exposed to a constant high airstream. In order to generate a continuously accelerated flow field the rotating arm facility at INTA is used. Droplets are allowed to fall in the path of an incoming airfoil mounted at the end of a rotating arm. Under certain conditions, these droplet deform and breakup before impinging on the airfoil. The incoming airfoil is a key element in the illumination technique. Droplets of 0.8 mm of diameter immersed in the flow field generated by an airfoil model of chord 0.690m approaching at 80 m/s were chosen for this study and were found to undergo a breakup process similar to the bag and stamen breakup found in the literature. Each of the stages at this type of breakup process was investigated by means of this new direct illumination technique and a high resolution camera. These images were compared to those images obtained using shadowgraph illumination technique and a high speed camera under the same conditions. Five different stages were studied and characterized. The final objective in this study was to visualize and identify fluid structures that occur during the deformation and breakup process in a continuouslyaccelerated flow field in order to develop and fine tune physical-mathematical models.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4991

Experimental and Numerical Investigation of Cavitation Regimes and Its Effects on Drag Characteristics of Wedge Shaped Bodies

2007 ◽  
Author(s):  
M. Osta ◽  
H. Mansouri ◽  
A. M. Razmi ◽  
M. A. Amini
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Unsteady Flow ◽  
Incompressible Flow ◽  
High Speed ◽  
Numerical Models ◽  
High Speed Camera ◽  
Cavitation Inception ◽  
Cavitation Phenomenon ◽  
Two Bodies

Cavitation phenomenon is defined as the process of rupturing any liquid by a decrease in pressure at nearly constant temperature. The cavities driven by the flow in a region of high pressure will implode and generate high pressure pulses leading eventually to erosion and vibration. But in supercavitation the bubbles produced by cavitation combine to form a large, stable bubble region around the supercavitating object. This phenomenon decreases the drag on the supercavitating body. Experimental testsware performed at 2-D unsteady flow for two wedge shaped bodies made before in laboratory and cavitation inception and its development were captured by a high speed camera. Then this cavitation regime around the wedge was studied numerically. In these cases CFD code was developed to simulate the unsteady and incompressible flow based on finite volume, 2D transient, with different boundary conditions. These numerical models which were evaluated experimentally depicted the capabilities of this CFD code to simulate this flow field cavitation inception, its development, and drag force in all cases. In this study we worked on two different geometries. Whether the cavitation is occurred at nose of body or not is worthy and studied by the above mentioned scheme. Moreover, we wanted to find the supercavitation regime and drag reduction for these two bodies.

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