Dynamic characteristics of laser-induced vapor bubble formation in water based on high speed camera

2013 ◽  
Author(s):  
Xian-zeng Zhang ◽  
Wenqing Guo ◽  
Zhenlin Zhan ◽  
Shusen Xie
Keyword(s):  
Dynamic Characteristics ◽  
Vapor Bubble ◽  
High Speed ◽  
Bubble Formation ◽  
High Speed Camera ◽  
Water Based

Laser-Induced Bubble Formation on a Micro Gold Particle Levitated Under Ultrasound

2016 ◽  
Author(s):  
Jaekyoon Oh ◽  
Yungpil Yoo ◽  
Samsun Seung ◽  
Ho-Young Kwak
Keyword(s):  
Resonance Frequency ◽  
Gold Particle ◽  
High Power ◽  
High Speed ◽  
Bubble Formation ◽  
Scattering Data ◽  
High Speed Camera ◽  
Scattered Intensity ◽  
High Power Laser ◽  
Power Laser

It is well known that a high-power laser could breakdown liquid [1, 2]. Laser-induced breakdown of liquids is characterized by fast plasma formation after evaporation of liquid and subsequent vapor expansion accompanied by shock wave emission [2]. The bubble wall velocity after the shock departure has been found to be sufficiently high to produce emission of light at the collapse point [3]. Recently, bubble formation on the surface of gold nanoparticles irradiated by a high-power laser in water [4, 5] has been studied for medical applications such as cancer diagnosis and possible therapy [5]. However, it is very hard to perform these experiments and to obtain good data from the bubble formation on the surface of laser-irradiated nano-particles because the nanoparticles dispersed in liquid cannot be controlled properly. In this study, laser-induced bubble formation on a micro gold particle levitated at the center of a spherical flask under ultrasound was investigated experimentally. The obtained results are compared with the results for laser cavitation without the gold particle, i.e., typical laser-induced cavitation. Figure 1 shows a schematic of the experimental setup used to investigate the laser-induced bubble formation on a micro gold particle. Two disk-type lead zirconate titanate (PZT) transducers (Channel Industries Inc.; 15 mm in diameter and 5.0 mm in thickness) attached to the side of the wall of the cell produced a velocity stagnation point near the center of the flask. The driving frequency of the PZT transducers was approximately 27.0 kHz which was close to the resonance frequency of the LRC circuit (Its capacitor unis is PZT.) and the acoustic resonance frequency of the water-filled flask. A drop of water containing gold particles with an average diameter of 10 μm are dispersed was injected into a 100-ml pyrex spherical flask filled with degassed water. When the body force of a gold particle in liquid is slightly lower than the Bjerknes force [6] induced by ultrasound, the particle will stay near the pressure antinode, i.e., the center of the flask. A Q-switched Nd:Yag laser delivered a single pulse of 0.5 ns in width with an energy of 7.5 mJ at a wavelength of 1064 nm to the gold particle or liquid at the center of the cell. The laser light was focused at the center of the flask using a lens with an effective focal length of 36.3 mm. Bubble formation and subsequent growth and collapse were visuallized by a high-speed camera (V2511, Phantom, USA) with 0.45 Mfps (million frames per second). The time-dependent radius was also obtained by the light scattering method. The scattering angle chosen was 80 degree where one-to-one relationship exists between the scattered intensity and the bubble radius [7]. The scattered intensity from a bubble illuminated by a 5-mW He-Ne laser was received by a photomultiplier tube (PMT: Hamamatsu, R2027) and was recorded in an oscilloscope. The scattering data were calibrated using the maximum radius for different bubble, which was obtained by high-speed camera. The shock strength during the expansion stage of bubbles was measured by a calibrated needle hydrophone (HPM1, Precision Acoustics, UK) at various distances from the center of the cell for different bubbles. The hydrophone can measure acoustic signals ranging from 1 kPa to 20 MPa. The hydrophone was attached to a three-dimensional micro stage so that fine control of the positioning of the hydrophone was possible.

Effect of Dual Frequency Ultrasound on the Bubble Formation in a Capillary Tube

2016 ◽  
Author(s):  
Benwei Fu ◽  
Nannan Zhao ◽  
Guoyou Wang ◽  
Hongbin Ma
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Capillary Tube ◽  
Bubble Formation ◽  
High Speed Camera ◽  
Dual Frequency ◽  
Heating Section ◽  
Nucleation Sites ◽  
Ultrasonic Sound ◽  
Frequency Ultrasound

A visual experimental was conducted to determine the effect of dual frequency ultrasound on the bubble formation and growth in a capillary quartz tube. The ultrasonic sound was applied to the heating section of a capillary tube by using electrically-controlled piezoelectric ceramics made of Pb-based lanthanum-doped zirconate titanates (PLZTs). The bubble formation and growth were recorded by a high speed camera. Experimental results show that the bubble formation and growth depend on PLZT frequency. When a dual frequency ultrasound (154 kHz and 474 kHz) was used, the nucleation sites for bubble formation were significantly increased and the bubble growth rate enhanced.

Whole Field Measurements to Understand the Role of Varying Depths of Nucleation Site on Vapor Bubble Dynamics and Heat Transfer Rates

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Surya Narayan L ◽  
Pasi Vijaykumar ◽  
Atul Srivastava
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Bubble Formation ◽  
Nucleation Site ◽  
Heat Transfer Process ◽  
Cavity Depth ◽  
Bulk Fluid ◽  
Transfer Rates ◽  
Transfer Processes

Abstract This work studies the possible effects of varying depths of cavity on bubbling features and the associated heat transfer rates in nucleate pool boiling regime. A single vapor bubble has been generated on a substrate with a cylindrical cavity at its center that acts as the nucleation site. Experiments have been conducted for three cavity depths (250, 500, and 1000 μm), while keeping its throat diameter constant at 200 μm. With the bulk fluid maintained under saturated conditions, for each cavity depth, surface superheat level has been varied in the range of ΔTsuperheat = 8, 10 and 12 °C. A gradient-based visualization technique, coupled with a high speed camera, has been employed to simultaneously map the changes in thermal gradients during the formation of the vapor bubble as well as bubble dynamic parameters. The image sequence obtained has been qualitatively and quantitatively analyzed to elucidate the dependence of bubbling features and various heat transfer processes on cavity depth. With an increase in the depth of cavity, the net effect of reduction in the available thermal energy due to the increased convection effects and significant depletion of superheated layer are identified as the dominant heat transfer processes that influence the bubbling features. Furthermore, based on the statistics of bubble departure characteristics, the cavity with higher depth (1000 μm) showed a much stable bubble formation with minimal variation in the bubble departure frequency as compared to the bubbling features from a cavity with smaller depth (250 μm). Evaporative heat transfer process has been identified as the primary cause for increased inconsistency of bubbling features at high superheat conditions for experiments performed for low cavity depths.

scholarly journals Tracking by Deblatting

2021 ◽  
Author(s):  
Denys Rozumnyi ◽  
Jan Kotera ◽  
Filip Šroubek ◽  
Jiří Matas
Keyword(s):  
High Speed ◽  
High Performance ◽  
Motion Blur ◽  
Velocity Estimation ◽  
High Speed Camera ◽  
Trajectory Function ◽  
Novel Approach ◽  
Blind Deblurring ◽  
Object Trajectories ◽  
Complex Trajectories

AbstractObjects moving at high speed along complex trajectories often appear in videos, especially videos of sports. Such objects travel a considerable distance during exposure time of a single frame, and therefore, their position in the frame is not well defined. They appear as semi-transparent streaks due to the motion blur and cannot be reliably tracked by general trackers. We propose a novel approach called Tracking by Deblatting based on the observation that motion blur is directly related to the intra-frame trajectory of an object. Blur is estimated by solving two intertwined inverse problems, blind deblurring and image matting, which we call deblatting. By postprocessing, non-causal Tracking by Deblatting estimates continuous, complete, and accurate object trajectories for the whole sequence. Tracked objects are precisely localized with higher temporal resolution than by conventional trackers. Energy minimization by dynamic programming is used to detect abrupt changes of motion, called bounces. High-order polynomials are then fitted to smooth trajectory segments between bounces. The output is a continuous trajectory function that assigns location for every real-valued time stamp from zero to the number of frames. The proposed algorithm was evaluated on a newly created dataset of videos from a high-speed camera using a novel Trajectory-IoU metric that generalizes the traditional Intersection over Union and measures the accuracy of the intra-frame trajectory. The proposed method outperforms the baselines both in recall and trajectory accuracy. Additionally, we show that from the trajectory function precise physical calculations are possible, such as radius, gravity, and sub-frame object velocity. Velocity estimation is compared to the high-speed camera measurements and radars. Results show high performance of the proposed method in terms of Trajectory-IoU, recall, and velocity estimation.

Influence of Main Swirler Vane Angle on the Ignition Performance of TeLESS-II Combustor

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Bo Wang ◽  
Chi Zhang ◽  
Yuzhen Lin ◽  
Xin Hui ◽  
Jibao Li
Keyword(s):  
High Speed ◽  
Inlet Temperature ◽  
Main Stage ◽  
Ignition Process ◽  
High Speed Camera ◽  
Fuel Distribution ◽  
Fuel Droplets ◽  
Planar Laser ◽  
Cfd Method ◽  
Vane Angle

In order to balance the low emission and wide stabilization for lean premixed prevaporized (LPP) combustion, the centrally staged layout is preferred in advanced aero-engine combustors. However, compared with the conventional combustor, it is more difficult for the centrally staged combustor to light up as the main stage air layer will prevent the pilot fuel droplets arriving at igniter tip. The goal of the present paper is to study the effect of the main stage air on the ignition of the centrally staged combustor. Two cases of the main swirler vane angle of the TeLESS-II combustor, 20 deg and 30 deg are researched. The ignition results at room inlet temperature and pressure show that the ignition performance of the 30 deg vane angle case is better than that of the 20 deg vane angle case. High-speed camera, planar laser induced fluorescence (PLIF), and computational fluids dynamics (CFD) are used to better understand the ignition results. The high-speed camera has recorded the ignition process, indicated that an initial kernel forms just adjacent the liner wall after the igniter is turned on, the kernel propagates along the radial direction to the combustor center and begins to grow into a big flame, and then it spreads to the exit of the pilot stage, and eventually stabilizes the flame. CFD of the cold flow field coupled with spray field is conducted. A verification of the CFD method has been applied with PLIF measurement, and the simulation results can qualitatively represent the experimental data in terms of fuel distribution. The CFD results show that the radial dimensions of the primary recirculation zone of the two cases are very similar, and the dominant cause of the different ignition results is the vapor distribution of the fuel. The concentration of kerosene vapor of the 30 deg vane angle case is much larger than that of the 20 deg vane angle case close to the igniter tip and along the propagation route of the kernel, therefore, the 30 deg vane angle case has a better ignition performance. For the consideration of the ignition performance, a larger main swirler vane angle of 30 deg is suggested for the better fuel distribution when designing a centrally staged combustor.

A modified damping model of vector form intrinsic finite element method for high-speed spiral bevel gear dynamic characteristics analysis

2021 ◽  
pp. 030932472110188
Author(s):  
Xiangying Hou ◽  
Yuzhe Zhang ◽  
Hong Zhang ◽  
Jian Zhang ◽  
Zhengminqing Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Numerical Solutions ◽  
Bevel Gear ◽  
Spiral Bevel Gear ◽  
Vector Form ◽  
Good Efficiency ◽  
Spiral Bevel ◽  
Damping Model

The vector form intrinsic finite element (VFIFE) method is springing up as a new numerical method in strong non-linear structural analysis for its good convergence, but has been constricted in static or transient analysis. To overwhelm its disadvantages, a new damping model was proposed: the value of damping force is proportional to relative velocity instead of absolute velocity, which could avoid inaccuracy in high-speed dynamic analysis. The accuracy and efficiency of the proposed method proved under low speed; dynamic characteristics and vibration rules have been verified under high speed. Simulation results showed that the modified VFIFE method could obtain numerical solutions with good efficiency and accuracy. Based on this modified method, high-speed vibration rules of spiral bevel gear pair under different loads have been concluded. The proposed method also provides a new way to solve high-speed rotor system dynamic problems.

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