Time-Resolved Spray-Droplet Velocity and Size Measurements via Single Camera Laser Sheet Imaging and Planar DPIV

2002 ◽  
Author(s):  
Michael R. Brady ◽  
Claude Abiven ◽  
Pavlos P. Vlachos ◽  
George Papadopoulos
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Imaging System ◽  
Laser Sheet ◽  
Sampling Rate ◽  
Direct Imaging ◽  
Entire Volume ◽  
Time Resolved ◽  
Direct Laser ◽  
Sheet Breakup

This paper describes a first effort to investigate the feasibility of droplet size and shape characterization by direct laser sheet imaging using time resolved Digital Particle Image Velocimetry. A 60-degree conical, high-pressure spray generated a poly-dispersed droplet distribution. Measurements were preformed for seven planes parallel to the spray axis, and separated by 4mm. A CMOS camera recorded the DPIV images at sampling rate of 10 KHz. Advanced image processing techniques were employed to identify the droplets and individually resolve their velocity using a hybrid cross-correlation particle-tracking algorithm. Subsequently, the size distribution of each droplet was quantified using geometric optics theory to convert the droplet image information to the true droplet size. Finally, the entire volume of the spray velocity and size distributions was reconstructed in a time-averaged sense. The droplet sizes from our direct imaging DPIV system were validated using a Phase Doppler Particle Analyzer (PDPA). The calculated sizes from the direct imaging methodology were found to agree with the measured PDPA results for droplets images larger than the diffraction limited diameter. Resolution limitations introduced inaccuracy for smaller droplets. In addition, the shedding frequency of the spray ligament was observed to be on the order of 1KHz, demonstrating the feasibility of using a high speed, direct imaging system in the characterization of unsteady, liquid sheet breakup properties. This preliminary effort illustrates the potential of performing global time resolved velocity and size measurements using a simple DPIV configuration based on CMOS imaging technology.

A New Type Laser Imaging System of Underwater Wake Bubbles

2014 ◽  
Vol 543-547 ◽  
pp. 2505-2508
Author(s):  
Xi Zhan Liu ◽  
Yan Bo Xue
Keyword(s):  
High Speed ◽  
Imaging System ◽  
Laser Sheet ◽  
High Speed Photography ◽  
Test Results ◽  
Laser Imaging ◽  
Technical Requirements ◽  
Wide Range ◽  
New Type ◽  
Wake Zone

Considering the difficulties in the wake bubbles imaging, a wake bubbles measurement system was presented based on the combination of high speed photography and laser sheet scanning technology. In this system, laser sheet was used to illuminate the wake zone to avoid the image stacking of bubbles. Because the particle size of bubbles was in a wide range (10~500um), three switchable magnification lenses were designed for the bubbles imaging. the test results show that the image quality is good and this system satisfies technical requirements.

scholarly journals Inspection of Large Droplets in Fuel Sprays Using a Gaussian Laser-Sheet: An Experimental Approach

ISRN Optics ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Rami Zakaria
Keyword(s):  
Light Scattering ◽  
Laser Beam ◽  
High Speed ◽  
Imaging System ◽  
Scattered Light ◽  
Laser Sheet ◽  
Injection System ◽  
High Temporal Resolution ◽  
Ic Engine ◽  
Fuel Sprays

A laser sheet imaging system was developed for the investigation of high-speed fuel sprays under a relatively low injection pressure (less than 1 MPa). A pulsed laser and high-resolution CCD cameras were used for the evaluation of the fuel injection system of a small IC engine. Large droplets were detected during the injection incident, with a variation in the scattered light pattern from one droplet to another. The light scattering pattern of individual droplets was investigated in order to study the interaction between the laser beam and large fluid droplets compared to the wavelength. A laser sheet, with a wide waist Gaussian profile, was used for illumination, so that the relative position of a droplet in the third dimension of the field of view (FOV) can be estimated from the 2D-image. Light scattering images were processed in order to closely investigate the structure of the fuel droplets, and the behaviour of the laser beam when encountering large droplets (0.2–1.4 mm). The Particle Image Velocimetry (PIV) method was applied on the double exposure spray images to calculate the droplet velocity distribution of the global spray, using a high temporal resolution (15 s).

Time-Resolved Step-Scan Infrared Imaging System Utilizing a Linear Array Detector

2008 ◽  
Vol 62 (1) ◽  
pp. 17-23 ◽  
Author(s):  
Hiroshi Sugiyama ◽  
Jun Koshoubu ◽  
Seiichi Kashiwabara ◽  
Toshiyuki Nagoshi ◽  
Richard A. Larsen ◽  
...  
Keyword(s):  
High Speed ◽  
Infrared Imaging ◽  
Linear Array ◽  
Single Channel ◽  
Imaging System ◽  
Piezo Actuator ◽  
Array Detector ◽  
Relaxation Dynamics ◽  
High Speed Imaging ◽  
Time Resolved

A time-resolved infrared (IR) imaging system combined with a multichannel IR microscope, which utilizes a 16 channel linear array (LA) detector, and step-scan Fourier transform infrared (FT-IR) microscope was developed. The LA detector integrates a readout circuit on each detector element, so the detected signals can be read simultaneously. Thus, this system can perform high speed imaging using the step-scan method, similar to a single channel detector. To verify the capabilities of this system, a reflective sample was examined whose position was altered using a piezo actuator activated by an alternating voltage. In addition, the localization of relaxation dynamics for the liquid crystal (LC) molecules in an LC cell under oscillating electric field conditions was detected by this system.

Multiple phase transitions investigated by high-speed TEM

1990 ◽  
Vol 48 (4) ◽  
pp. 550-551
Author(s):  
Oleg Bostanjoglo ◽  
Peter Thomsen-Schmidt
Keyword(s):  
Phase Transitions ◽  
High Speed ◽  
Short Exposure ◽  
Semiconductor Film ◽  
Time Resolved ◽  
Short Exposure Time ◽  
Multiple Phase ◽  
Model Substance ◽  
History Of ◽  
Electron Image

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)

scholarly journals Dual-shot dynamics and ultimate frequency of all-optical magnetic recording on GdFeCo

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Sicong Wang ◽  
Chen Wei ◽  
Yuanhua Feng ◽  
Hongkun Cao ◽  
Wenzhe Li ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Energy Efficient ◽  
High Speed ◽  
Data Transfer ◽  
Laser Pulses ◽  
Time Resolved ◽  
All Optical ◽  
Fs Laser ◽  
High Speed Data ◽  
Natural Way

AbstractAlthough photonics presents the fastest and most energy-efficient method of data transfer, magnetism still offers the cheapest and most natural way to store data. The ultrafast and energy-efficient optical control of magnetism is presently a missing technological link that prevents us from reaching the next evolution in information processing. The discovery of all-optical magnetization reversal in GdFeCo with the help of 100 fs laser pulses has further aroused intense interest in this compelling problem. Although the applicability of this approach to high-speed data processing depends vitally on the maximum repetition rate of the switching, the latter remains virtually unknown. Here we experimentally unveil the ultimate frequency of repetitive all-optical magnetization reversal through time-resolved studies of the dual-shot magnetization dynamics in Gd27Fe63.87Co9.13. Varying the intensities of the shots and the shot-to-shot separation, we reveal the conditions for ultrafast writing and the fastest possible restoration of magnetic bits. It is shown that although magnetic writing launched by the first shot is completed after 100 ps, a reliable rewriting of the bit by the second shot requires separating the shots by at least 300 ps. Using two shots partially overlapping in space and minimally separated by 300 ps, we demonstrate an approach for GHz magnetic writing that can be scaled down to sizes below the diffraction limit.

scholarly journals Acute Effects of Handheld Loading on Standing Broad Jump in Youth Athletes

2021 ◽  
Vol 18 (9) ◽  
pp. 5046
Author(s):  
Wei-Hsun Tai ◽  
Ray-Hsien Tang ◽  
Chen-Fu Huang ◽  
Shin-Liang Lo ◽  
Yu-Chi Sung ◽  
...  
Keyword(s):  
High Speed ◽  
Center Of Mass ◽  
Reaction Force ◽  
Sampling Rate ◽  
Random Order ◽  
Horizontal Distance ◽  
Acute Effects ◽  
Vertical Ground Reaction Force ◽  
Strength And Conditioning ◽  
Peak Knee

The study aimed to investigate the acute effects of handheld loading on standing broad jump (SBJ) performance and biomechanics. Fifteen youth male athletes (mean age: 14.7 ± 0.9 years; body mass: 59.3 ± 8.0 kg; height: 1.73 ± 0.07 m) volunteered to participate in the study. Participants were assigned to perform SBJ with and without 4 kg dumbbells in a random order. Kinematic and kinetic data were collected using 10 infrared high-speed motion-capture cameras at a 250 Hz sampling rate and two force platforms at a 1000 Hz sampling rate. A paired t-test was applied to all variables to determine the significance between loading and unloading SBJs. Horizontal distance (p < 0.001), take-off distance (p = 0.001), landing distance (p < 0.001), horizontal velocity of center of mass (CoM; p < 0.001), push time (p < 0.001), vertical impulse (p = 0.003), and peak horizontal and vertical ground reaction force (GRF; p < 0.001, p = 0.017) were significantly greater in loading SBJ than in unloading SBJ. The take-off vertical velocity of CoM (p = 0.001), take-off angle (p < 0.001), peak knee and hip velocity (p < 0.001, p = 0.007), peak ankle and hip moment (p = 0.006, p = 0.011), and peak hip power (p = 0.014) were significantly greater in unloading SBJ than in loading SBJ. Conclusions: Acute enhancement in SBJ performance was observed with handheld loading. The present findings contribute to the understanding of biomechanical differences in SBJ performance with handheld loading and are highly applicable to strength and conditioning training for athletes.

Sign in / Sign up

Export Citation Format

Share Document