Femtosecond Desorption Dynamics Probed by Time-Resolved Velocity Measurements

1995 ◽  
Vol 75 (4) ◽  
pp. 673-676 ◽  
Author(s):  
D. G. Busch ◽  
Shiwu Gao ◽  
R. A. Pelak ◽  
M. F. Booth ◽  
W. Ho
Keyword(s):  
Velocity Measurements ◽  
Time Resolved

Time-Resolved Velocity Measurements in a Matched Refractive Index Facility of Randomly Packed Spheres

2018 ◽  
Author(s):  
Ethan Kappes ◽  
Mateusz Marciniak ◽  
Andrew Mills ◽  
Robert Muyshondt ◽  
Stephen King ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Index Of Refraction ◽  
Mean Square ◽  
Reynolds Stresses ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Time Resolved ◽  
Wall Boundary

Complex geometries and randomly connected void spaces within packed beds have hindered efforts to characterize the underlying transport phenomena occurring within. In this communication, we present our experimental studies on a facility of randomly packed spheres that can be a representative of sections within a reactor core in a nuclear power plant. The results of high-fidelity velocity measurements can be seen using Time-Resolved Particle Image Velocimetry (TR-PIV) at the pore scales and near the wall boundary in the Matched Index of Refraction (MIR) facility. The MIR approach allows for a non-invasive analysis of the flow within packed spheres at the microscopic scales with high temporal and spatial resolution. Flow characteristics obtained from the TR-PIV measurements at various Reynolds numbers are presented. The results include the first- and second-order flow statistics, such as mean velocity, root-mean-square fluctuating velocity and Reynolds stresses. Effects of the wall boundary and Reynolds numbers on flow patterns are currently being investigated. Comparisons of the mean velocities, root-mean-square fluctuating velocities, and Reynolds stress components show the increase of flow mixing and turbulent intensities within the gaps between spheres in the packed bed. Sizes of recirculation regions, however, seem to be independent of the increase of Reynolds numbers.

Improvements to the Dynamic Range of Velocity Measurements Using DPIV

2006 ◽  
Author(s):  
John J. Charonko ◽  
Pavlos P. Vlachos
Keyword(s):  
High Speed ◽  
Dynamic Range ◽  
Total Error ◽  
Window Size ◽  
Laser Pulses ◽  
Velocity Measurements ◽  
Low Velocity ◽  
Displacement Fields ◽  
Correlation Peak ◽  
Time Resolved

The accurate measurement of velocity fields containing large dynamic ranges is important because many problems of interest feature regions of both very high and low velocity. Examples include mixing tanks, jets injected into quiescent chambers, and stagnation regions behind bodies in high speed flow. However, accurate calculation of the velocity is currently limited to displacements greater than the total error of the scheme used (typically in the range of 0.01 to 0.05 pixels) and less than one-quarter of the window size. To counteract this difficulty, two new methods for improving the dynamic range of DPIV calculations have been developed. The first can be used with any double-pulsed time-resolved DPIV system where closely spaced frame pairs are captured at kilohertz rates. Displacement measurements can be made both within each frame pair (resolving high velocity regions), and between successive pairs (resolving low velocity regions). The two displacement fields are then reconciled, resulting in a single flow field measurement. The second method uses multiple laser pulses per camera exposure. Four laser pulses are required per measurement (two per camera frame), however, unlike the first method, kilohertz repetitions rates are not required. By carefully selecting the intervals between pulses, it is possible to associate the each cross-correlation peak with the correct delay time, and thereby simultaneously obtain velocity measurements over a much wider dynamic range. These two methods have been applied to synthetic and experimental data and their performance has been characterized through error analysis. Results indicate that both methods can increase the dynamic range by one to two orders of magnitude as compared to traditional techniques, while retaining similar total error and spatial resolution characteristics.

Soap bubbles seeding for quantitative time resolved velocity measurements of a turbulent wake flow behind a cylinder

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Amine Koched ◽  
Giuseppe Serra ◽  
Giampaolo Romano ◽  
Carsten Kyal ◽  
Jean Stefanini
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Air Flow ◽  
Wake Flow ◽  
Laser Source ◽  
Soap Bubble ◽  
Velocity Measurements ◽  
Time Resolved ◽  
Soap Bubbles ◽  
Open Test

The wake flow behind a cylinder of 100mm diameter is investigated using time resolved 2D PIV technique applied to an air flow generated in a closed loop open test section wind tunnel. The flow is seeded using a micro soap bubble generator (BG-1000, TSI Inc.). The bubbles in the air flow were illuminated with a CW laser source and imaged using a high-speed camera. The main purpose of this study is to show features and advantages of using soap bubbles as seeding for a relatively large-scale PIV investigation under low power illumination conditions.

Time-resolved velocity measurements in a magnetic micromixer

2015 ◽  
Vol 67 ◽  
pp. 6-13 ◽  
Author(s):  
F. Gökhan Ergin ◽  
Bo B. Watz ◽  
Kaspars Ērglis ◽  
Andrejs Cēbers
Keyword(s):  
Velocity Measurements ◽  
Time Resolved

Time-resolved ion velocity measurements in a high-power Hall thruster using laser-induced fluorescence with transfer function averaging

2020 ◽  
Vol 116 (23) ◽  
pp. 234107 ◽  
Author(s):  
V. H. Chaplin ◽  
R. B. Lobbia ◽  
A. Lopez Ortega ◽  
I. G. Mikellides ◽  
R. R. Hofer ◽  
...  
Keyword(s):  
Transfer Function ◽  
High Power ◽  
Laser Induced Fluorescence ◽  
Hall Thruster ◽  
Velocity Measurements ◽  
Time Resolved ◽  
Ion Velocity

Simultaneous three-dimensional temperature and velocity field measurements using astigmatic imaging of non-encapsulated thermo-liquid crystal (TLC) particles

Lab on a Chip ◽  
2015 ◽  
Vol 15 (3) ◽  
pp. 660-663 ◽  
Author(s):  
Rodrigo Segura ◽  
Massimiliano Rossi ◽  
Christian Cierpka ◽  
Christian J. Kähler
Keyword(s):  
Liquid Crystal ◽  
Velocity Field ◽  
Three Dimensional ◽  
Field Measurements ◽  
Velocity Measurements ◽  
Time Resolved

TLC thermography and APTV for simultaneous time-resolved 3D temperature and velocity measurements in microflows.

scholarly journals Shock pressure and free surface velocity measurements in confined interaction — Response of new VF2/VF3 piezoelectric gauges

1996 ◽  
Vol 14 (2) ◽  
pp. 171-179 ◽  
Author(s):  
M. Boustie ◽  
S. Couturier ◽  
J.P. Romain ◽  
D. Zagouri ◽  
H. Simonnet
Keyword(s):  
Free Surface ◽  
Polyvinylidene Fluoride ◽  
Peak Pressure ◽  
Surface Velocity ◽  
Shock Propagation ◽  
Laser Irradiance ◽  
Free Surface Velocity ◽  
Velocity Measurements ◽  
Incident Intensity ◽  
Time Resolved

To determine the peak pressure induced versus the incident intensity of a neodymium (Nd) glass pulsed laser, with a duration of 25 ns in glass confined geometry, two methods have been comparatively used. Free surface velocity measurements have been performed using an electromagnetic gauge. The results are compared with pressure measurements realized at the back of irradiated aluminum targets with the use of polyvinylidene fluoride (PVDF) gauges. Both diagnostics provide consistent results. The measurements of peak pressure as a function of laser irradiance are used to determine the calibration curve (current density versus loading pressure) for new VF2/VF3 copolymer shock gauges used in this lasermatter interaction configuration. These experimental set-up deliver time resolved measurements that are interpreted by the shock-propagation phenomena.

Chirped pulse interferometry for time resolved density and velocity measurements of laser produced plasmas

2011 ◽  
Vol 110 (2) ◽  
pp. 023305 ◽  
Author(s):  
Y. B. S. R. Prasad ◽  
S. Barnwal ◽  
P. A. Naik ◽  
J. A. Chakera ◽  
P. D. Gupta
Keyword(s):  
Velocity Measurements ◽  
Time Resolved ◽  
Chirped Pulse
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