Confined direct and reverse chemical gardens: Influence of local flow velocity on precipitation patterns

2020 ◽  
Vol 30 (1) ◽  
pp. 013140
Author(s):  
I. Ziemecka ◽  
F. Brau ◽  
A. De Wit
Keyword(s):  
Flow Velocity ◽  
Local Flow ◽  
Precipitation Patterns ◽  
Chemical Gardens ◽  
Local Flow Velocity

An electrochemical technique to measure local flow velocity in biofilms

1998 ◽  
Vol 32 (12) ◽  
pp. 3631-3636 ◽  
Author(s):  
Fuhu Xia ◽  
Haluk Beyenal ◽  
Zbigniew Lewandowski
Keyword(s):  
Flow Velocity ◽  
Electrochemical Technique ◽  
Local Flow ◽  
Local Flow Velocity

Local Flow Velocity Measurements Using an In-Fibre Bragg Grating Sensor

2010 ◽  
Vol 8 (4) ◽  
pp. 651-658 ◽  
Author(s):  
Christopher R. Dennison ◽  
Maxym V. Rukosuyev ◽  
Peter M. Wild ◽  
Peter M. Oshkai ◽  
David A. Singlehurst ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Velocity Measurements ◽  
Local Flow ◽  
Fibre Bragg Grating Sensor ◽  
Bragg Grating Sensor ◽  
Local Flow Velocity

Unsteady critical liquid sheet flows

2017 ◽  
Vol 821 ◽  
pp. 219-247 ◽  
Author(s):  
M. Girfoglio ◽  
F. De Rosa ◽  
G. Coppola ◽  
L. de Luca
Keyword(s):  
Flow Velocity ◽  
Weber Number ◽  
Liquid Sheet ◽  
Global Dynamics ◽  
Equivalent Stiffness ◽  
Supercritical Regime ◽  
Local Flow ◽  
System Perspective ◽  
Linear Approach ◽  
Small Disturbances

The unsteady global dynamics of a gravitational liquid sheet interacting with a one-sided adjacent air enclosure (commonly referred to as nappe oscillation configuration) is addressed under the assumptions of potential flow and the presence of surface tension effects. From a theoretical viewpoint the problem is challenging, because from previous literature it is known that the equation governing the evolution of small disturbances exhibits a singularity at the vertical station where the local flow velocity equals the capillary wave velocity (local critical condition), although the solution to the problem has not yet been found. The equation governing the local dynamics resembles one featuring the forced vibrations of a string of finite length, formulated in the reference frame moving with the flow velocity, and exhibits both slow and fast characteristic curves. From the global system perspective the nappe behaves as a driven damped spring–mass oscillator, where the inertial effects are linked to the liquid sheet mass and the spring is represented by the equivalent stiffness of the air enclosure acting on the displacement of the compliant nappe centreline. A suited procedure is developed to remove the singularity of the integro-differential operator for Weber numbers less than unity. The investigation is carried out by means of a modal (i.e. time asymptotic) linear approach, which is corroborated by numerical simulations of the governing equation and supported by systematic comparisons with experimental data from the literature, available in the supercritical regime only. As regards the critical regime for the unit Weber number, the major theoretical result is a sharp increase in oscillation frequency as the flow Weber number is gradually reduced from supercritical to subcritical values due to the shift of the prevailing mode from the slow one to the fast one.

High Resolution Particle Image Velocimetry and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
C. W. Foley ◽  
I. Chterev ◽  
J. Seitzman ◽  
T. Lieuwen
Keyword(s):  
Particle Image Velocimetry ◽  
High Resolution ◽  
Shear Layer ◽  
Flow Velocity ◽  
Particle Image ◽  
Flame Stabilization ◽  
Flow Conditions ◽  
Local Flow ◽  
Image Velocimetry ◽  
Flow Velocities

Understanding the mechanisms and physics of flame stabilization and blowoff of premixed flames is critical toward the design of high velocity combustion devices. In the high bulk flow velocity situation typical of practical combustors, the flame anchors in shear layers where the local flow velocities are much lower. Within the shear layer, fluid strain deformation rates are very high and the flame can be subjected to significant stretch levels. The main goal of this work was to characterize the flow and stretch conditions that a premixed flame experiences in a practical combustor geometry and to compare these values to calculated extinction values. High resolution, simultaneous particle image velocimetry (PIV) and planar laser induced fluorescence of CH radicals (CH-PLIF) measurements are used to capture the flame edge and near-field stabilization region. When approaching lean limit extinction conditions, we note characteristic changes in the stretch and flow conditions experienced by the flame. Most notably, the flame becomes less critically stretched when fuel/air ratio is decreased. However, at these lean conditions, the flame is subject to higher mean flow velocities at the edge, suggesting less favorable flow conditions are present at the attachment point of the flame as blowoff is approached. These measurements suggest that blowoff of the flame from the shear layer is not directly stretch extinction induced, but rather the result of an imbalance between the speed of the flame edge and local tangential flow velocity.

Structural Analysis of Selected Failures Caused by the 27 February 2010 Chile Tsunami

2012 ◽  
Vol 28 (1_suppl1) ◽  
pp. 215-243 ◽  
Author(s):  
Ian Robertson ◽  
Gary Chock ◽  
Juan Morla
Keyword(s):  
Flow Velocity ◽  
Structural Performance ◽  
Structural Element ◽  
Local Flow ◽  
Inundation Depth ◽  
Hydrodynamic Loading ◽  
Tsunami Damage ◽  
Chile Earthquake ◽  
Chile Tsunami ◽  
Loading Estimates

Following the 2010 Chile earthquake and tsunami, the authors participated in the EERI reconnaissance team that traveled to Chile to document damage and structural performance. The authors focused on tsunami damage following the earthquake. A summary of tsunami damage to structures is given. Based on a series of well-defined structural element failures at sites where inundation depth was measured, the team was able to evaluate the hydrodynamic loading required to cause these failures and derive estimated lower bound flow velocity overland during the event. It was estimated that the velocity exceeded 3.2 m/s in Talcahuano harbor and 4.3 m/s in the coastal town of Dichato. When found in proximity to damaged buildings and other larger structures of interest, these simple structures can serve as “flow surrogate instruments” to estimate the local flow velocity. Failure analysis of these simple structures indicated that the hydrodynamic loading estimates provided by FEMA P646 may be unconservative.

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