Visualization of Macro- and Micromixing Using Two-Color Laser Induced Fluorescence and Particle Image Velocimetry

2006 ◽  
Author(s):  
M. Faes ◽  
D. Mewes
Keyword(s):  
Particle Image Velocimetry ◽  
Source Term ◽  
Particle Image ◽  
Optical Measurement ◽  
Laser Induced Fluorescence ◽  
Working Fluid ◽  
Simultaneous Application ◽  
Measurement Systems ◽  
Local Degree ◽  
Image Velocimetry

The progress in mixing on macro- and microscale is visualized by means of optical measurement systems. The Particle Image Velocimetry (PIV) is used to measure the velocity field inside the mixing system. The source term of the local energy dissipation is calculated by the information of the gradients of velocity. The Laser Induced Fluorescence (LIF) Technique is further developed for the simultaneous application of two different colors. A mixture of an inert and a reacting fluorescent dye is injected into a vessel. The macromixing is reflected by the inert dye serving as a tracer. Mixing on molecular scale is required for the progress of chemical reactions. Therefore the reacting dye indirectly visualizes the micromixing by changing its fluorescent characteristics during the reaction. The concentration fields of the two dyes are determined from measured fluorescence intensities. Based on these the local degree of deviation is calculated for detecting the areas of micromixing. Measurements are performed in a mixing system equipped with two glass cylinders. The working fluid is a mixture of glycerol and some adittional chemicals. The experiments are conducted in the laminar region. The injected dyes are stretched and folded in the flow field of the mixing system creating lamellar structures. The two optical measurement systems are prepared for the analysis of interrelation of macro- and micromixing subject to the local dissipation of energy.

A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

2000 ◽  
Vol 214 (5) ◽  
pp. 655-671 ◽  
Author(s):  
S C M Yu ◽  
J B Zhao
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Condition ◽  
Particle Image ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Flow Conditions ◽  
Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

Investigation of nitrogen-diluted syngas non-premixed flames measured by planar laser-induced fluorescence of hydroxyl and particle image velocimetry

2011 ◽  
Vol 225 (7) ◽  
pp. 1672-1680
Author(s):  
P Guo ◽  
S Zang ◽  
B Ge ◽  
Y Tian
Keyword(s):  
Carbon Monoxide ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Premixed Flames ◽  
Laser Induced Fluorescence ◽  
Experimental Results ◽  
Planar Laser Induced Fluorescence ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Recirculation Zones

In order to investigate the effects of nitrogen dilution on combustion behaviour of syngas flames, a model combustor with optical access for swirl non-premixed flames was developed. Experimental results from planar laser-induced fluorescence (PLIF) of OH and particle image velocimetry (PIV) are presented. The syngas consists of hydrogen and carbon monoxide of volume fraction ratio kept at 0.78. Up to 60 per cent (by volume) of nitrogen was added into syngas, as well as reference fuels including methane, hydrogen, and carbon monoxide, for dilution. Flow fields obtained by PIV reveal that the averaged typical swirling flow structure is not influenced by dilution content, which has more effect on turbulence intensities in recirculation zones and shear layers. Additionally, analysis of reaction zones and regions of burnt gas from OH-PLIF measurement shows that although syngas flame burns closer to fuel spray exit than methane, the latter shows more combustion stability, probably because of the different stabilization mechanisms for these two flames. With less support from hot burned gases in recirculation zones, the content of hydrogen plays a crucial role in syngas flame stabilization. Experimental results also imply that the increase of dilution content in fuel leads to less flame opening angle and thinner flame base.

Water Synthetic Jet Driven by a Piezoelectric Actuator – LIF and PIV Experiments

2015 ◽  
Vol 1104 ◽  
pp. 45-50 ◽  
Author(s):  
Zuzana Broučková ◽  
Shu Shen Hsu ◽  
An Bang Wang ◽  
Zdeněk Trávníček
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Piezoelectric Actuator ◽  
Particle Image ◽  
Three Dimensional ◽  
Laser Induced Fluorescence ◽  
Synthetic Jet ◽  
Fluid Exchange ◽  
Image Velocimetry ◽  
Surrounding Fluid

A synthetic jet (SJ) is a fluid jet flow generated from fluid oscillations during a periodical fluid exchange between an actuator cavity and surrounding fluid. A water synthetic jet was generated from submerged piezoelectric-driven SJ actuator. The actuator slot width was 0.36 mm. The experiments were performed using laser induced fluorescence (LIF) flow visualization and particle image velocimetry (PIV) techniques, both in a phase locked setup. The LIF visualization was used to demonstrate three-dimensional nature of the SJ formation process and to estimate SJ velocity. The PIV experiment quantified SJ velocity cycles in chosen plans. The driven frequency was adjusted near the resonance at approximately 46 Hz. It was evaluated theoretically and confirmed experimentally by means of LIF visualization. The time-mean orifice velocity and the Reynolds number were estimated asU0= 0.07–0.10 m/s andRe= 100–150, respectively.

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