The issue about the heat transfer enhancement in a 180-deg turned channel has attracted many attentions. The heat transfer capacity is influenced strongly by the behavior of the fluid flow. This work experimentally in...
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The issue about the heat transfer enhancement in a 180-deg turned channel has attracted many attentions. The heat transfer capacity is influenced strongly by the behavior of the fluid flow. This work experimentally investigated the fluid flow characteristics in a 180-deg round turned channel with discrete aluminum-foam blocks. The air was used as coolant. Several aluminum-foam blocks (0.90 porosity and 10 PPI pore density) were installed discretely in the 180-deg round turned channel with the square cross section. Four kinds of test section were employed to perform the flow visualizations. The results indicate that the arrangement of aluminum-foam blocks impacts on the flow pattern remarkably. The present results can be used to explain the pressure drop characteristics of such aluminum-foam channel, and be benchmarking by other investigators who would like to solve this problem numerically. (C) 2014 Elsevier Ltd. All rights reserved.
This work experimentally investigated the effects of jet flow and flow outlet configuration on the fluid flow in an annulus between co-axis rotating cylinders. By using the incense and the laser light, smoke flow visu...
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This work experimentally investigated the effects of jet flow and flow outlet configuration on the fluid flow in an annulus between co-axis rotating cylinders. By using the incense and the laser light, smoke flow visualization in a rotating annulus can be obtained. Firstly, the flow behavior in a rotating annular without jet flow and flow outlet was investigated. When Taylor number (Ta) exceeded 1708, the well-known Taylor vortices were successfully observed. Subsequently, the flow characteristics in a rotating annular with a jet flow and various flow outlet configurations were investigated. The circle jet nozzle was located at the middle position of the stationary outer cylinder. In addition, two flow outlet configurations were employed. One was the model of single outlet at the right side of the annulus, the other was the model of double outlets at both side of the annulus. The jet Reynolds number (Re) was 1351. The Taylor number (Ta) varied from 545 to 24,217. When the impinging force and the inertia force from the jet flow interacted with the Coriolis force and the centrifugal force due to rotation, the fluid flow should become very complicated. The experimental results indicated that the rapid rotation broke the original stream line of the jet flow. On the other hand, when the jet flow turned 90 degrees to be the axial flow, it would suppress the onset of Taylor vortices. Finally, fixing the Re and Ta, the model of single outlet more suppressed the onset of Taylor vortices than the model of double outlets did. (C) 2012 Elsevier Ltd. All rights reserved.
The unsteady low Reynolds number aerodynamics of flapping flight was investigated experimentally through flow visualization by suspended particle imagery and wall shear stress measurement from micro-array hot-film ane...
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The unsteady low Reynolds number aerodynamics of flapping flight was investigated experimentally through flow visualization by suspended particle imagery and wall shear stress measurement from micro-array hot-film anemometry. In conjunction, a mechanism was developed to create a flapping motion with three degrees of freedom and adjustable flapping frequency. The flapping kinematics and wing shape were selected for dynamic similarity to a hummingbird during hovering flight. flow visualization was used to validate the anemometry observations of leading edge vortex (LEV) characteristics and to investigate the necessity of spanwise flow in LEV stability. The shear sensors determined LEV characteristics throughout the translation section of the stroke period for various wing speeds. It was observed that a minimum frequency between 2 and 3.5 Hz is required for the formation and stabilization of a LEV. The vortex strength peaked around 30% of the flapping cycle (corresponding to just past the translation midpoint), which agrees with results from previous studies conducted by others. The shear sensors also indicated a mild growth in LEV size during translation sections of the wing's motion. This growth magnitude was nearly constant through a range of operating frequencies.
The present note describes a method for use in conjunction with a scanning electron microscope (SEM) that has been developed to visualize a liquid flow under a high-level vacuum and to measure a velocity field in a sm...
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The present note describes a method for use in conjunction with a scanning electron microscope (SEM) that has been developed to visualize a liquid flow under a high-level vacuum and to measure a velocity field in a small-scale flow through an open channel. In general, liquid cannot be observed via a SEM, because liquid evaporates under the high-vacuum environment of the SEM. As such, ionic liquid and room temperature molten salt having a vapor pressure of nearly zero is used in the present study. We use ionic liquid containing Au-coated tracer particles to visualize a small-scale flow under a SEM. Furthermore, the velocity distribution in the open channel is obtained by particle tracking velocimetry measurement and a parabolic profile is confirmed.
A flow visualization technique using dilute solutions of tobacco mosaic virus (TMV) is described. Rod-shaped TMV-particles align with shear, an effect that produces a luminous interference pattern when the TMV solutio...
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A flow visualization technique using dilute solutions of tobacco mosaic virus (TMV) is described. Rod-shaped TMV-particles align with shear, an effect that produces a luminous interference pattern when the TMV solution is viewed between crossed polarizers. Attractive features of this technique are that it is both transparent to the naked eye and benign to fish. We use it here to visualize the evolution and decay of the flows that they produce. We also report that dilute solutions of Kalliroscope are moderately birefringent and so may similarly be used for qualitative in situ flow visualizations.
Interest in flow visualization has constantly grown and experimental techniques have developed. The measurement of flow parameters is a wide field where we can distinguish purely geometrical parameters positioning of ...
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Interest in flow visualization has constantly grown and experimental techniques have developed. The measurement of flow parameters is a wide field where we can distinguish purely geometrical parameters positioning of a vortex or vibration amplitude of a shock wave, time and speed parameters such as velocity fields, and thermodynamic parameters such as pressure and temperature. The developing of Laser Induced Fluorescence has opened a new way in the measurement of thermodynamic parameters, coupled up with a velocimetry. The use of the light scattered by tracers in the crossing volume of 2 focused laser beams, Laser Doppler Velocimetry (LDV) has reached a high level of performance interm of speed range but also of rapidity, giving an easy access to the measurement of turbulence ratios. To better highlight the fluid dynamics inside a glass,laser tomography combined with fluorescent dyes has been used to give the vorticity convection, and once poured with champagne, the glass is lighted in its symmetry plane with a 1 mm planar laser sheet.
Stirred vessels are being used not only in chemical processes for simple contacting or blending operations, bur also in novel configurations and processes, as in mineral processing and/or wastewater treatment, with sp...
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Stirred vessels are being used not only in chemical processes for simple contacting or blending operations, bur also in novel configurations and processes, as in mineral processing and/or wastewater treatment, with specific requirements, like low shear or regions in the vessel with high and low turbulence levels. The techniques that are available for the study of the flow patterns induced by the various types of agitators, e.g., classical pressure or velocity measurements with Pitot tubes or hot-wire anemometers, and novel ones like laser Doppler velocimetry, laser-induced fluorescence and particle image velocimetry are reviewed and their usefulness for particular situations is discussed.
Using short-pulsed lasers to freeze the motion of small particles, imaging techniques can generate velocity and acceleration maps for a wide range of flowing systems.
Using short-pulsed lasers to freeze the motion of small particles, imaging techniques can generate velocity and acceleration maps for a wide range of flowing systems.
flow visualization has great potential in analyzing now patterns of centrifugal blood pumps to locate possible hemolysis and thrombus formation sites. This study focused on the said phenomena thought to correlate with...
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flow visualization has great potential in analyzing now patterns of centrifugal blood pumps to locate possible hemolysis and thrombus formation sites. This study focused on the said phenomena thought to correlate with areas of high shear velocity and stagnation and analyzed a new closed-type centrifugal blood pump. As a result of analyzing the flow of inlet and front gap of the impeller, flow in the front gap was approximately 30% of the external flow. visualization in the back gap showed sufficient exchange also. Analysis in the volute area and around the washout holes revealed high shear locations and quantified the highest shear velocity. Maximum shear on the volute wall was found to be 9,000-19,000 s(-1) and was located in the 0.2-mm vicinity of the wall. Based on these results, previous hemolysis tests, and small pump size, one concludes that the analyzed closed-type centrifugal pump has a relatively smooth flow suitable for a totally implantable artificial heart.
The work presented investigates the aerodynamic drag and flow physics of an airship configuration. The investigation is carried out experimentally in a water towing tank. The purpose of this project is to improve the ...
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The work presented investigates the aerodynamic drag and flow physics of an airship configuration. The investigation is carried out experimentally in a water towing tank. The purpose of this project is to improve the understanding of the aerodynamic characteristics of an airship through quantitative and qualitative approaches. Qualitative measurements of integral drag force and moment are measured in the presence of a crosswind. flow visualization using colored and fluorescent dyes has been applied to improve knowledge of the aerodynamics of airship configurations with an emphasis on the boundary layer separation, transition and hull-appendage interference effects. (C) 2009 Elsevier Masson SAS. All rights reserved.
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