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flow visualization STUDIES FOR OPTIMIZATION OF THE GROWTH OF TIN BY PACVD

SURFACE & COATINGS TECHNOLOGY 1995年第1-3期74-5卷 516-521页

作者： CRUMMENAUER, J STOCK, HR MAYR, P Stiftung Institut f&uuml r Werkstofftechnik Badgasteiner Strasse 3 D-28359 Bremen Germany

Gas flow visualization studies were performed in a vertical plasma-assisted chemical vapour depostion (PACVD) reactor. The flow patterns were made visible by illuminating TiO2 particles generated by the reaction of TiCl4 and H2O in the gas flow. The gas was injected through four different distribution systems. The deposition of TiN by a PACVD process was performed in a pulsed d.c. glow discharge at a total pressure of 250 Pa and a substrate temperature of 500 degrees C. flow visualization experiments and depositions were carried out under similar flow conditions, in particular the same Reynolds number. The streamline patterns were used to interpret the deposition rate and chemical composition across the surface of the deposited TiN layer. The thickness and uniformity of the deposited films were determined. It can be demonstrated that well designed gas distribution systems enable uniform deposition of coatings on cutting tools with complex geometry.

关键词： PACVD TITANIUM NITRIDE flow visualization GAS INJECTION GAS DISTRIBUTION

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flow visualization in bubbly two-phase hydraulic jump

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JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME 1998年第1期120卷 160-165页

作者： Mossa, M Tolve, U Acque Politecn Bari Dipartimento Ingn I-70125 Bari Italy Tecnopolis CSATA Novus Ortus I-70010 Valenzano Bari Italy

The present study investigates bubbly two-phase flow in a hydraulic jump using a flow visualization technique. Bubbly two-phase flow is encountered in many engineering problems;however, mainly because of experimental difficulties, little is known opt the internal structure of these flows, although such knowledge is clearly essential to a thorough understanding of the mass transfer between the two component phases. In the past, same authors measured the distribution of void ratio in a hydraulic jump using hot-film anemometry. Nowadays this interesting technique may be improved using a flow visualization technique, which enables one to obtain the percentage of air across each vertical section of the jump. This is possible by evaluating the gray levels of the first principal axes of transformed images starting from RCB images. The experiments considered the phenomenon of air concentration in a hydraulic jump, which was studied and analyzed using image processing techniques, aimed at obtaining reliable quantitative measurements. To achieve this, the processing system was planned and tested at the hardware level and a procedure for managing rifle processing was set up, The calibration curve was obtained using the McCorquodale and Khalifa law (1983). The results permit the visualization of flow structures and the estimation of air concentration of the flow along all the jump and to show the position in which the air concentration reaches the maximum value versus time.

关键词： Calibration Mass transfer Hardware Image processing flow (Dynamics) visualization Hydraulic jump flow visualization Two-phase flow

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flow visualization study to improve hemocompatibility of a centrifugal blood pump

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ARTIFICIAL ORGANS 1999年第8期23卷 697-703页

作者： Nishida, M Asztalos, B Yamane, T Masuzawa, T Tsukiya, T Endo, S Taenaka, Y Miyazoe, Y Ito, K Konishi, Y Mech Engn Lab Biomimet Div Tsukuba Ibaraki 3058564 Japan Ibaraki Univ Ibaraki Osaka Japan Natl Cardiovasc Ctr Osaka Japan Nikkiso Co Ltd Tokyo Japan

A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the flow in the volute and in the outlet. flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry, In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position;however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 mu m) than the standard model (-80 mu m). In the small radial gap model, the high shear layer in the outlet (-50 mu m) is much narrower than that in the volute. flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

关键词： flow visualization volute flow impeller/casing gap outlet position outlet flow shear velocity

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flow visualization during multiple-axis motions using a wind-driven manipulator

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JOURNAL OF AIRCRAFT 1996年第1期33卷 163-170页

作者： Magill, JC Darden, LA Komerath, NM Georgia Institute of Technology Atlanta Georgia 30332-0150

This article explores the problem of capturing vortex flow interactions that occur during coupled-axis maneuvers at finite rates. A wind-driven dynamic manipulator (WDM) has been developed to perform simultaneous motions repetitively about two degrees of freedom under open-loop or feedback control in a low-speed wind tunnel. The concept of the WDM is examined and support interference is shown to be small compared to that in conventional approaches to maneuver simulation. Vortex flow interactions occurring near the vertical fins of a 1/32-scale fighter configuration during pitch, yaw, and coupled pitch-yaw motions are explored using quantitative laser sheet videography. Large asymmetry and complex interactions are observed in the flowfield. Vortices generated by the forebody, wing leading edge, wingtip, and vertical fins are seen to interact during the coupled pitch-yaw maneuver, Maneuvers are limited to reduced frequencies below 0.036, based on wingspan. Vortex locations are seen to be accurately reproducible and to be independent of rate as expected in this regime. Even at such low rates, several transient interaction phenomena are observed, involving vortices and control surfaces. Quantification of such phenomena is demonstrated.

关键词： Flexible Manipulators flow visualization Vortex Breakdown Control Surfaces Closed Loop Control Low Speed Wind Tunnel Leading Edges Feedback Circuits Interactional Aerodynamics Angle of Attack

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flow visualization by mobile phone cameras

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EXPERIMENTS IN FLUIDS 2016年第6期57卷 1-10页

作者： Cierpka, Christian Hain, Rainer Buchmann, Nicolas A. Bundeswehr Univ Munich Inst Fluid Mech & Aerodynam Werner Heisenberg Weg 39 D-85577 Neubiberg Germany Von Stauffenberg Str D-82008 Unterhaching Germany

Mobile smart phones were completely changing people's communication within the last ten years. However, these devices do not only offer communication through different channels but also devices and applications for fun and recreation. In this respect, mobile phone cameras include now relatively fast (up to 240 Hz) cameras to capture high-speed videos of sport events or other fast processes. The article therefore explores the possibility to make use of this development and the wide spread availability of these cameras in the terms of velocity measurements for industrial or technical applications and fluid dynamics education in high schools and at universities. The requirements for a simplistic PIV (particle image velocimetry) system are discussed. A model experiment of a free water jet was used to prove the concept and shed some light on the achievable quality and determine bottle necks by comparing the results obtained with a mobile phone camera with data taken by a high-speed camera suited for scientific experiments.

关键词： flow visualization PARTICLE image velocimetry FLUID dynamics CAMERA phones EXTERNAL flows (Fluid mechanics)

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flow visualization experiment in a two-side wall heated rectangular duct for turbulence model assessment in natural convection heat transfer

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NUCLEAR ENGINEERING AND DESIGN 2019年第Jan.期341卷 284-296页

作者： Kim, Sin-Yeob Shin, Dong-Ho Kim, Chan-Soo Park, Goon-Cherl Cho, Hyoung Kyu Seoul Natl Univ Dept Energy Syst Engn 1 Gwanak Ro Seoul South Korea Korea Atom Energy Res Inst Nucl Hydrogen Reactor Technol Div 111 Daedeok Daero 989 Beon Gil Daejeon South Korea

Reactor Cavity Cooling System (RCCS) is one of the passive safety systems in Very High Temperature gas-cooled Reactor (VHTR). RCCS incorporates riser channels connected with a chimney to remove the residual heat emitted from the reactor vessel using natural circulation, and therefore, heat transfer phenomena in the RCCS riser duct is of great importance to ensure the safety of the VHTR. To enhance the understanding of heat transfer mechanism in a heated riser duct with rectangular shape, visualization of the local flow structure was conducted with an experimental facility for the natural convection heat transfer applying the Particle Image Velocimetry (PIV) method. With measured thermal boundary conditions by IR thermometry, CFD analysis was performed for the test facility using two different turbulence models. By comparing local flow structure from the experimental data and CFD calculation results, turbulence model assessment was conducted to confirm the prediction capability of the models. Experimental data show the magnitudes and locations of maximum velocity peak which is induced by buoyancy force and the anisotropic behaviors of velocity fluctuations near wall region. CFD calculations overestimate the maximum velocity near the wall compared with experimental data, and they seem to have limitations in reproducing the secondary flow observed at the corner of the test section in the experiment. The established methodology for flow visualization and the measurement strategy for thermal boundary conditions could contribute to obtain extensive experimental data and turbulence model assessment results, which would improve the understanding of the heat transfer mechanism to enhance the performance prediction capability for the passive heat removal system of the VHTR.

关键词： VHTR RCCS riser Convective heat transfer flow visualization Local flow structure Buoyancy effect

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flow visualization AND HEAT-TRANSFER EXPERIMENTS IN A DUCT WITH A STAGGERED ARRAY OF CYLINDERS

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 1989年第2期2卷 193-200页

作者： YAO, M NAKATANI, M SUZUKI, K Department of Mechanical Engineering Nara National College of Technology Nara Japan Department of Mechanical Engineering Kyoto University Kyoto Japan

flow visualization and heat transfer measurements were made for flow between parallel plates with an insertion of a staggered array of cylinders. The Reynolds number ranged from 8000 to 60,000. The channel height was 50 mm, and the cylinder diameter was 10 mm. The streamwise cylinder pitch was kept constant at five times the cylinder diameter, but the space between the cylinder and the duct wall was changed in four step increments. The measured distribution of local Nusselt number was found to be similar in shape regardless of the Reynolds number. The heat transfer results are discussed in terms of the results of flow visualization. The flow visualization study was made at a Reynolds number of 8500, corresponding to the lowest bound of the Reynolds number range chosen in the heat transfer experiments. A high-speed camera was used to examine the unsteady behavior of the flow. One of the results obtained is that heat transfer is enhanced mainly due to the effect of intermittent reattachment of discrete vortices formed in the separation shear layer starting from the cylinder surface.

关键词： flow visualization duct flow forced convection flow obstacles

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flow visualization study at the interface of alternating pitch tube bundles in a model helical coil steam generator using particle image velocimetry

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2018年 122卷 614-628页

作者： Delgado, M. Lee, S. Hassan, Y. A. Anand, N. K. Texas A&M Univ Dept Nucl Engn College Stn TX 77843 USA Texas A&M Univ Dept Mech Engn College Stn TX 77843 USA

A simplified Helical Coil Steam Generator (HCSG) model was constructed to study the flow on the shell side of rod bundles that coil against one another, using a 12-degree single rod bundle interface. The test section maintained a transverse pitch-to-diameter ratio of 2.98 while lateral pitch-to-diameter ratio constantly changed. To resolve optical distortions, experiments used para-cymene to match the refractive index of the test section. Three equally spaced regions of interest along the length of the model each have unique lateral rod pitch ratios. Experiments focused to capture the flow fields at each section between the adjacent coils at Reynolds number of 9,000. Particle image velocimetry is used for velocity measurements. The flow velocity in both the stream-wise (y-axis) and transverse (x-axis) directions for each plane, vorticity and streamline plots, used Reynolds Stresses for u'u', v'v' and u'v' for different geometric coordinates are presented. The wake and center streamline regions between the rod bundles demonstrate the complex flow structures and interactions between local adjacent rods that the changing geometry of the helical coil steam generator produces throughout its configuration. Previous studies on straight tube heat exchanger models identify the formation of vortices behind rods that form dependent on an in-line or staggered tube bundle reliant on the pitch ratios. Averaged flow visualization data for the tested model HCSG suggest that flow characteristics follow their relative location to bundle formations instead of pitch-ratio. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： PIV flow visualization Helical coil steam generator Tube and shell heat exchanger

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flow visualization, PIV measurement and CFD calculation for fluid-driven natural cross-ventilation in a scale model

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ENERGY AND BUILDINGS 2013年第Nov.期66卷 306-314页

作者： Bangalee, M. Z. I. Miau, J. J. Lin, S. Y. Yang, J. H. Univ Dhaka Dept Math Dhaka 1000 Bangladesh Natl Cheng Kung Univ Dept Aeronaut & Astronaut Tainan 70101 Taiwan Natl Cheng Kung Univ Res Ctr Energy Technol & Strategy Tainan 70101 Taiwan

A building that is equipped with a natural ventilation system gives greater physical comfort for its occupants and saves on electricity consumption. The flow structure of fluid-driven natural cross-ventilation is studied using three techniques: flow visualization, Particle Image Velocimetry (PIV) measurement and Computational Fluid Dynamics (CFD). Four specific cases are chosen to study the effect of the number of windows and the window configuration on cross-ventilation performance. A comparative discussion of these cases is provided and the significant advantages and disadvantages for each case, with regard to ventilation, are reported. There is satisfactory agreement between the results obtained from computation and those from the experiment, which provides an effective guideline for CFD users for the validation of future numerical approaches. A novel numerical technique is used to provide an insight into the quantification of the movement of entering air. The three dimensionality, turbulence and the replacement of the indoor fluid are visualized. The overall performance is significantly affected by the specific design of the cross-ventilation system. It is found that a larger volumetric flow rate does not always ensure better replacement of the indoor air, and vice versa. (C) 2013 Elsevier B.V. All rights reserved.

关键词： flow visualization PIV measurement CFD Natural cross ventilation Turbulence

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flow visualization and measurement on the roof of the Texas Tech building

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 1997年第0期71卷 597-606页

作者： Sarkar, PP Zhao, ZS Mehta, KC Texas Tech Univ Dept Civil Engn Lubbock TX 79409 USA

flow visualization and flow measurement on the roof of the Texas Tech Building are performed in this study. It mainly explores visualization techniques applied to full scale and discusses the results of how measurements within the separation bubble. The shape of the separation bubble along one axis of the building has been characterized by an intermittency factor. Preliminary observations of the dynamics of the separation bubble are made based upon visualization records.

关键词： flow visualization flow measurement full-scale experiment low building Texas Tech building separation bubble delta-wing vortex

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