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Academic literature on the topic 'Smoke Flow Visualization'

Author: Grafiati

Published: 4 June 2021

Last updated: 7 September 2023

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Journal articles on the topic "Smoke Flow Visualization"

1

Raval, D., S. V. Jain, A. M. Acharii, and K. Ghosh. "Design and analysis of smoke flow visualization apparatus for wind tunnel." IOP Conference Series: Materials Science and Engineering 1206, no. 1 (November 1, 2021): 012014. http://dx.doi.org/10.1088/1757-899x/1206/1/012014.

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Abstract In the present study, the design and analysis of smoke generator are done for the low-speed wind tunnel. The wind tunnel fan is fitted with the Variable Frequency Drive to produce the wind speed in the range of 3 to 32 m/s with fan speed of 150 to 1500 rpm. The design of smoke generator was done according to Preston Sweeting mist generator principle corresponding to the free stream velocity of 3 m/s. A controlled smoke generator consisting of kerosene reservoir, controlled heater, blower, liquid column height adjustment mechanism, valves etc. was designed and fabricated. The smoke generator produced the smoke at the rate of 154 cm3/s which was close to the design flow rate of 149 cm3/s. To supply the required quantity of smoke in the wind tunnel, the smoke rake of NACA 0010 profile was developed and installed in the rapid contraction section of the wind tunnel to achieve the streamlined flow. The parametric studies were done on the smoke generator at different power inputs and its effects were studied on smoke temperature, smoke discharge and boiling time of the kerosene. The flow visualization was carried out on NACA 0015 airfoil model and the images were captured to examine the flow physics around them under different operating conditions.

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2

Miller, L. S., and E. Irani. "Simple method of supersonic flow visualization using smoke." AIAA Journal 30, no. 1 (January 1992): 278–79. http://dx.doi.org/10.2514/3.10913.

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3

Balachander, Aakash, Akash Alase, K. Adithya Menon, G. Mahendra Perumal, and B. T. Kannan. "Smoke based visualization of turbulent swirl jet flow." IOP Conference Series: Materials Science and Engineering 912 (September 12, 2020): 022011. http://dx.doi.org/10.1088/1757-899x/912/2/022011.

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4

Yuan, Zhi, Ye Zhao, Fan Chen, Sean Reber, Cheng-Chang Lu, and Yang Chen. "Detail-preserving compression for smoke-based flow visualization." Journal of Visualization 22, no. 1 (November 19, 2018): 51–64. http://dx.doi.org/10.1007/s12650-018-0526-y.

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5

Goodfellow, S. D., S. Yarusevych, and P. E. Sullivan. "Smoke-wire flow visualization of a synthetic jet." Journal of Visualization 16, no. 1 (December 18, 2012): 9–12. http://dx.doi.org/10.1007/s12650-012-0155-9.

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6

Forney, G. P., D. Madrzykowski, K. B. McGrattan, and L. Sheppard. "Understanding fire and smoke flow through modeling and visualization." IEEE Computer Graphics and Applications 23, no. 4 (July 2003): 6–13. http://dx.doi.org/10.1109/mcg.2003.1210858.

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7

Koca, Kemal, Mustafa Serdar Genç, and Halil Hakan Açıkel. "Experimental investigation on effect of partial flexibility at low aspect ratio airfoil - Part II: Installation both on suction and pressure surface." EPJ Web of Conferences 269 (2022): 01028. http://dx.doi.org/10.1051/epjconf/202226901028.

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In this experimental study, flow over NACA 4412 airfoil with flexible membrane mounted both on suction surface and pressure surface was investigated at Reynolds number of 5x104 and different angles of attack. The smoke-wire visualization method was used for flow visualization to demonstrate flow phenomena as laminar separation bubble (LSB), leading edge separation and tip vortices. A constant temperature anemometer (CTA) was used for measuring flow over the partially flexible airfoil. Concerning the flow visualization, smoke-wire experiment was been conducted at z/c=0.1 and z/c=0.4. Besides, hot-wire experiment by means of CTA was employed to measure flow properties including values of velocity, turbulence statistics and Reynold stress over both uncontrolled and controlled airfoil. The results showed that partially flexible airfoil had several benefits compared with the uncontrolled airfoil. The results for this partially flexible airfoil were mainly lower size of LSB, higher stall angle of attack, ensuring more stable flow characteristics and more aerodynamic performance.

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8

Ristic, Slavica. "A - a view in the invisible." Theoretical and Applied Mechanics 40, no. 1 (2013): 87–119. http://dx.doi.org/10.2298/tam1301087r.

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Flow visualization is an important topic in, experimental and computational fluid dynamics and has been the subject of research for many years. This paper presents an overview of flow visualization techniques. The physical basis and applications of different visualization methods for subsonic, transonic and supersonic flow in wind and water tunnels are described: direct injection methods, (smoke, dye, fog and different small particles), gas and hydrogen bubbles, , flow visualization by tufts, oil, liquid crystals, pressure and temperature sensitive paints, shadow, schlieren, interferometry, Laser Doppler Anemometry, Particle Image Velocimetry and other special techniques. Almost all presented photos have been recorded during tests in laboratories of MTI Belgrade.

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9

Lee, Sang-Joon, and Sang-Hyun Lee. "SYNCHRONIZED SMOKE-WIRE TECHNIQUE FOR FLOW VISUALIZATION OF TURBULENT FLOWS." Journal of Flow Visualization and Image Processing 6, no. 1 (1999): 65–78. http://dx.doi.org/10.1615/jflowvisimageproc.v6.i1.60.

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10

SETA, SHIGEYUKI, ZIN SUGAWARA, MITURU YABUSHITA, YOSHIO HARA, TOSHIHIRO OKA, and MACHIKA URABE. "EXPERIMENTS OF FLOW VISUALIZATION IN CLEAN ROOM BY CIGARETTE SMOKE." JOURNAL OF THE FLOW VISUALIZATION SOCIETY OF JAPAN 7, Supplement (1987): 93–96. http://dx.doi.org/10.3154/jvs1981.7.supplement_93.

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Dissertations / Theses on the topic "Smoke Flow Visualization"

1

Szarko, David James. "Smoke-wire visualization of an oscillating flow in a gas spring." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/38727.

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2

Sipes, Jordan. "Streamsurface Smoke Effect for Visualizing Dragon Fly CFD Data in Modern OpenGL with an Emphasis on High Performance." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1369083905.

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3

Caletka, Petr. "Posouzení funkčnosti různých modifikací větrací vyústky pro kabinu osobního vozu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254454.

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This master thesis deals with determination of boundaries of the flow from a benchmark automotive vent (right-front situated – in front of a front passenger) using the smoke visualization. In this thesis is tested a pack of eight different constructional variants which differ among them by the type of deflection grille. The angles of the flow borders are compared to specific directional requirements (defined by ŠKODA AUTO a.s.) and there is evaluated a directability of each of the constructional variant on the bases of these results. The results of experiments show that better directability in vertical plane achieve deflection grilles with horizontal vanes situated closer to orifice of the vent or deflection grilles with higher number of horizontal vanes and lower number of vertical vanes (independently of their location). Directability of the deflection grilles in horizontal plane is analogically better with vertical vanes situated closer to orifice of the vent or with deflection grilles with higher number of vertical vanes and lower number of horizontal vanes (independently of their location).

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4

Molčan, Filip. "Vliv omezujících stěn na proudění z ventilační vyústky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378274.

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The goal of this work is to experimentally assess the influence of limiting walls of Škoda Octavia 3 automobile cabin to the air jet flowing from the right-front situated automotive vent which is part of a car dashboard. The experiment is performed by the smoke visualization method. There is a single construction option measured for an experiment. The setup of the vanes direction and the air flow rate are modified for this option. The experiment is divided into two phases. In the first phase, the visualization of the free air flow is conducted. In the second phase, exit plates are constructed and consequently, the visualization of the wall-jet flow is conducted. The results of both are compared to each other. The results imply that the influence of the surrounding surfaces must be taken into account with the increasing flow rate for the vanes set in the direction of upper-right, middle-right, and middle-middle. There is a direct interaction between the flow and exit plates (the flow impact, the Coanda effect). The free flow does not contain the information about the mutual interaction between the flow and the exit plates, as it is in the case of the wall-jet flow. In the case of the wall-jet flow, the opening of the flow takes place due to the effect of the impact and the subsequential suction caused by the Coanda effect. The exit plates substituting the car dashboard and the front window contribute to the prevention of the air intake from surrounding space and consequently to earlier flow opening from the vent. The present work also contains the measurement methodology and the image evaluation, the comparison with previous free flow measurements (70% match) and the comparison to the measurement of hot-wire anemometry method.

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5

Bečica, Radek. "Vizualizace proudu z větrací vyústky pro přístrojovou desku osobního vozu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230826.

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Goal of this master´s thesis is to experimentally analyse air jet from ventilation outlet of a passenger car dashboard using smoke visualization and to describe this air jet. Air flow was set at 30 m3/h according to requirements from Škoda Auto s.r.o. from previous experiments on a similar ventilation outlet. First type of measuring rig which was developed for previous experiments was disassembled and replaced with a new modern measuring rig which is supposed to be used for next visualizations and experiments. Visualization was performed using smoke method and laser light plane. Air jet was photographed for five defined ventilation outlet adjustments and that for a jet to free space and for a jet flowing along a wall. The wall represented a front left door of a car. Results were processed by computer and presented as pictures and tables. Resulting angles were transformed to the main coordinate system of a car. Ventilation outlet functionality with respect to the air distribution in a car was evaluated afterwards.

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6

Yang, chun-sheng, and 楊淳盛. "Visualization Experiment of Smoke Flow for Longitudinally Ventilated Tunnel Fires." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/37298429432520530120.

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碩士
國立屏東科技大學
車輛工程系所
95
In the events of tunnel fires, it is essential to extract smoke out of the tunnel by means of ventilation devices installed in the tunnel to ensure a safe evacuation route for the tunnel users trapped in the tunnel. Otherwise, the casualties and damages caused by the tunnel fire are often too difficult and painful to estimate. For uni-traffic long vehicular tunnels, researchers and designers are more interested in estimating the critical ventilation velocity. Unlike conventional assumption, the velocity profile of the longitudinally ventilated air flow induced by the actual jet fans in the tunnel is actually different from the uniform velocity profile employed for empirical correlations proposed in the literature. In this study, a reduced scale model tunnel of 1:20 was built in which small jet fans were installed at the ceiling of the model tunnel. The length of the tunnel is 5.3 m. Two fans were tied together to form a pair of jet fan set. The distance between each pair is 1 m. The smoke flow is simulated using heated liquid paraffin. Five different locations were used as smoke inlet to simulate the fire source. To serve the purpose of flow visualization, a part of the tunnel wall was constructed using a piece of transparent glass. Result of current experimental study shows that the influences of the upstream and downstream fan sets on the smoke flow were different. To form an ideal distribution of smoke flow in the tunnel, in additional to closing the fan sets near the fire source, the velocity of the upstream fans should be smaller than that of the downstream fans. Doing so can not only remove smoke from the tunnel, but also provide a safe evacuation route for the tunnel users.

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7

Lin, C. L., and 林志隆. "Smoke-wire flow visualization of the wake of a unconfined circular disk with and without centrally flushing jet." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/86961395508768057392.

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碩士
國立臺灣科技大學
工程技術研究所
81
The smoke-wire technique was used for visualization of the recirculation zone over axisymmetric, unconfined, and mounted bluff-body with or without central jet flow. Three patterns with no central flushing jet, inversed-Ω, open contour, and closed contour, are specified by whether the contour separating from the edge of disk is inversed into the recirculation zone. If the central flushing jet are introduced, five regions, pre- pentration, transition, pentration, un-inversed flow, and in- versed-Ω, are identified. In each pattern and region, the dynamics structures are described and measured. The vortex shedding from disk also studied in the ranges of Reynolds number 0 < Rea <1000 and 0 < Rec <1000, and the shedding patterns are specified as inversed-Ω, expelling, and shear- layer vortex shedding. The results, Lr/Lr0 and Jc/Ja for the recirculation, St and Jc/Ja for vortex shedding, and Z/Lr and r/ Wmax for the position of separation line, are correlated. It appears that momentum ratio Jc/Ja plays a important role over the variation of the dynamic structures of the recirculation zone.

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8

Suhas, Diwan Sourabh. "Dynamics Of Early Stages Of Transition In A Laminar Separation Bubble." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/679.

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This is an experimental and theoretical study of a laminar separation bubble and the associated transition dynamics in its early stages. The separation of a laminar boundary layer from a solid surface is prevalent in very many flow situations such as over gas turbine blades (especially in the low-pressure turbine stage) and the wings of micro-aero-vehicles (MAVs) that operate at fairly low Reynolds numbers. Flow separation occurs in such cases due to the presence of an adverse pressure gradient. The separated shear layer becomes unstable due to the presence of an inflection point and presumably transitions to turbulence rapidly. Eventually, there is reattachment back to the solid surface further downstream, if conditions are right. The region enclosed by the shear layer is called a laminar separation bubble and has been a subject of many studies in the past. The present experiments have been conducted in a closed-circuit wind tunnel. A separation bubble was obtained on the upper surface of a flat plate by appropriately contouring the top wall of the tunnel. Four different techniques were used for qualitative and quantitative study viz. surface flow visualisation, smoke flow visualisation, surface pressure measurements and hotwire anemometry. Response of the bubble to both natural as well as artificial (impulsive excitation) disturbance environment has been studied. Linear stability analyses (both Orr-Sommerfeld and Rayleigh calculations), in the spatial framework, have been performed for the mean velocity profiles starting from an attached adverse pressure gradient boundary layer all the way up to the front portion of the separation bubble region (i.e. up to the end of the dead-air region where linear evolution of disturbances could be expected). The measured velocity profiles (both attached and separated) were fitted with analytical model profiles for doing stability calculations. A separation bubble consists of aspects of both wall-bounded and wall-free shear layers and therefore both viscous and inviscid mechanisms are expected to be at play. Most of the studies in the literature point to the inviscid instability associated with the shear layer to be the main mechanism. The main aim of the present work is to understand the exact origin of the primary instability mechanism responsible for the amplification of disturbances. We argue that at least up to the front portion of the bubble, the instability mechanism is due to the inflectional mode associated with the mean velocity profile. However, the seeds of this inviscid inflectional instability could be traced back to the attached boundary layer upstream of separation. In other words, the inviscid inflectional instability of the separated shear layer should be logically seen as an extension of the instability of the upstream attached adverse-pressure-gradient boundary layer. This modifies the traditional view that pegs the origin of the instability in a separation bubble to the free shear layer outside the bubble with its associated Kelvin-Helmholtz mechanism. Our contention is that only when the separated shear layer has moved considerably away from the wall (and this happens near the maximum height of the mean bubble) that a description by Kelvin-Helmholtz instability paradigm with its associated scaling principles could become relevant. We also propose a new scaling for the most amplified frequency for a wall-bounded shear layer in terms of the inflection point height and the vorticity thickness, and show its universality. Next, we theoretically investigate the role played by the re-circulating region of the separation bubble in the linear instability regime. In the re-circulating region near the wall, associated with the so-called wall mode, the production of disturbance kinetic energy is found to be negative. This is a very interesting observation which has been cursorily noted in earlier studies. Here we show that the near-wall negative production region exerts a stabilising influence on the downstream travelling disturbances. A theoretical support for such a mechanism to exist close to the wall is presented. It is shown that the stabilising wall-proximity effect is not a peripheral aspect but has a significant effect on the overall stability especially for the waves close to the upper neutral branch. We demonstrate the appropriateness of inviscid analysis for the stability of the separated flow velocity profile away from the wall, by comparing the numerical solutions of Rayleigh and Orr-Sommerfeld equations. Following this, the analytical consequences of the Rayleigh equation such as the inflection point criterion and the Fjortoft criterion are derived for the wall-bounded inflectional velocity profiles. Furthermore, we also discuss the relevance of the negative production region towards flow control and management for the wall-bounded flows. It appears fruitful to divide the separation bubble region into two parts with respect to the nature of disturbance dynamics: one outside the mean dividing streamline (which behaves as an amplifier) and the other inside the bubble corresponding to the re-circulating region (having oscillator type characteristics). To explore the oscillator-like behaviour of the bubble further, we have carried out spatio-temporal stability analysis of the reversed flow velocity profiles and determined the conditions for the onset of absolute instability. We contend that the presence of the negative production region for the upstream travelling waves has a restraining effect arresting the tendency of the flow (both wall-free and wall-bounded) to become absolutely unstable and thereby requiring a particular threshold of the backflow velocity to be crossed for its realisation. Moreover, the delay in the onset of absolute instability for a wall-bounded profile as compared to a free shear layer is attributed to a certain ‘negative-drag’ effect of the wall on the overall flow which increases the group velocities for the wall-bounded flows. A related theme in the literature regarding the dynamics of laminar separation bubbles is the so-called ‘bursting’ of the bubble wherein there is a sudden increase in the length and height of the bubble as some critical conditions are reached. Bubbles before bursting are termed as ‘short’ bubbles and those after bursting as ‘long’ bubbles. In this work, we provide a criterion to predict bursting which is a refinement over the existing criteria. The proposed criterion takes into account not just the length of the bubble but also the maximum height and it is shown to be more universal in differentiating short bubbles from the long ones, as compared to the other criteria. We also present a hypothesis regarding the sequence of events leading to bubble bursting by relating its onset to the instability of the re-circulating region. For this we observe that as the amount of backflow velocity is increased for a reversed flow velocity profile, the inflection point moves inside the mean dividing streamline and this happens before the onset of absolute instability. This causes a vorticity maximum to develop inside the re-circulating region which could lead to the instability of the closed streamlines with respect to two-dimensional cylindrical disturbances. The actual bursting process may be expected to involve non-linear interactions of the disturbances and the long bubble could be a nonlinearly saturated state of the instability of the re-circulating region. In order to explore the three-dimensionality associated with the bubble, extensive surface flow visualisation experiments have been performed. The surface streamline pattern is obtained for the entire span of the plate for three different freestream velocities. The patterns have been interpreted using topological ideas and various critical points have been identified. It is shown that the arrangement of critical points satisfies the ‘index theorem’ which is a topological necessity and the streamline patterns are ‘structurally stable’. An interesting observation from these patterns is the presence of three-dimensionality upstream of the separation line close to the wall even though the oncoming flow is nominally two-dimensional. Using the critical point theory, we propose a hypothesis which could be used to construct a semi-empirical model wherein the critical points are assigned with a quantity called ‘strength’ for determining the extent of upstream influence of a given separation line. Finally, we derive a necessary condition for the existence of inviscid spatial instability in plane parallel flows. It states that for spatial instability the curvature of the velocity profile should be positive in some region of the profile. This includes Rayleigh’s inflection point theorem (which was proposed and proved by Rayleigh for temporal instability) as a special case. It thus provides a rigorous basis for applying the inflection point criterion to the flows in the framework of spatial stability theory (which we have used extensively in the present thesis). Moreover, the condition derived here is more general as it also includes velocity profiles with the curvature positive everywhere which are excluded by Rayleigh’s theorem in the temporal framework. An example of such a profile is presented (Couette-Poiseuille flow with adverse pressure gradient) and it is shown that this flow is an exceptional case which is temporally stable but spatially unstable. Eigenvalue calculations as well as energy considerations suggest that the mechanism governing instability of this flow is inviscid and non-inflectional in character. This is a new result which could have important implications in understanding the instability dynamics of parallel flows.

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9

Suhas, Diwan Sourabh. "Dynamics Of Early Stages Of Transition In A Laminar Separation Bubble." Thesis, 2009. http://hdl.handle.net/2005/679.

Full text

Abstract:

This is an experimental and theoretical study of a laminar separation bubble and the associated transition dynamics in its early stages. The separation of a laminar boundary layer from a solid surface is prevalent in very many flow situations such as over gas turbine blades (especially in the low-pressure turbine stage) and the wings of micro-aero-vehicles (MAVs) that operate at fairly low Reynolds numbers. Flow separation occurs in such cases due to the presence of an adverse pressure gradient. The separated shear layer becomes unstable due to the presence of an inflection point and presumably transitions to turbulence rapidly. Eventually, there is reattachment back to the solid surface further downstream, if conditions are right. The region enclosed by the shear layer is called a laminar separation bubble and has been a subject of many studies in the past. The present experiments have been conducted in a closed-circuit wind tunnel. A separation bubble was obtained on the upper surface of a flat plate by appropriately contouring the top wall of the tunnel. Four different techniques were used for qualitative and quantitative study viz. surface flow visualisation, smoke flow visualisation, surface pressure measurements and hotwire anemometry. Response of the bubble to both natural as well as artificial (impulsive excitation) disturbance environment has been studied. Linear stability analyses (both Orr-Sommerfeld and Rayleigh calculations), in the spatial framework, have been performed for the mean velocity profiles starting from an attached adverse pressure gradient boundary layer all the way up to the front portion of the separation bubble region (i.e. up to the end of the dead-air region where linear evolution of disturbances could be expected). The measured velocity profiles (both attached and separated) were fitted with analytical model profiles for doing stability calculations. A separation bubble consists of aspects of both wall-bounded and wall-free shear layers and therefore both viscous and inviscid mechanisms are expected to be at play. Most of the studies in the literature point to the inviscid instability associated with the shear layer to be the main mechanism. The main aim of the present work is to understand the exact origin of the primary instability mechanism responsible for the amplification of disturbances. We argue that at least up to the front portion of the bubble, the instability mechanism is due to the inflectional mode associated with the mean velocity profile. However, the seeds of this inviscid inflectional instability could be traced back to the attached boundary layer upstream of separation. In other words, the inviscid inflectional instability of the separated shear layer should be logically seen as an extension of the instability of the upstream attached adverse-pressure-gradient boundary layer. This modifies the traditional view that pegs the origin of the instability in a separation bubble to the free shear layer outside the bubble with its associated Kelvin-Helmholtz mechanism. Our contention is that only when the separated shear layer has moved considerably away from the wall (and this happens near the maximum height of the mean bubble) that a description by Kelvin-Helmholtz instability paradigm with its associated scaling principles could become relevant. We also propose a new scaling for the most amplified frequency for a wall-bounded shear layer in terms of the inflection point height and the vorticity thickness, and show its universality. Next, we theoretically investigate the role played by the re-circulating region of the separation bubble in the linear instability regime. In the re-circulating region near the wall, associated with the so-called wall mode, the production of disturbance kinetic energy is found to be negative. This is a very interesting observation which has been cursorily noted in earlier studies. Here we show that the near-wall negative production region exerts a stabilising influence on the downstream travelling disturbances. A theoretical support for such a mechanism to exist close to the wall is presented. It is shown that the stabilising wall-proximity effect is not a peripheral aspect but has a significant effect on the overall stability especially for the waves close to the upper neutral branch. We demonstrate the appropriateness of inviscid analysis for the stability of the separated flow velocity profile away from the wall, by comparing the numerical solutions of Rayleigh and Orr-Sommerfeld equations. Following this, the analytical consequences of the Rayleigh equation such as the inflection point criterion and the Fjortoft criterion are derived for the wall-bounded inflectional velocity profiles. Furthermore, we also discuss the relevance of the negative production region towards flow control and management for the wall-bounded flows. It appears fruitful to divide the separation bubble region into two parts with respect to the nature of disturbance dynamics: one outside the mean dividing streamline (which behaves as an amplifier) and the other inside the bubble corresponding to the re-circulating region (having oscillator type characteristics). To explore the oscillator-like behaviour of the bubble further, we have carried out spatio-temporal stability analysis of the reversed flow velocity profiles and determined the conditions for the onset of absolute instability. We contend that the presence of the negative production region for the upstream travelling waves has a restraining effect arresting the tendency of the flow (both wall-free and wall-bounded) to become absolutely unstable and thereby requiring a particular threshold of the backflow velocity to be crossed for its realisation. Moreover, the delay in the onset of absolute instability for a wall-bounded profile as compared to a free shear layer is attributed to a certain ‘negative-drag’ effect of the wall on the overall flow which increases the group velocities for the wall-bounded flows. A related theme in the literature regarding the dynamics of laminar separation bubbles is the so-called ‘bursting’ of the bubble wherein there is a sudden increase in the length and height of the bubble as some critical conditions are reached. Bubbles before bursting are termed as ‘short’ bubbles and those after bursting as ‘long’ bubbles. In this work, we provide a criterion to predict bursting which is a refinement over the existing criteria. The proposed criterion takes into account not just the length of the bubble but also the maximum height and it is shown to be more universal in differentiating short bubbles from the long ones, as compared to the other criteria. We also present a hypothesis regarding the sequence of events leading to bubble bursting by relating its onset to the instability of the re-circulating region. For this we observe that as the amount of backflow velocity is increased for a reversed flow velocity profile, the inflection point moves inside the mean dividing streamline and this happens before the onset of absolute instability. This causes a vorticity maximum to develop inside the re-circulating region which could lead to the instability of the closed streamlines with respect to two-dimensional cylindrical disturbances. The actual bursting process may be expected to involve non-linear interactions of the disturbances and the long bubble could be a nonlinearly saturated state of the instability of the re-circulating region. In order to explore the three-dimensionality associated with the bubble, extensive surface flow visualisation experiments have been performed. The surface streamline pattern is obtained for the entire span of the plate for three different freestream velocities. The patterns have been interpreted using topological ideas and various critical points have been identified. It is shown that the arrangement of critical points satisfies the ‘index theorem’ which is a topological necessity and the streamline patterns are ‘structurally stable’. An interesting observation from these patterns is the presence of three-dimensionality upstream of the separation line close to the wall even though the oncoming flow is nominally two-dimensional. Using the critical point theory, we propose a hypothesis which could be used to construct a semi-empirical model wherein the critical points are assigned with a quantity called ‘strength’ for determining the extent of upstream influence of a given separation line. Finally, we derive a necessary condition for the existence of inviscid spatial instability in plane parallel flows. It states that for spatial instability the curvature of the velocity profile should be positive in some region of the profile. This includes Rayleigh’s inflection point theorem (which was proposed and proved by Rayleigh for temporal instability) as a special case. It thus provides a rigorous basis for applying the inflection point criterion to the flows in the framework of spatial stability theory (which we have used extensively in the present thesis). Moreover, the condition derived here is more general as it also includes velocity profiles with the curvature positive everywhere which are excluded by Rayleigh’s theorem in the temporal framework. An example of such a profile is presented (Couette-Poiseuille flow with adverse pressure gradient) and it is shown that this flow is an exceptional case which is temporally stable but spatially unstable. Eigenvalue calculations as well as energy considerations suggest that the mechanism governing instability of this flow is inviscid and non-inflectional in character. This is a new result which could have important implications in understanding the instability dynamics of parallel flows.

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Books on the topic "Smoke Flow Visualization"

1

Ward, Donald T. Flight validation of a pulsed smoke flow visualization system. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Facility, 1993.

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2

Ward, Donald T. Flight validation of a pulsed smoke flow visualization system. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Facility, 1993.

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3

Facility, Dryden Flight Research, ed. Preliminary design of an intermittent smoke flow visualization system. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Facility, 1993.

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4

Ward, Donald T. Preliminary design of an intermittent smoke flow visualization system. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Facility, 1993.

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Ward, Donald T. Flight validation of a pulsed smoke flow visualization system: Final report submitted to the NASA Ames-Dryden Flight Research Facility, Edwards, CA. [Washington, DC: National Aeronautics and Space Administration, 1993.

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Richwine, David M. A smoke generator system for aerodynamic flight research. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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E, Curry Robert, Tracy Gene V, and United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., eds. A smoke generator system for aerodynamic flight research. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Flight validation of a pulsed smoke flow visualization system: Final report submitted to the NASA Ames-Dryden Flight Research Facility, Edwards, CA. [Washington, DC: National Aeronautics and Space Administration, 1993.

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Book chapters on the topic "Smoke Flow Visualization"

1

Pawar, Amit Ashok, Kumar Sanat Ranjan, Arnab Roy, and Sandeep Saha. "Investigation of Flowfield Over a Dart Using Smoke Flow Visualization." In Lecture Notes in Mechanical Engineering, 99–103. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-7055-9_17.

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Rajesh Kumar, S., Kaavya Ramachandran, and B. T. Kannan. "Smoke-Based Visualization of Jet Flow from a Cruciform Nozzle of Unit Aspect Ratio." In Lecture Notes in Mechanical Engineering, 29–36. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1388-4_3.

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Lim, T. T. "DYE AND SMOKE VISUALIZATION." In Flow Visualization, 43–72. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2000. http://dx.doi.org/10.1142/9781848160361_0003.

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Lim, T. T. "DYE AND SMOKE VISUALIZATION." In Flow Visualization, 47–78. IMPERIAL COLLEGE PRESS, 2012. http://dx.doi.org/10.1142/9781848167926_0003.

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Crowder, James P. "Smoke Flow Visualization in Large Wind Tunnels and Flight Testing Using the Flying-Strut Traverser." In Handbook of Flow Visualization, 409–15. Routledge, 2018. http://dx.doi.org/10.1201/9780203752876-26.

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Mueller, Thomas J. "Gases: Smokes." In Handbook of Flow Visualization, 47–65. Routledge, 2018. http://dx.doi.org/10.1201/9780203752876-5.

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Conference papers on the topic "Smoke Flow Visualization"

1

WARD, D., S. BRANDT, and J. MYATT. "Preliminary design of an intermittent smoke flow visualization system." In Aerospace Design Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-1028.

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STEINHOFF, J., and T. MERSCH. "Flow field measurement and visualization using projected smoke trails." In 30th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-384.

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Yarusevych, Serhiy, Pierre Sullivan, and John Kawall. "Smoke-Wire Flow Visualization on an Airfoil at Low Reynolds Numbers." In 38th Fluid Dynamics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-3958.

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Fumizawa, Motoo, Shuhei Ohkawa, Isaku Buma, and Suguru Tanaka. "Visualization and Numerical Simulation of Exchange Flow in Density Different Gases." In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-55107.

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Buoyancy-driven exchange flows of helium-air through inclined a narrow tube was investigated. Exchange flows may occur following the opening of a window for ventilation, as well as when a pipe ruptures in a high temperature gas-cooled reactor. The experiment in this paper was carried out in a test chamber filled with helium and the flow was visualized using the smoke wire method. A high-speed camera recorded the flow behavior. The image of the flow was transferred to digital data, and the slow flow velocity, i.e. micro flow rate was measured by PIV software. Numerical simulation was carried out by the code of moving particle method with Lagrange method.

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5

Shoe, Bridget, Peter J. Disimile, Eric Savory, Norman Toy, and Bahman Tahouri. "Image analysis of two impinging jets using laser-induced fluorescence and smoke flow visualization." In Munich '91 (Lasers '91), edited by Hatem N. Nasr. SPIE, 1991. http://dx.doi.org/10.1117/12.46060.

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Wang, Hai-Ping, Steven J. Olson, Richard J. Goldstein, and Ernst R. G. Eckert. "Flow Visualization in a Linear Turbine Cascade of High Performance Turbine Blades." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-007.

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Multiple smoke wires are used to investigate the secondary flow near the endwall of a plane cascade with blade shapes as used in high performance turbine stages. The wires are positioned parallel to the endwall and ahead of the cascade, within and outside the endwall boundary layer. The traces of the smoke generated by the wires are visualized within a laser light sheet arranged at various cross-sections around the cascade. During the experiment, a periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade. A series of photographs and video tapes was taken in the cascade to trace these vortices. The development and evolution of the horseshoe vortex and the passage vortex are clearly resolved in the photographs. The interaction between the suction side leg of the horseshoe vortex and the passage vortex is also observed in the experiment. A vortex induced by the passage vortex, starting about 1/4 of the curvilinear distance along the blade on the suction surface, is clearly shown in the photographs. This vortex stays close to the suction surface and above the passage vortex in the laminar flow region on the blade. From this flow visualization, a model describing the secondary flows in a cascade is proposed and compared with previous published models. Some naphthalene mass transfer results from a blade near an endwall are cited and compared with the current model. The flows inferred from both techniques agree well with each other.

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Yocum, Adam M., and Walter F. O’Brien. "Separated Flow in a Low Speed Two-Dimensional Cascade: Part I — Flow Visualization and Time-Mean Velocity Measurements." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-356.

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This study was conducted for the purpose of providing a more fundamental understanding of separated flow in cascades and to provide performance data for fully-stalled blade rows. Cascades of a single blade geometry and a solidity of unity were studied for three stagger angles and the full range of angle of attack, extending well into the stalled flow regime. Results are presented from flow visualization and time-mean velocity measurements of stalled flow in the cascade. Surface and smoke flow visualization revealed that the blade stagger angle is a key parameter in determining the location of the separation line and the occurrence of propagating stall. Time-mean velocity measurements obtained with a dual hot split-film probe also showed that the separated velocity profiles within the blade passages and the profiles in the wake have distinctly different characteristics depending on the stagger angle.

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Gutie´rrez-Torres, C. del C., R. Tolentino-Eslava, and J. A. Jime´nez-Bernal. "Experimental Visualization in a Cyclone Separation System." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98203.

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Cyclones are one of the most used equipment for gas cleaning. These devices are widely used because of their simple construction, low energy requirements and their ability to work with high temperature and pressure levels. In this work, a flow visualization of a cyclone separation system is carried out. For that purpose, smoke particles and a laser beam were used to show the flow patterns within the separation system. The objective of this work is to visualize the flow within a cyclone separation system to elucidate the effect of the flow patterns in the gas-particle separation and the optimization of the cyclone.

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Haiping, Chang, Zhang Jingyu, Huang Taiping, and Zhang Dalin. "Flow Visualization of a Jet Impinging on a Ribbed Surface With Crossflow." In ASME 1996 Turbo Asia Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-ta-003.

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The flow behavior of a jet impinging on a ribbed surface has an obvious effect on the impingement heat transfer. It has been observed experimentally in a special smoke wind tunnel with rectangular section. This is an interesting problem in the impingement cooling midchord region of the gas turbine aerofoils with ribbed surface, and also in the electronic component cooling. The effect of the structural parameters, such as rib height (e), pitch-to-height ratio (p/e), nondimensional jet-to-surface spacing (Z/d) and the relative position of the jet hole to the ribs etc., and the crossflow rate on the flow behavior have been investigated by the flow visualization on a variety of configuration models. The experimental results reveal the mechanism of flow behavior and explain the flow and heat transfer characteristics of the impingement cooling from ribbed surface with crossflow.

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Yamamoto, Atsumasa, Katsuyoshi Kaba, and Takayuki Matsunuma. "Measurement and Visualization of Three-Dimensional Flows in a Linear Turbine Cascade." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-341.

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To know the internal flows and the loss generation mechanisms in turbine blade passages, three–dimensional flows in a linear turbine cascade were measured in detail using a five–hole Pitot tube. Flow visualization tests were also carried out with oil smoke to see the unsteady behavior of the internal flows. The flow visualization tests show generation of various vortices occurring inside the cascade passage, which were hardly detectable with steady flow measurement. Many of the vortices behave unsteadily. The evolution of two legs of the leading edge horseshoe vortex was clearly visualized as a combined vortex system. Low energy fluids inside the boundary layer on the blade suction surface were seen to circulate very slowly and were fairly unstable. Rotational directions of the low energy fluids depend on the interaction with the surrounding vortex system. Many separated and strong reverse flows were also seen near the blade trailing edge.

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