Colour-coding schlieren techniques for the optical study of heat and fluid flow

doi:10.1016/0142-727X(85)90024-4

International Journal of Heat and Fluid Flow

Volume 6, Issue 1, March 1985, Pages 3-15

https://doi.org/10.1016/0142-727X(85)90024-4 Get rights and content

Abstract

This survey presents a unified view of the history, rationale, applications, and current status of colour-coding schlieren optical techniques, based on an extensive literature review. The characteristics and advantages of this unique flow visualization tool are discussed in terms of one- and two-dimensional colour-coding, qualitative and quantitative visualisations, and system sensitivity, range and resolution. In particular, the use of matched spatial filters to tailor the schlieren optics for specific applications is stressed. A wide range of past applications in fluid flow and heat transfer is surveyed. Connections are drawn among these applications and some new applications are discussed.

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Cited by (54)

In-situ measurements of temperature field and Marangoni convection at hydrogen bubbles using schlieren and PTV techniques
2023, International Journal of Heat and Mass Transfer
This work adapts the schlieren technique for in-situ measurement of temperature fields around gas bubbles growing during water electrolysis. First, the optical setup and the algorithm of data processing are explained. The method is then validated by comparing measurements near a laser-heated spherical thermocouple with numerical simulations. Further validation is obtained by comparing with temperature data measured earlier by a different method near a hydrogen bubble generated at a platinum microelectrode [2]. The schlieren technique is shown to deliver accurate temperature distributions with an uncertainty of less than 15%. The method was then used to investigate the temperature distribution near hydrogen bubbles during growth at different cathodic potentials. Additionally, particle tracking velocimetry was used to visualize the Marangoni flow pattern generated by strong Joule heating near the bubble foot. Combining the information from schlieren and PTV imaging allows to provide a more complete understanding of the fluid dynamics and heat transfer around gas bubbles growing during electrolysis.
On the identification and mapping of three distinct stages of single vapor bubble growth with the corresponding microlayer dynamics
2021, International Journal of Multiphase Flow
An experimental study to establish a one-on-one correspondence between microlayer dynamics and growth process of single vapor bubble under nucleate pool boiling regime has been presented. The transient evolution of microlayer and the corresponding vapor bubble growth have been simultaneously recorded using a thin film interferometer and one of the gradients-based imaging techniques, namely rainbow schlieren deflectometry. Based on interferometry measurements, the microlayer is observed to undergo three distinct stages. Each of these stages is identified by distinct microlayer structure namely, inverted conical, flattened peripheral region and truncated conical structure during the initial, transitional and diffusion-controlled growth phases of the vapor bubble. Contribution of microlayer towards bubble growth has been established by quantifying the time rate of change of net mass of the superheated fluid entrapped in the microlayer region and the corresponding rate of change of mass of the growing bubble. The analysis showed that the ratio of mass of the superheated fluid in the microlayer region to the mass of the vapor bubble does not exceed a maximum of ~ 15%. For any given heat flux level, the growing vapor bubble is seen to acquire its maximum size in the transitional regime of the growth process during which the microlayer exhibits a flattened peripheral region. Possible impact of varying heat flux level on microlayer dynamics and movement of the apparent contact line of the vapor bubble has also been discussed. A reasonably good agreement of the experimental data with some of the well-established bubble growth models for initial microlayer thickness has been observed. Based on the experimental results, critical value of empirical parameter ‘C_slope’ (parameter correlating the bubble base radius and the maximum microlayer thickness) for transition from inertia-driven to diffusion dominated growth has been identified to be ~ 0.0042.
Rainbow schlieren-based investigation of heat transfer mechanisms during isolated nucleate pool boiling phenomenon: Effect of superheat levels
2018, International Journal of Heat and Mass Transfer
Citation Excerpt :
Recent developments in the field of refractive index-based non-intrusive optical diagnostics coupled with the technological advancements in terms of increased data processing speeds of computers for digital image processing have helped in significantly improving both temporal and spatial resolutions of such laser and/or white light-based measurements systems. The inherent advantages of the refractive index-based whole field measurement techniques lie in the fact that these techniques not only serve as a qualitative tool for direct visualization of heat transfer processes but also provide the whole field quantitative data; for instance, fringe patterns in interferometry [31–34], color re-distribution in rainbow schlieren deflectometry representing the thermal gradients [35–38] and intensity variations in shadowgraph [39]. Some of earliest efforts which involve the use of non-intrusive optical diagnostic tools in the context of nucleate boiling can be seen in the works of Mayinger [40–43].
Experimental investigation of various heat transfer mechanisms associated with isolated nucleate pool boiling have been presented. Measurements have been made in a complete non-intrusive manner using rainbow schlieren deflectometry technique. Boiling experiments have been performed for two levels of superheat with the bulk fluid maintained under saturated conditions. The rainbow schlieren images have first been subjected to qualitative interpretation wherein various sub-processes associated with the boiling phenomenon, such as development of thermal boundary layer on the substrate surface, inception of single bubble, growth of the vapor bubble till it departs, and scavenging of the superheat layer following the bubble departure have been discussed. Contributions of individual sub-processes towards the overall heat transfer rates achieved for a given superheat level have been determined through quantitative analysis of the images. Schlieren observations revealed the effect of varying superheat levels on parameters such as bubble diameter and departure time. Detailed heat transfer analysis revealed the dominance of evaporative heating in contributing towards the overall heat transfer rates. On the other hand, the contribution of natural convection from the heated substrate was found to be relatively small. In quantitative terms, the evaporative heating was seen to have an individual contribution as high as ≈66% to the overall heat transfer and ≈88% to the growth of the vapor bubble in the case of superheat level of 7 °C.
Investigation of the double ramp in hypersonic flow using luminescent measurement systems
2012, Experimental Thermal and Fluid Science
Citation Excerpt :
Specifications of the experimental conditions are shown in Table 1. Schlieren allows for the visualisation of invisible light refractions [24,25]. The benefit of colour Schlieren, used here, is that with the addition of colour it not only becomes easier to discern flow features but the intensity of the colour also gives an indication of the magnitude of the flow features.
Compression ramp flows in supersonic and hypersonic environments present unique flow patterns for shock wave-boundary layer interaction studies. They also represent the generic geometry of two-dimensional inlets and deflected control surfaces for re-entry vehicles. Therefore, a detailed knowledge of the flow behaviour created by such geometries is critical for optimum design. The flow is made more complicated due to the presence of separation regions and streamwise Görtler vortices. The objective of the current research is to study the behaviour and characteristics of the flow over the double ramp model placed in hypersonic flow at freestream Mach number of 5. Three different incidence angles of 0°, −2°, and −4° are studied using colour Schlieren and luminescent paints consisting of anodized aluminium pressure-sensitive paint (AA-PSP) and the temperature-sensitive paint (TSP) technique. The colour Schlieren provides description of the external flow while the global surface pressure and temperature distribution is obtained through the AA-PSP and TSP methods. The TSP technique also proves that it is very effective in identifying the location and properties of the Görtler vortices; revealing the effect of incidence on the magnitude and pattern of Görtler vortices formed.
Application of AA-PSP to hypersonic flows: The double ramp model
2012, Sensors and Actuators, B: Chemical
Citation Excerpt :
The variation in flow Mach number and Reynolds number for different runs of the tunnel were ±0.4% and ±3.5%, respectively [10]. The schlieren technique allows for the visualisation of otherwise invisible light refractions [11]. Conventional black and white schlieren systems utilising a slit as source and horizontal or vertical knife edge have the ability to show refractive index gradients which deflect the light rays normal to the knife edge, making the system a one-dimensional tool [12].
Anodized Aluminium Pressure Sensitive Paint (AA-PSP) is known for its rapid response characteristics, making it a highly desirable technique when studying high-speed phenomenon on a global scale. The current study examines the efficacy of the AA-PSP technique, which is prepared with a more practical approach than that reported in literature, in analysing the flow characteristics of a double ramp model placed in hypersonic flow of M = 5. Three different flow angles of 0°, −2°, and −4° are studied. Two-dimensional colour schlieren visualisation, using a colour wheel, is employed alongside high sensitivity Kulite pressure tap data to corroborate the AA-PSP findings. The AA-PSP results show good correlation between the qualitative schlieren and ±8.9% discrepency with the quantitative pressure tap data. The more practical AA-PSP preparation proposed in the current study, which uses aluminium alloy 6-series rather than pure aluminium, is proved to have the response time and the accuracy to be applied to unsteady high-speed flows.
Natural convective heat transfer in vertical channels with low-thermal-conductivity ribs
2008, International Journal of Heat and Fluid Flow
The effect of repeated horizontal protrusions on the free-convection heat transfer in a vertical, asymmetrically heated, channel has been experimentally investigated. The protrusions have a square section and are made of a low-thermal-conductivity material. Experiments were conducted by varying the number of the protrusions over the heated surface (whose height was held fixed) and the aspect ratio of the channel. The convective fluid was air and the wall-to-ambient air temperature difference was set equal to 45 K. The local heat transfer coefficient was obtained by means of the schlieren optical technique.
The protrusions were found to significantly alter the heat transfer distribution along the heated surface of the channel, especially in the vicinity of each obstacle. For the ranges of parameters studied, the addition of low-conductivity protrusions leads to a decrease in the average heat transfer coefficient, as compared to that for the smooth surface, in the 0–7% range for the largest channel aspect ratio and in the 18–43% for the smallest channel aspect ratio.

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^☆: This survey is a greatly expanded version of a symposium paper.

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Colour-coding schlieren techniques for the optical study of heat and fluid flow☆

Abstract

Adv. in Heat Transfer

Schlierenverfahren und Ihre Anwendungen

Ergeb. der Exakt. Naturwiss.

Das Toeplersche Schlierenverfahren: Grundlagen fur seine Anwendung und Quantitative Auswertung

Forschungsheft 367, Forsch. a. dem Geb. des Ings.

Schlieren Methods

NPL Notes on Applied Science No. 31

Optical Methods for Examining the Flow in High-Speed Wind Tunnels; Part 1: Schlieren Methods

AGARDograph

Schlieren Photography: A Short Bibliography and Review

High Speed Photog. and Photonics Newsletter, Photomethods

Flow Visualisation

Introduction to Classical and Modern Optics

Optical Techniques for the Study of Phase Boundaries

Univ. of Calif., Berkeley. LRL Report UCRL-11997

Schlieren Photography

Kodak Corp. Pamphlet P-11

Flow Visualisation: Optical Methods of Analysing Flows

Modern Developments in Flow Visualisation

AIAA Paper 84-1599

Tenevye Metody (Schlieren Methods)

Optics of Flames

Schlieren, Phase-Contrast, and Light-Intersection Methods

Handbuch der Phys.

Phase Contrast, Schlieren, and Interference Microscopy

Micros. Acta

Color Schlieren Optics — A Review of Techniques and Applications

Color and Conspicuousness

J. Opt. Soc. Am.

Beobachtungen nach Einer Nueun Optischen Methode

Optische Studien nach der Methode der Schlieren-beobachtung

Poggendorffs Ann.

Optical Information Processing

Schlieren Experiment 300 Years Ago

Nature

Memoire sur la Construction des Telescopes en verre argente

Ann. de l'Observatoire Imp. de Paris

On an Addition to the Methods of Microscopical Research, by a new way Optically producing Colour-Contrast between an Object and its Background, or between Definite Parts of the Object Itself

J. Royal Microscop. Soc.

Rheinberg Differential Color Illumination in Biomedical Photomicrography

Biomedical Photography, Eastman Kodak Co. Data Book N-19

Beitrage zur Theorie des Mikroskops und der mikroskopischen Wahrnehmung

Arch. fur Mikr. Anat.

A Schlieren Apparatus Giving an Image in Colour

Nature

A Colour Schlieren System Using Multicolor Filters of Simple Construction

NPL Aero Note 266

A High Resolution, High Sensitivity Color Schlieren Method

SPIE J.

Flow Studies with an Improved Diffraction Grating Interferometer and a New Color Schlieren Method for Quantitative Analysis

A Color Schlieren System Without Image Degradation

SPIE J.

A Direction-Indicating Color Schlieren System

AIAA J.

Boundary-Layer Photography of Swimming Fish

A Versatile Apparatus for the Study of Refractory Index Fields

USAF ARL Report 63-45

Nonmetalized Solid Propellant Combustion in Standard and High Acceleration Environments

Combustion Sci. and Tech.

Separation Measurements on a Delta Wing in a Shock Tunnel at M=8.6 Using Monochrome and Colour Schlieren Photography

NPL Aero Note 1097 (A.R.C. 32 399)

Color Schlieren

Research/Development

A Color Schlieren System

Rutgers Univ. Mech, Engr. Dept. Report 105-ME-F

Schlieren Analysis Goes to Color

Astron. and Aeron.

Film Study of High-Velocity Gas Flow Phenomena

SMPTE J.

A Color Schlieren System

Photog. Applicns. in Sci. Tech. and Medicine

Streak Photography with a Color Schlieren System

Sov. Tech. Phys. Letters

Color Schlieren

New York Univ. Mech Engr. Dept. Lab. Experiments In Fluid Mech. and Heat Trans.

Investigation of the Process of Energy Transfer from an Intermittent Jet to a Secondary Fluid in an Ejector-Type Thrust Augmentor

Hiller Aircraft Corp. Report ARD-286

Ammonium Perchlorate and Ammonium Perchlorate-Binder Sandwich Construction