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Optical Methods Of Measuring Turbulence


Optical Methods Of Measuring Turbulence
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Optical Methods Of Measuring Turbulence


Optical Methods Of Measuring Turbulence
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Author : M. S. Vasudevan
language : en
Publisher:
Release Date : 1969

Optical Methods Of Measuring Turbulence written by M. S. Vasudevan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1969 with Gas flow categories.




Experimental Investigation Of Optical Methods For Measuring Turbulence


Experimental Investigation Of Optical Methods For Measuring Turbulence
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Author : Leslie S. G. Kov asznay
language : en
Publisher:
Release Date : 1952

Experimental Investigation Of Optical Methods For Measuring Turbulence written by Leslie S. G. Kov asznay and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1952 with categories.




Development Of A Ground Based Optical Method For Measuring Atmospheric Turbulence Aloft


Development Of A Ground Based Optical Method For Measuring Atmospheric Turbulence Aloft
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Author : G. R. Ochs
language : en
Publisher:
Release Date : 1974

Development Of A Ground Based Optical Method For Measuring Atmospheric Turbulence Aloft written by G. R. Ochs and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1974 with Atmospheric turbulence categories.




Optical Measurements


Optical Measurements
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Author : Franz Mayinger
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-03-14

Optical Measurements written by Franz Mayinger and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-03-14 with Science categories.


Increasing possibilities of computer-aided data processing have caused a new revival of optical techniques in many areas of mechanical and chemical en gineering. Optical methods have a long tradition in heat and mass transfer and in fluid dynamics. Global experimental information is not sufficient for developing constitution equations to describe complicated phenomena in fluid dynamics or in transfer processes by a computer program . Furthermore, a detailed insight with high local and temporal resolution into the thermo-and fluiddynamic situations is necessary. Sets of equations for computer program in thermo dynamics and fluid dynamics usually consist of two types of formulations: a first one derived from the conservation laws for mass, energy and momentum, and a second one mathematically modelling transport processes like laminar or turbulent diffusion. For reliably predicting the heat transfer, for example, the velocity and temperature field in the boundary layer must be known, or a physically realistic and widely valid correlation describing the turbulence must be avail able. For a better understanding of combustion processes it is necessary to know the local concentration and temperature just ahead of the flame and in the ignition zone.



Statistical Tomography For Scalar Turbulence Measurements Using Line Of Sight Optical Techniques


Statistical Tomography For Scalar Turbulence Measurements Using Line Of Sight Optical Techniques
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Author : Pankaj Sharadchandra Kolhe
language : en
Publisher:
Release Date : 2009

Statistical Tomography For Scalar Turbulence Measurements Using Line Of Sight Optical Techniques written by Pankaj Sharadchandra Kolhe and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Electronic dissertations categories.


Turbulence has been an intriguing subject for several decades with past studies focusing on understanding the transition to turbulence and characterizing turbulence using statistical tools. In present research rainbow schlieren deflectometry (RSD), a line of sight optical technique, is used and its high spatio-temporal resolution measurement capability is demonstrated through transitional hydrogen gas jet diffusion flame experiments wherein hitherto unknown secondary instability in flame surface is captured by employing 23 microseconds exposure time and 400 micro-meter/pixel resolution at 2000 Hz image sampling rate. Significant effects of buoyancy previously thought unimportant are identified and a conceptual view of transitional jet diffusion flames illustrating various instabilities is developed. The quantitative characterization of turbulent flow requires local scalar field statistics. However, RSD provides path integrated measurements that must be deconvoluted to obtain the local field statistics. For round turbulent jets, Abel inverse transform can be used to deconvolute time averaged local field quantities such as mean refractive index difference. Based on critical evaluation of four techniques two point formula, a semi-analytical approach, is recommended to evaluate the improper integral in Abel inverse transform with best accuracy and minimum error propagation. For deconvolution of second moment statistics (scalar fluctuation intensity) from path integrated measurements cross beam correlation (CBC) algorithm is presented and analyzed using noise free synthetic scalar turbulent data. CBC algorithm is found to yield accurate reconstruction only in fully developed turbulent flows and it required knowledge of statistics at inlet boundary that are generally unknown. To overcome limitations of CBC algorithm, a novel spectral analysis algorithm is developed and verified using synthetic scalar turbulent data. The algorithm provided local field statistics (mean and variance) at high accuracy using path integrated data in only one line of sight. Present implementation was limited to time averaged axisymmetric turbulent flow although its extension to asymmetric flow is feasible. Spectral analysis algorithm was applied for measurements in a turbulent helium jet with diameter, d = 2.96 mm at Reynolds number, Re = 3500 and Richardson's number, Ri =0.0000102335. Mean, variance, autocorrelation function, and power spectra of local scalar properties are presented to characterize the turbulent flow.



Imaging Through Turbulence


Imaging Through Turbulence
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Author : Michael C. Roggemann
language : en
Publisher: CRC Press
Release Date : 2018-02-06

Imaging Through Turbulence written by Michael C. Roggemann and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-02-06 with Technology & Engineering categories.


Learn how to overcome resolution limitations caused by atmospheric turbulence in Imaging Through Turbulence. This hands-on book thoroughly discusses the nature of turbulence effects on optical imaging systems, techniques used to overcome these effects, performance analysis methods, and representative examples of performance. Neatly pulling together widely scattered material, it covers Fourier and statistical optics, turbulence effects on imaging systems, simulation of turbulence effects and correction techniques, speckle imaging, adaptive optics, and hybrid imaging. Imaging Through Turbulence is written in tutorial style, logically guiding you through these essential topics. It helps you bring down to earth the complexities of coping with turbulence.



Preliminary Investigation Of An Optical Technique For Localized Measurements In Turbulent Jets


Preliminary Investigation Of An Optical Technique For Localized Measurements In Turbulent Jets
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Author : George Peter Mende
language : en
Publisher:
Release Date : 1957

Preliminary Investigation Of An Optical Technique For Localized Measurements In Turbulent Jets written by George Peter Mende and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1957 with Jets categories.


"This report presents a preliminary investigation of the crossed beam correlation technique for the measurement of local characteristics of turbulent jets. Tests on a bromine jet flowing coaxially to an air stream indicate the feasibility of the approach. Continuous recording-reduction equipment should be used to facilitate data acquisition. Extension of this method to the examinat ion of turbulent flames was shown to be possible since response similar to that of a cooled film anemometer was obtained. Where anemometry cannot be applied this technique is especially useful, such as in the investigation of projectile centrelines, turbulent flames and other high energy flows. Initial experiments demonstrate the versatility of this technique and thus warrant continued development." --



An Exploration Of New Optical Techniques For Turbulence Measurement Using Photon Correlation Laser Anemometry


An Exploration Of New Optical Techniques For Turbulence Measurement Using Photon Correlation Laser Anemometry
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Author : R. G. W. Brown
language : en
Publisher:
Release Date : 1983

An Exploration Of New Optical Techniques For Turbulence Measurement Using Photon Correlation Laser Anemometry written by R. G. W. Brown and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1983 with categories.




Optical Turbulence Measurement Investigations For Analysis Of Laser Designator Spot Patterns


Optical Turbulence Measurement Investigations For Analysis Of Laser Designator Spot Patterns
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Author : E. C. Crittenden
language : en
Publisher:
Release Date : 1983

Optical Turbulence Measurement Investigations For Analysis Of Laser Designator Spot Patterns written by E. C. Crittenden and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1983 with categories.


This methodology investigation evaluates the feasibility of applying video image analysis techniques and instrumentation to characterize optical path turbulence for use in assessing the field performance of laser designator systems. The effort focused on adpating a C sub n sub 2 path weighted measurement technique developed by Dr. E. Crittenden, NPS, which uses a telescope mechanical slit scanner configuration for data acquisition. The Phase I effort presented in this report covers a theoretical analysis and empirical measurements to include a coincident path performance comparison of the scanner and a video system in a laboratory environment. Computer programs for analyzing the video data using either a real time digitizer or a digital storage oscilloscope were also developed. The results of the investigation demonstrate that the video technique can be applied to the measurement of C sub n sub 2 and a test plan to further validate the technique in a field environment is presented. (Author).



Optical Measurements Of Mixing Processes In Turbulent Fluid Flows


Optical Measurements Of Mixing Processes In Turbulent Fluid Flows
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Author : Huixin Li
language : en
Publisher:
Release Date : 2023

Optical Measurements Of Mixing Processes In Turbulent Fluid Flows written by Huixin Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.


Many processes in chemical engineering and oceanography rely on fluid mixing. This thesis focuses on optical measurement techniques to experimentally investigate miscible liquid-liquid mixing and gas-liquid mixing. Previous numerical studies have examined the turbulent small-scale mixing, which is experimentally challenging because of the limited spatial resolution of the measurement techniques. A further difficulty emerges for active fluid mixing. When fluids of different densities, such as water and ethanol are mixed, experimental measurements for the small-scale fluctuations in turbulence are impeded by the optical distortion due to the spatio-temporally varying refractive index field. In this thesis, in order to investigate small-scale liquid-liquid mixing, an upscaled T-mixer was built with a height of 40 millimetres. A planar laser-induced fluorescence (PLIF) with high resolution was employed in proof-of-concept experiments concerning the T-junction. The results indicate that measuring the small-scale mixing in the viscous-convective range where the velocity does not fluctuate, but the scalar does, is possible. Subsequently, long inlet channels were added to the T-junction and the particle image velocimetry (PIV) technique was used to verify the fully developed laminar flows and to investigate the flow regimes for different Reynolds numbers. It was found that the present setup can achieve inlet conditions with fully developed laminar flows when the Reynolds number is smaller than 1100. The setup was validated by repeating the flow regimes in previous studies. However, small temperature differences had a weak effect on flow regimes, which should be avoided in the next measurements. Overall, high-quality measuring of the small-scale mixing dynamics in the T-mixer is now within reach. For active mixing with fluids of different densities, mixing usually causes optical measurement errors. In this thesis, a ray tracing simulation method is used in a three-dimensional flow to quantify the measurement errors of the flow velocity and flow acceleration for tracer-based velocimetry, i.e., particle tracking velocimetry (PTV). The flow field is from a direct numerical simulation of single-phase turbulent mixing of two miscible fluids. The measurement errors increase with increasing the refractive index difference. The errors of both velocity and acceleration are attributed to the spatial and the spatio-temporal gradients of the refractive indices. Since PTV, PIV and PLIF share the same working principles based on geometric optics, the findings are also assumed to hold for the measurements of other techniques. The thermal effect in the T-mixer on the measurement errors is subsequently estimated and found to be negligible. Finally, gas-liquid mixing is examined, in which a weakly soluble gas is transferred across the gas-liquid interface. This process is related to the climate balance and depends on surface waves and turbulence underneath the water in the ocean. Utilizing the refraction at the interface and optical displacements, a synthetic Schlieren method is developed to measure the surface topography. This method is implemented in experiments and allows high-accuracy measurements of free surface waves. This makes it feasible to implement simultaneous measurements of surface waves, mass transportation and turbulence under the water.