Application of laser velocimetry to unsteady flows in large scale high speed tunnels

Flowfield measurements obtained in several large scale, high speed facilities are presented. Sampling bias and seeding problems are addressed and solutions are outlined. The laser velocimeter systems and data reduction procedures which were used in the experiments are also described. The work demonstrated the potential of the laser velocimeter for applications in other than closely controlled, smallscale laboratory situations

Implementation of a high resolution optical feedback interferometer for microfluidics applications

Recent progress of interferometric sensors based on the optical feedback in a laser diode have demonstrated possibility for measurement of flow rates and flow-profiles at the micro-scale. That type of compact and embedded sensors is very promising for a research and industrial field –microfluidics – that is a growing domain of activities, at the frontiers of the physics, the chemical science, the biology and the biomedical. However, the acquisition of flow rate or local velocity at high resolution remains a very challenging issue, and the sensors that have been proposed so far did not have been giving sufficient information on the nature of the particles flowing. The present thesis is driven to the implementation, validation and evaluation of the sensing performances of the optical feedback interferometry technology in both chemical and biomedical fields of applications. The elaboration of a new generation of sensors that will provide both a high spatial resolution for 2D Doppler imaging is presented, as well as a methodology that gives further information on the flowing particles concentration and/or dimensions. Then, a new embedded optical feedback interferometry imager for flowmetry has been realized using a 2-axis beamsteering mirror mounted on Micro-Electro-Mechanical Systems (MEMS) thus taking the full advantage of the compactness offered by the optical feedback interferometry sensing scheme. While previous works on optical feedback interferometry flowmetry have been limited to high particle densities fluids in single or multiple scattering regimes, we present also a sensing technique based on the optical feedback interferometry scheme in a laser diode that enables single particle detection at micro and nanoscales through the Doppler-Fizeau effect. Thanks to the proposed signal processing, this sensing technique can detect the presence of single spherical polystyrene micro/nanospheres seeded in watery suspensions, and measure their flow velocity, even when their diameter is below half the laser wavelength. It discriminates particle by their diameter up to a ratio of 5 between large and small ones while most of the technologies for particle characterization is bulk and requires manipulation of the fluid with small volume handling, precise flow and concentration control. Altogether, the results presented in this thesis realize a major improvement for the use of optical feedback interferometry in the chemical engineering or biomedical applications involving micro-scale flows

Development of a new velocity measurement technique : the laser bessel velocimetry

The present thesis describes the design, construction and testing of a new velocity measurement optical technique system. The technique has similarities with the laser Doppler velocimetry (LDV) in that it uses scattered light detection, in order to measure one component of the velocity vector of moving flows or solid surfaces. It uses the fringes of a Bessel beam produced by an axicon to generate the measurement volume. This technique, which we call Laser Bessel velocimetry (LBV), is noninvasive and permits continuous velocity measurements of moving particles. The experimental measurement set-up including the laser source, the optical devices, a moving stage with known velocities, a photodetector to capture scattered light and signal processing and data acquisition components, was developed and used to provide a proof of concept of this new technique. The set-up was also tested with a commercial LDV system. Two types of refractive linear axicons have been used to generate a Bessel type beam by illuminating the axicons with blue and red collimated and coherent laser light of dissimilar wavelengths, λ. The linear axicons offer the advantage of simplicity. The software tools for measurements, acquisition and analysis of the data are developed using NI Labview and MATLAB. Results from both theoretical simulation and experimental measurements are presented and compared.Master's These

Frequency domain laser velocimeter signal processor: A new signal processing scheme

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a smart instrument that is able to configure itself, based on the characteristics of the input signals, for optimum measurement accuracy. The signal processor is composed of a high-speed 2-bit transient recorder for signal capture and a combination of adaptive digital filters with energy and/or zero crossing detection signal processing. The system is designed to accept signals with frequencies up to 100 MHz with standard deviations up to 20 percent of the average signal frequency. Results from comparative simulation studies indicate measurement accuracies 2.5 times better than with a high-speed burst counter, from signals with as few as 150 photons per burst

Implementation of optical feedback interferometry for sensing applications in fluidic systems

Optical feedback interferometry is a sensing technique with relative recent implementation for the interrogation of fluidic systems. The sensing principle is based on the perturbation of the laser emission parameters induced by the reinjection in the laser cavity of light back-scattered from a distant target. The technique allows for the development of compact and noninvasive sensors that measure various parameters related to the motion of moving targets. In particular, optical feedback interferometers take advantage of the Doppler effect to measure the velocity of tracers in flowing liquids. These important features of the optical feedback interferometry technique make it wellsuited for a variety of applications in chemical engineering and biomedical fields, where accurate monitoring of the flows is needed. This thesis presents the implementation of optical feedback interferometry based sensors in multiple fluidic systems where local velocity or flow rate are directly measured. We present an application-centered study of the optical feedback sensing technique used for flow measurement at the microscale with focus on the reliability of the signal processing methods for flows in the single and the multiple scattering regimes. Further, we present experimental results of ex vivo measurements where the optical feedback sensor is proposed as an alternative system for myography. In addition we present a real-time implementation for the assessment of non-steady flows in a millifluidic configuration. A semi-automatized system for single particle detection in a microchannel is proposed and demonstrated. Finally, an optical feedback based laser sensor is implemented for the characterization of the interactions between two immiscible liquid-liquid flowing at the microscale, and the measurement is compared to a theoretical model developed to describe the hydrodynamics of both fluids in a chemical microreactor. The present manuscript describes an important contribution to the implementation of optical feedback sensors for fluidic and microfluidic applications. It also presents remarkable experimental results that open new horizons to the optical feedback interferometry

Design and numerical simulation of the real-time particle charge and size analyser

The electrostatic charge and size distribution of aerosol particles play a very important role in many industrial applications. Due to the complexity and the probabilistic nature of the different charging mechanisms often acting simultaneously, it is difficult to theoretically predict the charge distribution of aerosol particles or even estimate the relative effect of the different mechanisms. Therefore, it is necessary to measure the size and also the bipolar charge distribution on aerosol particles. The main aim of this research project was to design, implement and simulate a signal processing system for novel, fully functional measurement instrument capable of simultaneously measuring in real time the bipolar charge and size distribution of medical aerosols. The Particle Size and Charge Analyser (PSCA), investigated in this thesis, uses Phase Doppler Anemometry (PDA) technique. The PDA system was used to track the motion of charged particles in the presence of an electric field. By solving the equation of particle motion in a viscous medium combined with the simultaneous measurement of its size and velocity, the magnitude as well as the polarity of the particle charge can be obtained. Different signal processing systems in different excitation fields have been designed and implemented. These systems include: velocity estimation system using spectral analysis in DC excitation field, velocity estimation system based on Phase Locked Loop (PLL) technique working in DC as well as sine-wave excitation fields, velocity estimation system based on Quadrature Demodulation (QD) technique under sine-wave excitation method, velocity estimation system using spectral analysis in square-wave excitation field and phase shift estimation based on Hilbert transformation and correlation technique in both sine-wave and square-wave excitation fields. The performances of these systems were evaluated using Monte Carlo (MC) simulations obtained from the synthesized Doppler burst signals generated from the mathematical models implemented in MATLAB. The synthesized Doppler Burst Signal (DBS) was subsequently corrupted with the added Gaussian noise. Cross validation of the results was performed using hardware signal processing system employing Arbitrary Waveform Generator and also NASA simulator to further confirm the validity of the estimation

Comprehensive review and application of particle image velocimetry

For a fluid dynamics experimental flow measurement technique, particle image velocimetry (PIV) provides significant advantages over other measurement techniques in its field. In contrast to temperature and pressure based probe measurements or other laser diagnostic techniques including laser Doppler velocimetry (LDV) and phase Doppler particle analysis (PDPA), PIV is unique due to its whole field measurement capability, non-intrusive nature, and ability to collect a vast amount of experimental data in a short time frame providing both quantitative and qualitative insight. These properties make PIV a desirable measurement technique for studies encompassing a broad range of fluid dynamics applications. However, as an optical measurement technique, PIV also requires a substantial technical understanding and application experience to acquire consistent, reliable results. Both a technical understanding of particle image velocimetry and practical application experience are gained by applying a planar PIV system at Michigan Technological University’s Combustion Science Exploration Laboratory (CSEL) and Alternative Fuels Combustion Laboratory (AFCL). Here a PIV system was applied to non-reacting and reacting gaseous environments to make two component planar PIV as well as three component stereographic PIV flow field velocity measurements in conjunction with chemiluminescence imaging in the case of reacting flows. This thesis outlines near surface flow field characteristics in a tumble strip lined channel, three component velocity profiles of non-reacting and reacting swirled flow in a swirl stabilized lean condition premixed/prevaporized-fuel model gas turbine combustor operating on methane at 5-7 kW, and two component planar PIV measurements characterizing the AFCL’s 1.1 liter closed combustion chamber under dual fan driven turbulent mixing flow

A Scanning laser-velocimeter technique for measuring two-dimensional wake-vortex velocity distributions

A rapid scanning two dimensional laser velocimeter (LV) has been used to measure simultaneously the vortex vertical and axial velocity distributions in the Langley Vortex Research Facility. This system utilized a two dimensional Bragg cell for removing flow direction ambiguity by translating the optical frequency for each velocity component, which was separated by band-pass filters. A rotational scan mechanism provided an incremental rapid scan to compensate for the large displacement of the vortex with time. The data were processed with a digital counter and an on-line minicomputer. Vaporized kerosene (0.5 micron to 5 micron particle sizes) was used for flow visualization and LV scattering centers. The overall measured mean-velocity uncertainity is less than 2 percent. These measurements were obtained from ensemble averaging of individual realizations