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Topic: Laser Doppler velocimetry

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	Engine Research Center
		A laser is separated into two beams that cross at point that is typically about 0.5 mm in size.
		A laser is coherent, which means that the light is all in phase, i.e.
		When a particle is moving the light it scatters is Doppler shifted (think of a moving train that has its pitch vary from when it approaches to when it is moving away from you).
	www.erc.wisc.edu /advanced_diagnostics/tutorials/optical_diagnostics_tutorial_ldv.html (557 words)

	CRDEssay: Laser Doppler Velocimetry
		Small particles suspended in fluid are illuminated by a laser beam and the light scattered to various angles is compared to light in a reference beam to determine the doppler shift of the scattered light.
		The spatial frequency of the fringe pattern is dependent upon the angle of observation, particle refraction index, beam intersection angle, laser wavelength and particle diameter.
		For spherical and refracting particles and in given conditions of particle refractive index and for the wavenumber of the laser light, the phase-shift may be expressed as a linear function of particle diameter (Naqwi et al., 1991).
	alcor.concordia.ca /~raojw/crd/essay/essay001951.html (670 words)

	NEEP Lab
		The laser velocimetry experiment makes use of a setup that includes a laser source, mirrors, beam splitter, convex lens, glass pipe with water flowing through it, and a photon detector.
		Laser velocimetry is a method of measuring particle velocities and flow rates that has become standard in fluid research labs across the world, thanks to its accuracy and noninvasive properties.
		The Laser Doppler Velocimetry used in this lab is especially useful, working in air or water, and has been used not only for fluid flows but even measuring the wake left by rotor blades on a helicopter or the concussion waves of a shock tube.
	www.rpi.edu /~danony/NEEP/velocimetry1.htm (334 words)

	Laser Doppler velocimetry - Wikipedia, the free encyclopedia
		Laser Doppler velocimetry (LDV, also known as laser Doppler anemometry, or LDA) is a technique for measuring the direction and speed of fluids like air and water.
		In its simplest form, LDV crosses two beams of collimated, monochromatic laser light in the flow of the fluid being measured.
		LDV is chosen over other forms of fluid velocity measurement such as Pitot tube measurements because the measurement equipment can be outside of the flow being measured and therefore have minimal effect on the flow.
	en.wikipedia.org /wiki/Laser_Doppler_velocimetry (205 words)

	SPIE Proceedings Vol. 2052
		Abstract: A 2-Dimensional Laser Doppler Velocimeter was used to investigate particle flow in the sampling chamber of a particle analyzer.
		Laser Doppler anemometry is widely used to measure the local, time-dependent velocities, while phase Doppler anemometry has been developed to measure particle size, distribution and velocity.
		Abstract: Based on laser Doppler anemometry, the mean and fluctuating components of the flow of a non-Newtonian shear thinning fluid in the transition regime in a vessel agitated either by a narrow or a wide blade axial flow hydrofoil impeller are presented for the first time.
	www.spie.org /web/abstracts/2000/2052.html (5315 words)

	Laser Doppler Velocimetry
		The phenomenon of Doppler shift is used to measure the velocities of explosively driven metal plates.
		Doppler shift is a change of the wavelength of a wave, due to the difference in velocity between the source of the wave and the observer.
		Doppler shift also occurs in distant stars and galaxies making them appear more red than they actually are, due to them receding at great velocity.
	www.awe.co.uk /main_site/scientific_and_technical/featured_areas/hydrodynamics_contents/esr-contents/esr-c/esr-c2/index.html (157 words)

	Planar Doppler Velocimetry
		Construction of a flow map using point measurement techniques, such as laser Doppler velocimetry requires measurements to be made sequentially over an array of positions with the flow.
		is the Doppler shift, c is the speed of light V is the magnitude of velocity of the particle in the direction (o - i) where o is the direction of the laser and i is to the direction of viewing.
		The laser is tuned to the flank of appropriate absorption band and the attenuated signal is passed by a signal detector.
	www.cranfield.ac.uk /soe/cpoe/pdv_main.htm (429 words)

	A Laser Doppler Velocimetry (LDV) System for Fish Bypass Evaluation
		A three-beam, two-component LDV device is used to measure velocities precisely along a surface.
		Laser Doppler velocimetry (LDV) systems have been used for a number of years in field and laboratory applications.
		To complement the three-beam LDV system, WES uses computer-controlled traversing systems to control the position of the laser probe to within 0.1 mm, thus assuring any difference in the flow field is due to a physical change in the model.
	www.nasatech.com /Briefs/Jan98/ETB01983.html (556 words)

	[No title]
		Laser Doppler Velocimetry (LDV) is a technique that fluid mechanics researchers use to make instantaneous velocity measurements (magnitude and direction) of fluid flow.
		The frequency of the scattered light is Doppler shifted and referred to as the Doppler frequency of the flow.
		This Doppler frequency is proportional to a component of the particles velocity which is perpendicular to the planar fringe pattern produced by the beam crossing.
	www.egr.msu.edu /erl/ldv/ldv1/ldv1.htm (596 words)

	Frequently Asked Questions on ultrasonic Doppler velocimetry and applications on UDV, UDVF techniques
		In ultrasonic Doppler velocimetry, the shape and lateral sizes of the sampling volumes (measured perpendicularly to the ultrasonic beam axis) are defined by the geometry of the ultrasonic beam.
		LDV measures the component which is perpendicular to the axis of the light beam.
		Ultrasonic Doppler Velocimetry is almost the unique technique that is capable to measure in real time a velocity profile in liquids containing a great number of particles, liquid mud.
	www.signal-processing.com /faq/faq_udv.htm (1062 words)

	Planar Doppler Velocimetry (Site not responding. Last check: 2007-10-20)
		Planar Doppler Velocimetry (PDV), is capable of determining instantaneous, three-dimensional velocity vectors of moving particles or solid material in a laser light sheet everywhere in the field of view.
		These capabilities, in addition to the minimal requirements of PDV on the optical features of the aerosols in the flow, make it particularly attractive as a means of measuring 3‑D velocity vector fields in time dependent flows in large scale wind tunnel facilities.
		In the case of measurements on solid objects where the path of the motion is known, only a single camera system is necessary to obtain the complete velocity along the trajectory and the laser illumination can be volumetric, rather that a light sheet.
	www.metrolaserinc.com /pdvtempl.htm (571 words)

	MEASURING WAVE INDUCED TURBULENCE NEAR STRUCTURES
		The laser Doppler velocimetry is being continually developed in its components but still combined with problems in nonstationary flows.
		Contrary to the laser Doppler velocimetry which is fundamentally a point measurement technique the particle tracking technique and the particle image velocimetry give an impression of the flow characteristics over an entire region of a flow field.
		The laser beam is diffused to a precisely definable, continuously illuminated light sheet by a rotating cylinder.
	www.uni-leipzig.de /~grw/lit/texte_099/21__1994/21_1994_turbulence.htm (1939 words)

	Laser Doppler Velocimetry
		The frequency of this fluctuation is equivalent to the Doppler shift between the incident and scattered light, and is thus proportional to the component of particle velocity which lies in the plane of the two laser beams and is perpendicular to their bisector.
		A laser power source is required, with excellent frequency stability, narrow linewidth, small beam diameter, and a Gaussian beam intensity profile (bright at the center).
		Class IV lasers pose severe eye hazards, yet aligning 2 to 6 beams in a 0.1mm cube of space 21 feet away is not easy when wearing laser goggles.
	www.aiaa.org /tc/amt/techniques/lv.html (637 words)

	TSI Laser Doppler Velocimetry Products
		Laser Doppler velocimetry is a well-proven technique that measures fluid velocity accurately and non-invasively.
		The frequency of the resulting Doppler burst signal is directly proportional to the particle velocity.
		LDV system electronics provide accurate and reliable flow velocity data, including turbulence statistics, from all measurement situations - from simple flows to high speed, flames, combustion, near wall and other low SNR situations.
	www.tsi.com /Category.aspx?Cid=68 (214 words)

	Molecular tagging velocimetry - Wikipedia, the free encyclopedia
		Along its path an optically induced chemical process is initiated, resulting in the creation of a new chemical species or in changing the internal energy state of an existing one.
		The tagged molecule is then excited using a second laser beam, employing a wavelength such that it specifically excites the tagged molecule.
		In Doppler schemes, light quasi-elastically scatters off molecules and the velocity of the molecules convey a Doppler shift to the frequency of the scattered light.
	en.wikipedia.org /wiki/Molecular_tagging_velocimetry (723 words)

	Solids-Solutions: Laser diffraction
		Phase Doppler Velocimetry In laser Doppler velocimetry particles are radiated by two laser beams and the phase shift of the scattered light signals is measured.
		The measurements are performed on a TSI Phase Doppler Particle Analyzer and the report consists of size and velocity distribution results.
		Laser diffraction In laser diffraction (static light scattering) the scattering pattern, obtained from illumination of dispersed particles with a laser beam, contains information about particle size.
	www.solids-solutions.com /r-laser-diffration.html (1371 words)

	ch20.01.03 : Laser Doppler Velocimetry
		Doppler velocimetry can be used before below the knee amputation to predict if the operative wound will heal.
		Moving red blood cells in blood vessels cause a doppler shift of incident light which correlates with the velocity of blood flow.
		• laser doppler velocimeter is used to measure cutaneous blood flow in study region
	www.medal.org /visitor/www/Active/ch20/ch20.01/ch20.01.03.aspx (206 words)

	Electrophoretic mobility and particle size of clays using laser doppler velocimetry-photon correlation spectroscopy
		Laser Doppler velocimetry-photon correlation spectroscopy (LDVPCs) was evaluated for the characterization of clay minerals.
		Electrophoretic mobility and particle size of pure and mixed suspensions of KGa-2 kaolinite and SWY-I bentonite were determined as a function of pH, ionic strength, and suspension concentration ratios.
		Electrophoretic mobility and particle size of clays using laser doppler velocimetry-photon correlation spectroscopy.
	www.uga.edu /srel/Reprint/1807.htm (194 words)

	Amazon.com: Laser Doppler Velocimetry in the Space-Shuttle Main Engine High-Pressure Fuel Turbopump: Books: James D. ... (Site not responding. Last check: 2007-10-20)
		Flow field measurements were obtained, using a the LDV system, in the first-stage rotor end-wall region of the test turbine, at three axial locations and at three depths from the end wall.
		In addition to the laser data, velocity profiles were determined at the first- stage stator inlet and rotor exit planes, using a three-hole pressure probe.
		Both laser and probe data were taken at referred rotational speeds in the range 4815 to 4853 rpm.
	www.amazon.com /Doppler-Velocimetry-Space-Shuttle-High-Pressure-Turbopump/dp/1423563336 (785 words)

	PIV (Site not responding. Last check: 2007-10-20)
		In this method velocity is inferred from the Doppler shift of laser light scattered by small (~ 1 micron) particles moving with the fluid.
		Highly sensitive measurement of the Doppler shift is accomplished by the process of optical heterodyne mixing in which the frequency-shifted light is combined on a photodetector with unshifted light to produce a photo signal that oscillates at the difference of the two frequencies.
		The special advantages of the method are that it does not require calibration, it responds uniquely to a single component of the velocity vector, it can distinguish between positive and negative velocities, it has a good accuracy (~ 0.1%), and it can be used in a variety of transparent fluids.
	www.efluids.com /efluids/pages/products/ldv.htm (186 words)

	Laser Air Motion Sensor
		A Laser Motion Air Sensor (LAMS) based upon laser doppler velocimetry is currently in development for use on
		A prototype, using a single beam, high power 1.5 µm narrow linewidth fiber laser source is being investigated and scheduled for experimental test flights in late 2006.
		The beam quality is within 10 % of modeled output and provides a gaussian beam quality of greater than 95% at the focussing region.
	www.atd.ucar.edu /~dr/page7/page11/page11.html (78 words)

	Relationship between the Parameters of Retinal Circulation Measured by Laser Doppler Velocimetry and a Marker of Early ...
		Relationship between the Parameters of Retinal Circulation Measured by Laser Doppler Velocimetry and a Marker of Early Systemic Atherosclerosis -- Nagaoka et al.
		Laser Doppler measurements were obtained from a temporal retinal
		Laser Doppler measurements of blood velocity in human retinal vessels.
	www.iovs.org /cgi/content/full/46/2/720 (3328 words)

	Mechanical Engineering College of Engineering - University of Massachusetts Dartmouth
		A laser and a computer are used to measure the velocities of the liquid stream.
		The Laser Doppler Velocimeter is the most advanced experimental technique yet devised for measuring fluid velocities.
		Because the Laser Doppler Velocimeter uses laser light to make the velocity measurement the flow is completely unaffected.
	www.umassd.edu /engineering/mne/about/laboratories/velocimetry.cfm (238 words)

	Newport: Photovoltaic Processing, Optical Coherence Tomography, Multiphoton Microscopy & Flat Panel Display ... (Site not responding. Last check: 2007-10-20)
		An economically manufacturable, continuous-wave single-mode quantum-dot laser with spectral width in excess of 20 nm and spectral wavelength between 1200 and 1320 nm has been developed at NL Nanosemiconductor (Dortmund, Germany).
		In vivo cellular visualization of the human retina at micrometer-scale resolution is possible by enhancing Fourier-domain optical-coherence tomography with adaptive optics that compensate for the eye’s optical aberrations.
		The Tsunami® mode-locked Ti:Sapphire laser provides the widest pulse width range, the broadest wavelength coverage and the highest power levels of any ultrafast oscillator on the market.
	lfw.pennnet.com /Newport/opticalcoherencetomography (348 words)

	Laser Doppler Velocimetry (Site not responding. Last check: 2007-10-20)
		Laser Doppler Velocimetry allows a non-invasive measurement of flow velocity by means of the well-known Doppler effect.
		A laser is splitted into two equal-intensity, parallel beams.
		The frequency f of the electric signals produced by a particle moving across the dark fringe pattern with a velocity component V normal to the fringes is given by:
	www.dipmec.unian.it /misure/strumenti/LDA/LDA_en.html (104 words)

	TSI Laser Doppler velocimetry/Accessories
		TSI Laser Power Meters provide a convenient and accurate way to measure Ar ion beam powers, to keep your LDV or PDPA system running at peak efficiency.
		TSI Laser Laser Safety Goggles provide a solid protection from direct and scattered laser beams.
		Turning Mirrors offer the user the convenience of a folded laser beam path, which reduces the footprint of the laser/fiberlight system.
	www.tsi.com /JoinCategories.aspx?Cid1=68&Cid2=165 (224 words)

	A Novel, Nongenomic Action of Estrogen on the Cardiovascular System -- Komesaroff et al. 83 (7): 2313 -- Journal of ...
		The technique employed was that of laser Doppler velocimetry
		Laser Doppler velocimetry is a noninvasive technique for
		1988 Laser Doppler velocimetry in the measurement of neurovascular function.
	jcem.endojournals.org /cgi/content/full/83/7/2313 (2735 words)

	Glenn Research Center - Acoustics Branch
		Rotor/stator interaction noise is the engineering term used to describe noise created this way and is one of many ways that air passing through an engine makes noise.
		Since we cannot see wakes in an airstream like we can see wakes in water, we must use special instrumentation like hotwire probes and Laser Doppler Velocimeters (LDV) to measure the air velocity between the rotor and the stator.
		Hotwire and LDV data are routinely used to validate calculations used to estimate noise from turbofan engines.
	www.grc.nasa.gov /WWW/Acoustics/testing/instrumentation/hotwire.htm (266 words)

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