Localized fluid flow measurements with an He-Ne laser spectrometer

The doppler frequency shift produced in the various diffraction orders of a rotating radial diffraction grating allows such a device to be used as an optical modulator. The theory and performance of such devices is presented.

Optical frequency shifting by means of a rotating diffraction grating

This article describes the use of the Fabry–Perot laser interferometer in the fringe mode to measure velocities of fast‐moving reflecting surfaces, and includes a review of previously published work. We begin by describing the theory of the Doppler shift that applies to these situations, and include an experimental test of whether surface normal direction affects Doppler shift. Formulas are derived for the analysis of the effects of shocked, dispersive, moving transparent media on velocity measurements, including expressions for the velocity of light in a moving medium with moving boundaries. The Fabry–Perot method is compared with other techniques such as the VISAR interferometer. We then describe in detail a standard configuration developed at our facilities, discuss other configurations using optical fibers and more than one cylinder lens, and describe a new laser amplifier developed specifically for velocimetry. Methods of alignment, instrument calibration, surface preparation, and operation are inclu...

Velocimetry of fast surfaces using Fabry–Perot interferometry

An overview of measurements of particle velocities and diameters by laser techniques, with emphasis on thermal plasmas, is given. As far as veloities are concerned, laser-Doppler velocimetry is discussed as a well-established technique. Diameter measurements are much less developed. The state of the art is described and prospective considerations are stressed.

A review on measurements of particle velocities and diameters by laser techniques, with emphasis on thermal plasmas

Oxygen supply in aerobic bioprocesses is of crucial importance. For this reason, this paper presents the oxygen demand of different cells and summarizes experimental and numerical possibilities for the determination of oxygen transfer in bioreactors. The focus lies on the volumetric oxygen mass transfer coefficient (kLa) calculation using computational fluid dynamics and state-of-the-art models for surface-aerated and forced-aerated bioreactors. In addition, experimental methods for the determination of the kLa value and the gas bubble size distribution are presented.

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Oxygen mass transfer in biopharmaceutical processes : numerical and experimental approaches

A differential arrangement using a laser for the measurement of the velocity of moving surfaces is discussed. Configurations of optical velocimeters with diffraction beam-splitters are shown not to be critical on the wavelength stability of a semiconductor laser. Laser meters measuring the velocity and length of rolled stock have been built on the basis of the devices considered.

Optical velocimeters for moving surfaces using gas and semiconductor lasers

An optical method for measuring the geometric radius and velocity of slip of a wheel rolling on a rail is discussed.

Optical control of the radius of a wheel rolling on a rail

The possibility of using an electro-optical frequency modulator with a rotating electric field (MREF) in LDV is discussed. Prototype systems measuring one component of the velocity vector are described. Photographs of the experimental signals obtained are given.

The application of an electro-optical frequency modulator with a rotating electric field in optical Doppler velocimeters

A new optical method for measuring sizes of a dispersed phase (gas bubbles in liquid or drops of liquid in gas) illuminated by a laser “sheet” is substantiated theoretically and experimentally. The accuracy of the method is determined by the resolution of image recording systems. In a test experiment, the error for measuring the sizes of a dispersed phase was under 1%.

A method for measuring the size distribution and the local gas concentration in gas-liquid flows

The use of laser Doppler anemometry methods for determining the radius and slip velocity of rolling wheels is justified theoretically and experimentally. It is demonstrated that these methods allow the wheel radius to be measured with a relative error of 0.05–0.02% for the wheel turning angle of 0.6–4.0°. The slip velocity can be calculated in this case with an error of 20%. The slip velocity of a railroad wheel moving with a velocity of 60 mm/s is found.

P. Ya. Belousov

Papers

Optical velocimeters for moving surfaces using gas and semiconductor lasers

Optical control of the radius of a wheel rolling on a rail

The application of an electro-optical frequency modulator with a rotating electric field in optical Doppler velocimeters

A method for measuring the size distribution and the local gas concentration in gas-liquid flows

Measurement of the radius and slip velocity of a rolling wheel by a laser Doppler anemometer