3 edition of Using a 3-dimensional laser anemometer to determine mean streamline paterns in a turbulent flow found in the catalog.
Using a 3-dimensional laser anemometer to determine mean streamline paterns in a turbulent flow
by National Aeronautics and Space Administration, Ames Research Center in Moffett Field, Calif
Written in English
|Other titles||Using a three dimensional laser anemometer to determine mean streamline patterns in a turbulent flow.|
|Statement||K.L. Orloff and P.K. Snyder.|
|Series||NASA technical memorandum -- 85948.|
|Contributions||Snyder, P. K., Ames Research Center.|
|The Physical Object|
The liquid-phase turbulent structure and the phase distribution of an air-water, bubbly, upward flow in a circular channel were investigated experimentally. The liquid-phase local flow parameters, such as mean liquid velocity, turbulent intensity and Reynolds stress, were measured, using both one- and two-dimensional hot-film anemometer probes. Anemometer, device for measuring the speed of airflow in the atmosphere, in wind tunnels, and in other gas-flow applications. Most widely used for wind-speed measurements is the revolving-cup electric anemometer, in which the revolving cups drive an electric output of the generator operates an electric meter that is calibrated in wind speed.
To calculate the beam divergence and spot size of the given laser beam. Laser: The term LASER is the acronym for Light Amplification by Stimulated Emission of Radiation. It is a mechanism for emitting electromagnetic radiation via the process of stimulated emission. The laser was the first device capable of amplifying light waves themselves. An anemometer measures the pressure and force of the wind. There are several different types of anemometers: cup or propeller anemometers electronically measure the wind by counting the revolutions per minute; ultrasonic or laser anemometers detect light that is reflected from lasers off air molecules; hot wire anemometers detect wind speed through temperature differences .
Modern laser Doppler anemometer systems incorporate a Bragg cell for frequency shifting of a laser beam, at a frequency of 40 MHz, in order to remove any directional ambiguity. This facility enables regions of positive, zero and negative flow velocities to be clearly identified, the importance of this capability is highlighted in Figure 4. Laser Doppler anemometry is a non-contact optical measurement method to obtain the velocity of a flow (liquid, gas). In the experiment P a laser Doppler anemometer is assembled. A laser beam is split into two parts. Focused back to one spot, the laser beams create an interference pattern.
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Using a 3-dimensional laser anemometer to determine mean streamline patterns in a turbulent flow - NASA/ADS The determination of mean streamline patterns by moving the test point in the direction of the measured velocity is shown to produce cumulative errors that are by: 1.
CONCLUDING REMARKS An algorithm has been presented that can be used with a three-dimensional laser-Doppler anemometry system to determine accurately the mean streamline patterns in a complex, turbulent, three-dimensional flow.
Get this from a library. Using a 3-dimensional laser anemometer to determine mean streamline paterns in a turbulent flow. [Kenneth L Orloff; P K Snyder; Ames Research Center.]. Using a 3-dimensional laser anemometer to determine mean streamline patterns in a turbulent flow.
By K. Orloff and P. Snyder. Abstract. The determination of mean streamline patterns by moving the test point in the direction of the measured velocity is shown to produce cumulative errors that are unacceptable.
A two-dimensional algorithm Author: K. Orloff and P. Snyder. Both mean and fluctuating velocities were measured and use was made of the very fine spatial resolution of the laser anemometer in order to measure velocities very close to a wall. Rolfe et a1' have built a laser anemometer which Cited by: The technique of tracing out a mean flow streamline with a three dimensional laser Doppler anemometer (LDA) is discussed with respect to cumulative, systematic errors that are inherent when the.
Laser Doppler Flow Measurement. The laser doppler anemometer (LDA) is a well-established technique that has been widely used for fluid dynamic measurements in liquids and gases for well over 30 years. The directional sensitivity and non-intrusiveness of LDA make it useful for applications with reversing flow, chemically reacting or high.
Hightlights from laser Doppler anemometer measurements of turbulent flows of a two phase suspension are first described and peculiar features of flow behaviour at.
the laser anemometer data with results from numerical flow analysis codes that assume the flow is steady in the reference frame of the rotor. Each laser anemometer survey consists of axial and tangential velocity component measurements acquired at 50 points from blade to blade at a fixed axial and radial location.
Typical laser Doppler anemometers use two equal-intensity laser beams (split from a single beam) that intersect across the target area at a known angle q, as shown in the schematic below. Given that the laser light has a wavelength l, we would like to find the spacing d of the interference fringes where the combined laser light intensity is zero.
Here is sketch diagram shows the arrangement of a hot wire anemometer used for the measurement fitted with a wheatstone bridge. LASER DOPPLER ANEMOMETER AND ITS APPLICATIONS . It is a very advanced type of anemometer offers the advantage that they do not disturb the flow during the measurement is a optical type of flow meter and it.
A powerful two‐color Laser Doppler Anemometer (LDA) system, with direct digital signal processing has been used to measure accurately the longitudinal and vertical velocity components in two‐dimensional, fully‐developed open‐channel flow over smooth beds.
For a flow whose velocity is to be determine, it is to be noted that the flow should contain small particles to scatter the light. The particle concentration should be very small. Operation of Laser Doppler anemometer.
The laser source sends a beam that is divided by a beam splitter into two beams. The flow structure and the vortex topology were studied in a variety of oncoming flow conditions using flow visualization techniques.
A PIV measurement, which is highly suited to measurements in three-dimensional flows, was used to provide detailed information about the vortex structures in the longitudinal plane x – y and their streamwise. Laser-Doppler anemometer investigations are described in boundary-layer flows along bean leaves and a metal model of plant leaves.
These measurements formed the basis of heat and mass transfer predictions near leaves for a specific leaf position relative to the free stream and with different turbulence properties imposed onto the oncoming flow. Predicting detailed flow properties of a confined, isothermal, and swirling flow field in an axisymmetric sudden expansion combustor is of great importance.
In this regard, the current paper makes use of Artificial Neural Networks to enhance the experimental results obtained using a two-component laser Doppler velocimetry capable of measuring the mean velocity. interference pattern to move at Vs = fs df, and shifts the frequency of the scattered light by fs.
Directional ambiguity is then removed for V > -fsλ/ (2sin(θ/2)). After a burst signal (Figure 3) is detected by the PMT, three different processing schemes can be used to determine fd. A 'counter' processor first isolates the.
A laser-type anemometer is described which measures the mean velocity and velocity fluctuations in turbulent streams. This is a preview of subscription content, log in to check access. Access options. In fact, the laser diode has become by far the most common laser type, with truly massive use throughout telecommunications and data storage (e.g., DVDs, CDs).
In a laser diode, current flow creates charge carriers (electrons and holes) in a p-n junction. These combine and emit light through stimulated emission. The flow past a two-dimensional cylinder is one of the most studied of aerodynamics. It is relevant to many engineering applications. The flow pattern and the drag on a cylinder are functions of the Reynolds number Re D = U ¥ D/n, based on the cylinder diameter Dand the undisturbed free-stream velocity U ¥.
Recall that the Reynolds number. A. Ideal flow model of flow past a circular cylinder In AOE you studied irrotational incompressible flow past a circular cylinder without circulation (see Bertin,section ).
Such a flow can be generated by adding a uniform flow, in the positive xdirection to a doublet at the origin directed in the negative xdirection.A series of flow fields generated by a turbulent methane/air stratified swirl burner are investigated using laser Doppler anemometer (LDA).
The LDA provides flow field measurements with comparatively high temporal resolutions. However, processingof the power spectral energy.Laser Doppler velocimetry, also known as laser Doppler anemometry, is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows or the linear or vibratory motion of opaque, reflecting surfaces.
The measurement with laser Doppler anemometry is absolute and linear with velocity and requires no pre-calibration.