Turbulence measurements in a jet: Comparing the vectrino and vectrinoii (original) (raw)
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Velocity measurements in a high-Reynolds-number, momentum-conserving, axisymmetric, turbulent jet
Journal of Fluid Mechanics, 1994
The turbulent flow resulting from a top-hat jet exhausting into a large room was investigated. The Reynolds number based on exit conditions was approximately 105. Velocity moments to third order were obtained using flying and stationary hot-wire and burst-mode laser-Doppler anemometry (LDA) techniques. The entire room was fully seeded for the LDA measurements. The measurements are shown to satisfy the differential and integral momentum equations for a round jet in an infinite environment.The results differ substantially from those reported by some earlier investigators, both in the level and shape of the profiles. These differences are attributed to the smaller enclosures used in the earlier works and the recirculation within them. Also, the flying hot-wire and burst-mode LDA measurements made here differ from the stationary wire measurements, especially the higher moments and away from the flow centreline. These differences are attributed to the cross-flow and rectification errors ...
Evaluation of the Acoustic Doppler Velocimeter (ADV) for Turbulence Measurements*
Journal of Atmospheric and Oceanic Technology, 1998
Accuracy of the acoustic Doppler velocimeter (ADV) is evaluated in this paper. Simultaneous measurements of open-channel flow were undertaken in a 17-m flume using an ADV and a laser Doppler velocimeter. Flow velocity records obtained by both instruments are used for estimating the true (''ground truth'') flow characteristics and the noise variances encountered during the experimental runs. The measured values are compared with estimates of the true flow characteristics and values of variance (͗uЈ 2 ͘, ͗wЈ 2 ͘) and covariance (͗uЈwЈ͘) predicted by semiempirical models for open-channel flow. The analysis showed that the ADV sensor can measure mean velocity and Reynolds stress within 1% of the estimated true value. Mean velocities can be obtained at distances less than 1 cm from the boundary, whereas Reynolds stress values obtained at elevations greater than 3 cm above the bottom exhibit a variation that is in agreement with the predictions of the semiempirical models. Closer to the boundary, the measured Reynolds stresses deviate from those predicted by the model, probably due to the size of the ADV sample volume. Turbulence spectra computed using the ADV records agree with theoretical spectra after corrections are applied for the spatial averaging due to the size of the sample volume and a noise floor. The noise variance in ADV velocity records consists of two terms. One is related to the electronic circuitry of the sensor and its ability to resolve phase differences, whereas the second is flow related. The latter noise component dominates at rapid flows. The error in flow measurements due to the former noise term depends on sensor velocity range setting and ranges from Ϯ0.95 to Ϯ3.0 mm s Ϫ1 . Noise due to shear within the sample volume and to Doppler broadening is primarily a function of the turbulence dissipation parameter. Noise variances calculated using spectral analysis and the results of the ground truthing technique are compared with theoretical estimates of noise. * Woods Hole Oceanographic Institution Contribution Number 9300.
1983
The test article was instrumented with 32 static pressure orifices distributed over the afterbody external surface, including four at f = 0 on the aft-facing nozzle lip. Positions of the orifices are given in'Fig. 6. These pressures were measured by the standard Tunnel IT pressure system consisting of five gauged 48-port Scanivalves ® , each with a 15-psid transducer. Four additional static orifices were located within the nozzle plenum chamber. Straingage transducers with a range from 0 to 500 psia were used to measure these pressures. Two copper-constantan thermocouples were located in the gas supply line just upstream of the model to measure gas temperature for computation of nozzle mass flow. Instrumentation for the venturi metering station included one copper-constantan thermocouple and four strain gage pressure transducers. The thermocouple and a 0 to 2,000 psia transducer measured supply gas conditions, and three 0 to 1,000 psia transducers measured venturi throat static pressure. 10 AEDC-TR-82-27 4.0 RESULTS AND DISCUSSION 4.1 AFTERBODY FLOW FIELD 4.1.1 Computational Boundary Measurements Longitudinal LDV surveys were made at r/D = 1.5 and 1.35 to obtain input boundary condition information for future numerical flow-field computations. Data were taken at both r/D positions for each of the 29 x/D stations in the survey. The scatter in the resulting velocity distributions shown in Fig. 9 reflects the estimated 1.5-percent uncertainty in the LDV measurements. Some type of smoothing would be required to condition the data for input into a computational code. 4.1.2 Boundary-Layer Profiles and Flow Separation Radial LDV surveys between the computational boundary and the model surface were made at 13 axial stations along the afterbody. Mean velocity vectors for those over the boattail are illustrated in Fig. 10. Rectangles indicate turbulence intensity levels in the x-and r-directions at that location. The height and width of each rectangle are proportional to the standard deviations (turbulence levels) in the radial and axial velocity measurements, respectively.
Direct measurement of turbulent dissipation rate using dual laser doppler velocimeters
Interim Report Jun Dec 1992 Wright Lab Wright Patterson Afb Oh, 1993
93 12 13 065 NOTICE When Government drawings, specifications, or other data are used for any purpose other than in connection with a definitely Government-related procurement, the United States Government incurs no responsibility or any obligation whatsoever. The fact that the government may have formulated or in any way supplied the said drawings, specifications, or other data, is not to be regarded by implication, or otherwise in any manner construed, as licensing the holder, or any other person or corporation; or as conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto. This report is releasable to the National Technical Information Service (NTIS). At NTIS, it will be available to the general public, including foreign nations. This technical report has been reviewed and is approved for publication.
Measurement of turbulence properties
Analecta Technica Szegedinensia, 2020
The aim of the research is to investigate anisotropic turbulence intensities, id est to investigate the distribution of Reynolds stresses and energy spectra in a square cross-section channel, downstream of a semi-active jet turbulence grid generating anisotropic turbulent airflow. In addition to the semi-active jet turbulence grid, another type of turbulence grid was developed and experimentally investigated. This grid contains vertical, flexible strips of aluminum (in this case, there are no perpendicular (horizontal) grid elements), which vibrate at a frequency depending on the velocity of the main airflow. Besides the investigation of the velocity- and turbulence intensity distributions, another main objective of the research is to measure the von Kármán energy spectrum when the turbulence cannot be considered isotropic. This aspiration of ours is justified by the knowledge gap present in the literature in this specific field. Monin has carried out a theoretical study to extend a...
Fluids
Flow mapping around bridge piers is crucial in estimating scour development potential under different flow conditions. The reliable measurement of turbulence and the estimation of Reynolds stress can be achieved on scaled models under controlled laboratory experiments using high-frequency Acoustic Doppler Velocimeter Profilers (ADVP) for flow measurement. The aim of this paper was to obtain operation parameters for an array of Vectrino Profilers for turbulent flow field measurement to reliably measure the flow field around bridge piers. Laboratory experiments were conducted on a scaled river model set up in an open channel hydraulic flume. Flow field data were measured on three characteristic profiles, each containing five measurement points collected by ADVPs configured as an array of two instruments. The determination of the operation parameters was done as a two-step process—calibration through the flume’s pump flow rate and verification with Acoustic Doppler Current Profiler Rio...
Optical Measurements of Jet Turbulence
The eventual aim of this project is to establish the mechanism of jet noise generation in hot and cold supersonic jets, using the remote optical Crossed Beam Schlieren Method. The work reviewed in this report covers the period October 1969 to October, 1970. During this period the remote Crossed Beam Schlieren Apparatus was built and its performance assessed on a 1 inch dia. cold free air jet run at both subsonic and supersonic speeds. In order to check the viability of the fundamental crossed beam Schlieren theory, an extensive survey of the cold subsonic jet was undertaken; the supersonic programme was initiated during the latter part of the period. The results verify the suitability of the system to remotely extract fundamental turbulence information and it appears that little difffculty should be encountered on applying the apparatus to the high temperature jet measurements programme to follow.
Jet Noise Turbulence Measurements
This paper describes hot-wire anemometer measurements made in a low speed air jet and their use to model jet mixing noise using Lighthill’s acoustic analogy evaluated in a fixed frame of reference. The measurements include second and fourth order two-point space-time correlations for the axial velocity, associated cross-spectra and spectral length scales of the axial and lateral velocity components. The two-point measurements are made in three orthogonal axis about a mid point in the mixing layer and for different Strouhal numbers, thereby avoiding the customary assumption of separation of space and time variables. Predicted fixed frame convective amplification is compared with acoustic measurements made specifically for this purpose.
Measurements of Turbulent Flows
Springer eBooks, 2007
An understanding of turbulence, with its complex spatio-temporal structure, remains elusive. Ideally, an instrument to study the dynamics of turbulent flows would be capable of resolving the smallest relevant spatial and temporal scales in three dimensions. This dissertation details the development of a new optical measurement technique, three-dimensional, long-distance, high-speed micro particle image velocimetry (3-D LHµPIV), and its application to two types of turbulent flow. This technique uses three cameras to simultaneously locally measure all three components of the velocity and all nine velocity gradients. Bibliography vi LIST OF FIGURES 2.1 a) Three laser sheets illuminate three faces of a cubical volume within the flow. Each camera sees a two-dimensional particle field on one of the three faces. The fields of view for the three cameras are offset from the vertex of the cube. Particles within the cube and on the remaining three faces are not visualized. b) After being broken into subsections and digitally analyzed, each face yields an array of twodimensional velocity vectors to be fit to a three-dimensional model.. 2.2 Sample camera image of 1 µm polystyrene spheres suspended in the flow. The particles are illuminated by a laser sheet 0.018 cm thick in a plane perpendicular to the viewing angle. The resolution of the image is 240×210 pixels, corresponding to a region of flow 0.11×0.10 cm. Approximately 450 particles are visible in this image.. .. .. . 2.3 Cylindrical converging lenses are used to create laser sheets. A beam passed through the lens narrows to a thin waist before expanding again.