Velocity, intermittency, and turbulence intensity measurements in the boundary layer of an accelerated flow
Hot-wire anemometer for velocity, intermittancy, and turbulence intensity measurements in boundary layer of accelerated flow
Boldman, D. R.↗
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Effects of free stream turbulence intensity and integral length scale on heat transfer from a circular cylinder in crossflow
A model has been proposed for the momentum eddy diffusivity induced by free stream turbulence intensity and integral length scale. The eddy diffusivity model is applied to a cylinder situated in a uniform crossflow in the presence of free stream turbulence. Numerical solution of the governing momentum and energy equations with the proposed eddy diffusivity model yielded results for the skin friction coefficient and the Nusselt number. The numerical predictions of the present work are compared with experimental data and the agreement between the two is seen to be very good.
Gorla, R. S. R.↗
Laser anemometer using a Fabry-Perot interferometer for measuring mean velocity and turbulence intensity along the optical axis in turbomachinery
A technique for measuring a small optical axis velocity component in a flow with a large transverse velocity component is presented. Experimental results are given for a subsonic free jet operating in a laboratory environment, and for a 0.508 meter diameter turbine stator cascade. Satisfactory operation of the instrument was demonstrated in the stator cascade facility with an ambient acoustic noise level during operation of about 105 dB. In addition, the turbulence intensity measured with the interferometer was consistent with previous measurements taken with a fringe type laser anemometer.
Seasholtz, R. G.↗
Turbulence Intensity at Inlet of 80- by 120-Foot Wind Tunnel Caused by Upwind Blockage
In order to estimate the magnitude of turbulence in the National Full-Scale Aerodynamics Complex (NFAC) 80- by 120-Foot Wind Tunnel (80 x 120) caused by buildings located upwind from the 80 x 120 inlet, a 150th-scale study was performed that utilized a nominal two-dimensional blockage placed ahead of the inlet. The distance of the blockage ahead of the inlet was varied. This report describes velocity measurements made in the plane of the 80 x 120 model inlet for the case of zero ambient (atmospheric) wind.
80- by 120-Foot Wind Tunnel↗
Probe shapes that measure time-averaged streamwise momentum and cross-stream turbulence intensity
A method and apparatus for directly measuring the time-averaged streamwise momentum in a turbulent stream use a probe which has total head response which varies as the cosine-squared of the angle of incidence. The probe has a nose with a slight indentation on its front face for providing the desired response. The method of making the probe incorporates unique design features. Another probe may be positioned in a side-by-side relationship to the first probe to provide a direct measurement of the total pressure. The difference between the two pressures yields the sum of the squares of the cross-stream components of the turbulence level.
Rossow, Vernon J.↗
Intense turbulence in the polar mesosphere - Rocket and radar measurements
Two radars respectively operating at 53.5 MHz and 224 MHz have been used to simultaneously measure the polar mesospheric summer echoes (PMSEs) during the launch of a sounding rocket designed to measure the fluctuations in the electron density in the same height range. Some features of the data obtained are consistent with nearly isotropic, intense, meter-scale turbulence on the day of the observations. A dissipation rate is derived from the spectral width of the 53.5 MHz backscatter signal and from the rocket electron density fluctuation data; the diffusive subrange occurs at a wavelength which is a factor of 10 greater than the viscous subrange. This corresponds to a Schmidt number of about 100.
Kelley, M. C.↗
Mesopheric turbulence intensities measured with a HF radar at 35 deg S. Part 2
A theory was developed for extracting turbulence energy dissipation rates from spectra measured with a radar. It is shown that factors apart from turbulence contribute to the observed spectral widths, and that these factors must be considered if accurate estimates of energy dissipation rates are to be obtained. In particular, beam-width broadening and shear broadening are important. The first results obtained with this theory are presented. The rules were obtained using the large HF array at Adelaide, Australia, primarily during the Southern Hemisphere winter of 1981. Results are consistent with rocket measurements of turbulence, with typical values varying between 0.01 and 1/0.2 W kg at 80-90 km altitude.
Hocking, W. K.↗
Transitional Boundary Layers Under the Influence of High Free Stream Turbulence, Intensive Wall Cooling and High Pressure Gradients in Hot Gas Circulation
The requirements for fundamental experimental studies of the influence of free stream turbulence, pressure gradients and wall cooling are discussed. Under turbine-like free stream conditions, comprehensive tests of transitional boundary layers with laminar, reversing and turbulent flow increments were performed to decouple the effects of the parameters and to determine the effects during mutual interaction.
Rued, Klaus↗
Turbulence-intensity Measurements in a Jet of Air Issuing from a Long Tube
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FLOW, MIXED↗
Characteristics of the motions, turbulence intensity, diffusivity, flux of momentum and sensible heat in the upper atmosphere
Analyses of the meteorological rocket data obtained from an experiment conducted at 3-hour intervals at 8 western meridional rocket stations are presented. Large variations in the meridional wind contribute substantially to overall turbulence in the tropical stratosphere. The solar semidiurnal component of wind oscillations in the tropics was observed to be much higher than predicted by theory, often exceeding the magnitude of the diurnal amplitude throughout the stratosphere. The observed value of the solar diurnal amplitude in the stratosphere was in line with theoretical prediction. The solar terdiurnal amplitudes for temperature, meridional and zonal winds were non-negligible and must be considered in any harmonic analysis. Phase angle variation with height was rapid for all harmonics; however, there was general agreement between predicted and observed phase angles. Because of large changes in the mean winds in the mesosphere with season, harmonic determinations are difficult. There appear to be large zonal wind changes even within the same season as mentioned previously. Turbulence diffusivity in the upper stratosphere is greater near the equator than in the mid-latitudes.
Kao, S. K.↗
Seasonal variation of turbulence intensities in the upper mesosphere and lower thermosphere measured by radar techniques
Since February 1985, the 2 MHz narrow beam radar operated by the University of Adelaide in Australia has been used to measure the short term root-mean-square fluctuating velocities of radio wave scatterers in the upper middle atmosphere (80 to 100 km). These measured fluctuations are caused by a mixture of turbulence and gravity waves, and under certain reasonable assumptions the turbulent contribution can be extracted. The results of these measurements were discussed in detail by Hocking (1988). These results are summarized and the data set is extended to include 1987.
Hocking, W. K.↗
Laser Doppler velocimeter measurements of boundary layer velocity and turbulent intensities in Mach 2.5 flow
In recent years, the interest in developing a high-speed civil transport has increased. This has led to an increase in research activity on compressible supersonic flows, in particular the boundary layer. The structure of subsonic boundary layers has been extensively documented using conditional sampling techniques which exploit the knowledge of both u and v velocities. Researchers using these techniques have been able to explore some of the complex three-dimensional motions which are responsible for Reynolds stress production and transport in the boundary layer. As interest in turbulent structure has grown to include supersonic flows, a need for simultaneous multicomponent velocity measurements in these flows has developed. The success of conditional analysis in determining the characteristics of coherent motions and structures in the boundary layer relies on accurate, simultaneous measurement of two instantaneous velocity components.
Sewell, Jesse↗
New aircraft instrument indicates turbulence intensity
System consists of accelerometer, indicator, and necessary electronic circuits for summing and averaging accelerations. Averaging-time feature enables pilot to see large values of accelerations over a short time or smaller accelerations over longer period of time.
Champine, R. A.↗
Laser anemometer using a Fabry-Perot interferometer for measuring mean velocity and turbulence intensity along the optical axis in turbomachinery
Previously announced in STAR as N82-28605
Seasholtz, R. G.↗
A hot-wire method for high-intensity turbulent flows
A measuring technique for determing instantaneous, three-dimensional velocity vectors in highly turbulent flows by means of a 4-sensor hot-wire probe is described. As is well known, the hot-wire signal received in reversing flows cannot uniquely be interpreted. This difficulty is circumvented by tracking the thermal wake of a heated wire. Whenever the approximate flow direction is indicated by a temperature-sensitive wake detector, all components of the instantaneous velocity vector are evaluated by means of a digital data reduction method. Uniqueness of the solution derived from the triple-hot-wire response equations is examined. A first application of the proposed measuring technique in the recirculating flow downstream of a backward-facing step is described.
Mueller, U. R.↗
Flame Propagation in Low-Intensity Turbulence under Microgravity Conditions
The goal of the research is to understand the influences of the hydrodynamic instability on premixed-flame propagation. It is known that coupling between flame and flow-field dynamics in association with the hydrodynamic instability may lead to flame-generated turbulence, flame acceleration and enhancement of burning rates. As a result of such hydrodynamic coupling the transition from initially planar or wrinkled laminar flames to fast turbulent flames or detonations is possible, even when diffusive-thermal effects associated with non-unity reactant Lewis numbers are not destabilizing. It is important to identify methods of suppressing the hydrodynamic instability so as to insure fire safety, particularly in space.
Aldredge, R. C.↗
Turbulence measurements in shock induced flow using hot wire anemometry
Heat transfer measurements over various geometric shapes have been made by immersing models in shock-induced flows. The heat transfer to a body is strongly dependent on the turbulence level of the stream. The interpretation of such heat transfer measurements requires a knowledge of the turbulence intensity. Turbulence intensity measurements, using hot-wire anemometry, have been successfully carried out in shock-induced flows. The experimental procedures for making such measurements and the techniques required are discussed.
Hartung, Lin C.↗
Turbulence measurements in a complex plowfield using a crossed hot-wire
Turbulence was quantified in complex axisymmetric, nonreacting, nonswirling flowfields using a crossed hot-wire anemometer. Mean velocity, turbulence intensities, turbulent viscosity, and Reynolds tree were measured in round free jet and confined jet flowfields. The confined jet, a model of an axisymmetric can combustor, had an expansion ratio D/d=2, an expansion angle of 90 deg, and an axial location increments of 0.5 diameters. The confined jet was studied with and without a contraction nozzle. Free jet measurements validated the experimental technique and data reduction. Results show good agreement with those of previous research. Measurements in the confined jet indicate that the cross hot-wire used cannot handle axial flow reversal and the experimental technique is inadequate for measuring time-mean radial velocity. Other quantities show a high level of comparability.
Mckillop, B. E.↗