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Showing papers on "Turbulence published in 1968"


Journal ArticleDOI
TL;DR: In this paper, the authors discuss the solar wind magnetic field power spectra and plasma velocity, discussing turbulence, viscosity and dissipation, and discuss the effect of solar wind energy on the environment.
Abstract: Solar wind magnetic field power spectra and plasma velocity, discussing turbulence, viscosity and dissipation

819 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured the local pressure and skin friction distribution around a cylinder and calculated the total drag, the pressure drag and the friction drag, which can be used to define three states of the flow: the subcritical flow, where the boundary layer separates laminarly; the critical flow, in which a separation bubble, followed by a turbulent reattachment, occurs; and the supercritical flow where an immediate transition from the laminars to the turbulent boundary layer is observed at a critical distance from the stagnation point.
Abstract: In a large range of Reynolds numbers, 6 × 104 < Re < 5 × 106, the flow around single cylinders with smooth surfaces has been investigated. The high values of the Reynolds numbers were obtained in a test channel which could be pressurized up to 40 bar of static pressure. New experiments were performed to measure the local pressure and skin friction distribution around the cylinder. From these results the total drag, the pressure drag and the friction drag were calculated. By means of the skin friction distribution the position of the separation points, separation bubbles or transition points can be localized. These data allow one to define three states of the flow: the subcritical flow, where the boundary layer separates laminarly; the critical flow, in which a separation bubble, followed by a turbulent reattachment, occurs; and the supercritical flow, where an immediate transition from the laminar to the turbulent boundary layer is observed at a critical distance from the stagnation point. According to the total drag coefficient the values found in this paper connect the subcritical region represented by the measurements of Wieselsberger (1923) and Fage & Warsap (1930) with the supercritical range in which Roshko (1961) carried out his experiments.

670 citations


Journal ArticleDOI
TL;DR: In this paper, a diffusion approximation to inertial energy transfer in two-dimensional isotropic turbulence is derived in such a way that energy and squared vorticity are conserved.
Abstract: A diffusion approximation to inertial energy transfer in two‐dimensional isotropic turbulence is derived in such a way that energy and squared vorticity are conserved. The −53 and −3 power inertial ranges are predicted.

524 citations


Journal ArticleDOI
19 Apr 1968-Science
TL;DR: The observed critical parameters indicate that a laminar flow in the core, due to the earth's precession, would have weak hydrodynamic instabilities at most, but that finite-amplitude hydromagnetic instability could lead to fully turbulent flow.
Abstract: I have proposed that the precessional torques acting on the earth can sustain a turbulent hydromagnetic flow in the molten core. A gross balance of the Coriolis force, the Lorentz force, and the precessional force in the core fluid provided estimates of the fluid velocity and the interior magnetic field characteristic of such flow. Then these numbers and a balance of the processes responsible for the decay and regeneration of the magnetic field provided an estimate of the magnetic field external to the core. This external field is in keeping with the observations, but its value is dependent upon the speculative value for the electrical conductivity of core material. The proposal that turbulent flow due to precession can occur in the core was tested in a study of nonmagnetic laboratory flows induced by the steady precession of fluid-filled rotating spheroids. It was found that these flows exhibit both small wavelike instabilities and violent finite-amplitude instability to turbulent motion above critical values of the precession rate. The observed critical parameters indicate that a laminar flow in the core, due to the earth9s precession, would have weak hydrodynamic instabilities at most, but that finite-amplitude hydromagnetic instability could lead to fully turbulent flow.

442 citations


Journal ArticleDOI
TL;DR: In this article, the rate of mixing across a density interface between two layers of liquid has been measured in a laboratory experiment which allows a direct comparison between heat and salinity transports over the same range of density differences.
Abstract: The rate of mixing across a density interface between two layers of liquid has been measured in a laboratory experiment which allows a direct comparison between heat and salinity transports over the same range of density differences. Low Reynolds number turbulence was produced by stirring mechanically at a fixed distance from the interface, either in one or in both layers, and the results for these two sets of experiments are also compared. The measurements cover a factor of two in stirring rate and twenty in density. Over this range of conditions the ratio of entrainment velocity to stirring velocity can be expressed as functions of an overall Richardson number Ri, and in this form the results of the one and two stirred layer experiments are indistinguishable from one another. For density differences produced by heat alone, the functional dependence is close to Ri−1 except at small values of Ri where it approaches a finite limit. For experiments with a salinity difference across the interface, the mixing rate is the same as in the heat experiments at low values of Ri, but falls progressively below this as Ri is increased, with the approximate form .An interpretation of these results has been attempted, using a dimensional analysis and qualitative mechanistic arguments about the nature of the motion. The Ri−1 dependence implies a rate of change of potential energy proportional to the rate of working by the stirrer. The decreased mixing rates for salt have been attributed to a slower rate of incorporation of an entrained element into its surroundings by diffusion, which increases the tendency for it to return to the interface and dissipate energy in wave-like motions.

305 citations


Journal ArticleDOI
TL;DR: In this article, the authors derived expressions for turbulence spectra measured with a single hot wire and wires in an X-array, and applied them to the problem of measurement of spectra at small scales.
Abstract: Expressions are derived for turbulence spectra measured with a single hot wire and wires in an X-array, and are applied to the problem of measurement of spectra at small scales. Isotropic turbulence and Pao's form for the three-dimensional spectrum are assumed. Calculated curves for one-dimensional spectra measured with a single wire and an X-array are presented. Experimental data in good agreement with the single wire calculations are shown. The calculations show that both one-dimensional spectra measured with the X-array are contaminated by crosstalk from the other component. The effect is more serious for the longitudinal spectrum and depends on array geometry and the Kolmogorov microscale.

285 citations


Journal ArticleDOI
TL;DR: In this article, a study of the noise produced by turbulent premixed flames stabilized on open burners is described, and it is shown that such flames may be represented acoustically as a collection of monopole sound sources in the combustion zone.
Abstract: A study of the noise produced by turbulent premixed flames stabilized on open burners is described. It is shown that such flames may be represented acoustically as a collection of monopole sound sources in the combustion zone. The radiated sound pressure is dependent on the rate of change of the rate of increase of volume of the gas during combustion, which varies owing to the turbulence in the flow. The rate of volume increase is proportional to the rate of consumption of combustible gas mixture in the flame. To measure this quantity, an optical technique has been developed which relies on observations of changes in the intensity of emission from the free radicals C 2 or CH generated in the reaction zone. Good quantitative agreement is obtained between the radiated sound pressures calculated from these intensity measurements and the values recorded simultaneously with a microphone. A correlation observed between the mean emission intensities of C 2 and CH radicals and the total flow rate of combustible gas mixture both in the laminar and turbulent flames, and in their transition region, supports the wrinkled laminar flame concept of turbulent flame propagation.

261 citations


Journal ArticleDOI
TL;DR: In this article, a study has been made of the varicose instability of an axisymmetrical jet with a velocity distribution radially uniform at the nozzle mouth except for a laminar boundary layer at the wall.
Abstract: A study has been made of the varicose instability of an axisymmetrical jet with a velocity distribution radially uniform at the nozzle mouth except for a laminar boundary layer at the wall. The evolutionary phenomena of instability, such as the rolling up of the cylindrical vortex layer into ring vortices, the coalescence of ring vortex pairs, and the eventual disintegration into turbulent eddies, have been investigated as a function of the Reynolds number using smoke photography, stroboscopic observation, and the light-scatter technique.Emphasis has been placed on the wavelength with maximum growth rate. The jet is highly sensitive to sound and the effects of several types of acoustic excitation, including pure tones, have been determined.

241 citations


Journal ArticleDOI
TL;DR: In this article, the authors described the occurrence of instability, its nature, and the subsequent transition to turbulence in a laminar accelerating flow in a closed horizontal tube containing a stratified fluid.
Abstract: When the end of a long closed horizontal tube containing a stratified fluid is raised, a laminar accelerating flow begins. The flow is two-dimensional in the central portion of the tube, and, in this region, it is predictable, at least until the onset of instability. The occurrence of instability, its nature, and the subsequent transition to turbulence, are described qualitatively. The apparatus may be used for the study of a variety of other internal hydraulic phenomena with applications to meteorology and oceanography.

238 citations


Journal ArticleDOI
TL;DR: In this article, a packed bed model has been adopted to develop a general correlation applicable to the flow of Newtonian fluids through all types of woven metal screens, which is used to derive a viscous resistance coefficient α = 8.61 and an inertial resistance coefficient β = 0.52.
Abstract: A packed bed model has been adopted to develop a general correlation applicable to the flow of Newtonian fluids through all types of woven metal screens. Both of the main theoretical approaches to studying pressure drop in packed systems have been used by visualizing the screen as a collection of submerged objects with surface area to unit volume ratio a for laminar flow, and as a bundle of tubes of diameter D for turbulent flow. In the usual manner viscous and inertial energy losses are added to give an expression for the total pressure loss. Rearrangement of the general equation to the form of a friction factor yields a unique definition of the Reynolds number for screens NRe = ρu/μa2D. Procedures are described for collection of pressure drop-velocity data for the flow of nitrogen and helium through plain square, full twill, fourdrinier, plain dutch, and twilled dutch weaves. The data are used to derive a viscous resistance coefficient α = 8.61 and an inertial resistance coefficient β = 0.52. The validity of the correlation equation is tested by using additional data from the literature. The correlation successfully predicts pressure drop for a Reynolds number range of 0.1 to 1,000, void fractions from 0.35 to 0.76, screen pore diameters from 5 to 550 μ, mesh sizes from 30 to 2,400 wires/in., and surface area to unit volume ratios from 1,200 to 29,000 ft.−1.

228 citations


Journal ArticleDOI
TL;DR: In this paper, the skewness and kurtosis of ∂u/∂x-type signals were calculated and the small-scale structure of turbulence may be modeled as vortex tubes of diameter η, which are stretched by eddies of scale λ.
Abstract: The small‐scale structure of turbulence may be modeled as vortex tubes of diameter η, which are stretched by eddies of scale λ. The skewness and kurtosis of ∂u/∂x‐type signals are calculated.


Journal ArticleDOI
TL;DR: In this paper, Dokl. Akad. Nauk SSSR 30, 299 (1941), Submitted originally December 28, 1940, and originally published December 14, 1940.
Abstract: Reprinted from Dokl. Akad. Nauk SSSR 30, 299 (1941), Submitted originally December 28, 1940.

Journal ArticleDOI
TL;DR: In this paper, the authors measured atmospheric turbulence recently measured at various heights and sites under a variety of stability conditions, and compared the results with the Kolmogorov hypothesis for the inertial sub-range.
Abstract: Spectra of atmospheric turbulence recently measured at various heights and sites under a variety of stability conditions have been analysed and compared. The results are: (i)In regions over which the spectra obey −5/3 power laws, the ratio of the lateral to the longitudinal spectra shows fair agreement with the 4/3 ratio predicted by the Kolmogorov hypothesis for the inertial sub-range. The vertical-longitudinal ratio has a similar tendency. (ii)Dissipation rates computed from the longitudinal spectra seem to be consistent with the hypothesis that dissipation is balanced by the total production of mechanical and convective turbulent energy, provided that the turbulence is in equilibrium. In transition from rough to smooth terrain, dissipation exceeds the other terms. (iii)Vertical-velocity spectra obey Monin-Obukhov similarity theory up to a height of about 50 m. Their shapes are reasonably uniform, the major change with stability being a change of scale of the wave number axis, i.e., any characteristic nondimensional wave number is a function of z/L only. This function appears to be the same as the relation between the normalized dissipation and z/L. These results are consistent with previously measured Kolmogorov constants and with measured ratios of standard deviation of vertical velocity to friction velocity. Up to about a height of 50 m the wavelengths of the maxima of the logarithmic spectra increase linearly with height and more slowly thereafter, up to about 300 m. The spectra in stable air above 50 m suggest the existence of a buoyant sub-range. (iv)Longitudinal spectra do not obey similarity theory in a number of ways. The wavelengths do not scale with height, and there may be differences between sites when the spectra are plotted in similarity coordinates. (v)Spectra over the sea seem to have relatively more energy at low frequencies than those over land.

Journal ArticleDOI
TL;DR: In this article, it is argued that Reynolds stress evolves in a continuously changing mean field according to a viscoelastic constitutive law, relating stress to deformation history by means of a scalar memory function.
Abstract: A number of shear-flow phenomena can be explained qualitatively if turbulence is regarded as a continuous viscoelastic medium with respect to its action on a mean field. Conditions are sought under which the analogy is quantitative, and it is found that the turbulence must be fine-grained and the mean field weak. For geometrical convenience the turbulence is assumed to be nearly homogeneous and isotropic so that body forces are required to maintain it. The turbulence is found to respond initially to an arbitrary deformation as an elastic medium, in which Reynolds stress is linearly proportional to strain. Three processes that cause the resulting Reynolds stress to relax are distinguished: viscous diffusion, body-force agitation and non-linear scrambling. It is argued that, regardless of which process dominates, Reynolds stress evolves in a continuously changing mean field according to a viscoelastic constitutive law, relating stress to deformation history by means of a scalar memory function. The argument is carried through analytically for weak turbulence, in which non-linear scrambling is negligible, and the memory function is computed in terms of the wave-number-frequency spectrum of the background turbulence. In the course of the analysis, a new type of Reynolds stress arises related to the passage of the turbulence through its sustaining environment of body forces. It is found that the mean field must be surprisingly weak for this ‘translation stress’ to be negligible. Applications of the viscoelasticity theory of turbulent shear flow are discussed in which body forces and therefore translation stress are absent.

Journal ArticleDOI
TL;DR: In this article, the effect of Mach number on mixing lengths and kinematic eddy viscosities in the turbulent, flat-plate boundary layer has been evaluated using the generalized velocities suggested by Van Driest, using measured boundary-layer profiles, for a range of Reynolds numbers and Mach numbers from 0 to 5, on a single curve.
Abstract: The effect of Mach number on the mixing lengths and kinematic eddy viscosities in the turbulent, flat-plate boundary layer has been evaluated. Using the generalized velocities suggested by Van Driest, it was possible to correlate measured boundary-layer profiles, for a range of Reynolds numbers and Mach numbers from 0 to 5, on a single curve. From this correlation, velocity profiles at desired Reynolds and Mach numbers were generated, and the boundary-layer equations of motion were then integrated, using these profiles, to obtain the local turbulent shear stress. The local mixing lengths and kinematic eddy viscosities were subsequently evaluated from the computed shear-stress distribution. The results of this study show that within the Mach number range of 0 to 5 the effect of compressibility on the normalized, turbulent shear stress and mixing length distribution is quite small, in keeping with Morkovin's hypothesis concerning the structure of compressible turbulent shear flow. The kinematic eddy viscosity displays a more pronounced sensitivity to Mach number, but a normalizing length scale can be found such that this sensitivity is all but eliminated.

Journal ArticleDOI
TL;DR: In this paper, temperature and velocity fluctuations have been recorded in the open sea and in a tidal channel, and power spectra have been determined from the records, and the one-dimensional spectra of temperature fluctuations are found to have an inertial subrange.
Abstract: : Temperature and velocity fluctuations have been recorded in the open sea and in a tidal channel, and power spectra have been determined from the records. The one-dimensional spectra of temperature fluctuations are found to have an inertial subrange. At larger wave-numbers the data can be fitted by Batchelor's spectrum function for the viscous-convective range. The spectra are inconsistent with the form proposed by Pao for the vicsous-convective range. Estimates are given for the constants in Batchelor's spectrum function, but these depend upon knowledge of the rate of dissipation of kinetic energy, which is determined from the velocity spectra. There is doubt about the validity of some of the velocity spectra, and in other cases there is reason to suspect that the turbulence is not locally isotropic. (Author)

Journal ArticleDOI
TL;DR: In this paper, a criterion for the onset of reverse transition has been deduced in terms of the mean shear-stress gradient in the wall region of the flow, which is quite general applicable to all fully turbulent shear flows.
Abstract: It has been shown experimentally that quite large departures occur from the universal inner-law velocity distribution in the presence of severe favourable pressure gradients in turbulent boundary layers and that these departures are associated with the tendency for the turbulent boundary layer to revert to a laminar state. From the measurements a criterion for the onset of reverse transition has been deduced in terms of the mean shear-stress gradient in the wall region of the flow. Experiments in fully developed pipe and channel flows suggest that the proposed criterion may be quite generally applicable to all fully turbulent shear flows.

Journal ArticleDOI
TL;DR: In this paper, the relation of the increased resistance of air flowing over a liquid surface to the properties of the waves has been studied and the relationship of this increased resistance to the wave properties has been shown to increase with the square of the gas velocity.
Abstract: Air flowing over a liquid surface encounters an increased resistance if waves are present. The relation of this increased resistance to the properties of the waves has been studied. Air and a liquid flowed co-currently in an enclosed channel which is 12 in. wide and 1 in. high and which is long enough so that flow in the air and the liquid and the interfacial structure are fully developed. The drag on interfaces with three-dimensional wave structures was found to increase with the square of the gas velocity and to depend more on the height of the waves than on other parameters characterizing the interface. The ratio of the equivalent sand roughness to the root-mean-square of the fluctuations in the height of the liquid film is approximately equal to 3 √2. The velocity profiles in the gas were found to be different from what has been reported for flows over sand roughened surfaces.

Journal ArticleDOI
TL;DR: Experiments to determine film cooling with air injection through holes into turbulent air boundary layer on flat plate are described in this paper, where a flat plate is used as a flat surface.
Abstract: Experiments to determine film cooling with air injection through holes into turbulent air boundary layer on flat plate

Journal ArticleDOI
TL;DR: In this article, two kinds of distorting ducts are used to produce the uniform mean strain applied to initially nearly isotropic grid turbulence, and the results differ from Townsend's in that (1) a considerably higher degree of anisotropy is achieved, Townsend's measure of an isotropy attaining values up to 0.6, rather than the maximum of 0.42 he found; (2) there is no evidence that an equilibrium structure is attained; and (3) the strained turbulence rapidly becomes less anisotropic when the straining ceases.
Abstract: : The experiments extend those of Townsend which form the basis of his model of free turbulence. Here straining is carried to a strain ratio of 6:1, while Townsend's straining went only to 4:1. Two kinds of distorting ducts are used to produce the uniform mean strain applied to initially nearly isotropic grid turbulence. The results differ from Townsend's in that (1) a considerably higher degree of anisotropy is achieved, Townsend's measure of anisotropy attaining values up to 0.6, rather than the maximum of 0.42 he found; (2) there is no evidence that an equilibrium structure is attained; and (3) the strained turbulence rapidly becomes less anisotropic when the straining ceases. It is found to be possible to predict the variation of the total turbulence energy using rapid-distortion theory with a correction for decay. However, the individual components cannot be accurately predicted in this way. (Author)

Journal ArticleDOI
TL;DR: In this article, a model forest canopy was designed to simulate the meteorological characteristics of typical live forests and measurements were made of velocity, turbulence, drag, and gaseous plume spread within the simulated canopy.
Abstract: A model forest canopy was designed to simulate the meteorological characteristics of typical live forests. Measurements were made of velocity, turbulence, drag, and gaseous plume spread within the simulated canopy. The resulting data compares favorably with prototype field measurements in all cases. Several new aspects of the flow at the upwind edge of a forest are displayed.



Journal ArticleDOI
TL;DR: In this paper, a hot film flowmeter, a thin film resistance thermometer and several thermistors were mounted on a submarine and used to study turbulence and temperature microstructure in the open sea.
Abstract: : The purpose of the paper is to describe some observations of small-scale velocity and temperature fluctuations in the upper layers of the ocean. The results are largely qualitative and the measurements were made in only one location at one time of the year so they are not adequate to provide the basis for a detailed heat and momentum transport model. A hot film flowmeter, a thin film resistance thermometer and several thermistors were mounted on a submarine and used to study turbulence and temperature microstructure in the open sea. The surface layer is found to be continuously turbulent and patches of turbulence have been found in and below the main ocean thermocline. (Author)

Journal ArticleDOI
TL;DR: In this paper, it was found experimentally that the turbulent pipe flow through a mitred, right-angle bend produces a downstream secondary circulation which does not conform to the twin-circulatory flow usually to be found in pipe bends.
Abstract: It has been found experimentally that the turbulent pipe flow through a mitred, right-angle bend produces a downstream secondary circulation which does not conform to the twin-circulatory flow usually to be found in pipe bends. The secondary flow is dominated by a single circulation about the axis in either a clockwise or an anticlockwise sense, between which it switches abruptly at a low, random frequency. The phenomenon is explained in terms of the asymmetry of the inner wall separation and the turbulent axial circulation generated in the upstream flow.

Journal ArticleDOI
TL;DR: In this paper, a general formulation for statistically inhomogeneous and anistropic processes using the Wiener stochastic expansion is presented, which can be used for non-linear non-Gaussian processes such as many turbulent fluid flows.
Abstract: The turbulence problem is formulated using the Wiener stochastic expansion. The expansion is useful for processes which are in some sense nearly normal, and can be used for non-linear non-Gaussian processes such as many turbulent fluid flows. Here we present the general formulation for statistically inhomogeneous and anistropic processes.The transfer term in the energy equation, or equivalently the third-order velocity correlation, forms a sensitive measure of the amount of non-Gaussianity present in real fluid flows. Experimental evidence shows that in many flows this component is small compared with the Gaussian part. It is shown that a homogeneous and isotropic flow which has but a small non-Gaussian part possesses a distribution at one point which is Gaussian to terms of second order. The experiments suggest that immediately behind a grid in a wind tunnel the flow is very nearly normal. The non-Gaussian part grows at a moderate rate, at least within the range of distance downstream (or decay time) available in the usual experiments. This growth is probably due to the relative increase in the amount of energy in the smallest eddies, which are non-normal.A necessary criterion for the validity of the zero-fourth-cumulant approximation is suggested: the transfer term in dimensionless form should be small. It is shown that calculations using the zero-fourth-cumulant approximation have given negative energy spectra when this condition is violated, probably for the reason that the process is no longer nearly Gaussian. However, even when this condition is fulfilled, it is shown that that approximation must be corrected.It is suggested that the present theory is valid for quite large times of decay if initial energy spectra are chosen which are not too far from the actual physical values for fluid in turbulent flow. Equations are given for the next-higher-order term in a nearly normal approximation. The expansion is also used in § 6 to describe turbulent mixing problems and is compared with the zero-fourth-cumulant approximation for these problems. Computational results are presented in § 7 and compared with experiments by Stewart and Townsend.

Journal ArticleDOI
TL;DR: In this article, the Doppler shifts in the frequency of laser light scattered by small particles in the water were measured using an optical hetrodyne technique to measure the shift in frequencies.
Abstract: The local mean values and fluctuations of the velocity of water in turbulent flow through a tube have been determined from the Doppler shifts in the frequency of laser light scattered by small particles in the water. An optical hetrodyne technique was used to measure the shift in frequencies. The limited lifetime of the Doppler shifted signals, due to the finite time of passage of the scattering particles through the laser beam, causes broadening of the frequency spectra representing the fluctuations in turbulent velocity. This broadening, which is analogous to the Doppler radar ambiguity, was investigated with laminar flow and was allowed for in interpreting the spectra observed with turbulent flow. The optics were chosen so that the coherence limits were at all times greater than the beam diameter and did not further shorten the lifetimes of the Doppler signals. The root mean squares of the fluctuations in velocity, calculated from the observed spectra, are in agreement with corresponding data obtained by hot wire anemometry.

Journal ArticleDOI
TL;DR: In this paper, a turbulent eddy viscosity model is formulated for the shear stress scaling scaling of the dissipation integral in the mechanical energy equation, and a simple conservation model is presented to relate the viscous sublayer after expansion to the initial boundary layer ahead of the step.
Abstract: The integral near- wake analysis of Reeves and Lees developed for supersonic laminar base flows with viscous-inviscid interaction is extended to the case of fully turbulent separated adiabatic flow behind a rearward-facin g step at supersonic speeds. A turbulent eddy viscosity model is formulated for the shear stress scaling of the dissipation integral in the mechanical energy equation. It is shown that the eddy viscosity can be described simply by one incompressible constant (valid for both shear layers and wakes) and one reference density pr. Using a compressibility transformation, theoretical solutions for the spreading rates of free shear layers are found to agree with experiment when the reference density is chosen to be the centerline density for the wake flow. The wake flow solution, uniquely determined by the wake critical point, is joined to the body through a turbulent free shear layer mixing solution. A simple conservation model is presented to relate the viscous sublayer after expansion to the initial boundary layer ahead of the step. For freestream Mach numbers MI < 2.3, where lip shock effects may be neglected, the integral theory is found to give good estimates for the length scales and centerline pressure variations measured experimentally for both wake flows and step flows (where reattachment is to a solid surface). b C f f'M h

Journal ArticleDOI
TL;DR: In this paper, a method for the measurement of turbulence level and turbulent shearing stress by a single, continuously rotated, hot wire anemometer is presented, where emphasis is placed on the simplicity in the measuring procedure and on the accuracy in the results obtained.
Abstract: A convenient method for the measurement of turbulence level and turbulent shearing stress (u2¯,v2¯,uv¯) by a single, continuously rotated, hot wire anemometer is presented. Emphasis is placed on the simplicity in the measuring procedure and on the accuracy in the results obtained. When comparing the results of Reynolds stress measurement in fully developed turbulent pipe flow, good agreement was found with values calculated from the measured pressure drop (skin friction coefficient) along the pipe.