Mean Velocity Vector Research Articles

Equatorial Upwelling in the Central Pacific Estimated from Moored Velocity Profilers

Horizontal divergence and vertical velocity (w) are estimated at 0°, 140°W using an array of five subsurface moored acoustic Doppler current profilers deployed from May 1990 to June 1991 during the Tropical Instability Wave Experiment. The record-length mean flow is divergent within the near-surface region and convergent within the thermocline, with maximum convergence located at the high speed core of the Equatorial Undercurrent (EUC). This pattern of divergence results in upwelling at and above the EUC core (with maximum value of 2.3 × 10−5 m s−1 located at 60-m depth) and downwelling below the core. The relative slopes in the zonal plane between the mean velocity vectors and the isotherms suggest a net diffusive heat flux. Assuming that this occurs vertically, an entrainment velocity parameterization provides an estimate of the “diapycnal vertical velocity” profile that reverses sign at the EUC core depth. Several kinematical and dynamical consistency checks are developed on both the time-dependent and the mean motions to supplement a discussion of errors for the mean w profile. The time-dependent fluctuations in w may be an order of magnitude larger than the mean values, and on synoptic timescales w may be directed either up or down over the entire upper 250-m region sampled.

Using a Broadband ADCP in a Tidal Channel. Part I: Mean Flow and Shear

This paper discusses the principles of measuring the mean velocity and its vertical shear in a turbulent flow using an acoustic Doppler current profiler (ADCP), and presents an analysis of data gathered in a tidal channel. The assumption of horizontal homogeneity of the first moments is fundamental to the derivation of the mean velocity vector because the velocity is never homogeneous over the span of the beams in a turbulent flow. Two tests of this assumption are developed—a comparison of the mean error velocity against its standard deviation and against the mean speed. The fraction of the samples that pass these tests increases with increasing spatial averaging and exceeds 95% for distances longer than 55 beam separations. The statistical uncertainty of the velocity and shear vector, averaged over 10 min and longer, stems from turbulent fluctuations rather than Doppler noise. Estimation of the vertical velocity requires a correction for the bias in the measured tilt. The mean velocity and shear estimates from this natural tidal channel show more complex depth‐time variations than found in idealized one-dimensional channel flow, which seldom occurs in nature. The ADCP measurements reveal the secondary circulation, bursts of up- and downwelling, shear reversals, and transverse velocity shear.

Computational study of natural ventilation

Abstract The object of the present work is to use computational fluid dynamics (CFD) to study the ventilation properties for a room with different opening configurations. The finite volume method is used to solve the basic equations of mass and momentum conservation in the primitive form together with the two-equation turbulence model. The model is verified by comparing the results for steady two-dimensional flow around a long square cylinder immersed in the atmospheric boundary layer with experimental values. Internal flows are then simulated in a single-room building with different opening configurations. Six examples are considered for internal flows. The results include mean velocity vectors, stream lines, and pressure distribution around the building as well as the mean velocity vectors, streamlines and turbulent eddy viscosity inside the room are considered. The placement of openings in relation to one another may enhance or reduce mean velocity at certain locations inside the room. The model can help in assigning comfortable locations for humans inside the room. For a given upstream wind speed the in-room mean velocity vectors are found to be sensitive to upstream wind direction while the effect of upstream turbulence level on in-room wind speed is shown to be negligible.

Many-legged maneuverability: dynamics of turning in hexapods

Remarkable similarities in the vertical plane of forward motion exist among diverse legged runners. The effect of differences in posture may be reflected instead in maneuverability occurring in the horizontal plane. The maneuver we selected was turning during rapid running by the cockroach Blaberus discoidalis, a sprawled-postured arthropod. Executing a turn successfully involves at least two requirements. The animal's mean heading (the direction of the mean velocity vector of the center of mass) must be deflected, and the animal's body must rotate to keep the body axis aligned with the heading. We used two-dimensional kinematics to estimate net forces and rotational torques, and a photoelastic technique to estimate single-leg ground-reaction forces during turning. Stride frequencies and duty factors did not differ among legs during turning. The inside legs ended their steps closer to the body than during straight-ahead running, suggesting that they contributed to turning the body. However, the inside legs did not contribute forces or torques to turning the body, but actively pushed against the turn. Legs farther from the center of rotation on the outside of the turn contributed the majority of force and torque impulse which caused the body to turn. The dynamics of turning could not be predicted from kinematic measurements alone. To interpret the single-leg forces observed during turning, we have developed a general model that relates leg force production and leg position to turning performance. The model predicts that all legs could turn the body. Front legs can contribute most effectively to turning by producing forces nearly perpendicular to the heading, whereas middle and hind legs must produce additional force parallel to the heading. The force production necessary to turn required only minor alterations in the force hexapods generate during dynamically stable, straight-ahead locomotion. A consideration of maneuverability in the horizontal plane revealed that a sprawled-postured, hexapodal body design may provide exceptional performance with simplified control.

On the deep western-boundary current in the Southwest Pacific Basin

The principal system of deep western-boundary currents in the subtropical South Pacific is that in the Southwest Pacific Basin, which transports Circumpolar Deep Water northward and Pacific Deep Water (at mid-depths) southward. The WOCE PCM9 current-meter array was placed across this system at Lat. 32° 30′S in order to measure the mean transports of those components and their variations. The array, consisting of 60 current meters on 20 moorings, extended 1000 km eastward from the Tonga–Kermadec Ridge, and remained in place for 22 months, between February 1991 and December 1992. The instruments were situated approximately at 2500 m, 4000 m, and close to the bottom. CTD sections (including dissolved oxygen and nutrients) were occupied along the array during its deployment and recovery, and, in between, by the WOCE transpacific section P6. Density sections were used to construct objectively-mapped fields of geostrophic velocity, which were adjusted using current-meter data as integration constants to provide snapshots of the full velocity field. The resulting adjusted transports sometimes differed substantially from relative geostrophic transports, but agreed quite well with transports calculated from current records alone. A time series of volume transport was derived from objectively-mapped three-day-averaged currents. The boundary-current system at PCM9 was essentially 700 km wide, with flow most intense on the flank of the Tonga–Kermadec Ridge, where the maximum mean velocity vector had a magnitude of 9.6 cm s −1. The time-averaged transport, integrated horizontally across the array and from 2000 m to the bottom, was 16.0×10 6±11.9×10 6 m 3 s −1 northward. Of this roughly 15.8×10 6±9.2×10 6 m 3 s −1 was northward flow of Circumpolar Deep Water, and 0.2×10 6±5.1×10 6 m 3 s −1 was northward flow of Pacific Deep Water. Even for the 22-month mean, however, the velocity field was strikingly banded vertically, and there was little impression of a zero-velocity surface following the demarcation between Circumpolar Deep Water and Pacific Deep Water across the section; only in the horizontally integrated sense was there a correspondence between water masses and the variation of transport with depth. The very large variability in transport is associated with prominent oscillations of periods near 50 days, 20 days, and 10 days, as well as with strong events distributed irregularly across the array that lead to a concentration of spectral energy in a band between 40 and 200 days. The origins of these disturbances are not known. While unexpectedly large changes in the density field near the Tonga–Kermadec Ridge were observed from one cruise to another, the huge fluctuations in transport seemed to be connected more with velocity signals varying only slowly with depth. No measurable changes in water-mass properties were detected by the cruises during the 22 months of deployment, but the salinity was about 0.01 lower at the salinity maximum in the Circumpolar Deep Water than it had been 25 years earlier. The direct, long-term transport measurement suggests that the total upwelling at 2000 m north of 30° S is 13×10 6 m 3 s −1, corresponding to an areally-averaged vertical velocity of 1.0×10 −5 cm s −1. This is substantially smaller than earlier values, and it helps to reduce estimates of the global deep upwelling closer to those of the global deep downwelling. The small value of Pacific Deep Water transport in the boundary-current system, relative to that of Circumpolar Deep Water, implies, within the framework of the Stommel–Arons dynamics, that little of the deep water entering the Pacific from the Antarctic returns southward at mid-depths. If so, then some present-day circulation schemes and budgetary constructions need to be re-assessed.

Angular Bias Errors in Three-Component Laser Velocimeter Measurements

For three-component laser velocimeter systems, the change in projected area of the coincident measurement volume for different flow directions will introduce an “angular” bias in naturally sampled data. In this study, the effect of turbulence level and orientation of the measurement volumes on angular bias errors was examined. The operation of a typical three-component laser velocimeter was simulated using a Monte Carlo technique. Results for the specific configuration examined show that for turbulence levels less than 10 percent no significant bias errors in the mean velocities will occur and errors in the root-mean-square (r.m.s.) velocities will be less than 3 percent for all orientations. For turbulence levels less than 30 percent, component mean velocity bias errors less than 5 percent of the mean velocity vector magnitude can be attained with proper orientation of the measurement volume; however, the r.m.s. velocities may be in error as much as 10 percent. For turbulence levels above 50 percent, there is no orientation which will yield accurate estimates of all three mean velocities; component mean velocity errors as large as 15 percent of the mean velocity vector magnitude may be encountered.

TAYLOR DISPERSION OF MULTICOMPONENT SOLUTES

Coupled transport of multicomponent solutes in globally continuous systems is considered in the framework of the Generalized Taylor dispersion theory. Coupling between transports of n different species at the local (or micro-) scale, is considered to result from first-order irreversible surface reactions occurring on the local space boundaries, or from the off-diagonal terms of the solute diffusivity matrices. General expressions are obtained for the global effective (long-time) solute dispersion matrix cofficients: mean global scalar reactivity, velocity vector and dispersivity dyadic. The effect of surface chemical reactions is to partition the matter between different solute constituents. This is manifested in a coupling of the global transport coefficients, which may be mathematically removed by a linear (canonic) transformation applied to the effective global transport equation. This type of coupling does not exist for inert solutes. The second type of the global coupling is represented by the off-diagonal terms of the global velocity and dispersivity matrices. It exists for both reactive and inert solutes. This coupling stems from the convective dispersion process (dependence or the global velocity vector on the local space coordinate). Is shown to be irremovable from the global transport equation by any linear transformation via the solute partition matrix. In the canonic form of the global equation the irremovable coupling is manifested by the traceless parts of the global solute velocity matrix and the global solute dispersivity. The solution scheme is illustrated by calculating the mean global diffusivity of a solute consisting of two components, transport of which is coupled at the microscale via the molecular diffusivity matrix. At the macroscale the coupling is shown to be represented by negative off-diagonal terms of the global diffusivity matrix,

On the stochastic theory of solute transport by unsteady and steady groundwater flow in heterogeneous aquifers

In this study the exact and approximate deterministic partial differential equations of the time-space evolution of mean solute concentration, of solute concentration two-point moment and of solute concentration n-point moment for conservative solute transport by unsteady and steady groundwater flow in a heterogeneous aquifer were developed in the real time-space domain under second-order cumulant expansion. These derivations were performed by means of the cumulant expansion method, combined with the calculus for the time-ordered exponential and with the calculus for Lie operator. The mean solute transport equations which describe the time-space evolution of mean conservative solute concentration under transport by unsteady and steady groundwater flows in a heterogeneous aquifer have convective-dispersive forms whose convective and dispersive coefficients are defined precisely in terms of the mean and covariance functions of the pore flow velocity random field. However, owing to the spatial nonuniformity of groundwater flow in heterogeneous porous media a new convective coefficient, besides the standard mean velocity vector, appeared in the derived mean solute transport equations in the case of steady flows. In the case of transport by unsteady groundwater flow in a heterogeneous aquifer, the new convective coefficient (besides the standard mean velocity vector) is due to the non-zero divergence of the pore flow velocity. The fundamental reason for the convective-dispersive form of the mean transport equations is the second-order truncation of the formal cumulant expansion. In the derived mean solute transport equations the macroscopic dispersion coefficient emerges as the time integral of the covariance function of the pore flow velocity. However, both in the case of transport by unsteady groundwater flow and in the case of transport by steady spatially nonstationary-nonuniform groundwater flow the macroscopic dispersion coefficients and convective coefficients vary with spatial locations within the porous medium. Only in the case of transport by steady spatially stationary-nonuniform flow are both the macroscopic dispersion coefficient and the convective coefficient constant with respect to spatial location within the heterogenous aquifer. Therefore, only in the case of conservative solute transport by steady spatially stationary-nonuniform groundwater flow in a heterogeneous aquifer does the mean transport equation apply to all spatial locations within the aquifer with the same parameter values at each time instant.

A fast simple hot-wire method of determining the mean velocity vector of complex three-dimensional flows

A fast and simple method of determining the mean velocity vector of complex three-dimensional flow fields is outlined. Straight and slanted single hot-wires are rotated in two perpendicular planes. This method increases the angular resolution, which is of importance in flow situations where one of the velocity components dominates and the other changes rapidly from one point to another. The method was calibrated in a wind tunnel and assessed in the internal flow field at the outlet of a fan in a defroster channel. It is shown that the hot-wire method yields good agreement with corresponding flow visualizations determined using a textile thread, and an integration of the measured mean flow yields a flow rate which agrees within a few percent with corresponding direct measurements on an orifice plate.

Control of vortex shedding from circular cylinder by acoustic excitation

The flow around a circular cylinder was controlled by an acoustic excitation issued from a thin slit along the cylinder axis. The static pressure distributions around the cylinder wall and flow characteristics in the near wake have been measured. Experiments were performed under three cases of Reynolds number, 7.8 * 104/, 2.3 * 105/ and 3.8 * 105/. The effects of excitation frequency, sound pressure level and the location of the slit were examined. Data indicate that the excitation frequency and the slit location are the key parameters for controlling the separated flow. At Red/, = 7.8 * 104/, the drag is reduced and the lift is generated to upward direction, however, at Red/, =2.3 * 105/ and 3.8 * 105/, the drag is increased and lift is generated to downward direction inversely. It is thought that the lift switching phenomenon is due to the different separation point of upper surface and lower surface on circular cylinder with respect to the flow regime which depends on the Reynolds number. Vortex shedding frequencies are different at upper side and lower side. Time-averaged velocity field shows that mean velocity vector and the points of maximum intensities are inclined to downward direction at Red/ = 7.8 * 104/, but are inclined to upward direction at Red/ = 2.3 * 105/.

Cold Model Experiment on Fluid Flow Phenomena in Hot Dip Plating Bath.

Flow phenomena in a hot dip plating bath were investigated by using cold models with reduced scale of 1/5 and 1/10. The mean velocity components, root-mean-square value of turbulence components and Reynolds shear stress in the bath were measured using a hot-wire anemometer and a two-channel laser Doppler velocimeter (LDV). The flow in the bath had three dimensional components. Main flow induced by belt motion was directed from the entry region to the exit region, and this flow subsequently returned in the entry region along the side walls and the bottom wall. A part of the flow returning along the side walls entered the region enclosed with the belt. The flow in the region enclosed with the belt had also three dimensional components. The flow pattern in the whole bath was in good agreement with that suggested by mean velocity vectors measured with the LDV. Mean velocity components and the root-mean-square value of turbulence components were altogether low in the almost all part of the entry region except near the belt. As the value of Reynolds shear stress was very large in the vicinity of the belt in the exit region, the dross would be vigorously disturbed and dispersed there.

Weak static magnetic fields increase the speed of circumnutation in cucumber (Cucumis sativus L.) tendrils

Tendrils are thread-like organs whose function is to support the stems of many species of climbing plants. Tendrils naturally move (circumnutate) in space. Individual tendrils of cucumber (Cucumis sativus L.) ‘Poinset’ had the vertical component of their mean velocity vector of circumnutation changed when exposed to a range of weak static magnetic fields between 1 and 16 mT. The speed (modulus) of the velocity vector was significantly increased (p=0.016) in the vicinity of a magnet, but its direction did not show a definite trend with respect to the magnet. Although cucumber tendrils bear static positive charges, they did not behave as charged bodies do in a magnetic field, neither did they show a magnetotropic response. In fact, tendrils showed a nastic response to magnetism. Magnetic fields affected some processes underlying the movement of circumnutation, but no clear interpretation of them can be given presently on the basis of the known effects of magnetism on plants. It is clear that cucumber tendrils, because of some inherent susceptibility to magnetism or their particular size and shape, are very sensitive to relatively low static magnetic field strengths.

Turbulent mixing in a free jet issuing from a low aspect ratio contoured rectangular nozzle

AbstractThe flow field of a turbulent free jet issuing from a contoured rectangular nozzle of aspect ratio 2 has been studied experimentally, using hot-wire anemometry. The study was undertaken to gain some understanding of the mixing process within the jet. Results of the measured and derived mean flow and turbulence quantities are presented. The three components of the mean velocity vector, the three Reynolds normal stresses, the two Reynolds primary shear stresses, and the flatness factor of the streamwise fluctuating velocity were measured. Mass entrainment, turbulence kinetic energy, and the intermittency factor were derived from the mean streamwise velocity data, the Reynolds normal stress data, and the flatness factor data, respectively. The derived results and the Reynolds primary shear stress data indicate enhanced near-field mixing of the present rectangular jet compared to a round turbulent free jet. The mean streamwise velocity field changes from a rectangular to an oval and then to an approximately circular shape at about twenty equivalent nozzle diameters downstream of the nozzle exit plane.

An experimental study of a three-dimensional pressure-driven turbulent boundary layer

A three-dimensional, pressure-driven turbulent boundary layer created by an idealized wing–body junction flow was studied experimentally. The data presented include time-mean static pressure and directly measured skin-friction magnitude on the wall. The mean velocity and all Reynolds stresses from a three-velocity-component fibre-optic laser-Doppler anemometer are presented at several stations along a line determined by the mean velocity vector component parallel to the wall in the layer where the $\overline{u^2}$ kinematic normal stress is maximum (normal-stress coordinate system). This line was selected by intuitively reasoning that overlap of the near-wall flow and outer-region flow occurs at the location where $\overline{u^2}$ is maximum. Along this line the flow is subjected to a strong crossflow pressure gradient, which changes sign for the downstream stations. The shear-stress vector direction in the flow lags behind the flow gradient vector direction. The flow studied here differs from many other experimentally examined three-dimensional flows in that the mean flow variables depend on three spatial axes rather than two axes, such as flows in which the three-dimensionality of the flow has been generated either by a rotating cylinder or by a pressure gradient in one direction only throughout the flow.The data show that the eddy viscosity of the flow is not isotropic. These and other selected data sets show that the ratio of spanwise to streamwise eddy viscosities in the wall-shear-stress coordinate system is less scattered and more constant (about 0.6) than in the local free-stream coordinate system or the normal stress coordinate system. For y+ > 50 and y/δ < 0.8, the ratio of the magnitude of the kinematic shear stress |τ/ρ| to the kinematic normal stress $\overline{v^2}$ is approximately a constant for three-dimensional flow stations of both shear-driven and pressure-driven three-dimensional flows. In the same region, the ratio of the kinematic shear stresses $-\overline{vw}/-\overline{uw}$ appears to be a function of y+ in wall-stress coordinates for three-dimensional pressure-driven flows.

Flows in a curved combustor inlet with and without a guide vane

Laser Doppler velocimetry measurements of the longitudinal, radial, and spanwise velocity components are presented for the three-dimensional flowfield in a 60-deg curved combustor inlet duct with and without a guide vane. The Reynolds number based on the bulk mean velocity and hydraulic diameter was 2.53 x 10(exp 4). Quantities such as mean-velocity vectors, wall static pressure, size of the reversed flow region, number of secondary vortex pairs, streamwise mean vorticity, turbulence intensity contours, anisotropy, turbulent kinetic energy, and structure parameters were used to characterize the flow. Comparisons between the flow characteristics within the curved duct with and without a guide vane were also made. It was found that the presence of a guide vane partially suppresses formation of the region of flow reversal, provides a more uniform velocity distribution across the inner passage of the curved duct, and enhances a stronger secondary flow vortex in the cross-stream section. 34 refs.

溶融めっき浴内流れに関するコールドモデル実験

Flow phenomena in a hot dip plating bath were investigated by using cold models with reduced scale of 1/5 and 1/10. The mean velocity components, root-mean-square value of turbulence components and Reynolds shear stress in the bath were measured using a hot-wire anemometer and a two-channel laser Doppler velocimeter (LDV). The flow in the bath had three dimensional components. Main flow induced by belt motion was directed from the entry region to the exit region, and this flow subsequently returned in the entry region along the side walls and the bottom wall. A part of the flow returning along the side walls entered the region enclosed with the belt. The flow in the region enclosed with the belt had also three dimensional components. The flow pattern in the whole bath was in good agreement with that suggested by mean velocity vectors measured with the LDV. Mean velocity components and the root-mean-square value of turbulence components were altogether low in the almost all part of the entry region except near the belt. As the value of Reynolds shear stress was very large in the vicinity of the belt in the exit region, the dross would be vigorously disturbed and dispersed there.

Large-eddy simulations of turbulent reacting flows in a chamber with gaseous ethylene injecting through the porous wall

Large-eddy simulations were performed to study the turbulent reacting flows in a simulated solid-fuel combustion chamber. The time-dependent axisymmetric compressible conservation equations were solved directly without using subgrid-scale turbulence models. The combustion process considered was a one-step, irreversible, and infinitely fast chemical reaction and the pyrolizing solid fuel was simulated by gaseous ethylene injected through a porous wall for a practical range of fuel blowing velocity encountered in solid-fuel combustion chambers for the first time. The numerical code used the finite-volume technique which involved alternating in time the second-order, explicit MacCormack's and Godunov's methods. Characteristic-based boundary conditions were applied on inflow and outflow boundaries, which allowed outlet boundary conditions to be nonzero gradients and, in turn, a practical length of computational domain to be realized. The effects of combustion on the large-scale unsteady flow structure and the mean flameholder recirculation zone were documented in terms of the density contours, vorticity dynamics, streamlines, mean-velocity vector fields, temperature profiles, flame position, and fuel blowing velocity. A comparison of the distributions of instantaneous and mean mass fractions of reactants shows that the present method appropriately reveals the effects of large-scale turbulent motions on combustion. Furthermore, the present large-eddy simulations have achieved a significant improvement in predicting the mean effective reattachment length over the previous calculations incorporating with turbulence models. The physical insight regarding the decrease of the mean effective reattachment length with combustion was also addressed.

Structure of a methanol/air coaxial reacting spray near the stabilization region

Planar laser Mie scattering, planar laser-induced fluorescence and two component phase-doppler interferometry have been used to study the reaction zone structure near the stabilization region of a coaxial methanol/air spray flame. The configuration of the experiment was chosen to approximate the atomizer geometry, surface tension and Weber number of a single coaxial rocket injector. The measurements are made in a water-cooled, optically accessible confinement chamber at a pressure of 1 atm. Data are reported for two atomizing air velocity conditions. One yields a flame length of approximately 1 m, the other, half that value. Both the Weber number (characterizing the atomization process) and the Reynolds number (characterizing the gas-phase mixing process) vary between the cases, but the data suggest that it is the Weber number which has the dominant effect. In both cases OH imaging shows that the reaction zone is confined to a narrow region, with the OH field being similar in appearance to that of a single-phase turbulent mixing-controlled (diffusion) flame. Size-classified mean velocity vectors derived from the phase-doppler data show striking differences in the flow pattern for low and high Stokes number droplets. Droplets 5 μm in diameter and below (Stokes number less than 3) appear to follow the recirculating eddies that provide flame stabilization while droplets of large Stokes number travel ballistically through the flow. Increasing the Weber number by a factor of 2.5 decreased the Sauter mean diameter of the spray by as much as one-third, and the arithmetic mean diameter by as much as one-half. We believe that it is this decrease in the spray droplet diameter that is primarily responsible for the very different flame lengths in the two cases.

Interrupted jet as a candidate for mixing enhancement in aircraft ejectors

The near flowfield of an interrupted turbulent free jet, which consists of four unventilated rectangular jets, has been studied experimentally. The study was done to show the potential of the interrupted jet for passive enhancement of mixing in aircraft thrust-augmenting ejectors. The quantities measured, using hot-wire anemometry, include the three components of the mean velocity vector and the Reynolds normal and primary shearing stresses. The results show that, compared to a single, uninterrupted, rectangular jet of aspect ratio 10, the mixing in an interrupted jet is enhanced. The enhanced mixing is evidenced by a faster decay of the mean streamwise velocity along the centerline of each of the four jets and higher centerline streamwise turbulence intensities. The results also show that the unventilated multiple turbulent rectangular free jets of the present study develop faster into a single jet, implying complete mixing, than their known ventilated counterparts. The measured Reynolds normal and primary shearing stresses are higher than those found at corresponding locations in a round turbulent free jet, and are thus consistent with the faster mixing of the interrupted turbulent free jet.

Development of a large-aspect-ratio rectangular turbulent free jet

This paper reports the results of detailed mean flow and turbulence measurements made with hot-wire anemometry in the flowfield of a turbulent free jet of air issuing from a sharp-edged rectangular slot of aspect ratio 20 into still air surroundings. All three components of the mean velocity vector, the three Reynolds normal stresses and the two Reynolds primary shear stresses were measured. The mean streamwise vorticity and the turbulence kinetic energy have been calculated from the relevant measured data. It was found that the cross section of the jet, in the near flowfield, is dominated by counter-rotating streamwise vortices that facilitate rapid nearfield mixing. Rapid mixing is also evidenced by a short potential core length and high values of the turbulence kinetic energy and the Reynolds primary shear stresses compared with those found in an axisymmetric jet at the corresponding streamwise locations. In addition, mean streamwise velocity off-center peaks, which may be the result of the self-induction of the counter-rotating streamwise vortices, were found in the near flowfield, and the jet was found to spread monotonically in the central plane of the slot minor axis and to contract initially in the central plane of the slot major axis.