The interpretation of statistics from hot-film anemometers used in salt water flows of variable temperature and density

Stillinger, D. C.

doi:10.1088/0022-3735/15/12/014

Cited by 4 publications

(5 citation statements)

References 2 publications

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“…Perhaps due to the brief and unsustained input of energy in Linden's experiments, the total mixing efficiency was characterized by the largest scales that the density step initially allowed. Gibson (1980) andStillinger et al (1983) have developed a length scale model for decaying turbulence. In this model, the scale of turbulent eddies grows unaffected by buoyancy until the largest eddies reach a scale proportional to the Ozmidov scale L,, after which they can no longer overturn.…”

Section: Comparison With Linden's Resultsmentioning

confidence: 99%

Mixing efficiency in stably-stratified decaying turbulence

Rohr

Itsweire

Atta

1984

Geophysical & Astrophysical Fluid Dynamics

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The behavior of the flux Richardson number R,, as a function of the overall Richardson number Ri,, was investigated for a stably stratified, grid-generated, turbulent flow evolving in a closed-loop water channel. The turbulent dissipation rate E, the buoyancy or vertical mass flux pW and the rms density fluctuation p' were obtained from simultaneous single-point measurements of the horizontal and vertical velocity components and density fluctuations. From these, R, and Ri, were calculated at each point in the spatially evolving flow. The resulting curves of R , vs. Ri, exhibit the full range of behavior found in the very different case studied by Linden (1980). The length scale arguments of Gibson (1980) and Stillinger et a/. (1983b) provide an underlying mechanism which successfully accounts for the shape of the R, vs. Ri, curve.

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Section: Comparison With Linden's Resultsmentioning

confidence: 99%

Mixing efficiency in stably-stratified decaying turbulence

Rohr

Itsweire

Atta

1984

Geophysical & Astrophysical Fluid Dynamics

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“…One MSCTI was used to measure temperature and conductivity profiles, while the other was combined with a thermal anemometer (TSI model 1249A-10W cross-flow X-film probe and IFA-300 constant temperature anemometer) to measure streamwise and vertical velocities. Combining the X film with the MSCTI was necessary to correct the velocity signal for temperature and density fluctuations (Stillinger 1982). The spatial resolution of the X film, temperature, and conductivity probe (hereafter XTC) was limited by the separation of the MSCTI and X-film probes (about 2 mm) and the temporal .…”

Section: B Instrumentsmentioning

confidence: 99%

Experiments on Differential Scalar Mixing in Turbulence in a Sheared, Stratified Flow

Jackson

Rehmann

2014

Journal of Physical Oceanography

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Laboratory experiments were performed to measure differential diffusion of temperature and salinity across a sheared density interface. The eddy diffusivity of temperature K T exceeded the eddy diffusivity of salinity K S by as much as 1.5 orders of magnitude at low «/nN 2 , where « is the rate of dissipation of turbulent kinetic energy, n is the kinematic viscosity, and N is the buoyancy frequency in the pycnocline. The diffusivity ratio d 5 K S /K T increased from about 0.05 to 1 over the range 0.1 , «/nN 2 , 40. These differences made the eddy diffusivity of density depend on the density ratio. The trend of d with «/nN 2 was consistent with trends found in other experiments, simulations, and theory, and the collapse of several datasets allowed the diffusivity ratio to be expressed as a function of «/nN 2 . However, shear decreased differential diffusion less in the experiments than predicted by theory for homogeneous turbulence subjected to constant shear and stratification. No strong effect of the density ratio on the diffusivity ratio was apparent. Because many flows in oceanography and limnology have values of «/nN 2 low enough to exhibit significant differential diffusion, accounting for differential diffusion in interpreting measurements and modeling stratified water bodies is recommended.

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“…The behaviour of the turbulent kinetic energy, turbulent production and buoyancy flux is investigated in $4.1 for different values of Richardson number and development time 7. Section 4.2 compares the present evolution of turbulent lengthscales with other laboratory stratified-shear-flow measurements, as well as the unsheared stratified experiments of Stillinger, Helland & Van Atta (1983) and Itsweire, Helland & Van Atta (1986) (hereinafter referred t o as SHV and IHV respectively). Section 5 investigates the general behaviour of the velocity and density spectra.…”

Section: Introductionmentioning

confidence: 94%

“…The UCSD ten-layer, closed-loop water channel was designed to produce stably stratified, turbulent shear flows in which measurements could be extended sufficiently far downstream to study evolving turbulence statistics. The basic facility has been described in detail by Stillinger et al (1983).…”

Section: Experimental Facilitymentioning

confidence: 99%

“…Standard quartz-coated TSI films mounted on an X-film probe provided measurements of the downstream (0, u) and vertical velocity (w) components. Using the error analysis of Stillinger (1983) the salinity contamination of the measured velocity components was found to be negligible and the low-frequency temperature drift was compensated for with temperature measurements from a platinum resistance thermometer. A four-wire conductivity probe, having both good spatial resolution ( < 2.5 mm) and very low drift, developed by Head (1983), measured the local instantaneous conductivity of the salt solution.…”

Section: Oj-pdipcmentioning

confidence: 99%

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Growth and decay of turbulence in a stably stratified shear flow

Rohr¹,

et al. 1988

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The behaviour of an evolving, stably stratified turbulent shear flow was investigated in a ten-layer, closed-loop, salt-stratified water channel. Simultaneous single-point measurements of the mean and fluctuating density and longitudinal and vertical velocities were made over a wide range of downstream positions. For strong stability, i.e. a mean gradient Richardson number Ri greater than a critical value of Ricr ≈ 0.25, there is no observed growth of turbulence and the buoyancy effects are similar to those in the unsheared experiments of Stillinger, Helland & Van Atta (1983) and Itsweire, Helland & Van Atta (1986). For values of Richardson number less than Ricr the turbulence grows at a rate depending on Ri and for large evolution times the ratio between the Ozmidov and turbulent lengthscale approaches a constant value which is also a function of Richardson number.Normalized velocity and density power spectra for the present experiments conform to normalized spectra from previous moderate- to high-Reynolds-number studies. With increasing $\tau = (x/\overline{U}) (\partial \overline{U}/\partial z)$ or decreasing stability, the stratified shear spectra exhibit greater portions of the universal non-stratified spectrum curve. The shapes of the shear-stress and buoyancy-flux cospectra confirm that they act as sources and sinks for the velocity and density fluctuations.

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The interpretation of statistics from hot-film anemometers used in salt water flows of variable temperature and density

Cited by 4 publications

References 2 publications

Mixing efficiency in stably-stratified decaying turbulence

Mixing efficiency in stably-stratified decaying turbulence

Experiments on Differential Scalar Mixing in Turbulence in a Sheared, Stratified Flow

Growth and decay of turbulence in a stably stratified shear flow

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