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Velocity gradient

About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.


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Patent
18 Oct 1995
TL;DR: In this paper, the velocity of sound in the oil is measured, preferably at a plurality of heights over a relatively short vertical range to determine the velocity gradient, which is then extrapolated for the entire depth of the oil.
Abstract: A method of and apparatus for determining the topography and/or volume of a layer of sludge on the bottom of an oil tank, for example, in which a sonar head (3) having a velocimeter is immersed in the oil, and a fan-shaped beam (12) of acoustic energy is swept across the layer of sludge (2). Also the velocity of sound in the oil is measured, preferably at a plurality of heights over a relatively short vertical range to determine the velocity gradient, which is then extrapolated for the entire depth of the oil. Processing means (8) determine, from the extrapolated velocity gradient, the topography and/or volume of the sludge (12). The method provides an accurate indication of the distribution and volume of sludge across the whole of the bottom of an oil tank, taking into account changes in the speed and attenuation of accoustic energy due to, for example, the temperature gradient in the oil.

19 citations

Journal ArticleDOI
TL;DR: A progressive change in profile shape was observed, indicating a range of translocation velocities, which agreed with a predicted velocity distribution based on calculated sieve tube conductivities and the size distribution of functional sieve tubes.
Abstract: The movement of 14 C-photosynthate in morning glory ( Ipomea nil Roth, cu. Scarlet O9Hara) vines 2 to 5 meters long was followed by labeling a lone mature leaf with 14 CO 2 and monitoring the arrival rate of tracer at expanding sink leaves on branches along the stem. To a first approximation, the kinetic behavior of the translocation profiles resembled that which would be expected from movement at a single velocity (“plug flow”) without tracer loss from the translocation stream. There was no consistent indication of a velocity gradient along the vine length. The profile moved along the vine as a distinct asymmetrical peak which changes shape only slowly. The spatial distribution of tracer along the vine reasonably matched that predicted on the basis of the arrival kinetics at a sink, assuming plug flow with no tracer loss. These observations are in marked contrast to the kinetic behavior of any mechanism describable by diffusion equations. However, a progressive change in profile shape (a symmetrical widening) was observed, indicating a range of translocation velocities. A minimum of at least two factors must have contributed to the observed velocity gradient: the exchange of 14 C between sieve elements and companion cells (demonstrated by microautoradiography) and the range of velocities in the several hundred sieve tubes which carried the translocation stream. Possible effects of these two factors on profile spreading were investigated by means of numerical models. The models are necessarily incomplete, due principally to uncertainties about the exchange rate between sieve elements and companion cells and the degree of functional connectivity between sieve tubes of different conductivities. However, most of the observed profile spreading may be reasonably attributed to the combined effects of those two factors. The mass average velocity of translocation (calculated from the mean times of 14 C arrival at successive sink leaves) was about 75% of the maximum velocity (calculated from the times of initial detection at the same sink leaves), which was usually between 0.6 and 1 cm min −1 . Owing to tracer exchange between sieve elements and companion cells, the mass average velocity of tracer in the sieve tubes was probably closer to 86% of the maximum velocity, a figure which agreed with a predicted velocity distribution based on calculated sieve tube conductivities and the size distribution of functional sieve tubes.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared two configurations of pulsed-wire probe for measurements in the very near wall region, as introduced by Castro and Dianat (1990) and Devenport et al.
Abstract: This experimental investigation compares two configurations of pulsed-wire probe for measurements in the very near wall region, as introduced by Castro and Dianat (1990) and Devenport et al. (1990). Diffusion of the thermal wake causes significant errors in regions where the velocity is low and the velocity gradient high. These errors, which are about the same for either configuration, are large in the viscous sub-layer. An analysis of diffusional effects is made, and a method of correction is given that applies equally in laminar and turbulent flow. It is necessary to calibrate a probe for the effects of shear in a known flow.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of fine water droplets on extinguishment of a methane-air counterflow diffusion flame, which was generated by piezoelectric atomizer.

19 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202233
2021127
2020116
2019134
201892