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Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.


Papers
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Journal ArticleDOI
TL;DR: In this article, the drop size distribution in very dilute (0.03% by volume) liquid-liquid dispersions over a wide range of rotational speeds, using different impellers with varying diameters and off-bottom clearances.

94 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the rotation on the characteristics of flow over the sphere was investigated, and it was shown that the flow becomes frozen at higher rotational speed with increasing Reynolds number.
Abstract: Numerical simulations are conducted for laminar flow past a sphere rotating in the streamwise direction, in order to investigate the effect of the rotation on the characteristics of flow over the sphere. The Reynolds numbers considered are Re = 100, 250 and 300 based on the free-stream velocity and sphere diameter, and the rotational speeds are in the range of 0 [les ] ω* [les ] 1, where ω* is the maximum azimuthal velocity on the sphere surface normalized by the free-stream velocity. At ω* = 0 (without rotation), the flow past the sphere is steady axisymmetric, steady planar-symmetric, and unsteady planar-symmetric, respectively, at Re = 100, 250 and 300. Thus, the time-averaged lift forces exerted on the stationary sphere are not zero at Re = 250 and 300. When the rotational speed increases, the time-averaged drag force increases for the Reynolds numbers investigated, whereas the time-averaged lift force is zero for all ω* > 0. On the other hand, the lift force fluctuations show a non-monotonic behaviour with respect to the rotational speed. At Re = 100, the flow past the sphere is steady axisymmetric for all the rotational speeds considered and thus the lift force fluctuation is zero. At Re = 250 and 300, however, the flows are unsteady with rotation and the lift force fluctuations first decrease and then increase with increasing rotational speed, showing a local minimum at a specific rotational speed. The vortical structures behind the sphere are also significantly modified by the rotation. For example, at Re = 300, the flows become ‘frozen’ at ω* = 0.5 and 0.6, i.e. the vortical structures in the wake simply rotate without temporal variation of their strength and the magnitude of the instantaneous lift force is constant in time. It is shown that the flow becomes frozen at higher rotational speed with increasing Reynolds number. The rotation speed of the vortical structures is shown to be slower than that of the sphere.

94 citations

Journal ArticleDOI
TL;DR: In this paper, a tapered thread tool with triple facets was designed and tested for high depth-to-width ratio friction stir welding at a rotational speed of 800-rpm and a welding speed of 30mm/min.

94 citations

Journal ArticleDOI
TL;DR: In this paper, a ball measuring system (BMS) is used to measure the torques due to drag exerted on the sphere and its holder as well as corresponding speeds are measured and transformed into values of shear stress and shear rate based on the method of Metzner and Otto.
Abstract: In order to describe the flow behaviour of debris flows often rheologic models are used. This study introduces two novel facilities to determine rheologic parameters of different models for debris flow material mixtures containing grain sizes larger than to be measured in standard viscometers. The diameter of the vertically rotating flume (VRF) is 2.5 m, the rectangular cross section has a width of 0.45 m, and the maximum rotational speed is around 30 revolutions per minute, corresponding to a mean speed of the examined mixture of ∼4 m/s. From the measured flow parameters total boundary shear stress and corresponding shear rate of the flowing mixture are derived. The ball measuring system (BMS) consists of a sphere that is dragged at specific speeds across a sample of 0.5 l volume with the help of a small sphere holder. Accordingly torques due to drag exerted on the sphere and its holder as well as corresponding speeds are measured and transformed into values of shear stress and shear rate based on the method of Metzner and Otto. Material taken from fresh debris flow deposits in Eastern Switzerland have been investigated with both facilities. We present results from experiments involving mixtures with different sediment concentrations and with grain sizes up to 5 mm. Although estimated from completely different approaches the rheologic parameters of the independent measurements are generally in reasonable agreement.

92 citations

Journal ArticleDOI
TL;DR: In this article, the recognition of faults in toothing during non-stationary start-up and run-down of gear drives is solved by means of the time-frequency analysis.

92 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023539
20221,195
2021522
2020773
20191,092
20181,138