Topic
Critical speed
About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.
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TL;DR: In this article, a useful design tool is developed for a bundle conductor of an electrical transmission line by using a three-degree-of-freedom hybrid model, which accommodates interactions of the vertical, horizontal and torsional movements, non-linear aerodynamic loads, a non-uniform ice geometry, distributed and discrete galloping control devices, and a variation of the wind along a span.
86 citations
Patent•
24 Apr 1987
TL;DR: In this article, a variable speed wind turbine is controlled in a way which avoids the turbine lingering at a critical speed which would otherwise tend to cause excessive vibration, and the selected rate is changed in the vicinity of the critical speed to a different rate which is selected slower in the selected embodiment.
Abstract: A variable speed wind turbine is controlled in a way which avoids the turbine lingering at a critical speed which would otherwise tend to cause excessive vibration. The disclosed method and apparatus increases speed at a selected rate with respect to generator output power except in the vicinity of the critical speed. The selected rate is changed in the vicinity of the critical speed to a different rate which is selected slower in the selected embodiment, to avoid commanding the critical speed. After the output power increases or decreases beyond the critical point, a deliberate discontinuity in the speed command signal is induced. A rapid speed change through the critical speed is accompanied by a corresponding power output change. If the speed is increasing at a selected slower rate below the critical speed, and the speed command signal is stepped to a higher level just before reaching the critical speed, the speed will rapidly increase and quickly pass through the critical speed while the power output decreases. Similarly, if the speed is decreasing at a selected slower rate above the critical speed, and the speed command signal is stepped to a lower level just before reaching the critical speed, the speed will rapidly decrease and quickly pass through the critical speed while the power output increases.
86 citations
TL;DR: In this paper, the authors evaluated the validity of these assumptions and the usefulness of velocity criteria based on critical speed data in predicting passage success in wild smallmouth bass Micropterus dolomieu.
Abstract: Critical swimming speed (U crit) is a common measure of the relationship between exercise intensity and duration within the prolonged performance envelope. This relationship is often used to establish water velocity criteria for fishways and culverts; however, the technique involves the assumptions that fish will choose to move at (1) a swimming speed equivalent to U crit and (2) a ground speed that results in a passage time equal to the interval used in the critical speed protocol. The objective of this study was to evaluate the validity of these assumptions and the usefulness of velocity criteria based on critical speed data in predicting passage success. To accomplish this, I measured the critical swimming speed of wild smallmouth bass Micropterus dolomieu in a respirometer and the relationship between the water velocity and swimming speed of fish in a 50-m raceway. The latter was then used in conjunction with the former to calculate water velocity criteria based on ground speeds actually atta...
86 citations
27 Oct 1937
TL;DR: In this article, the effect of shape, compressibility, and Reynolds number on the drag and critical speed for simple forms were measured in the NACA 11-inch high-speed wind tunnel.
Abstract: In order to determine the effect of shape, compressibility, and Reynolds number on the drag and critical speed for simple forms, the drag forces on models of various simple geometric cross sections were measured in the NACA 11-inch high-speed wind tunnel. The models were circular, semitubular, elliptical, square, and triangular (isosceles) cylinders. They were tested over a speed range from 5 percent of the speed of sound to a value in excess of the critical speed, corresponding, for each model, approximately to a tenfold Reynolds number range, which extended from a minimum of 840 for the smallest model to a maximum of 310,000 for the largest model.
85 citations
TL;DR: Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed as discussed by the authors, which accelerates the electrons much above the phase speed of the linearly unstable modes.
Abstract: Particle simulations of the modified two-stream instability demonstrate strong electron acceleration rather than bulk heating when the relative drift speed is below a critical speed Vc A very interesting nonlinear mode transition and autoresonance acceleration process is observed which accelerates the electrons much above the phase speed of the linearly unstable modes Simple criteria are presented that predict the value of Vc and the number density of the accelerated electrons
85 citations