196,114 research outputs found

    On the galloping instability of two-dimensional bodies having elliptical cross sections.

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    Galloping, also known as Den Hartog instability, is the large amplitude, low frequency oscillation of a structure in the direction transverse to the mean wind direction. It normally appears in the case of bodies with small stiffness and structural damping, when they are placed in a flow provided the incident velocity is high enough. Galloping depends on the slope of the lift coefficient versus angle of attack curve, which must be negative. Generally speaking this implies that the body is stalled after boundary layer separation, which, as it is known in non-wedged bodies, is a Reynolds number dependent phenomenon. Wind tunnel experiments have been conducted aiming at establishing the characteristics of the galloping motion of elliptical cross-section bodies when subjected to a uniform flow, the angles of attack ranging from 0° to 90°. The results have been summarized in stability maps, both in the angle of attack versus relative thickness and in the angle of attack versus Reynolds number planes, where galloping instability regions are identified

    Common rules for 'out of home' catering

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    Could common EU rules for organic catering be possible? Are they needed or even desired? There are several initiatives in Europe that work on the exchange of information between the different EU countries with regard to catering standards and certification, and these are setting the groundwork for a long-term harmonised regulation
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