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An exception to the optimal geometry for deepwater tubulars has been made for short cylinders, such as spar production platforms, where considerations such as drag and the need for shorter correlation lengths (due to the limited length of the structure) have driven helical strake designs closer to the geometries of tradition helical strakes for wind applications.īecause helical strakes are relatively bluff to the incoming flow and often produce early separation of the incoming flow, they are associated with higher drag. Helical strakes are effective when they break up the correlation of vortices along a tubular and produce random alternating forces along the tubular length. The configuration utilizing three starts was generally maintained. Early tests of helical strakes for deepwater tubular applications found that the traditional wind parameters were inadequate and that the strakes performed best with a fin height closer to 25 percent and a pitch per start in the range of 12 to 20 times the tubular diameter. Traditional helical strakes designed for applications in wind had three starts (three fins each 120 degrees apart around the tubular), pitch per start of approximately 5 times the tubular diameter, and a fin height of 10 percent of the diameter. Helical strakes consist of one or more fins that are spiraled around a tubular. Strakes are often a feasible candidate for risers, tendons, jumpers, and horizontal pipeline spans. Protruding fins disrupt the correlation of vortex shedding along a tubular’s span, resulting in lower and randomly-phased lift and drag forces. Helical strakes are a popular choice for suppressing VIV of subsea tubulars. VIV can usually be minimized with the careful selection and design of VIV suppression devices such as helical strakes and fairings. See all of #tdebbie2002's lists of films with English subtitles. Thanks for putting together this awesome German language education resource! All the subtitles are uploaded by the users, and you can find various language subtitles from this site. |
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