Digital Vortex Flowmeters, bu the very nature of their principle of operation create vorticies. As such these vortices create Vortex-Induced Vibration. Typically, these vibrations are very small and users of Digital Vortex Flow Meters need not concern themselves with this mode of vibration. The information below is extracted from the Wikipedia pages referring to this
In periodical irregularities on this flow.
A classical example is the VIV of an underwater cylinder. You can see how this happens by putting a cylinder into the water (a swimming-pool or even a bucket) and moving it through the water in the direction perpendicular to its axis. Since real fluids always present some resonance).
VIV manifests itself on many different branches of engineering, from cables to heat exchanger tube arrays. It is also a major consideration in the design of ocean structures. Thus study of VIV is a part of a number of disciplines, incorporating smart materials.
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[edit] Motivation
They occur in many engineering situations, such as bridges, stacks, transmission lines, aircraft control surfaces, offshore structures, thermowells, engines, heat exchangers, marine cables, towed cables, drilling and production risers in petroleum production, mooring cables, moored structures, tethered structures, buoyancy and spar hulls, pipelines, cable-laying, members of jacketed structures, and other hydrodynamic and hydroacoustic applications. The most recent interest in long cylindrical members in water ensues from the development of hydrocarbon resources in depths of 1000 m or more.
Vortex-induced vibration (VIV) is an important source of fatigue damage of offshore oil exploration and production risers. These slender structures experience both current flow and top-end vessel motions, which give rise to the flow-structure relative motion and cause VIV. The top-end vessel motion causes the riser to oscillate and the corresponding flow profile appears unsteady.
One of the classical open-flow problems in fluid mechanics concerns the flow around a circular cylinder, or more generally, a bluff body. At very low Kármán vortex street occurs.
The natural frequency of vibration of the structure. When this happens large and damaging vibrations can result.
[edit] Current state of art
Much progress has been made during the past decade, both numerically and experimentally, toward the understanding of the shear layers and large-scale structures.
There is much that is known and understood and much that remains in the empirical/descriptive realm of knowledge: what is the dominant response amplitude in the synchronization range as a function of the controlling and influencing parameters? Industrial applications highlight our inability to predict the dynamic response of fluid–structure interactions. They continue to require the input of the in-phase and out-of-phase components of the lift coefficients (or the transverse force), in-line drag coefficients, correlation lengths, damping coefficients, relative roughness, shear, waves, and currents, among other governing and influencing parameters, and thus also require the input of relatively large safety factors. Fundamental studies as well as large-scale experiments (when these results are disseminated in the open literature) will provide the necessary understanding for the quantification of the relationships between the response of a structure and the governing and influencing parameters.
It cannot be emphasized strongly enough that the current state of the laboratory art concerns the interaction of a rigid body (mostly and most importantly for a circular cylinder) whose degrees of freedom have been reduced from six to often one (i.e., transverse motion) with a three-dimensional separated flow, dominated by large-scale vortical structures.
[edit] See also
[edit] References
- Bearman, P.W. (1984), “Vortex shedding from oscillating bluff bodies”, 10.1146/annurev.fl.16.010184.001211
- Williamson, C.H.K.; Govardhan, R. (2004), “Vortex-induced vibrations”, 10.1146/annurev.fluid.36.050802.122128
- Sarpkaya, T. (1979), “Vortex-induced oscillations: A selective review”, Journal of Applied Mechanics 46 (2): 241–258, 10.1115/1.3424537
- Sarpkaya, T. (2004), “A critical review of the intrinsic nature of vortex-induced vibrations”, Journal of Fluids and Structures 19 (4): 389–447, 10.1016/j.jfluidstructs.2004.02.005
- Sarpkaya, T.; Isaacson, M. (1981), Mechanics of wave forces on offshore structures, Van Nostrand Reinhold, ISBN 0-442-25402-4
- Sumer, B. Mutlu; Fredsøe, Jørgen (2006), Hydrodynamics around cylindrical structures, Advanced series on ocean engineering, 26 (revised ed.), World Scientific, ISBN 981-270-039-0
[edit] External links
- Vortex induced vibration data repository
- Design Principles for Ocean Vehicles Course Homepage at MIT
- eFunda: Introduction to Vortex Flowmeters
Source: Wikipedia