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Engineering and Construction
Pages 13 (3263 words)
Precessing Vortex Core Introduction Whenever fluid flows fast through a conduit, it is easily subjected to a spinning effect because of the turbulent flow. The resulting spiral motion of the fluid with a rapid swirl is the vortex. The vortex is subject to varying degrees of rotation .
While this appears to be an indication of perpetuated turbulence in fluid flow, experimental results have shown that the vortex tends to adapt to the force causing the spiral flow . Fig 1: Precession of the vortex tending towards the equilibrium Fluid Flow in the Precessing Vortex Core Perhaps, it is on the basis of this tendency of vortex precession that the concept of swirl flow stabilization was developed for turbines. The precessing vortex core (PVC) has been defined by  as “...a three-dimensional time-dependent coherent structure developed in the exhaust nozzle of many swirl devices...” p. 147. Some of the challenges faced in adopting the concept of precessing vortex core point at the significance of the geometry of the combustor (for gaseous flow) as well as the instabilities in the thermo-acoustic. These are noted by  as significant sources of losses in stabilization process. According to , “...a precessing vortex core can be a source that drives combustion instability” (p.1) and may lead to obvious undesirable results. This overshadows the beneficial effect of precessing vortex core sought for in a chamber such as an improved mixing of the fuel and air as well as stabilization of the flow. From the observation, the precessing vortex core can be linked to flow instabilities . This was demonstrated by the interactions among the zones of recirculation during the flow process. ...
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