Laminar–turbulent transition in Poiseuille pipe flow subjected to periodic perturbation emanating from the wall
摘要：
Transition in fully developed circular pipe flow was investigated experimentally by the introduction of periodic perturbations. The simultaneous excitation of the azimuthal periodic modes m=+2 and m=2 was chosen for detailed analysis. The experiments were carried out at three amplitudes. At the smallest amplitude the disturbances decayed in the direction of streaming. At intermediate input amplitude the disturbances amplified initially but then decayed with increasing distance downstream. Their growth was accompanied by the appearance of higher harmonics. At still higher amplitudes transition occurred. A mean velocity distortion corresponding to an azimuthal index of m=4 was observed at the intermediate and at the higher levels of forcing. When four stationary jets were introduced through the wall to emulate a similar mean velocity distortion, transition was observed at smaller amplitudes of forcing at modes ±2. Thus, weak longitudinal vortices provide an added instability needed to generate a secondary disturbance which, in turn, amplifies the steady vortical structures introduced by the jets. Such vortices may also be generated through the interaction of time-periodic helical modes.
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关键词：
Theoretical or Mathematical/ flow instability laminar to turbulent transitions pipe flow Poiseuille flow vortices/ laminar-turbulent transition Poiseuille pipe flow periodic perturbation wall fully developed circular pipe flow simultaneous excitation azimuthal periodic modes disturbances decay streaming intermediate input amplitude disturbance amplification higher harmonics higher amplitudes transition mean velocity distortion azimuthal index stationary jets weak longitudinal vortices secondary disturbance steady vortical structures time-periodic helical modes/ A4760 Flows in ducts, channels, and conduits A4715 Laminar flows A4725 Turbulent flows, convection, and heat transfer A4730 Rotational flow, vortices, buoyancy and other flows involving body forces A4720 Hydrodynamic stability and instability
DOI：
10.1016/j.ciresp.2012.11.015
被引量：
年份：
1998
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