Characteristics of Taylor vortex structure in combined axial and rotating flow

Abstract

The sequential form of the axial displacement of inclined Taylor vortices and their progressive degeneration to horizontal streaks due to the increasing dominance of axial flow is demonstrated via an analytical indicator-based direct flow visualization technique applied to a concentric cylinder cell with the inner cylinder rotating.Cette communication d6crit le decalage s6quentiel axial des tourbillons de Taylor inclinks, ces derniers se d6sa-gr6geant h la fin en de striures horizontales h la mesure de la domination du debit axial. Le ph6nomtne est manifest6 au moyen de visualisation bade sur les indicateurs color6s dans une cellule B cylindres coaxiaux, le cylindre int6rieur 6tant tournt. n recent years, there has been an increasing theoretical I and experimental interest in Taylor-Couette flow (Di Prima and Swinney, 1981;Park et al. 1983; Marcus, 1984a,b). A particularly interesting case is axial flow passing through the annulus between two concentric cylinders with one or both cylinders rotating. The onset of Taylor vortex formation in the presence of axial flow has been extensively studied (Chung and Astill, 1977;Takeuchi and Jankowski, 1981), but the structure of combined flow resulting at rotation rates of the inner-cylinder much larger than the critical rotation rate has not been thoroughly examined. Such a flow structure is expected to be highly complicated due to strong interaction between axial and rotating flow. Simmers and Coney (1979a) measured the velocity distribution in combined flow via hot wire anemometry. Based on the measurement of electric conductivity, Kataoka et al. (1975) described the axial movement of the Taylor vortices as an ideal plug flow without intermixing between adjacent Taylor cells in the range of 5 1.4 < Ta < 640 and 0 < Re < 90. Kataoka et al. (1977) also observed indirectly Taylor vortices distorted by the small imposed axial flow by means of a micro-electrode technique. Using the same technique, Coeuret et al. (Coeuret and Legrand, 1983;Legrand et al., 1983) attributed the disappearance of sharp frequency peaks in the associated density spectra to the deformation of Taylor vortices caused by the increasing axial flow. However, the entire process of propagation and deformation of the Taylor vortices induced by the imposed axial flow has not been studied in a systematic manner and current knowledge about the process mechanism is very limited. Classical visualization approaches (e.g., dye or smoke injection) cannot follow continuously the axial displacement of Taylor vortices, since the accumulation of the dye causes a rapid fading of colour and the suspended solid-particle technique fails to indicate a detailed flow structure in the intercylinder gap. The crucial experimental requirement is that the visualization technique must closely follow both convective propagation of Taylor vortices and their fine structure. The analytical-indicator technique (Quraishi and Fahidy , 1983a) is especially attractive for meeting this challenge. Because of its complete reversibility , the t...

A review of heat transfer between concentric rotating cylinders with or without axial flow

“…This zone would seem to correspond to relocation of the vortices in an overall movement at a speed equal to axial speed. This phenomenon has similarly been observed by Astill [48] and by Gu and Fahidy [49]. Lueptow et al [50] carried out a highly meticulous experimental study pertaining to types of flows for low Taylor numbers (Ta < 3000) and very low Reynolds numbers (Re a < 540) in the framework of a narrow cylindrical gap: h ¼ 0.885, e/R 1 ¼ 0.083 and G ¼ 41.…”

Pattern selection in the absolutely unstable regime as a nonlinear eigenvalue problem: Taylor vortices in axial flow

“…Therefore, our results are not limited to PV flow in a Taylor-Couette apparatus only. In this context we also mention the experimental investigation of Gu and Fahidy [23]. They observed that axial through-flow causes a rearrangement of the vortex centers similar to the one seen for tranverse convection rolls subject to a horizontal flow [15, Fig.…”

“…Only for higher through-flow rates, which are not investigated here, there is a bifurcation [19,20] to spirals [20][21][22][23][24][25][26]. We have performed numerical simulations of the full, rotationally symmetric, two dimensional (2D) Navier-Stokes equations (NSE).…”

“…Linear stability analyses of the basic state to traveling axisymmetric vortices were performed using various approximations, e. g. , for the narrow-gap limit, or simplified azimuthal velocity, or axial through-flow profiles [40], and later on for various aspect ratios fixed by the diameters of both cylinders [19,20,41,42]. Also, many experiments and comparisons with the theoretical predictions were done [21][22][23][24][25]28,29,[31][32][33][34][35]43,44].…”

Flow and axial dispersion simulation for traveling axisymmetric Taylor vortices

“…In the narrow-gap limit, they also found that the linear theory predicts that axisymmetric vortices form that have a positive axial velocity proportional to the axial flow Reynolds number. Gu and Fahidy (1985;1986) experimentally showed that the effect of axial flow is to decrease wavelength and to increase critical Taylor number. Their range of axial flow Reynolds numbers is substantially higher than Snyder's, starting at Re,=60.…”