Experimental study of expansion and compression effects on the stability of Taylor vortex flow

Abstract

The aim of the present experimental work is to determine the stability limits of Taylor cells by expanding and compressing the cells. The investigation was performed under laminar flow condition with a wide gap between an inner rotating cylinder and outer stationary cylinder. In order to allow the expansion and compression of the cells, the test rig was designed with a sliding upper end plate and a fixed lower end plate. The objectives are to determine the maximum and minimum size limits of each number of cells as well as the stability margin of them. Since, unstable cells have various oscillations and time dependent structures which change the behavior of the flow; the investigations of the stability limits is quite necessary to avoid the possible generation of unstable cells. In addition, the results are used to detect the number of cells that can be generated in the gap at different fluid column lengths. A stability map, locating the stability state of all possible numbers of cells, is assigned in the results. The map provides overlap zones between stable cells, in which the operating conditions will always lead to stable cells, even if the number of cells is changed by changing the initial conditions. Moreover, a rare phenomenon was observed during the compression process when the cells jumps unusually from six to two cells without passing through the fourcell mode.

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps Part B: Review of Experimental Investigations

“…This phenomenon means that the final pump performance changes according to the steps (history) used to reach the desired conditions, i.e., the flow rates of both phases. Hysteresis can be seen in a variety of flow applications, such as the Taylor vortex flow, where the height and number of vortices strongly depend on how the flow is initiated [49]. Similar to this, for formally identical operating points, large differences in performance can occur in centrifugal pumps when reducing the air flow rate from an initially high value or starting from zero and increasing the air flow rate.…”

Controlling the number of vortices and torque in Taylor–Couette flow

“…Similar phenomena also occur in circular Couette flow with pressure-driven axial flow (Takeuchi & Jankowski 1981; Chung & Astill 1977; Lueptow, Docter & Min 1992) or when fluid is added or withdrawn through a permeable inner cylinder (Min & Lueptow 1994; Tilton & Martinand 2018). It is found that for flow states with fewer than the nominal number of vortices, these vortices are highly stretched in the axial direction and occupy the whole liquid annulus height (Benjamin 1978 a , b ; Martínez-Arias et al 2014; Mansour, Ali & El-Maksoud 2016; Ostilla-Mónico, Lohse & Verzicco 2016). These multiple flow states have recently been found to exist even at extremely high Reynolds number () in turbulent TC flows (Huisman et al 2014), where only one flow state is expected.…”

“…These multiple flow states have recently been found to exist even at extremely high Reynolds number () in turbulent TC flows (Huisman et al 2014), where only one flow state is expected. The reported methods for generating different flow states include continuously adjusting the liquid annulus height using a sliding top plate between the inner and outer cylinders while the inner cylinder keeps rotating (Benjamin 1978 b ; Mansour et al 2016) or adjusting the starting acceleration rate of the inner cylinder (Xiao, Lim & Chew 2002; Martínez-Arias et al 2014). Further investigations showed that for the same liquid annulus height the flow state with larger number of vortices induces larger torque on the inner rotating cylinder, for both moderate (Riecke & Paap 1986; Brauckmann & Eckhardt 2013; Ostilla et al 2013; Martínez-Arias et al 2014) and very high (Huisman et al 2014).…”