This paper reveals the results of a study of vortex air core formation (Rankine vortex) when a rotated liquid (water) column in a cylindrical vessel is drained through two ports located at equal eccentricity (e) at the vessel base (diameter, 1 and 2) simultaneously; 1 is fixed whereas 2 is varied. Just before draining, a rotation (n rpm) is provided to the liquid column in controlled conditions. As draining progresses, when the liquid level reaches certain height called critical height (ℎ), initially a surface dip forms which further develops in to a vortex extending down till the drain port. Results show that critical height increases as the fluid rotation rate increases at the lowest eccentricity. But, at higher eccentricities, ℎ , exhibits more or less an increasingdecreasing trend in most of the cases studied. Critical height is observed to be minimum for the largest value of 2 (equal to 1) irrespective of the values of the speed of fluid rotation, liquid initial height and port eccentricity. To particularly note, at the highest eccentricity, vortex formation is found to be completely suppressed for all values of port diameter (2) and initial fluid rotation (n) as indicated by the near-zero critical height values. The tangential velocity measurements using Particle Image Velocimetry are also reported. PIV results obtained for certain cases with induced fluid rotation (normal draining and faster draining) correlate well with the changes in the efflux (axial) velocity (deduced analytically) in these cases studied. The tangential velocity along radial direction obtained (PIV) also indicated the type of vortex formed in normal and faster draining cases. Video visualization of vortex formation carried out reveals that, vortex air core switching takes place between the drain ports maintaining an arched or curvilinear surface profile apart from demonstrating the nature of outlet flow discharge. All the vortex air core formation studies so far carried out were invariably with single drain port except the preliminary novel study by the same author group and the present study is a detailed extension of that novel study.
Nominally two-dimensional air flow over a thin flat plate at low Reynolds number is investigated. The primary objective is to experimentally determine with good accuracy the small magnitude lift force, generated by the plate at various angles of attack, by means of application of the Kutta-Joukowsky theorem where circulation is obtained from the line integral of velocity around the flat plate using non-invasive laser doppler velocimeter. Specific focus is on assessing applicability of the KuttaJoukowsky theorem, originally theorized for inviscid and steady flow, in the post-stall region. At high angles of attack, due to severe flow separation from both the edges of the flat plate and occurrence of periodic vortex shedding, wake flow is found to be highly viscous, turbulent and unsteady. Nevertheless, the results show a remarkably good agreement with previous investigations in both the linear range and the non-linear range of the lift curve without any correction applied to the data. The line integral of velocity along the rectangular loop enclosing the flat plate shows that the vertical components, albeit smaller in magnitude, possess the same sign and hence are additive in contribution to the circulation, whereas the horizontal components possess opposite signs and hence are subtractive in their contribution to the circulation. The paper presents some interesting and hitherto undisclosed features of flow field around the flat plate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.