This paper reports an experimental study on the combined effect of drain port eccentricity and port diameter on air core vortex formation in a cylindrical tank with a rotating liquid column. The study is motivated by the need to control air core vortex formation in applications like propellant feed systems of rocket engines. Based on a series of experiments in a water tank with varying discharge port diameter and port eccentricity values, the study shows how the vortex formation can be suppressed using an appropriate combination of diameter and eccentricity of the discharge port. Experiments are carried out over a range of values of initial speed of rotation (60–200 rpm) of the water column. The height of the water column at which the air core vortex extends to the discharge port, is used as a measure of the vortex growth rate. The study proposes a correlation between the critical port diameter (which suppresses vortex formation) and port eccentricity. The intermittency of vortex formation in the eccentric port configuration is also studied using flow visualization.

The phenomenon of air core vortexing in liquid draining through cylindrical tanks can have serious adverse effects on many engineering systems. Hence, suppression of such vortices is necessity in these applications. In the present work, the influence of initial rotation on vortexing phenomenon with different drain port configurations with constant port diameter (d = 10 mm) are investigated using multiple ports. In all the configurations considered, there is a concentric port (circular) in common surrounded by other ports (circular) placed equidistant from the center. In this paper, vortexing phenomenon is studied by varying the number of surrounding ports and their eccentricity. Draining is allowed through one or more surrounding ports simultaneously. Before draining, circulation is provided to the liquid column by means of rotation (40–240 rpm) using a motorized stirrer where rotational speed can be controlled. Results of this study reveal that for all the drain port configurations, as eccentricity increases, the vortex gets suppressed and hence the draining time decreases. The result also shows that the central port is the key contributor to the vortex formation and for lower values of eccentricity, as the number of surrounding ports increases, vortex is progressively suppressed. Literature reveals that all vortexing studies reported so far were either with single or two drain ports. On multiple drain ports (number of drain ports more than 2), no investigations have ever been reported. Hence, the current study is the first of its kind being presented in this paper.

This paper study the influence of roughness of the tank base in the formation of air core vortex when liquid inside the cylindrical tank is rotated and subsequently drained. The vortex air core formation in drain tanks can lead to the blockage of drain port and can result in reduced discharge of draining liquid as an immediate consequence. The formation of such a vortex in propellant tanks of spacecraft and rockets will lead to underutilization of propellants and can adversely affect the performance of rocket engines. Ingestion of air core vortex in metal casting process can affect the mechanical properties of casted metal. Hence, suppression of air core vortex is inevitable in the fields of aerospace, metal casting and other hydraulic engineering systems. Current study makes use of roughness of the tank base to suppress vortexing which is the first of its kind and therefore, novel. Experimental investigations have been carried out at several values of roughness height and initial fluid rotation to study the characteristics of air core vortex. It is found that at the highest value of initial rotation provided to the liquid, air core vortexing can be subdued up to 25% by making use of base roughness. Current study also recommends drain tank manufacturers not to smoothen the tank base surface spending time at extra cost. In addition, applying roughness on the tank base will further weaken the formation of air core vortex, in the light of this study.

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