Author: Ala MoradianPublisher:
ISBN: 9780494395721
Category :
Languages : en
Pages : 390
Book Description
Surface tension is the dominant parameter in many fundamental studies in fluid mechanics and plays a major role in many industrial processes. Methods for measuring surface tension of liquids may vary according to different temperature ranges. The objective of this study is to propose a new methodology for measuring surface tension of materials with high melting point. In this new containerless method, an atmospheric radio-frequency Inductively Coupled Plasma (RF-ICP) torch melts horizontal metallic rods, and a high-speed camera records the drop formation process caused by melting. The drop shapes are fitted by the theoretical Young-Laplace (YL) profiles to determine the surface tension. In addition to the measurements based on the drop shapes, this methodology provides the possibility of validating the results with three other methods for measuring surface tension: the drop weight, pendant drop, and drop oscillation method. The drop oscillation method was used to measure the surface tension and viscosity, based on the resonance frequency and damping rate of the oscillations, respectively. From the photographs of the melting process, the solid-liquid interface was found to be inclined at an angle to the horizontal. The effect of this inclination on surface tension measurement is investigated. The dynamics of drop formation are modeled numerically as drop ejection from a nozzle. The numerical model solves the axisymmetric Navier-Stokes equations, for both the melt and the surrounding gas. The numerical pendant drops are compared with the theoretical YL profiles. A detailed study of the differences between numerical and theoretical profiles demonstrates some of the hydrodynamic effects influencing the surface tension measurement methods that are based on drop profiles. Good agreement between the numerical and the theoretical drop profiles validated the procedure of fitting YL profiles on dynamic drop profiles during drop formation. In addition, using the proposed methodology, surface tension values measured based on the drop shapes can be incorporated into the numerical code. Therefore, experimental drops and numerical drops can be compared and the viscosity of the melt can be determined. This method is established based on copper and nickel; however, it can be applied to metals, alloys, and ceramics.
