Application of PIV for Virtual Mass Coefficient Measurement

Abstract

The particle image velocimetry (PIV) technique is employed for the measurement of the virtual mass of a submerged object, an important parameter in the two-fluid model, particularly so for reactor thermal-hydraulic and safety analyses. Instead of carrying out the measurement through traditional transient processes that mix steady-state drag, virtual mass force, and Basset force, a new PIV approach is developed for steady-state flows through the integration of the fluid kinetic energy around the object. The Basset force, an inseparable transient force in viscous flows, is eliminated in the new approach, making virtual mass quantification possible. This new method has been applied to the virtual mass measurement of a solid cylinder, and although the measurement uncertainty from the flow’s random fluctuations is substantial, the results are very encouraging. The results suggest that the existence of drag force in viscous flow affects the virtual mass, as the flow field is different from the ideal potential flow. When the measurement method was applied to the quantification of air bubbles, no reliable data were obtained due to complications from bubble lateral motions and deformation. Further study is needed for the PIV method to be employed for bubble virtual mass force measurements under steady-state flow conditions.