A PIV Study of Natural Convection Induced by Oscillating Thermal Gradients

Microscale fluid flow and mass transfer are of both fundamental and practical importance to the design of solidification systems for melt processing of materials. These microscale fluid flow phenomena are affected by the macroscopic bulk flow motion and heat transfer away from the solidification front. As a first step towards a systematic understanding of the interactions of the micro- and macro-scale phenomena, a miniature cavity of a few millimeters in size is considered, where an oscillating temperature gradient is established to simulate the driving force under perturbed solidification conditions typical of microgravity environments. Flow visualization and velocity measurements of the transient oscillating fluid motion under two sets of thermal conditions are conducted using the Particle Image Velocimetry (PIV) technique. These experimental results are used to validate numerical simulations carried out using a finite element based model, developed by the authors for the prediction of flows in microgravity environments. The visualized flow pattern and velocity measurements in the two test cases compare very well with the numerical simulations. The numerical model is now ready to be used as a reliable tool for understanding and predicting the structure of fluid flow and heat transfer in microgravity environments.