Flow visualisation demonstrating surface-tension driven convection in the weld pool

Surface-tension driven convection in the weld pool has the most profound effect on the shape of the resultant weld among various types of convection. However, the existence of the surface-tension driven convection in weld pools is difficult, if not impossible, to demonstrate in a laboratory. Therefore, it also becomes difficult for students or even engineers to understand. This paper addresses the flow visualisation technique and the special design of the simulated weld pool. They allow convection to be clearly observed without any optical distortions and render certain properties of fluid flow accessible to visual perception so that the insight of a surface-tension driven convection in the welding process can be better understood. The recorded video clips of flow visualisation can serve as an effective instructional aid for engineering students and engineers in related fields as well as help them to appreciate the importance of surface-tension driven convection in weld pools. This demonstration on how to apply the flow visualisation technique is an example of the effort to increase the effectiveness of engineering education.