การศึกษาการดูดและผลักระหว่างแผ่นกลมบางที่ลอยบนผิวน้ำด้วยวิธีเชียเรนสังเคราะห์ของผิวอิสระ

Abstract

A Floating object on water surface causes the surface deformation from a smooth surface to a curved surface, creating surface tension from another floating object. In general, a symmetrical object floating on the water surface will also create symmertrical water meniscus around the object, which results in zero the horizontal capillary force or in other word, the object has no horizontal motion. When the floating objects are however in the vincinity of each other, water meniscus around each object is no longer in symmetry, causing a net horizontal capillary force object moves forword or away from nearby object, depended upon the nature of the curved surface between them. This research proposed the use of Free Surface Synthetic Schlieren (FS-SS) method to create three-dimensional surface characteristics of water surface around objects and to relate it to the lateral force acting floating thin disks. The results found experimentally that the FS-SS method was able to create water surface topography in three dimensions with resolution of submillimeter scale. From the study of attractive capillary force between two circular disks that are both denser than water, it was found the capillary force is in the range of 10^(-10) N to 10^(-9) N. As for the case of attractive capillary force between two circular disks that are less dense than water, the force is in the range of 10^(-12) N to 10^(-9) N. For the repulsive capillary force between two circular disks, one denser and one less dense than water, the force is in the range of10^(-13) N to 10^(-9) N . However, the forces calculated from FS-SS and from tracking the motion using Tracker program are significantly different. The main factor is due to the inapplicable of the simplified capillary force equation to the experimental conditions. Numerical method is needed in order to precisely calculate capillary force.