Narrow Results

In order to increase more greatly the measurement accuracy for the laser tracking system in measuring the moving body, a laser beat-wave interferometry method is approached based on the absolute measuring distance. The He–Ne laser with the two hot steady frequency modes is used as the light source for the laser tracking system. The light source developed by us not only has the advantages of steady frequency, high precision and strongly anti-interference capability, but also it mainly has the same character in the shoot stability degrees and laser frequency stability degrees. By using the laser beat-wave interferometry method, we can realize the absolute distance measurement of the moving body, and the laser tracking system has very high measurement precision, fast tracking speed and anti-interference capability.

Water entry of a solid through the free surface is a persisting field of research in ship hydrodynamics applications. Indeed, the knowledge of pressure forces acting on structures is necessary to ensure the verification of safety criteria in the design and operation. However, in water entry problems, jets can be generated, thus an effective numerical model is needed to capture this complicated breaking water surface. In this paper, the level set method is adopted, which has been shown to be capable of capturing interface evolution when the topological change of shape is extremely large, or merging, breaking and pinching occur. Moreover, the incorporation of an immersed boundary method with this free surface capture scheme implemented in a Navier-Stokes solver allows the interaction between fluid flow with free surface and moving bodies of almost arbitrary shape to be modeled. The developed Level-Set Immersed Boundary Method is applied to simulate the water entry of a rectangular body with different velocities into the still water. The complicated surface profile, velocity field and pressure are obtained. The simulation is also carried out for the same body exiting the water, and some preliminary results are presented.