We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end ...We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end of the cylinders remain stationary. The upper top boundary is the free surface of the working liquid between the inner and outer cylinders and it contacts with the air. While this flow appears in fluid machinery and chemical reactors and includes industrial interests, it also contains problems of fluid mechanics, which is about the behavior of the free surface in the rotating field. In this paper, we concretely show the developments of the one cell mode flow and the three cell mode flow at a small aspect ratio. We also represent the bifurcation diagram of the flow at the moderate aspect ratio about 5.5. In the numerical simulation, the flow is rest in the initial state, and the inner cylinder is linearly or suddenly accelerated to attain a flow with a prescribed Reynolds number. When the acceleration of the inner cylinder is high, an imperfect bifurcation occurs and the flows of the secondary modes emerge. At high Reynolds numbers, the flow first has many vortices and then some of the vortices collapse and the final stable flow arises. The loci of the normal five cell mode, the anomalous six cell mode and the secondary seven cell mode are determined.展开更多
The step-flow growth condition of Si on Si（111） near the （7×7）-＂1×1＂ surface phase transition temperature Tc are analyzed within the framework of Burton- Cabrera-Frank theory. In particular, coexistenc...The step-flow growth condition of Si on Si（111） near the （7×7）-＂1×1＂ surface phase transition temperature Tc are analyzed within the framework of Burton- Cabrera-Frank theory. In particular, coexistence of both surface phases well below Tc and their specific influence on the step-flow growth behavior are considered. We presume that under dynamical condition of growth, the surface initially covered by only the （7×7） phase separates into domains surrounded by ＂1×1＂ areas. On such a surface, the overall supersaturation should be reduced drastically compared to a surface with only （7×7）, resulting in much larger critical terrace width for nucleation.展开更多
文摘We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end of the cylinders remain stationary. The upper top boundary is the free surface of the working liquid between the inner and outer cylinders and it contacts with the air. While this flow appears in fluid machinery and chemical reactors and includes industrial interests, it also contains problems of fluid mechanics, which is about the behavior of the free surface in the rotating field. In this paper, we concretely show the developments of the one cell mode flow and the three cell mode flow at a small aspect ratio. We also represent the bifurcation diagram of the flow at the moderate aspect ratio about 5.5. In the numerical simulation, the flow is rest in the initial state, and the inner cylinder is linearly or suddenly accelerated to attain a flow with a prescribed Reynolds number. When the acceleration of the inner cylinder is high, an imperfect bifurcation occurs and the flows of the secondary modes emerge. At high Reynolds numbers, the flow first has many vortices and then some of the vortices collapse and the final stable flow arises. The loci of the normal five cell mode, the anomalous six cell mode and the secondary seven cell mode are determined.
基金financially supported by grants from the National Natural Science Foundation of China (No. 51422301)Beijing Higher Education Young Elite Teacher Project (No. 29201493)the Fundamental Research Funds for the Central Universities(No.YWF-16-BJ-Y-68)
文摘The step-flow growth condition of Si on Si（111） near the （7×7）-＂1×1＂ surface phase transition temperature Tc are analyzed within the framework of Burton- Cabrera-Frank theory. In particular, coexistence of both surface phases well below Tc and their specific influence on the step-flow growth behavior are considered. We presume that under dynamical condition of growth, the surface initially covered by only the （7×7） phase separates into domains surrounded by ＂1×1＂ areas. On such a surface, the overall supersaturation should be reduced drastically compared to a surface with only （7×7）, resulting in much larger critical terrace width for nucleation.
