A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern.The fastest fish have a very sharp convex nose(rostrum),the purpose of which remains unclear.The bodies...A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern.The fastest fish have a very sharp convex nose(rostrum),the purpose of which remains unclear.The bodies of revolution similar to their shapes are analyzed in steady underwater and floating motion.The sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water surface.It was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface elevation.These fact allow diminishing the maximum pressure on the surface and wave drag.Special shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls.展开更多
An amendment to the speed property theory by Japanese professor Kumabe is proposed. A large number of experimental investigations show that ultrasonic vibration cutting in unseparating zone presents not a mono state b...An amendment to the speed property theory by Japanese professor Kumabe is proposed. A large number of experimental investigations show that ultrasonic vibration cutting in unseparating zone presents not a mono state but many states. This result has broken through the restriction of the critical cutting speed on ultrasonic vibration cutting.展开更多
文摘A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern.The fastest fish have a very sharp convex nose(rostrum),the purpose of which remains unclear.The bodies of revolution similar to their shapes are analyzed in steady underwater and floating motion.The sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water surface.It was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface elevation.These fact allow diminishing the maximum pressure on the surface and wave drag.Special shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls.
基金Project Supported by the National Natural Science Foundation of China
文摘An amendment to the speed property theory by Japanese professor Kumabe is proposed. A large number of experimental investigations show that ultrasonic vibration cutting in unseparating zone presents not a mono state but many states. This result has broken through the restriction of the critical cutting speed on ultrasonic vibration cutting.
