Abstract
The drag reduction design of underwater vehicles is of great significance to saving energy and enhancing speed. In this paper, the drag reduction characteristics of Paramisgurnusdabryanus loach was explored using 3D ultra-depth field microscopy to observe the arrangement of the scales. Then, a geometric model was established and parameterized. A simulated sample was processed by computer numerical control (CNC) machining and tested through using a flow channel bench. The pressure drop data were collected by sensors, and the drag reduction rate was consequently calculated. The test results showed that the drag reduction rate of a single sample could reach 23% at a speed of 1.683 m/s. Finally, the experimental results were verified by numerical simulation and the drag reduction mechanism was explored. The boundary layer theory and RNG k-ε turbulence model were adopted to analyze the velocity contour, pressure contour and shear force contour diagrams. The numerical simulation results showed that a drag reduction effect could be achieved by simulating the microstructure of scales of the Paramisgurnusdabryanus loach, showing that the results are consistent with the flow channel experiment and can reveal the drag reduction mechanism. The bionic surface can increase the thickness of boundary layer, reduce the Reynolds number and wall resistance. The scales disposition of Paramisgurnusdabryanus loach can effectively reduce the surface friction, providing a reference for future research on drag reduction of underwater vehicles such as ships and submarines.
Highlights
IntroductionThe frictional resistance from water accounts for about 80%of the total resistance [1]
For underwater vehicles, the frictional resistance from water accounts for about 80%of the total resistance [1]
The flow state during the test is turbulent, so there are some differences in the values the flow state during the test is turbulent, so there are some differences in the values of each test. It can be seen from the results that the overall trend presents a dr each test. It can be seen from the results that the overall trend presents a drag reduction effect, and the relative standard deviation (RSD) is within 5%, so the test resu reduction effect, and the relative standard deviation (RSD) is within 5%, so the test results are credible
Summary
The frictional resistance from water accounts for about 80%of the total resistance [1]. The frictional resistance from water accounts for about 80%. In order to improve the power efficiency, it is necessary to reduce the surface friction of underwater vehicles. The theory of bionic tribology has become popular in the field of drag reduction in recent decades. There are two main factors affecting the tribological characteristics of a surface: the composition of the material itself and the surface structure [2,3,4,5]. The drag reduction of the surfaces could reach up to 24%. Changing the material properties or adding smooth coatings may change the original material’s performance and require high costs [8]. The research on microstructure drag reduction has become increasingly popular, and it has been applied in the fields of natural gas pipelines, airplanes, navigation, swimming suits, etc. The research on microstructure drag reduction has become increasingly popular, and it has been applied in the fields of natural gas pipelines, airplanes, navigation, swimming suits, etc. [9,10,11]
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