| Global warming has become a common challenge in the world.China has issued a series of policies such as the "13th Five-Year Plan" to actively respond to energy issues,and the development of the shipping industry is highly dependent on energy.With the implementation of the maritime power strategy,the performance requirements for reducing drag and consumption of marine vessels have been further improved.Bionic non-smooth surface technology has become a hotspot of drag reduction research because of its advantages of strong designability,high stability,environmental protection and economy.In this technology,the selection of bionic objects and the rationality of research methods are the main factors affecting the drag reduction effect.Puffer has a good ability to reduce drag and consumption,and the ability has been initially verified through simulation experiments and water tunnel experiments.In this paper,the puffer spines were taken as the research object,and its size distribution,structural characteristics and drag reduction performance were analyzed and optimized using modeling techniques,simulation experiments,water tunnel experiments,and theoretical foundations.The drag reduction performance and spatial flow characteristics of the non-smooth curve surface of the bionic spines were further studied.By this work,the further understanding of the drag reduction performance of the puffer spines structure is made,and the foundation is laid for the study of the bionic non-smooth surface of the puffer.Mainly research contents were carried out shown as the following.First,based on the image processing technology and curve fitting method,an accurate contour model of the puffer spine was established and the feature size was obtained.The model fitting determination coefficient reaches 0.9954.On this basis,the non-smooth surface model of the spine was established by orthogonal test method for simulation.In addition,the effect of the spine structure on the boundary layer flow field and the drag reduction mechanism of the non-smooth surface were analyzed.The non-smooth surface of the spine effectively reduced the wall shear stress and Reynolds stress,and a special "climbing vortex" phenomenon occurred,thereby reducing the surface viscous friction resistance and achieving drag reduction effect.The work revealed and verified the drag reduction performance of puffer fish spine.Next,to optimize the drag reduction ability of the non-smooth surface of the spine,a concave-like model was proposed,and the drag reduction characteristics of the spine feature(r,R)were analyzed and compared through simulation.In addition,the cone model and the convex-like model was established under the same conditions,then the drag reduction effect and flow field structure of the three bionic spine models were compared and analyzed to determine the best optimized model and size.The results showed that the non-smooth surfaces of the three models can achieve a good drag reduction effect,and the structure has a small effect on the viscous friction resistance and a large influence on the differential pressure resistance.The concave-like model has the best drag reduction effect,and the drag reduction rate can reach 13.83%,which provides a surface structure with a high drag reduction effect.Finally,based on the results of the flat panel study,the flow field characteristics of the optimization model on the curve body surface were further studied.The rotational body model was designed reasonably,and the smooth surface was tested using the water tunnel platform combined with PIV technology,which verified the feasibility of the simulation method.Through the simulation test of the non-smooth surface of the rotational body,the drag reduction characteristics of the shape factor were analyzed,and the explanation was combined with the flow field.The results showed that the concave-like model can achieve a good drag reduction effect on the curved surface.At a flow rate of 2.8m/s,the drag reduction rate reached 8.5%,and the primary and secondary factors affecting the drag reduction rate were R-H-L-r.It lays a foundation for further research on the optimization,coupling and application of bionic spines on non-smooth surface drag reduction. |
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