水下湍流减阻技术研究进展OA北大核心CSTPCD

The technology for underwater drag reduction is an effective means to enhance the speed of watercraft and achieve energy-saving and emission reduction goals.It holds significant economic value and promising prospects,thus attracting extensive attention from scholars.Over the course of its development,various drag reduction technologies have been formed based on different mechanisms and categorized into active drag reduction technologies and passive drag reduction technologies depending on their controllability.The work aims to conduct a comprehensive overview of research on turbulence drag reduction technologies,aiming to provide a detailed examination of the progress and impact of various techniques.The developmental trajectory of each drag reduction technology is systematically traced from their inception to current research highlights.Additionally,the impact mechanisms of these technologies on near-wall turbulent boundary layers are explored thoroughly,shedding light on their inherent drag reduction mechanisms. Biomimetic structure drag reduction is built upon the "protrusion height" theory,drawing inspiration from natural structures.Superhydrophobic drag reduction takes a different approach by capitalizing on the "velocity slip" theory,utilizing surface properties to minimize drag forces.On the other hand,polymer drag reduction leverages the "viscoelasticity" theory,introducing polymers into the fluid to modify its dynamic behavior.Innovative technologies such as supercavitation and microbubble drag reduction employ unique strategies.Supercavitation focuses on creating supercavities,while microbubble drag reduction uses bubbles to establish a separation between the fluid medium and the surface,thereby mitigating drag effects.Compliant wall surface drag reduction,incorporating "elastic vibration",aims to dynamically adapt wall surfaces for effective drag reduction.Additionally,wall oscillation or blowing drag reduction directly targets the large vortex structures on the wall,exerting effect to reduce drag. The development trends and limitations of various technologies are concluded.For instance,biomimetic drag reduction structures inspired by underwater creatures like sharks or pufferfish can reduce wall friction drag by altering the turbulence boundary layer flow coherent structures,thus sustaining a long-lasting drag reduction effect without the need for additional energy input,but may struggle to maintain high drag reduction in complex and variable flow environments.Microbubble drag reduction can create micro bubbles by aeration or electrolysis on the wall surface to separate the contact surfaces from the underwater fluid,which greatly reduces the viscous drag of the flow fields to the contact surfaces.Nonetheless,it comes with the drawback of higher energy consumption.Superhydrophobic surfaces are capable of inducing velocity slip in the near-wall turbulence boundary layer of the fluid medium,leading to noticeable drag reduction effects.Nevertheless,they are susceptible to issues like coating exfoliation corrosion and degradation,making them prone to reduced effectiveness. Based on these foundations,the study offers a perspective on the future directions of underwater drag reduction technologies from a technology integration perspective.At present,single drag reduction technology faces challenges in maintaining high levels of drag reduction effectiveness in complex flow fields.Therefore,combining multiple drag reduction technologies is essential to achieving more pronounced cumulative drag reduction effects.With the rapid development of micro and nanomanufacturing,it is becoming increasingly feasible to fine-tune flow fields.This paves the way for the integration of various drag reduction technologies,such as anti-fouling,hydrophobicity,microstructures,deformations,and bubbles may be integrated into actively controlled surfaces,leading to the birth of a multifunctional intelligent drag reduction skin.