Research On Bionic Superhydrophobic Surface And Drag Reduction Technology Based On Laser Processing

With the continuous progress of science and technology,the bionic surface has become a hot topic for many scholars due to its broad application prospects in medical,sports,military and transportation.How to prepare and test the performance of the bionic surface has become the focus of everyone's attention.Aiming at the drag reduction performance of superhydrophobic surface,this paper uses laser etching method to prepare superhydrophobic surface on aluminum alloy surface and conducts drag reduction test.The subject first made corresponding bionic surfaces based on the topography of the fish scale surface,lotus leaf surface and shark skin surface,and explored the influence of laser processing equipment on the surface topography,and then infiltrated the bionic fish scale surface and the bionic lotus leaf surface The sex test obtained the best wettability.The size of the bionic lotus leaf was 40 um,the contact angle reached 157°,the surface size of the bionic fish scale was 100 um,and the contact angle reached 158 °.A drag reduction test was conducted to obtain a reduction in the directionality of the surface of the bionic fish scale.Resistance effect,the difference between the drag reduction rate in the direction of the fish scale and the reverse fish scale can reach 10%-15%.According to the phenomenon that the drag reduction rate is low at two high flow rates on the surface,a bionic lotus surface using a hydrophilic-hydrophobic structure is proposed to improve the drag reduction effect at high flow rate.This structure can block the bubbles removed by high-speed water flow One side of the hydrophilic band thus increases the gas-liquid contact area.Practical tests show that the best drag reduction effect can be achieved when the hydrophilic band is 1mm apart,and the drag reduction rate of about 35% can still be maintained at a flow rate of 4.2m/s,without bionic lotus leaf without hydrophilic-hydrophobic structure.The surface has a drag reduction rate of only about 15% at this flow rate.This subject also carried out COMSOL simulation on the surface of bionic fish scale,bionic lotus leaf and the surface of bionic lotus leaf with hydrophilic-hydrophobic structure.The simulation results also proved that the experimental test results were correct and explained the simulation results.For the surface of the bionic fish scale,the state of the liquid rolling is more in line with the Cassie state without infiltration,and the area of the air-liquid interaction interface is larger,so the drag reduction effect will be better as the size of the bionic fish scale increases,when the size is 100 um The drag reduction effect is the best and the slip length is the longest.However,when the size increases to about 120 um,it graduallychanges to the Wenzel state.At this time,the drag reduction effect will become worse,and the slip length will decrease.In addition,no rolling occurred on the surface of the fish scale regardless of the size in the reverse fish scale direction.For the bionic lotus leaf surface,the surface morphology is similar to the columnar microstructure.The roughness factor is defined and brought into the Wenzel and Cassie model for calculation.It can be concluded that the smaller the element size,the better the wettability,but it needs to be compromised with the actual situation..For the bionic surface of the hydrophilic-hydrophobic structure,due to the presence of the hydrophilic channel,a larger gas-liquid contact area can be formed locally to improve the overall drag reduction effect at high flow rates.