Simulation And Experimental Study On Rebound Dynamics And Impact Outcomes Of Droplet Impact

When droplets impact a solid surface,they undergo spreading and retraction kinetics,resulting in impact product phases such as adhesion,splashing,breakup,or rebound,which are widely used in inkjet printing,self-cleaning,anti-icing,etc.Contact time,as one of the most important parameters to characterize the droplet rebound property,has received a lot of attention from researchers.At present,most scholars have carried out extensive research on the impact product phase and contact time of droplets impacting superhydrophobic surfaces.However,droplets can also rebound on impact with hydrophobic surfaces.However,there are few studies on the product phase and contact time of droplet impact on hydrophobic surfaces and no scalar relationship based on contact time on hydrophobic surfaces has been established.Therefore,it is of great importance to research the contact time and product phase of droplets impacting hydrophobic surfaces.Firstly,the kinetic properties of droplets impacting horizontal hydrophobic surfaces were investigated by means of lattice Boltzmann method(LBM)simulations.It was found that the retraction characteristics of impacting droplets on hydrophobic and superhydrophobic surfaces are significantly different,resulting in their contact times on impacting hydrophobic surfaces no longer following the scalar relationship of contact times on impacting superhydrophobic surfaces.In addition,when the impact Weber number is We=15～35 and the Reynolds number is Re=235～359,the spreading time of the impacted droplets on the surface is largely unaffected by surface wettability,impact Weber number,and Reynolds number;And its retraction time is mainly influenced by the surface wettability.Based on this,a scalar relationship between retraction rate and surface wettability was established,which reveals the mechanism of the influence of surface wettability on the kinetic behavior of droplets impacting hydrophobic surfaces.The final scalar relationship for the contact time of an impacting droplet on a hydrophobic surface was established.This study provides a theoretical basis for calculating the contact time of a droplet impacting a hydrophobic surface.Secondly,the dynamics of droplets impacting an inclined hydrophobic surface were studied with the help of LBM simulations.It was found that the surface inclination had no effect on the contact time.When the impact Weber number is We=15～45,the spreading time of droplets on the surface is basically not affected by the surface wettability and impact Weber number;while their retraction time is affected by the surface wettability and impact Weber number.Based on this,the scalar relationships of retraction rate with surface wettability and Weber number were established to reveal the mechanism of the influence of surface wettability and Weber number on the kinetic behavior of droplets impinging on hydrophobic surfaces.The final scalar relationship for the contact time of an impacting droplet on an inclined hydrophobic surface was established.This study provides a theoretical basis for calculating the contact time of a droplet impacting an inclined hydrophobic surface.