Study of pressure-sensitive effects on the flow of nanobubbles on wetted surfaces

The slip of nanobubbles has been considered to be the result of a single effect of wettability; however, the pressure-sensitive properties of the fluid also affect the flow properties of nanobubbles. An alcohol-water exchange nanobubble nucleation and nanolimited domain flow model considering pressure is constructed, and the nucleation state of nanobubbles with different wettability surfaces under pressure and its effect on the slip properties are analyzed. During the nucleation of alcohol-water exchanged nanobubbles, pressure increases the nucleation capacity of the nanobubbles by changing the solubility of the gas in a water solution. The hydrophilic and hydrophobic properties determine their bulk and surface nucleation states. The pressure is unable to transfer bulk nanobubbles (BNBs) to hydrophilic surfaces. The low pressure drives the transfer of BNB to the hydrophobic surface, increasing the surface gas coverage and hence the interfacial slip. The high pressure leads to an increase in the density of nanobubbles and also reveals that the change in the gas–liquid interfacial tension due to the density of surface nanobubbles is a key factor affecting the interfacial slip at different pressures. The greater the gas–liquid interfacial tension, the greater the slip length. The high density and high coverage gas coupling of the interface creates a better slip effect under high pressure conditions.