Simulation Study on the Screening of Hydrophobic Surface Materials for Pipeline Drag Reduction Based on Adsorption Properties

Abstract

Hydrophobic surface drag reduction techniques are effective in reducing the frictional resistance of fluids, the adsorption of liquid molecules on hydrophobic surfaces can reflect the resistance to fluid flow through such solid surfaces. Based on molecular simulation technology, we investigate the adsorption characteristics of water molecules on hydrophobic surfaces to achieve rapid screening of hydrophobic materials in fire-fighting water supply systems. The Monte Carlo method was used to simulate the adsorption process of polymers and to analyze the effects of temperature and fixed adsorption quantity. Contact angle tests were also done to verify polymer hydrophobicity. The isothermal adsorption heat, water molecule distribution, and energy distribution were studied by molecular mechanics and molecular dynamics methods. Then, adsorption localization simulations and electrostatic potential distributions were used to predict possible adsorption sites on hydrophobic surfaces and single-molecule chains. Finally, the interaction energy, diffusion coefficient, and free volume were investigated to explain the adsorption mechanism at the molecular level. Simulation results show that, overall, PTFE was more hydrophobic and PES was more hydrophilic and at 298 K, the number of adsorbed water molecules was ranked as follows: PTFE < PVDF < PVC < PMMA < PPS < CSM < BD-HDI < BD-MDI < BD-TDI < PES. Furthermore, PTFE, PVDF, PVC, PES, and PPS have more stable adsorption configurations on the (0 −1 0) surface. According to the findings, hydrogen bonding dominates the interaction between water molecules and hydrophilic polymers, whereas π−π interactions increase water molecules' diffusion resistance in polymers with benzene rings. In addition, PES contains many sulfone groups and ether bonds, which disorganize the chain arrangement to provide more free volume, whereas the water adsorption rate of PTFE is reduced because its molecular chains are less convoluted and more organized.

Computational Study of Metal‐Organic Frameworks for Hydrogen Sulfide Adsorption: Grand Canonical Monte Carlo and Molecular Dynamics Simulations

“…In the molecular dynamics simulation section, the Dynamics module in the ‘Focite’ was used, using the NVT system synthesis, and the Berendsen temperature control method. The accuracy was selected as Ultra‐Fine, the simulation step size of 500 ps, and the step interval of 1.0 fs [36] …”

“…The accuracy was selected as Ultra-Fine, the simulation step size of 500 ps, and the step interval of 1.0 fs. [36]…”