Numerical study on the effects of liquid parameters on sclerosing foam coalescence

Foam sclerotherapy is a simple and easy minimally invasive treatment for varicose veins, but foam stability is a bottleneck in the treatment. The foam-coalescence pattern can reveal the process of foam decay, whereas the effects of fluid parameters can characterize the decay patterns under various conditions. This study is instructive for clinical and research purposes. Four liquid parameters were considered by the addition of surfactant P-188 to change the liquid properties. A simplified four-foam basic unit model was developed. Two-phase flow calculations were performed in ANSYSA Fluent with grid-independence verification, and post-processing was performed using Tecplot 360. As the concentration of P-188 increased from 0 to 12%, the foam-coalescence time gradually increased from 0.28 to 0.35 ms at a growth rate of approximately 25%. The coalescence of the unit foam group of the four foams finally approached a spherical shape. The first consolidation consumed 0.03 ~ 0.05 ms, and the velocity increased sharply to 1.0 ~ 1.2 m/s in the second consolidation. The greater the concentration of P-188, the later the peak appeared. A simplified spatially stereoscopic coalescence model was developed, and the foam-coalescence time was found to increase linearly with increase in the surfactant concentration. It was revealed that foam coalescences under different conditions mainly included the coalescence proximity effect of the pressure gradient field and the repulsion effect of the vortex on the bubble surface. This paper serves as a basis for the design of more macroscopic foam-stability experiments and paves the way for ideas achieving the stability of sclerosing foam.