Dynamic contact angle effects onto the maximum drop impact spreading on solid surfaces

Abstract

This paper reports experimental investigations of drop impacts onto chemically treated surfaces with wettability from 5° to 160°. To follow in time the drop spreading, a high speed video camera was used, and it allows us to determine precisely the expansion of the drop and the profile of the free surface at the contact line. By changing the impact velocity, between less than 0.5 and 5 m/s, and the viscosity, from 1 to 100 mPa s, at constant surface tension, a broad range of Reynolds and Weber numbers is explored. This paper is divided into two parts. In the first part, the experimental drop evolution during spreading is directly reported and compared with previous works. Secondly, the emphasis is on the importance of the apparent dynamic contact angle for the prediction of the maximum spreading diameter. This achievement is manifested at low Reynolds numbers at which the matching between the experiment and the model is improved greatly.

Physicochemical Characteristics and Droplet Impact Dynamics of Superhydrophobic Carbon Nanotube Arrays

“…Compared to other published models of β, 21,23,29 , the model given by Eq.17 gives the best agreement to the experimental data ( Figure S4). …”

“…Since the first term of Eq.14 is smaller than the second term, it is reasonable to drop the first term from Eq.14. 21,23 . In addition, for superhydrophobic surfaces with θ s ≥ 150°, the value of cos θ s is close to unity.…”

“…Weber number is considered as the most important parameter mainly because of its appearance in the energy balance of the droplet, which has been discussed in detail elsewhere, [17][18][19][20][21][22][23] and to avoid competition between two main components of kinetic energy, i.e. v i and d i .…”

Maximum Deformation Ratio of Droplets of Water-Based Paint Impact on a Flat Surface

“…Therefore, the results agree well with the theoretical solutions. Based on the research of Vadillo et al [18], the contact diameter is determined by …”

“…As shown in Figure 5, the simulation result is in accordance with the prediction model of Vadillo et al Therefore, the Navier-Stokes equation coupled with the level set method can be used to simulate the dynamics of droplets after the impact onto the solid surface. Based on the research of Vadillo et al [18], the contact diameter is determined by    …”