Experimental investigation of near-surface small-scale structures at water--air interface: Background Oriented Schlieren and thermal imaging of water surface

Background-oriented schlieren (BOS) techniques

“…The main limitation of the method, namely the ray crossing (caustics) due to strong curvature and/or large surface pattern distance, was presented additionally. Jin et al (2010) and Plaksina et al (2012) presented an experimental investigation of near-surface small-scale structures at water-air interface and found that the temperature measurement sensitivity is generally better than 0.1 K for such an application by comparing the result with infrared measurements. Tokgoz et al (2012) conducted temperature and velocity measurements inside a thin fluid layer using background-oriented schlieren and PIV methods by placing a reflective surface to one side of the test section.…”

Horizontal convective flow from a line heat source located at the liquid–gas interface in presence of surface film

“…Anomalous behaviour of the distilled water surface is thus attributed to the influence of surfactants present in very low concentration even in distilled water (Plaksina et al. 2012) and forming a kind of elastic surface film, which does not prevent evaporation, but inhibits the surface renewal (Vinnichenko et al. 2018 a ).…”

“…Small moving cells are observed in ultrapure deionized water, whereas distilled or tap water surfaces appear to be stagnant with large cells. Anomalous behaviour of the distilled water surface is thus attributed to the influence of surfactants present in very low concentration even in distilled water (Plaksina et al 2012) and forming a kind of elastic surface film, which does not prevent evaporation, but inhibits the surface renewal (Vinnichenko et al 2018a). This hypothesis was first proposed by Frumkin and Levich (Lohse & Zhang 2020) as an alternative to the surface viscosity concept proposed by Boussinesq.…”