  Contact angle is an essential characteristic in wetting, capillarity and
moving contact line; however, although contact angle phenomena are effectively
simulated, an accurate and real-time measurement for contact angle has not been
well studied in computational fluid dynamics, especially in dynamic
environments. Here, we design a geometry-based mesoscopic scheme to onthesport
measure the contact angle in the lattice Boltzmann method. The computational
results without gravity effect are in excellent agreement with the benchmarks
from the spherical cap method. The qualities of the scheme are further verified
in gravitational environments by simulating sessile and pendent droplets on
smooth solid surfaces and contact angle hysteresis on chemically heterogeneous
surfaces. This scheme is simple, efficient and requires only the local data. It
is independent of multiphase models and can be easily extended to 3D dynamic
contact angle measurements.
