Contact Angle

Enable the contact angle parameter to allow different wetting behaviors.

The default wetting behavior on walls for the TARTAKOVSKY2016_F1 surface tension model is neutral with a static contact angle of 90 degrees. Enabling the contact angle parameter allows simulation of different wetting behaviors in single phase flows (the only type of flows the model is currently recommended for).

Note: When using subphase-aware contact angle and TARTAKOVSKY2016_F1 surface tension model, the total number of cfg phases is limited to 100.
Contact angle is a single value prescribed as a solid surface/boundary property. This can be set via the parameter contact_angle in the phases subsection of the .cfg file for any WALL or MOVINGWALL phase and will be ignored for fluid phases. It is measured as the angle ( θ c MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiUde3aaS baaSqaaiaadogaaeqaaaaa@38BD@ ) between solid and fluid surface with respect to the (resolved) fluid phase.

Figure 1.
An angle of less than 90 degrees develops hydrophilic behavior and an angle greater than 90 degrees develops hydrophobic behavior. Figure 2 illustrates this with a droplet on a flat surface with contact angles of 30, 60, 90 and 120 degrees.

Figure 2.
Figure 3 contains isometric, plan, and elevation views of three droplets with equal volume. From left to right the droplets are assigned contact angles of 30, 90 and 120 degrees. This illustrates that contact angle affects the particle spread and distance from the wall.

Figure 3.

Wetting behavior is highly sensitive to numerical (particles aligned on a Cartesian grid) and experimental (surface type and cleanness) setups. This parameter should not be interpreted as a precise parameter down to a single degree, but rather an estimate of the wetting behavior in general (wetting/non-wetting to certain degrees).