A two-angle model of dynamic wetting in microscale capillaries under low capillary numbers with experiments

Area of Science:

• Fluid dynamics
• Microfluidics
• Interfacial phenomena

Background:

• Accurate modeling of dynamic contact angle (θd) is crucial for capillary force calculations in enhanced oil recovery.
• Existing models struggle with rate-dependence at low capillary numbers (Ca: 10⁻¹⁰ to 10⁻⁵) and low Bond numbers (Bo: < 10⁻⁴).

Purpose of the Study:

• Investigate the rate-dependence of dynamic contact angles under conditions relevant to enhanced oil recovery.
• Develop and validate an accurate model for dynamic contact angles in microscale systems.

Main Methods:

• Developed an innovative experimental system with pressure control and interface tracking.
• Enabled direct optical measurement of dynamic contact angles in microcapillaries (40×20 μm and 80×20 μm).
• Tested advancing and receding processes for wetting and nonwetting liquids.

Main Results:

• Confirmed that the dynamic contact angle is velocity-independent for Ca ranging from 10⁻⁹ to 10⁻⁵.
• A two-angle model accurately describes the observed dynamic contact angles.
• Developed a modified two-angle model with an empirical form.
• Advancing angles (θadv) approximated static contact angles (θo).
• Receding angles (θrec) showed a linear dependence on advancing angles (θadv).

Conclusions:

• The dynamic contact angle is independent of velocity in the studied microfluidic regime.
• A modified two-angle model provides an accurate empirical description of dynamic contact angles.
• Findings simplify capillary force modeling for enhanced oil recovery applications.