A Matter of Shape: Contact Area Optimization in Soft Lubricated Impact

Area of Science:

• Fluid dynamics
• Soft matter physics
• Tribology

Background:

• Understanding fluid-mediated impacts is crucial for soft matter, adhesion, and elastohydrodynamics.
• The influence of object shape on contact formation in fluid environments is not fully understood.

Purpose of the Study:

• To investigate how the shape of a deformable axisymmetric object affects contact formation during impact with a rigid substrate.
• To analyze the role of fluid entrapment and pressure distribution in these impacts.
• To explore potential design parameters for optimizing contact in soft matter applications.

Main Methods:

• Simulations of fluid-mediated impact involving deformable axisymmetric objects and rigid substrates.
• Analysis of contact formation, fluid entrapment, and pressure distributions at low approach velocities and large Stokes numbers.
• Comparison of results with classical dry contact mechanics models.

Main Results:

• Sharper object profiles (e.g., conical) maximize central contact and minimize fluid entrapment.
• Blunter profiles lead to central dimples and potential bubble entrapment.
• Pressure distributions in thin viscous films are accurately predicted by dry contact mechanics.
• A mechanical equivalence between object shape and approach velocity is theorized.

Conclusions:

• Object shape is a critical design parameter for optimizing contact in fluid-mediated scenarios.
• Findings have implications for designing soft materials, improving adhesion, and understanding elastohydrodynamic lubrication.
• The study suggests potential for simplified modeling by relating shape effects to velocity effects.