Particle Technology / Air Pollution – Resistance to particle entrainment In dust collection and particle control, which force most strongly resists particles getting entrained (picked up and carried) by a moving fluid stream from a surface?

Introduction / Context:
In aerosol science, environmental engineering, and powder handling, “entrainment” refers to particles being lifted from a surface and carried by a gas or liquid flow. Whether dust lifts off a wall, a pipe interior, or a filter surface depends on the balance between lifting forces (drag, lift, turbulence) and resisting forces that hold particles in place. Understanding the dominant resisting force helps in designing cleaning strategies and predicting resuspension.

Given Data / Assumptions:

• The scenario concerns particles initially resting on or attached to a surface.
• We compare generic resisting mechanisms: friction, cohesion, adhesion, and momentum (which is not a resisting force by itself).
• We need the force most directly preventing detachment/entrainment from a surface.

Concept / Approach:
Two families of interparticle forces exist: cohesive (particle-to-particle) and adhesive (particle-to-surface). For entrainment from a surface, detachment requires overcoming particle-to-surface adhesion (van der Waals, electrostatic, capillary bridges). While friction contributes to resisting sliding or rolling, the key threshold for lift-off is usually adhesion. Cohesion matters inside agglomerates, but if a single particle adheres to a wall, adhesion governs its removal.

Step-by-Step Solution:
Identify the interface: particle contacting a surface.List resisting forces: adhesion (particle–surface), friction (tangential), cohesion (particle–particle in a cluster).Determine which must be overcome to detach: adhesion primarily sets the lift-off threshold.Select “particle adhesive bonds” as the most important resistance to entrainment.

Verification / Alternative check:
Filter cleaning and wall fouling studies show that increasing humidity (capillary bridges) or electrostatic charge raises adhesion and reduces resuspension. Conversely, anti-adhesive coatings reduce adhesion and increase entrainment at the same flow conditions—evidence that adhesion dominates detachment behavior.

Why Other Options Are Wrong:

• frictional resistance: resists sliding/rolling after partial detachment; not the primary lift-off barrier.
• particle cohesive bonds: key within particle clusters, not at the wall–particle interface.
• momentum: a property of moving particles/flow, not an intrinsic resisting force.

Common Pitfalls:
Confusing surface adhesion with cohesion inside agglomerates; assuming “friction” alone determines lift-off; overlooking the role of electrostatics and capillary forces in adhesion.

Final Answer:
particle adhesive bonds