Aerodynamic Entrainment and Resuspension

DOE-HDBK-3010-94

4.0 Solids; Powders

4.4.4 Aerodynamic Entrainment and Resuspension

Particles can be entrained from a surface in two configurations: 1) entrainment of particles

from the surface of a homogeneous bed (e.g., relatively flat pile of powder, soil), and 2)

entrainment of particles from sparse deposits on a heterogeneous surface (hard, unyielding).

Since the entrainment of particles is a function of the characteristics of the flow, particles and

surface, the entrainment of particles from the surfaces can be substantially different.

Entrainment from homogeneous beds is discussed in this subsection covering powders

exposed to normal air flow characteristics. The entrainment from sparse deposits on hard,

unyielding surface will be covered in the subsection discussing aerodynamic entrainment of

surface contamination (section 5.2.4).

The suspension of particles from the surface of a homogeneous bed (includes powders and

contamination on soil) under routine process (stable ventilation flow velocities and patterns

indoors) and meteorological (steady windspeeds less than 5 m/s) conditions appears to be

dependent upon the interaction of various factors such as source, surface, upwind

topographical and flow characteristics.

4.4.4.1

Entrainment From the Surface of a Homogeneous Powder Layer

4.4.4.1.1 Review of Literature on Resuspension Phenomenon, Factors, and

Rates. Sutter (May 1982) reviewed much of the known information and data for

resuspension factors and rates and fractional releases. Both suspension by aerodynamic and

mechanical stresses are covered.

Resuspension factors are defined as the ratio between the airborne concentration of a

pollutant per cubic meter directly over a contaminated surface and the areal pollutant surface

contamination. The units are meters-1. In concept, the factor represents the uniform

concentration above a contaminated surface at whatever height. As measured, the factor

represents the airborne concentration of a pollutant measured at some height above the

surface collected over some period of time versus the surface contamination without

knowledge of what is the true inventory-at-risk. The relationship may have some relevance

for indoor (static volumes and relatively reproducible conditions) but does not appear to

reflect the physics of the situations outdoors.

For outdoor situations where the contaminated surface is predominantly soil (although

contamination can be resuspended from vegetation, asphalt roadways, rocks, buildings

surfaces, etc.) and the aerodynamic or mechanical stress can be imposed from many

directions and levels, the situation is much more complex. Particulate contamination is

assumed to agglomerate (become attached) with the soil particles. The removal and

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