Aerodynamic Entrainment and Resuspension cont'd

DOE-HDBK-3010-94

5.0 Surface Contamination; Solid, Noncombustible Surfaces

There are two general conceptions for aerodynamic entrainment - force balance and energy

balance. The force balance concept is that aerodynamic lift/drag forces exceed the adhesive

forces causing particles on the surface of the substrate to be suspended. Most authors have

subscribed to the force balance concept. Recently, Reeks et al. (May 1985a, May 1985b,

June 1985a, June 1985b, 1988) have proposed an energy balance concept that postulates

resuspension of small (<100 m diameter) particles by energy transfer from turbulent flow.

The concept is similar to removal of molecules from surfaces by Brownian motion. Energy

maintains the particle in motion at the surface within the surface potential well. Particles are

suspended when they accumulate sufficient vibrational energy to escape the potential well.

Authors (Reeks et al., May 1985a, Wright, 1984) have reported suspension of large fractions

of deposited particles during the buildup to test velocities. Wright (1984) reports that the

initial suspension of 95% of the deposited particles on the floor of a wind tunnel during

an air velocity increase to 60 m/s (~ 135 mph). Braaten, Shaw and Paw U (1986) reported

negligible loss during an increase to 20 m/s in a wind tunnel. John, Fritter and Winklmayr

(1991) found some suspension of 8.6 m sodium fluorescein particles when filtered air at

40 m/s from a nozzle was impinged upon the Tedlar surface. The point may be moot for the

conditions covered here since the material is continually subjected to at least some air flow

during deposition and any suspension occurring in the initial seconds would be lost with the

release from the occurrence. Garland (1982), Corn and Stein (July 1965), Cleaver and Yates

(1973) and Wright (1984) found resuspension fluxes inversely proportional to time (decayed

with time) while Sehmel and Lloyd (1976) did not find any apparent decay over a 21-month

test period.

A vast array of literature exists on various aspects of the resuspension of sparse particles

from the surface of substrates (Corino and Brodkey, 1969; Corn, 1966; Dahneke, January

1975; Ettinger, 1974; Fairchild, 1982; Fish, 1967; Hall, 1988; Hubbe, 1984; Larsen, August

1958; Nelson, 1973; Punjrath, 1972; Spenser, 1976). Zimon's (1969) text book provides a

good theoretical background of the topic. More recently several reviews (Brockman,

February 1985; Fromentin, January 1987; Alonso, Bolado and Hontanon, July 1991) directed

towards the dry resuspension of particles in light water reactor coolant systems during the

depressurization of the containment following a severe core disruptive events have been

published. In general, most of the experimental data have been obtained on sparse particle

suspension from heterogeneous substrates with few field studies that is the converse of the

situations for suspension from homogeneous beds covered in section 4.4.5. Fromentin

(January 1987) concluded from his review that:

Both theoretical and experimental studies of the suspension of solid particles

from solid surfaces are still in an elementary state.

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