Page 476 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 45 1
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
8 2001 Elsevier Science Ltd. AI1 rights reserved

FLOW BEHAVIOR AROUND TANDEM OIL FENCES

Dong Gi Han', Choung M. Lee' and Sang J. Lee'

'Department of Mechanical Engineering
Pohang University of Science and Technology, Korea

ABSTRACT

The present paper presents the results of the experimental and numerical investigation on the flow and
oil droplets behaviors about a set of tandem oil fence deployed in a uniform current. A numerical
solver of the Reynolds averaged Navier-Stokes equation and the Lagrangian particle trajectories are
utilized to trace the oil droplets around the two fences, and assessment of the effectiveness of a tandem
fence is made. Laboratory experiments are carried out to check the validity of the numerical
predictions.

KEYWORDS
Oil fcncc, Oil leakagc, Flow passing a tandem fence, PIV method, Lagrangian particle-tracking
method, Free-surface effect , Entrainment failure, critical leakage zone.

1 INTRODUTION

The only mechanical device used in deterring the spreading of spilt oil in water is oil fence that
normally consists of the float, skirt and ballast rope or chain. However, when the environment
condition such as current, wind and wave, exceeds certain limits, the oil fences become useless since
the oil would either leak beneath the fence or spill over the fence. Yet, there are some water zones that
definitely need to be protected from the oil contamination such as fishing farm area, cooling-water
intake area for a nuclear power plant, marine sports and recreational area, and marine ecologically
sensitive area. In these areas, the chemical dispersants are not favorable substances because of the
possible secondary pollution hazards. Short of any better conceivable devices for prevention of the
spilt-oil spreading, the idea of tandem fence has been proposed by Cornrack( 1983), Delvigne(l987),
Lo( 1996) and Lee et al.( 1998). A computational assessment method for tandem-fence effectiveness
was introduced by Lee et al.( 1998), which tracks the motion of oil patches around and between the two
fences. The variables considered in this method were current(or towing) speed, and fence separation
distance under the assumption of an identical draft for the two fences, deep water and flat free surface.
In the present investigation, the effects of the variation of the drafts of the two fences, the water depth
and the deformable free surface on the tandem-fence effectiveness are investigated.