INTRODUCTION 
The Navy is faced with very strict regulations covering the 
discharge of oily wastes from its ships and shore facilities. Such 
wastes primarily originate from ship’s bilges and ballast waters, 
oil spill recovery operations, fuel storage and transfer systems, 
and garage and maintenance activities. Technology and hardware 
are being developed to process such wastes so that effluent will 
meet EPA requirements. 
Current methods of separating oil from oil-water mixtures 
are centrifugation, gravitation, coalescence and ultrafiltration 
[1,2]. Centrifugation is an accepted method for separating water- 
oil dispersions or emulsions [2]. Commercial equipment is available 
for a wide range of applications. Despite their effectiveness, 
the power requirement, cost and maintenance of such systems 
is relatively high. The gravitation method of separating oil 
from oily wastes relies upon differences in densities of the 
fluids being separated. Commercially available API and Heil 
type parallel separators are based upon the gravitation principle. 
Because of the laminar flow requirements for separation such 
systems are normally bulky. Coalescence has been used quite 
extensively for removing finely dispersed water droplets from 
fuels. The basic mechanism behind this separation technique 
is the formation of larger oil drops on the coalescing material. 
The resulting larger drops are separated by gravity. The method, 
however suffers from fouling of the coalescing element and 
requires frequent maintenance. Finally, ultrafiltration uses 
a filtering process to separate water from oil. This method, 
although very effective, suffers from fouling of the filter 
element. The system requires frequent cleaning. 
A new method of separating free oil from oil-water mixtures 
[3] is under investigation at the Naval Civil Engineering Laboratory * 
(NCEL). This technique uses the fluid dynamic phenomenon, called 
“wall attachment, or Coanda effect’’, named after its discoverer, 
Henry Coanda. This effect is seen, for example, when one’s 
finger is held close to a thin stream of water issuing from 
a tap or when tea is poured from a badly designed teapot-spout. 
A preliminary investigation was conducted to establish 
the feasibility of using the Coanda effect for separating two 
immiscible liquids. This report describes in detail the feasibility 
program. 
*On 1 January 1974 redesignated the Civil Engineering Laboratory (CEL) of the Naval Construction Battalion 
Center, Port Hueneme, California. 
