NIS Mich oct05

Recent Advances in the Naval Architecture for NIS Control: 

Recent Advances in the Naval Architecture for NIS Control Prof. Michael G. Parsons Naval Architecture and Marine Engineering University of Michigan

New IMO Requirements: 

New IMO Requirements A 95% volumetric ballast exchange (@ 200nm, 200 m). Effectiveness is still being debated, however. Flow-through exchange for three volumes “shall be considered” to meet the requirements All ships shall remove and dispose of sediments in ballast spaces Management standard for non-exchange: less than 10 viable organisms/m3 above 50 µm and 10 between 50 and 10 µm Indicator microbes: E. coli, Vibrio cholerae, intestinal Enterococci re: International Convention for the Control and Management of Ships’ Ballast Water and Sediments, IMO, Feb. 13, 2004

Idealized Models of Flow-Through Exchange: 

Idealized Models of Flow-Through Exchange No mixing of the new and old ballast water (so-called plug flow); then one tank volume of flow yields 100% replacement Perfect mixing of the new and old ballast water at all times - then the concentration of old water is given by C(t) = Ci e – t/t where t = residence time = tank volume/inlet flow rate after three volumes (t = 3t), the exchange is 95% this is the basis for current rules confirmed by MV Iron Whyalla tests (rectangular tanks)

Impact of Ballast Tank CFD Research: 

Impact of Ballast Tank CFD Research This research has shown that CFD can be used to analyze exchange effectiveness and help design better ballast tanks. This research has shown that the new IMO rules are flawed and will not necessarily provide the protection assumed. This research has demonstrated that the bulk carrier hooper side/wing tank configuration previously recommended in the ship design literature is actually the worst possible choice. re: Kent, C. P, and Parsons, M. G., “Computational Fluid Dynamics Study of the Effectiveness of Flow-Through Ballast Exchange,” Transactions of SNAME, Vol. 112, 2004. summary to appear in IMO Globallast’s Ballast Water News – future issue circulation to 12,000 policy, biology, and engineering NIS specialists world-wide

The “Ballast-Free” Ship : 

The “Ballast-Free” Ship Period 2002-2004 (nearing end) Development of a new concept of ship design to essentially eliminate the potential for NIS introductions through the ballast water vector Investigation of related design and technical research issues associated with this concept

The Ballast-Free Ship Concept: 

The Ballast-Free Ship Concept Its origin was in National Research Council’s Ships’ Ballast Water Operations Committee deliberations : Question from biologists/ecologists in the: “Why not just eliminate the use of water ballast?” Response: “Water ballast is necessary in the light cargo condition to ensure: Transverse stability Bow submergence Propeller submergence Reduce windage for adequate maneuverability, …”

The Ballast-Free Ship Concept (cont.): 

The Ballast-Free Ship Concept (cont.) Traditional approach: Add water ballast to increase vessel weight in the light cargo condition Paradigm shift: instead of thinking add weight, reduce buoyancy Ballast-Free Ship concept principles: Replace traditional ballast tanks by longitudinal, structural ballast trunks that extend beneath the cargo region below the ballast waterline. Connect these trunks to the sea through a plena at the bow and the stern. Flood trunks in the ballast condition. Pump out when finished. The natural hydrodynamic pressure differential between the bow and the stern region induces a slow flow in the ballast trunks. Thus, the trunks are always filled with “local seawater”. US Patent #6694908, 2004

The Ballast-Free Ship Concept (cont.): 

The Ballast-Free Ship Concept (cont.) Concept advantages: Eliminates the need for costly ballast water treatment equipment. Effective approach even for transport of biota smaller than 50 microns; e.g. Vibrio cholerae Concept development requirements: the project research Prove feasibility of concept (CFD studies of available pressure differential, trunk flow development, effect of waves). Investigate resistance and propulsion impacts (model tests). Re-design the internal structure to implement the concept and ensure structural strength adequacy. Assess intact stability, probabilistic damage stability and seakeeping performance. Evaluate economic feasibility.

Summary of Economic ComparisonChange in Required Freight Rate compared to filtration and UV treatment: 

Summary of Economic Comparison Change in Required Freight Rate compared to filtration and UV treatment Ballast-free ship with 7.5% power penalty found in our tank testing and a larger engine + $0.133/t of cargo Ballast-free ship with 7.5% power penalty and same engine - $0.023/t, a small savings Ballast-Free Ship without any power penalty - $0.204/t, significant Ballast-Free Ship compared to flow-through exchange +0.165/t

Impact of Ballast-Free Concept Research: 

Impact of Ballast-Free Concept Research This research has shown that: The Ballast-Free Ship concept essentially eliminates the transport of foreign ballast water. It provides a viable alternative to ballast water treatment systems and ballast exchange; and should be equally effective even with stricter future requirements. Hydrodynamic optimization should eliminate most of the added power penalty. Our pending future research. This should be a cost effective alternative (DRFR < 0) to filtration/UV re: Kotinis, M, Parsons, M. G., Lamb, T., and Sirviente, A. “Development and Investigation of the Ballast-Free Ship Concept,” Transactions of SNAME, Vol. 112, 2004. summary to appear in IMO Globallast’s Ballast Water News - next issue