View non-flash version
18 MARITIME REPORTER & ENGINEERING NEWS ? FEBRUARY 2013 Computational fluid dynam-ics (CFD) denotes collec-tively techniques for solv-ing equations describing the physics of fluid flow. CFD is by now widely known and accepted in the maritime industry, but mostly as- sociated with flows around the hull and propellers, for example in the context of designing more fuel-effi- cient ships. However, CFD is in many ways far more versatile than classical model testing. The same software can be applied to a variety of flows, including also in-ternal flow problems. A key advantage of CFD is the insight into flow details. As flow quantities are computed (and stored) at many discrete locations in space (computa-tional cells) and for many time steps, it is easy in post-processing to look at arbitrary cross-sections and zoom in and out at will. Ballast water management systems have moved into the spotlight for ship operators with recent IMO regulations which drive the transition towards ballast water management to curb the spread of invasive species. But apart from the particularities of the new regulations, ballast water handling may pose challenges for ship opera-tors where the advantages of CFD simulations come into play. The fol- lowing case studies illustrate prob-lems and solutions taken from indus-try experience. CASE STUDY 1: TYPE APPROVAL BASED ON CFD The ballast water of ships carries plants and animals which frequently settle in foreign sea regions, repre-senting a danger for the indigenous aquatic environment, potentially caus-ing great ecological, health-related and economic damage. The growing ship traffic has increased this threat considerably. The IMO ?International Convention for the Control and Man-agement of Ships? Ballast Water and Sediments? requires a ballast water management plan. Starting from the year 2016, all ships will have to base their ballast water management on ballast water treatment. If this treatment is based on chemi-cal approaches, rapid and effective mixing of the chemical component with the ballast water is vital to achieve a homogeneous concentra-tion of the biocide. For type approval of new systems, simulations can be a valuable tool. In one case, Future-Ship simulated the mixing of chlorine and ballast water in pipes during the ballasting operation. The CFD simu- lations were used to determine the required pipe length of the mixing zone to ensure homogeneous mixing. Simulations showed that the mixing in the initial design was inefficient. Very simple and cost effective modifi- cations of the inlet geometry served to increase the turbulence level signifi-cantly with a resulting much shorter TECHNICAL FEATURE SIMULATION & BALLAST WATER TREATMENT Advanced Simulation Helps to SolveBallast Water Management Problems Figure 1: CFD simulates mixing of two fluids in a pipe for type approval.Ballast water management poses problems in design and operation of ships. Computational fluid dynamics (CFD) offers solutions with design, type approval and trouble-shooting. By Tobias Zorn, Jan Kaufmann, FutureShip & Milovan Peric, CD-adapco MR #2 (18-25).indd 18MR #2 (18-25).indd 182/1/2013 9:46:03 AM2/1/2013 9:46:03 AM
