FOURTEENTH INTERNATIONAL CONFERENCE ON MARINE SCIENCES AND TECHNOLOGIES 89 ON THE FOREBODY SHAPE EFFECT ON SHIP RESISTANCE IN STILL WATER AND SEAWAY Ihor P. DAVYDOV*, Andriy V. PECHENYUK** * – Marine Engineering Bureau (Odessa, Ukraine), National University “Odessa Maritime Academy” (Odessa, Ukraine), As. Prof., Dr, senior researcher, head of vessel's theory and design department of University ** – National University “Odessa Maritime Academy”, (Odessa, Ukraine), PhD Abstract. In recent years CFD technologies are actively used for the practice in the design and optimization of the ship hull form. The suggested method of in-detail hull form design uses CFD for hull resistance determination. The obtained results can be presented as the optimum distribution of the required hull volume and, eventually, the optimized shape of hull surface. The method was applied to forebody of the well-known KCS hull form and showed interesting characteristics. This paper describes farther development of the method as well as diversified analysis of its reliability and practical feasibility. It is shown that precision can be noticeably improved, however correctness strongly depends on CFD model and computational grid. At last, it has been taken into account that the optimization process manages hull resistance in still water only. Therefore the overall design assessment of the optimized forebody shape is supported by estimation of resistance in seaway. Keywords: computational fluid dynamics, hull form design, hull form optimization, ship resistance in seaway. INITIAL PROBLEM Hull form optimization is a well-known problem of ship design, which is hackneyed and topical at the same time. In practice, lines design is still to some extent an art. There is no accepted formalized method, which allows designing a hull form with guaranteed minimum resistance, not to mention highest propulsion qualities. Although a great amount of experimental and theoretical researches have been carried out in that field, and perfect hull forms were designed in particular cases, their optimality in strict sense remained questionable. A special research direction was established for developing scientifically grounded way of hull form design. Seemingly first attempts to arrange an optimization process for hull form were made on the base of Mitchell's formula for wave resistance [1, 2]. Statistical analysis of experimental results [3] and developing original methods based on CFD [4] are examples of present-day approach. The represented method of optimum foreship transformation (MOFT) may be considered as some combination of several approaches, which complement each other. The MOFT showed interesting characteristics [5, 6] and it's now being developed further. AIM OF THE PAPER Grounding of efficiency of results received with usage of MOFT. The MOFT manages hull resistance in still water only. Nonetheless, effect of modified forebody shape on resistance increase in seaway can be additionally estimated. The corresponding results are also included. MAIN TEXT MOFT conception MOFT conception implies a reasonable compromise between mathematically strict optimization process and practically available methods of hull geometry variation and resistance evaluation. Principal dimensions of the ship, including displacement volume, are considered constant, as well as the side contour of the hull. It corresponds to intention of isolating shape effect from more intense effect of principal dimensions. Well-known specific resistance  R remains the main criteria of hull form efficiency, though it is now applied to separate regions of hull surface. If we considered some individual region of hull surface and altered it with causing some hull volume increment   , but without changing the rest surface, the volume increment   can be corresponded then to appropriate resistance increment R  . When there was more than one alteration of each surface region, resistance increments can be expressed versus volume increments as continuous functions. These functions can be set up for several selected surface regions and used for searching the combination of volume increment values, which meets two conditions: (1) min    R ; (2) 0     .