The Effects of Deadrise and Deadrise Variation on Steady Planing Hull Performance

Abstract

Historically, planing surfaces have been successfully used in a wide variety of practical applications ranging from flying boats of the 1930’s to the high-speed recreational, commercial, and military craft of the modern era. Planing hull analysis technology spans a similar time frame. The pioneering works of von Karman (1929) and Wagner (1932) were motivated by military interests in flying boats. Similarly, in the United States, Davidson Laboratories conducted and enormous amount of experimental research starting largely in the World War II time frame. One of the seminal publications related to planing hull performance prediction is Savitsky (1964), based upon research conducted at Davidson Laboratories. A major motivation for the Savitsky (1964) work, was to be able to provide the naval architect with a tool to assess steady planing performance in a meaningful way during the preliminary design process. Savitsky (1964) allowed the designer to study tradeoffs between variables such as deadrise angle, , chine beam, , planing surface length, longitudinal center of gravity, vessel weight, and shaft angle. As the 2010 Chesapeake Bay Powerboat Symposium is honoring the professional accomplishments of Dr. Daniel Savitsky, the work contained herein is motivated by the example set by Dr. Savitsky in successfully applying fundamental research findings to practical planing hull naval architecture problems. In the spirit of Savitsky (1964), the work of Savander (1997) and Savander, et al., (2002) was motivated by the need to provide the planing hull designer with a tool to assess steady planing performance that allowed for sufficient geometric sensitivity in a computationally efficient manner. These methods are based upon application of a slender body theory approach in conjunction with an ideal flow theory formulation. Savander, et al. (2002) revealed explicit definition of general deadrise variation, B (x,z), in the formulation for dynamic lift and drag, where the horizontal plane is defined by (x,z). The formulation presented in Savander, et al. (2002) is implemented in a numerical program identified as SEAdyn. SEAdyn is used herein to analyze the calm water resistance characteristics of a series of geometrically related planing surfaces created by systematic variation of deadrise, B (x,z), as may be used by the naval architect in the planing hull design process. The baseline hull configuration corresponds to the 70-ft planing hull (JB70) presented in Savander, et al. (2008) which was extensively tested at model scale by MARIN, and at full scale by MTU - Detroit Diesel. The performance of the hullform variants is presented and compared to model test results obtained by MARIN for the JB70. The hullform that which displayed the most favorable resistance improvement is be analyzed, as part of an ongoing effort, with the RANS solvers STAR-CCM+ and OPENFOAM. The results from model tests, SEAdyn, STAR-CCM+, and OPENFOAM are all be presented and the merits of each analysis approach discussed.