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Utilizing process automation and intelligent design space exploration for simulation driven ship design
Published in Pentti Kujala, Liangliang Lu, Marine Design XIII, 2018
E.A. Arens, G. Amine-Eddine, C. Abbott, G. Bastide, T.-H. Stachowski
From Figure 18 it can be seen that to design for a low CAPEX, a short (small Lpp) bulky vessel is better whereas to design for low OPEX, a long (large Lpp) streamlined vessel is better. This can also be seen in Figures 19 and 20 (respectively the low CAPEX design and low OPEX design as highlighted in Figure 17). Both designs, although being narrow, satisfy the criterion for deck space by having a long after body and by having an optimized bow shape for a low pressure resistance and thus low OPEX. The design in Figure 19 is clearly short, minimizing the steel weight and thus the CAPEX. To keep sufficient displacement the draft is larger, increasing the frontal area of the submerged hull which increases the pressure drag. The design in Figure 20 is much longer, increasing the CAPEX, but with a small draft the transom is out of the water and the pressure drag is reduced significantly. The wetted area is slightly larger which increases the resistance drag due to friction, but this increase is small compared to the reduction in pressure drag.
Drag force and drag coefficient
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
Wetted area is the actual surface area of the material making up the skin of the airplane; it is the total surface area that is in actual contact with, that is, wetted by, air in which the body is immersed. Indeed, the wetted surface area is the surface on which the pressure and shear stress distributions act; hence, it is a meaningful geometric quantity when one is discussing aerodynamic force. However, the wetted surface area is not easily calculated, especially for complex body shapes.
A conceptual design of a solar powered UAV and assessment for continental climate flight conditions
Published in International Journal of Green Energy, 2022
Irem Turk, Emre Ozbek, Selcuk Ekici, T. Hikmet Karakoc
The two important reasons for redesign are: The high-volume requirement of PEMFC UAV fuselage required in the Hydra for allocation of the fuel cell stack and a 2 L hydrogen tank. The fuselage geometry was iterated into a slenderer type with less form drag and a less wetted area. Therefore, the total aircraft drag coefficient was decreased.An air inlet on the fuselage that was designed for taking the required air mass for the chemical reaction in the fuel cell stack. Air inlets are a great source of drag force for aircraft even when designed carefully. Eliminating the air inlet decreased the total aircraft drag coefficient.
Experimental measurement of the nearfield longitudinal wake profiles of a high-speed prismatic planing hull
Published in Ship Technology Research, 2021
Angus Gray-Stephens, Tahsin Tezdogan, Sandy Day
When a stepped hull is employed, any method of performance prediction must calculate the forces and moments acting on each section of the hull, before summing them to solve for the global forces and moments that establish the total resistance, lift and the equilibrium position of the hull. To determine the forces acting upon each of the lifting surfaces, both the wetted area and the relative deadrise angle between the fluid surface and the hull must be known. In order to calculate these, it is vital to be able to accurately model the wake pattern associated with the forebody flow so that how it intersects with the afterbody may be determined. Errors introduced through the incorrect modelling of this wake pattern may result in large differences in the wetted area and relative deadrise, leading to the incorrect calculation of forces and moments acting upon each surface. While the calculation of resistance is negatively affected, it is the calculation of the hulls equilibrium position that suffers the greatest accuracy loss when this happens. This is due to the incorrect distribution of forces and moments arising from the incorrect wetted area and relative deadrise calculations.
Rapid resistance estimation method of non-Wigley trimarans
Published in Ships and Offshore Structures, 2019
Lin Du, Hamid Hefazi, Prasanta Sahoo
The viscous resistance coefficient is the product of form factor and frictional resistance coefficient as shown in the following equation:where (1 + k) is the form factor which can be determined by the method proposed by Prohaska (1966). The frictional component of trimarans can be expressed in terms of their respective wetted surface area as shown in the following equation:where is the total wetted area () and and are the main-hull and side-hulls’ wetted surface area respectively as Equation (9) illustrated.