Marine Vehicles
From Thermal-FluidsPedia
As ships and other marine vehicles move through water, they experience both water and air resistances. The resistance through water is the greater of the two and depends on many factors including ship speed, hull form, and water temperature. The total hull resistance consists of several components:
a. Skin friction drag due to friction between the hull and water
b. Form drag due to pressure forces acting on the hull
c. Wave drag due to energy lost in creating and maintaining the ship’s characteristic bow and stern waves
d. Wind resistances
Frictional losses are the function of the hull’s wetted surface area, surface roughness, and viscosity. At low speeds, viscous resistance is dominant and can account for up to 50-80% of total resistance. As speed increases, the wave-making resistance increases rapidly and eventually dominates all other resistances. Air drag can also play a role and may contribute between 4 to 10% to total ship resistance, depending on speed, the shape of the ship above the waterline, and the area of the ship exposed to the air. Wind and current resistances can be significant in rough waters and when a ship runs into strong headwinds.
The resistance is not proportional to velocity, but increases as the square of velocity at low speeds and more rapidly as velocity to the fifth power at higher speeds (Figure 1). The power required to propel a ship through water is the product of total hull resistance and ship speed (P = F.V). Therefore, the power required can be proportional up to ship speed raised to the 6th power! The fuel consumption rate also increases accordingly; it takes much more fuel to travel a given distance at a faster speed than traveling the same distance at a slower speed.
References
(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005
Further Reading
Tillman, D., Fuels of Opportunity: Characteristics and Uses In Combustion Systems, Academic Press, 2004.
Sorensen, K., Hydrogen and Fuel Cells: Emerging Technologies and Applications, Academic Press, 2005.
Dhameia, S., Electric Vehicle Battery Systems, Academic Press, 2001.
Hussain, I., Electric and Hybrid Vehicles: Design Fundamentals, CRC Press, LLC. 2003.
Jefferson, C.M., and Barnard, R. H., Hybrid Vehicle Propulsion, WIT Press, 2002.
Spelberg, D. The Hydrogen Energy Transition: Moving Toward the Post Petroleum Age in Transportation, Academic Press, 2004.
Fuel, Direct Science Elsevier Publishing Company, Fuel focuses on primary research work in the science and technology of fuel and energy fuel science.
Transportation Research Part C: Emerging Technologies, Direct Science Elsevier Publishing Company; this journal focuses on scholarly research on development, application, and implications in the fields of transportation, control systems, and telecommunications, among others.
Fuel Cells Bulletin, Direct Science Elsevier Publishing Company, Fuel Cells Bulletin is the leading source of technical and business news for the fuel cells sector.
International Journal of Hydrogen Energy, Direct Science Elsevier Publishing Company, Quarterly journal covering various aspects of hydrogen energy, including production, storage, transmission, and utilization, as well as economical and environmental aspects.
External Links
US Department of Transportation (http://www.dot.gov).
US Department of Energy (http://www.doe.gov).
US Environmental Protection Agency (http://www.epa.gov).
National Energy Renewable Laboratory Fuel Cell, Hybrid Electric, and Plug-In Hybrid Vehicles (http://www.nrel.gov/learning/avf_advanced_vehicles.html).
FreedomCar (http://www.eere.energy.gov/vehiclesandfuels).