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Ocean Waves and Wind Forces
Published in Srinivasan Chandrasekaran, Faisal Khan, Rouzbeh Abbassi, Wave Energy Devices, 2022
Srinivasan Chandrasekaran, Faisal Khan, Rouzbeh Abbassi
Environmental loads continuously interact with offshore structures in waves, wind, current, or seaquakes. Continuous exposure to these loads can also induce fatigue damage to the structure over time as these loads are also cyclic. Among all these loads, a primary concern is wave and wind loads; the former is a high-frequency phenomenon compared to the latter. The basic concept of floating offshore structures should therefore be FORM-dominant; resistance to load should be incurred from the geometric shape and not by the strength of the material. For a broader convenience of commissioning and de-commissioning, large floating structures are designed as positively buoyant. Excessive buoyancy keeps them afloat, enabling easy installation, but poses serious challenges to their structural response.
Petroleum Migration and Accumulation
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Buoyancy is the upward force exerted by fluid. It is a natural property of a liquid. An object floats at the surface of water because of the upward buoyancy force. The upward pressure of the fluid is enhanced by the difference of specific gravities of gas/oil/water in fluid-saturated pores. The specific gravities of gases are between 0.1 and 0.55, of oil between 0.55 and 0.99 and for water the range is 1.0–1.25. The specific gravity of water depends on salinity (salt content). The higher the gravity differences, the higher the buoyancy pressure. A gas/water system has a higher buoyant rise than an oil/water system. The buoyant pressure continues to work until a less permeable trap rock is encountered. Upward buoyant pressure is balanced by trap rock, where pores’ hydrostatic pressure prevents the further rise of the fluid. Thus a reservoir is created. The underground pore water may be mobile or immobile. Mobile hydrodynamic pressure enhances the buoyancy, whereas immobile hydrostatic pressure retards this buoyancy pressure.
Fluid statics
Published in Amithirigala Widhanelage Jayawardena, Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers, 2021
Amithirigala Widhanelage Jayawardena
Buoyancy is the force (only vertical) acting on a body floating on a liquid surface due to liquid pressure. There is no horizontal thrust since pressures are equal at the same horizontal level. It is due to the pressure difference between the upper and lower surfaces of the body. It acts upwards in the vertical direction because the pressure at the lower surface is always higher than that at the upper surface. For a static fluid, p=hρg⇒dpdh=ρg⇒p=p0+ρgh
Criterion of vehicle instability in floodwaters: past, present and future
Published in International Journal of River Basin Management, 2021
Syed Muzzamil Hussain Shah, Zahiraniza Mustaffa, Eduardo Martinez-Gomariz, Do Kyun Kim, Khamaruzaman Wan Yusof
When a body is submerged in fluid, the resultant force acting on the body is formed in an upward vertical direction. This force, which is also known as the buoyancy force, is generated because of the pressure which increases with depth. These pressure forces acting from below are larger than the pressure forces acting from above. Therefore, the buoyancy force has a magnitude equal to the weight of the fluid displaced by the body and is directed vertically upward. This phenomenon is commonly referred to as Archimedes’ principle (Young et al. 2010). The buoyancy force is an upward force exerted by a fluid that opposes the weight of the immersed object. Therefore, when the buoyancy force , is greater than the vehicle weight, the vehicle starts to float and is carried away by the flow. This force can be expressed aswhere is the density of water, is the acceleration due to gravity and is the submerged volume of the vehicle (Shu et al. 2011).
Resistance characteristics of innovative eco-fitness equipment: a water buoyancy muscular machine
Published in Sports Biomechanics, 2018
Wei-Han Chen, Ya-Chen Liu, Hsing-Hao Tai, Chiang Liu
The resistance of WBM machine was generated by buoyancy and drag. Buoyancy refers to the vertical force resulting from the pressure difference between the upper and lower surfaces of an object, and the buoyant force acting on an immersed object is equal to the weight of the fluid displaced by the object. Fluid resistance is the force exerted by the fluid on an object moving through the fluid. A float was placed in a cylindrical water tank to produce resistance; resistance was generated by buoyancy and fluid resistance when the float was pulled downward. A cable attached to the float bottom can be pulled from outside the machine using pulleys; this cable can be used to pull the float down. Figure 1 illustrates the mechanics of the WBM machine. A user can hold the handle on the machine top (Figure 2) to perform exercises such as a straight arm pull down or triceps extension. In addition to the pull down and triceps extension, the WBM machine is versatile and can strengthen numerous muscle groups in the upper and lower extremities, similar to a cable or multi-function system.
Multi-Phase Permanent Magnet Generator with Halbach Array for Direct Driven Wind Turbine: A Hybrid Technique
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Janarthanan Balakrishnan, Chinnathambi Govindaraju
The detailed explanation of proposed approach named AOA and RBFNN is clarified in this section. Here, AOA deals the optimization issues. AOA is derived from Archimedes principles. It follows the principle of buoyant force and it exerts the upward object and fully or practically immerses the fluid and it is propositional to the weight of displaced fluid (Liu et al. 2013). Most commonly used artificial neural network is the Radial basis function (RBF) networks, which are used to solve the function approximation problems. The main advantage of RBFNN is faster learning speed and universal approximation (Hashim et al. 2021).