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Kinetics of Particles
Published in M Rashad Islam, A K M Monayem H Mazumder, Mahbub Ahmed, Engineering Dynamics, 2022
M Rashad Islam, A K M Monayem H Mazumder, Mahbub Ahmed
When a nail is struck by a hammer on a wall, the nail enters overcoming the resistance of the wall. The hammer can do this work because of its motion and the resulting kinetic energy, which allows the nail to overcome the resistance of the wall. You might have seen sailboats on the river. The kinetic energy of the current in the river drives the boat. When a strong wind blows, the boat moves faster if the sail is hoisted. As another example, an athlete would not jump from rest when competing in the high jump or long jump but would instead jump after running a certain distance. As a result, they can go a longer distance by using this kinetic energy. From this discussion, we observe that to stop a moving body by applying an external force, the total work done by the body before stopping is the measure of the kinetic energy of the body. In short, the energy possessed by a body by virtue of its motion is called kinetic energy. In other words, if a particle is at rest, a certain amount of work is required to be applied to it in order to produce a certain velocity. This work is also known as kinetic energy. The SI unit of kinetic energy is also J (N.m), and the US customary unit is lb.ft.
Airborne Wind Energy
Published in Vaughn Nelson, Innovative Wind Turbines, 2019
For models with the generator on the ground, the rising (reel-out) portion of the flight loop provides the power as there are no rotors. There can be small rotors for takeoff and landing for airframes even with the generator on the ground. Another idea is to have a rail track on the ground where the kite pulls a wagon (also referred as cart or bogie) with a generator connected to the wheels, namely a lift translator (see Chapter 6, section 4). Professor Wubbo OckelsOckels|Wubbo, Delft University of TechnologyDelft University of Technology envisioned wings on a ladder like a giant clothesline (LadderMill), which was essentially a lift translator with the upper end held aloft by a sail or balloon (http://www.energykitesystems.net/LadderMill/index.html). Wings on one side are positioned for maximum lift while the winds on the downside are positioned so that they bear their own weight. Later the single kite project at Delft University of Technology was called the LadderMillLadderMill project [4,5]. Note: A sailboat is a lift translator, which moves faster than the wind when it sails perpendicular to the wind and moves slower than the wind when it sails downwind (drag device).
Wind-assisted, electric, and pure wind propulsion – the path towards zero-emission RoRo ships
Published in Ships and Offshore Structures, 2023
Fabian Thies, Jonas W. Ringsberg
The ship concept’s main propulsion is wind energy, i.e. sail. This section presents the potential of wind propulsion for such a RoRo vessel and compares two sail technologies: Flettner rotors and fixed, symmetrical Wing sails. The lift and drag coefficients of both, the Wing sail and the Flettner rotor, depend on the trim of the sails. The trim parameters are the angle of attack for Wing sails and the spin ratio (i.e. the ratio of circumferential speed of the cylinder’s surface and inflow speed) for the Flettner rotor. To compare the two sail types, one must first compare the achievable (maximum) thrust coefficients as well as the thrust over side force at the same trim for each sail type while neglecting aerodynamic interaction effects, as presented in Figure 6.