Offshore & Subsea Structures

LNB 40702ASSIGNMNET 1

Lecturer: MR. Mazlan Bin Muslim

Prepared By :Kogulan MuruganAnand Raj Rajah

Mohd Zakuan Firdaus bin Muhammad

INTRODUCTION- WAVE ENERGY

Waves are a ridge or swell moving through or along the surface of a large body of water.

Wave energy means, the energy obtained by harnessing wave power, which can be divided into three types of progressive wave which is Longitudinal Wave, Transverse Wave and Orbital Wave.

WAVE CHARACTERISTIC

Most ocean waves are produced by wind, as the wind blows over the ocean surface, it creates pressure and stress. This energy from pressure and stress is carried by the waves towards the shore.

The physical changes as the wave approach shore can be divided into three transformation process which is Breaking, Reflection and Refraction. These processes are taken place between the transitions of deep-water wave into shallow water wave.

PROGRESSIVE WAVES

• Waves transmit energy by means of cyclic movement through matter. The medium itself whether solid, liquid, or gas does not actually travel in the direction of the energy that is passing through it.• Waves move in different ways. Simple progressive waves are waves

that oscillate uniformly and progress or travel without breaking.

Progressive wave divided into 3 broad classes :

1) Longitudinal – a good example are sound waves2) Transverse – energy moves at right angles to the wave. 3) Orbital (interface waves) - these occur at the interface of two materials with different densities (e.g. air and water)

LONGITUDINAL WAVES• In a longitudinal wave, particles of the medium are displaced in a

direction parallel to energy transport. The shape of the wave called as waveform moves through the medium by compressing and decompressing as it goes. Sound, for instance, travels as longitudinal waves.• Energy can be transmitted through all states of matter gaseous, liquid,

or solid by this longitudinal movement of particles.

TRANSVERSE WAVES

• In transverse waves (also known as side-to-side waves), energy travels at right angles to the direction of the vibrating particles.• Transverse waves transmit energy only through solids, because the

particles in solids are bound to one another strongly enough to transmit this kind of motion.

ORBITAL WAVES

• As the wave travels, the water passes the energy along by moving in a circle. This movement is called circular orbital motion.• Waves travel because gravity pulls the water in the crests downward.

Forced out from beneath the falling crests, the falling water pushes the former troughs upward, and the wave moves to a new position, as indicated.

THE POSSESSES OF WAVE CHARACTERISTICDEEP-WATER WAVE

• if water depth (d) is greater than the wave base (L/2), the waves are called deep-water waves. Deep-water waves have no interference with the ocean bottom, so they include all wind-generated waves in the open ocean, where water depths far exceed wave base.

Wave speed (S) is the rate at which a wave travels. Numerically, it is the distance traveled divided by the travel time; for a wave, it can be calculated as:

According to the equations that govern the movement of progressive waves, the speed of deep-water waves is dependent upon:

WavelengthSeveral other variables such as gravitational attraction that remains constant on Earth.

Altogether, the general relationship for Deep-Water Wave is the longer the wavelength, the faster the wave travels. A fast wave does not necessarily have a large wave height, however, because wave speed depends only on wavelength.