If this is positive, the wave is propagating backwards (in the negative x direction)

If a wave is moving in one direction it is called a plane wave (dependent on only x & t OR y & t)

It is a function of space and time

Taken as the distance from the mean surface level to the seabed

There are other waves that occur internally in the ocean due to things like difference in salinity - but in this unit we are more interested in waves that propagate on the free surface

When you say it acts laterally, does this just mean that it is perpendicular to the flow direction but not necessarily up or down?

This explains why the drag oscillates at double the vortex shedding frequency - because it does not depend on if the vortices are moving clockwise (upper half) or anticlockwise (lower half)

It is a sort of "fin" that is attached to the cylinder in a helix shape which prevents the formation of vortices

When the cylinder starts to move, the flow "sees" a larger cross sectional area which increases the drag

Kinematic viscosity

If we are given a problem where Strouhal or reynolds number are not known - is it ok to assume St = 0.2?

Sometimes the viscous effect can be neglected, but it is very important when dealing with problems to do with boundary layers and flow separation

Added mass effect (more important in water than in air) - when you move in water you accelerate the surrounding fluid making it harder to move

This refers to the natural frequency of the object - in design it is important to design risers etc to have a natural frequency that is far from the vortex shedding frequency

Unit for both Fx and Fy are N/m because it is a two dimensional force

Ocean current and tidal currents are not the same due to wind, temperature difference, and salinity.

It is the most predictable as the positions of the sun, moon etc are known. The same cannot be said for waves & wind.

Gravity is inversely proportional to (distance)^2. But the tidal generating force is related to the difference in gravitational force (the derivative of the gravitational force) which is why the tidal generating force is inversely proportional to (distance)^3 instead of (distance)^2

These objects are typically slender structures / floating structures

For example 1, A is calculated as the surface area of the plane perpendicular to wind speed ( 5 x 5 = 25). But for example 2, A is calculated as the whole surface area of the cylinder (A = Dh), why?

Always use H0 = 10m and T0 = 1hr in calculations

It is a function of the speed of the fluid, the more turbulent the flow the larger the Reynolds number

Above water > wind Below water > current

Accidental load

Live load

Live load

Difference between wind wave & swell: - Wind waves are locally generated and have shorter wavelengths - Swells typically have longer wavelengths & travel beyond the location where they were generated

Characteristics of live loads: - Variable (not static) - Temporary

Characteristics of dead loads: - Static - Permanent - Constant with time

Couldn't some of these loads apply to onshore structures as well? making it not entirely unique? (other than wave/marine growth etc)