Buoyancy And Stability (week 3)
What we learnt
1.0 Buoyancy and stability
Today in class, we have learnt about the basics of buoyancy and stability. These two factors are very important when designing a prototype that floats on water as we will need to know the maximum weight of the load the prototype can support itself when it is floating on water. Such loads includes cargo, motors and other supporting structures to support the cargo when on water.
The image demonstrates how the buoyancy force works.
The calculation of buoyancy force,
Upward thrust on body = Upward force on lower surface - downward force on upper
surface
= total weight - weight of upper surface
Upward thrust on body = Weight of fluid displaced by the body.
2.0 Drag
We were also taught about drag in water, this is very similar to the module aeronautical engineering and fundamentals of flight.
However, we noticed that there is a difference between drag in the air and drag on/underwater. This is because liquids have higher viscosity compared to air, which adds to the drag.
There are several types of drag
Profile drag (pressure drag + Skin friction drag)
Form drag or Pressure drag
Skin Friction drag
Wave drag
Parasite drag
The picture below shows some shapes and their drag coefficient.
Different types of shapes have different drag coefficients, drag coefficient is the quantity to define resistance or drag of an object going through air or water.
More streamlined shape objects have lower drag coefficients compared to a shape such as square.
At the end of the lesson the teacher gave us a task that will be assessed for the next 3-4 weeks.
At the end of the lesson the lecturers gave us a task to build a surface vessel and there are various tasks that we have to carry out and complete by week 7.
More details about the activity can be found on page 12, click here to find out more.
Before we are able to carry on with our activity we were given some time to do requirement one.
Requirement one stated:
"Were there calculations to determine how much (aka. How much volume of) flotation elements are required to make the vessel float stably subject to the aforementioned requirements? TIP: you'll need a weighing scale (written or typed out calculations are required"
The calculations will be posted in another blog.
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