Week 8 - Types of Drag Flashcards
3 types of Drag
Wave drag, Surface drag, Profile drag
Define wave drag
Resistance created by the generation of waves at the interface between two different fluids
What increases wave drag
Vertical movements of swimmer, velocity of swimmer
Fine surface drag
Resistance derived from friction between adjacent layers of fluid near a body moving through fluid
What increases surface drag
Fluid viscosity, surface roughness
Define profile drag
Resistance created by pressure differential between the lead and rear sides of a body moving through fluid
What increases profile drag
When the body in the water is not streamline, this causes the boundary layer of water to become partially turbulent when it separates causing a difference in pressure from the front to the rear of the swimmer
What is drafting in cycling?
Traveling close behind another moving object, sitting in the low pressure wake made by the front cyclist, which requires less energy.
What are the 3 types of flow
Type I flow: Laminar
Type II flow: Partially turbulent
Type III flow: Fully turbulent boundary layer
What happens to profile drag and surface drag when a ball is traveling slowly?
As it is a laminar flow there will be less profile drag, but increased surface drag as there is friction between the adjacent fluid layers
What happens to profile drag when a ball is traveling at high velocities
Profile drag is increased causing turbulent flow at the rear of the ball and creating a lower pressure behind the ball resulting in drag as the air is sucked from the high to low pressure.
What happens to profile drag at extremely high velocities?
Reduced surface drag as the air flowing passed the ball is fully turbulent, meaning the layers of fluid aren’t so close to each other causing less friction.
What ball design simulates Type III flow?
Golf balls are made with dimples to encourage turbulent flow around the ball, minimising the low pressure behind the ball and surface drag of the air flow.
