3.5 FLUID-SED INTERACTION II- BOUNDARY LAYERS, BEDFORMS & SHARKS

Question 1

What is a buffer layer?

Answer 1

Aka turbulence generation layer

A zone of intense interaction between turbulent and viscous forces

Question 2

Burst and sweep events

Answer 2

High instantaneous velocity profile = sweep event

Low instantaneous velocity profile = burst event

Question 3

What do riblets do?

Answer 3

Decrease cross-flow width of vortices - reduce drag

They may also act as VORTEX GENERATORS - keep flow attached and reduce pressure drag

Question 4

What are some examples of artificial riblets?

Answer 4

Speedo swimsuits

Aircraft coatings

Question 5

Describe the sequence of events leading to ripple formation.

Answer 5

1) Sweep of high velocity turbulent fluid suspends grains
2) Grains settle to form pile
3) Flow separation occurs causing further erosion
4) Ripples form along bed

Question 6

What are ripples’ existence limited by?

Answer 6

The presence of laminar/viscous sublayer