3.2 LIFE IN THE HIGH RE WORLD

Question 1

What is the key to propulsion in the inertial high Re world?

Answer 1

Be streamlined (less chance of flow separation)

Question 2

Angle of airfoil (angle of attack)

Answer 2

Higher angle = faster you’ll be able to climb/higher velocity

Question 3

How to prevent stall in airfoils

Answer 3

• use eddy flaps to stop propagation of flow separation up surface

Question 4

How do leading edge tubercules help humpback whales?

Answer 4

• lift sustained at higher angles of attack
• lower drag coefficient with tubercules at angles of attack higher than 11 degrees
• generate vortices that delay separation thus preventing stall

Question 5

How do scallops avoid predators?

Answer 5

• Propelled by jets as shell is clamped shut reaching 0.5m/s

- Riblets optimised to prevent formation of hairpin vortices; keep vortices channelled streamwise

Question 6

Fish and vortices

Answer 6

• Fish tails function as an independent propellor

- Not as passive extension to body

Question 7

Can marine organisms influence the Re world?

Answer 7

Exopolymer substances EPS exuded in plankton blooms increase seawater viscosity

• copepod predators avoid high viscosity zones
• may be so viscous that flow in fish gills retarded/stopped - get fish kills
• such events becoming more common with eutrophication and warming