hydrodynamics

Question 1

reynolds number

Answer 1

Re = uL/v
u = flow speed (m/s)
L = characteristic linear dimension (m)
v = kinematic viscosity (m^2/s)

Helps describe how fluid flows
inertial vs viscous effects

Question 2

at low reynolds number

Answer 2

flow is laminar (sheet-like)
inertia provides little usefulness
you can move by way of like a flexible oar or corkscrew
- you can’t have the same path like a stiff oar
-Purcell’s life at low reynolds number

Question 3

high reynolds number

Answer 3

flow becomes turbulent (i.e. chaotic changes in flow velocity and pressure)

Question 4

Bernoulli’s equation

Answer 4

increase in speed causes a decrease in pressure or potential energy

v^2/2+gz+p/rho = const.

v = fluid flow
z = elevation
p = pressure
rho = density

For incompressible fluid -different eq for compressible fluid

Question 5

viscosity

Answer 5

resistance of fluid to deformation - not to be confused with elasticity in solids