Sed Strat Lab Final Rev

Question 1

Hjulstrom Diagram Assumptions

Answer 1

-spherical quartz
-1 m depth of water
-flow over a smooth bed
-freshwater

Question 2

Why are higher velocities required to move fine-grained material?

Answer 2

due to cohesion

Question 3

what is the x axis on the Shields diagram

Answer 3

grain reynolds number (r=(U*D)/v)

Question 4

what is the y-axis on the shields diagram

Answer 4

critical shear stress

Question 5

boundary shear stress

Answer 5

t = p hS g
p=density of fluid
h=water depth
S= slope
g= gravity

Useful conversions:
1g/cms^2 = 0.1 Pa
1g/cm^3 = 1000 kg/m^3
*If you use cm in your other units (how they are given to you here), make sure you use g = 980 cm/s^2

Given values:
Density of quartz: p = 1 g/cm^3
Density of water: p = 2.65 g/cm^3
Kinematic viscosity of water: 1*10^-6 m^2/s

Question 6

reynolds number

Answer 6

Re= (ULp/u) = (UL/v)
Re> 2000 turbulent flow
Predicts laminar vs. turbulent

Question 7

Stokes Law

Answer 7

V = (Ps-Pf) g D^2
____________
18 u
Expresses the settling velocity of a spherical particle in a fluid medium
Ps = density of particle
Pf = density of the fluid
g = gravity
D = particle diameter
u = dynamic viscosity

Question 8

Froude Number

Answer 8

F=U/(gL)^0.5
dimensionless #
>1 Rapid
<1 Tranquil
Determines which bedforms will form