Exam 1 Flashcards
Surface tension units
[F/L] or [M/T^2]
Surface tension force balance
weight = surface tension * length OR
density * area * gravity = surface tension (i.e. rod on surface)
Wetting liquid
(Hydrophilic surface) - theta is smaller than 90
Nonwetting liquid
(Hydrophobic surface) - theta is greater than 90
Contact angle for capillary tubes
Measured between the tangent line of the point where the meniscus meets the tube walls and the vertical walls of the tube
Contact angle for surfaces
Measured between the tangent line of the point where the droplet meets the surface and the surface inside the droplet
Young’s Law
σSG = σSL + σLG cos θ
Dynamic viscosity
- Resistance to deformation at a given rate
- stress / deformation rate
- stress / (dVx/dy), where dVx/dy is velocity gradient
- Can be measured with fluid between two plates (apply 1 force or 2 velocities) or using a Henke viscometer
- Constant for Newtonian fluids
Kinematic viscosity
dynamic viscosity / density
A diffusion constant for momentum
Dynamic viscosity units
[M/LT] or [FT/L^2]
Kinematic viscosity units
[L^2/T]
Continuity equation
Grounded in conservation of mass, applicable to all fluids
Shear-thinning fluids
Dynamic viscosity decreases with increasing strain rate (paint, blood)
Shear-thickening fluids
Dynamic viscosity increases with increasing strain rate (oobleck)
Sigma LG in Young’s
Surface tension (plain sigma)
Sigma LG in Young’s
Surface tension (plain sigma)
Density of water (standard conditions)
1 kg/L or 1 g/mL or 1000 kg/m^3
Viscosity of water (standard conditions)
1.12 x 10^-3 Ns/m^2
Contact angle of water (standard conditions)
0 degrees
Surface tension of water (standard conditions)
7.34 x 10^-2 N/m
