Fluid Principles Flashcards
(9 cards)
What are the two categories of solids states of matter
Elastic- where they recover their shape
Plastic where they deform permanently after passing a certain stress
What is newtons law of viscosity for a Newtonian fluid and explain
Newtons law of viscosity: tau= mew x du/dy
This essentially means that the shear stress (tau) is proportional to the rate at which the speed decreases in a liquid where a boundary plate is moving.
And the constant of proportionality is the viscosity of the liquid-mew.
What is the law of viscosity for a non Newtonian fluid
tau= a + b(du/dy)^n
What is specific weight and explain it
Specific weight is the density x the gravity
Specific weight measures the force exerted by gravity on a unit volume of a fluid
It is used as in hydrology mass or weight is not used as much as it is not as useful due to the constant changing nature of a river.
What is specific gravity (SG)
SG = specific weight of 1st liquid over specific weight of 2nd liquid
or density of first over density of second
as the gravitational acceleration is the same
What is the definition of buoyancy
Buoyancy is the upward force exerted by a fluid that opposes the weight of a partially or fully immersed object
What is Archimedes law and equation
m(f) x g = rho x g x V(f)
This means that the mass of the object in a fluid multiplied by gravity (the weight) is equal to the density of the fluid multiplied by the gravity and the volume of the object.
Which essentially means that an object will float if the weight of the displaced fluid can balance with the weight of the object itself.
What is surface tension
Surface tension is the tendency for a liquid to minimize its surface area
due to the water molecules wanting to bond to each other rather than air
resulting in a net tension acting across the outer layer of a fluid
What is the units of surface tension and explain how to calculate it
N/m as dimensionally it is the force per unit length
To calculate it we to know the contact angle and the length of the interface where the contact is happening
to do this we define a tangent and use F(w) = 2 x F(s) cos theta
