5.14. (9/27) Bernoulli's Law: Pressure/Viscous Forces Flashcards
What does Bernoulli’s law describe?
when a solid object interacts with a fluid, a differential pressure (pressure on top vs bottom) can be created on the solid object that can push it in a certain direction
*in any (moving) fluid, the overall pressure head of it is a function of elevation/static pressure/velocity
What does Bernoulli’s equation say?
an elevation term + pressure term + velocity term = a constant
*conditions at one point have to equal the conditions at another point
What is the equation for Bernoulli’s law?
h1 + p/ρg + U1^2/2g
What do we know about fluids?
as it goes faster, the pressure it exerts is less
* inverse relationship
What is the velocity of the water where it hits your leg?
U = 0
How do we find static pressure?
ρgh density * gravity * elevation
How do you find velocity?
2sqrt(gh2) (3)
*h2 = height of risen water
What was the velocity meter doing?
it was measuring the pressure differential across its bulb
*The pressure differential was following Bernoulli’s Law to find velocity
How do we find discharge?
Q= Velocity * area (1)
What is the velocity gradient concept?
(4) the velocity at the bottom of a flow is 0, but it bows out to a maximum and sinks back in which is why we set it to 6/10 (60%) depth because that is where it averages
*velocity curve
How does a fluid behave in terms of the velocity gradient?
change in u as a function of h (change of velocity as a function of depth)
a shear stress changes linearly whose slope is viscosity
what is the equation for velocity profile?
τ= μ(dU/dh)
What terms does Reynold’s Number put together?
relates viscosity term to velocity + particle size + density of fluid
What is the Reynold’s Number?
tells us when a flow is laminar or not
*it is dimensionless
