1P1 Fluid Mechanics Flashcards
Define a fluid.
A fluid cannot sustain shear stress when at rest.
Key facts about pressure.
Pressure acts noramlly to surfaces
Pressure acts uniformally in all directions
Pressure in a manometer.
pm = rho x g x h + patm
How does a mercury barometer work?
Weight of mercury in the column = atmospheric pressure
How do you calculate total force on a submergd plate?
Integrating the forces along it with respect to area.
How do you find the centre of pressure?
Integrating the moments to find the average moment arm needed to balance the force.
Quick way to find horizontal force on a submerged plate.
Find the force on a submerged vertical plate wiht the same projected area.
Quick way to find vertical force on a submerged plate.
Find the total weight of the water above the plate.
Define the streamline.
A line which are in line with the velocity vectors at each point in flow.
Define a stagnation point in a flow.
Where the flow velocity is zero.
What is flow seperation?
When flow perpetrates from the surface when they cannot follow its curvature.
Define unsteady flow.
The trajectory of a particle will change with time.
Define the no slip condition.
The fluid at the surface of a body will have 0 velocity.
Define the boundary layer.
The layer of fluid around a body where the velocity varies.
Define inviscid flow.
Flow where the effects of friction are ignored.
What causes flow seperation.
Viscosity.
What is true for a control volume in steady flow?
A region of fluid where the net mass flow in and out of the volume is zero.
mdot in = mdot out
How do you calculate mass flow with a non uniform velocity distribution?
mdot = integral(rho x v x dA)
How do you calculate mass flow with velocity which is not perpendicular to the area?
mdot = rho x A x vn (normal component of velocity)
Integral form of momentum flow rate.
integral(rho x vel in direction
xv . dA)
Where do you derive Bernoulli’s eq from?
Apply newton 2 to a fluid element in the streamwise direction.
F = -(dp/ds) dV
F = ma = mv(dv/ds)
Then equate and integrate.
What assumptions must you make to apply Bernoulli’s eq?
That the flow is incompressible
That it is used along a streamline (sometimes can be used throughout a flow)
Where does the normal point in fluid dynamics?
Away from the centre of curvature.
How do you derive the eq for pressure gradients with streamline curvature?
Apply N2 vertically using a pressure differentia.
Then use eq for centripetal force of mv^2/r
What is the Coanda Effect.
A jet of fluid will attach itself to a body due to its curvature
