Momentum Conservation Flashcards
What is Newtons 2nd Law?
The rate of change of momentum is equal to the sum of the forces
What are the forces acting a fluid?
- Pressure
- Gravity
- Density differences
- Friction/Viscosity
- Forces exerted by a solid surface e.g., a water jet hitting a flat plate
How is momentum calculated?
m*U in the x direction
How can sum of momentum be found?
Finding the integral of Ο*U dv
What is the surface force?
Due to stress, proportional to total surface area in which it acts
What are body forces?
Forces acting on a fluid mass
What is the unsteady momentum equation?
ππ (πππβ πππ’π‘) + π
When can we expect the pressure in a moving fluid to be hydrostatic?
As long as the vertical acceleration π_π is negligibly small.
When is vertical acceleration negligible?
If the streamlines
are nearly horizontal without significant curvature
What is pressure like in closed conduits?
Constant
What does S stand for in the momentum equation?
The sum of horizontal forces
What is the force like in converging pipes?
- Neglect friction losses
- Flow driven by pressure differences
- Force exerted by pipe onto fluid
- Flow accelerates so resultant force exists on the fluid
How do you find surface area?
PR where P = ΟD
What does shear stress exert?
A force over an area
What gives a larger pressure gradient?
More friction
