FLUID MECHANICS Flashcards
what are the 2 type of force acting on object by fluid and its due to what
Buoyant force
Due to immersion
Dynamic force
Due to relative motion in fluid
what is buoyant force
a vertical, upward-directed force acting upon an object that is submerged or partially submerged in a fluid.
Buoyant force is the difference between the force acting upward on the cube and the force acting downward on the cube.
what is archimedes principle
a body submerged in a fluid will be buoyed up by a force that is equal in magnitude to the weight of the displaced water.
the size of buoyant force is equal to what
the weight of the volume of fluid displaced by the object. This depends on how much water is pushed out of the way by the object.
Two key concepts of pressure needed to understand buoyant force
All points of a submerged body, at a given depth, will experience the same pressure.
Pressure increases in large increments with relatively small changes in depth.
If the cube of material weighs more than the cube of water, what happen
the buoyant force acting upward is less than the weight acting downward, and the cube will accelerate downward.
If the cube of material weighs more than the cube of water, what happen
the buoyant force acting upward is less than the weight acting downward, and the cube will accelerate downward.
If the cube of material weighs less than the cube of water,
the buoyant force acting upward is more than the weight acting downward, and the cube will accelerate upward
If the cube of material weighs the same as the cube of water,
the buoyant force acting upward equals the weight acting downward, and the cube is in equilibrium.
An object with a density less than the fluid it is immersed in will sink or float.
float
Whether or not something floats is determined by
the volume of the object immersed and the weight of the object compared to the weight of the same volume of water
Something with a specific gravity of 1.0 or less will sink or float.
float
what is center of buoyancy
the center of gravity of the displaced volume of water, equal in shape and volume of the submerged object that is displaced.
what does an object needs to have its center of gravity and center of buoyancy to have the same location
to have relatively uniform density
where does the center of buoyancy is locateed in a human body
superiorly to the center of gravity.
The line of action of gravitational force through the center of gravity will be vertically downward/upward
The line of action of buoyant force through the center of buoyancy will be vertically downward/upward.
downward
upward
Dynamic fluid force vector can be resolved into two components:
perpendicular component: lift
vertical component: drag
what is the drag force
the parallel component of dynamic fluid force that acts in the opposite direction of system motion with respect to the fluid.
Tends to resist motion of the system through the fluid
which force tend to resist motion of the system
drag force
The greater the decrease in velocity of the molecules and the faster the rate of this decrease, the greater/smaller the total drag.
greater
Drag forces are produced by two different means
surface drag and form drag
what is surface drag
Surface drag may be thought of as equivalent to the sum of the friction forces acting between the fluid molecules and the surface of the object.
what is form drag
Form drag may be thought of as equivalent to the sum of the impact forces resulting from the collisions between the fluid molecules and the object.
what is form drag and how does it vary
due to a relatively higher pressure on the leading edge of the object compared to its trailing edge.
The larger the changes in direction, the larger the forces exerted.
Form drag thus increases as the amount of turbulent flow increases.
what is a lift force
the perpendicular component of dynamic fluid force that acts in any direction that is perpendicular to the system motion with respect to the fluid.
Lift tends to change the direction of system motion.
which force tend to change the direction of a system in motion
lift
T/F A lift force can be directed upward, downward, or in any direction
true
The possible directions of the lift force are determined by
the direction of flow of the fluid
The possible directions of the lift force are determined by
the direction of flow of the fluid
more particule under the object result in what type of lift
upward lift
more particule above the object result in what type of lift
downward
what is magnus force
lift cause by rotation
