week 2 fluids Flashcards
what is a fluid
fluid has the ability to flow
can be a liquid or a gas.
gravity causes fluids to flow.
assume shape of the container
what is hydrostatics
the study of fluids that are NOT moving
fluids that are static what are two useful properties?
density and pressure
hydrodynamics
is the study of fluid in motion.
pressure formula
p= F/A F= force A= area
Pressure is inversely proportional to the area.
t/f?
true If you double the area (or diameter), you will decrease pressure by 4.
Imagine a beaker filled with water
How much pressure does the water exert on the bottom of the beaker?
The beaker measures 10 cm in diameter and the height of the water is 20 cm.
Only the weight of atmosphere is pushing down on the top surface of the water. Both the weight of the atmosphere and the weight of the water are pushing down on the bottom of the beaker. Obviously, the force pushing down on the bottom of our beaker is larger than theforce pushing down on the top of the water.
Pressure at the Same Depth
At the same depth in a fluid, the fluid exerts the same pressure and in all directions
is Pressure Is Independent of Container Shape
yes
Pascal’s Principle is?
The pressure applied to a confined fluid increases the pressure throughout the fluid by the same amount.
Example, if you increase the pressure on top of a confined fluid by 5 Pa, the pressure everywhere in the fluid goes up by 5 Pa
You’re applying a pressure of 3 psi on the plunger of a syringe with a plugged needle.
How does the pressure in the barrel compare to the pressure in the needle?
they are the same pressure.
Buoyancy
All fluids exert a buoyant force on objects immersed in them.
Archimedes Principles
An object immersed either totally or partially in a fluid feels a buoyant force equal to the weight of the fluid displaced.
If the density of the object is greater than the density of the fluid, it will what?
also vice versa
sink,
If the object sinks, the buoyant force is less than the true weight of the object.
Hydrometers
A hydrometer is a very simple device used to measure the specific gravity of liquids.
A hydrometer will sink until it displaces an amount of fluid exactly equal to its weight. If the fluid is dense, it will displace only a small amount of fluid and thus not sink very deep. If the density of the fluid is not very high, the hydrometer will sink deeper.
Hydrodynamics is the study of what kind of fluids?
moving fluids
Two types of flow are?
Laminar flow-unchanging flow pattern, smooth and orderly.
Turbulent flow-continuously varying pattern of flow, abruptly changing and chaotic.
In anesthesia we strive for laminar flow
Flow Rate is
The volume of fluid passing a particular point (e.g., the black line) per unit time.
Think about oxygen for a patient. We deliver a flow rate i.e. 3 liters/min.
Speed and Diameter: narrowing causes what to happen to speed?
slide 18
increases tremendously.
The flow rate remains the same.
if a patient has a larger tube you can have slower flows easier to ventilate
small tube you need higher flows. for more speed.
Bernoulli’s Principle is?
As the speed of a fluid increases, the pressure exerted by the fluid decreases.
This phenomenon is called theBernoulli effect
The Bernoulli effect provides the lift for airplanes and is why shower curtains get sucked toward you when you first turn on the shower. It also provides the basis for a Venturi flowmeter.
increase in speed will decrease the pressure of a fluid
Venturi Tube Flowmeter measures what
measure fluid speeds in pipes. and prevents turbulance
Venturi Tube Flowmeter is used for what
administering an albuterol nebulizer
Viscosity
Viscosity is a measure of a fluid’s resistance to flow.
Fluids with high viscosity (honey) do not flow very readily, while fluids with low viscosity (water) flow more easily.
The closer a molecule is to a wall, the slower it moves
T/F
true
Laminar Flow
When a fluid streams through a tube, the particles comprising the fluid may move along lines parallel to the walls of the tube.
Poiseuille’s Law applies to what
Poiseuille’s equation applies to laminar flow only.
radius and length are the two most important things
Poiseulle determined that the laminar flow rate of an incompressible fluid along a pipe is proportional to
the fourth power of the pipe’s radius.
Poiseuille’s equation yields three possible ways to increase the fluid flow rate through a catheter or needle.
First and foremost, increasing the pressure differential (P1−P2) across the catheter or needle can increase the flow rate.
Raise iv bag height. Add a pressure bag to IV
Use a larger gauge IV catheter.
Or a shorter length catheter.
Reynold’s Number is ?
Reynolds’ numberand is the measure of the tendency for turbulence to occur
when Reynolds’ number rises above approximately 2000, turbulence will usually occur even in a straight, smooth vessel.
laminar flow turns turbulent after 2000 ex in the ventricle into the aorta
For a given liquid and tube there is a critical flow rate above which the flow will become turbulent.
Reynolds number is less than approximately 2,000 will typically have laminar flow, while Reynolds numbers greater than 3,000 will result in turbulent flow. When the Reynolds number is between these two values, the fluid flow will be unstable, and the flow can transition between laminar and turbulent flow.
