Fluid Properties Flashcards
What’s a fluid?
A fluid is a substance in either the liquid or gas phase.
What’s a modeled continuum?
A substance that can be divided into infinitesimally small volumes, with properties that are continuous functions over the entire volume.
What’s the density?
It is the mass per unit volume of a fluid
What’s the specific volume?
It’s the volume occupied by a unit of mass.
What’s the specific weight?
It’s the weight of a substance per unit volume.
What’s specific gravity?
Its the dimensionless ratio of a fluid’s density to the density of water or specific weight of the fluid to the specific weight of water.
What’s absolute pressure?
The pressure measured with respect to a true zero pressure reference.
What’s gage pressure?
The pressure measured with respect to atmospheric pressure.
What is standard atmospheric pressure equal to?
Either 101.3 kPa or 29.9 inches of Mercury.
How are atmospheric and gage pressure related?
The absolute pressure is equal to the addition of the atmospheric pressure and gage pressure.
What are barometric pressures?
Barometric pressures are atmospheric pressures.
What is a vacuum pressure measurement?
It’s a negative gage pressure.
How are atmospheric and vacuum gage pressure related?
The absolute pressure is equal to the difference of the atmospheric pressure and vacuum gage pressure.
What is stress?
It is the force per unit area.
How many types of stress are exist and what are they?
Two. Normal stress and shear stress.
What is normal stress?
In normal stress the area is normal to the force.
What is tangential or shear stress?
In shear stress the area is parallel to the force.
How are Normal stress and pressure related?
The normal stress is equal to the pressure of the fluid.
What is the viscosity of a fluid?
Is a measure of that fluid’s resistance to flow when acted upon by an external force.
What is Newton’s Law of Viscosity?
Its the equation used to find the shear stress for Newtonian fluids.
What are Newtonian fluids?
Strains are proportional to the applied shear stress. The stress versus strain curve is a straight line.
What is the Power Law?
Its the equation used to find the shear stress for non Newtonian fluids.
What are non Newtonian fluids?
Fluids that have viscosity that change with shear rate.
How many Non Newtonian fluids exist and what are they?
There are two non Newtonian fluids and they are pseudo plastic fluids and dilatant fluids.
What are pseudo plastic fluids?
Fluids that exhibit a decrease in viscosity the faster they are agitated.
What are dilitant fluids?
Fluids that exhibit an increase in viscosity the faster they are agitated.
What is kinematic viscosity?
Is the absolute viscosity divided by the mass density.
What is surface tension?
The tensile force between two points a unit distance apart.
What is capillary action?
The action caused surface tension between the liquid and a vertical solid surface.
How many capillary actions are there and what are they?
There are 2 capillary actions and they are capillary rise and depression.
What are adhesive forces?
Are the attractive forces between the liquid and solid surfaces.
What are cohesive forces?
The attractive forces between the water molecules themselves.
What is a meniscus?
The curved surface of the liquid caused by the adhesive or cohesive forces.
What is a capillary rise?
When the adhesive forces dominate and the meniscus is above the general liquid surface level.
What is a capillary depression?
When the cohesive forces dominate and the meniscus is below the general liquid surface level.
What is the angle of contact?
Is an indicator of whether adhesive or cohesive forces dominate.
When does the angle of contact indicate adhesive and cohesive dominance?
For contact angles less than 90 degrees adhesive forces dominate for angles greater than 90 degrees cohesive angles dominate.
What does the capillary equation determine?
The capillary equation determines the height of the rise or depression.
What does a positive or negative capillary equation result determine?
A positive determines a rise and negative a depression for the meniscus.
