Fluid Properties Flashcards
Define fluid mechanics:
the study of fluids at rest or in motion
Define thermal science:
the study of energy used and transformations from one form to another
or
the study of energy flow that is caused by a temp. difference
Define solids, liquids, and gases
solids: molecules are arranged in a pattern repeated througout
liquids: molecules can move and rotate freely
gases: molecules are far apart, molecular arrangement non-existent
What is the difference between a solid and a fluid?
a fluid is a substance that deforms continuously when acted upon by a shear stress, while a solid deforms but not continuously
What does it mean to assume a substance is continuum?
disregarding atomic nature of substance and assuming it is continuous, homogenous, with no holes
When can we assume a substance is continuum, and why?
if the size of molecules is relatively large compared to the size of the gaps between molecules
why? so that we can assume that the substance properties vary continually
When do liquids evaporate?
when the molecules have enough energy to overcome intermolecular cohesion forces
What is vapour pressure?
pressure exerted by its vapour in phase equlibrium with its liquid at a given temperature
When does condensation occur and when does evaporation occur?
condensation: when pressure is higher than vapour pressure
evaporation: pressure lower than vapour pressure
Define saturation pressure:
the pressure at which water vapour is in equilibrium with the liquid state
Define saturation temperature:
temperature at which a given substance changes phase at a given pressure
What is partial pressure?
the pressure of a gas or vapour mixed with other gases
What is cavitation?
formation and collapse of vapours
What are microscopic forms of energy?
related to molecular structure and degree of molecular activity of a system
What is internal energy?
it is the sum of microscopic energies of a non-flowing fluid
What is enthalpy?
it is the microscopic energy of a flowing fluid
What is specific heat?
it is the amount of energy required to raise the temp. of a unit mass by 1 degree
What is macroscopic energy?
energy of a system as a whole, relative to a reference frame
What is a water hammer?
occurs when a valve/pump is shut down suddenly causing the water pressure to rise and fall rapidly
Define sonic speed:
speed at which an infinitesimally small pressure wave travels through a medium
or
velocity at which small disturbances propagate
Define adiabatic:
no heat flow in or out of the system
Define Isentropic:
flow is adiabatic and reversible
Define viscosity:
property of fluid that represents the internal resistance of a fluid to motion
What causes viscosity in fluids?
in liquids: molecular cohesive forces
in gases: molecular collisions
Define drag:
the measure of force applied by a flowing fluid on a body in the direction of flow
What is the difference between Newtonian and Non-Newtonian fluids?
Newtonian fluids viscosity is not affected by the shear rate while Non-Newtonian fluids viscosity changes with deformation
List some Non-Newtonian fluids w/ definitions:
Dilatant: “shear thickening”, viscosity increases w/ increasing rate of deformation
Pseudoplastic: “shear thinning”, viscosity decreases with increasing shear stress
Bingham: acts as a solid at small shear stress then deforms as shear stress increases
Define dynamic viscosity:
measure of force, internal resistance required to move a fluid
Define kinematic viscosity:
measure of velocity of a moving fluid
Define surface tension:
pulling force at surface per unit area
Define contact angle:
the angle the liquid surface makes with the solid surface at a point of contact
Define cohesive forces:
forces between like molecules
Define adhesive forces:
forces between unlike molecules
What defines wetness of liquid?
relative magnitude of forces
Define capillary force:
force able to pull water into ground
