Thermofluids Year 1 Definitions

What is a streamline

A curve though the fluid tangent to the local velocity at each point

What is a steady flow

A flow where the flow velocity at a point does not change with time

What is transient flow

A flow that changes for a short period before becoming steady

What does Euler’s equation state

The velocity of a fluid particle as it moved along as streamline is caused by two effects, pressure differences and gravity

What is a substantive derivative

It describe how a property changes following a fluid particle along its path

What does Bernoulli’s equation state

The sum of a fluids pressure, kinetic energy and potential energies per unit volume is constant along a streamline

What are the assumptions about the flow for Bernoulli’s equation

The flow is steady, incompressible, and frictionless

What is energy density

The amount of energy per unit volume

What is stagnation pressure

The total pressure a fluid would have if it were brought to rest with no losses

What is static pressure

The pressure of the fluid when stationary

What is dynamic pressure

Pressure due to the fluids motion

What does a ‘head’ refer to

The height of a hydrostatic column of the fluid which would yield a corresponding amount of pressure

What is a fluid

A substance that flows rather than deforming

What is a shearing force

A force that acts in a direction parallel to the surface, causing one layer of the material to slide past another layer

What is shear stress

The internal force per unit area that resists the shearing force

What is shear strain angle

Shows how much a material shape deforms due to an applied shear stress

What is the continuum hypothesis

The fluid is treated as a continuous substances with no gaps or holes

What is strain rate

The rate of change in shear strain angle

What is Newtons Law of viscosity

The shear stress between fluid layers is directly proportional to the velocity gradient between the layers

What are Newtonian fluids

A fluid whose viscosity stays constant no matter how fast the fluid layers pass each other

What is viscosity

The resistance to shear stress

What does the continuum approximation allow

Define fluid properties as if they are continuous variables

What is Pascel’s Principle

When a change of pressure is applied in an enclosed incompressible fluid, the pressure change is transmitted equally throughout the fluid in all directions

What is gauge pressure

Pressure measured relative to atmospheric pressure

What is absolute pressure

Pressure measured relative to a vacuum

What is a planer surface

A perfectly flat surface

What is another name for Archimedes’ Principle

Law of buoyancy

What does Archimedes’ Principle state

Any object that is wholly or partially submerged in a fluid experiences an upward buoyancy force equal to the weight of the fluid displaced

What is Viscosity

The resistance to shear stress

What are the three charateristics of pressure

The force resulting from pressure on a surface acts perpendicular, pressure at a point in a fluid at rest is the same in all directions, the pressure applied to the fluid is transmitted everywhere throughout the fluid