Fluid Mechanics 2

What is the Eulerian frame of reference?

Everything is related back to a fixed point of reference

What is the Lagrangian frame of reference?

The frame of reference moves with a fluid particle.

what does the material derivative find?

Lagrangian rate of change

Incompressible flow definition

Density of a particle is constant

continuity equation, material derivative and cauchy assumptions

continuum

what happens to body and surface forces when a fluid is static and there are no external body forces?

body force+surface force=0

Bridgmann theorem

Physical dimensions can be expressed as the product of fundamental dimensions raised to the power of a real number

what is the number of dimensionless groups?

n-r

what assumptions are used to measure the speed of sound?

c is constant, 1D, inviscid flow, no body forces, compression is infintesimally small

what is a chocked nozzle?

When the flow through the nozzle occurs at a Mach number of 1

when is the mass flowrate maximum inside a nozzle?

when the nozzle is choked

Bernoulli equation assumptions

steady flow, inviscid, incompressible, same streamline

isentropic flow assumptions

continuum, steady flow, no body forces, inviscid, perfect gas, isentropic, flow along a streamline

Euler assumptions

inviscid, continuum

What can particle motion be decomposed into?

Translation, rotation, deformation

Navier stokes assumptions

Incompressible, uniform viscosity, continuum, newtonian

How does velocity change in stokes first problem?

Plate suddenly set into motion at t=0

How does velocity change in stokes second problem?

Plate velocity varies by a certain function

how do bluff bodies cause boundary layer separation?

Downstream high pressure gradient and flow reversal in the boundary layer

how does a low Reynolds number affect wake and drag?

no separation, no wake, little drag

how does a high Reynolds number affect wake and drag?

flow separation, turbulent wake, form drag prevalent

how does an even higher Reynolds number affect wake and drag?

huge momentum deficit, smaller wake, higher drag

How are diffusers designed to minimise losses?

Change in cross section

What can turbulence be characterised as?

Unsteadiness of flow, range of scales, 3D vertical motion

What does energy cascade imply?

Kinetic energy of turbulence moves from large scales to small scales where it's dissipated by heat by viscous forces

boundary layer assumptions

continuum, incompressible, steady flow, no body forces, newtonian fluid

what additional assumptions are used for the Blasius solution?

d«L, self similarity, pressure gradient is 0