3650 fluid dynamics Flashcards
gas
molecular proximity defined by container
states of substances
gas liquids solids but all fluids and beyond solid are plasmas
dynamic forces
lift and drag
static forces and what they depend on
pressure and buoyancy - position, size, structure
pressure
acting down on the substance
weight
mg, pulling the substance down
drag (2)
resistive force that results from DISORDERLY collisions with fluid molecules
opposing the action
lift
pushing object up
buoyancy (2)
supportive force produced by displacement of ORDERLY fluid molecules
- initially would not have if we dont have it in order until the fluids rearrange itself
pushing object up
density and buoyancy
less dense -buoyant
sum of Fy
-RU-w+RB
RU and RB depends on
volume
w depends on
mass
density
mass/volume
if the object has more volume
more buoyant
object density =1
stay in the middle
object density <1
float
object density >1
sink
drag increases with (4)
object cross section
fluid density
object velocity
fluid flow parameters
laminar vs turbulent flow
straight undisturbed layers vs tiny disturbed whirpools
with drag in the front
laminar flow tears up to create turbulent flows - disorganized
laminar flow range (I)
smooth surface/low velocity - attract fluid molecules to it (surface layer) because of collisions of molecules equals high surface drag
partially turbulent flow range (I)
pair of separation points with more velocity - some form drag
turbulent low pressure wake in the back
decreased surface drag
decreased support of fluid force from behind
Partially turbulent flow range (II)
high velocity - more formed drag
little surface dry
decreased boundary
earilier separation point of boundry layer
with rougher surface
more surface drag, full turbulent flow follows keeping the support behind
if normal velocity puts it at the top end of 2, better to make surface
rougher - to make the fluid more viscous so the boundry layer becomes fuller
magnus effect
on top you have lower velocity and high pressure
below you have high velocity and low pressure - pushing it down
boundary layer of air spinning with ball’s surface - surface drag
surface thrust - pulls molecucles higher
gear effect
the ball keeps on bending - spin of the ball
lift
supportive force produced by relative pressure on opposite sides of an object
an object with a bump on its back
low pressure/high velocity on top and high pressure/low velocity on the bottom so it gets lifted - packet of air ends up at the same time
