Fluid Dynamics Flashcards
Fluid dynamics
how fluids flow
Viscosity
All fluids are viscous, but for water, it is negligible (pressure X time) or NsXm^2
Momentum divided by surface area
As temperature decrease, what happens to viscosity?
Viscosity increase. They have an inverse relationship
Laminar flow
A flowing fluid is composed of parallel layer that may be moving at different velocities
Poiseuille’s law (accounts for viscosity)
Q=pir^4changeP / 8nL
changeP=8nLQ/pir^4
Turbulent flow
Flowing fluid composed of mixed layers that vary dramatically in pressure and speed
a “mess”
represented by Reynolds number
Re = (density X velocity X diameter) / dynamic viscosity fluid
If the velocity is higher, what does that most likely mean for the turbulent?
Higher velocity= more likely the flow is to become turbulent
Poiseuille’s Law and proportions
Q is proportional to changeP
changeP is proportional to L
1/L is proportional to Q
Q is proportional to r^4 (so increasing radius will increase flow rate)
Bernoulli’s law
highly idealized fluids
- assume laminar flow
- neglect viscosity
- neglect interactions between the fluid and container
Bernoulli’s law equation
P1 + 1/pv^2 + pgh = P2 + 1/pv^2 + pgh Three terms on each side P= pascals kinetic energy potential energy pressure = energy/volume and this is what this equation boils down to
Bernoulli’s law equation proportions
at a constant height, increasing the velocity will decrease the pressure exerted on the container
Continuity equation
Within a closed system, the flow rate of a liquid is constant (Q1=Q2)
Q=V*A
liquids are incompressible
Velocity in a narrow tube compared to a wide tube
To get a volume to flow through a narrow section compared to a wider section, it’ll need to be faster
Venturi effect
linked to velocity
pitot tube = one ended tube, stagnation pressure
measure speed of airplanes, ship, wind
difference between stag and static = 1/2pv^2
