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Flashcards in Fluid flow Deck (16)
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1

What is the formula for pressure in a fluid column?

height*density*gravity Mass = kg density = rho gravity = 9.81m/s^2

Note that pressure is the same in all directions and is independent of the size of the object on which pressure is being exerted.

 

t

2

  Explain Bernoulli's' equation

Bernoulli's' equation is about the conversation of energy in fluid flow. It states that as fluid flows into a narrowing pipe the velocity will increase which means that the pressure will decrease. When a fluid flows in an expanding pipe the opposite happens.  

3

4

What does mu μ symbolise in fluid dynamics

Viscocity

5

What does V symbolise in fluid dynamics

Relative velocity

6

Explain viscocity

Viscocity is a measure of a fluids resistance to deformation. The symbol is μ and it is measured in (kg/ms). This is a result of the friction between the different layers.

 

7

Explain Stokes law

Stokes law calculates the drag on an object as it travels through a fluid.

FD = 6πRμV

F = Drag force on the sphere

R= radius of the sphere

μ = viscocity of the fluid

V = relative velocity of the sphere

 

8

What is the relationship between viscocity and the reynolds nubmer

Reynolds number = inertia force/ (viscouse force)

9

Explain terminal velocity in a sphere.

Terminal velocity is the balance between the acceleration of gravity and the countering forces. The primary oppositional force is drag followed by buoyancy.

For a sphere this is 

 

(Sphere Density-Fluid density)*(Sphere Volume)*(Gravity)

6πR*fluid viscosity

 

((ρsf)*(4/3πR3)*(9.81))

(6πRsμ)

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11

Explain Pouseuille's equation for pressure drop in a

Note this applies for laminar flow of viscous fluid in a straight pipe only

Pressure drop = 32*viscocity*length*average velocity

              Diameter2

 

ΔP = (32*μL)*V(Bar)/D2

 

12

Explain the fanning friction factor

This is a dimensionless number that relates to the fluid flow in a pipe. 

In a round pipe it is taken to be 16/Reynolds number.

This can also be calculated as 16μ/ρVD

 

13

What is the hydrolic dyameter

It is a metric for creating an equivalent round diameter pipes for non round pipes. It is calculated from 4A/P

P is wetted perimeter.  

14

Explain the velocity pressure equation.

4*Friction*Length*density*average velocity squared

2 * diameter

4fLρV2/2D

 

15

Explain the velocity profile in laminar fluid flow

Velocity is slower and the boundary of fluid flow than the centre of fluid flow. The difference is called the boundary profile. 

 

 

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