Fluid Properties

Question 1

What is the definition of a fluid in the context of fluid mechanics?

Answer 1

A substance that deforms continuously under the action of a shear forces.

Question 2

How is Density calculated/defined?

Answer 2

Density (ρ) is calculated as mass (m) per unit volume (V): ρ = m/V.

Question 3

How is relative density/specific gravity defined?

Answer 3

Relative density/specific gravity is the ratio of the actual density (ρ) to the density of water (ρ_water).

Relative density= ρ/1000

Question 4

How is pressure defined in fluid mechanics?

Answer 4

Pressure is the normal stress acting on a surface, typically measured in N/m² (Pa).

Question 5

What are the different types of pressures in fluid mechanics?

Answer 5

Types of pressure include absolute pressure, gauge pressure, and atmospheric pressure.

Question 6

How much does one Bar of pressure equal in Pa?

Answer 6

1 bar= 10^5 Pa

Question 7

What is gauge pressure and how does it differ from absolute pressure?

Answer 7

Gauge pressure is the pressure relative to atmospheric pressure, whereas absolute pressure includes atmospheric pressure.

Question 8

How to calculate Absolute Temperature

Answer 8

T(K)= T(C) + 273

Question 9

What is the Equation of State?

Answer 9

PV= mRT
P= ρRT
Where R is the gas constant (287 in air) and the gas is an ideal gas

Question 10

What is the combined gas law?

Answer 10

P₁V₁/T₁=P₂V₂/T₂

Question 11

What is viscosity?

Answer 11

The resistance of a fluid to deformation in the shear

Question 12

Relationship between Temperature and Viscosity

Answer 12

In liquids:
As temperature increases viscosity decreases

In gases:
As temperature increases viscosity increases

Question 13

What is the no slip boundary condition?

Answer 13

Fluid particles will “stick”, gain the same velocity as the surface they are in contact with due to their viscosity

Question 14

What is the boundary layer?

Answer 14

The layers of fluid where the particles are flowing slower then the mainstream flow

Question 15

What does inviscid mean and where is it observed?

Answer 15

Inviscid implies zero viscosity and is only observed in ideal fluids as all real fluids have some viscosity

Question 16

Define Newtonian fluids and give examples

Answer 16

Newtonian fluids are ones where the shear stress is directly proportional to the velocity gradient and they include air, water, petrol, oil