Fluid mechanics

Question 1

What is shear stress?

Answer 1

The force that acts parallel to the surface per unit area

Unit = Pascal (Pa)

Question 2

What is shear rate?

Answer 2

It is the velocity gradient set up in the liquid due to the applied shear stress
Unit = s-1

Question 3

What is a Newtonian fluid?

Answer 3

A fluid that has constant viscosity and is independent of stress. Examples include water, milk and juices

Question 4

What is a non-newtonian fluid?

Answer 4

A fluid where its viscosity changes when a force or pressure is applied. Examples include honey and ketchup

Question 5

What is viscosity?

Answer 5

A physical property that describes the resistance of a material to shear-introduced flow. It is given by the ratio of shear stress to shear rate

Question 6

Reynold’s number at laminar flow conditions?

Answer 6

< 2100

Question 7

Reynold’s number at transitional flow conditions?

Answer 7

2100 < Nre < 4000

Question 8

Reynold’s number at turbulent flow conditions?

Answer 8

> 4000

Question 9

What is mean velocity?

Answer 9

It is the volumetric flow rate divided by the cross-sectional area of the pipe

Question 10

What is friction factor?

Answer 10

the friction factor is the ratio between the shear stress at the wall, σw to the kinetic energy of the fluid per unit volume.