Lecture 10

Question 1

What is the integral roughness k_i?

Answer 1

The integral roughness k_i is an increased roughness value that provides the same energy loss as the calculatio of the energy loss through the addition of the individual losses and friction losses

Question 2

What does the integral roughness k_i take into account?

Answer 2

• Friction losses due to wall roughness
• Local losses, e.g. due to pipe joints and fittings
• Installations

Question 3

What does the calculation of the energy head losses with the integral roughness results in?

Answer 3

• lolles due to continously occuring flow resistnaces (friction losses) and
• losses due to discontinously occuring flow resistnaced (local losses)

Question 4

What are the funtions of drinking water pumping systems?

Answer 4

• Overcoming height differences (e.g. when pumping from a lake to a water reservoirs) at a given flow rate
• Overcoming energy loss in pipelines

Question 5

What does the pump characteristics curve show?

Answer 5

Relationship between flow rate and total head

Question 6

What is the operating point?

Answer 6

Intersection between pump characteristic curve and pipe charactersitic curve

Question 7

What are causes for dynamic changes in pressure p?

Answer 7

• intertia of the water
• elasticity of the water
• elasticity of the pipe wall

Question 8

What do spread and superimposition of pressure change?

Answer 8

• move within the pipeline from the “point of distrubance” as a pressure surge to both sides (direct wave)
• are reflected at points of discontinuity as overpressure or underpressure water hammers depending on the boundary conditions (indirect waves)
• direct and indirect waves overlap

Question 9

What are points of discontinuity?

Answer 9

• changes in cross-section, branches and fittings

Question 10

Name the Reynolds number for laminar and turbulent flow?

Answer 10

Laminar flow: Re < 2320
Turbulent flow: Re > 2320