Understanding flow and velocity

00:03

Before modeling water supply networks,

00:05

you must have a basic understanding of

00:07

the terminology used when discussing water pressure

00:10

flow is a unit of volume moving past a certain point within a unit of time

00:16

flow is measured in different units depending on its application.

00:20

Velocity is the distance of a given fluid within a unit of time

00:25

velocity is how fast a fluid is moving

00:28

for a given flow rate. It is disproportional to the pipe radius,

00:33

flow is equivalent to the velocity of the water

00:36

multiplied by the radius of the pipe squared,

00:39

the smaller the pipe, the greater the velocity at the same flow rate.

00:44

It is important to note that low velocities can result in sediment deposits.

00:48

While changes in velocity can lift and release these deposits

00:53

flow moving through smooth unobstructed pipework will move at

00:56

a constant velocity and is known as laminar flow

01:00

head loss is the combining of energy losses within a pipe such

01:03

as frictional contact with the pipe wall or bends in the pipe

01:07

flow that is disrupted by bends or roughness of a pipe wall is called turbulent flow

01:13

losses, increase velocities and flow rates requiring more energy to overcome

01:19

losses are usually measured per distance

01:22

in WS pro.

01:23

The Darcy Weisbach

01:24

equation is used to calculate head loss

01:27

in water networks.

01:29

A hydraulic transient refers to pressure changing with time

01:32

and typically reflects rapid or unexpected changes in pressure

01:37

in the water industry. It is often referred to as a surge or water hammerer.

Video transcript

00:03

Before modeling water supply networks,

00:05

you must have a basic understanding of

00:07

the terminology used when discussing water pressure

00:10

flow is a unit of volume moving past a certain point within a unit of time

00:16

flow is measured in different units depending on its application.

00:20

Velocity is the distance of a given fluid within a unit of time

00:25

velocity is how fast a fluid is moving

00:28

for a given flow rate. It is disproportional to the pipe radius,

00:33

flow is equivalent to the velocity of the water

00:36

multiplied by the radius of the pipe squared,

00:39

the smaller the pipe, the greater the velocity at the same flow rate.

00:44

It is important to note that low velocities can result in sediment deposits.

00:48

While changes in velocity can lift and release these deposits

00:53

flow moving through smooth unobstructed pipework will move at

00:56

a constant velocity and is known as laminar flow

01:00

head loss is the combining of energy losses within a pipe such

01:03

as frictional contact with the pipe wall or bends in the pipe

01:07

flow that is disrupted by bends or roughness of a pipe wall is called turbulent flow

01:13

losses, increase velocities and flow rates requiring more energy to overcome

01:19

losses are usually measured per distance

01:22

in WS pro.

01:23

The Darcy Weisbach

01:24

equation is used to calculate head loss

01:27

in water networks.

01:29

A hydraulic transient refers to pressure changing with time

01:32

and typically reflects rapid or unexpected changes in pressure

01:37

in the water industry. It is often referred to as a surge or water hammerer.

Video quiz

When modeling water supply networks, velocity refers to which of the following?

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Before modeling water supply networks, you must have a basic understanding of the terminology used when discussing water flow and velocity.

  • Pressure Flow — a unit of volume moving past a certain point within a unit of time. Flow is measured in different units, depending upon its application.
  • Velocity — the distance of a given fluid within a unit of time, or how fast a fluid is moving.
  • Flow — equivalent to the velocity of the water multiplied by the radius of the pipe squared. The smaller the pipe, the greater the velocity at the same flowrate.
  • Low velocities can result in sediment deposits, while changes in velocity can lift and release these deposits.
  • Flow moving through smooth, unobstructed pipework will move at a constant velocity and is known as laminar flow.

The formula for flow, with definitions for each symbol displayed. A diagram of a pipe that begins wide and narrows on the other side demonstrates changes in velocity.

  • Headloss — the combination of energy losses within a pipe, such as frictional contact with the pipe wall or bends in the pipe.

A diagram showing a pipe with directional flow. Two pipes connect at the top of the pipe, showing headloss from one to the other.

  • Turbulent flow — flow that is disrupted by bends or roughness of a pipe wall.
  • Losses — increase velocities and flowrates, requiring more energy to overcome. Losses are usually measured per distance. In WS Pro, the Darcy-Weisbach equation is used to calculate headloss.
  • Hydraulic transient (a.k.a. surge, water hammer) — in water networks, refers to pressure changing with time and typically reflects rapid or unexpected changes in pressure.

A graph showing rapid changes to pressure over a span of time.

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