1.

Segment V8.1: Laminar/Turbulent Pipe Flow
(Related to Textbook Section 8.1.1 - Laminar or Turbulent Flow)

Whether flow in a pipe is laminar, transitional, or turbulent depends on the value of the Reynolds number.

In this experiment water flows through a clear pipe with increasing speed. Dye is injected through a small diameter tube at the left portion of the screen. Initially, at low speed (Re <2100) the flow is laminar and the dye stream is stationary. As the speed (Re) increases, the transitional regime occurs and the dye stream becomes wavy (unsteady, oscillatory laminar flow). At still higher speeds (Re>4000) the flow becomes turbulent and the dye stream is dispersed randomly throughout the flow.

2.

Segment V8.2: Turbulence in a Bowl
(Related to Textbook Section 8.3.2 - Turbulent Shear Stress)

Turbulent flow can often be thought of as a series of random, 3-dimensional eddy motions (swirls) ranging from large eddies down through very small eddies.

The turbulent nature of the flow of soup being stirred in a bowl is made visible by use of small reflective flakes that align with the motion. The initial stirring causes considerable small and large scale turbulence. As time goes by, the smaller eddies dissipate, leaving the larger scale eddies. Eventually, all of the motion dies out. The irregular, random nature of turbulent flow is apparent.

3.

Segment V8.3: Laminar/Turbulent Velocity Profiles
(Related to Textbook Section 8.3.3 - Turbulent Velocity Profile)

The velocity profile for laminar flow in a pipe is quite different than that for turbulent flow.

An approximation to the velocity profile in a pipe is obtained by observing the motion of a dye streak placed across the pipe. With a viscous oil at Reynolds number of about 1, viscous effects dominate and it is easy to inject a relatively straight dye streak. The resulting laminar flow profile is parabolic. With water at Reynolds number of about 10,000, inertial effects dominate and it is difficult to inject a straight dye streak. It is clear, however, that the turbulent velocity profile is not parabolic, but is more nearly uniform than for laminar flow.

4.

Segment V8.4: Entrance/Exit Flows
(Related to Textbook Section 8.4.2 - Minor Losses)

Entrance and exit flow into and out of a pipe are two common components of pipe systems.

The character of entrance and exit flow at the nozzle of a shop vac is noted by what happens to particles on a flat surface. In the "blowing" mode (exit flow) a narrow jet of air extends many diameters from the nozzle exit. Only particles directly in front of the exit are moved by the flow. In the "suction" mode (entrance flow) only particles in the immediate vicinity (both directly in front and on the sides) of the nozzle are moved.

5.

Segment V8.5: Car Exhaust System
(Related to Textbook Section 8.4.2 - Minor Losses)

Pipe systems often contain multiple pipes in series or parallel in addition to system components other than straight pipes.

Although simple in concept, a rather complex pipe system is needed to carry engine exhaust from the unsteady outlet flow at the exhaust valve ports of the engine block to the nearly steady flow at the end of the exhaust pipe. In addition to numerous curves and corrugations in the pipes, the system contains a muffler with its complex flow geometry, an exhaust header (or manifold) with its parallel pipe configuration, and other components.

6.

Segment V8.6: Rotameter
(Related to Textbook Section 8.6.1 - Pipe Flowrate Meters)

It is often necessary to determine the volumetic flowrate of a fluid in a pipe. A rotameter can be used for such purposes.

The main elements of a rotameter are a tapered tube through which the fluid flows and the float within the tube. The equilibrium height of the float within the tube is a function of the flowrate and represents a balance between buoyant, weight, and drag forces on the float. As the flowrate in the pipe increases or decreases, the water bubbles higher or lower from the exit and the float in the rotameter rises or falls.

7.

Segment V8.7: Water Meter
(Related to Textbook Section 8.6.2 - Volume Flow Meters)

In many cases knowledge of the volume of fluid that has passed through a pipe is of interest rather than the instantaneous flowrate. Such volume-measuring devices are called volume flow meters.

The household water meter, a nutating disk volume flow meter, contains only one moving part - a nutating circular disc. Water flowing through the chamber that houses the disc forces it to wobble (nutate). To complete "one wobble" of the disc, a known amount of fluid must pass through the meter. A counter connected to a pin on the disc measures the number of wobbles (and thus the fluid volume that has passed through the meter).