Using a Flume to Demonstrate Fluid Properties and Sediment Transport
A laboratory recirculating flume offers ideal opportunities for conducting demonstrations designed to help students observe and understand a variety of fluid properties and the basics of sediment entrainment and transport.
Skills and concepts that students must have mastered
The demonstrations are scheduled to coincide with the discussion of the topic during lecture. Each demonstration takes only a portion of the total class time and can be used to introduce a topic or take place after a lecture to illustrate and reinforce the concept/process. Each demonstration discussed in the 'activity description' (linked near the bottom of this page) explains the concepts that students learn before and after the activity.
How the activity is situated in the course
The demonstrations can easily be completed during a 90-minute class period. One or more demonstrations can be combined, but done as stand-alone exercises breaks up the learning and allows for connecting the demonstration to the lecture.
Content/concepts goals for this activity
Fundamental fluid behavior (transition from laminar to turbulent flow) is critical to understanding sediment entrainment, transport, and depositional processes. The demonstrations are designed to build upon each other, starting with observing streamlines for laminar and turbulent flow conditions (demonstration 1), estimation of critical threshold velocity (demonstration 2), migration of ripples (demonstration 3), and density flows (demonstration 4). Students are asked to observe and record their observations, noting important sedimentary processes, and explore what happens when parameters/flow conditions change (e.g., water depth, velocity, degree of turbulence, and density differences). The flume demonstrations also help students learn about models and scale (benefits and limitations of using flumes to model real-world fluvial processes).
Higher order thinking skills goals for this activity
Students measure water depth, velocity (using a Marsh-McBirney portable current meter), use ink to define streamlines, and carry out other observations to confirm/modify their predictions about flow behavior and sediment transport processes.
Other skills goals for this activity
Demonstrations involve students participating in setting up the flume (filling, water temperature, placement of bed material), recording velocities, and documenting their observations (sketching and describing what they see). The open-ended nature of the demonstrations also supports students posing questions. For example, "what if an obstacle was on the bed?" answered by experimenting with the placement of different sized/shaped objects on the bed, using ink streamers to see if they observe flow separation, and/or scouring of sediment behind the obstacle.
Description of the activity/assignment
A 20-foot long recirculating flume is used for a series of demonstrations designed to help students explore the principles of fluid dynamics and sediment transport. The design and construction of the flume and four demonstrations are described in the attached activity. The demonstrations build upon each other so that students have a chance to develop an understanding of sedimentary transport processes and the deposits they produce.
Determining whether students have met the goals
Discussions take place before, during, and after each demonstration. The students are asked to draw their sketches on the board as part of the post-demonstration discussions, and exam questions require students to describe and explain what they observed during the flume demonstrations.
Teaching materials and tips
Activity Description/Assignment (Microsoft Word PRIVATE FILE 72kB Jul3 06)
[file 'Instructors Notes']
[file 'Solution Set']
Poster with ideas for teaching students about fluid properties and particle transport (Acrobat (PDF) PRIVATE FILE 1.4MB Aug31 06) Poster about the design and construction of the flume and wave tank (Acrobat (PDF) PRIVATE FILE 796kB Sep13 06) A PowerPoint slide presentation to accompany John McPhee's essay 'LA Against the Mountains' (PowerPoint PRIVATE FILE 23.8MB Jul4 06)
Photo of flume tank and schematic diagram
Students simulate a turbidity current by pouring milk into the flume tank.
(Click on any image to enlarge)
- Sediment transport movies
- The Control of Nature, John McPhee