Project Description

	Mainstream Sediment Trap
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University Of Idaho Senior Design Project for the Center for Ecohydraulics Research Objective Design, fabricate, and test a sediment trap system capable of trapping and weighing sediment that is traveling down the bed of a large flume. The sediment must then be removed from the trap and transported to a waste bin located in the alley behind the laboratory. Background The Center for Ecohydraulics Research (CER) is located in the Idaho Water Center (IWC) in downtown Boise. The Center for Ecohydraulics Research Stream Laboratory (CERSL) is a 2500 square foot lab located on the first floor of the IWC. The CERSL features a high gradient sediment flume designed in close collaboration with state and federal agencies and several of the major research laboratories in academia. The facility has been carefully designed to fill a current void in laboratory facilities to study the interaction of sediment and turbulence. A combination of operational features makes this facility unique. These include: a steep slope (variable up to 11%), large scale (20m long, 2m wide, and 1.2m deep), and a computer controlled flow, sediment system, and instrumentation system. The maximum water discharge is 1.4 m3/s (or 50 cfs). Design Requirements 1. The sediment trap will trap sediment that is traveling down the bed of the flume (called the bed load). It will not trap the sediment that is suspended in the moving water (called suspended sediment). The bed load sediment will range in size from less than 1 mm to 70 mm. The maximum mass flow rate of sediment will be 30 tons per hour. 2. The system must provide a continuous record of the weight of the sediment that is accumulating in the trap. The accuracy of the weight record should be approximately 0.1 N. The record may be interrupted for brief time periods (less than five seconds) while the weighing device is being emptied. 3. The trap will fill with sediment as the flume continues to run. The system must have a device to transport the sediment from the trap to a waste bin in the alley behind the laboratory. Existing Design Concept The St Anthony Falls Lab at the University of Minnesota has developed a sediment trap concept that is in use at a few flumes (that are different in size from the CERSL flume) around the U.S. It involves a rotating drum that is suspended by load cells. This looks like the best concept that I have seen - but we need a design team to adapt the concept to the CERSL flume, to perform the detailed design work, and implement the trap into the flume. Timeline: Shortly after starting the project an overview timeline was developed. This timeline was to help the team see the big picture as well as provide deadlines throughout the year. The timeline called for initial design work to be complete by the end of the semester, with final design selection, design and fabrication to come in the spring. Trips: Over the course of the project trips to Boise and Minneapolis became necessary. The purpose of each of these trips was to obtain more knowledge of specifications, to determine certain dimensions of the facility and flume, learn more about the flume/trap interface, among other things. Boise In September and again in March members of the Mainstream Design Team visited Boise to look over the flume site. Time was spent taking measurements, pictures and otherwise climbing all over the flume. This trip was necessary due to the large scale of this project. We would be needing to design many different components. It was important for the team to visualize just how each piece would interface with the flume, building structure and each other. The trip was a good way to kick start the brainstorming process and helped with the generation of ideas.. Sadly the holding tank was drained and we did not get to test the flume's water slide potential. Click here to see photos from this trip. Minneapolis The St. Anthony Falls Lab run by the University of Minnesota in Minneapolis has a sediment trap similar to the one designed in this project. In January team member Nathan Barrett went to Minneapolis to tour their facility and learn as much about the mechanics of their setup as he could to aid the development of our flume. Of particular help was their sediment catchment system, weighing/drum setup and their pumping system. Their flume actually has five sediment traps running side by side instead of just one. This is so they can measure more of a sediment movement profile in their experiments. Photos can be found here. Functional Model: The purpose of the functional model is to show the various systems of the flume their inputs and outputs. Four major components were identified as the flume, the sediment feeder, the sediment trap and the holding tank (sump). Three input/output categories examined are the energy, materials and input/output. Also, the two subsystems of interest, the flume and the sediment trap, have several of the needs added in. This allows us to link each need to the component and ultimately to link the inputs directly to each need. Specifications: All work up to this point has been done towards the goal of compiling a complete list of specifications. The project proposal we were given listed a few major requirements. These were more general ones pertaining to the kinds of research experiments to be preformed. The trips to Boise and Minnesota revealed more specifications that were not immediately apparent. Dozens of questions were answered to help give our design ideas some practical constraints. Breaking the setup into a function model further refined our project by mapping out the needs for each component. The end result is the list of project specifications given here.

Mainstream

Sediment Trap

University Of Idaho Senior Design Project for the Center for Ecohydraulics Research

Objective

Design, fabricate, and test a sediment trap system capable of trapping and weighing sediment that is traveling down the bed of a large flume. The sediment must then be removed from the trap and transported to a waste bin located in the alley behind the laboratory.

Background

The Center for Ecohydraulics Research (CER) is located in the Idaho Water Center (IWC) in downtown Boise. The Center for Ecohydraulics Research Stream Laboratory (CERSL) is a 2500 square foot lab located on the first floor of the IWC. The CERSL features a high gradient sediment flume designed in close collaboration with state and federal agencies and several of the major research laboratories in academia. The facility has been carefully designed to fill a current void in laboratory facilities to study the interaction of sediment and turbulence. A combination of operational features makes this facility unique. These include: a steep slope (variable up to 11%), large scale (20m long, 2m wide, and 1.2m deep), and a computer controlled flow, sediment system, and instrumentation system. The maximum water discharge is 1.4 m3/s (or 50 cfs).

Design Requirements

1. The sediment trap will trap sediment that is traveling down the bed of the flume (called the bed load). It will not trap the sediment that is suspended in the moving water (called suspended sediment). The bed load sediment will range in size from less than 1 mm to 70 mm. The maximum mass flow rate of sediment will be 30 tons per hour.

2. The system must provide a continuous record of the weight of the sediment that is accumulating in the trap. The accuracy of the weight record should be approximately 0.1 N. The record may be interrupted for brief time periods (less than five seconds) while the weighing device is being emptied.

3. The trap will fill with sediment as the flume continues to run. The system must have a device to transport the sediment from the trap to a waste bin in the alley behind the laboratory.

Existing Design Concept

The St Anthony Falls Lab at the University of Minnesota has developed a sediment trap concept that is in use at a few flumes (that are different in size from the CERSL flume) around the U.S. It involves a rotating drum that is suspended by load cells. This looks like the best concept that I have seen - but we need a design team to adapt the concept to the CERSL flume, to perform the detailed design work, and implement the trap into the flume.

Timeline:

Shortly after starting the project an overview timeline was developed. This timeline was to help the team see the big picture as well as provide deadlines throughout the year. The timeline called for initial design work to be complete by the end of the semester, with final design selection, design and fabrication to come in the spring.

Trips:

Over the course of the project trips to Boise and Minneapolis became necessary. The purpose of each of these trips was to obtain more knowledge of specifications, to determine certain dimensions of the facility and flume, learn more about the flume/trap interface, among other things.

Boise

In September and again in March members of the Mainstream Design Team visited Boise to look over the flume site. Time was spent taking measurements, pictures and otherwise climbing all over the flume. This trip was necessary due to the large scale of this project. We would be needing to design many different components. It was important for the team to visualize just how each piece would interface with the flume, building structure and each other. The trip was a good way to kick start the brainstorming process and helped with the generation of ideas.. Sadly the holding tank was drained and we did not get to test the flume's water slide potential. Click here to see photos from this trip.

Minneapolis

The St. Anthony Falls Lab run by the University of Minnesota in Minneapolis has a sediment trap similar to the one designed in this project. In January team member Nathan Barrett went to Minneapolis to tour their facility and learn as much about the mechanics of their setup as he could to aid the development of our flume. Of particular help was their sediment catchment system, weighing/drum setup and their pumping system. Their flume actually has five sediment traps running side by side instead of just one. This is so they can measure more of a sediment movement profile in their experiments. Photos can be found here.

Functional Model:

The purpose of the functional model is to show the various systems of the flume their inputs and outputs. Four major components were identified as the flume, the sediment feeder, the sediment trap and the holding tank (sump). Three input/output categories examined are the energy, materials and input/output. Also, the two subsystems of interest, the flume and the sediment trap, have several of the needs added in. This allows us to link each need to the component and ultimately to link the inputs directly to each need.

Specifications:

All work up to this point has been done towards the goal of compiling a complete list of specifications. The project proposal we were given listed a few major requirements. These were more general ones pertaining to the kinds of research experiments to be preformed. The trips to Boise and Minnesota revealed more specifications that were not immediately apparent. Dozens of questions were answered to help give our design ideas some practical constraints. Breaking the setup into a function model further refined our project by mapping out the needs for each component. The end result is the list of project specifications given here.

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