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Plate Mount H-Bar Mount Peristaltic Pump CMA & UCSD Team 14

Ultrasonic Signals Sent by Transducers

Background

Groundwater aquifers are at risk of contamination via man-made pollutants and natural occurring chemicals. Once contaminated, the flow of the aquifers can transport the pollutants over a widespread area, with the possibility of reaching other sources or bodies of water. As a result, these groundwater plumes are a potential threat to the surrounding environment. This project was formed to detect and monitor these plumes.ObjectiveThe objectives of this project are the detection and monitoring the groundwater plumes, leading up to eventual evaluation and quantification of the contaminant flow rates. To this end, the Coastal Monitoring Associates team has built the Ultraseep system, a seepage meter for direct measurement of groundwater plumes at their site of origin. The Ultraseep system utilizes a set of ultrasonic flow transducers. The transducers send ultrasonic signals to one another, using time difference between them is measured to calculate the flow velocity. These ultrasonic flow transducers are the key to detecting and evaluating ground water seepage. The Ultrasonic Seepage Meter team will aid these goals by forming a procedure to calibrate and optimize the Fluxus F601 and ADM7407 model flow meters to accurately measure flows on the magnitude of ml/min. This entails finding the optimal pipe material and setup for the transducers. The team will also create mounting devices that will allow the flow transducers to be placed easily and accurately on the final pipe setup. Finally, the team will provide an evaluation on retrofitting the new flow meters for the housing of the Ultraseep system.Final DesignThe final design of the project consisted of the test rig, mounting devices, and housing evaluation. The test rig was a closed loop flow system composed of a peristaltic pump, stainless steel tubes, and flexible tygon piping. The test rig allowed both sets of transducers to run on the same flow condition, providing a side by side analysis of their performance in real time. It was used to find the optimal configuration for the transducer setup. The mounting devices were created to easily place the transducers onto the Ultraseep system after the optimal configuration was discovered. The mounting devices kept the transducers from rotating or moving laterally while on the pipe. The team designed two versions: the hinged mounting device, and the velcro mounting device. The hinged version utilized a hinge to clamp onto the pipe and had an open slot for the transducers. The transducers were set in place with screws. In the velcro version, velcro was attached to half tube of plastic and the transducers themselves. The transducers were simply attached to the plastic via the velcro to hold the system in place.

The housing evaluation showed that the current Ultraseep system would have to be remodeled to fit the flow meter controllers.

Dual Test Rig Setup

The velcro mounting device was able to easily switch between pipes, but it had trouble constraining the transducers onto the pipes themselves. As such, the signal strength attained by the transducers suffered. However, this mounting device was sufficient to run tests on the effects of low signal strength for the flow meters. The housing evaluation proved that the current Ultraseep system was unable to contain the flow meters in its current form. As a result, CMA was advised to increase the width of their current housing to make space for the setup.The Executive Summary of the project can be found here.

Performance ResultsThe designed components were able to meet the project's primary objectives: the calibration and optimization of the flow meters. The test rig was able to provide suitable simulations of low-flow conditions for the transducers to measure. The rig allowed both flows to test the same flow conditions simultaneously, and allowed pipes of varying diameters to be placed throughout it. In addition to that, the rig allowed the distance between the transducers to be easily adjusted to find the optimal configuration. The test rig conditions helped to show that the optimal distance between the transducers was about 13.3 cm (5.25 in) at a setting of 24 bounces. The mounting devices were able to constrain the transducers upon the pipes efficiently. The hinged mounting device clamped the pipe down and kept it from rotating. It had the ability to easily switch transducers out, and it was also adjustable for distance. The mounting device did not impede the measurements of the flow meters, so it was considered to be an acceptable solution for the design criterion.

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