Institution: Youngstown state University
Proposal No: 1102088
The objective of this EAGER proposal is to demonstrate the applicability of in-situ particle image velocimetry (PIV) technology to addressing fluid mechanics questions that are difficult to answer in the laboratory. This applicability will be demonstrated by linking eddy composition to fish habitat selection. Despite the ubiquity and importance of turbulence in the fluvial environment, accurate measures of turbulent eddy composition (eddy diameter, vorticity, and orientation) in rivers are lacking. In-situ PIV extends laboratory particle image velocimetry to the field by using synchronized portable laser and imaging systems. The result is a temporal series of two-dimensional vector fields that can then be used to describe the size, orientation, distribution, and rotational strength of eddies in a river. These turbulent eddy metrics will be collected at locations where brown trout are observed station holding in a river. The results will, for the first time, describe the eddy characteristics of habitat selected by brown trout. The eddy characteristics of trout habitat will be compared to regions not occupied by the fish in order to also describe the habitat the fish are actively choosing against. The benefits of this project will be: (1) demonstration of the applicability of a new technology to fluvial research, (2) increased understanding of the interaction between turbulence and fish habitat selection, and (3) improved stream restoration designs that increase biodiversity. The proposed work will provide researchers with a novel method for understanding fluvial processes. While the specific process to be investigated is fish habitat selection, the demonstrated method will be applicable to researchers interested in fields as diverse as nutrient mixing, sediment transport, and turbulence closure algorithms. This research will be conducted by researchers from Youngstown State University, a primarily undergraduate institution (PUI), who include the P.I., one undergraduate engineering student, one undergraduate ecology student, and one Youngstown City high school student. In addition to the objectives outlined above, this research will expose two undergraduate and one high school student to interdisciplinary research opportunities in STEM fields.
Bruce Hamilton Program Director Environmental Sustainability 10/16/10
The objective of this EAGER study was to demonstrate the applicability of in-situ PIV technology to answer questions that are difficult to reproduce in the laboratory. To achieve this objective the in-situ PIV system was deployed in Carp Creek and Douglass Lake of northern Michigan during the months of June and July 2011. The turbulence in microhabitat regions such as sand dunes, scour holes, log jams, surf zones, and boat docks were investigated. All of the data were collected on the University of Michigan’s Biological Station property and analysis is ongoing. During the data collection stage two major challenges were identified and overcome. PIV tracks ambient particles in the flow. In the laboratory environment small (diameters on the order of 10s of microns) neutrally buoyant highly reflective particles such as glass beads or titanium dioxide are added to the flow. In many field situations the ambient particles in the stream or lake are insufficient to act as tracer particles and a supplemental tracer particle is needed. Using titanium dioxide or glass beads was determined to be both practically and ecologically undesirable. Due to the fact that the volume of water associated with a given river or lake is large compared to most laboratory experiments our calculations showed that the mass of particles used as a tracer over the course of the month-long study would be on the order of hundreds to thousands of kilograms placing the cost out of reach for this demonstration project. An ideal particulate for in-situ PIV study should have little impact on the host ecosystem, be sufficiently inexpensive for the project, be neutrally buoyant, have a small diameter, and exhibit a high reflectivity. Prior to the field event, students conducted reflectivity and terminal velocity experiments on multiple particulate materials. The materials tested included chalk, bone meal, corn starch, flour, ground cereal, sugar crystals, silica sand, and ground rice. These materials were compared against the reflectivity and terminal velocity of the glass beads and titanium dioxide used in the laboratory. The results of these tests indicated that ground rice had the highest reflectivity with lowest settling velocity of the materials tested. Two-dimensional PIV uses a laser sheet to illuminate particles in a plane. In order to avoid tracking particles that are outside of this plane background light pollution needs to be minimized. In the laboratory this is accomplished by turning off lights in the laboratory during data collection. In previous in-situ PIV demonstrations data were either collected at night or at large ocean depths. While collecting data at night in streams and lakes remains a possibility, working at night is less efficient and safe than during the day. For this reason a crude three step field method was developed to reduce ambient lighting in order to collect in-situ PIV during the day. The turbulent flow around select scour holes, woody debris jams, algal mats, within the road crossing culvert barrel, and above sand dunes was collected using the in-situ PIV in order to compare the turbulent habitat available to the habitat selected. In addition to data collected in Carp Creek two data sets were collected in Douglass Lake around a boat dock and in the surf zone to demonstrate the system’s additional applicability in wave dominated environments. The data collected are being processed using JPIV software which was created and freely distributed by Peter Vennemann. This software converts the images collected in the field to velocity vector and vorticity scalar files. A MATLAB program is being written to identify eddies and calculate the circulation of each eddy. This program and the analysis of the data files are being conducted under a university grant that is supporting a graduate student’s salary. While the analyses are ongoing the initial findings have been presented at the American Society of Civil Engineering Environmental Water Resources Institute’s 2012 Congress in Albuquerque New Mexico.
