Paper No. 6
Presentation Time: 8:00 AM-12:00 PM
EXPERIMENTAL RESULTS WITHIN A RE-CIRCULATING FLUME CONCERNING THE RELATIONSHIP BETWEEN WATER TEMPERATURE AND THE GENERATION OF BEDFORMS
Viscosity and density are important factors controlling fluid deformation and the transmission of forces from fluids to solids during entrainment, transportation, and deposition of sedimentary particles. For water, density and viscosity vary with temperature, which ranges from ~25° to 0°C in mid to high-latitude streams. Over this range, dynamic viscosity increases from 0.000891 to 0.001792 kg/ms, and density changes from 997.13 to 999.82 kg/m3. Using a 1m x 1m x 7m re-circulating flume, containing nine tons of medium grained quartz sand, we conducted a series of experiments to record the relationships between changing water temperatures, Reynolds numbers (expression of the relative importance of inertial and viscous forces in a fluid flow), Froude numbers (ratio of the inertial to gravity forces in a fluid), and bedforms. Filtered water drawn from Lake Michigan was used, which from October to February changed from 21° to 3.3°C. During experimental runs, increases in velocity resulted in progressive changes in the configuration of the bed from no movement, to 2-D ripples, to 3-D ripples, to 2-D dunes, to 3-D dunes, to plane bed, and finally to antidunes. Our findings suggest that for a given water depth, the type of bedform generated was dependent on specific Reynolds numbers. Because decreasing fluid temperatures result in increasing viscosities, and therefore a decrease in turbulence, slightly higher velocities and Froude numbers are required to produce specific bedforms at lower water temperatures.