published_or_final_version / Physics / Master / Master of Philosophy

This dissertation examines how turbidity currents interact with submarine channels. Turbidity currents display exaggerated super-elevation at the outer banks of channel bends, because they have low excess densities relative to the ambient sea-water. Low-velocity zones form where flows separate from the inner banks. In a high-resolution seismic volume, I mapped 226 inclined surfaces associated with bank-attached bars in 16 channel bends of 2 buried sinuous channels. Position and geometries of bars indicate construction from suspended sediment in flow separation zones. Concave-bank benches, first identified in rivers where they are built from fully-suspended sediment deposited within flow separation zones in channel bends, comprise approximately 19% of this dataset. Bars have high median slopes (10°-11°) and occupy less than 30% of channel width. Associated channels migrated a median distance of less than 70% of the channel width and incised 20-30% of the channel depth. These bars are therefore interpreted to have formed during sediment bypass or weak erosion. I have analyzed the sedimentology and stratigraphy of a well-exposed channel complex, in the Permian Brushy Canyon Formation, west Texas. A steeply-inclined set of fine-grained sandstone beds (median dip=10°) at the margin of the channel complex is interpreted as deposits of a bank-attached bar. Beds are characterized by sub- to super-critically climbing ripple-lamination, planar stratification and trough cross-stratification. Paleo-transport directions are at high angles, 20-120°, to the dip azimuths of interpreted bar surfaces. Geometries of bounding surfaces, sedimentation styles and grain-size data were used to construct a facies model for suspension-dominated, bank-attached bars, built within flow-separation zones in submarine channels. I designed physical experiments to examine how erosional turbidity currents evolve channel- bend topography. Time-lapse bathymetry maps capture the evolution of raised benches tied to sedimentation within flow separation zones and erosion outside of separation zones. Erosional currents showed sensitivity to local conditions. The pattern of erosion was connected to roughness elements such as bend curvature and scours on the bed. Turbidity current run-up at the outside of bends produced a greater aerial extent of side-wall erosion than is commonly seen in incisional rivers.

Not available / text

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

No description available.

No description available.

The technical feasibility of ohmic heating was evaluated for viscous liquids in static ohmic heating cells in three stages. First, electrical conductivities and time/temperature profiles were measured and compared for selected hydrocolloids (carrageenan, gelatin, pectin, starch and xanthan) in water at various concentrations (1--6%). Of the thickening agents examined, carrageenan gave the highest value for electrical conductivity and the shortest time to raise the temperature from 20 to 100°C. It was followed by xanthan. Pectin and gelatin samples were found to exhibit lower, but similar electrical conductivities and heating profiles. Starch samples had the lowest electrical conductivity and the temperature of starch solutions never exceeded 62°C within the specified time limit of 10000 s. / In the second stage, the effect of salt and acid concentration was evaluated on electrical conductivities and time/temperature profiles of the above selected hydrocolloids in water solutions at a concentration necessary to achieve a similar apparent viscosity of 0.2 Pa.s at 300 s-1 and 20°C (carrageenan 1.7%, pectin 2.5%, starch 4.3% and xanthan 2%). / In the third stage, measurements of electrical conductivities, time/temperature and heating rate profiles were performed applying six voltage gradients (5.26, 7.14, 13.16, 17.86, 21.05 and 25 V/cm), with two electrode cross-sectional surface areas (19.84 and 37.95 cm2) and the electrodes separated at three specific distances (10.05, 14.33 and 20.01 cm) at 150 V. Applied voltage gradients had a major effect on temperature and heating rate profiles but no effect on electrical conductivities. / Rheological properties of carrageenan, pectin, starch and xanthan solutions were investigated at various temperatures (20--80°C) and concentrations (carrageenan 1.5, 1.7 and 1.9%; pectin 2.3, 2.5 and 2.7%; starch 3.8, 4 and 4.2%; xanthan 1.6, 1.8 and 2%) in the presence of 1% salt. Both temperature and concentration influenced the rheological properties of solutions. / Finally, electrical conductivity measurements and rheological properties of starch at 4% and 1% salt were used as input to evaluate a theoretical model for the electrical, thermal and flow behaviour in a continuous ohmic heating unit. (Abstract shortened by UMI.)

No description available.

No description available.