Mixing processes and hydraulic control in a highly stratified estuary
Thesis (Ph. D .)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | eng |
| Published: |
Massachusetts Institute of Technology
2005
|
| Subjects: | |
| Online Access: | http://hdl.handle.net/1721.1/16902 |
| _version_ | 1826214432477282304 |
|---|---|
| author | MacDonald, Daniel George, 1970- |
| author2 | W. Rockwell Geyer. |
| author_facet | W. Rockwell Geyer. MacDonald, Daniel George, 1970- |
| author_sort | MacDonald, Daniel George, 1970- |
| collection | MIT |
| description | Thesis (Ph. D .)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003. |
| first_indexed | 2024-09-23T16:05:16Z |
| format | Thesis |
| id | mit-1721.1/16902 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T16:05:16Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/169022019-04-12T21:50:49Z Mixing processes and hydraulic control in a highly stratified estuary MacDonald, Daniel George, 1970- W. Rockwell Geyer. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Civil and Environmental Engineering. Thesis (Ph. D .)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003. Includes bibliographical references (p. 207-214). This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. This thesis utilizes field data from the Fraser River Estuary, a highly stratified system located in southwestern British Columbia, Canada, to investigate the nature of mixing processes in a highly stratified environment, and to extend two-dimensional hydraulic theory to a three dimensional environment. During the late ebb, a stationary front exists at the Fraser mouth. Although densimetric Froude numbers in the vicinity of the front are supercritical in a frame of reference parallel to the local streamlines, the front itself is oriented such that the value of the Froude number is equal to the critical value of unity when taken in a frame of reference perpendicular to the front. This observation presents a robust extension of established two-dimensional, two-layer hydraulic theory to three dimensions, and implies similarity with trans-sonic flows, in that a Froude angle can be used to identify critical conditions in a manner similar to the Mach angle. Mixing processes were evaluated at the mouth during the late ebb using a control volume approach to isolate mean vertical entrainment processes from turbulent processes, and quantify the vertical turbulent salt and momentum fluxes. Observed turbulent dissipation rates are high, on the order of 10-3 m2s-3, with vertical entrainment velocities on the order of 2 x 10-3 m s' . Mixing efficiencies, expressed as flux Richardson numbers, are confined within a range from 0.15 to 0.2, at gradient Richardson number values between 0.2 and 0.25. (cont.) These results are consistent with previous laboratory studies, but represent energetic conditions that are several orders of magnitude higher. In the estuarine channel, the variability of mixing processes was investigated through the tidal cycle using control volume and overturn scale methods. Spatially, mixing was observed to be more intense near a width constriction on the order of 25%. Temporally, more dominant mixing was observed during ebbs, due to increases in both vertical shear and stratification. Mixing is active and important throughout the tidal cycle, and was found to be the dominant process responsible for removing salt from the estuarine channel during the ebb. by Daniel George MacDonald. Ph.D . 2005-05-19T15:13:24Z 2005-05-19T15:13:24Z 2003 2003 Thesis http://hdl.handle.net/1721.1/16902 52255415 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 214 p. 14325658 bytes 14325370 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Civil and Environmental Engineering. MacDonald, Daniel George, 1970- Mixing processes and hydraulic control in a highly stratified estuary |
| title | Mixing processes and hydraulic control in a highly stratified estuary |
| title_full | Mixing processes and hydraulic control in a highly stratified estuary |
| title_fullStr | Mixing processes and hydraulic control in a highly stratified estuary |
| title_full_unstemmed | Mixing processes and hydraulic control in a highly stratified estuary |
| title_short | Mixing processes and hydraulic control in a highly stratified estuary |
| title_sort | mixing processes and hydraulic control in a highly stratified estuary |
| topic | Civil and Environmental Engineering. |
| url | http://hdl.handle.net/1721.1/16902 |
| work_keys_str_mv | AT macdonalddanielgeorge1970 mixingprocessesandhydrauliccontrolinahighlystratifiedestuary |