Gas Transfer in Diffused Bubble Plumes

The gas transfer in aeration systems is broken into two processes: gas transfer at the bubble interface and gas transfer at the water surface. Experiments were conducted to separate these two sources of dissolved gas. Oxygen absorption was measured in a laboratory tank with air being diffused through a porous diffuser and then with nitrogen gas being diffused. The combination of these experiments along with reformulation of the theoretical transfer equation permit separation of the gas transfer at the water surface and in the rising bubble plume. Estimates of the exchange coefficient for the plume and surface are given

Design of Pneumatic Diffuser System

During non-generation periods, leakage through the wicket gates of a hydroturbine often results in very poor quality water (low or zero dissolved oxygen) in the tailrace of the hydropower facility. Generally, the leakage rate is relatively small, usually about 5-10 cfs per turbine. A bottom-mounted diffuser system was designed based on laboratory-measured and manufacturer-supplied specifications about the gas transfer characteristics of the bubble plume generated by an 11- inch flexible head diffuser. The design criteria and the overall effectiveness of the system were evaluated in field tests at Lake Eufaula, Oklahoma. The analysis of field data is reported herein

Bay Springs Lake: Water-Quality Study: Hydraulic Laboratory Investigation

Source: https://erdc-library.erdc.dren.mil/jspui/Physical and mathematical models were used to investigate the mechanics of density-stratified flow within Bay Springs Lake as affected by inflow from the local drainage areas and the divide-cut canal, and to predict the temperature and dissolved oxygen (D. O.) regimes of the lake immediately upstream of the dam and in releases through the lock. The hydrodynamic phenomena in the lake were greatly influenced by the extremely dynamic nature of the operation of the Bay Springs project and the relatively large quantity of flow from the divide-cut canal. Operation of the lock indicated that a circulation of water within the hypolimnion should occur during certain times of the year. The lake is primarily affected by inflow from the divide-cut canal. Numerical simulations predicted satisfactory temperature and D.O. profiles at the dam. The relatively high withdrawal of the lock intakes, coupled with the large inflow from the divide- cut canal, indicates the proposed project will satisfy water-quality interests._x000D_ _x000D_ NOTE: This file is large. Allow your browser several minutes to download the file

Enhancement of Releases from a Stratified Impoundment by Localized Mixing, Okatibbee Lake, Mississippi

Source: https://erdc-library.erdc.dren.mil/jspui/Tests were conducted at Okatibbee Lake, Mississippi, to evaluate the effectiveness of localized mixing for enhancing the quality of low-level, low-flow releases from a stratified impoundment. A low-energy mechanical pump (Garton pump) that consisted of a submerged ventilating fan driven by a 1.12-kw electric motor was positioned immediately upstream of and above the low-level intake. Epilimnion water was forced toward the lake bottom where it was mixed with hypolimnion water and then released through the fixed low-level flood control outlet. The quality of this water mixture was an improvement over the quality of the water released without the pump operating. It was estimated that the epilimnion water comprised about 50 percent of the total release. Use of a Garton pump to induce localized mixing upstream of a fixed low-level flood control outlet was demonstrated to be an effective and economical means of improving the quality of low-flow releases from a stratified reservoir

Reaeration Tests, Outlet Works Beltzville Dam, Pohopoco Creek, Pennsylvania

Source: https://erdc-library.erdc.dren.mil/jspui/Prototype water-quality tests were conducted at Beltzville Dam during August 1976. The purposes of these tests were to : (a) determine the location and degree of reaeration of flow that occurred as it passed through the outlet works, (b) provide prototype data with which to evaluate the accuracy of the U.S. Army Engineer Water ways Experiment Station selective withdrawal numerical model, SELECT, and (c) supplement results of hydraulic prototype tests conducted at Beltzville Dam in May 1973. Twelve tests were conducted. Temperature and dissolved oxygen data (vertical profiles) were collected upstream of the dam, at seven stations within the outlet structure, and at one station in the downstream channel. The tests involved various flow rates and various outflow port elevations. The results of these prototype tests showed : (A.) the dissolved oxygen content of the release flows was approximately 90 to 95 percent of the saturation level regardless of the dissolved oxygen content of the flow entering the structure or the discharge, and major reaeration occurred within the outlet structure downstream of the water-quality gate; (B.) the predictions of the SELECT model were in close agreement with the observed data; and (C.) the hydraulic measurements were close to those of the 1973 tests

Scour Protection for Locks and Dams 2-10, Upper Mississippi River: Hydraulic Model Investigation

Source: https://erdc-library.erdc.dren.mil/jspui/A 1:70-scale physical model of a typical spillway section of the locks and dams on the Upper Mississippi River was used to determine the probable cause of the scour that has occurred at these projects. It was determined that single-gate operation on the spillways created hydraulic conditions conducive to scour. A 1:42-scale model was used to develop suitable riprap protection. Two gradations of fill material were found suitable and two gradations of riprap were adequate for protection downstream of the tainter gates and roller gates at these structures. The geometric layout of the riprap depended upon the slope of the scour hole to be repaired. Lock and Dam 2 was studied separately because of its unique stilling basin configuration and operation schedule. Riprap protection similar to the other projects was devised for Lock and Dam 2

Dickey-Lincoln School Lakes Hydrothermal Model Study: Hydaulic Model Investigation

Source: https://erdc-library.erdc.dren.mil/jspui/A one-dimensional, vertically stratified, thermal simulation model was developed for prediction of temperature within and downstream from Dickey-Lincoln School Lakes. Two physical hydraulic models were used to obtain an improved understanding and description of the hydrodynamic response of the lakes to pumped-storage hydropower. An undistorted, 1:200-scale model of the Dickey Lake intake structures and local topography was used to determine the steady-state selective withdrawal and pumpback flow characteristics for various conditions. A highly distorted-scale model (1:3600 horizontal, 1:180 vertical) was used to simulate the entire dual reservoir system and to determine the response to dynamic, unsteady-state, density stratified flow. Information from the two physical models was used to modify existing algorithms and to develop new algorithms for the mathematical model. The mathematical model allows simulation of the hydrodynamic and heat exchange characteristics so that the thermal regimes within and downstream from the two lakes can be determined for various hydrologic and meteorologic conditions and various pumped-storage hydropower operations