Browsing by Author "Christopher, Richard"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    The Physical Model Study of the Bond Falls Emergency Spillway
    (2008-05) Christopher, Richard; Mohseni, Omid
  • Thumbnail Image
    Item
    Physical Model Study of the Intake Structure of the Prairie Du Sac Hydroelectric Project
    (St. Anthony Falls Laboratory, 2006-03) Mohseni, Omid; Leuker, Matthew; Christopher, Richard; Stefan, Heinz G.
    A physical model study of the intake structure of the Prairie du Sac Hydroelectric Project was conducted to assess the distribution of velocities across the intake as an aid in identifying possible modifications to meet resource agency fish protection criteria. The model was built at a scale of 1 to 14. In the model study, approach velocity characteristics were evaluated for a new trash rack placed upstream of the intake structure replacing the existing trash rack inside the structure. Two modification scenarios were studied: a trash rack with 1.75-inch openings (68% opening ratio), and a trash rack with 1.0-inch openings (53% opening ratio). Flow velocities were measured at 40 locations upstream of the model trash rack, corresponding to points located approximately one foot upstream of the trash rack in the full-scale (prototype) structure. Flow velocity measurements were conducted under three flow conditions: 1300 cfs (representing typical flow through the project’s 3 larger generating units) 1000 cfs (representing typical flow through the project’s 5 smaller generating units), and 2170 cfs (representing maximum flow possible through the project’s largest generating unit). Under the 1300 cfs flow condition, the approach flow velocities did not exceed 1.1 and 1.2 fps with the 1.75- and 1.0-inch opening trash racks, respectively. The maximum through flow velocities for the 1300 cfs flow condition were estimated to be 1.9 and 2.4 fps, respectively.
  • Thumbnail Image
    Item
    Physical Model Study of the San Antonio River Lock System
    (St. Anthony Falls Laboratory, 2005-10) Mohseni, Omid; Christopher, Richard; Barnacle, Todd; Stefan, Heinz
    The San Antonio River Authority (SARA) initiated a project to extend tour boat navigation approximately 7,000 feet upstream on the San Antonio River. To make this section of the river navigable, a small dam and parallel lock system will be built to transfer vessels between lower pool elevation of 631.2 feet and upper pool elevation of 640.0 ft. The hydraulic locks must transfer tour boats quickly, efficiently, comfortably and safely using available river flow. A physical model study was required to verify and refine the operational suitability of the proposed side-port lock system. The model was constructed and studied at St. Anthony Falls Laboratory. The scope of the study was to build a physical model of one lock and its associated filling and emptying system and to test its operation on a scale model of the design vessel. The model was built at a scale of 1:8 and included a single lock chamber, a side-port gallery to convey water into and out of the lock chamber, and the upstream and downstream sluice gates. Two series of tests were conducted and at least one of the following parameters was modified during each test: The gate opening height, the gate opening duration, the gate opening as a function of time, the lock chamber floor level, and the loading of the vessel. For each test, headwater, tailwater, water surface level in the lock chamber and the opening rate of the sluice gate were recorded. The performance of the lock chamber was determined qualitatively by inspection of the vessel reaction and the flow patterns inside the gallery and the lock chamber. The second and more extensive series of tests were videotaped.
  • Thumbnail Image
    Item
    Testing a Single Lateral of an Underdrain System
    (St. Anthony Falls Laboratory, 2006-10) Mohseni, Omid; Christopher, Richard
    To evaluate the performance of the laterals of an underdrain system manufactured by Johnson Screens, a test-stand basin was built at St. Anthony Falls Laboratory. Two laterals were placed in the basin of which one was a blind lateral, i.e. with no orifice holes, for the leakage test. The laterals were 8-inch conduits with 9.25-inch diameter vee-wire wrap around them. Eleven series of tests were conducted on the laterals, of which five test series were to assess the hydraulic performance under the backwash mode, three test series to assess the hydraulic performance under the filter mode, and three test series to determine the amount of leakage. Under the backwash mode, the flow rate from every two rings of orifices was measured using a flow-capturing apparatus. The flow rate varied from 53 GPM at the upstream point to 64 GPM at the downstream point. Two tests series were also conducted and flow velocities around the lateral were measured to determine the turbulence intensity along the lateral. The average turbulence intensities estimated at the upstream, downstream and the midpoint of the lateral were comparable. Under the filter mode, the flow rate from the orifice rings could not be measured, therefore, only the approach flow velocities were measured. The average turbulence intensities estimated at the upstream, downstream and the midpoint of the lateral were again comparable. For the leakage test, the amount of leakage exceeded the threshold during the first two series. Subsequently, the tested lateral was modified and improved by the Johnson Screens crew members. The final product was tested and the amount of leakage under 35 psi pressure with a duration of four minutes decreased to 5 GPM.
  • Thumbnail Image
    Item
    Testing an Underdrain System under Backwash Flow Conditions for the Chaparral Water Treatment Plant
    (St. Anthony Falls Laboratory, 2005-03) Ellis, Chris; Christopher, Richard; Mohseni, Omid
    Johnsons Screens was required to test its underdrain system under backwash flow conditions to assess the uniformity of flow discharge throughout the manifold system. To test the system, a basin was built in St. Anthony Falls Laboratory and the underdrain system components were provided and installed by Johnsons Screens. To assess the uniformity of flow of the manifold system, a measurement technique was developed to determine the flow at a number of locations at design flows. The technique was a flow-capturing apparatus with an open-topped tank, two tubes, a hose and a pump. Using this apparatus, the flow was captured over a period of time and weighed to determine the flow rate from each triplet of orifices. The system error under high system flow rate (about 19 cfs) was less than 0.7%. Six locations were determined by Johnsons Screens for the testing. At each location, a total of five measurements were taken and averaged under the high system flow rate (about 19 cfs) and an additional five measurements for the low system flow rate (about 4.4 cfs). The results of the measurements showed that the deviation of the flow measurements from the mean were within ±5% under high system flows and ±7% under low system flows.