Predicting Flow Through the Causeway of the Great Salt Lake Using Hydrodynamic Simulations and Artificial Neural Networks

At the Great Salt Lake, the northern and southern portions of the lake are divided by an east-to-west causeway that disrupts natural lake currents and significantly increases salt concentrations in the norther portion. To support management efforts to address rising environmental and economic concerns, the causeway was recently modified to include a new breach that typically exhibits a strong density-driven bidirectional flow pattern. To obtain much needed insights into the hydraulic performance of this hydraulic structure and the exchange between the two sections of the lake, a field campaign coupled with computational fluid dynamics (CFD) modeling and an artificial neural network (ANN) model were undertaken

Labyrinth Weirs

Labyrinth weirs are often a favorable design option to regulate upstream water elevations and increase flow capacity; nevertheless, it can be difficult to engineer an optimal design due to the complex flow characteristics and the many geometric design variables of labyrinth weirs. This study was conducted to improve labyrinth weir design and analyses techniques using physical-model-based data sets from this and previous studies and by compiling published design methodologies and labyrinth weir information. A method for the hydraulic design and analyses of labyrinth weirs is presented. Discharge coefficient data for quarter-round and half-round labyrinth weirs are offered for sidewall angles of 6° to 35°. Cycle efficiency is also introduced to aid in sidewall angle selection. Parameters and hydraulic conditions that affect flow performance are discussed. The validity of this method is presented by comparing predicted results to data from previously published labyrinth weir studies. A standard geometric design layout for arced labyrinth weirs is presented. Insights and comparisons in hydraulic performance of half-round, trapezoidal, 6° and 12° sidewall angles, labyrinth weir spillways located in a reservoir with the following orientations are presented: Normal, Inverse, Projecting, Flush, Rounded Inlet, and Arced cycle configuration. Discharge coefficients and rating curves as a function of HT/P are offered. Finally, approaching flow conditions and geometric similitude are discussed; hydraulic design tools are recommended to be used in conjunction with the hydraulic design and analysis method. Nappe aeration conditions for trapezoidal labyrinth weirs on a horizontal apron with quarter- and half-round crests (sidewall angles of 6° to 35°) are presented as a design tool. This includes specified HT/P ranges, associated hydraulic behaviors, and nappe instability phenomena. The effects of artificial aeration (a vented nappe) and aeration devices (vents and nappe breakers) on discharge capacity are also presented. Nappe interference for labyrinth weirs is defined; the effects of nappe interference on the discharge capacity of a labyrinth weir cycle are discussed, including the parameterization of nappe interference regions to be used in labyrinth weir design. Finally, the applicability of techniques developed for quantifying nappe interference of sharp-crested corner weirs is examined

A Laboratory Study of Streambed Stability in Bottomless Culverts

Traditional culvert designs, in many cases, have become habitat barriers to aquatic animal species. In response, environmentally sensitive culvert designs have been developed to function as ecological bridges. Bottomless and buried invert culverts are examples of such designs and are commonly used for fish passage. Additional design guidance specific to streambed stability in buried-invert or bottomless culverts under high flow events is needed. This study investigated incipient motion conditions for four substrate materials in a 2-ft (0.61-m) diameter circular bottomless arch culvert and in a 1-ft (0.30-m) wide rectangular flume in a laboratory setting. General scour of the streambed within the bottomless arch culvert was also investigated under partially pressurized and non-pressurized flow conditions. This thesis discusses the experimental methods used to determine incipient motion conditions and analyses of incipient motion prediction methods. This thesis also presents the experimental results obtained from both test facilities with the results of other published incipient motion studies on gravel streambeds. Finally, the prediction efficiency of eight stone sizing methods (open channel and culvert application) applied to the experimental results was analyzed, which may be useful for determining stable stone diameters to be used as riprap in simulated streambeds through bottomless culverts

Driftwood Accumulation and Passage at V- and I-Rock Weirs in Mountain Streams

The transport and accumulation of driftwood, large wood, or large woody debris (LWD) in mountain streams is a natural part of catchment health and river connectivity. At hydraulic structures, the presence of driftwood has impacts on total discharge and up-stream energy. Driftwood has been studied at a variety of spillways and weir types; however, little is known about its interaction at rock weirs. This study seeks to determine what factors affect the transport of driftwood and potential upstream impacts of driftwood accumulations at rock weirs through field-informed scaled model testing. Observations of driftwood at rock weirs located on the Blacksmith Fork River, a mountain stream located in Utah, USA, were used to replicate driftwood dynamics in V- and I-shaped rock weirs in a large flume. The river response to rock weirs on the cor-responding section of the Blacksmith Fork River was also investi-gated using historic aerial imagery and field data. Approaches to driftwood management typically prioritize either natural processes or hydraulic structure safety and flow conveyance. A new hybrid approach should consider both aspects for rock weirs in mountain streams

CFD Model of the Density-Driven Bidirectional Flows through the West Crack Breach in the Great Salt Lake Causeway

Stratified flows and the resulting density-driven currents occur in the natural environment and commonly in saline lakes. In the Great Salt Lake, Utah, USA, the northern and southern portions of the lake are divided by an east-to-west railroad causeway that disrupts natural lake currents and significantly increases salt concentrations in the northern section. To support management efforts focused on addressing rising environmental and economic concerns associated with varied saltwater densities throughout the lake, the causeway was recently modified to include a new breach. The purpose of this new breach is to enhance salt exchange between the northern and southern sections of the lake. Since construction, it typically exhibits a strong density-driven bidirectional flow pattern, but estimating flows and salt exchange has proven to be difficult. To obtain much needed insights into the ability of this hydraulic structure to exchange water and salt between the two sections of the lake, a field campaign coupled with CFD modeling was undertaken. Results from this study indicate that the vertical velocity profile in the breach is sensitive to density differences between flow layers along with breach geometry and water surface elevations. The CFD model was able to accurately represent the bidirectional flows through the breach and provides for improved estimates of water and salt exchanges between the north and south sections of the lake

Educating Medical Students in Laboratory Medicine A Proposed Curriculum

As the 100th anniversary of the Flexner report nears, medical student education is being reviewed at many levels One area of concern, expressed in recent reports from some national health care organizations is the adequacy of training in the discipline of laboratory medicine (also termed clinical pathology) The Academy of Clinical Laboratory Physicians and Scientists is appointed an ad hoc committee to review this topic and to develop a suggested curriculum, which was subsequently forwarded to the entire membership for review The proposed medical student laboratory medicine curriculum defines goals and objectives for training, provides guidelines for instructional methods, and gives examples of how outcomes can be assessed. This curriculum is presented as a potentially helpful outline for use by medical school faculty and curriculum committees