Thesis (M.S.)--Ohio University, August, 1995. / Title from PDF t.p.

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2008. / Includes bibliographical references (p. 39-43).

Many oceanographers have postulated that internal wave form inversion would take place at the turning point where the thickness of the upper and bottom layer are equal in a stratified two-layer fluid system. This implies that an internal wave of depression may convert into elevation as the wave propagates over a continental margin comprising continental slope and shelf. Laboratory experiments were conducted on the propagation of a depression ISW over a trapezoidal obstacle in a stratified two-layer fresh/brine water system in a steel framed wave tank of 12m long with cross section of 0.7m high by 0.5m wide. The relative difference in water depth between the upper and lower layer and the initial ISW amplitude were the main controlling parameters, among others. The water depth in the stratified two-layer system on the horizontal plateau of the trapezoid obstacle fell into one of the following case: (1) the upper layer larger than lower (H1>¢Ö2'); or (2) equal depth in the upper and lower layer (H1=¢Ö2'); or (3) the upper layer less than lower layer (H1<¢Ö2'). In addition of the depth ratio, the difference in the length of the horizontal plateau and the thickness of the phycnocline above if were also parameters affecting the outcome of the experiments. In these experiments, three different type of the height and length of the trapezoidal obstacle were used, including long (4.8x0.37m), medium (1x0.35m) and short (0.5x0.35m) types. A full account on the characteristics of the ISW evolution observed during this experimental study is presented in this thesis. As an ISW propagated on the fronting slope, were run-down, vortex motion, internal hydraulic jump (IHJ) and run-up were occurred. Once the wave passed the turning point (where the depth of upper and lower layer equal), the wave form became elevation on the plateau above the obstacle. Based on the laboratory data available, the effect on internal wave evolution can be evaluated by the relative fluid thickness (H1/¢Ö2') on the plateau. The outcome can be classified into three categories: (1) H1>¢Ö2', the relative layer thickness on the plateau unfits for depression ISW propagation and waveform behaves like elevation type; (2) H1=¢Ö2', wave boluses containing mixed fluid propagating on the plateau after breaking on the slope; (3) H1<¢Ö2', ISW propagated over trapezoidal obstacle subjected to shoaling and viscosity effect, without change in waveform. As a depression ISW propagated over the variable length of the plateau, another important factor affecting the intensity of the internal hydraulic jump was the water volume drawn from the plateau. In the case of long horizontal plateau, the interaction range was large, and the IHJ was strong. Consequently, the thickness of the increased which caused the IHJ to move upward along the fronting slope. However, the amplitude and phase speed of the resulting internal wave decreased as if propagated further.

Thesis (M.S. in Civil Engineering)--Washington State University. / Includes bibliographical references.

Low-head dams are known to be dangerous due to a recirculating current that, when formed, drowns recreationalists who become trapped in the current. Efforts to mitigate the hazard of low-head dams have led to the compilation of a database of low-head dams with proven fatalities. Additionally, flume-based experiments along with well-known hydraulic equations have been used to create a spreadsheet-based system for predicting the occurrence of the dangerous recirculating current, otherwise known as a submerged hydraulic jump. The premise of the spreadsheet is that if the normal depth calculated with the Mannings Equation for the downstream reach is between the conjugate depth and the flip depth associated with the hydraulic jump at the low-head dam, a submerged hydraulic jump will occur. This hypothesis was tested using 58 fatal incidents at 29 low-head dams across the United States. The algorithm output was also compared to conditions observed during 13 site visits to 6 non-fatal low-head dams in Utah. The predictions achieved 75% accuracy in predicting submerged hydraulic jumps using publicly available data and data collected using site visits. Flow-duration curves were then developed to determine the frequency of submerged hydraulic jumps at correctly predicted dams where fatalities occurred. These dangerous dams were calculated to have submerged hydraulic jumps for an average of 343 days per year. Modeled discharge using the GEO Global Water Sustainability Initiative and the National Water Model was compared with USGS gaged data and produced similar results for the correctly predicted dangerous dams. Due to sparse data, it is recommended to calibrate the spreadsheet approach using detailed data at a random sample of dams or by creating a new system for predicting dangerous low-head dams using a one dimensional or multidimensional hydraulic computer model.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22756号 / 工博第4755号 / 新制||工||1744(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 細田 尚, 教授 戸田 圭一, 准教授 音田 慎一郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Screens may be utilized efficiently for dissipating the energy of water. In this study, water flowing beneath a gate is used to simulate the flow downstream of a hydraulic structure and screens are used as an alternative mean for energy dissipation. Investigations are done conducting a series of experiments. The porosity, thickness, and the location of the screens are the major parameters together with the Froude number of the upstream flow. The scope of this thesis covers the situation where there is a pseudo-jump formation. The experiments covered a range of Froude numbers between 5 and 18, porosities between 20% and 60%, and location of the screen up to 100 times of the undisturbed upstream flow depth. The thicknesses of the screens used are in the order of the undisturbed upstream flow depth. The results show the importance of each parameter on the energy dissipating performance of the screens and the system. It is observed that screens dissipate more energy than a jump within the range covered in these studies.

No description available.

The majority of dams contain low-level outlet works, which typically consist of closed conduits that run through the dam, and are used to release water from the reservoir when the water level is below the level of the surface spillways. It is also used to flush the reservoir of sediments and to control the elevation of the reservoir. Low-level outlet works typically consist of a gate that controls the flow within a closed conduit that runs through the dam and an air vent that supplies air behind the gate. In the absence of properly designed air vents, negative pressures may develop downstream of the gate. These negative pressures could potentially lead to cavitation and vibration damage. Properly sized air vents help maintain the downstream air pressure at or near atmospheric pressure and/or provide air to absorb the energy generated by cavitation, reducing the potential for damage. The majority of research done on air vent sizing is for dams having large dam geometry, which consist of a pressurized conduit leading to a vertical slide gate that is followed by a discharge tunnel. The typical air vent design for these large dams uses the water flow rate and the Froude number measured at the vena contracta downstream of the gate. The low-level outlet works for small-to-medium-sized embankment dam geometries typically have an inclined slide gate, installed at the inlet on the upstream face of the dam slope, followed by an elbow that connects to a conduit that passes through the dam and discharges downstream. This type of outlet geometry does not produce the typical vena contracta. Consequently, the use of the Froude number, at the vena contracta , as a characteristic parameter for characterizing airflow demand is not practical. Recently a laboratory study was performed calculating the head-discharge characteristics of low-level outlets for small-to-medium sized dam geometries. In addition to validating some of the previous laboratory-scale air venting research, the objective of this study was field verification of air-demand/air vent sizing predicted by the laboratory-based method. The influence of conduit slope, air port location, and hydraulic jumps on air demand was also evaluated in the laboratory. The findings of this study can be found within this thesis.

The majority of dams contain low-level outlet works, which typically consist of closed conduits that run through the dam, and are used to release water from the reservoir when the water level is below the level of the surface spillways. It is also used to flush the reservoir of sediments and to control the elevation of the reservoir. Low-level outlet works typically consist of a gate that controls the flow within a closed conduit that runs through the dam and an air vent that supplies air behind the gate. In the absence of properly designed air vents, negative pressures may develop downstream of the gate. These negative pressures could potentially lead to cavitation and vibration damage. Properly sized air vents help maintain the downstream air pressure at or near atmospheric pressure and/or provide air to absorb the energy generated by cavitation, reducing the potential for damage. The majority of research done on air vent sizing is for dams having large dam geometry, which consist of a pressurized conduit leading to a vertical slide gate that is followed by a discharge tunnel. The typical air vent design for these large dams uses the water flow rate and the Froude number measured at the vena contracta downstream of the gate. The low-level outlet works for small-to-medium-sized embankment dam geometries typically have an inclined slide gate, installed at the inlet on the upstream face of the dam slope, followed by an elbow that connects to a conduit that passes through the dam and discharges downstream. This type of outlet geometry does not produce the typical vena contracta. Consequently, the use of the Froude number, at the vena contracta , as a characteristic parameter for characterizing airflow demand is not practical. Recently a laboratory study was performed calculating the head-discharge characteristics of low-level outlets for small-to-medium sized dam geometries. In addition to validating some of the previous laboratory-scale air venting research, the objective of this study was field verification of air-demand/air vent sizing predicted by the laboratory-based method. The influence of conduit slope, air port location, and hydraulic jumps on air demand was also evaluated in the laboratory. The findings of this study can be found within this thesis.