A hydraulically undersized control structure could result in water overtopping a dam or channel banks. To increase hydraulic capacity and reduce flooding risk, nonlinear spillways are frequently replacing linear weirs. This study investigates four subjects to further knowledge for two types of nonlinear weir, the piano key and labyrinth. Weir submergence is a condition when the downstream water level of a weir exceeds the weir crest elevation, and can influence the head-discharge relationship of the structure. The effects of submergence on laboratory-scale piano key weir head-discharge relationships were evaluated experimentally and compared to published submergence data for linear and labyrinth weirs. For relatively low levels of submergence, the piano key weir requires less upstream head relative to the labyrinth weir (<6%). This increase in efficiency was reversed at higher levels. Staged labyrinth weirs feature multiple weir segments with different crest elevations, which confine base flows and/or satisfy downstream discharge requirements. Head-discharge relationships for various laboratory-scale staged labyrinth weir configurations were established. The accuracy of a head-discharge predictive technique based upon superposition and traditional labyrinth weir empirical data was evaluated, and found to be generally within ±5%. The influence of linear, labyrinth, and staged labyrinth weir head-discharge characteristics on the outflow hydrograph behavior was evaluated by numerically routing various flood discharges through a fictitious reservoir; peak outflow, maximum water surface elevation, and required detention volume data are presented for each weir alternative. A staged labyrinth weir can be an effective alternative for decreasing the peak outflow hydrograph for frequent events, while increasing discharge for higher return period storm events. Approach flow perpendicular to the labyrinth weir centerline axis may not be possible in all situations. The head-discharge characteristics of a laboratory-scale labyrinth weir were evaluated with three different approach flow angles (0°, 15°, and 45°). For approach flow angles up to 15°, no measurable loss in discharge efficiency occurred. The discharge efficiency reduced as much as 11% for the 45° approach angle case. While all data presented are specific to the weir configurations and geometries tested, these data can be beneficial to the general understanding of nonlinear weirs.

The present text, submitted to the University of Liège in fulfillment of the requirements for the degree of Docteur en Sciences de lIngénieur, aims at improving the understanding and description of air‐water interactions in transient flows. A particular emphasis is set on phenomena relevant in civil and environmental engineering, like rivers, pipes, and hydraulic structures. Theoretical results of this doctoral research may be summarized in two main propositions. First, I show that any mathematical model for free surface flows can be extended to pressurized flows. Second, the multiphase drift‐flux model is proven an adequate alternative to Navier‐ Stokes equations in civil and environmental engineering. These propositions underpin the development of original mathematical models and new computational codes (WOLF1D and WOLF IMPack). Validation and application on actual cases prove the efficiency of the new approach. Original concepts introduced in this thesis pave the way for further research on environmental flows, especially on the mathematical description of transport phenomena (pollutants, sediments) and heterogeneous interactions (vegetation, rough bed).

A SuperCritical Water-cooled Nuclear Reactor (SCWR) is a Generation IV concept currently being developed worldwide. Unique to this reactor type is the use of light-water coolant above its critical point. The current research presents a thermal-hydraulic analysis of a single fuel channel within a Pressure Tube (PT) - type SCWR with a single-reheat cycle. Since this reactor is in its early design phase many fuel-channel components are being investigated in various combinations. Analysis inputs are: steam cycle, Axial Heat Flux Profile (AHFP), fuel-bundle geometry, and thermophysical properties of reactor coolant, fuel sheath and fuel. Uniform and non-uniform AHFPs for average channel power were applied to a variety of alternative fuels (mixed oxide, thorium dioxide, uranium dicarbide, uranium nitride and uranium carbide) enclosed in an Inconel-600 43-element bundle. The results depict bulk-fluid, outer-sheath and fuel-centreline temperature profiles together with the Heat Transfer Coefficient (HTC) profiles along the heated length of fuel channel. The objective is to identify the best options in terms of fuel, sheath material and AHFPS in which the outer-sheath and fuel-centreline temperatures will be below the accepted temperature limits of 850°C and 1850°C respectively. The 43-element Inconel-600 fuel bundle is suitable for SCWR use as the sheath-temperature design limit of 850°C was maintained for all analyzed cases at average channel power. Thoria, UC2, UN and UC fuels for all AHFPs are acceptable since the maximum fuel-centreline temperature does not exceed the industry accepted limit of 1850°C. Conversely, the fuel-centreline temperature limit was exceeded for MOX at all AHFPs, and UO2 for both cosine and downstream-skewed cosine AHFPs. Therefore, fuel-bundle modifications are required for UO2 and MOX to be feasible nuclear fuels for SCWRs. / UOIT

A common problem encountered in mobile hydraulics is the desire to automate motion control functions in a restricted-cost and restricted-sensor environment. In this thesis a solution to this problem is presented. A velocity control scheme based on a novel single component pressure compensated ow controller was developed and evaluated. <p> The development of the controller involved solving several distinct technical challenges. First, a model reference control scheme was developed to provide control of the valve spool displacement for a particular electrohydraulic proportional valve. The control scheme had the effect of desensitizing the transient behaviour of the valve dynamics to changes in operating condition. Next, the pressure/flow relationship of the same valve was examined. A general approach for the mathematical characterization of this relationship was developed. This method was based on a modification of the so-called turbulent orifice equation. The general approach included a self-tuning algorithm. Next, the modified turbulent orifice equation was applied in conjunction with the model reference valve controller to create a single component pressure compensated flow control device. This required an inverse solution to the modified orifice equation. Finally, the kinematics of a specific single link hydraulically actuated mechanism were solved. Integration of the kinematic solution with the flow control device allowed for predictive velocity control of the single link mechanism.

Numerical ice sheet modeling is a rather young discipline: it started in the 1950s. The "first generation" models developed at that time are currently being replaced by "new generations" ones, such as e.g. ARCTIC-TARAH. ARCTIC-TARAH is a Bert Bolin Center for Climate Research spin-off from the Pennsylvania State University Ice sheet model (PSUI). When the Bolin Center received PSUI for subsequent independent development and adaption of the code to Arctic settings in 2010, an initial inspection of the source code suggested that PSUI also contained a module that allows for the treatment of glacial hydraulics. A numerical ice sheet model including coupling of ice dynamics and hydraulics is an extremely important tool in testing new hypotheses of former geological events. E.g., based on the recent finding that Arctic Ocean sediments contain a very distinct signature, it has been suggested that ice dammed lakes at the south-eastern margin of the late Weichselian Eurasian ice sheet drained into the Arctic Ocean in a catastrophic event around 55.000 years ago. The aim of this thesis is to perform a reconnaissance analysis of the glacio-hydraulic algorithms in ARCTIC-TARAH, as "inherited" (but never with published record of functionality) from PSUI. The work is carried out in two steps: first the routines and algorithms describing the hydraulics are located and explored, and then these routines are tested and verified by performing experiment simulations. The investigation of the program code reveals the presence of two hydraulics related modules in ARCTIC-TARAH. The main tasks of the module Water are to initiate lakes and oceans and to adjust hydrostatic pressure in each lake. Further, with the module Move Water activated, transportation of water (e.g. in rivers) is possible. Results from idealized experiment simulations verify the functionality of the routines in the module Water. An in-depth analysis of the module Move Water suggests that there is a mismatch in time units when solving the equations describing flow of water. Experiment simulations also support this flaw detected in the flow model. Preliminary adjustments were made to the source code  of the module Move Water, which made it possible to simulate the transportation of water both under an ice sheet and in rivers on land. However, these adjustments do not solve the problem of mismatching time scales, and the numerical solutions obtained from the experiments were observed to be unstable and, therefore, possibly incorrect. To be able to perform more advanced simulations in support of the above mentioned hypothesis, the flow model in the module Move Water needs to be improved or replaced. One solution to the problem with mismatching time scales, could be to use a so called multiscale solution in time.

A common problem encountered in mobile hydraulics is the desire to automate motion control functions in a restricted-cost and restricted-sensor environment. In this thesis a solution to this problem is presented. A velocity control scheme based on a novel single component pressure compensated ow controller was developed and evaluated. <p> The development of the controller involved solving several distinct technical challenges. First, a model reference control scheme was developed to provide control of the valve spool displacement for a particular electrohydraulic proportional valve. The control scheme had the effect of desensitizing the transient behaviour of the valve dynamics to changes in operating condition. Next, the pressure/flow relationship of the same valve was examined. A general approach for the mathematical characterization of this relationship was developed. This method was based on a modification of the so-called turbulent orifice equation. The general approach included a self-tuning algorithm. Next, the modified turbulent orifice equation was applied in conjunction with the model reference valve controller to create a single component pressure compensated flow control device. This required an inverse solution to the modified orifice equation. Finally, the kinematics of a specific single link hydraulically actuated mechanism were solved. Integration of the kinematic solution with the flow control device allowed for predictive velocity control of the single link mechanism.

No description available.

The Tsallis entropy is applied to derive both 1-D and 2-D velocity distributions in an open channel cross section. These distributions contain a parameter m through which the Tsallis entropy becomes a generalization of the Shannon entropy. Different m parameter values are examined to determine the best value for describing the velocity distribution.Two Lagrangian parameters that are involved in the final form of 1-D velocity distribution equation are determined from observations of mean velocity and the maximum velocity at the water surface. For channels which are not wide and where the maximum velocity does not occur at the water surface, a 2-D velocity distribution is more appropriate. The Tsallis entropy is applied to derive 2-D velocity distributions. A new parameter M is introduced which represents the hydraulic characteristics of the channel. The derived velocity distributions are verified using both field data and experimental data. The advantages are found by comparing with Parandtl-von Karman, power law and Chiu’s velocity distributions.

A new correlation for the prediction of the Countercurrent Flow Limitation (CCFL) in a large diameter tube with a falling water lm is proposed. Dierent from previous correlations, it predicts the onset of ooding by considering the relative velocities of the working uids and the lm thickness of the liquid layer. This provides a more complete accounting of the physical forces contributing to CCFL. This work has been undertaken in order to provide a better estimate of CCFL for reactor safety codes such as MELCOR, MAAP, and SCDAP/RELAP. Experiments were conducted to determine the CCFL for a 3-inch inner diameter smooth tube with an annular liquid lm and air injection from the bottom. The size of the test section and the range of working uid ow rates were based on a scaling analysis of the surge line of a PressurizedWater Reactor pressurizer. An experimental facility was designed and constructed based on this analysis in order to collect data on the CCFL phenomenon. In order to capture some of the physical phenomena at the onset of ooding visual pictures were taken at high speed. These pictures provided a new understanding of the process of transition to ooding. The facility also produced a new set of ooding data. This can also lead to a more comprehensive mechanistic model.

Thèse de doctorat : Sciences : Paris, Faculté des sciences : 1867. / Titre provenant de l'écran-titre.