The Shield&rsquo / s Diagram has been the key stone for the description of initiatial motion of a particle in open channel flow. Data in Shield&rsquo / s study and further studies are collected in channels. However, the approximation of these data for the case of withdrawal of sediment or clean water through bottom outlets has not been confirmed. Furthermore, two phase models run to simulate the phenomenon so far have used brine and water combination. In this study, an experimental attempt is made to study the behavior of deposits subject to withdrawal from a bottom outlet where there are not enough parameters to calculate the bottom shear stress and consequently the dimensionless parameters generally used for the description of initiation of motion. The experimental set up used for this purpose is a 1 m long and 0.35 m wide channel such that at the downstream of the channel there is a horizontal slit representing the bottom outlet. During the experiments, fresh water and sand with D50 = 0.298 mm and D50 = 0.912 mm are used. Two different widths of the slit, namely 0.35 m and 0.0875 m are investigated. Based on the observations of the incipient motion of the sediment, the findings in the form of a relationship among the discharge through the bottom outlet, and some other relevant parameters are reported. In addition, a comparison of these data with the literature by the help of some newly defined dimensionless parameters for the description of the initiation of motion is included.

In this thesis was presented Nové Heřminovy dam with basic parameters. Requirements on bottom outlets and intake objects are presented as well. Analysis of used valves on all dams in Czech Republic was done as an underlay for suggestions of bottom outlets in this thesis. The main task was to suggest three variations of bottom outlets. Differences are in number of outlets, dimensions, placing and valves. Then variation of intake objects. Each of variation was verbally described and filled with calculations.

If air is entrained in a bottom outlet of a dam in an uncontrolled way, the resulting air pockets may cause problems such as blowback, blowout and loss of discharge capacity. In order to provide guidance for bottom outlet design and operation, this study examines how governing parameters affect air entrainment, air-pocket transport and de-aeration and the surrounding flow structure in pipe flows. Both experimental and numerical approaches are used. Air can be entrained into the bottom outlet conduit due to vortex formation at the intake if the intake submergence is not sufficient. The influent of the intake entrance profiles and channel width on the critical submergence were studied in the experiment. The experimental study was performed to investigate the incipient motion of air pockets in pipes with rectangular and circular cross sections. The critical velocity is dependent on pipe slope, pipe diameter, pipe roughness and air-pocket volume. If the pipe is horizontal, air removal is generally easier in a rectangular pipe than in a circular pipe. However, if the pipe is downward-inclined, air removal is easier in a circular pipe. When a bottom outlet gate opens, air can become entrained into the conduit in the gate shaft downstream of the gate. Using FLUENT software, the transient process of air entrainment into a prototype bottom outlet during gate opening is simulated in three dimensions. The simulations show in the flow-pattern changes in the conduit and the amount of air entrainment in the gate shaft. The initial conduit water level affects the degree of air entrainment. A de-aeration chamber is effective in reducing water surface fluctuations at blowout. High-speed particle image velocimetry (HSPIV) were applied to investigate the characteristics of the flow field around a stationary air pocket in a fully developed horizontal pipe flow. The air pocket generates a horseshoe vortex upstream and a reverse flow downstream. A shear layer forms from the separation point. Flow reattachment is observed for large air pockets. The air―water interface moves with the adjacent flow. A similarity profile is obtained for the mean streamwise velocity in the shear layer beneath the air pocket. / <p>QC 20140211</p>

Water structure Ivanské jezero was built on the Javorník Creek back between 1905-1907. The main purpose of the dam was accumulation of high volumes of water and protection of the territory downstream. After the adjustment for higher flows on the river Kněžna in Rychnov nad Kněžnou, which was completed in 1937, the water structure lost the protective function. On the basis of an assessment made by Povodí Labe in 1993 - due to the low volume of the reservoir there is no flood wave transformation and already while flow rates greater than Q50 pass through dam, it results in overflowing the dam. To this date water structure Ivanské jezero is in very poor condition due to degradation of the binding material in the dam. The goal of the thesis is to propose a procedure for removal of the existing structure and the subsequent construction of the design and construction of a new – gravity, concrete dam. This work will contain technological removal process of current dam and possible usage options for the dam material. In the next step a new structure will be designed in the place of existing dam. After new design is completed there will be hydraulic assessment of the functional objects, hydrology and stability on the dam.

Undesired air entrainment in bottom outlet conduits of dams may cause pressure transients, leading to conduit vibrations, blowback, discharge pulsation and even cavitation, and jeopardize the operational safety. Due to design limitations or construction costs, it is impossible to create an air free environment in a pressurized pipe. Therefore, it is essential to understand the air transport in enclosed pipes in order to provide guidance in bottom outlet design and operation. The commonly used criterion of the air-pocket movement in pipe flow is the water flow velocity for starting moving an air pocket, the so-called critical velocity. In this thesis, the classical Volume of Fluid (VOF) model combined with the k-ε turbulence model is adopted for the computation of the critical velocity of a 150-mm pipe. The computed critical velocities are compared with the experimental results. The governing parameters investigated in this study include pipe slope and diameter, wall shear stress and air-pocket volume. Meanwhile, the carrying capacity (air-pocket velocity/ flow velocity) at all pipe slopes are analyzed. The simulation results of air pockets with different volumes in the bottom outlet conduit of Letten Dam in Sweden are presented in this study. Moreover, experimental study was conducted to measure the critical velocity for a 240-mm Plexiglas pipe. The results are in agreement with the experiments performed by HR Wallingford (HRW) in 2003 in terms of the effects of pipe slope and air-pocket volume; however, the critical Froude pipe number is slightly smaller in this study. In rough pipes, a larger critical velocity is required compared with that in the smooth pipe. The removal mechanism in the rough pipe involves the successive loss of air caused by turbulence. This explains that the air-pocket size, with the dimensionless air-pocket volume n &lt; 0.015, has little impact on the critical velocity for the rough pipe. In addition, roughness has little impact on the air-pocket velocity when it moves upstream in the downward inclined pipe. The trapped air bubbles most likely remain permanently in the rough pipe. / QC 20120110

The theme of this diploma thesis is to restore the existing small reservoir in the village Žďárná. A new safety spillway and bottom outlet will be built, the flood will be shaped according to the cross-sections and the dam of the water reservoir will be fortified. The designed objects will be hydraulically verified. Using the HEC-HMS program, a hydrological model of the river basin is created and subsequently a derived flood wave PV20.

This diploma thesis, called „Reconstruction of the small water reservoir Hradisko in the cadastral area of Radslavice“, focuses on the complex process of a reconstruction of the small water reservoir Hradisko. This work follows up on the bachelor’s thesis, in which the current state of the Hradisko reservoir was described in detail. Based on the survey of the dam and the flood using a GPS device, detailed project documentation was prepared. Within the solution for the reconstruction of Hradisko reservoir, a repair of the dam and the increase of the crown of the dam is proposed, new functional objects are dimensioned, the bottom is cleared of mud, including modifications in the flood, and other necessary steps for proper functioning of the crumbling no longer compliant reservoir are described. Functional objects are processed for two variants of the solution. The first option consists of the design of a bottom outlet and a safety spillway, and the second alternative involves the design of a combined functional block. In the end, the total costs of both options are quantified and compared on the basis of an indicative item budget.

The subject of the thesis is to develop a simplified documentation of multipurpose reservoirs in the cadastral territory Třebařov. This thesis consists of the text, graphic and hydraulic calculations.

The subject of the thesis is to design proposal protective water management solution reservoirs in the basin Kobylí potok. This thesis consist of the text, hydraulic calculation and graphic.

The thesis aims to determine the influence partial or complete submerge of hollow cone valve by outflow on its capacity without space restrictions, by outflow into discharge chamber and by outflow into water tunnel of circular cross section. The valve capacity is for mutual comparability purposes usually characterized by discharge coefficient. Research works have been performed on a spatial hydraulic model of the valve with inlet diameter D = 67 mm and an apex angle of a cone 90°. Values of the discharge coefficient obtained from measurements were statistically analyzed. The dependence of discharge coefficient, expressed by energy head, on submerged level was approximated by an exponential function. Exponent value of this function express the dependance rate of valve capacity on downstream water level. This procedure didn’t demonstrate signifiant dependance downstream water level on hollow cone valve capacity, only on tests at outflow to water tunel showed a low increase in the discharge coefficient partly due to the influence of kinetic energy of the stream flowing out of the tunnel on the energy head and also due to underpressure. Independence of discharge coefficient value on valve head has been prooved for head greather than 232 mm. Also was defined 3 stages of interaction outflow jet from valve and downstream water, some of them may cause on real waterworks structures unfavorable situations (may affect excessive load on valve by pressure pulsations). The presented results allow better evaluation of bottom outlets capacity at higher water levels, when the valves are flooded. Significant effect of sufficient aeration (especially in long water tunnels) on valve capacity was also confirmed. Taking into account on the specifics of hollow jet valves and cone valves, it is possible to generalize some of this resultos on them as well.