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The application of a minimum specific energy concept for a fish ladder design

Kubrak Michał, Smoliński Błażej, Riha Jaromír, Kodura Apoloniusz, Popielski Paweł, Jabłoński Kamil

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

555--568

EN

Structural solutions in terms of fish ladders and the use of natural materials to construct them often raise concerns regarding the possibility of using the standard calculation methods. The fish ladder being designed on the Wisłok river consists of three pools, separated from each other by baffles made of rock boulders. The purpose of this study was to analyze water surface profiles for fish ladder at specific values of flow rates. The paper presents the results of hydraulic calculations under the conditions of constant flow rate based on the concept of a minimum specific energy. According to this method, water flow through boulders is critical. Thus, it does not take into account head losses, which are hard to estimate and which are the integral part of typical calculation methods, e.g. the use of equations to determine the flow rate of a weir. An additional advantage of this method is that there is no need to assume the flow pattern of one specific weir. Verification calculations of the water depths were conducted using the HEC-RAS software, under an assumption of an one-dimensional steady water flow. Water depths in the fish ladder, calculated using both methods, were similar, despite the adopted different calculation concepts, and can be used in ichthyologic analyses.

PL

Rozwiązania konstrukcyjne przepławek i wykorzystywanie do ich budowy naturalnych materiałów budzą często obawy o możiwości stosowania do ich obliczeń typowych schematów hydraulicznych. Projektowana przepławka na rzece Wisłok składa się z trzech komór, oddzielonych od siebie przegrodami z kamiennych głazów. Celem obliczeń było określenie profilu zwierciadła wody w przepławce przy wybranych wartościach natężeń przepływu wody. Przedstawiono wyniki obliczeń hydraulicznych przepławki przeprowadzone w warunkach stałego natężenia przepływu w oparciu o zasadę minimalnej energii własnej strumienia wody. Według tej metody woda przepływa przez szczeliny lub przelewa się nad głazami przy minimalnym nakładzie energii (przepływ odbywa się ruchem krytycznym). W obliczeniach założono, że głazy są prostopadłościanami, a przekroje poprzeczne szczelin mają kształt prostokąta. Obliczenia weryfikacyjne głębokości wody przeprowadzono programem HEC-RAS w założeniu występowania ruchu ustalonego wody. Obliczone obiema metodami głębokości wody w przepławce są zbliżone, mimo przyjętych różnych koncepcji obliczeń i mogą być wykorzystane w analizach ichtiologicznych.

2

Outlet Flow Velocity in Circular Culvert

Szpakowski W.

Archives of Hydro-Engineering and Environmental Mechanics

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2014

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Vol. 61, nr 3-4

193–-203

EN

The outlet flow velocity in the end section of the culvert barrel depends in most cases on the culvert geometry, including the barrel slope, as well as on upstream and downstream channel parameters. Flowing water can create pressure flow or free surface flow in the culvert barrel. In the case of an unsubmerged barrel outlet, the free-surface flow is more frequent than the full flow. Increased velocities can cause channel bed scour and bank erosion downstream of the culvert outlet. Different culvert flow cases in which the barrel outlet is unsubmerged are presented in this paper. The influence of the flow regime on the outlet velocity is also discussed.

3

Liquid unloading optimization from gas wells which exploit depleted reservoirs

Tataru A., Stefanescu D. P., Simescu B.

AGH Drilling, Oil, Gas

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2014

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Vol. 31, no. 2

241--

EN

One of the most important aspects in natural gas exploitation, which must be constantly monitored, is the liquid impurities loading in gas wells, mostly in depleted reservoirs. The extension of this phenomenon is observed, as the natural gas reservoirs are depleted, thus substantially reduction of the reservoir pressure. The increasing quantity of liquid impurities is a major problem in gas depleted reservoirs exploitation, which could not be naturally removed in energetical depletion conditions. In this period, to avoid liquids acumulation and afterwards flooding, wells must produce with a minimum flow, named critical flow, under whose value is not possible the unloading of accumulated liquids. Wells can produce without liquid accumulations if in the tubing is obtained a gas flow velocity, greater than the liquid drop free dowfall speed limit. The velocity and critical flow depend on bottom hole or surface dynamie pressure, flow section diameter, liquid and gas density, water superficial strength. Liquid flow inerease during gas depleted reservoir exploitation, but only a part of this quantity is naturally unloaded by gas stream, the other part tend to accumulate to the bottom hole. In this conditions, the dynamie bottom hole pressure will inerease continuosly, causing continuous dropping and pronounced gas flow rate, until the well floods and stops producing. Early recognition of signs that indicates well liquid loading and the most suitable lifting system selection can eliminate problems before the production drops and layers damage.