scholarly journals Numerical studies for a better understanding of static ice loads on dams

2018 ◽  
Vol 45 (1) ◽  
pp. 18-29 ◽  
Author(s):  
Ekaterina Kharik ◽  
Brian Morse ◽  
Varvara Roubtsova ◽  
Mario Fafard ◽  
Alain Côté ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Water Level ◽  
Material Model ◽  
Initial Stresses ◽  
Water Level Fluctuations ◽  
Intermediate Water ◽  
Numerical Studies ◽  
Ice Loads ◽  
The Impact ◽  
Potential Maximum

It is important to anticipate potential maximum ice loads to ensure the structural stability of dams in cold climates. Finite element modeling (FEM) can provide some insights into process mechanisms. Four important ice-loading events on dams are presented and simulated. The measured loads were caused by the thermal expansion of ice together with intermediate water level fluctuations. Only the thermal expansion is modeled by the FEM, but the impact of water level fluctuations can increase lateral confinement that increases the predicted load by 36% to 106%, particularly when the cover contains mostly columnar ice. It is demonstrated that the presence of snow ice in the cover can decrease the predicted load by 35% to 53%. The study also demonstrates how initial stresses in the ice can affect the ultimate load and show that the very-difficult-to-manage delayed-elastic strain term need not be included in the material model where preliminary results suffice.

Quantifying recent lake level changes in Patagonia (Argentina and Chile): Back to the future?

2021 ◽  
Author(s):  
Daniel Ariztegui ◽  
Clément Pollier ◽  
Andrés Bilmes
Keyword(s):  
Water Level ◽  
Lake Level ◽  
Satellite Images ◽  
Meteorological Data ◽  
Tierra Del Fuego ◽  
Water Level Fluctuations ◽  
Lake Levels ◽  
The Past ◽  
Rainfall Variations ◽  
The Impact

<p>Lake levels in hydrologically closed-basins are very sensitive to climatically and/or anthropogenically triggered environmental changes. Their record through time can provide valuable information to forecast changes that can have substantial economical and societal impact.</p><p>Increasing precipitation in eastern Patagonia (Argentina) have been documented following years with strong El Niño (cold) events using historical and meteorological data. Quantifying changes in modern lake levels allow determining the impact of rainfall variations while contributing to anticipate the evolution of lacustrine systems over the next decades with expected fluctuations in ENSO frequencies. Laguna Carrilaufquen Grande is located in the intermontane Maquinchao Basin, Argentina. Its dimension fluctuates greatly, from 20 to 55 km<sup>2</sup> water surface area and an average water depth of 3 m. Several well-preserved gravelly beach ridges witness rainfall variations that can be compared to meteorological data and satellite images covering the last ~50 years. Our results show that in 2016 lake level was the lowest of the past 44 years whereas the maximum lake level was recorded in 1985 (+11.8 m above the current lake level) in a position 1.6 km to the east of the present shoreline. A five-years moving average rainfall record of the area was calculated smoothing the extreme annual events and correlated to the determined lake level fluctuations. The annual variation of lake levels was up to 1.2 m (e.g. 2014) whereas decadal variations related to humid-arid periods for the interval 2002 to 2016 were up to 9.4 m. These data are consistent with those from other monitored lakes and, thus, our approach opens up new perspectives to understand the historical water level fluctuations of lakes with non-available monitoring data.</p><p> </p><p>Laguna de los Cisnes in the Chilean section of the island of Tierra del Fuego, is a closed-lake presently divided into two sections of 2.2 and 11.9 km<sup>2</sup>, respectively. These two water bodies were united in the past forming a single larger lake. The lake level was  ca. 4 m higher than today as shown by clear shorelines and the outcropping of large Ca-rich microbialites. Historical data, aerial photographs and satellite images indicate that the most recent changes in lake level are the result of a massive decrease of water input during the last half of the 20<sup>th</sup> century triggered by an indiscriminate use of the incoming water for agricultural purposes. The spectacular outcropping of living and fossil microbialites is not only interesting from a scientific point of view but has also initiated the development of the site as a local touristic attraction. However, if the use of the incoming water for agriculture in the catchment remains unregulated the lake water level might drop dangerously and eventually the lake might fully desiccate.</p><p>These two examples illustrate how recent changes in lake level can be used to anticipate the near future of lakes. They show that ongoing climate changes along with the growing demand of natural resources have already started to impact lacustrine systems and this is likely to increase in the decades to come.</p>

scholarly journals Effects of Water Depth on the Growth of the Submerged Macrophytes Vallisneria natans and Hydrilla verticillata: Implications for Water Level Management

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2590
Author(s):  
Qisheng Li ◽  
Yanqing Han ◽  
Kunquan Chen ◽  
Xiaolong Huang ◽  
Kuanyi Li ◽  
...  
Keyword(s):  
Water Level ◽  
Water Depth ◽  
Deep Water ◽  
Submerged Macrophytes ◽  
Hydrilla Verticillata ◽  
Water Level Fluctuations ◽  
Total Biomass ◽  
Intermediate Water ◽  
Factors Affecting ◽  
Vallisneria Natans

Water level is one of the most important factors affecting the growth of submerged macrophytes in aquatic ecosystems. The rosette plant Vallisneria natans and the erect plant Hydrilla verticillata are two common submerged macrophytes in lakes of the middle and lower reaches of the Yangtze River, China. How water level fluctuations affect their growth and competition is still unknown. In this study, three water depths (50 cm, 150 cm, and 250 cm) were established to explore the responses in growth and competitive patterns of the two plant species to water depth under mixed planting conditions. The results show that, compared with shallow water conditions (50 cm), the growth of both submerged macrophytes was severely suppressed in deep water depth (250 cm), while only V. natans was inhibited under intermediate water depth (150 cm). Moreover, the ratio of biomass of V. natans to H. verticillata gradually increased with increasing water depth, indicating that deep water enhanced the competitive advantage of V. natans over H.verticillata. Morphological adaptation of the two submerged macrophytes to water depth was different. With increasing water depth, H. verticillata increased its height, at the cost of reduced plant numbers to adapt to poor light conditions. A similar strategy was also observed in V. natans, when water depth increased from 50 cm to 150 cm. However, both the plant height and number were reduced at deep water depth (250 cm). Our study suggests that water level reduction in lake restoration efforts could increase the total biomass of submerged macrophytes, but the domination of key plants, such as V. natans, may decrease.

Modeling the impact of in-stream water level fluctuations on stream-aquifer interactions at the regional scale

2011 ◽  
Vol 400 (3-4) ◽  
pp. 490-500 ◽  
Author(s):  
Firas Saleh ◽  
Nicolas Flipo ◽  
Florence Habets ◽  
Agnès Ducharne ◽  
Ludovic Oudin ◽  
...  
Keyword(s):  
Water Level ◽  
Stream Water ◽  
Regional Scale ◽  
Water Level Fluctuations ◽  
The Impact

scholarly journals Water Level Fluctuations in the Turawa Reservoir in Relation to the Tourist Use of the Water Body

2008 ◽  
Vol 13 (1) ◽  
pp. 133-144
Author(s):  
Andrzej T. Jankowski ◽  
Marek Ruman
Keyword(s):  
Water Level ◽  
Water Body ◽  
High Water ◽  
Ecological Condition ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Natural Factors ◽  
Odra River ◽  
The Impact ◽  
First Time

Abstract The aim of the paper is to assess the fluctuations of water levels in the Turawa Reservoir (50° 43’ N, 18° 08’ E) in relation to the tourist use of the water body. The reservoir is situated within the macroregion of the Silesian Lowland in the mesoregion of the Opole Plain. In administrative terms, the reservoir is situated in the pole Province within the borough of Turawa. In hydrological terms, in turn, it is situated in the catchment area of the Mała Panew river, which belongs to the basin of the Odra river. The Turawa Reservoir was opened for use in 1938, and in 1948 it was filled with water to its maximum for the first time. At present, the surface area of the reservoir, when it is filled with water to its maximum, is about 20.8 km2, its volume 99.5 mln m3, and its depth exceeds 13 meters. In the period of hydrological years 1976-2000 water levels in this reservoir were characterized by high, unnoticed in natural conditions, amplitudes of changes reaching 6.99 m. Anthropogenically stimulated fluctuations in the water level result in conflicts in terms of tasks and functions that the Turawa Reservoir was designed for. Changes in the level of the water surface in the Turawa Reservoir resulted from the impact of the natural factors (thaw and rainfall related high water levels), as well as anthropogenic ones (the need to improve sailing conditions, water supply for industrial and municipal needs). Decreasing the fluctuations of water levels in the Turawa Reservoir is necessary in order to maintain its tourist-recreational functions and keep the ecological condition of its waters at the appropriate level.

scholarly journals NUMERICAL MODELLING OF BIRD STRIKE ON A ROTATING ENGINE BLADES BASED ON VARIATIONS OF POROSITY DENSITY

2022 ◽  
Vol 23 (1) ◽  
pp. 412-423
Author(s):  
Sharis-Shazzali Shahimi ◽  
Nur Azam Abdullah ◽  
Ameen Topa ◽  
Meftah Hrairi ◽  
Ahmad Faris Ismail
Keyword(s):  
Numerical Modelling ◽  
Structural Integrity ◽  
Constitutive Relations ◽  
Material Model ◽  
Initial Stresses ◽  
Model Parameters ◽  
Bird Strike ◽  
Elastic Plastic ◽  
Engine Blade ◽  
The Impact

A numerical investigation is conducted on a rotating engine blade subjected to a bird strike impact. The bird strike is numerically modelled as a cylindrical gelatine with hemispherical ends to simulate impact on a rotating engine blade. Numerical modelling of a rotating engine blade has shown that bird strikes can severely damage an engine blade, especially as the engine blade rotates, as the rotation causes initial stresses on the root of the engine blade. This paper presents a numerical modelling of the engine blades subjected to bird strike with porosity implemented on the engine blades to investigate further damage assessment due to this porosity effect. As porosity influences the decibel levels on a propeller blade or engine blade, the damage due to bird strikes can investigate the compromise this effect has on the structural integrity of the engine blades. This paper utilizes a bird strike simulation through an LS-Dyna Pre-post software. The numerical constitutive relations are keyed into the keyword manager where the bird’s SPH density, a 10 ms simulation time, and bird velocity of 100 m/s are all set. The blade rotates counter-clockwise at 200 rad/s with a tetrahedron mesh. The porous regions or voids along the blade are featured as 5 mm diameter voids, each spaced 5 mm apart. The bird is modelled as an Elastic-Plastic-Hydrodynamic material model to analyze the bird’s fluid behavior through a polynomial equation of state. To simulate the fluid structure interaction, the blade is modelled with Johnson-Cook Material model parameters of aluminium where the damage of the impact can be observed. The observations presented are compared to previous study of a bird strike impact on non-porous engine blades. ABSTRAK: Penyelidikan berangka telah dijalankan ke atas bilah enjin berputar tertakluk kepada impak pelanggaran burung. Pelanggaran burung tersebut telah dimodelkan secara berangka sebagai silinder gelatin dengan hujungnya berbentuk hemisfera demi mensimulasikan impaknya ke atas bilah enjin yang berputar. Pemodelan berangka bilah-bilah enjin yang berputar tersebut menunjukkan bahawa pelanggaran burung mampu menyebabkan kerosakan teruk terhadap bilah enjin terutamanya apabila bilah enjin sedang berputar oleh sebab putaran menghasilkan tekanan asal di pangkal bilah enjin. Kajian ini mengetengahkan pemodelan berangka ke atas bilah-bilah enjin tertakluk kepada pelanggaran burung terhadap bilah-bilah enjin yg mempunyai keliangan demi menyelidik dan menilai kerosakan kesan daripada keliangan tersebut. Keliangan juga mempengaruhi tahap-tahap desibel ke atas bilah kipas ataupun bilah enjin, kerosakan hasil serangan burung boleh menterjemah tahap ketahanan struktur integriti bagi bilah-bilah enjin tersebut. Penyelidikan ini mengguna pakai perisian “LS-Dyna Pre-post” untuk simulasi pelanggaran burung. Hubungan konstitutif berangka telah dimasukkan sebagai kata kunci di mana ketumpatan SPH burung, masa simulasi 10ms, dan halaju burung ditetapkan kepada 100 m/s. Bilah tersebut berputar pada 200 rad/s arah lawan jam dengan jejaring tetrahedron. Kawasan berliang atau kosong di sepanjang bilah ditetapkan diameternya kepada 5 mm, dan dijarakkan 5 mm di antara satu sama lain. Burung pula dimodelkan sebagai material “Elastic-Plastic-Hydrodynamic” untuk mengkaji sifat bendalir burung melalui persamaan polinomial. Demi mensimulasi interaksi struktur bendalir, bilah tersebut dimodelkan sebagai parameter aluminium material “Johnson Cook” di mana kerosakan daripada impak tersebut dapat diteliti. Penelitian-penelitian tersebut dibandingkan dengan kajian terdahulu ke atas serangan burung terhadap bilah-bilah enjin tidak berliang.

scholarly journals Features of the balance structure formation of groundwater withdrawal and its effect on river flow at a subsoil water level drawdown

2019 ◽  
Vol 46 (3) ◽  
pp. 247-258
Author(s):  
S. O. Grinevsky ◽  
V. S. Sporyshev
Keyword(s):  
Water Balance ◽  
Water Level ◽  
River Flow ◽  
Groundwater Withdrawal ◽  
Intermediate Water ◽  
Subsoil Water ◽  
Balance Structure ◽  
The Impact ◽  
Subsoil Water Level ◽  
Infiltration Recharge

The balance structure of the pumpage sourses of riverside water-intakes, developing a subsoil aquifer or intermediate water that hydraulically interacts with it, can show the effect of the processes of water balance adjustment in the unsaturated zone to the accompanying subsoil water level drawdown. In this case, because of the shallow depth to subsoil water, its level drop due to water withdrawal causes a decrease in evapotranspiration and an increase in groundwater infiltration recharge. These processes have their effect on the balance structure of usable water resources as components of natural and involved resources and reduce the impact of groundwater pumping on river flow. Analysis of the operational data of the Sudogda waterintake in Vladimir oblast and geohydrological modeling were used to evaluate variations of the groundwater evaportanspiration losses and infiltration recharge and their role in the water balance structure of reserves of a field and in the impact of groundwater withdrawal on river flow.

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