scholarly journals Lampiran 1A Paper Sediment Characteristics and Wind Induced Sediment Dynamics in Lake Markemeer, the Netherlands, Aquatic Sciences

2021 ◽  
Author(s):  
Philiphi de Rozari
Keyword(s):  
Sediment Resuspension ◽  
Sediment Dynamics ◽  
Sediment Characteristics ◽  
Wind Speeds ◽  
Sediment Bed ◽  
Trap Field ◽  
Average Wind ◽  
Waves And Currents ◽  
Aquatic Sciences ◽  
Extreme Winds

In 2007/08, a study was undertaken on thesediment dynamics in shallow Lake Markermeer (theNetherlands). Firstly, sediment characteristics were determined at 49 sites in the lake. Parameters such as median grain size and loss on ignition showed a spatial as well as water depth related pattern, indicating wind-induced sediment transport. Highly significant correlations were found between all sediment parameters. Lake Markermeer sediment dynamics were investigated in a sediment trap field survey at two permanent stations in the lake. Sedimentyields, virtually all coming from sediment resuspension, were significantly correlated with average wind speeds,though periods of extreme winds also played a role.Sediment resuspension rates for Lake Markermeer were high, viz. on average ca. 1,000 g m-2 day-1. The highlydynamic nature of Lake Markermeer sediments must bedue to the overall shallowness of the lake, together with itslarge surface area (dynamic ratio = [H(area)]/[averagedepth] = 7.5); wind-induced waves and currents willimpact most of the lake’s sediment bed. Indeed, near-bed currents can easily reach values 10 cm/s. Measurements of the thickness of the settled ‘‘mud’’ layer, as well as 137Csdating, showed that long-term deposition only takes placein the deeper SE area of the lake. Finally, lake sediment dynamics were investigated in preliminary laboratory experiments in a small ‘‘micro-flume’’, applying increasingwater currents onto five Lake Markermeer sediments.Sediment resuspension started off at 0.5–0.7 cm/s andshowed a strongly exponential behaviour with respect to these currents.

scholarly journals Lampiran 1B Paper Sediment dynamics in shallow Lake Markermeer, The Netherlands: field/laboratory surveys and first results for a 3-D suspended solids model

2021 ◽  
Author(s):  
Philiphi de Rozari
Keyword(s):  
The Netherlands ◽  
Shallow Lake ◽  
Suspended Solids ◽  
Sediment Resuspension ◽  
Sediment Dynamics ◽  
Lake Area ◽  
Sediment Yields ◽  
Wind Speeds ◽  
First Results ◽  
Set Up

In 2007/08, a study was undertaken on sediment dynamics in shallow Lake Markermeer, The Netherlands. Firstly, the sediment characteristics median grain size, mud content and loss on ignition showed a spatial as well as water depth related pattern indicating wind-induced sediment transport. Sediment dynamics were investigated in a sediment trap field survey at two stations. Sediment yields, virtually all coming from sediment resuspension, were significantly correlated with wind speeds. Resuspension rates for Lake Markermeer were very high, viz. ca. 1,000 g/m2 day as an annual average, leading to high suspended solids (SS) contents, due to the large lake area and its shallowness (high ‘Dynamic Ratio’). Sediment resuspension behaviour was further investigated in preliminary laboratory experiments using a ‘micro-flume’, applying increasing water currents onto five Lake Markermeer sediments. Resuspension showed a clear exponential behaviour. Finally, a 3-D model was set up for water quality and SS contents in Lake Markermeer; first results showed a good agreement between modelled and actual SS contents. Construction of artificial islands and dams will reduce wind fetches and may be expected to cause a substantial decrease in lake water turbidity.

scholarly journals Sediment dynamics in shallow Lake Markermeer, The Netherlands: field/laboratory surveys and first results for a 3-D suspended solids model

2012 ◽  
Vol 66 (9) ◽  
pp. 1984-1990
Author(s):  
P. Kelderman ◽  
P. De Rozari ◽  
S. Mukhopadhyay ◽  
R. O. Ang'weya
Keyword(s):  
The Netherlands ◽  
Shallow Lake ◽  
Suspended Solids ◽  
Sediment Resuspension ◽  
Sediment Dynamics ◽  
Lake Area ◽  
Sediment Yields ◽  
Wind Speeds ◽  
First Results ◽  
Set Up

In 2007/08, a study was undertaken on sediment dynamics in shallow Lake Markermeer, The Netherlands. Firstly, the sediment characteristics median grain size, mud content and loss on ignition showed a spatial as well as water depth related pattern indicating wind-induced sediment transport. Sediment dynamics were investigated in a sediment trap field survey at two stations. Sediment yields, virtually all coming from sediment resuspension, were significantly correlated with wind speeds. Resuspension rates for Lake Markermeer were very high, viz. ca. 1,000 g/m2day as an annual average, leading to high suspended solids (SS) contents, due to the large lake area and its shallowness (high ‘Dynamic Ratio’). Sediment resuspension behaviour was further investigated in preliminary laboratory experiments using a ‘micro-flume’, applying increasing water currents onto five Lake Markermeer sediments. Resuspension showed a clear exponential behaviour. Finally, a 3-D model was set up for water quality and SS contents in Lake Markermeer; first results showed a good agreement between modelled and actual SS contents. Construction of artificial islands and dams will reduce wind fetches and may be expected to cause a substantial decrease in lake water turbidity.

scholarly journals A CRITICAL ESTIMATION OF DATA ON EXTREME WINDS IN LITHUANIA VĖJO KELIAMA ŽALA APLINKAI: KRITINIS DUOMENŲ APIE EKSTREMALIUS VĖJUS LIETUVOJE VERTINIMAS / ПОВРЕЖДЕНИЯ ОКРУЖАЮЩЕЙ СРЕДЫ, ВЫЗЫВАЕМЫЕ ВЕТРОМ: КРИТИЧЕСКАЯ ОЦЕНКА ДАННЫХ ПО ЭКСТРЕМАЛЬНЫМ ВЕТРАМ В ЛИТВЕ

2011 ◽  
Vol 19 (2) ◽  
pp. 178-188 ◽  
Author(s):  
Egidijus R. Vaidogas ◽  
Virmantas Juocevičius
Keyword(s):  
Wind Data ◽  
Data Set ◽  
Wind Speeds ◽  
The Past ◽  
Hurricane Wind ◽  
Average Wind ◽  
Extreme Wind ◽  
Separate Treatment ◽  
Basic Reference ◽  
Extreme Winds

An assessment of data on wind storms recorded in Lithuania during the past 48 years is presented. Records of storms with the average wind speeds of at least 30 m/s are compiled into one data set and presented in the paper. Reliability and meteorological homogeneity of wind storm data is assessed. The extreme wind data is estimated in relation to an assessment of damage to the built environment. An exceedance of basic reference wind speeds and design wind speeds specified in Lithuanian loading code by extreme winds (large cyclonic storms) is detected. The annual exceedance frequency was found to be considerably higher than the frequency of once per fifty years declared in the code. The exceedance was also found to be relatively dangerous in terms of magnitude. It is suggested to analyze wind data by a separate treatment of fastest annual winds and hurricane winds. Two hurricane wind regions are proposed for the Lithuanian territory. Basic reference wind speeds for these regions are calculated by applying the approach of partial duration series of extreme wind records. The regionalisation of hurricane-prone parts of Lithuania led to a compilation of two small-size statistical samples of hurricane wind speeds, which can be applied to an assessment of risk posed by hurricanes. Santrauka Nagrinėjami duomenys apie vėjo audras, kilusias Lietuvoje per pastaruosius 48 metus. Pateikiama duomenų apie vėjo audras, kurių vidutinis vėjo greitis buvo ne mažesnis kaip 30 m/s. Įvertinamas duomenų patikimumas ir meteorologinis homogeniškumas. Duomenys apie vėjo audras analizuojami vertinant tokių audrų galią sukelti užstatytos aplinkos pažeidimus. Nustatyta, kad ekstremalūs vėjai (didelės cikloninės audros) daugelį kartų viršijo bazinius atskaitinius ir projektinius vėjo greičius, apibrėžtus anksčiau Lietuvoje galiojusių ir dabar galiojančių projektavimo normų. Atskaitinių ir projektinių vėjo greičių viršijimai daug dažnesni nei normose nustatomas vieno karto per 50 metų dažnis. Atskaitinių ir projektinių vėjo greičių viršijimas taip pat yra gana pavojingas. Siūloma ekstremalius vėjo greičius analizuoti atskirai nagrinėjant metinius vėjo greičio maksimumus ir duomenis apie uraganinius vėjus. Lietuvos teritoriją siūloma dalyti į tris zonas, iš kurių dvi turėtų būti laikomos uraganinių vėjų zonomis. Baziniai atskaitiniai vėjo greičiai šiose zonose skaičiuojami taikant dalinės trukmės sekų metodiką. Uraganinių vėjų zonųįvedimas leido suformuoti dvi mažo dydžio statistines imtis, kurių elementai yra uraganinio vėjo greičio matavimų duomenys. Šias imtis siūloma taikyti vertinant uraganų sukeliamą riziką. Резюме Рассматривается оценка повреждений, которые могут быть причинены природной и застроенной среде экстремальными ветрами. Внимание сосредотачивается на ветровых штормах, наблюдавшихся в Литве за последние 48 лет. В статье представлены данные о штормах со средней скоростью ветра не менее 30 м/с. Оценивается надежность и метеорологическая однородность данных по экстремальным ветрам. Данные анализируются в свете их применения к оценке потенциальных повреждений застроенной среды. Установлено, что экстремальные ветра, создаваемые большими циклонами, во много раз превышали нормативные и расчетные значения скоростей ветра, установленные нормами проектирования, применявшимися в предыдущие годы и применяемыми в Литве в настоящее время. Частота превышения нормативных и расчетных значений значительно превышает декларируемую настоящими нормами одноразовую частоту за 50 лет. Степень превышения нормативных и расчетных значений скорости ветра также является достаточно опасной. Предлагается раздельный анализ данных по годовым максимумам скоростей ветра и данных по ураганам. Вводятся три зоны территории Литвы, две из которых следует рассматривать как зоны возможных ураганов. Нормативные значения скорости ветра в этих зонах определяются при помощи метода последовательностей частичной продолжительности. Введение зон ураганных ветров позволило сформировать две статистические выборки, включающие в себя относительно небольшое количество ураганных скоростей ветра. Предлагается использовать эти выборки для оценки риска, создаваемого ураганами.

SHAPING OF AN AUTONOMOUS POWER SYSTEM FOR GUARANTEED POWER SUPPLY WITH THE PREDOMINANCE WIND ENERGY

2018 ◽  
pp. 28-50
Author(s):  
S. G. Ignatiev ◽  
S. V. Kiseleva
Keyword(s):  
Energy Storage ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Diesel Generator ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Optimization of the autonomous wind-diesel plants composition and of their power for guaranteed energy supply, despite the long history of research, the diversity of approaches and methods, is an urgent problem. In this paper, a detailed analysis of the wind energy characteristics is proposed to shape an autonomous power system for a guaranteed power supply with predominance wind energy. The analysis was carried out on the basis of wind speed measurements in the south of the European part of Russia during 8 months at different heights with a discreteness of 10 minutes. As a result, we have obtained a sequence of average daily wind speeds and the sequences constructed by arbitrary variations in the distribution of average daily wind speeds in this interval. These sequences have been used to calculate energy balances in systems (wind turbines + diesel generator + consumer with constant and limited daily energy demand) and (wind turbines + diesel generator + consumer with constant and limited daily energy demand + energy storage). In order to maximize the use of wind energy, the wind turbine integrally for the period in question is assumed to produce the required amount of energy. For the generality of consideration, we have introduced the relative values of the required energy, relative energy produced by the wind turbine and the diesel generator and relative storage capacity by normalizing them to the swept area of the wind wheel. The paper shows the effect of the average wind speed over the period on the energy characteristics of the system (wind turbine + diesel generator + consumer). It was found that the wind turbine energy produced, wind turbine energy used by the consumer, fuel consumption, and fuel economy depend (close to cubic dependence) upon the specified average wind speed. It was found that, for the same system with a limited amount of required energy and high average wind speed over the period, the wind turbines with lower generator power and smaller wind wheel radius use wind energy more efficiently than the wind turbines with higher generator power and larger wind wheel radius at less average wind speed. For the system (wind turbine + diesel generator + energy storage + consumer) with increasing average speed for a given amount of energy required, which in general is covered by the energy production of wind turbines for the period, the maximum size capacity of the storage device decreases. With decreasing the energy storage capacity, the influence of the random nature of the change in wind speed decreases, and at some values of the relative capacity, it can be neglected.

scholarly journals Analysis of Performance of the Wind-Driven Pulverizing Aerator Based on Average Wind Speeds in the Conditions of Góreckie Lake

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2796
Author(s):  
Andrzej Osuch ◽  
Ewa Osuch ◽  
Stanisław Podsiadłowski ◽  
Piotr Rybacki
Keyword(s):  
Mathematical Model ◽  
Wind Speed ◽  
Water Pump ◽  
Average Wind Speed ◽  
Flow Rates ◽  
Wind Speeds ◽  
Average Wind ◽  
Flow Through ◽  
Analysis Of Performance ◽  
Research Period

In the introduction to this paper, the characteristics of Góreckie lake and the construction and operation of the wind-driven pulverizing aerator are presented. The purpose of this manuscript is to determine the efficiency of the pulverizing aerator unit in the windy conditions of Góreckie Lake. The efficiency of the pulverization aerator depends on the wind conditions at the lake. It was necessary to conduct thorough research to determine the efficiency of water flow through the pulverization segment (water pump). It was necessary to determine the rotational speed of the paddle wheel, which depended on the average wind speed. Throughout the research period, measurements of hourly average wind speed were carried out. It was possible to determine the efficiency of the machine by developing a dedicated mathematical model. The latest method was used in the research, consisting of determining the theoretical volumetric flow rates of water in the pulverizing aerator unit, based on average hourly wind speeds. Pulverization efficiency under the conditions of Góreckie Lake was determined based on 6600 average wind speeds for spring, summer and autumn, 2018. Based on the model, the theoretical efficiency of the machine was calculated, which, under the conditions of Góreckie Lake, amounted to 75,000 m3 per year.

scholarly journals Rapid coral mortality following unusually calm and hot conditions on Iriomote, Japan

F1000Research ◽  
2018 ◽  
Vol 6 ◽  
pp. 1728 ◽  
Author(s):  
Andrew H Baird ◽  
Sally A. Keith ◽  
Erika Woolsey ◽  
Ryuta Yoshida ◽  
Tohru Naruse
Keyword(s):  
Water Movement ◽  
Sea Surface ◽  
Bleaching Event ◽  
Coral Mortality ◽  
Average Wind Speed ◽  
Common Cause ◽  
Wind Speeds ◽  
Average Wind ◽  
The Mean ◽  
Low Wind Speeds

Coral bleaching can be induced by many different stressors, however, the most common cause of mass bleaching in the field is higher than average sea surface temperatures (SST). Here, we describe an unusual bleaching event that followed very calm sea conditions combined with higher than average SST. Patterns of mortality differed from typical bleaching in four ways: 1) mortality was very rapid; 2) a different suite of species were most affected; 3) tissue mortality in Acropora spp. was often restricted to the center of the colony; 4) the event occurred early in summer. The two weeks prior to the event included 8 days where the average wind speed was less than 3 ms-1. In addition, SSTs in the weeks preceding and during the event were 1.0-1.5°C higher than the mean for the last 30 years. We hypothesize that this unusual bleaching event was caused by anoxia resulting from a lack of water movement induced by low wind speeds combined with high SST.

Blade Design Criteria to Compensate the Flow Curvature Effects in H-Darrieus Wind Turbines

2014 ◽  
Author(s):  
Francesco Balduzzi ◽  
Alessandro Bianchini ◽  
Riccardo Maleci ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari
Keyword(s):  
Wind Turbines ◽  
Scale Effects ◽  
Medium Size ◽  
Design Criteria ◽  
Wind Speeds ◽  
Curvature Effects ◽  
Average Wind ◽  
Energy Scenario ◽  
Flow Curvature ◽  
Real Flow

Darrieus wind turbines are experiencing a renewed interest in the wind energy scenario, in particular whenever small and medium-size installations are considered. In these contexts, the average wind speeds are generally quite low due to scale effects and therefore the most exploited design choices for the turbines are the H-shape configuration, as the entire blade can take advantage of the maximum rotational radius, and high chord to radius ratios, in order to ensure suitable Reynolds numbers on the airfoils. By doing so, the aerodynamic effects induced by the motion of the airfoils in a curved flowpath become more evident and the airfoils themselves have to be designed to compensate these phenomena if conventional design tools based on the BEM theory are used. In this study, fully unsteady 2D simulations were exploited to analyze a three-bladed H-Darrieus wind turbine in order to define the real flow structure and its effects on the turbine performance; in detail, the influence of both the virtual camber and the virtual incidence were investigated. CFD results were supported by experimental data collected on full-scale models reproducing two different airfoil mountings. Finally, the proper design criteria to compensate these phenomena are proposed and their benefits on a conventional simulation with a BEM approach are discussed.

scholarly journals Formation and distribution of sea-surface microlayers

2010 ◽  
Vol 7 (4) ◽  
pp. 5719-5755 ◽  
Author(s):  
O. Wurl ◽  
E. Wurl ◽  
L. Miller ◽  
K. Johnson ◽  
S. Vagle
Keyword(s):  
Wind Speed ◽  
Primary Production ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind ◽  
The Pacific ◽  
Sea Surface Microlayer ◽  
Natural Surfactants

Abstract. Results from a study of surfactants in the sea-surface microlayer (SML) in different regions of the ocean (subtropical, temperate, polar) suggest that this interfacial layer between the ocean and atmosphere covers the ocean's surface to a significant extent. Threshold values at which primary production acts as a significant source of natural surfactants have been derived from the enrichment of surfactants in the SML relative to underlying water and local primary production. Similarly, we have also derived a wind speed threshold at which the SML is disrupted. The results suggest that surfactant enrichment in the SML is typically greater in oligotrophic regions of the ocean than in more productive waters. Furthermore, the enrichment of surfactants persisted at wind speeds of up to 10 m s−1 without any observed depletion above 5 m s−1. This suggests that the SML is stable enough to exist even at the global average wind speed of 6.6 m s−1. Global maps of primary production and wind speed are used to estimate the ocean's SML coverage. The maps indicate that wide regions of the Pacific and Atlantic Oceans between 30° N and 30° S are more significantly affected by the SML than northern of 30° N and southern of 30° S due to higher productivity (spring/summer blooms) and wind speeds exceeding 12 m s−1 respectively.

scholarly journals The super-turbine wind power conversion paradox: using machine learning to reduce errors caused by Jensen's inequality

2019 ◽  
Vol 4 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Tyler C. McCandless ◽  
Sue Ellen Haupt
Keyword(s):  
Machine Learning ◽  
Standard Deviation ◽  
Wind Speed ◽  
Wind Power ◽  
Power Conversion ◽  
Jensen’S Inequality ◽  
Jensen's Inequality ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Abstract. Wind power is a variable generation resource and therefore requires accurate forecasts to enable integration into the electric grid. Generally, the wind speed is forecast for a wind plant and the forecasted wind speed is converted to power to provide an estimate of the expected generating capacity of the plant. The average wind speed forecast for the plant is a function of the underlying meteorological phenomena being predicted; however, the wind speed for each turbine at the farm is also a function of the local terrain and the array orientation. Conversion algorithms that assume an average wind speed for the plant, i.e., the super-turbine power conversion, assume that the effects of the local terrain and array orientation are insignificant in producing variability in the wind speeds across the turbines at the farm. Here, we quantify the differences in converting wind speed to power at the turbine level compared with a super-turbine power conversion for a hypothetical wind farm of 100 2 MW turbines as well as from empirical data. The simulations with simulated turbines show a maximum difference of approximately 3 % at 11 m s−1 with a 1 m s−1 standard deviation of wind speeds and 8 % at 11 m s−1 with a 2 m s−1 standard deviation of wind speeds as a consequence of Jensen's inequality. The empirical analysis shows similar results with mean differences between converted wind speed to power and measured power of approximately 68 kW per 2 MW turbine. However, using a random forest machine learning method to convert to power reduces the error in the wind speed to power conversion when given the predictors that quantify the differences due to Jensen's inequality. These significant differences can lead to wind power forecasters overestimating the wind generation when utilizing a super-turbine power conversion for high wind speeds, and indicate that power conversion is more accurately done at the turbine level if no other compensatory mechanism is used to account for Jensen's inequality.

Extreme winds in a WRF downscaling for the SAM-22 CORDEX domain for the 1979-2018 Historical Period

2021 ◽  
Author(s):  
Natalia Pillar da Silva ◽  
Rosmeri Porfírio da Rocha ◽  
Natália Machado Crespo ◽  
Ricardo de Camargo ◽  
Jose Antonio Moreira Lima ◽  
...  
Keyword(s):  
Wind Speed ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Horizontal Resolution ◽  
Historical Period ◽  
Climate Projections ◽  
Wind Speeds ◽  
Extreme Wind ◽  
Wind Events ◽  
Extreme Winds

<p>This study aims to evaluate how extreme winds (above the 95th percentile) are represented in a downscaling using the regional model WRF over the CORDEX South American domain in an approximate 25 km (0.22 degrees) horizontal resolution, along with CFSR as input. The main focus of the analysis resides over the coastal Brazilian region, given a large number of offshore structures from oil and gas industries subject to impact by severe events. Model results are compared with a reanalysis product (ERA5),  estimates from satellites product (Cross-Calibrated Multi-Platform Wind Speed), and available buoy data (Brazilian National Buoy Project). Downscaling results from WRF show an underestimation of maximum and extreme wind speeds over the region when compared to all references, along with overestimation in the continental areas. This directly impacts results for extreme value estimation for a larger return period and severity evaluation of extreme wind events in future climate projections. To address this, a correction procedure based on the linear relationship between severe wind from satellite and model results is applied. After linearly corrected, the extreme and maximum wind speed values increase and errors in the representation of severe events are reduced in the downscaling results.</p>

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