Wind Energy and the Turbulent Nature of the Atmospheric Boundary Layer

Wind turbines operate in the atmospheric boundary layer, where they are exposed to the turbulent atmospheric flows. As the response time of wind turbine is typically in the range of seconds, they are affected by the small scale intermittent properties of the turbulent wind. Consequently, basic features which are known for small-scale homogeneous isotropic turbulence, and in particular the well-known intermittency problem, have an important impact on the wind energy conversion process. We report on basic research results concerning the small-scale intermittent properties of atmospheric flows and their impact on the wind energy conversion process. The analysis of wind data shows strongly intermittent statistics of wind fluctuations. To achieve numerical modeling a data-driven superposition model is proposed. For the experimental reproduction and adjustment of intermittent flows a so-called active grid setup is presented. Its ability is shown to generate reproducible properties of atmospheric flows on the smaller scales of the laboratory conditions of a wind tunnel. As an application example the response dynamics of different anemometer types are tested. To achieve a proper understanding of the impact of intermittent turbulent inflow properties on wind turbines we present methods of numerical and stochastic modeling, and compare the results to measurement data. As a summarizing result we find that atmospheric turbulence imposes its intermittent features on the complete wind energy conversion process. Intermittent turbulence features are not only present in atmospheric wind, but are also dominant in the loads on the turbine, i.e. rotor torque and thrust, and in the electrical power output signal. We conclude that profound knowledge of turbulent statistics and the application of suitable numerical as well as experimental methods are necessary to grasp these unique features (...)Comment: Accepted by the Journal of Turbulence on May 17, 201

High speed PIV measurements of an adaptive camber airfoil under highly gusty inflow conditions

Studies of the impact of gusty inflow on an adaptive camber airfoil were performed. The adaptive camber airfoil was developed at the TU Darmstadt and uses a mechanically coupled leading and trailing edge for passive load reduction. In the present study wind tunnel experiments were performed with tailored inflow generated by means of an active grid. The main goal is the investigation of dynamic loads on such a wind turbine blade and the resulting aerodynamics around it. Therefore, temporal highly resolved PIV measurements at the suction side of the airfoil were performed. To link the local measured aerodynamics to global forces, force balances were used

Child and Adolescent Mental Health During the COVID-19 Pandemic: Results of the Three-Wave Longitudinal COPSY Study

Purpose The German population-based longitudinal COVID-19 and Psychological Health study monitors changes in health-related quality of life (HRQoL) and mental health of children and adolescents during the COVID-19 pandemic and identifies vulnerable groups. Methods A nationwide, population-based survey was conducted in May 2020 to June 2020 (Wave 1), December 2020 to January 2021 (Wave 2), and September 2021 to October 2021 (Wave 3). In total, n = 2,097 children and adolescents aged 7–17 years were investigated using measures to assess HRQoL (KIDSCREEN-10), mental health problems (SDQ), anxiety (SCARED), depressive symptoms(PHQ-2), and psychosomatic complaints(HBSC-SCL). Results The prevalence of low HRQoL increased from 15% prepandemic to 40% and 48% in Waves 1 and 2 and improved slightly to 35% in Wave 3 (all differences significant). Similarly, overall mental health problems increased from 18% prepandemic to 29% in Wave 1 and 31% in Wave 2 to 28% in Wave 3 (all differences significant, except Wave 3 vs. 2), anxiety increased from 15% prepandemic to 24% and 30% in Waves 1 and 2 and was still 27% in Wave 3. Depressive symptoms increased from 10% prepandemic to 11% and 15% in Waves 1 and 2 and were 11% in Wave 3. A group with low parental education, restricted living conditions, migration background, and parental mental health problems was at significantly increased risk of HRQoL and mental health impairments. Discussion The prevalence of low HRQoL, mental health problems, and anxiety has been elevated throughout the pandemic. Thus, mental health promotion, prevention, and intervention strategies need to be implemented to support adolescents–particularly those at risk.Peer Reviewe

Blind test comparison on the wake behind a yawed wind turbine

This article summarizes the results of the Blind test 5 workshop, which was held in Visby, Sweden, in May 2017. This study compares the numerical predictions of the wake flow behind a model wind turbine operated in yaw to experimental wind tunnel results. Prior to the workshop, research groups were invited to predict the turbine performance and wake flow properties using computational fluid dynamics (CFD) methods. For this purpose, the power, thrust, and yaw moments for a 30° yawed model turbine, as well as the wake's mean and turbulent streamwise and vertical flow components, were measured in the wind tunnel at the Norwegian University of Science and Technology (NTNU). In order to increase the complexity, a non-yawed downstream turbine was added in a second test case, while a third test case challenged the modelers with a new rotor and turbine geometry.Four participants submitted predictions using different flow solvers, three of which were based on large eddy simulations (LES) while another one used an improved delayed detached eddy simulation (IDDES) model. The performance of a single yawed turbine was fairly well predicted by all simulations, both in the first and third test cases. The scatter in the downstream turbine performance predictions in the second test case, however, was found to be significantly larger. The complex asymmetric shape of the mean streamwise and vertical velocities was generally well predicted by all the simulations for all test cases. The largest improvement with respect to previous blind tests is the good prediction of the levels of TKE in the wake, even for the complex case of yaw misalignment. These very promising results confirm the mature development stage of LES/DES simulations for wind turbine wake modeling, while competitive advantages might be obtained by faster computational methods.</p

The German Young Olympic Athletes' Lifestyle and Health Management Study (GOAL Study): design of a mixed-method study

<p>Abstract</p> <p>Background</p> <p>In order to perform at top levels, elite athletes have to both protect and risk their health at the same time. Adolescent elite athletes have the additional challenge of coping with substantial physical, psychological and social transformations. The contradictory phenomenon of protecting and risking the adolescent athletes' health in sports challenges the development of health promotion and protection strategies. The GOAL Study (German Young Olympic Athletes' Lifestyle and Health Management Study) analyzes the individual and organizational management of health in adolescent elite sports.</p> <p>Methods/design</p> <p>We combine quantitative and qualitative approaches in a mixed-method study. This allows us to gather a broad range of representative information on squad athletes from all Olympic disciplines as well as in-depth information on four selected Olympic disciplines (artistic gymnastics, biathlon, handball and wrestling). Within the quantitative section we attempt to identify the young athletes' health and nutrition behavior, their subjective health state and their lay health representations, health-related social networks, and structures of medical attendance. 1138 national team level athletes born between 1992 and 1995 from 51 Olympic disciplines responded to the questionnaire (response rate: 61,75%). The qualitative section investigates the meaning and relevance of health and nutrition within the athletes' sports specific surroundings, the impact of biographic backgrounds on individual health behavior, and sports specific cultures of health, nutrition and risk. We interviewed 24 athletes and 28 coaching and medical experts, and carried out 14 multi-day participant observations at training sessions and competitions.</p> <p>Conclusions</p> <p>The studies' results will serve as the basis for developing tailored health promotion strategies to be in cooperation with German elite sports associations.</p

Change in the direct cost of treatment for children and adolescents with hyperkinetic disorder in Germany over a period of four years

Abstract Background In many developed countries, the treatment of hyperkinetic disorder (or ADHD) consumes a considerable amount of resources. The primary aim of this study was to determine change in the direct cost of treatment for children and adolescents with hyperkinetic disorder in Germany over time, and compare the cost with the cost of treatment for two physical disorders: epilepsy and asthma. Methods The German Federal Statistical Office provided data on the direct cost of treating hyperkinetic disorder, epilepsy and asthma in Germany for 2002, 2004, and 2006. The direct costs of treatment incurred by hyperkinetic disorder in these years were compared with those incurred by epilepsy and asthma. Results The total direct cost of treatment for the hyperkinetic disorder was € 177 million in 2002, € 234 million in 2004, and € 341 million in 2006. The largest proportion of the cost was incurred by the age group Conclusion The direct cost of treatment for hyperkinetic disorder in the age group < 15 years increased considerably between 2002 and 2006. Over the same period of time and for the same age group, expenditure for epilepsy and asthma was more or less constant. The increase in expenditure for the treatment of hyperkinetic disorder may be due to increasing demand for diagnostic and therapeutic services and improved availability of such services. The study is limited by the difficulty of obtaining consistent data on the direct cost of treatment for both physical and psychiatric disorders in Germany.</p

Juvenile obesity and its association with utilisation and costs of pharmaceuticals - results from the KiGGS study

<p>Abstract</p> <p>Background</p> <p>According to a national reference, 15% of German children and adolescents are overweight (including obese) and 6.3% are obese. An earlier study analysed the impact of childhood overweight and obesity on different components of direct medical costs (physician, hospital and therapists). To complement the existing literature for Germany, this study aims to explore the association of body mass index (BMI) with utilisation of pharmaceuticals and related costs in German children and adolescents.</p> <p>Methods</p> <p>Based on data from 14, 836 respondents aged 3-17 years in the German Interview and Examination Survey for Children and Adolescents (KiGGS), drug intake and associated costs were estimated using a bottom-up approach. To investigate the association of BMI with utilisation and costs, univariate analyses and multivariate generalised mixed models were conducted.</p> <p>Results</p> <p>There was no significant difference between BMI groups regarding the probability of drug utilisation. However, the number of pharmaceuticals used was significantly higher (14%) for obese children than for normal weight children. Furthermore, there was a trend for more physician-prescribed medication in obese children and adolescents. Among children with pharmaceutical intake, estimated costs were 24% higher for obese children compared with the normal weight group.</p> <p>Conclusions</p> <p>This is the first study to estimate excess drug costs for obesity based on a representative cross-sectional sample of the child and adolescent population in Germany. The results suggest that obese children should be classified as a priority group for prevention. This study complements the existing literature and provides important information concerning the relevance of childhood obesity as a health problem.</p