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This report describes the work done in the project ”EFP07- Metoder til kortlægning af vindforhold i komplekst terræn” granted by the Danish Energy Agency. References to reports published during the project are given. The main purpose of the project has been to investigate micro-scale wind conditions in complex terrain using “remote-sensing” techniques and CFD computations and validate these using measurements. The work done in the project can be divided into three parts: 1. “The Bolund Experiment” is a measuring campaign performed on a small hill located near Risø DTU. The experiment provides data for validating CFD models. 2. “The blind comparison” is a comparison of more than 50 different micro-scale models and the Bolund measurements. 3. “The Benakanahalli Experiment” is a large-scale measuring campaign that provides a complex validation case for micro-scale models. This report describes the work done in the project ”EFP07- Metoder til kortlægning af vindforhold i komplekst terræn” granted by the Danish Energy Agency. References to reports published during the project are given. The main purpose of the project has been to investigate micro-scale wind conditions in complex terrain using “remote-sensing” techniques and CFD computations and validate these using measurements. The work done in the project can be divided into three parts: 1. “The Bolund Experiment” is a measuring campaign performed on a small hill located near Risø DTU. The experiment provides data for validating CFD models. 2. “The blind comparison” is a comparison of more than 50 different micro-scale models and the Bolund measurements. 3. “The Benakanahalli Experiment” is a large-scale measuring campaign that provides a complex validation case for micro-scale models.

The atmospheric boundary layer flow over different types of terrain is studied through simulations made with the finite volume CFD code of Ellipsys 2D and 3D. The simulations are compared to measurements made at the Høvsøre test site and over the hill of Askervein.The primary objective of these investigations is to find out, how the wind under neutral atmospheric stratification is affected by changes in the surface roughness.In both cases of Høvsøre and Askervein, an upstream roughness change is seen to have a significant influence on the observed flow. General empirical expressions are suggested for describing the flow after a change in the surface roughness. The derivation of these expressions is based on a range of simulations of flows over flat terrain with different types of roughness changes.The derived expressions show good agreement with simulations and could, as intended, be used to define inlet conditions for flow simulations over terrain, where an upstream roughness change is thought to have an influence. More thorough experimental verification is however, thought necessary to make the expressions sufficiently reliable. The same goes for the simulations-based conclusions regarding the flow over Askervein.

The report describes the application of the correlation based transition model of of Menter et. al. [1, 2] to the cylinder drag crisis and the stalled flow over an DU-96-W-351 airfoil using the DES methodology. When predicting the flow over airfoils and rotors, the laminar-turbulent transition process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer on the wings or airfoils is handled by the turbulence model. The correlation based transition model has lately shown promising results, and the present paper describes the application of the model to predict the drag and shedding frequency for flow around a cylinder from sub to super-critical Reynolds numbers. Additionally, the model is applied to the flow around the DU-96 airfoil, at high angles of attack.

A new method for generating synthetic turbulence is presented. The method is intended for generating a turbulent velocity field with a fine spatial resolution but only covering a small moving part of the rotor area of a wind turbine. For this application the Mann and Sandia methods cannot be used because of the very high requirements for computer memory. In the present method the auto- and cross-correlation in all three directions is computed from analytical or empirical expressions and the auto- and cross-spectra are determined by using the Wiener-Khinchin relation. From the auto- and cross-spectra a realization of a velocity field is determined by factorization and Fourier transform as in the Sandia method. A new method for generating synthetic turbulence is presented. The method is intended for generating a turbulent velocity field with a fine spatial resolution but only covering a small moving part of the rotor area of a wind turbine. For this application the Mann and Sandia methods cannot be used because of the very high requirements for computer memory. In the present method the auto- and cross-correlation in all three directions is computed from analytical or empirical expressions and the auto- and cross-spectra are determined by using the Wiener-Khinchin relation. From the auto- and cross-spectra a realization of a velocity field is determined by factorization and Fourier transform as in the Sandia method.

The Bolund experiment is a measuring campaign performed in 2007 and 2008. The aim of the experiment is to measure the flow field around the Bolund hill in order to provide a dataset for validating numerical flow models. The present report gives an overview of the whole experiment including a description of the orography, the instrumentation used and of the data processing. The Actual measurements are available from a database also described.

Ungdomsliv er en bredt dækkende bog om de unge i Danmark i dag. Den kommer rundt om alle de vigtige sider af ungdomslivet: uddannelse og vejledning, arbejds-, firtids- og foreningsliv - og trænger ind i en række af ungdomslivets brændpunkter: ungdomskulturerne, kønsrelationerne, de sociale og etniske tilhørsforhold og de mange former for risikoadfærd.

'Spænd hjelmen' er et pilotprojekt, der belyser, hvordan unge forholder sig til og taler om arbejdsmiljø og risikoadfærd i arbejdet. Rapporten bygger på interviews med og feltarbejde blandt unge fra fem forskellige brancher: detailhandlen, industrien, hotel og restaurent, plejeområdet samt bygge og anlæg.

The present work addresses the validation of the implementation of the Menter, Langtry et al. γ - θ corrrelation based transition model [1, 2, 3] in the EllipSys2D code. Firstly the 2. order of accuracy of the code is verified using a grid refinement study for laminar, turbulent and transitional computations. Based on this, an estimate of the error in the computations is determined to be approximately one percent in the attached region. Following the verification of the implemented model, the model is applied to four airfoils, NACA64- 018, NACA64-218, NACA64-418 and NACA64-618 and the results are compared to measurements [4] and computations using the Xfoil code by Drela et al. [5]. In the linear pre stall region good agreement is observed both for lift and drag, while differences to both measurements and Xfoil computations are observed in stalled conditions.

An actuator disc model for the flow solver EllipSys (2D&3D) is proposed. It is based on a correction of the Rhie-Chow algorithm for using discreet body forces in collocated variable finite volume CFD code. It is compared with three cases where an analytical solution is known. An actuator disc model for the flow solver EllipSys (2D&3D) is proposed. It is based on a correction of the Rhie-Chow algorithm for using discreet body forces in collocated variable finite volume CFD code. It is compared with three cases where an analytical solution is known.

Wind turbines operate in the turbulent boundary layer of the atmosphere and due to the rotational sampling effect the blades experience a high level of turbulence [1]. In this project the effect of turbulence is investigated by large eddy simulations of the turbulent flow past a NACA 0015 airfoil at Reynolds number 1.6 million. The effect of increasing the turbulence intensity is investigated and the results are compared to measurements from a wind tunnel. By including the inflow turbulence the agreement with measurements is improved for some angles of attack. The results indicate that the free stream turbulence may trigger separation of the flow at angles of attack close to stall. Wind turbines operate in the turbulent boundary layer of the atmosphere and due to the rotational sampling effect the blades experience a high level of turbulence [1]. In this project the effect of turbulence is investigated by large eddy simulations of the turbulent flow past a NACA 0015 airfoil at Reynolds number 1.6 million. The effect of increasing the turbulence intensity is investigated and the results are compared to measurements from a wind tunnel. By including the inflow turbulence the agreement with measurements is improved for some angles of attack. The results indicate that the free stream turbulence may trigger separation of the flow at angles of attack close to stall.

Udgivelsesdato: december

Udgivelsesdato: juli

Artiklen handler om unges risikoadfærd. Den belyser hvordan risikoadfærd og -problematikker blandt unge er særligt knyttet til de faser i ungdomslivet, hvor individualiseringen for alvor presser sig på. En pædagogisk pointe er, at der er stor forskel på, hvor meget man skal oplyse om forskellige typer af risikoadfærd. Men samtidig betyder det meget, at institutioner ved hvordan de skal forholde sig til risikoadfærd blandt unge og at de har praksisser, der kan være med til at forebygge og inddæmme risikoadfærd. Udgivelsesdato: September

Udgivelsesdato: maj

For at fi nde ud af, hvor stor en andel skarverne tager af de småskrubber, som fi ndes i Ringkøbing Fjord, blev der indfanget, mærket og genudsat godt 6.000 småskrubber. Derefter blev der i kolonierne indsamlet omkring 2.000 gylp. Disse gylp, som skarverne producerer ét af i døgnet, består af ufordøjelige føderester inklusiv de anvendte fi skemærker. Undersøgelserne tyder på, at skarverne i det mindste i nogle forår kan tage en stor del af de 1 år gamle skrubber.

Rapporten offentliggør resultaterne af den første videnskabelige undersøgelse af pengespil blandt unge danskere mellem 12 og 17 år. Den beskæftiger sig med tre områder 1) Pengespiladfærd blandt unge, 2) Problemspiladfærd blandt unge og 3) Sammenhænge mellem unges risikoadfærd og trivsel samt deres penge- og problemspiladfærd.

Udgivelsesdato: december

Ved at fiske med et lille bundtrawl i Ringkøbing Fjord blev antal og udbredelse af skrubbeyngel, rødspætteyngel, sandkutling, hesterejer og strandkrabber fulgt fra 2003 til 2006. Sæsonvariationen for hver art er stor; for sandkutling er der f.eks. 25 gange så mange fi sk om efteråret som om foråret. Fiskeundersøgelserne viste, at skrubbebestanden er meget varierende og helt afhængig af indvandring af yngel fra Vesterhavet. Skrubbens livscyklus skitseres, ogfaktorer af betydning for skrubbernes tilstedeværelse i fjorden diskuteres

Udgivelsesdato: maj

Traditionally, rotor computations using CFD (Computational Fluid Dynamics) are performed assuming a uniform inflow with zero shear over the rotor disc. In the present work, time true simulations of a rotor in an atmospheric boundary layer are performed to investigate the unsteady effects due to variation of the mean velocity over the rotor disc. The main purpose of these computations are to provide new input to the BEM (Blade Element Momentum) type models used in most engineering codes, concerning the dynamic induction and an eventual phase shifting of the force response with respect to the variation of the inflow velocity over the rotor disc. The results show a clear disturbance of the flow upstream of the rotor and a pronounced phase lag in azimuth direction of the forces and the axial velocity seen by the blades.

Udgivelsesdato: September