Rüzgar Türbinlerinin Mikro Düzeyde Yer Seçimi için Navier- Stokes Akış Çözücüsünün Topografik Yapısız Çözüm Ağlarında Geliştirilmesi ve Kullanılması

TÜBİTAK MAG Proje15.05.2015Bu çalışmada türbülanslı atmosferik akış çözümlerinin elde edilmesi amacıyla ODTÜ Havacılık ve Uzay Mühendisliği Bölümünde geliştirilmekte olan, paralel hesaplama ortamında çalışabilen 3 boyutlu Navier-Stokes çözücü HYP3D, Mezo ölçekli meteorolojik tahmin yazılımı WRF ile akuple edilerek yüksek çözünürlüklü topografya üzerinde uzun dönemli rüzgar akış alanları ve rüzgar enerji potansiyeli hesaplanmıştır. Numerik çalışmalar bir rüzgar santralinin ve uzun dönemli atmosferik gözlem verilerinin olduğu Mersin-Mut bölgesinde uygulanmış, ve gözlem verileri ile doğrulanmıştır. Bu çözüm bölgesi için yüksek çözünürlüklü (1,5 arcsec, 30m) topografya haritası (DEM) temin edilmiştir. Bu topoğrafya verisi ile yüksek çözünürlüklü, yapılı ve hibrit çözüm ağları oluşturulmuştur. HYP3D çözümleri için gerekli sınır koşulları, yaygın olarak kullanılan, açık kaynak kodlu meteorolojik hava tahmin yazılımı WRF ile 1km çözünürlüklü çözüm ağında elde edilen akış çözümlerinden sağlanmıştır. Akuple çözümler için öncelikle seçilen dar bölgeyi içine alan daha büyük bir bölge için WRF ile uzun dönemli çözümler elde edilmiştir. WRF çözümlerinde kullanılan global ölçekli başlangıç ve sınır koşulları NCEP (National Centers for Environmental Prediction) Final Analysis (FNL from GFS) (ds083.2 dataset) veri setinden temin edilmiştir. HYP3D çözüm ağının dış hücreleri için gerekli olan zamana bağłı sınır koşulları ise düşük çözünürlüklü WRF çözümlerinden interpolasyon yöntemiyle elde edilmiştir. HYP3D .Navier-Stokes akış çözücüsünde ve meteorolojik tahmin yazılımı WRF 'de kullanılan çözüm ağ yapılarının ve çözünürlüklerin farklı olması sebebiyle, WRF ile hesaplanan akış değişkenlerinin Navier-Stokes çözücüsünün yeryüzeyine yakın bazı düğüm noktalarına interpolasyon yapılamamaktadır. Bu çalışmada düşük çözünürlüklü WRF çözüm ağı ile yüksek çözünürlüklü Navier-Stokes çözüm ağının yeryüzüne yakın bölgelerde yaklaşık olarak eşleştirilmesi için iki farklı yöntem denenmiştir. HYP3D yazılımında zamana bağlı sınır koşullarının veri dosyalarından okunarak paralel hesaplama ortamında uygulanması sağlanmıştır. HYP3D'de kullanılan türbülans modeli ile yüzey pürüzlülüğünün etkin bir şekilde modellenebilmesi için var olan Runge-Kutta açık (explicit) çözüm yöntemine ek olarak Simetrik Gauss-Seidel nokta kapalı (point implicit) çözüm yöntemi geliştirilmiş, performans değerlendirilmesi yapılmıştır. WRF ile akuple edilen yüksek çözünürlüklü Navier-Stokes çözümleri bir yıllık bir zaman aralığı için elde edilmiştir. Bu akış çözümlerinde elde edilen yüksek çözünürlüklü rüzgar alanları, rüzgar hızının eşdeğer çizgileri, Weibull dağılımları ve rüzgar gülü grafikleri ile değerlendirilmiştir. Akış değişkenleri, 7 gerçek gözlem verileri ve WRF sonuçları ile kıyaslanmış, paralel hesaplamalar için performans değerlendirmesi yapılmıştır. Ayrıca güç üretim eğrileri verilen örnek rüzgar türbinleri için yıllık enerji üretim haritaları elde edilmiştir

OpenFOAM ile akuple numerik hava tahmin modeli, WRF kullanılarak zamana bağlı atmosferik akış çözümleri.

Ways to predict wind energy potential and energy generation accurately are sought in many applications such as the wind turbine siting and the short term wind power production estimation. Current wind energy prediction models are based on the statistical analysis of long term observation data and the reconstruction of average wind fields by means of numerical tools. Even if computational fluid dynamics tools based on Navier-Stokes solutions are employed for sectoral wind fields, the reconstruction of wind fields according to prevailing wind speeds and directions are, in general, not accurate for wind field predictions on complex terrains.On the other hand, numerical weather prediction software such as WRF, in which the unsteady atmospheric physics are taken into account, provides time dependent atmospheric flow field solutions, but due to the low resolution and the pressure based vertical coordinate system wind field predictions are inaccurate near ground in complex terrains. In this work, unsteady atmospheric flows are computed by a coupled solution methodology. Atmospheric flow solutions based on the weather prediction model, WRF, on a low resolution grid provide the unsteady boundary conditions for OpenFOAM solutions on high resolution terrain fitted grids. The usage of WRF predictions as boundary conditions accounts partially for the physical processes such as solar radiation, precipitation, surface heating and the resulting diurnal cycle. OpenFOAM solutions with the high resolution topography and computational grid, and a spatially varying roughness model capture complex terrain effects such as flow separation, recirculation, and reattachment zones. The OpenFOAM solutions coupled with WRF are performed in parallel. A post-processing tool is also developed to extract the wind field data from the coupled OpenFOAM solutions at any given altitude, and to estimate the distributions of wind power density and wind energy generation by time integration along the unsteady flow solution. The coupled flow solutions are compared with the time series wind speed and direction data obtained from a meteorological measurement tower, Met-mast. It is shown that the coupled flow solutions developed improve the time dependent wind field predictions of WRF by about 12% with respect to the observation data which corresponds to about 40% improvement on wind power production estimations.Ph.D. - Doctoral Progra

Arazi modelleme ve meteorolojik verilere dayalı atmosferik akış çözümleri.

In this study, atmospheric and turbulent flow solutions are obtained using meteorological flowfield and topographical terrain data in high resolution. The terrain topology of interest, which may be obtained in various resolution levels, is accurately modeled using structured or unstructured grids depending on whether high-rise building models are present or not. Meteorological weather prediction software MM5, is used to provide accurate and unsteady boundary conditions for the solution domain. Unsteady turbulent flow solutions are carried out via FLUENT with the help of several User Defined Functions developed. Unsteady flow solutions over topographical terrain of METU campus are computed with 25m x 25m x 15m resolution using structured grids. These FLUENT solutions are compared with the MM5 solutions. Also, the accuracy of the boundary layer velocity profiles is assessed. Finally, effects of surface roughness model extracted from MM5 for the region of interest is investigated. In addition, unsteady flow solutions over METU campus are repeated in presence of high-rise building models using unstructured grids with resolution varying from 5 meters around buildings to 80 meters further away. The study shows that unsteady, turbulent flow solutions can be accurately obtained using low resolution atmospheric weather prediction models and high resolution Navier-Stokes solutions over topographical terrains.M.S. - Master of Scienc

Development of openFOAM - WRF coupling methodolgy for wind power production estimations

The objective of the this study is the development of a tool to predict daily wind energy production potentialaccurately for a region of interest. For that purpose, mesoscale weather prediction model WRF (WeatherResearch and Forecast) is coupled with the Opensource CFD solver OpenFOAM via using low resolutionWRF data as unsteady and spatially varying boundary condtions in the CFD solver OpenFOAM. For thatpurpose, a new boundary condition class (timevaryingmixed) in OpenFOAM was developed and utilized. 12hour WRF coupled OpenFOAM solutions are performed in Mersin/Mut region in Turkey where a met-mastis located for validation purposes. Unlike other methodologies, capability of time resolved energy predictionis attained in this study and also, observation data is not a must. As time is of essence for predictions,paralleling the process is crucial. Studies for the parallelization of the process is ongoi

Openfoam'un wrf ile akuple edilmesi ve rüzgar potansiyeli tahmini

Bu projede a ̧cık kaynaklı Navier-Stokes tabanlı akı ̧s ̧c ̈oz ̈uc ̈u OpenFOAM ile orta ̈ol ̧cekli(meso-scale) hava tahminlerinde kullanılan WRF yazılımı akuple edilerek y ̈uksek ̧c ̈oz ̈un ̈url ̈ukl ̈u,mikro ̈ol ̧cekli (micro-scale) atmosferik akı ̧s ̧c ̈oz ̈um y ̈ontemleri geli ̧stirilmi ̧stir. WRF global havatahminlerinde kullanılan, g ̈ozlem verileriyle s ̈urekli bir ̧sekilde g ̈uncellenen d ̈u ̧s ̈uk ̧c ̈oz ̈un ̈url ̈ukl ̈u,yery ̈uz ̈un ̈u e ̧sbasın ̧c seviyeleri ile modelleyen global bir atmosferik akı ̧s ̧c ̈oz ̈uc ̈us ̈ud ̈ur.OpenFOAM ise a ̧cık kaynak olarak geli ̧stirilen, genel ama ̧clı bir hesaplamalı akı ̧skanlardinami ̆gi, HAD (CFD) yazılımıdır. WRF’ in ba ̧sarısız oldu ̆gu karma ̧sık topografyalarda yereyakın b ̈olgelerde, HAD ̧c ̈oz ̈uc ̈ulerin daha do ̆gru ̧c ̈oz ̈um yaptı ̆gı bilinmektedir. Bu sebepleOpenFOAM ve WRF’ in akuple edilmesi tahminlerde iyile ̧stirme sa ̆glayacaktır. D ̈u ̧s ̈uk ̧c ̈oz ̈un ̈url ̈ukl ̈u WRF ile tahmin edilen global atmosferik akı ̧s ̧c ̈oz ̈umlerinden alınan akı ̧sbilgilerinin, y ̈uksek ̧c ̈oz ̈un ̈url ̈ukl ̈u dar b ̈olgelerdeki OpenFOAM ̧c ̈oz ̈umlerinde ba ̧slangı ̧c ve sınırko ̧sulları olarak kullanılmasıyla OpenFOAM ve WRF akuple bir ̧sekilde ̧calı ̧stırılmı ̧stır.Mersin-Mut b ̈olgesinde 24 saatlik zamana ba ̆glı (unsteady), t ̈urb ̈ulanslı ̧c ̈oz ̈umler yapılmı ̧stır.Y ̈ontemin paralel ̧calı ̧stırılması i ̧cin gerekli ara ̧clar geli ̧stirilmi ̧s ve ̧c ̈oz ̈um zamanında ̈onemliiyile ̧stirmeler sa ̆glanmı ̧stır. Geli ̧stirilen akuple ̧c ̈oz ̈um y ̈ontemi mikro ̈ol ̧cekli r ̈uzgar enerjipotansiyelinin belirlenmesinde, r ̈uzgar t ̈urbinleri i ̧cin yer se ̧ciminde (micro-siting) ve r ̈uzgart ̈urbinlerinin ileriye d ̈on ̈uk, kısa s ̈ureli (g ̈unl ̈uk/haftalık) enerji ̈uretim tahminlerinin eldeedilebilmesinde kullanılabilecekti

OpenFOAM solutions coupled with WRF for wind power estimation

The open source flow solver OpenFOAM is coupled with the mesoscale weather prediction software WRF in order to predict the atmospheric flows in complex terrains more accurately and to predict the daily wind energy production potential accurately. The low resolution, unsteady WRF solution provides the spatially varying unsteady boundary conditions for OpenFOAM solutions on high resolution terrain fitted viscous grids. Coupled OpenFOAM solutions are successfully obtained for Mersin/Mut region in Turkey. It is shown that the coupled solutions agree with the WRF solutions in general and compare well with the wind mast data available

Validation of Parallel WRF Downscaling Methodology using OpenFOAM

The main objective of this study is to obtain real-time atmospheric flow solutions using open source CFD solver OpenFOAM coupled with Numerical Weather Prediction (NWP) model; Weather Research Forecast (WRF). NWP can take moist convection, land surface parameterization, atmospheric boundary layer physics into account, but wind flow features finer than 1 km aren't captured by the turbulence physics of such models. CFD simulations, however, have proved to be useful at capturing the details of smaller scales due to a finer scale topography. Moreover, using the WRF weather prediction data as unsteady and spatially varying BCs for the CFD solution may prove to be one of the most realistic representations for the atmospheric flow field, and also allows daily power production estimations. Coupling the mesoscale weather prediction model WRF (Weather Research and Forecast) with the open source CFD solver OpenFOAM is done via using low resolution WRF data as unsteady and spatially varying boundary conditions for the OpenFOAM domain.For this purpose, a new unsteady and spatially varying boundary condition class (timeVaryingMixed) that switches between Neumann and Dirichlet depending on the flow is entering or exiting the domain to use the WRF data as boundary conditions without convergence issues for continuity, is developed.Due to real-time prediction requirement, parallelization of the process is of utmost importance. But the developed boundary condition class 'timeVaryingMixed' cannot be run in parallel using OpenFOAM's domain decomposition tool decomposePar as the indexes of cells change when the domainis decomposed. Parallelization of the process is done and made automatic using METIS to optimize the number of partitionboundaries, even when all the cells that arein neighbourhoodof the developed boundary condition timeVaryingMixed, are owned by 1 processor. Details about the methodology and parallelization of process will be given in the final paper.Unsteady OpenFOAM solutions coupled with WRF are performed using the methodology on high resolution stretching structured grids seen in Figure 2. High resolution (1.5 arcsec) ASTER GDEM topographical data is used to create the topography in order to capture the viscous effects which dominates the flow characteristics at the surface layer of the atmosphere where majority of the wind turbines reside. Simulations in Alaiz Mountain (Spain) are carried out and validation studies using the met-mast data from the region are done at the met-mast location at 5 different heights(118, 102, 90, 78, 40 meters) above the ground. As a preliminary result, time-series wind speed data at118and 40meters above ground is given in Figure 1.Results show a drastic improvement over the WRF results especially in thevicinity of the ground

Design optimization of a 2-d scramjet inlet

A generic 2-D scramjet inlet is analyzed with SU2 software. Accuracy of three turbulence models are compared and a mesh dependence study is performed for the case. Results are compared favorably with experimental data from Idris et al. (2014). The geometry is planned to be optimized by using the adjoint method in the full paper