Giorgio Crasto - Academia.edu (original) (raw)
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Papers by Giorgio Crasto
Journal of Physics: Conference Series, 2018
In the present study it is discussed a sensitivity analysis on input parameters of a CFD resource... more In the present study it is discussed a sensitivity analysis on input parameters of a CFD resource assessment methodology built on top of OpenFOAM 4.1, a well-known open source library for numerical fluid dynamics. RANS are solved for dry uncompressible air, the Atmospheric Boundary Layer is calculated without thermal effects (neutral conditions). It is highlighted how the control of a metric based upon a weighted root mean square error (wRMSE) of the local accelerations (speed ups) can guide the wind analyst in the design of the computational mesh and further numerical settings. Moreover, it will be quantified the wRMSE as a function of the distance to the measurement points. The parameters analysed are the horizontal extension of the model, the horizontal resolution within the refined area, which is covering the layout of the wind farm, three different versions of k-e turbulence closure and the number of directional sectors considered.
一般社団法人 日本教育心理学会, Mar 30, 1985
一般社団法人 日本教育心理学会, Mar 30, 1985
Se un uomo sogna da solo, il sogno rimane solo un sogno, ma se molti uomini sognano la stessa cos... more Se un uomo sogna da solo, il sogno rimane solo un sogno, ma se molti uomini sognano la stessa cosa, il sogno diventa realtà. Dom Helder Camara (1909-1999)
Wind Engineering, 2013
This paper is focusing on the wake modeling in large offshore wind farms. Over the sea the ambien... more This paper is focusing on the wake modeling in large offshore wind farms. Over the sea the ambient turbulence is much lower than onshore, wakes persist for long distances, mixing in a complex pattern. Hence an accurate evaluation of the wakes become crucial in the estimation both of the production and loads. Regarding loads the main effect of the turbines wakes is an increase of turbulence compared to the ambient one. A careful assessment of the wakes is therefore required when analyzing offshore wind farms. The approaches in estimating the wake losses go from simple theoretical or empirical laws to full rotor aerodynamic calculations; in between there is a range of intermediate calculations. Two approaches will be presented: the use of relative simple equations (also called analytical models) which are the standards in the wind resource assessment and a more accurate, but computationally more demanding, the actuator disc technique.
Single wake of a wind turbine over flat terrains is modeled with a finite-volume Computational Fl... more Single wake of a wind turbine over flat terrains is modeled with a finite-volume Computational Fluid Dynamics (CFD) Reynolds Averaged Navier-Stokes (RANS) solver. The RANS equations of an uncompressible flow are solved with a multigrid coupled ...
Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, host... more Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, hosted by the Poltecnico di Milano (POLIMI).
The independent comparison of three simulation codes to estimate the wind resource over complex t... more The independent comparison of three simulation codes to estimate the wind resource over complex terrains is performed in the present work. The three software are OpenFOAM, WindSim and ORFEUS: the first two are finite-volume codes solving nonlinear flow equations, while the third is a linearised spectral solver. In order to avoid possible biases, the three simulations were run by different groups with only the terrain characteristics and turbine positions available. In order to avoid errors due to the different turbine modelling approaches, no turbines were simulated, so that the focus here is on the free flow only. SCADA data were then used to validate the results and to assess the uncertainty of the simulations. The comparison is reasonably good for simple terrain configurations, while larger errors are present for terrains with severe mountainous features.
Journal of Physics: Conference Series, 2018
In the present study it is discussed a sensitivity analysis on input parameters of a CFD resource... more In the present study it is discussed a sensitivity analysis on input parameters of a CFD resource assessment methodology built on top of OpenFOAM 4.1, a well-known open source library for numerical fluid dynamics. RANS are solved for dry uncompressible air, the Atmospheric Boundary Layer is calculated without thermal effects (neutral conditions). It is highlighted how the control of a metric based upon a weighted root mean square error (wRMSE) of the local accelerations (speed ups) can guide the wind analyst in the design of the computational mesh and further numerical settings. Moreover, it will be quantified the wRMSE as a function of the distance to the measurement points. The parameters analysed are the horizontal extension of the model, the horizontal resolution within the refined area, which is covering the layout of the wind farm, three different versions of k-e turbulence closure and the number of directional sectors considered.
一般社団法人 日本教育心理学会, Mar 30, 1985
一般社団法人 日本教育心理学会, Mar 30, 1985
Se un uomo sogna da solo, il sogno rimane solo un sogno, ma se molti uomini sognano la stessa cos... more Se un uomo sogna da solo, il sogno rimane solo un sogno, ma se molti uomini sognano la stessa cosa, il sogno diventa realtà. Dom Helder Camara (1909-1999)
Wind Engineering, 2013
This paper is focusing on the wake modeling in large offshore wind farms. Over the sea the ambien... more This paper is focusing on the wake modeling in large offshore wind farms. Over the sea the ambient turbulence is much lower than onshore, wakes persist for long distances, mixing in a complex pattern. Hence an accurate evaluation of the wakes become crucial in the estimation both of the production and loads. Regarding loads the main effect of the turbines wakes is an increase of turbulence compared to the ambient one. A careful assessment of the wakes is therefore required when analyzing offshore wind farms. The approaches in estimating the wake losses go from simple theoretical or empirical laws to full rotor aerodynamic calculations; in between there is a range of intermediate calculations. Two approaches will be presented: the use of relative simple equations (also called analytical models) which are the standards in the wind resource assessment and a more accurate, but computationally more demanding, the actuator disc technique.
Single wake of a wind turbine over flat terrains is modeled with a finite-volume Computational Fl... more Single wake of a wind turbine over flat terrains is modeled with a finite-volume Computational Fluid Dynamics (CFD) Reynolds Averaged Navier-Stokes (RANS) solver. The RANS equations of an uncompressible flow are solved with a multigrid coupled ...
Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, host... more Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, hosted by the Poltecnico di Milano (POLIMI).
The independent comparison of three simulation codes to estimate the wind resource over complex t... more The independent comparison of three simulation codes to estimate the wind resource over complex terrains is performed in the present work. The three software are OpenFOAM, WindSim and ORFEUS: the first two are finite-volume codes solving nonlinear flow equations, while the third is a linearised spectral solver. In order to avoid possible biases, the three simulations were run by different groups with only the terrain characteristics and turbine positions available. In order to avoid errors due to the different turbine modelling approaches, no turbines were simulated, so that the focus here is on the free flow only. SCADA data were then used to validate the results and to assess the uncertainty of the simulations. The comparison is reasonably good for simple terrain configurations, while larger errors are present for terrains with severe mountainous features.
Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, host... more Presentation held at the Third Symposium on OpenFOAM® in Wind Energy, Milan 15-17 June 2015, hosted by the Poltecnico di Milano (POLIMI).
Slides from the Presentation held at The Fourth Symposium on OpenFOAM in Wind Energy (SOWE 2016).... more Slides from the Presentation held at The Fourth Symposium on OpenFOAM in Wind Energy (SOWE 2016). Delft 2-4 May 2016, hosted by TU Delft.
Internship objectives were provide to IEA Task 31-Wakebench the best result possible and highligh... more Internship objectives were provide to IEA Task 31-Wakebench the best result possible and highlight a wind and wakes simulation quality-checked procedure. The project was organized in test cases benchmark exercises. The author has been asked to design an evaluation strategy that shows that the model is formulated properly and provides an accurate representation of the real world from the point of view of the intended uses of the model. This project required the implementation of software tools that would make easier the launch and the post-processing of a large number of simulations automatically. A general description of the code is available here 1.2 TESTCASE RESULT 1.2.1 Monin-Obukhov This mandatory test case intends to demonstrate the model ability to reproduce the analytical expressions of the predicted profiles in several cases of neutral or stratified atmosphere. The analytical expressions come from the Monin-Obukhov theory. Case domain (above) and parameters (below) Two different types of calculation domain's vertical discretization were evaluated using the arithmetic and geometric progressions. A grid sensitivity study has been carried out for both the above discretization. The simulations have been built coupling the two discretization at the same horizontal resolution and number of layers. In this way it has been possible compare the two discretization results at the same calculation cost (number of total cells). The goodness of the results has been assessed using the simulated roughness