wind energy resource evaluation in a site of central italy ... - WindSim

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1.3 Mathematical formulation of the ABLThe Atmospheric Boundary Layer can be described through very simplemathematical equations using the so called surface-layer similarity, also known asMonin-Obukhov similarity.According to this, the speed vertical profile of the wind can be described as afunction of the height by the logarithmic profile,1.1) ( ) = ∙where,is the friction velocity[m/s]is the Von Karman constant [ ]is the roughness height[m]The friction velocity is calculated by the equation1.2) =where,τ is the shear stress at the wall boundary [N/m 2 ]is the air density [kg/m 3 ]An example of a velocity vertical profile, is shown in figure 1.15
Figure 1.1: Example of an atmospheric speed vertical profile – U=10 m/s – d=500 m.1.4 Navier-Stokes and RANS EquationsThe most general equations that govern the fluid flow in the ABL are theNavier.Stokes equations [10]. These equations express the physical principles ofconservation of mass, momentum and energy. Since a neutral boundary layer is tobe analysed, no thermal effect is taken into account and the energy equation willnot be solvedConservation of mass (“continuity equation”)1.3)( )=0Conservation of momentum (“momentum equation”)1.4)( )+u( )=− +ρf + μ ( )The numerical solution of the Navier-Stokes equation is possible only if a DirectNumerical Simulation is seeked. Nowadays this kind of CFD technique is applied tosimple geometries and very low Reynolds numbers. Even with the today’s computerpower, It is only used for academic research.6
Page 1 and 2: UNIVERSITÀ DEGLI STUDI DI CAGLIARI
Page 3 and 4: IndexIndex page IAcknowledgmentsVII
Page 5 and 6: CHAPTER 4: Characteristics of the s
Page 7 and 8: 6.7.1 Mean wind velocity page 1096.
Page 9 and 10: This thesis is the result of a prac
Page 11 and 12: WindSim is a software developed by
Page 13: CHAPTER 1. Atmospheric Boundary Lay
Page 17 and 18: 1.5 The WindSim numerical codeWindS
Page 19 and 20: (κ−ε RNG or the Low Reynolds),
Page 21 and 22: 1.5.4 RESULTSThe Results module all
Page 23 and 24: Figure 1.2: Example of TKE vertical
Page 25 and 26: CHAPTER 2. Simulations over flat te
Page 27 and 28: inlet position (0 meters), station
Page 29 and 30: 2.4 Height distribution factor sens
Page 31 and 32: e decreased, to avoid to build thin
Page 33 and 34: Figure 2.10: Vertical profiles for
Page 35 and 36: CHAPTER 3. Simulations over 2D hill
Page 37 and 38: Table 3.1: Measurement coordinatesS
Page 39 and 40: The results shown above demonstrate
Page 41 and 42: Figure 3.6: Sketch of the 15 km lon
Page 43 and 44: Figure 3.9: Influence of the height
Page 45 and 46: Figure 3.13: Zoom of the hill top r
Page 47 and 48: 3.5.2) = ∙.The two models for att
Page 49 and 50: H [m] hill heightν[m 2 /s] air cin
Page 51 and 52: Figure 3.18: Particular of the nume
Page 53 and 54: Finally, the horizontal x velocity
Page 55 and 56: Figure 3.25: Z velocity componentFi
Page 57 and 58: 3.6 RemarksA CFD study of a boundar
Page 59 and 60: Some experimental wind data of this
Page 61 and 62: Both the pictures 4.3 and 4.4 have
Page 63 and 64: Table 4.2: Description of the color
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In this periods, data are recorded
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In the following pages, a short des
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4.3.2 Mast 5424-15 m Period April-M
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4.3.4 Mast 5424-15 m Period Novembe
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4.3.6 Mast 5428-40 m Period April-M
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4.3.8 Mast 5428-50 m Period Novembe
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4.3.10 Mast 5428-30 m Period Novemb
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4.4.2 Mast 542870
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4.5.2 Mast 542872
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CHAPTER 5. Test of the Free Stream
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case the wind is blowing from the e
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Geometrical modelTable 5.3: Input p
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Figure 5.6: Vertical profiles in po
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The orthogonalization of the grid h
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Figure 5.9: Map of speed-ups for di
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Figure 5.30: Speed-2D at 30 m heigh
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Figure 5.12: Speed-2D at 30 m heigh
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CHAPTER 6. Analysis of the wind fie
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Table 6.2: Boundary conditions and
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6.5 Vertical profiles of VelocityTo
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characterized by high wind speed (5
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From the error analysis, it is foun
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Anyhow, the trend of the linear int
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Concerning the CFD simulations, val
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Analyzing RMS error table for tower
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A general overview of the figure 6.
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6.7 Cross Checking of wind dataIn t
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Figure 6.8 a/bFigure 6.8 c/dFigure
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Table 6.11: RMS error for cross che
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Figure 6.9 e/fFigure 6.9 g/hFigure
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Figure 6.10 g/hFigure 6.10 i/lFigur
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to have a better agreement during t
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Figure 7.2: Weibull fitting of the
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Figure 7.5: Perspective view of the
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The calculated AEP has been reporte
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ConclusionsIn this thesis the evalu
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Bibliography[1] CRASTO G. - Numeric
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