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Research Papers

Implementation Issues in 3D Wind Flow Predictions Over Complex Terrain

[+] Author and Article Information
John Prospathopoulos

 National Technical University of Athens, School of Mechanical Engineering, Department of Fluids, 9 Heroon Polytechniou Str., 15773 Zografou, Athens, Greecejprosp@fluid.mech.ntua.gr

Spyros G. Voutsinas1

 National Technical University of Athens, School of Mechanical Engineering, Department of Fluids, 9 Heroon Polytechniou Str., 15773 Zografou, Athens, Greecespyros@fluid.mech.ntua.gr

1

Address for correspondence: NTUA, Department of Fluids, 9 Heroon Polytechniou Str., 15773 Zografou, Athens, Greece

J. Sol. Energy Eng 128(4), 539-553 (Jul 23, 2006) (15 pages) doi:10.1115/1.2346702 History: Received September 22, 2005; Revised July 23, 2006

Practical aspects concerning the use of 3D Navier-Stokes solvers as prediction tools for micro-siting of wind energy installations are considered. Micro-siting is an important issue for a successful application of wind energy in sites of complex terrain. There is a constantly increasing interest in using mean wind flow predictions based on Reynolds averaged Navier-Stokes (RANS) solvers in order to minimize the number of required field measurements. In this connection, certain numerical aspects, such as the extent of the numerical flow domain, the choice of the appropriate inflow boundary conditions, and the grid resolution, can decisively affect the quality of the predictions. In the present paper, these aspects are analyzed with reference to the Askervein hill data base of full scale measurements. The objective of the work is to provide guidelines with respect to the definition of appropriate boundary conditions and the construction of an adequate and effective computational grid when a RANS solver is implemented. In particular, it is concluded that (a) the ground roughness affects the predictions significantly, (b) the computational domain should have an extent permitting the full development of the flow before entering the region of interest, and (c) the quality of the predictions at the local altitude maxima depends on the grid density in the main flow direction.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The variation of B coefficient with the surface value of the dimensionless rate of dissipation per unit of turbulent kinetic energy SR

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Figure 2

The computation domain

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Figure 3

Terrain of the Askervein hill after the smoothing of the irregularities and the alignment with the main direction of the flow

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Figure 4

Fitting of the logarithmic distribution of the velocity to the experimental data

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Figure 5

Altitude contours of the Askervein hill

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Figure 6

The effect of the crosswind extension of the terrain on the dimensionless velocity contours (U∕Uin) at 10m A.G.L. (a) 2400×2400m2 and (b) 2400×3600m2.

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Figure 7

Effect of the downwind extension of the terrain on the dimensionless velocity along the line A-A at 10m A.G.L.

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Figure 8

Effect of the downwind extension of the terrain on the dimensionless velocity along the line AA-AA at 10m A.G.L.

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Figure 9

Effect of the upwind extension of the terrain on the dimensionless velocity along the line A-A at 10m A.G.L.

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Figure 10

Effect of the upwind extension of the terrain on the dimensionless velocity along the line AA-AA at 10m A.G.L.

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Figure 11

Effect of the upwind extension of the terrain on the longitudinal velocity profile in front of the hill—line A-A, P1 position in Fig. 9

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Figure 12

Effect of the upwind extension of the terrain on the longitudinal velocity profile in front of the hill—line AA-AA, P2 position in Fig. 1

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Figure 13

Effect of the upwind extension of the terrain on the vertical velocity profile in front of the hill—line A-A, P1 position in Fig. 9

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Figure 14

Effect of the upwind extension of the terrain on the vertical velocity profile in front of the hill—line AA-AA, P2 position in Fig. 1

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Figure 15

Altitude contours of the Askervein hill for the extended terrain 3600×3600m

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Figure 16

The effect of the ground roughness on the dimensionless velocity along the line A-A at 10m A.G.L.

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Figure 17

The effect of the ground roughness on the dimensionless velocity along the line AA-AA at 10m A.G.L.

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Figure 18

Effect of the vertical grid refinement on the measure of the velocity along the line A-A at 10m A.G.L.

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Figure 19

Effect of the vertical grid refinement on the measure of the velocity along the line AA-AA at 10m A.G.L.

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Figure 20

Effect of the vertical grid refinement on the longitudinal velocity profile in the lee side of the hill—line A-A, P3 position in Fig. 1

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Figure 21

Effect of the vertical grid refinement on the longitudinal velocity profile in the lee side of the hill—line AA-AA, P4 position in Fig. 1

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Figure 22

Effect of the vertical grid refinement on the lateral component of the velocity in the lee side of the hill—line A-A, P3 position in Fig. 1

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Figure 23

Effect of the vertical grid refinement on the lateral component of the velocity in the lee side of the hill—line AA-AA, P4 position in Fig. 1

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Figure 24

Effect of the vertical grid refinement on the vertical component of the velocity in the lee side of the hill—line A-A, P3 position in Fig. 1

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Figure 25

Effect of the vertical grid refinement on the vertical component of the velocity in the lee side of the hill—line AA-AA, P4 position in Fig. 1

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Figure 26

Effect of the longitudinal grid refinement on the measure of the velocity along the line A-A at 10m A.G.L.

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Figure 27

Effect of the longitudinal grid refinement on the measure of the velocity along the line AA-AA at 10m A.G.L.

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