Author Contributions
Conceptualization, C.G., S.Z.I. and T.A.; methodology, C.G.; software, C.G.; validation, C.G.; formal analysis, C.G.; investigation, C.G., S.G. and S.Z.I.; resources, C.G. and S.Z.I.; data curation, C.G.; writing—original draft preparation, C.G.; writing—review and editing, C.G., S.Z.I. and N.T.; visualization, C.G.; supervision, S.Z.I.; project administration, C.G. and S.Z.I. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Single blade geometry: (a) Viewed from above; (b) Viewed from side; (c) Isometric view.
Figure 1.
Single blade geometry: (a) Viewed from above; (b) Viewed from side; (c) Isometric view.
Figure 2.
Darrieus vertical axis wind turbine (VAWT) geometry: (a) Viewed from above; (b) Viewed from side; (c) Isometric view.
Figure 2.
Darrieus vertical axis wind turbine (VAWT) geometry: (a) Viewed from above; (b) Viewed from side; (c) Isometric view.
Figure 3.
Close-up of Savonius turbine with: (a) 3 blades; (b) 4 blades; (c) 5 blades.
Figure 3.
Close-up of Savonius turbine with: (a) 3 blades; (b) 4 blades; (c) 5 blades.
Figure 4.
Cross-section of 1.4 million element mesh for Darrieus VAWT: (a) Full mesh; (b) Close-up of mesh centre; (c) Close-up of mesh around a blade.
Figure 4.
Cross-section of 1.4 million element mesh for Darrieus VAWT: (a) Full mesh; (b) Close-up of mesh centre; (c) Close-up of mesh around a blade.
Figure 5.
Three-point balance.
Figure 5.
Three-point balance.
Figure 6.
VAWT experiment setup.
Figure 6.
VAWT experiment setup.
Figure 7.
Single blade lift to drag ratio.
Figure 7.
Single blade lift to drag ratio.
Figure 8.
Power curves of unaltered Darrieus VAWT plotted against: (a) Tip-speed ratio (TSR); (b) Rotational speed.
Figure 8.
Power curves of unaltered Darrieus VAWT plotted against: (a) Tip-speed ratio (TSR); (b) Rotational speed.
Figure 9.
Isometric view of velocity contour for wind speed 14 m/s at TSR of 0.7.
Figure 9.
Isometric view of velocity contour for wind speed 14 m/s at TSR of 0.7.
Figure 10.
Contours for 14 m/s wind speed of: (a) Velocity at TSR of 0.3; (b) Pressure at TSR of 0.3; (c) Turbulent kinetic energy (TKE) at TSR of 0.3; (d) Velocity at TSR of 0.5; (e) Pressure at TSR of 0.5; (f) TKE at TSR of 0.5; (g) Velocity at TSR of 0.7; (h) Pressure at TSR of 0.7; (i) TKE at TSR of 0.7; (j) Velocity at TSR of 0.9; (k) Pressure at TSR of 0.9; (l) TKE at TSR of 0.9; (m) Velocity at TSR of 1.1; (n) Pressure at TSR of 1.1; (o) TKE at TSR of 1.1.
Figure 10.
Contours for 14 m/s wind speed of: (a) Velocity at TSR of 0.3; (b) Pressure at TSR of 0.3; (c) Turbulent kinetic energy (TKE) at TSR of 0.3; (d) Velocity at TSR of 0.5; (e) Pressure at TSR of 0.5; (f) TKE at TSR of 0.5; (g) Velocity at TSR of 0.7; (h) Pressure at TSR of 0.7; (i) TKE at TSR of 0.7; (j) Velocity at TSR of 0.9; (k) Pressure at TSR of 0.9; (l) TKE at TSR of 0.9; (m) Velocity at TSR of 1.1; (n) Pressure at TSR of 1.1; (o) TKE at TSR of 1.1.
Figure 11.
Contours for 14 m/s wind speed at different stages of rotation of: (a) Velocity at 360°; (b) Pressure at 360°; (c) TKE at 360°; (d) Velocity at 320°; (e) Pressure at 320°; (f) TKE at 320°; (g) Velocity at 280°; (h) Pressure at 280°; (i) TKE at 280°.
Figure 11.
Contours for 14 m/s wind speed at different stages of rotation of: (a) Velocity at 360°; (b) Pressure at 360°; (c) TKE at 360°; (d) Velocity at 320°; (e) Pressure at 320°; (f) TKE at 320°; (g) Velocity at 280°; (h) Pressure at 280°; (i) TKE at 280°.
Figure 12.
Power curves for variation of: (a) Diameter; (b) Blade length/height.
Figure 12.
Power curves for variation of: (a) Diameter; (b) Blade length/height.
Figure 13.
Contours at wind speed 14 m/s, rotational speed 98 rad/s for varied diameters: (a) Velocity at 0.15 m; (b) Pressure at 0.15 m; (c) TKE at 0.15 m; (d) Velocity at 0.20 m; (e) Pressure at 0.20 m; (f) TKE at 0.20 m; (g) Velocity at 0.25 m; (h) Pressure at 0.25 m; (i) TKE at 0.25 m.
Figure 13.
Contours at wind speed 14 m/s, rotational speed 98 rad/s for varied diameters: (a) Velocity at 0.15 m; (b) Pressure at 0.15 m; (c) TKE at 0.15 m; (d) Velocity at 0.20 m; (e) Pressure at 0.20 m; (f) TKE at 0.20 m; (g) Velocity at 0.25 m; (h) Pressure at 0.25 m; (i) TKE at 0.25 m.
Figure 14.
Contours at wind speed 14 m/s, rotational speed 98 rad/s for varied blade lengths/heights: (a) Velocity at 0.15 m; (b) Pressure at 0.15 m; (c) TKE at 0.15 m; (d) Velocity at 0.20 m; (e) Pressure at 0.20 m; (f) TKE at 0.20 m; (g) Velocity at 0.25 m; (h) Pressure at 0.25 m; (i) TKE at 0.25 m.
Figure 14.
Contours at wind speed 14 m/s, rotational speed 98 rad/s for varied blade lengths/heights: (a) Velocity at 0.15 m; (b) Pressure at 0.15 m; (c) TKE at 0.15 m; (d) Velocity at 0.20 m; (e) Pressure at 0.20 m; (f) TKE at 0.20 m; (g) Velocity at 0.25 m; (h) Pressure at 0.25 m; (i) TKE at 0.25 m.
Figure 15.
Darrieus and Savonius comparison.
Figure 15.
Darrieus and Savonius comparison.
Figure 16.
Contours for Savonius three-blade turbine at wind speed 6 m/s of: (a) Velocity at TSR of 0.05; (b) Pressure at TSR of 0.05; (c) TKE at TSR of 0.05; (d) Velocity at TSR of 0.10; (e) Pressure at TSR of 0.10; (f) TKE at TSR of 0.10; (g) Velocity at TSR of 0.20; (h) Pressure at TSR of 0.20; (i) TKE at TSR of 0.20.
Figure 16.
Contours for Savonius three-blade turbine at wind speed 6 m/s of: (a) Velocity at TSR of 0.05; (b) Pressure at TSR of 0.05; (c) TKE at TSR of 0.05; (d) Velocity at TSR of 0.10; (e) Pressure at TSR of 0.10; (f) TKE at TSR of 0.10; (g) Velocity at TSR of 0.20; (h) Pressure at TSR of 0.20; (i) TKE at TSR of 0.20.
Figure 17.
Savonius design comparison.
Figure 17.
Savonius design comparison.
Figure 18.
Contours at wind speed 6 m/s, TSR 0.1, for Savonius with varied number of blades: (a) Velocity with 3 blades; (b) Pressure with 3 blades; (c) TKE with 3 blades; (d) Velocity with 4 blades; (e) Pressure with 4 blades; (f) TKE with 4 blades; (g) Velocity with 5 blades; (h) Pressure with 5 blades; (i) TKE with 5 blades.
Figure 18.
Contours at wind speed 6 m/s, TSR 0.1, for Savonius with varied number of blades: (a) Velocity with 3 blades; (b) Pressure with 3 blades; (c) TKE with 3 blades; (d) Velocity with 4 blades; (e) Pressure with 4 blades; (f) TKE with 4 blades; (g) Velocity with 5 blades; (h) Pressure with 5 blades; (i) TKE with 5 blades.
Figure 19.
Single blade lift-to-drag ratios with simulation and experiment data, with ±10% error lines for experimental data, represented by dashed lines.
Figure 19.
Single blade lift-to-drag ratios with simulation and experiment data, with ±10% error lines for experimental data, represented by dashed lines.
Figure 20.
Unaltered Darrieus turbine data comparison.
Figure 20.
Unaltered Darrieus turbine data comparison.
Figure 21.
Velocity contour at 12 m/s wind speed and TSR of 0.1, with enlarged legend.
Figure 21.
Velocity contour at 12 m/s wind speed and TSR of 0.1, with enlarged legend.
Figure 22.
Smoke flow: (a) From the inlet; (b) Around the returning side.
Figure 22.
Smoke flow: (a) From the inlet; (b) Around the returning side.
Figure 23.
Velocity streamlines at wind speed 14 m/s and TSR of 0.1.
Figure 23.
Velocity streamlines at wind speed 14 m/s and TSR of 0.1.
Figure 24.
Three-blade Savonius simulation and experiment comparison.
Figure 24.
Three-blade Savonius simulation and experiment comparison.
Table 1.
Reference values for single blade simulation.
Table 1.
Reference values for single blade simulation.
Parameter | Value |
---|
Area 1 | 0.0625 m2 |
Density | 1.225 kg/m3 |
Enthalpy | 0 J/kg |
Length | 0.25 m |
Pressure | 0 Pa |
Temperature | 288.16 K |
Velocity 2 | 10 m/s |
Viscosity | 1.7894 × 10−5 kg/(m s) |
Ratio of specific heats | 1.4 |
Yplus for Heat Tran. Coef. | 300 |
Table 2.
VAWT geometry.
Parameter | Value |
---|
VAWT type | Darrieus |
No. of blades | 3 |
Chord length | 100 mm |
Blade height | 260 mm |
Rotor diameter | 200 mm |
Domain length (X) | 4 m |
Domain width (Y) | 2.2 m |
Domain height (Z) | 2.26 m |
Table 3.
VAWT solver values.
Table 3.
VAWT solver values.
Parameter | Value |
---|
Time | Transient |
Turbulence model | SST k- |
Area | 0.052 m2 |
Density | 1.225 kg/m3 |
Enthalpy | 0 J/kg |
Length | 0.1 m |
Pressure | 0 Pa |
Temperature | 288.16 K |
Velocity | 12 m/s |
Viscosity | 1.7894 × 10−5 kg/(m s) |
Ratio of specific heats | 1.4 |
Yplus for Heat Tran. Coef. | 300 |
Inlet turbulent intensity | 2% |
Inlet turbulent length scale | 0.02 m |
Outlet turbulent intensity | 2.2% |
Outlet turbulent viscosity ratio | 0.1 |
No. of timesteps | 900 |
Iterations per timestep | 20 |
Table 4.
Mesh validation.
Table 4.
Mesh validation.
Elements | Duration | Drag Coefficient | Lift Coefficient | Drag (N) | Lift (N) | Iterations |
---|
510,124 | 2 h | 0.070788 | 0.23833 | 0.27098 | 0.91236 | 500 |
1,013,542 | 1 h | 0.056044 | 0.21801 | 0.21454 | 0.83456 | 90 |
1,363,588 | 1 h | 0.055799 | 0.21802 | 0.21361 | 0.83460 | 88 |
Table 5.
Coefficient of performance calculation method comparison.
Table 5.
Coefficient of performance calculation method comparison.
Parameter | Value |
---|
WS (m/s) | 12 | 12 | 12 | 12 | 12 | 12 | 12 |
TSR | 0.1 | 0.3 | 0.5 | 0.7 | 0.9 | 1 | 1.2 |
Cp (TSR method) | 0.00837 | 0.048732 | 0.091961 | 0.121013 | 0.109003 | 0.085687 | 0.026125 |
Cp (power method) | 0.00837 | 0.048732 | 0.091961 | 0.121013 | 0.109003 | 0.085687 | 0.026125 |
% Difference | −3.6 × 10−6 | −3.6 × 10−6 | −3.6 × 10−6 | −3.6 × 10−6 | −3.6 × 10−6 | −3.6 × 10−6 | −3.6 × 10−6 |
Table 6.
Wind velocity contours from experiment at two inlet velocities.
Table 6.
Wind velocity contours from experiment at two inlet velocities.
Inlet Velocity (m/s) | Y (m) | Wind Speed (m/s) |
---|
14.12 | 0.24 | | 14 | 12 | | | | |
0 | 14.12 | Turbine | 7.9 | 6.7 | 7.2 | 7.5 | 8.4 |
−0.24 | | 14 | 12.2 | | | | |
13.86 | 0.24 | | 13 | 10.1 | | | | |
0 | 13.86 | Turbine | 9 | 8.8 | 8.5 | 8.2 | 8.8 |
−0.24 | | 15.2 | 11.9 | | | | |
| X (m) | −0.24 | 0 | 0.24 | 0.365 | 0.49 | 0.615 | 0.740 |