p m C R C V 7 11 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 31

P m c r c v 7 11 190 191 192 193 194 195 196 197 198

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p m C R C V (7) 11 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204
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3.1. Validation of the present results Averaged moment coefficient ( C m ) for complete two revolutions of the rotor has been obtained from the present computations, and the corresponding power coefficient ( C p ) has been calculated using Eqn.7. This present C p values are validated with experimental and numerical results of Bai et al. (2019), as shown in Fig. 5. the results are closely matching with the experimental results of Bai et al. (2019) within the TSR range of 0.2-0.8. However, in the present simulations, the maximum C p occurs at the TSR of 0.8. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 Bai et el. (2019) Experiment Bai et al. (2019) Numerical Present results Fig. 5: Effect of TSR on C m for rotor placed in an unconfined domain ( CW =12 D ) Computations are carried out with a rotor placed in a confined channel with wind velocity, u = 3.9479 m/s (Re=1x10 5 ) at the inlet, and λ = 0.8. The computational domain and boundary conditions used in the present study are the same as that of Bai et al. (2019). The effect of channel width has been studied, and their results are used for validating present computations. The comparison is presented in Table-3. When compared to Bai et al. (2019), the present computations underestimate the value of C p , and deviation is increasing with CW . 12 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219
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This deviation is due to the time averaged values. Table-3: Validation of present results Channel width C p reported by Bai et al. (2019) C p calculated from present computations. Deviation (%) 4 D 0.34 0.31 8.8 3 D 0.39 0.37 2.0 2 D 0.57 0.56 1.7 3.2. Effect of Channel Width ( CW ) on rotor performance In the present study, the rotor without confinement ( CW = 12 D ) is considered as the base case. The variation of moment coefficient C m with respect to the angular position of the rotor is shown in Fig. 6. Compared to the unconfined rotor, 154.54 % increase in average C m is observed for rotor with confinement ( CW = 2 D ).The effect of channel confinement on the performance coefficients C p and C m is shown in Fig. 7. The C p and C m are directly proportional, and its value increases with decreasing CW .The increase in average C m and C p with decreasing CW is due to confined walls, which focuses and increases the amount of energy that strikes the rotor. The variation in pressure inside the confined channel varies much with respect to the angular position of the rotor as well for different CW. The variation in pressure drop across the channel due to the presence of the rotor has been shown in Fig.12. As the rotor position ( o ) increases from 0˚ the pressure drop slowly increases because of the resisting area increases and reaches the maximum at an angular position of 90˚ later it reduces to initial value as the position of the rotor reaches 180˚ till this the blade experienced advancing action, after this the blade will be in returning action. This action repeats as the other blade now will act as an advancing blade. Pressure contour of CW =2 D, 3 D and4 D for four different angular positions (0˚, 45˚, 90˚, 135˚) has been shown in Fig 8-10 respectively. For each CW the 13 220 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236
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