Blade‐resolved simulations of a model wind turbine: effect of temporal convergence

Mittal, Anshul; Sreenivas, Kidambi; Taylor, Lafayette K.; Hereth, Levi; Hilbert, Christopher B.

doi:10.1002/we.1949

Cited by 28 publications

(22 citation statements)

References 24 publications

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“…The method yields a divergence-free velocity field as the residual is reduced and the solution converges. For further details, please refer to Mittal et al [5]…”

Section: A Flow Regimesmentioning

confidence: 99%

“…Newton's method is used to drive the unsteady residual to zero, thereby ensuring time accuracy. For further details of the time advancement algorithm, the reader is referred to the study by Mittal et al [5] The flux Jacobians arising from this linearization can be evaluated using numerical derivatives or the complex Taylor series method. They can also be replaced by approximations which result in substantial savings in computational time.…”

Section: Time Evolutionmentioning

confidence: 99%

“…However, this has not been observed in practice and points that are very close to each other have approximately the same solution values. Further details on the parallel implementation of the sliding interface algorithm are available in Hyams et al [5,15,16]…”

Section: F Relative Motionmentioning

confidence: 99%

“…The BT1 rotor, on the other hand, was designed from the beginning to be part of a two rotor setup with one rotor operating in the wake of the other. BT1 results computed using Tenasi were presented in Sreenivas et al [4] and Mittal et al [5] with three different turbulence models and the effect of temporal convergence were investigated. Good agreement was obtained between predicted power and thrust coefficients and experimental data for all the turbulence models.…”

Section: Introductionmentioning

confidence: 99%

“…It is known that fully-resolved rotor CFD simulations perform better over a wider operating range than BEM based simulations due to the capability of the method to capture the flow separation over the blade at the off-design conditions. [8] The BT1 [4,5] study showed that out of the three turbulence models tested (Spalart-Allmaras, Menter's SST, and a DES version of the Menter's SST), the DES version of the Menter's SST model performed better than the other two.…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of the interaction between tandem wind turbines

Sreenivas

Mittal

Hereth

et al. 2016

Journal of Wind Engineering and Industrial Aerodynamics

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Two model wind turbines operating in tandem are simulated using Tenasi, a nodecentered, finite volume unstructured flow solver. The turbine blades are designed using the NREL S826 airfoils. The entire test section of the wind tunnel is simulated since the blockage (based on swept area of the rotor and tower area) was 12%. The simulations included the tunnel walls, wind turbine blades, hubs, nacelles and towers. Detailed experimental data is available for a variety of flow conditions (varying tip-speed-ratios). The results presented here are for tip-speed-ratios of 2.5, 4, and 7 for the rear turbine while the front turbine was always operated at the design tip speed ratio of 6. The tunnel wind speed was 10 m/s and the wind turbine RPM was varied to achieve the desired tip-speed-ratios. A DES version of the Menter's SST turbulence model is utilized for the turbulence closure. Turbine performance as well as wake data at various locations is compared to experiment (Blind Test 2 study carried out at NTNU, Norway). Very good agreement is observed for the turbine performance. Good agreement was obtained for velocity fluctuations in the wake region with trends captured very well. Mean velocity predictions agree reasonably well.

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“…The method yields a divergence-free velocity field as the residual is reduced and the solution converges. For further details, please refer to Mittal et al [5]…”

Section: A Flow Regimesmentioning

confidence: 99%

Section: Time Evolutionmentioning

confidence: 99%

Section: F Relative Motionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical simulation of the interaction between tandem wind turbines

Sreenivas

Mittal

Hereth

et al. 2016

Journal of Wind Engineering and Industrial Aerodynamics

Self Cite

View full text Add to dashboard Cite

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Effect of tower and nacelle on the flow past a wind turbine

et al. 2017

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Large eddy simulations (LES) of the flow past a wind turbine with and without tower and nacelle have been performed at 2 tip speed ratios (TSR, ), λ=3 and 6, where the latter corresponds to design conditions. The turbine model is placed in a virtual wind tunnel to reproduce the “Blind test 1” experiment performed at the Norwegian University of Science and Technology (NTNU) closed‐loop wind tunnel. The wind turbine was modeled using the actuator line model for the rotor blades and the immersed boundary method for the tower and nacelle. The aim of the paper is to highlight the impact of tower and nacelle on the turbine wake. Therefore, a second set of simulations with the rotating blades only (neglecting the tower and nacelle) has been performed as reference. Present results are compared with the experimental measurements made at NTNU and numerical simulations available in the literature. The tower and nacelle not only produce a velocity deficit in the wake but they also affect the turbulent kinetic energy and the fluxes. The wake of the tower interacts with that generated by the turbine blades promoting the breakdown of the tip vortex and increasing the mean kinetic energy flux into the wake. When tower and nacelle are modeled in the numerical simulations, results improve significantly both in the near wake and in the far wake.

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Evaluating the accuracy of the actuator line model against blade element momentum theory in uniform inflow

et al. 2022

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We evaluate the accuracy of the actuator line model (ALM) approach by performing simulations for the NREL 5‐MW wind turbine in uniform inflow using three large eddy simulation codes. The power and thrust coefficients obtained using the three codes agree within 1% when the grid spacing normalΔgrid≤5.25 m and are cross‐validated against blade element momentum (BEM) theory. We find that the results of ALM converge towards BEM theory without the need for tip correction when the numerical resolution is increased. For normalΔgrid=0.98 m, the difference between the power and thrust coefficient obtained using ALM and BEM is 4.5% and 2.1%, respectively, although we note that no absolute convergence between ALM and BEM can be obtained as both models use different assumptions, such as the use of a force projection method in the ALM. The difference in the local axial and tangential forces along the blades obtained from ALM simulations using normalΔgrid=1.97 m and normalΔgrid=0.98 m can be as large as 10%. The effect of the number of actuator points on the obtained turbine power and thrust coefficients is limited as the results converge when the spacing between the actuator points is about three times the grid spacing. This insight on the required number of blade points can be used to improve the efficiency of actuator line simulations.

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Blade‐resolved simulations of a model wind turbine: effect of temporal convergence

Cited by 28 publications

References 24 publications

Numerical simulation of the interaction between tandem wind turbines

Numerical simulation of the interaction between tandem wind turbines

Effect of tower and nacelle on the flow past a wind turbine

Evaluating the accuracy of the actuator line model against blade element momentum theory in uniform inflow

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