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Computational Fluid Dynamics Simulations of Wind Turbine Performance and Wake Characteristics.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Computational Fluid Dynamics Simulations of Wind Turbine Performance and Wake Characteristics./
Author:	Ye, Maokun.
Description:	1 online resource (153 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-05, Section: B.
Contained By:	Dissertations Abstracts International85-05B.
Subject:	Energy. -
Online resource:	click for full text (PQDT)
ISBN:	9798380828451

Computational Fluid Dynamics Simulations of Wind Turbine Performance and Wake Characteristics.
Ye, Maokun.

Computational Fluid Dynamics Simulations of Wind Turbine Performance and Wake Characteristics. - 1 online resource (153 pages)

Source: Dissertations Abstracts International, Volume: 85-05, Section: B.

Thesis (Ph.D.)--Texas A&M University, 2023.

Includes bibliographical references

In this work, Computational Fluid Dynamics (CFD) simulations are performed for three wind tunnel experiments, i.e., the NREL S826 airfoil experiment, the NTNU BT1 experiment, and the NTNU BT2 experiment by using two in-house CFD codes, ReFRESCO and FANS. In ReFRESCO simulations, the Reynolds-Averaged Navier Stokes (RANS) equations with the k − ω SST turbulence model are adopted and the Moving-Grid-Formulation (MVG) approach with a sliding interface technique is leveraged to handle the relative motion between the rotating hub and turbine blades and the stationary tower and nacelle. In FANS simulations, the RANS equations are solved with a two-layer k − ϵ turbulence closure, and the overset grid capability of the code is leveraged to deal with the relative motion between different grid blocks.As a benchmark case, CFD simulations for a wing section of the NREL S826 airfoil under the Reynolds number (Re) of 1.0 x 105 at three different Angles of Attack (AoA) are performed by the two adopted CFD codes. The CFD-predicted surface pressure distributions along the chord are compared against the experimental data directly, and good agreement between the predictions and the measurement is achieved.Then, to quantify the spatial and temporal discretization uncertainties in the simulations targeting the performance of the BT1 wind turbine, simulation matrices for ReFRESCO and FANS are respectively established by using systematically refined computational grids and different time increments. In all the computational grids, the wind turbine geometry is fully resolved, including the blades, hub, nacelle, and tower. An inlet velocity of 10 m/s and a tip speed ratio (TSR) of 6 are used for the verification study. Unsteady RANS simulations are performed. By applying a modern verification procedure to the numerical predictions, the spatial and temporal numerical uncertainties of the predicted thrust (CT ) and power (CP ) coefficients are determined. In addition, simulations are performed over a range of TSRs by the two CFD codes, and a validation study is carried out by comparing the CFD results to the experimental data.Afterward, CFD simulations targeting the wake characteristics of the NTNU BT1 wind turbine are performed by using ReFRESCO and FANS. In ReFRESCO simulations, a thorough verification and validation (V&V) study is performed first to quantify the numerical uncertainties in the CFD-predicted wake characteristics. A simulation matrix consisting of three systematically refined grids coupled with three different time increments is established. The numerical uncertainties for the predicted velocity and turbulent kinetic energy at different downstream locations are then obtained by applying a systematic verification procedure to the CFD results. Then, a validation study is carried out by comparing the CFD results against the experimental data. It is shown that the CFD predictions are in good agreement with the measurements. In FANS simulations, the results are directly compared against the measurements and other numerical results. In general, good agreement between the prediction and measurement is achieved while under-predictions in the turbulence levels are identified. In addition, the details of the wind turbine wake are visualized and discussed. It is found that the tower wake is skewed by the rotating turbine blades. As a result, the wake profiles at downstream locations are asymmetric. Further, the tower wake is carried upwards by the rotating blade wakes, and thus the location of the asymmetry peak at different downstream distances is changing. We therefore confirm that the asymmetry of the wake profile is physical and it is not a measurement error in the experiment as suspected by some researchers in previous studies.Further, CFD simulations are performed for the NTNU BT2 experiment in which two wind turbines are tandemly arrayed. In both ReFRESCO and FANS simulations, the CFD-predicted wake characteristics are compared against the experimental data and with other representative numerical results. It was found that the CFD-predicted velocity profiles behind the downstream wind turbine are in generally good agreement with the experimental data. However, challenges are also identified in the predictions of turbulent fluctuation profiles.Lastly, conclusions are drawn based on the results of the current study, and recommendations are proposed for future research.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798380828451Subjects--Topical Terms:

784773
Energy.
Subjects--Index Terms:

Wind turbineIndex Terms--Genre/Form:

554714
Electronic books.

Computational Fluid Dynamics Simulations of Wind Turbine Performance and Wake Characteristics.
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504 $a Includes bibliographical references
520 $a In this work, Computational Fluid Dynamics (CFD) simulations are performed for three wind tunnel experiments, i.e., the NREL S826 airfoil experiment, the NTNU BT1 experiment, and the NTNU BT2 experiment by using two in-house CFD codes, ReFRESCO and FANS. In ReFRESCO simulations, the Reynolds-Averaged Navier Stokes (RANS) equations with the k − ω SST turbulence model are adopted and the Moving-Grid-Formulation (MVG) approach with a sliding interface technique is leveraged to handle the relative motion between the rotating hub and turbine blades and the stationary tower and nacelle. In FANS simulations, the RANS equations are solved with a two-layer k − ϵ turbulence closure, and the overset grid capability of the code is leveraged to deal with the relative motion between different grid blocks.As a benchmark case, CFD simulations for a wing section of the NREL S826 airfoil under the Reynolds number (Re) of 1.0 x 105 at three different Angles of Attack (AoA) are performed by the two adopted CFD codes. The CFD-predicted surface pressure distributions along the chord are compared against the experimental data directly, and good agreement between the predictions and the measurement is achieved.Then, to quantify the spatial and temporal discretization uncertainties in the simulations targeting the performance of the BT1 wind turbine, simulation matrices for ReFRESCO and FANS are respectively established by using systematically refined computational grids and different time increments. In all the computational grids, the wind turbine geometry is fully resolved, including the blades, hub, nacelle, and tower. An inlet velocity of 10 m/s and a tip speed ratio (TSR) of 6 are used for the verification study. Unsteady RANS simulations are performed. By applying a modern verification procedure to the numerical predictions, the spatial and temporal numerical uncertainties of the predicted thrust (CT ) and power (CP ) coefficients are determined. In addition, simulations are performed over a range of TSRs by the two CFD codes, and a validation study is carried out by comparing the CFD results to the experimental data.Afterward, CFD simulations targeting the wake characteristics of the NTNU BT1 wind turbine are performed by using ReFRESCO and FANS. In ReFRESCO simulations, a thorough verification and validation (V&V) study is performed first to quantify the numerical uncertainties in the CFD-predicted wake characteristics. A simulation matrix consisting of three systematically refined grids coupled with three different time increments is established. The numerical uncertainties for the predicted velocity and turbulent kinetic energy at different downstream locations are then obtained by applying a systematic verification procedure to the CFD results. Then, a validation study is carried out by comparing the CFD results against the experimental data. It is shown that the CFD predictions are in good agreement with the measurements. In FANS simulations, the results are directly compared against the measurements and other numerical results. In general, good agreement between the prediction and measurement is achieved while under-predictions in the turbulence levels are identified. In addition, the details of the wind turbine wake are visualized and discussed. It is found that the tower wake is skewed by the rotating turbine blades. As a result, the wake profiles at downstream locations are asymmetric. Further, the tower wake is carried upwards by the rotating blade wakes, and thus the location of the asymmetry peak at different downstream distances is changing. We therefore confirm that the asymmetry of the wake profile is physical and it is not a measurement error in the experiment as suspected by some researchers in previous studies.Further, CFD simulations are performed for the NTNU BT2 experiment in which two wind turbines are tandemly arrayed. In both ReFRESCO and FANS simulations, the CFD-predicted wake characteristics are compared against the experimental data and with other representative numerical results. It was found that the CFD-predicted velocity profiles behind the downstream wind turbine are in generally good agreement with the experimental data. However, challenges are also identified in the predictions of turbulent fluctuation profiles.Lastly, conclusions are drawn based on the results of the current study, and recommendations are proposed for future research.
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