A consistent steady state CFD simulation method for stratified atmospheric boundary layer flows

Chang, Chi-Yao; Schmidt, Jonas; Dörenkämper, Martin; Stoevesandt, Bernhard

doi:10.1016/j.jweia.2017.10.003

Cited by 30 publications

(26 citation statements)

References 22 publications

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“…al 1996. Moreover, an ABL wall function is used to apply the roughness-related logarithmic law near to the ground, which is consistent with Monin-Obukhov similarity theory (Chang et al, 2018). For the primal CFD simulation of a circular domain the standard "inletOutlet" BC is used which checks if the flow is flowing into domain or out of it and switches between fixed value and zero gradient respectively.…”

Section: Numerical Resultsmentioning

confidence: 99%

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Adjoint-based Calibration of Inlet Boundary Condition for Atmospheric CFD Solvers

Akbarzadeh

Kassem

Buhr

et al. 2019

Preprint

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Abstract. A continuous adjoint solver is developed for optimization of the inlet velocity profile boundary condition for CFD simulations of the neutral atmospheric boundary layer (ABL). The adjoint solver uses interior domain wind speed observations to compute the gradient of a calibration function with respect to inlet velocity components and wind direction. The solver has been implemented in the open source CFD package OpenFOAM. The sensitivities computed by the newly developed adjoint solver are validated against the second order finite-difference method. Furthermore, the DAKOTA optimization package is coupled with OpenFOAM, and a number of numerical studies are carried out including the calibration of the inlet velocity profile of a 3-D complex domain.

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Section: Numerical Resultsmentioning

confidence: 99%

“…The second method which is common in CFD RANS simulations is to solve a zero-pressure gradient equation for a onedimensional (1D) domain with periodic boundary conditions in stream-and span-wise directions (Chang et al, 2018):…”

Section: Inflow Boundarymentioning

confidence: 99%

Adjoint-based Calibration of Inlet Boundary Condition for Atmospheric CFD Solvers

Akbarzadeh

Kassem

Buhr

et al. 2019

Preprint

Self Cite

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“…where the subscript p denotes the first cell center above the ground, the equivalent friction wind speed is u * k = C 0.25 µ φ −0.5 k,p k 0.5 p , and the wall shear stress is τ w = µ t,p (dU/dz). The eddy viscosity µ t,p and the turbulent heat conductivity are imposed at the first cell center above the ground as [54]…”

Section: Boundary Conditionsmentioning

confidence: 99%

Monin–Obukhov Similarity Theory for Modeling of Wind Turbine Wakes under Atmospheric Stable Conditions: Breakdown and Modifications

Han

Liu

et al. 2019

Applied Sciences

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Monin–Obukhov similarity theory (MOST) overestimates the mean vertical velocity gradient in some atmospheric stable conditions, i.e., Richardson number R f < 0 . 25 . To obtain a given hub-height inflow velocity for a certain roughness length, this overestimated velocity gradient underpredicts the friction wind speed and the turbulence intensity, potentially influencing wake modeling of a wind turbine. This work investigates the side effects of the breakdown of MOST on wake modeling under stable conditions and makes some modifications to the flow similarity functions to eliminate these side effects. Based on a field measurement in a wind farm, we first show that MOST predicts a larger velocity gradient for the atmospheric stability parameter ζ > 0 . 1 and proposes new flow similarity functions without constraining R f to limit the overestimated velocity gradient. Next, different turbulence models based on MOST and a modified one based on the new similarity functions are investigated through numerical simulations. These turbulence models are combined with the actuator disk model (AD) and Reynolds-averaged Navier–Stokes equations (RANS) to model wind turbine wakes under stable conditions. As compared to measurements, numerical results show that turbulence models based on MOST result in a larger wake deficit and a slower wake recovery rate with a root-mean-squared error (RSME) of wake deficit in the range of 0.07 to 0.20. This overestimated wake effect is improved by applying the new similarity functions, and the RSME of wake deficit is reduced by 0.05 on average.

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“…Furthermore, the present model does not rely on MOST functions for calculating u * and θ * , meaning that MOST is not predefined in the EARS model. This is not so in Chang et al (2018), where MOST was used as a wall function for estimating u * and θ * and then for comparing the profiles of V(z) and Θ(z) predicted by MOST to the model result. Hence, their model results cannot be considered to be independent of the imposed MOST functions.…”

Section: Monin-obukhov Similarity Theorymentioning

confidence: 99%

Consistent Boundary-Condition Treatment for Computation of the Atmospheric Boundary Layer Using the Explicit Algebraic Reynolds-Stress Model

Želi

Brethouwer

Wallin

et al. 2018

Boundary-Layer Meteorol

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Standard turbulence models for the atmospheric boundary layer (ABL) typically use boundary conditions based on the Monin-Obukhov similarity theory (MOST). This can lead to inconsistency between the boundary condition and the closure model. Here, we propose a new boundary-condition treatment of the stratified ABL, derived for the so-called explicit algebraic Reynolds-stress model. The boundary conditions correspond to the relations for vanishing buoyancy effects that are valid close to the ground. The solution for the stratified surface layer is in agreement with the surface scaling physics and MOST functions. This was validated in a simulation of an idealized diurnal cycle of the ABL based on the second Global Energy and Water cycle Experiment (GEWEX) Atmospheric Boundary Layer Study (GABLS2) case.

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A consistent steady state CFD simulation method for stratified atmospheric boundary layer flows

Cited by 30 publications

References 22 publications

Adjoint-based Calibration of Inlet Boundary Condition for Atmospheric CFD Solvers

Adjoint-based Calibration of Inlet Boundary Condition for Atmospheric CFD Solvers

Monin–Obukhov Similarity Theory for Modeling of Wind Turbine Wakes under Atmospheric Stable Conditions: Breakdown and Modifications

Consistent Boundary-Condition Treatment for Computation of the Atmospheric Boundary Layer Using the Explicit Algebraic Reynolds-Stress Model

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