Spectra over complex terrain in the surface layer

Panofsky, H. A.; Dutton, John A.; Larko, D.; Lipschutz, R.; Stone, G.L.

doi:10.2172/7047080

Cited by 3 publications

(3 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At the other end of the scale, local winds within urban areas form part of local weather forecasts and are required for building design applications (e.g. Panofsky and Dutton 1984). In addition, urban air quality is becoming an issue of increasing concern (Vardoulakis et al 2003).…”

Section: Introductionmentioning

confidence: 99%

A canopy model of mean winds through urban areas

Coceal¹,

Belcher²

2004

Quart J Royal Meteoro Soc

277

248

View full text Add to dashboard Cite

SUMMARYAn urban canopy model is developed for spatially averaged mean winds within and above urban areas. The urban roughness elements are represented as a canopy-element drag carefully formulated in terms of morphological parameters of the building arrays and a mean sectional drag coefficient for a single building. Turbulent stresses are represented using a mixing-length model, with a mixing length that depends upon the density of the canopy and distance from the ground, which captures processes known to occur in canopies. The urban canopy model is sufficiently simple that it can be implemented in numerical weather-prediction models.The urban canopy model compares well with wind tunnel measurements of the mean wind profile through a homogeneous canopy of cubical roughness elements and with measurements of the effective roughness length of cubical roughness elements. These comparisons give confidence that the basic approach of a canopy model can be extended from fine-scale vegetation canopies to the canopies of large-scale roughness elements that characterize urban areas.The urban canopy model is also used to investigate the adjustment to inhomogeneous canopies. The canonical case of adjustment of a rural boundary layer to a uniform urban canopy shows that the winds within the urban canopy adjust after a distance x 0 = 3L c ln K, where L c is the canopy drag length-scale, which characterizes the canopy-element drag, and ln K depends weakly on canopy parameters and varies between about 0.5 and 2. Thus the density and shape of buildings within a radius x 0 only determine the local canopy winds. In this sense x 0 gives a dynamical definition of the size of a neighbourhood.The urban canopy model compares well with observations of the deceleration of the wind associated with adjustment of a rural boundary layer to a canopy of cubical roughness elements, but only when the sectional drag coefficient is taken to be somewhat larger than expected. We attribute this discrepancy to displacement of streamlines around the large-scale urban roughness elements, which yields a stress that decelerates the wind. A challenge for future research is to incorporate this additional 'dispersive stress' into the urban canopy model.

show abstract

Section: Introductionmentioning

confidence: 99%

A canopy model of mean winds through urban areas

Coceal¹,

Belcher²

2004

Quart J Royal Meteoro Soc

277

248

View full text Add to dashboard Cite

show abstract

“…Where C, C1, C2, k and  are the k- model constants. The standard constants have been modified to be closer to atmospheric conditions and the values proposed by (Panofsky and Dutton 1984) are used. The applied model constants are thus: C=0.033, C1 = 0.176, C2=1.92, k=1 and =1.3…”

Section: Turbulence Modelingmentioning

confidence: 99%

“…The atmospheric boundary layer settings are loaded into the CFD code as UDF. Cµ= 0.033 is the modified constant for neutral air boundary layer flows based on (Panofsky and Dutton 1984).…”

Section: The Abl Wind Profilementioning

confidence: 99%

New Actuator Disk Model for the Analysis of Wind Turbines Wake Interaction with the Ground

Adjiri

Dobrev

Benzaoui

et al. 2023

JAFM

View full text Add to dashboard Cite

Wake models based on Actuator Disk theory are usually applied to optimize the wind farm layouts and improve their overall efficiency and expected AEP. Despite the effectiveness of the existing models, most Actuator Disk approaches are based on the flow axisymmetric assumption, without considering the ground effect on the wake behavior. However, it has been shown that the mast’s height, or distance from the wind turbine to the ground, has an influence on the wake expansion on both hub’s side and at downstream of the wind turbine. Therefore, in this study, a hybrid CFD-BEM-Actuator Disk approach is developed to address the lack of the existing models. In the proposed model, the 3D wind rotor is modeled by a set of blade elements. Then, the local lift and drag forces acting on each blade element are calculated using BEM theory and incorporated into the momentum equation. This BEM-AD model is implemented in a User Defined Function (UDF) that is loaded into the CFD software. Thereby, ground effects are considered to be a wall boundary and defining a wind boundary layer profile at the inlet boundary, which describes the Atmospheric Boundary Layer (ABL). For the validation of this new Actuator Disk model, an enhanced experimental study is conducted at the Dynfluid Laboratory wind tunnel (ENSAM School Paris Tech). The Particle Image Velocimetry (PIV) measurements are used for the experimental wake explorations applied to a miniature two-bladed wind turbine. The wake developments are analyzed at two different hub heights ratio, h/D = 0.7 and 1.0 (where h is the hub height, and D is the wind rotor diameter). The analysis of the outcomes showed that the numerical simulations are in good correlation with the experimental measurements of the ENSAM wind tunnel. The numerical results show that for h/D=0.7, the upper half of the rotor operates within the boundary layer whereas the lower tip vortices are mainly developed in the horizontal direction with lower intensity compared to the upper tip vortices. This effect was not observed for the case h/D=1.0 where the rotor operates outside of the boundary layer; however, the wake centerline is upward deflected at about 0.3D. The main conclusion is that a distance above 7D must be observed between wind turbines to optimize the wind farm performance and over 1D hub height be required to limit the influence of the ground boundary layer effect.

show abstract

The use of mesoscale numerical models to assess wind distribution and boundary-layer structure in complex terrain

Pielke

1985

Boundary-Layer Meteorol

View full text Add to dashboard Cite

show abstract

Spectra over complex terrain in the surface layer

Cited by 3 publications

References 16 publications

A canopy model of mean winds through urban areas

A canopy model of mean winds through urban areas

New Actuator Disk Model for the Analysis of Wind Turbines Wake Interaction with the Ground

The use of mesoscale numerical models to assess wind distribution and boundary-layer structure in complex terrain

Contact Info

Product

Resources

About