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A prediction model for wind speed ratios at pedestrian level with simplified urban canopies

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The purpose of this study is to review and improve prediction models for wind speed ratios at pedestrian level with simplified urban canopies. We adopted an extensive database of velocity fields under various conditions for arrays consisting of cubes, slender or flattened rectangles, and rectangles with varying roughness heights. Conclusions are summarized as follows: first, a new geometric parameter is introduced as a function of the plan area index and the aspect ratio so as to express the increase in virtual density that causes wind speed reduction. Second, the estimated wind speed ratios in the range 0.05 < z/h < 0.3, where h is the building height, are consistent with those derived from the database to within an error of ±25%. Lastly, the effects of the spatial distribution of the flow were investigated by classifying the regions near building models into areas in front of, to the side of, or behind the building. The correlation coefficients between the wind speeds averaged over the entire region, and the front or side region values are larger than 0.8. In contrast, in areas where the influence of roughness elements is significant, such as behind a building, the wind speeds are weakly correlated.

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A N  , B N :

Empirical constants in prediction models (subscript indicates authors)

A(z) , a(z) , b(z):

Height-dependent empirical coefficients

a M :

Attenuation coefficient in Eq. (3.4)

H :

Actual building height in simulation domain (=1L – 3L)

h :

Assumed building height (30 m for a ten-story, 15 m for a five-story, and 6 m for a two-story building)

h av :

Average building height for nonuniform array

h max :

Maximum building height for nonuniform array

L :

Standard length (=25 m)

l x :

Streamwise distance between two blocks

n :

index number of power law for wind speed

Re* :

Roughness Reynolds number (\( ={u}^{*}{z}_o/\nu \))

T :

Time scale defined by \( H/{u}^{*} \)

U :

Spatially averaged streamwise wind speed (subscript indicates defined height)

u * :

Friction velocity

u , v , w:

Wind velocity components in the x , y , z directions, respectively

V :

Magnitude of spatially averaged wind velocity vector (subscript indicates defined height)

w p :

Width of pedestrian space (=3.0 m)

X , Y:

Streamwise and spanwise block lengths, respectively

x , y , z:

Coordinates in the streamwise, transverse, and vertical directions, respectively

z o :

Roughness length

z p :

Pedestrian height (=1.5 m)

α p :

Aspect ratio (\( ={\lambda}_f/{\lambda}_p \))

α px  , α py  :

Streamwise and spanwise aspect ratios, respectively

γ N :

Prediction model of wind speed ratio (subscript indicates authors)

γ(z, ζ):

Proposed prediction model for wind speed ratio

\( {\gamma}_{h_{av}} \) :

Wind speed ratio defined by h av

\( {\gamma}_{h_{\max }} \) :

Wind speed ratio defined by h max

γfront , γ side , γ behind :

Wind speed ratio in pedestrian spaces

λ f :

Frontal area index

λ p :

Plan area index (=building coverage ratio)

ν :

Dynamic viscosity

ζ :

New geometric parameter [=\( 1-{\left(1-{\lambda}_p\right)}^{\alpha_p^{a(z)}} \)]


  • Cheng H, Castro IP (2002) Near wall flow over urban-like roughness. Bound-Layer Meteorol. 104:229–259

    Article  Google Scholar 

  • Cionco RM (1965) Mathematical model for air flow in a vegetative canopy. J Appl Meteorol 4:517–522

    Article  Google Scholar 

  • Coceal O, Thomas TG, Castro IP, Belcher SE (2006) Mean flow and turbulence statistics over groups of urban-like cubical obstacles. Bound-Layer Meteorol. 121:491–519

    Article  Google Scholar 

  • Deardorff JW (1980) Stratocumulus-capped mixed layers derived from a three-dimensional model. Bound-Layer Meteorol. 18:495–527

    Article  Google Scholar 

  • Hagishima A, Tanimoto J, Nagayama K, Meno S (2009) Aerodynamic parameters of regular arrays of rectangular blocks with various geometries. Bound-Layer Meteorol. 132:315–337

    Article  Google Scholar 

  • Hu T, Yoshie R (2013) Indices to evaluate ventilation efficiency in newly-built urban area at pedestrian level. J Wind Eng Ind Aerodyn 112:39–51

    Article  Google Scholar 

  • Ikeda Y, Hagishima A, Ikegaya N, Tanimoto J (2014) Estimation of wind speed of urban pedestrian spaces on a basis of large-eddy simulation. J. Environ. Eng. AIJ 80:709

    Google Scholar 

  • Kanda M, Inagaki A, Gryschka M, Raasch S (2013) A new aerodynamic parameterization for real urban surfaces. Bound-Layer Meteorol. 148:357–377

    Article  Google Scholar 

  • Kubota T, Miura M, Tominaga Y, Mochida A (2008) Wind tunnel tests on the relationship between building density and pedestrian-level wind velocity. Build Environ 43:1699–1708

    Article  Google Scholar 

  • Letzel MO, Krane M, Raasch S (2008) High-resolution urban large-eddy simulation studies from street canyon to neighbourhood scale. Atmos Environ 42:8770–8784

    Article  Google Scholar 

  • Macdonald RW (2000) Modelling the mean velocity profile in the urban canopy layer. Bound-Layer Meteorol. 97:25–45

    Article  Google Scholar 

  • Mohammad A.F., Zaki S.A., Hagishima A., Ali M.S.M. (2014) Determination of aerodynamic parameters of urban surfaces: methods and results revisited, J. Theor. Appl Climatol, Published online.

  • Oke TR (1988) Street design and urban canopy layer climate. Energ Build 11:103–113

    Article  Google Scholar 

  • Razak AA, Hagishima A, Ikegaya N, Tanimoto J (2013) Analysis of airflow over building arrays for assessment for urban environment. Build Environ 59:56–65

    Article  Google Scholar 

  • Snyder WH, Castro IP (2002) The critical Reynolds number for rough-wall boundary layers. Wind Eng Indust Aerodyn 90:41–54

    Article  Google Scholar 

  • Stull RB (1988) An introduction to boundary layer meteorology. Springer

  • Wang W, Yi C (2012) A new nonlinear analytical model for canopy flow over a forested hill. J Theor Appl Climatol 109:549–563

    Article  Google Scholar 

  • Yoshie R, Tanaka H, Shirasawa T, Kobayashi T (2008) Experimental study on air ventilation in a built-up area with closely-packed high-rise buildings. J Environ Eng AIJ 73:661–667[in Japanese]

    Article  Google Scholar 

  • Yuan C, Ng E (2012) Building porosity for better urban ventilation in high-density cities—a computational parametric study. Build Environ 50:176–189

    Article  Google Scholar 

  • Zaki SA, Hagishima A, Tanimoto J, Ikegaya N (2011) Aerodynamic parameters of urban building arrays with random geometries. Bound-Layer Meteorol. 138:99–120

    Article  Google Scholar 

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This work was supported by Japan Society for Promotion of Science KAKENHI Grant Numbers 25289196 and 25820282.

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Correspondence to N. Ikegaya.

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Ikegaya, N., Ikeda, Y., Hagishima, A. et al. A prediction model for wind speed ratios at pedestrian level with simplified urban canopies. Theor Appl Climatol 127, 655–665 (2017).

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