Aerodynamic roughness length: Correlation with roughness elements

Fang, Chou; Sill, Ben L.

doi:10.1016/0167-6105(92)90444-f

Cited by 28 publications

(12 citation statements)

References 9 publications

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“…5) are generally low for z d but are among the best for z 0 . The input requirements are reasonably simple (com- Raupach et al (1980) Schlichting (1937) Styles (1997) Theurer (1993) Tieleman et al (1978) Visser (1987) Bottema (1995b) Bottema (1995b) Bottema (1995b) Bottema (1995b, Hussain andLee (1980) Fang andSill (1992), Kutzbach (1961) Bottema (1995b) Bottema (1995b) Bottema (1995b, Fang and Sill (1992) Bottema (1995b, Fang and Sill (1992) Bottema (1995b, Fang and Sill (1992) Styles (1997) Theurer (1993) Bottema (1995b, Fang and Sill (1992) Bottema (1995b FIG. 6.…”

Section: Comparison Of Measured and Predicted Valuesmentioning

confidence: 99%

Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form

Grimmond¹,

Oke²

1999

J. Appl. Meteor.

999

702

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Several methods to determine the aerodynamic characteristics of a site through analysis of its surface form (morphometry) are considered in relation to cities. The measures discussed include zero-plane displacement length (z d), roughness length (z 0), depth of the roughness sublayer, and aerodynamic conductance. A sensitivity analysis is conducted on seven formulas to estimate z d and nine to estimate z 0 , covering a wide range of probable urban roughness densities. Geographic information systems developed for 11 sites in 7 North American cities are used to characterize their morphometry-the height, shape, three-dimensional area, and spatial distribution of their roughness elements (buildings and trees). Most of the sites are in residential suburbs, but one is industrial and two are near city centers. This descriptive survey of urban geometric form is used, together with the morphometric formulas, to derive the apparent aerodynamic characteristics of the sites. The resulting estimates of z d and z 0 are compared with values obtained from analysis of wind and turbulence observations. The latter are obtained from a survey of approximately 60 field studies and 14 laboratory studies of real and scale model cities. Despite the comprehensive nature of the survey, very few studies are found to be acceptable and their scatter is large, hence they do not provide a standard against which to test the morphometric algorithms. Further, the data show only weak relations between measured z d and z 0 and roughness density. The relative merits of morphometric and wind-based estimates of aerodynamic parameters are discussed. Recommendations are made concerning the choice of method to estimate z d and z 0 in urban areas and their most likely magnitude.

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Section: Comparison Of Measured and Predicted Valuesmentioning

confidence: 99%

Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form

Grimmond¹,

Oke²

1999

J. Appl. Meteor.

999

702

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“…LEGO cubes in a symmetrical, staggered pattern were used to simulate buildings and other obstructions in a suburban environment. The spacing and height of surface roughness elements in each configuration was preliminarily determined as indicated in Counihan (1971), Gartshore and De Croos (1977), and Fang and Sill (1992), and final arrangements were made by making continuous adjustments. Details of surface roughness and barriers' design in the 1:400, 1:250 and 1:220 suburban ABL wind-tunnel simulations are given in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Wind-tunnel simulations of the suburban ABL and comparison with international standards

Kozmar¹

2011

Wind and Structures An International Journal

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Abstract. Three wind-tunnel simulations of the atmospheric boundary layer (ABL) flow in suburban country exposure were generated for length scale factors 1:400, 1:250 and 1:220 to investigate scale effects in wind-tunnel simulations of the suburban ABL, to address recommended wind characteristics for suburban exposures reported in international standards, and to test redesigned experimental hardware. Investigated parameters are mean velocity, turbulence intensity, turbulent Reynolds shear stress, integral length scale of turbulence and power spectral density of velocity fluctuations. Experimental results indicate it is possible to reproduce suburban natural winds in the wind tunnel at different length scales without significant influence of the simulation length scale on airflow characteristics. However, in the wind tunnel it was not possible to reproduce two characteristic phenomena observed in full-scale: dependence of integral length scales on reference wind velocity and a linear increase in integral length scales with height. Furthermore, in international standards there is a considerable scatter of recommended values for suburban wind characteristics. In particular, recommended integral length scales in ESDU 85020 (1985) are significantly larger than in other international standards. Truncated vortex generators applied in this study proved to be successful in part-depth suburban ABL wind-tunnel simulation that yield a novel methodology in studies on wind effects on structures and air pollution dispersion.

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“…Ward-Smith (1980) gives typical ranges of the surface roughness for a variety of materials. The surface roughness of a snow saltation layer was estimated based on Clifton and others (2006), Fang and Sill (1992) and Tabler (1980).…”

Section: Appendix: Design and Characterization Of The Wind Tunnel A1mentioning

confidence: 99%

Wind tunnel experiments: saltation is necessary for wind-packing

Sommer

Lehning

Fierz³

2017

J. Glaciol.

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ABSTRACT. Wind-packed snow in the form of slabs or crusts is an important part of alpine and polar snow covers. Yet, the formation process of such layers is poorly understood. For example, it remains unclear whether drifting snow is necessary for wind-packing or not. A better understanding of wind-packing could improve snow-cover models and avalanche danger forecasts and contribute to the assessment of mass balances in polar regions. We designed a closed-circuit, obround wind tunnel to study the process of wind crust formation. A SnowMicroPen was used to measure how the hardness of the snow evolved. The results show that no crust forms without saltation. Drifting snow is a necessary but not sufficient condition for wind-packing. The dynamics of erosion and deposition appear to be equally important.

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Aerodynamic roughness length: Correlation with roughness elements

Cited by 28 publications

References 9 publications

Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form

Aerodynamic Properties of Urban Areas Derived from Analysis of Surface Form

Wind-tunnel simulations of the suburban ABL and comparison with international standards

Wind tunnel experiments: saltation is necessary for wind-packing

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