Wind Turbulence Statistics of the Atmospheric Inertial Sublayer under Near-Neutral Conditions

The inertial sublayer comprises a considerable and critical portion of the turbulent atmospheric boundary layer. The mean windward velocity profile is described comprehensively by the Monin–Obukhov similarity theory, which is equivalent to the logarithmic law of the wall in the wind tunnel boundary...

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Bibliographic Details
Main Authors: Eslam Reda Lotfy, Zambri Harun
Format: Article
Language:English
Published: MDPI AG 2020-10-01
Series:Atmosphere
Subjects:
Online Access:https://www.mdpi.com/2073-4433/11/10/1087
Description
Summary:The inertial sublayer comprises a considerable and critical portion of the turbulent atmospheric boundary layer. The mean windward velocity profile is described comprehensively by the Monin–Obukhov similarity theory, which is equivalent to the logarithmic law of the wall in the wind tunnel boundary layer. Similar logarithmic relations have been recently proposed to correlate turbulent velocity variances with height based on Townsend’s attached-eddy theory. The theory is particularly valid for high Reynolds-number flows, for example, atmospheric flow. However, the correlations have not been thoroughly examined, and a well-established model cannot be reached for all turbulent variances similar to the law of the wall of the mean-velocity. Moreover, the effect of atmospheric thermal condition on Townsend’s model has not been determined. In this research, we examined a dataset of free wind flow under a near-neutral range of atmospheric stability conditions. The results of the mean velocity reproduce the law of the wall with a slope of <inline-formula><math display="inline"><semantics><mrow><mn>2.45</mn></mrow></semantics></math></inline-formula> and intercept of <inline-formula><math display="inline"><semantics><mrow><mo>−</mo><mn>13.5</mn></mrow></semantics></math></inline-formula>. The turbulent velocity variances were fitted by logarithmic profiles consistent with those in the literature. The windward and crosswind velocity variances obtained the average slopes of <inline-formula><math display="inline"><semantics><mrow><mo>−</mo><mn>1.3</mn></mrow></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><mrow><mo>−</mo><mn>1.7</mn></mrow></semantics></math></inline-formula>, respectively. The slopes and intercepts generally increased away from the neutral state. Meanwhile, the vertical velocity and temperature variances reached the ground-level values of <inline-formula><math display="inline"><semantics><mrow><mn>1.6</mn></mrow></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><mrow><mn>7.8</mn></mrow></semantics></math></inline-formula>, respectively, under the neutral condition. The authors expect this article to be a groundwork for a general model on the vertical profiles of turbulent statistics under all atmospheric stability conditions.
ISSN:2073-4433