Effect of atmospheric boundary layer top and capping inversion properties on mean wind profiles

Kelly, M. C. (Main supervisor), Jørgen Højstrup (External examiner), Jacob Berg (Supervisor)

Activity: Examinations and supervisionSupervisor activities

Description

The thesis studies the inversion capped neutral (conditionally neutral) atmospheric boundary layer. The effect of the potential temperature inversion on the mean wind speed profile is analyzed using the data from seventeen LES simulations. The averaged turbulent quantities profiles are presented, explained and the relevant dimensional groupings to obtain dimensionless functions are investigated. Based on this observations three solutions for the mean speed profile have been obtained: analytic, semi-empirical and from similarity theory. The last is the most reliable and is obtained using Buckingham Pi theorem twice. First, to obtain an expression for the entrainment heat flux based on surface and ABL-top parameters. Then this expression is used in a second similarity theory where the choice of the groupings is analogous to Monin-Obukhov’s with the difference that the heat flux profile is used rather than the surface heat flux. This allows to identify two dimensionless groups. These two groups are related by very similar functions and the existence of a universal function that relates the two groups has been assumed and found. This allows to express the mean wind speed profile as S(z) = (u*/) ln(z/z0)+c(z/B)2. This formulation ensures maximum errors within 5% percent, up to 80% of the boundary layer height when compared to LES results.
Period30 Jan 201730 Jun 2017
ExamineeRoberto Cersosimo
Examination held atDepartment of Wind Energy
Degree of RecognitionNational