Theoretical study of the decaying convective turbulence in a shear-buoyancy PBL |
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Authors: | CJ Kipper A GoulartG Degrazia MT VilhenaPM Soares |
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Institution: | a Departamento de Engenharia Mecânica, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazilb Centro de Tecnologia de Alegrete, Universidade Federal do Pampa, 97546-550 Alegrete, RS, Brazilc Departamento de Física, Universidade Federal de Santa Maria, 97111-900 Santa Maria, RS, Brazild Instituto de Matemática, Universidade Federal do Rio Grande do Sul, 97111-900 Porto Alegre, RS, Brazile Centro de Geofísica, Universidade de Lisboa, 17049-016 Lisboa, Portugal |
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Abstract: | The derivation of a theoretical model for the decaying convective turbulence in a shear-buoyancy planetary boundary layer is considered. The model is based on the dynamical equation for the energy density spectrum in which the buoyancy, mechanical and inertial transfer terms are retained. The parameterization for the buoyancy and mechanical terms is provided by the flux Richardson number. Regarding the inertial term an approach employing Heisenberg’s spectral transfer theory is used to describe the turbulence friction, caused by small eddies, responsible for the energy dissipation of the large eddies. Therefore, a novelty in this study is to utilize the Adomian decomposition method to solve directly without linearization the energy density spectrum equation, with this the nonlinear nature of the problem is preserved. Therefore, the errors found are only due to the parameterization used. Comparison of the theoretical model is performed against large-eddy simulation data for a decaying convective turbulence in a shear-buoyancy planetary boundary layer. The results show that the existence of a mechanical turbulent driving mechanism reduces in an accentuated way the energy density spectrum and turbulent kinetic energy decay generated by the decaying convective production in a shear-buoyancy planetary boundary layer. |
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Keywords: | Energy spectrum Planetary boundary layer Heisenberg&rsquo s model Adomian method |
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