Large-Eddy Simulation of the Convective Boundary Layer: A Comparison of Four Computer Codes

Nieuwstadt, F. T. M.; Mason, P. J.; Moeng, Chin‐Hoh; Schumann, U.

doi:10.1007/978-3-642-77674-8_24

Cited by 175 publications

(209 citation statements)

References 11 publications

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“…There, the small difference is due to the fact that the SGS contribution was not included because it was not estimated directly in this simulation. In fact, τ ww was estimated assuming the isotropy hypothesis: τ ww = (2/3) e * (Nieuwstadt et al, 1992). Despite the discrepancies in the upper half of the CBL, the results obtained here are similar to Schmidt & Schumann (1989), who found that their results fitted better to the experimental data provided by Lenschow et al (1980).…”

Section: Vertical Profile Of Variancessupporting

confidence: 84%

“…This linear profile induces a constant heating rate in the mixed layer, as expected for CBL in equilibrium. Near to the PBL top, ( w θ + ( τ θw ) reaches a minimum of −(0.11 ± 0.01)w * T * , that is smaller than the value −(0.17 ± 0.02)w * T * suggested by Schmidt & Schumann (1989), but in agreement with the value −0.11w * T * after Moeng (1984) and −0.12w * T * by Nieuwstadt et al (1992). The SGS sensible heat flux τ θw contributes significantly to the total flux near the surface, decreasing drastically to zero above the height 0.2z i .…”

Section: Turbulent and Mean Vertical Structuressupporting

confidence: 77%

“…This time period can be interpreted as the time after which the simulated CBL have reached the quasi-steady equilibrium. The overshoot is presumably caused by the initial development of large convective rolls, which turn into more random motions after the quasi-steady equilibrium (Nieuwstadt et al, 1992). It is possible to shown that the small, but visible (Fig.…”

Section: Quasi-steady Equilibriummentioning

confidence: 89%

“…The PBL is considered in equilibrium when its average TKE stops to oscillate (Nieuwstadt et al, 1992). …”

Section: Quasi-steady Equilibriummentioning

confidence: 99%

“…The θ 2 /T 2 * profile drops with the height until the middle of the CBL, where it starts to increase, reaching a secondary maximum at the entrainment layer. The SGS variance of potential temperature is estimated according to τ θθ = (0.67) −4 τ θw 2 / e * (Nieuwstadt et al, 1992).…”

Section: Vertical Profile Of Variancesmentioning

confidence: 99%

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Pollutant transport in a Convective Boundary Layer with LES

et al. 2006

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ABSTRACT. This work describes the statistical properties of a Convective Boundary Layer (CBL) and the associated turbulent transport of a passive and inert pollutant, continuously emitted in the atmosphere by an area-source on the surface. The CBL flow and properties are simulating with a Large Eddy Simulation (LES) model. To assure the development of a quasi-steady turbulent regime, both the stability parameter and the Turbulent Kinetic Energy (TKE) criteria were applied to LES with similar RESUMO. Este trabalho descreve as propriedades estatísticas de uma Camada Limite Convectiva (CLC) e o transporte turbulento de um poluente inerte e passivo, emitido continuamente por uma fonte do tipoárea localizada na superfície. As propriedades da CLC são simuladas numericamente com o modelo de simulação direta dos grandes turbilhões (LES). A determinação da condição de quase-equilíbrio realizada com base no parâmetro de estabilidade para a CLC mostrou-se equivalente ao procedimento padrão, que utiliza os valores da energia cinética turbulenta integrada na camada. A estrutura vertical da concentração do poluente, temperatura potencial, e dos respectivos fluxos turbulentos e variâncias estão de acordo com os prognósticos da teoria da similaridade para a camada de mistura. Os parâmetros de assimetria da flutuação de concentração do poluente e da velocidade vertical refletem o padrão assimétrico das estruturas na CLC e indicam a importância dos processos de entranhamento na limpeza da camada. Palavras-chave:Modelo LES, Camada Limite Convectiva, Dispersão de Poluentes, Modelagem Numérica.

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Section: Vertical Profile Of Variancessupporting

confidence: 84%

Section: Turbulent and Mean Vertical Structuressupporting

confidence: 77%

Section: Quasi-steady Equilibriummentioning

confidence: 89%

“…The PBL is considered in equilibrium when its average TKE stops to oscillate (Nieuwstadt et al, 1992). …”

Section: Quasi-steady Equilibriummentioning

confidence: 99%

Section: Vertical Profile Of Variancesmentioning

confidence: 99%

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Pollutant transport in a Convective Boundary Layer with LES

et al. 2006

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Oil plumes and dispersion in Langmuir, upper-ocean turbulence: Large-eddy simulations and K-profile parameterization

Yang

Chen

Chamecki

et al. 2015

J. Geophys. Res. Oceans

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Once oil plumes such as those originating from underwater blowouts reach the ocean mixed layer (OML), their near-surface dispersion is influenced heavily by wind and wave-generated Langmuir turbulence. In this study, the complex oil spill dispersion process is modeled using large-eddy simulation (LES). The mean plume dispersion is characterized by performing statistical analysis of the resulting fields from the LES data. Although the instantaneous oil concentration exhibits high intermittency with complex spatial patterns such as Langmuir-induced striations, it is found that the time-averaged oil distribution can still be described quite well by smooth Gaussian-type plumes. LES results show that the competition between droplet rise velocity and vertical turbulent diffusion due to Langmuir turbulence is crucial in determining both the dilution rate and overall direction of transport of oil plumes in the OML. The smoothness of the mean plume makes it feasible to aim at modeling the oil dispersion using Reynolds-averaged type formulations, such as the K-profile parameterization (KPP) with sufficient vertical resolution to capture vertical profiles in the OML. Using LES data, we evaluate the eddy viscosity and eddy diffusivity following the KPP framework. We assess the performance of previous KPP models for pure shear turbulence and Langmuir turbulence by comparing them with the LES data. Based on the assessment a modified KPP model is proposed, which shows improved overall agreement with the LES results for both the eddy viscosity and the eddy diffusivity of the oil dispersion under a variety of flow conditions and droplet sizes.

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Large Eddy Simulation of Heat Entrainment Under Arctic Sea Ice

et al. 2018

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Arctic sea ice has declined rapidly in recent decades. The faster than projected retreat suggests that free‐running large‐scale climate models may not be accurately representing some key processes. The small‐scale turbulent entrainment of heat from the mixed layer could be one such process. To better understand this mechanism, we model the Arctic Ocean's Canada Basin, which is characterized by a perennial anomalously warm Pacific Summer Water (PSW) layer residing at the base of the mixed layer and a summertime Near‐Surface Temperature Maximum (NSTM) within the mixed layer trapping heat from solar radiation. We use large eddy simulation (LES) to investigate heat entrainment for different ice‐drift velocities and different initial temperature profiles. The value of LES is that the resolved turbulent fluxes are greater than the subgrid‐scale fluxes for most of our parameter space. The results show that the presence of the NSTM enhances heat entrainment from the mixed layer. Additionally there is no PSW heat entrained under the parameter space considered. We propose a scaling law for the ocean‐to‐ice heat flux which depends on the initial temperature anomaly in the NSTM layer and the ice‐drift velocity. A case study of “The Great Arctic Cyclone of 2012” gives a turbulent heat flux from the mixed layer that is approximately 70% of the total ocean‐to‐ice heat flux estimated from the PIOMAS model often used for short‐term predictions. Present results highlight the need for large‐scale climate models to account for the NSTM layer.

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Large-Eddy Simulation of the Convective Boundary Layer: A Comparison of Four Computer Codes

Cited by 175 publications

References 11 publications

Pollutant transport in a Convective Boundary Layer with LES

Pollutant transport in a Convective Boundary Layer with LES

Oil plumes and dispersion in Langmuir, upper-ocean turbulence: Large-eddy simulations and K-profile parameterization

Large Eddy Simulation of Heat Entrainment Under Arctic Sea Ice

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