scholarly journals The spatial variability and structure of turbulent kinetic energy in the convective boundary layer over an isolated mountain

2016 ◽  
Author(s):  
Mark Sghiatti
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Spatial Variability ◽  
Turbulent Kinetic Energy ◽  
Convective Boundary Layer ◽  
Convective Boundary

scholarly journals A Scale-Adaptive Turbulent Kinetic Energy Closure for the Dry Convective Boundary Layer

2018 ◽  
Vol 75 (2) ◽  
pp. 675-690 ◽  
Author(s):  
Marcin J. Kurowski ◽  
João Teixeira
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Convective Boundary Layer ◽  
Mixing Length ◽  
Subgrid Scale ◽  
Convective Boundary ◽  
Continuous Transition ◽  
Simple Method ◽  
Grid Length

Abstract A pragmatic scale-adaptive turbulent kinetic energy (TKE) closure is proposed to simulate the dry convective boundary layer for a variety of horizontal grid resolutions: from 50 m, typical of large-eddy simulation models that use three-dimensional turbulence parameterizations/closures, up to 100 km, typical of climate models that use one-dimensional turbulence and convection parameterizations/closures. Since parameterizations/closures using the TKE approach have been frequently used in these two asymptotic limits, a simple method is proposed to merge them with a mixing-length-scale formulation for intermediate resolutions. This new scale-adaptive mixing length naturally increases with increasing grid length until it saturates as the grid length reaches mesoscale-model resolution. The results obtained using this new approach for dry convective boundary layers are promising. The mean vertical profiles of potential temperature and heat flux remain in good agreement for different resolutions. A continuous transition (in terms of resolution) across the gray zone is illustrated through the partitioning between the model-resolved and the subgrid-scale transports as well as by documenting the transition of the subgrid-scale TKE source/sink terms. In summary, a natural and continuous transition across resolutions (from 50 m to 100 km) is obtained, for dry convection, using exactly the same atmospheric model for all resolutions with a simple scale-adaptive mixing-length formulation.

scholarly journals Turbulence measurements with a tethered balloon

2016 ◽  
Author(s):  
G. Canut ◽  
F. Couvreux ◽  
M. Lothon ◽  
D. Legain ◽  
B. Piguet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Convective Boundary Layer ◽  
Motion Sensor ◽  
Tethered Balloon ◽  
Inertial Motion ◽  
Convective Boundary ◽  
Momentum Fluxes ◽  
Field Campaigns

Abstract. This study presents the first deployment of a turbulence probe below a tethered balloon in field campaigns. This system allows to measure turbulent temperature fluxes, momentum fluxes as well as turbulent kinetic energy in the lower part of the boundary layer. It is composed of a sonic thermoanemometer and inertial motion sensor. It has been validated during three campaigns with different convective boundary layer conditions using turbulent measurements from atmospheric towers and aircraft.

Derivation of Turbulent Kinetic Energy from a First-Order Nonlocal Planetary Boundary Layer Parameterization

2013 ◽  
Vol 70 (6) ◽  
pp. 1795-1805 ◽  
Author(s):  
Hyeyum Hailey Shin ◽  
Song-You Hong ◽  
Yign Noh ◽  
Jimy Dudhia
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Water Cycle ◽  
Convective Boundary ◽  
First Order ◽  
Eddy Simulation ◽  
Pbl Parameterization ◽  
Planetary Boundary Layer Parameterization

Abstract Turbulent kinetic energy (TKE) is derived from a first-order planetary boundary layer (PBL) parameterization for convective boundary layers: the nonlocal K-profile Yonsei University (YSU) PBL. A parameterization for the TKE equation is developed to calculate TKE based on meteorological profiles given by the YSU PBL model. For this purpose buoyancy- and shear-generation terms are formulated consistently with the YSU scheme—that is, the combination of local, nonlocal, and explicit entrainment fluxes. The vertical transport term is also formulated in a similar fashion. A length scale consistent with the K profile is suggested for parameterization of dissipation. Single-column model (SCM) simulations are conducted for a period in the second Global Energy and Water Cycle Experiment (GEWEX) Atmospheric Boundary Layer Study (GABLS2) intercomparison case. Results from the SCM simulations are compared with large-eddy simulation (LES) results. The daytime evolution of the vertical structure of TKE matches well with mixed-layer development. The TKE profile is shaped like a typical vertical velocity (w) variance, and its maximum is comparable to that from the LES. By varying the dissipation length from −23% to +13% the TKE maximum is changed from about −15% to +7%. After normalization, the change does not exceed the variability among previous studies. The location of TKE maximum is too low without the effects of the nonlocal TKE transport.

scholarly journals Scaling Laws for the Heterogeneously Heated Free Convective Boundary Layer

2014 ◽  
Vol 71 (11) ◽  
pp. 3975-4000 ◽  
Author(s):  
Chiel C. van Heerwaarden ◽  
Juan Pedro Mellado ◽  
Alberto De Lozar
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Convective Boundary Layer ◽  
Scaling Laws ◽  
Fixed Ratio ◽  
Buoyancy Flux ◽  
Convective Boundary ◽  
Optimal State ◽  
Surface Buoyancy ◽  
Surface Buoyancy Flux

Abstract The heterogeneously heated free convective boundary layer (CBL) is investigated by means of dimensional analysis and results from large-eddy simulations (LES) and direct numerical simulations (DNS). The investigated physical model is a CBL that forms in a linearly stratified atmosphere heated from the surface by square patches with a high surface buoyancy flux. Each simulation has been run long enough to show the formation of a peak in kinetic energy, corresponding to the “optimal” heterogeneity size with strong secondary circulations, and the subsequent transition into a horizontally homogeneous CBL. Scaling laws for the time of the optimal state and transition and for the vertically integrated kinetic energy (KE) have been developed. The laws show that the optimal state and transition do not occur at a fixed ratio of the heterogeneity size to the CBL height. Instead, these occur at a higher ratio for simulations with increasing heterogeneity sizes because of the development of structures in the downward-moving air that grow faster than the CBL thickness. The moment of occurrence of the optimal state and transition are strongly related to the heterogeneity amplitude: stronger amplitudes result in an earlier optimal state and a later transition. Furthermore, a decrease in patch size combined with a compensating increase in patch surface buoyancy flux to maintain the energy input results in decreasing KE and a later transition. The simulations suggest that a CBL with a heterogeneity size smaller than the initial CBL height has less entrainment than a horizontally homogeneous CBL, whereas one with a larger heterogeneity size has more.

Application of a K-ε Turbulence Model to Natural Convection From a Vertical Isothermal Surface

1977 ◽  
Vol 99 (1) ◽  
pp. 79-85 ◽  
Author(s):  
O. A. Plumb ◽  
L. A. Kennedy
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Energy Dissipation Rate ◽  
Convective Boundary ◽  
Wall Functions ◽  
Isothermal Surface ◽  
Turbulent Momentum ◽  
Energy Equations

A K-ε turbulence model similar to that proposed by Jones and Launder is applied to the calculation of the turbulent natural convective boundary layer on a vertical, isothermal surface. Conservation equations for the turbulent kinetic energy, dissipation rate of turbulent kinetic energy, and mean square temperature fluctuations are solved numerically along with the turbulent momentum and energy equations using the Spalding-Patankar boundary layer method. Various model constants and wall functions, and wall terms were tested. The results are compared with available experimental data and found to be in reasonable agreement.

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