Estimates of turbulent kinetic energy dissipation rate for a stratified flow in a wind tunnel

Puhales, Franciano Scremin; Demarco, Giuliano; Martins, Luís Gustavo Nogueira; Acevedo, Otávio C.; Degrazia, Gervásio Annes; Welter, Guilherme Sausen; Costa, Felipe Denardin; Fisch, Gilberto; Avelar, Ana Cristina

doi:10.1016/j.physa.2015.03.008

Cited by 15 publications

(6 citation statements)

References 19 publications

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“…TKE dissipation rate ϵ is determined from the second‐order structure function

S_{u}^{2}

through the relationship

S_{u}^{2} ((), r) = C_{k} ϵ^{2 true/ 3} r^{2 true/ 3}

, valid for the inertial subrange (Panchev, ), where C k is Kolmogorov's constant, assumed to be 2.13 (Sreenivasan, ), and r is the eddy spatial scale. The inertial subrange is determined by assuming that the exponent that best fits the structure function is within 5% of the 2/3 value prescribed by Kolmogorov's law and that such a fitting has at least 80% of correlation with the observed structure function (Puhales et al , ). Dissipation rates from series that do not fulfil these requirements, totalling 4.8% of the total dataset, have been discarded.…”

Section: Data and Analysismentioning

confidence: 99%

Contrasting structures between the decoupled and coupled states of the stable boundary layer

Acevedo

Mahrt

Puhales

et al. 2015

Quart J Royal Meteoro Soc

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Different aspects of the stable boundary-layer structure are contrasted between the very stable and the weakly stable regimes from a new point of view. This study finds a limit wind speed, referred to as the crossover threshold, when the average vertical gradient of the turbulent kinetic energy switches sign at all observational levels. When the wind speed exceeds this transition, the entire stable boundary layer becomes vertically fully coupled. Consequently the very stable boundary layer in this study is considered as a decoupled regime, while the weakly stable state is referred to as a coupled regime. It is shown that the vertical profiles of other quantities, such as friction velocity, heat flux and thermal gradients are strikingly different between the two coupling states.Decomposition of turbulent kinetic energy and heat flux into temporal scales indicates overlapping of non-turbulent sub-mesoscale flow with turbulence in the decoupled case, while there is a clearer scale distinction between the two types of motions when coupling takes place. The turbulent kinetic energy budget is dominated by dissipation and shear production in both coupling states. However, the relative importance of the buoyant destruction term is shown to be appreciably larger in the decoupled regime. In the heat flux budget equation, buoyant destruction is larger in magnitude than production by the thermal gradient in the decoupled case, but not when there is full coupling. These results indicate that the surface heat flux plays a major role in controlling the stable boundary-layer state, as previously proposed. For the entire dataset, the frequency distributions of turbulence quantities near the surface are shown to be bimodal. The two modes are associated with the two coupling states, each well described by independent log-normal distributions.

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“…TKE dissipation rate ϵ is determined from the second‐order structure function

S_{u}^{2}

through the relationship

S_{u}^{2} ((), r) = C_{k} ϵ^{2 true/ 3} r^{2 true/ 3}

Section: Data and Analysismentioning

confidence: 99%

Contrasting structures between the decoupled and coupled states of the stable boundary layer

Acevedo

Mahrt

Puhales

et al. 2015

Quart J Royal Meteoro Soc

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“…This result is coherent since the values of TKE and rms velocity for SWD are also smaller than for LWD wind. A tight correlation of ε with TKE was highlighted by Puhales et al [31].…”

Section: Probability Density Of Energy Dissipation Rate and Length-sc...mentioning

confidence: 84%

“…This result is coherent since the values of TKE and rms velocity for SWD are also smaller than for LWD wind. A tight correlation of ε with TKE was highlighted by Puhales et al [31]. The turbulence length-scale (L) which is known as the dissipation length is calculated using the dissipation rate and TKE.…”

Section: Probability Density Of Energy Dissipation Rate and Length-sc...mentioning

confidence: 97%

Turbulence of Landward and Seaward Wind during Sea-Breeze Days within the Lower Atmospheric Boundary Layer

et al. 2021

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Reynolds stress anisotropy is estimated from the stress spheroids, based on 20 Hz ultrasonic anemometer measurements, performed in the coastal area of northern France, over a 1.5-year long period. Size and shape variation (i.e., prolate, oblate, disk, rod, etc.) of stress spheroids are used for the characterization of energy redistribution by turbulent eddies. The sea-breeze (SB) events were identified using a change in wind direction from seaward (SWD) to landward (LWD) during the day time. We found that the LWD wind creates more turbulent anisotropic states than SWD wind. The prolate-shaped stress spheroids correspond to small-scale turbulence observed during LWD wind, while oblate spheroids are found during SWD winds. Moreover, it was found that during LWD winds, large turbulence kinetic energy (TKE) in the flow field produces large stress spheroids. On the contrary, during SWD winds, a smaller level of TKE is responsible for small-size stress spheroid formation. The average volume of the corresponding Reynolds stress spheroids during the LWD is 13% larger than that of during SWD wind.

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“…Utilizando este mesmo conjunto de medidas, Puhales et al (2015) identificou anomalias nas funções estruturas calculadas devido à presença de ruído de alta frequência. Neste mesmo estudo, foi utilizado um processo de filtragem (passa-baixa) baseado na DME…”

Section: Resultsunclassified

Aplicação da Transformada de Hilbert-Huang em dados de velocidade medidos em túnel de vento

Martins

Demarco

Puhales

et al. 2018

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In this study, the Hilbert-Huang transform was applied to experimental measurements performed in a wind tunnel to determine the frequency of occurrence of the spectral maximum. These maximum frequencies are associated with the time scale of the most energetic eddies and represent an important input parameter in the pollutants dispersion models. The values of the maximum frequencies obtained by the Hilbert-Huang marginal spectrum are compared with the vaues obtained by the traditionally used Fourier transform. The results show that the energy distribution calculated by both methods are very similar in the region of occurence of the spectral maximum, and for this reason, the maximum frequency values obtained by each method do not presente significant differences. Under determined hypothesis, the Hilbert-Huang transform provided physically more realistic maximum frequency values that those obtained using the Fourier transform.

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Estimates of turbulent kinetic energy dissipation rate for a stratified flow in a wind tunnel

Cited by 15 publications

References 19 publications

Contrasting structures between the decoupled and coupled states of the stable boundary layer

Contrasting structures between the decoupled and coupled states of the stable boundary layer

Turbulence of Landward and Seaward Wind during Sea-Breeze Days within the Lower Atmospheric Boundary Layer

Aplicação da Transformada de Hilbert-Huang em dados de velocidade medidos em túnel de vento

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