scholarly journals Bottlenecks in turbulent kinetic energy spectra predicted from structure function inflections using the Von Kármán-Howarth equation

2015 ◽  
Vol 92 (3) ◽  
Author(s):  
Gabriel G. Katul ◽  
Costantino Manes ◽  
Amilcare Porporato ◽  
Elie Bou-Zeid ◽  
Marcelo Chamecki
Keyword(s):  
Kinetic Energy ◽  
Structure Function ◽  
Turbulent Kinetic Energy ◽  
Energy Spectra ◽  
Von Karman ◽  
Von Kármán

Turbulence Measurements from Five-Beam Acoustic Doppler Current Profilers

2017 ◽  
Vol 34 (6) ◽  
pp. 1267-1284 ◽  
Author(s):  
Maricarmen Guerra ◽  
Jim Thomson
Keyword(s):  
Kinetic Energy ◽  
Structure Function ◽  
Turbulent Kinetic Energy ◽  
Puget Sound ◽  
Inertial Subrange ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Frequency Spectra ◽  
Turbulence Data ◽  
Acoustic Doppler Current Profilers

AbstractTwo new five-beam acoustic Doppler current profilers—the Nortek Signature1000 AD2CP and the Teledyne RDI Sentinel V50—are demonstrated to measure turbulence at two energetic tidal channels within Puget Sound, Washington. The quality of the raw data is tested by analyzing the turbulent kinetic energy frequency spectra, the turbulence spatial structure function, the shear in the profiles, and the covariance Reynolds stresses. The five-beam configuration allows for a direct estimation of the Reynolds stresses from along-beam velocity fluctuations. The Nortek’s low Doppler noise and high sampling frequency allow for the observation of the turbulent inertial subrange in both the frequency spectra and the turbulence structure function. The turbulence parameters obtained from the five-beam acoustic Doppler current profilers are validated with turbulence data from simultaneous measurements with acoustic Doppler velocimeters. These combined results are then used to assess a turbulent kinetic energy budget in which depth profiles of the turbulent kinetic energy dissipation and production rates are compared. The associated codes are publicly available on the MATLAB File Exchange website.

scholarly journals Measurement of turbulence properties

2020 ◽  
Vol 14 (1) ◽  
pp. 67-75
Author(s):  
Dávid Faragó ◽  
Péter Bencs
Keyword(s):  
Turbulence Models ◽  
Industrial Applications ◽  
Energy Spectra ◽  
Reynolds Stresses ◽  
Theoretical Understanding ◽  
Anisotropic Turbulence ◽  
Von Karman ◽  
Anisotropic Energy ◽  
Von Kármán ◽  
Turbulence Grid

The aim of the research is to investigate anisotropic turbulence intensities, id est to investigate the distribution of Reynolds stresses and energy spectra in a square cross-section channel, downstream of a semi-active jet turbulence grid generating anisotropic turbulent airflow. In addition to the semi-active jet turbulence grid, another type of turbulence grid was developed and experimentally investigated. This grid contains vertical, flexible strips of aluminum (in this case, there are no perpendicular (horizontal) grid elements), which vibrate at a frequency depending on the velocity of the main airflow. Besides the investigation of the velocity- and turbulence intensity distributions, another main objective of the research is to measure the von Kármán energy spectrum when the turbulence cannot be considered isotropic. This aspiration of ours is justified by the knowledge gap present in the literature in this specific field. Monin has carried out a theoretical study to extend and generalize the von Kármán – Howarth isotropic principal stress equation to the anisotropic regime. The proposed new experimental work aims to provide a solid experimental background for verifying and validating the physical correctness of the Monin equation, which may result in a new theoretical understanding and perception of the major issues and the nature of anisotropic turbulence. Since the anisotropic energy spectra are expected to exhibit different characteristics from the isotropic Kolmogorov spectra, these new experimental results may contribute to the development of new anisotropic and engineering turbulence models that can be used in industrial applications.

scholarly journals IWC Analysis of Turbulent Plume Fires

2021 ◽  
Vol 65 (2-4) ◽  
pp. 196-200
Author(s):  
Francesco S. Ciani ◽  
Paolo Bonfiglio ◽  
Stefano Piva
Keyword(s):  
Spectral Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Power Law ◽  
Grid Size ◽  
Energy Spectra ◽  
Test Case ◽  
Wavenumber Domain ◽  
Taylor’S Hypothesis ◽  
Turbulent Plume

Plumes fires are characterized by a turbulent nature with a large number of different scales. LES is used to solve the largest structures and to model the smallest ones. Grid size and time steps become decisive to place a limit between solved and modelled turbulence. A spectral analysis, both in frequency and wavenumber domain of the specific turbulent kinetic energy is an instrument to check for the information investigated. Unfortunately, the spectra in the wavenumber domain can be difficult to achieve adequately, because the specific turbulent kinetic energy values should be available in many points. This issue can be overcome by identifying a correlation law between frequencies and wavenumbers. An approach to identify this correlation law can be to adopt the IWC method. Here, for a test case of a turbulent reacting plume of burning propane, specific turbulent kinetic energy is analysed both in frequency and wavenumber and a correlation law between them is identified by using the IWC method. A study has been performed to evaluate the grid dependency of the specific turbulent kinetic energy spectra, by assessing the extension of the Kolmogorov power law region. The correlation results are discussed and compared with the Taylor’s hypothesis.

scholarly journals Correcting Surface Wave Bias in Structure Function Estimates of Turbulent Kinetic Energy Dissipation Rate

2017 ◽  
Vol 34 (10) ◽  
pp. 2257-2273 ◽  
Author(s):  
Brian D. Scannell ◽  
Tom P. Rippeth ◽  
John H. Simpson ◽  
Jeff A. Polton ◽  
Joanne E. Hopkins
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Structure Function ◽  
Turbulent Kinetic Energy ◽  
Vertical Gradient ◽  
Energy Dissipation Rate ◽  
Oceanic Turbulence ◽  
Modified Method ◽  
Wide Range ◽  
Acoustic Doppler Current Profilers

AbstractThe combination of acoustic Doppler current profilers and the structure function methodology provides an attractive approach to making extended time series measurements of oceanic turbulence (the rate of turbulent kinetic energy dissipation ε) from moorings. However, this study shows that for deployments in the upper part of the water column, estimates of ε will be biased by the vertical gradient in wave orbital velocities. To remove this bias, a modified structure function methodology is developed that exploits the differing length scale dependencies of the contributions to the structure function resulting from turbulent and wave orbital motions. The success of the modified method is demonstrated through a comparison of ε estimates based on data from instruments at three depths over a 3-month period under a wide range of conditions, with appropriate scalings for wind stress and convective forcing.

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