Visualizing the effects of distributed volume non-Kolmogorov and anisotropic turbulence on incoherent long horizontal-path imaging

The present work aims at developing a spectral model for a passive scalar field and its associated scalar flux in homogeneous anisotropic turbulence. This is achieved using the paradigm of eddy-damped quasi-normal Markovian (EDQNM) closure extended to anisotropic flows. In order to assess the validity of this approach, the model is compared to several detailed direct numerical simulations (DNS) and experiments of shear-driven flows and isotropic turbulence with a mean scalar gradient at moderate Reynolds numbers. This anisotropic modelling is then used to investigate the passive scalar dynamics at very high Reynolds numbers. In the framework of homogeneous isotropic turbulence submitted to a mean scalar gradient, decay and growth exponents for the cospectrum and scalar energies are obtained analytically and assessed numerically thanks to EDQNM closure. With the additional presence of a mean shear, the scaling of the scalar flux and passive scalar spectra in the inertial range are investigated and confirm recent theoretical predictions. Finally, it is found that, in shear-driven flows, the small scales of the scalar second-order moments progressively return to isotropy when the Reynolds number increases.

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Linear forcing for numerical generation of anisotropic turbulence field

Journal of the Japan Society of Naval Architects and Ocean Engineers ◽

10.2534/jjasnaoe.8.53 ◽

2008 ◽

Vol 8 (0) ◽

pp. 53-59

Author(s):

Shinichiro Hirabayashi ◽

Toru Sato

Keyword(s):

Anisotropic Turbulence ◽

Numerical Generation

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Research on the Influence of Ocean Atmosphere to Infrared Detection

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.1698 ◽

2012 ◽

Vol 472-475 ◽

pp. 1698-1701 ◽

Cited By ~ 1

Author(s):

Yu Chen ◽

Yunan Hu ◽

Kun Hu Kou ◽

Hai Jun Li ◽

Gang Zhang

Keyword(s):

Boundary Layer ◽

Infrared Detection ◽

Infrared Transmission ◽

Horizontal Path ◽

Atmospheric Window ◽

Ocean Atmosphere ◽

Slant Path ◽

Atmospheric Transmittance ◽

Total Transmittance ◽

Major Absorption Band

Ocean atmospheric transmittance is an important factor to influence detecting distance of infrared system. The influence efficiency of infrared detection is studied by using modtran, on the basis of studying the character of infrared transmission. Firstly, major absorption band of vapor, carbon dioxide, ozone and vapor continuum and the change of transmittance in boundary layer, troposphere and stratosphere are analyzed. Secondly, atmospheric window transmittance of navy maritime aerosol in horizontal path and slant path is analyzed, and the influence of four types of maritime aerosol is also analyzed for navy maritime aerosol. Lastly, the influence of five model atmospheres to total transmittance is analyzed.

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Fluctuations of radio occultation signals in X/K band in the presence of anisotropic turbulence and differential transmission retrieval performance

Radio Science ◽

10.1029/2006rs003544 ◽

2007 ◽

Vol 42 (4) ◽

pp. n/a-n/a ◽

Cited By ~ 16

Author(s):

M. E. Gorbunov ◽

G. Kirchengast

Keyword(s):

Radio Occultation ◽

Retrieval Performance ◽

Anisotropic Turbulence ◽

Differential Transmission ◽

K Band

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Application of advanced RANS turbulence models for the prediction of turbomachinery flows

Journal of Turbomachinery ◽

10.1115/1.4051938 ◽

2021 ◽

pp. 1-13

Author(s):

Ernesto Casartelli ◽

Luca Mangani ◽

David Roos Launchbury ◽

Armando Del Rio

Keyword(s):

Design Process ◽

Current Trend ◽

Turbulence Models ◽

Stability Limit ◽

Transport Equations ◽

Stability And Convergence ◽

Operating Characteristics ◽

Convergence Behavior ◽

Anisotropic Turbulence ◽

Rans Models

Abstract The current trend in turbomachinery towards broader operating characteristics requires that operating points in the off-design region can be captured accordingly from the simulation models. Complex processes like separation and vortex formation/dissipation occur under these conditions. Linear two equation models are often not able to represent these effects correctly since their derivation is based on over-simplifications, such as the Boussinesq hypothesis, which makes it impossible to capture anisotropic turbulence. Advanced RANS models are usually not considered in the design process of turbomachines because (1) they are usually more delicate with regards to stability and convergence behavior and (2) require additional computational effort. To make the usage of advanced RANS models more applicable for complex turbomachinery simulations a selected group of models were implemented into a robust framework of a pressure-based fully coupled solver. To further enhance stability, coupling terms between the turbulent transport equations were derived for several models. Anisotropic turbulence is introduced by computing an algebraic expression or by solving the transport equations for the Reynolds stress components. The evaluation of the models is performed on the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. For design conditions and operation points near the stability limit, all investigated turbulence models predict the compressor characteristic. Operation points in the choking region on the other hand are only predicted well by anisotropic models. The good results and improved convergence behavior of the advanced RANS models clearly indicates their applicability in the design process of turbomachines.

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