scholarly journals The Batchelor Spectrum of Passive Scalar Turbulence in Stochastic Fluid Mechanics at Fixed Reynolds Number

2021 ◽  
Author(s):  
Jacob Bedrossian ◽  
Alex Blumenthal ◽  
Samuel Punshon‐Smith
Keyword(s):  
Reynolds Number ◽  
Fluid Mechanics ◽  
Passive Scalar ◽  
Scalar Turbulence ◽  
Stochastic Fluid

scholarly journals Fronts in passive scalar turbulence

2001 ◽  
Vol 13 (6) ◽  
pp. 1768-1783 ◽  
Author(s):  
A. Celani ◽  
A. Lanotte ◽  
A. Mazzino ◽  
M. Vergassola
Keyword(s):  
Passive Scalar ◽  
Scalar Turbulence

scholarly journals Anisotropic fluctuations in passive scalar turbulence with a uniform mean gradient

2019 ◽  
Vol 2019 (0) ◽  
pp. OS8-02
Author(s):  
Tatsuya YASUDA ◽  
Toshiyuki GOTOH ◽  
Takeshi WATANABE ◽  
Izumi SAITO
Keyword(s):  
Passive Scalar ◽  
Scalar Turbulence

Numerical shape optimization in Fluid Mechanics at low Reynolds number

2019 ◽  
Author(s):  
Alexis Courtais ◽  
Francois Lesage ◽  
Yannick Privat ◽  
Pascal Frey ◽  
Abderrazak M. Latifi
Keyword(s):  
Reynolds Number ◽  
Fluid Mechanics ◽  
Shape Optimization ◽  
Low Reynolds Number ◽  
Low Reynolds

Inertial-range intermittency and accuracy of direct numerical simulation for turbulence and passive scalar turbulence

2007 ◽  
Vol 590 ◽  
pp. 117-146 ◽  
Author(s):  
TAKESHI WATANABE ◽  
TOSHIYUKI GOTOH
Keyword(s):  
Spatial Resolution ◽  
Passive Scalar ◽  
Inertial Range ◽  
Flow Dynamics ◽  
Eighth Order ◽  
Range Resolution ◽  
Filter Width ◽  
Scalar Turbulence ◽  
Grid Points ◽  
Dissipation Range

We examine the effects of the variation in dissipation-range resolution on the accuracy of inertial-range statistics and intermittency in terms of the direct numerical simulations of homogeneous turbulence and passive-scalar turbulence by changing the spatial resolution up to 20483 grid points while maintaining a constant Reynolds number at Rλ ≃ 180 or ≃ 420 and Schmidt number at Sc = 1. Although large fluctuations of the derivative fields depended strongly on Kmaxη and were underestimated when Kmaxη≃1, where Kmax is the maximum wavenumber in the computations and η is the mean Kolmogorov length, the behaviour of the spectra and the scaling exponents of the structure functions up to the eighth order in the range of scales greater than 10η was insensitive to variations in Kmaxη, even when Kmaxη≃1. The relationship between the spatial resolution and asymptotic tail of the probability density functions of the energy dissipation fields was studied using the multifractal model for dissipation, and the results were confirmed by comparison to the simulation data. Degradation of the statistics arises from modifications to the flow dynamics due to the finite wavenumber cutoff and the use of a coarser filter width for the data, which is obtained using a reasonable accuracy criterion for the flow dynamics. The effect of the former was less than that of the latter for the low-to-moderate-order statistics when Kmaxη≥1. We also discuss the universality of the inertial-range statistics with respect to variations in the dissipation-range characteristics.

Mixed velocity–passive scalar statistics in high-Reynolds-number turbulence

2003 ◽  
Vol 475 ◽  
pp. 173-203 ◽  
Author(s):  
L. MYDLARSKI
Keyword(s):  
Reynolds Number ◽  
Transverse Velocity ◽  
Reynolds Numbers ◽  
Passive Scalar ◽  
Inertial Range ◽  
Scaling Exponents ◽  
Local Isotropy ◽  
Exponential Tails ◽  
Reynolds Number Dependence ◽  
Scalar Fluctuation

Statistics of the mixed velocity–passive scalar field and its Reynolds number dependence are studied in quasi-isotropic decaying grid turbulence with an imposed mean temperature gradient. The turbulent Reynolds number (using the Taylor microscale as the length scale), Rλ, is varied over the range 85 [les ] Rλ [les ] 582. The passive scalar under consideration is temperature in air. The turbulence is generated by means of an active grid and the temperature fluctuations result from the action of the turbulence on the mean temperature gradient. The latter is created by differentially heating elements at the entrance to the wind tunnel plenum chamber. The mixed velocity–passive scalar field evolves slowly with Reynolds number. Inertial-range scaling exponents of the co-spectra of transverse velocity and temperature, Evθ(k1), and its real-space analogue, the ‘heat flux structure function,’ 〈Δv(r)Δθ(r)〉, show a slow evolution towards their theoretical predictions of −7/3 and 4/3, respectively. The sixth-order longitudinal mixed structure functions, 〈(Δu(r))2(Δθ(r))4〉, exhibit inertial-range structure function exponents of 1.36–1.52. However, discrepancies still exist with respect to the various methods used to estimate the scaling exponents, the value of the scalar intermittency exponent, μθ, and the effects of large-scale phenomena (namely shear, decay and turbulent production of 〈θ2〉) on 〈(Δu(r))2(Δθ(r))4〉. All the measured fine-scale statistics required to be zero in a locally isotropic flow are, or tend towards, zero in the limit of large Reynolds numbers. The probability density functions (PDFs) of Δv(r)Δθ(r) exhibit roughly exponential tails for large separations and super-exponential tails for small separations, thus displaying the effects of internal intermittency. As the Reynolds number increases, the PDFs become symmetric at the smallest scales – in accordance with local isotropy. The expectation of the transverse velocity fluctuation conditioned on the scalar fluctuation is linear for all Reynolds numbers, with slope equal to the correlation coefficient between v and θ. The expectation of (a surrogate of) the Laplacian of the scalar reveals a Reynolds number dependence when conditioned on the transverse velocity fluctuation (but displays no such dependence when conditioned on the scalar fluctuation). This former Reynolds number dependence is consistent with Taylor’s diffusivity independence hypothesis. Lastly, for the statistics measured, no violations of local isotropy were observed.

scholarly journals Critical Geometry of Two-Dimensional Passive Scalar Turbulence

2001 ◽  
Vol 86 (26) ◽  
pp. 5890-5893 ◽  
Author(s):  
Jané Kondev ◽  
Greg Huber
Keyword(s):  
Passive Scalar ◽  
Two Dimensional ◽  
Scalar Turbulence
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