Direct numerical simulations of multi-mode immiscible Rayleigh-Taylor instability with high Reynolds numbers

2019 ◽  
Vol 31 (11) ◽  
pp. 112104 ◽  
Keyword(s):  
Numerical Simulations ◽  
Reynolds Numbers ◽  
Direct Numerical Simulations ◽  
Taylor Instability ◽  
High Reynolds Numbers ◽  
Rayleigh Taylor Instability ◽  
High Reynolds ◽  
Multi Mode

The scaling of the turbulent/non-turbulent interface at high Reynolds numbers

2018 ◽  
Vol 843 ◽  
pp. 156-179 ◽  
Author(s):  
Tiago S. Silva ◽  
Marco Zecchetto ◽  
Carlos B. da Silva
Keyword(s):  
Numerical Simulations ◽  
Reynolds Numbers ◽  
Direct Numerical Simulations ◽  
Micro Scale ◽  
High Reynolds Numbers ◽  
High Reynolds

The scaling of the turbulent/non-turbulent interface (TNTI) at high Reynolds numbers is investigated by using direct numerical simulations (DNS) of temporal turbulent planar jets (PJET) and shear free turbulence (SFT), with Reynolds numbers in the range $142\leqslant Re_{\unicode[STIX]{x1D706}}\leqslant 400$. For $Re_{\unicode[STIX]{x1D706}}\gtrsim 200$ the thickness of the TNTI ($\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D714}}$), like that of its two sublayers – the viscous superlayer (VSL, $\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}$) and the turbulent sublayer (TSL, $\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D70E}}$) – all scale with the Kolmogorov micro-scale $\unicode[STIX]{x1D702}$, while the particular scaling constant depends on the sublayer. Specifically, for $Re_{\unicode[STIX]{x1D706}}\gtrsim 200$ while the VSL is always of the order of $\unicode[STIX]{x1D702}$, with $4\leqslant \langle \unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}\rangle /\unicode[STIX]{x1D702}\leqslant 5$, the TSL and the TNTI are typically equal to $10\unicode[STIX]{x1D702}$, with $10.4\leqslant \langle \unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D70E}}\rangle /\unicode[STIX]{x1D702}\leqslant 12.5$, and $15.4\leqslant \langle \unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D714}}\rangle /\unicode[STIX]{x1D702}\leqslant 16.8$, respectively.

scholarly journals Direct Numerical Simulations of Type Ia Supernovae Flames. II. The Rayleigh‐Taylor Instability

2004 ◽  
Vol 608 (2) ◽  
pp. 883-906 ◽  
Author(s):  
J. B. Bell ◽  
M. S. Day ◽  
C. A. Rendleman ◽  
S. E. Woosley ◽  
M. Zingale
Keyword(s):  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Taylor Instability ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Rayleigh Taylor Instability ◽  
Ia Supernovae

Reynolds- and Mach-number effects in canonical shock–turbulence interaction

2013 ◽  
Vol 717 ◽  
pp. 293-321 ◽  
Author(s):  
Johan Larsson ◽  
Ivan Bermejo-Moreno ◽  
Sanjiva K. Lele
Keyword(s):  
Shock Wave ◽  
Numerical Scheme ◽  
Isotropic Turbulence ◽  
Reynolds Numbers ◽  
Linear Analysis ◽  
Direct Numerical Simulations ◽  
High Reynolds Numbers ◽  
Grid Convergence ◽  
Post Shock ◽  
High Reynolds

AbstractThe interaction between isotropic turbulence and a normal shock wave is investigated through a series of direct numerical simulations at different Reynolds numbers and mean and turbulent Mach numbers. The computed data are compared to experiments and linear theory, showing that the amplification of turbulence kinetic energy across a shock wave is described well using linearized dynamics. The post-shock anisotropy of the turbulence, however, is qualitatively different from that predicted by linear analysis. The jumps in mean density and pressure are lower than the non-turbulent Rankine–Hugoniot results by a factor of the square of the turbulence intensity. It is shown that the dissipative scales of turbulence return to isotropy within about 10 convected Kolmogorov time scales, a distance that becomes very small at high Reynolds numbers. Special attention is paid to the ‘broken shock’ regime of intense turbulence, where the shock can be locally replaced by smooth compressions. Grid convergence of the probability density function of the shock jumps proves that this effect is physical, and not an artefact of the numerical scheme.

The vortex-induced forces on a multi-column platform in current at high Reynolds numbers

2018 ◽  
Vol 32 (29) ◽  
pp. 1850356 ◽  
Author(s):  
Xiaofeng Hu ◽  
Xinshu Zhang ◽  
Yunxiang You
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Transverse Force ◽  
Single Cylinder ◽  
Force Coefficients ◽  
High Reynolds Numbers ◽  
The Mean ◽  
High Reynolds ◽  
Current Incidence

The unsteady vortex-induced forces on a multi-column platform in current from subcritical up to supercritical Reynolds numbers have been investigated using three-dimensional numerical simulations. Two different current incidences, 0[Formula: see text] and 45[Formula: see text], are considered. The results show that for 0[Formula: see text] current incidence, the mean streamwise force coefficients [Formula: see text] increase with the rise of [Formula: see text] when [Formula: see text], while they grow slightly when [Formula: see text]. For 45[Formula: see text] current incidence, a decrease of streamwise force with increasing [Formula: see text] is observed. Similar to a single cylinder, the fluctuating transverse force coefficients [Formula: see text] of the multi-column platform drop at [Formula: see text] for 0[Formula: see text] and 45[Formula: see text] current incidences. In addition, it is found that for 0[Formula: see text] current incidence, the [Formula: see text] values of the downstream columns are much larger than those of the upstream columns, while for 45[Formula: see text] current incidence, the [Formula: see text] values of each column are similar. Furthermore, the results of correlations between the forces on each column and total forces indicates that for 0[Formula: see text] current incidence, the fluctuating transverse forces on the downstream columns are mainly responsible for the total fluctuating transverse force on the multi-column platform.

scholarly journals Experimental Evidence of the Kraichnan Scalar Spectrum at High Reynolds Numbers

2012 ◽  
Vol 42 (10) ◽  
pp. 1717-1728 ◽  
Author(s):  
D. J. Bogucki ◽  
H. Luo ◽  
J. A. Domaradzki
Keyword(s):  
Temperature Gradient ◽  
Reynolds Numbers ◽  
Passive Scalar ◽  
Direct Numerical Simulations ◽  
Horizontal Temperature Gradient ◽  
Spectral Form ◽  
High Reynolds Numbers ◽  
Flow Reynolds Number ◽  
M 12 ◽  
High Reynolds

Abstract Measurements of horizontal temperature gradient spectra were carried out in a 25 m × 12 m × 3 m freshwater well mixed swimming pool. The associated flow Reynolds number was found to vary from 4 × 103 to 6 × 103. In all analyzed cases, at large wavenumbers k, the temperature gradient spectra exhibited behavior consistent with the Kraichnan spectral form: ~exp[−(6qk)1/2k] with constant . The measurements are in agreement with direct numerical simulations of a passive scalar flow with of Bogucki et al. and with recent experimental observations of Sanchez et al.

scholarly journals A Numerical and Experimental Study of the Aerodynamics and Stability of a Horizontal Parachute

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Mazyar Dawoodian ◽  
Abdolrahman Dadvand ◽  
Amir Hassanzadeh
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Drag Coefficient ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
The Stability ◽  
Good Agreement

The flow past a parachute with and without a vent hole at the top is studied both experimentally and numerically. The effects of Reynolds number and vent ratio on the flow behaviour as well as on the drag coefficient are examined. The experiments were carried out under free-flow conditions. In the numerical simulations, the flow was considered as unsteady and turbulent and was modelled using the standard - turbulence model. The experimental results reveal good agreement with the numerical ones. In both the experiments and numerical simulations, the Reynolds number was varied from 85539 to 357250 and the vent ratio was increased from zero to 20%. The results show that the drag coefficient decreases by increasing the Reynolds number for all the cases tested. In addition, it was found that at low and high Reynolds numbers, the parachutes, respectively, with 4% vent ratio and without vent are deemed more efficient. One important result of the present work is related to the effect of vent ratio on the stability of the parachute.

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