Direct Numerical Simulation of Rayleigh-Taylor ... - ASC at Livermore

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Setup for Rayleigh-Taylor DNS:‣ 3:1 density ratio (Atwood number = 0.5)‣ Schmidt number = ν/D = 1‣ Grid spacing Δ ≈ η (Kolmogorov scale)‣ 3072 x 3072 x 3072 grid points‣ Error function for diffuse initial interface (5 grid pointsthick) with horizontally perturbed position‣ Periodic side boundaries‣ Potential-flow vertical boundaries at early times‣ Free-slip walls at top and bottom boundariesViscous and diffusion scales are resolved.WC-IWPCTM10-6
Direct Numerical Simulation serves as alow-Re “numerical experiment”• DNS resolves all relevant scales in turbulentflow (inertial, dissipation, and diffusion);there are no model approximations.• Turbulence is inherently three-dimensional.• DNS is limited to low to moderate Reynoldsnumbers, constrained by computer resources.• To reach a fully turbulent state (e.g., mixing transition), the outerscaleReynolds number must exceed Re > 10 4 (microscale Re λ> 10 2 ).• The range of scales (∝ number of grid points Ν) in any direction isΛ/η ∼ Re 3/4 ; hence the cost of DNS ∼ Ν 4 ∼ Re 3 (assuming perfectparallel scaling).• DNS needs large resources to reach higher Re.BG/L is the fastest computer in the world.WC-IWPCTM10-7
Page 1 and 2: Direct Numerical Simulation ofRayle
Page 3 and 4: The Navier-Stokes equations have be
Page 5: Paris is the birthplace of the Navi
Page 9 and 10: There is not much pure light fluid
Page 11 and 12: Outer-scale Reynolds number reaches
Page 13 and 14: Peak of energy spectrum follows a k
Page 15 and 16: In the self-similar regime, (dh/dt)
Page 17 and 18: The mixing rate lags the entrainmen
Page 19 and 20: Self-similarity gives: λ∼h 1/4
Page 21 and 22: Similar trends were observed in a p
Page 23: DNS of R-T instability at Re up to

Direct Numerical Simulation of Rayleigh-Taylor ... - ASC at Livermore

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