Stratified Kelvin–Helmholtz turbulence of compressible shear flows

San, Omer; Maulik, Romit

We study scaling laws of stratified shear flows by performing high-resolution numerical simulations of inviscid compressible turbulence induced by Kelvin–Helmholtz instability. An implicit large eddy simulation approach is adapted to solve our conservation laws for both two-dimensional (with a spatial resolution of 16 384inline-formula2) and three-dimensional (with a spatial resolution of 512inline-formula3) configurations utilizing different compressibility characteristics such as shocks. For three-dimensional turbulence, we find that both the kinetic energy and density-weighted energy spectra follow the classical Kolmogorov inline-formula M3inlinescrollmathml k - normal 5 / normal 3 28pt14ptsvg-formulamathimg31e02f6fec8a944189706d77f1a9cdf1 npg-25-457-2018-ie00001.svg28pt14ptnpg-25-457-2018-ie00001.png inertial scaling. This phenomenon is observed due to the fact that the power density spectrum of three-dimensional turbulence yields the same inline-formula M4inlinescrollmathml k - normal 5 / normal 3 28pt14ptsvg-formulamathimg606a13185139bfb9d3bfcdf17275b8f3 npg-25-457-2018-ie00002.svg28pt14ptnpg-25-457-2018-ie00002.png scaling. However, we demonstrate that there is a significant difference between these two spectra in two-dimensional turbulence since the power density spectrum yields a inline-formula M5inlinescrollmathml k - normal 5 / normal 3 28pt14ptsvg-formulamathimg5c458c9911acbbfab2d9e74a47119f91 npg-25-457-2018-ie00003.svg28pt14ptnpg-25-457-2018-ie00003.png scaling. This difference may be assumed to be a reason for the inline-formula M6inlinescrollmathml k - normal 7 / normal 3 28pt14ptsvg-formulamathimgd5c7ed4793c3c6eae8d3ae03c4794559 npg-25-457-2018-ie00004.svg28pt14ptnpg-25-457-2018-ie00004.png scaling observed in the two-dimensional density-weight kinetic every spectra for high compressibility as compared to the inline-formulak−3 scaling traditionally assumed with incompressible flows. Further inquiries are made to validate the statistical behavior of the various configurations studied through the use of the Helmholtz decomposition of both the kinetic velocity and density-weighted velocity fields. We observe that the scaling results are invariant with respect to the compressibility parameter when the density-weighted definition is used. Our two-dimensional results also confirm that a large inertial range of the solenoidal component with the inline-formulak−3 scaling can be obtained when we simulate with a lower compressibility parameter; however, the compressive spectrum converges to inline-formulak−2 for a larger compressibility parameter.

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San, Omer / Maulik, Romit: Stratified Kelvin–Helmholtz turbulence of compressible shear flows. 2018. Copernicus Publications.

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Rechteinhaber: Omer San

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