A new class of adaptive high-order targeted ENO schemes for hyperbolic conservation laws

In [Fu et al., JCP 305(2016): 333-359], a family of high-order targeted ENO (TENO) schemes with a new nonlinear weighting strategy has been proposed. Building upon this strategy, in the current paper, a new class of adaptive TENO schemes for hyperbolic conservation laws is proposed based on three new concepts: (1) a hierarchical voting strategy is proposed to improve the ENO-like stencil selection; (2) the TENO weighting strategy is extended to function as a built-in discontinuity-location detector. Since the reconstruction scheme must not cross any discontinuity, corresponding target schemes are selected from a set of predefined linear schemes which are optimized towards maximum accuracy order or spectral resolution; (3) based on the observation that the cut-off parameter $C_T$ in the TENO weighting strategy determines nonlinear dissipation, a $C_T$ adaptation strategy is developed to minimize numerical dissipation for high-wavenumber fluctuations while maintaining robustness for shock-capturing. Six-point and eight-point TENO schemes are constructed, and their spectral properties are analyzed by the ADR analysis. A set of benchmark cases is considered to demonstrate the performance of proposed adaptive TENO schemes. Numerical results suggest that the proposed TENO schemes preserve the accuracy order at first and second order critical points and show less numerical dissipation compared with typical WENO schemes. Moreover, the TENO8-NA scheme exhibits good results for both highly compressible flows and nearly incompressible turbulence.

A targeted ENO scheme as implicit model for turbulent and genuine subgrid scales

Even for state-of-the-art implicit LES (ILES) methods, where the truncation error acts as physically-motivated subgrid-scale model, simultaneously resolving turbulent and genuine non-turbulent subgrid scales is an open challenge. For the purpose of dealing with non-turbulent subgrid scales, such as shocks, extra sensors, which often are case-dependent, are generally employed. The problem originates in the lack of scale-separation between low-wavenumber resolved-scale regions, high-wavenumber resolved or non-resolved fluctuations, and discontinuities. The targeted ENO (TENO) approach allows for separately designing the dispersive and dissipative truncation error components. Thus it provides a suitable environment to develop an implicit LES model. In this paper, we extend previous work and propose a variant of TENO family scheme [Fu et al., JCP 305 (2016): 333-359], which can separate resolved and nonresolved scales effectively. The novel idea is to propose a nonlinear dissipation-control strategy by adapting the cut-off parameter $C_T$ dynamically while measuring the nonsmoothness based on the first-order undivided difference. Low-wavenumber smooth scales are handled by an optimized linear scheme while high-wavenumber components, that involve nonresolved fluctuations and discontinuities, are subjected to adaptive nonlinear dissipation. The new scheme is Galilean invariant and free from sensors relating to specific physical phenomenon. A set of benchmark simulations with a wide range of length-scales and with discontinuities has been conducted without specific parameter adaptation. Numerical experiments demonstrate that the proposed TENO8-A scheme exhibits robust shock-capturing and high wave-resolution properties, and that it is suitable for simulating flow fields that contain isotropic turbulence and shocks. It is a promising alternative to other viable approaches.

The two-dimensional detonation with TENO scheme.

Thanks to the collaborative work of Haibo Dong, Fan Zhang and et al., we have extended the high-order TENO schemes to very complex detonation simulations, e.g. the two-dimensional detonation with TENO scheme.