A high-order SPH method by introducing inverse kernels

The smoothed particle hydrodynamics (SPH) method is usually expected to be an effi-cient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by intro-ducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square (LS) and Moving-Least-Square (MLS) methods. Then detailed analysis in spectral space is presented for people to better under-stand this method. Finally we show three test examples to verify the method behavior.     

Chicxulub and climate: radiative perturbations of impact-produced S-bearing gases

We use one-dimensional (1D) atmospheric models coupled to a sulfate aerosol model to investigate climate forcing and short-term response to stratospheric sulfate aerosols produced by the reaction of S-bearing gases and water vapor released in the Chicxulub impact event. A 1D radiation model is used to assess the climate forcing due to the impact-related loading of S-bearing gases. The model suggests that a climate forcing 100 times larger than that from the Pinatubo volcanic eruption is associated with the Chicxulub impact event for at least 2 years after the impact. In particular, we find a saturation effect in the forcing, that is, there is no significant difference in the maximum forcing between the highest (approximately 300 Gt) and lowest (approximately 30 Gt) estimated stratospheric S-loading from the Chicxulub impact. However, higher S-loads increase the overall duration of the forcing by several months. We use a single column model for a preliminary investigation of the short-term climate response to the impact-related production of sulfate aerosols (the lack of horizontal feedbacks limits the usefulness of the single column model to the first few days after the impact). Compared with the present steady-state climate, the introduction of large amounts of sulfate aerosols in the stratosphere results in a significant cooling of the Earth's surface. A long-term climate response can only be investigated with the use of a three-dimensional atmospheric model, which allows for the atmospheric circulation to adjust to the perturbation. Overall, although the climate perturbation to the forcing appears to be relatively large, the geologic record shows no sign of a significant long-term climatic shift across the K/T boundary, which is indicative of a fast post-impact climatic recovery.