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A hybrid stabilization technique for simulating water wave - Structure interaction by incompressible Smoothed Particle Hydrodynamics (ISPH) method
The Smoothed Particle Hydrodynamics (SPH) method is emerging as a potential tool for studying water wave related problems, especially for violent free surface flow and large deformation problems. The incompressible SPH (ISPH) computations have been found not to be able to maintain the stability in certain situations and there exist some spurious oscillations in the pressure time history, which is similar to the weakly compressible SPH (WCSPH). One main cause of this problem is related to the non-uniform and clustered distribution of the moving particles. In order to improve the model performance, the paper proposed an efficient hybrid numerical technique aiming to correct the ill particle distributions. The correction approach is realized through the combination of particle shifting and pressure gradient improvement. The advantages of the proposed hybrid technique in improving ISPH calculations are demonstrated through several applications that include solitary wave impact on a slope or overtopping a seawall, and regular wave slamming on the subface of open-piled structure
Hydrodynamic capabilities of an SPH code incorporating an artificial conductivity term with a gravity-based signal velocity
This paper investigates the hydrodynamic performances of an SPH code
incorporating an artificial heat conductivity term in which the adopted signal
velocity is applicable when gravity is present. In accordance with previous
findings it is shown that the performances of SPH to describe the development
of Kelvin-Helmholtz instabilities depend strongly on the consistency of the
initial condition set-up and on the leading error in the momentum equation due
to incomplete kernel sampling. An error and stability analysis shows that the
quartic B-spline kernel (M_5) possesses very good stability properties and we
propose its use with a large neighbor number, between ~50 (2D) to ~ 100 (3D),
to improve convergence in simulation results without being affected by the
so-called clumping instability. SPH simulations of the blob test show that in
the regime of strong supersonic flows an appropriate limiting condition, which
depends on the Prandtl number, must be imposed on the artificial conductivity
SPH coefficients in order to avoid an unphysical amount of heat diffusion.
Results from hydrodynamic simulations that include self-gravity show profiles
of hydrodynamic variables that are in much better agreement with those produced
using mesh-based codes. In particular, the final levels of core entropies in
cosmological simulations of galaxy clusters are consistent with those found
using AMR codes. Finally, results of the Rayleigh-Taylor instability test
demonstrate that in the regime of very subsonic flows the code has still
several difficulties in the treatment of hydrodynamic instabilities. These
problems being intrinsically due to the way in which in standard SPH gradients
are calculated and not to the implementation of the artificial conductivity
term.Comment: 26 pages, 15 figures, accepted for publication in A&
Study on SPH Viscosity Term Formulations
For viscosity-dominated flows, the viscous effect plays a much more important role. Since the viscosity term in SPH-governing (Smoothed Particle Hydrodynamics) equations involves the discretization of a second-order derivative, its treatment could be much more challenging than that of a first-order derivative, such as the pressure gradient. The present paper summarizes a series of improved methods for modeling the second-order viscosity force term. By using a benchmark patch test, the numerical accuracy and efficiency of different approaches are evaluated under both uniform and non-uniform particle configurations. Then these viscosity force models are used to compute a documented lid-driven cavity flow and its interaction with a cylinder, from which the most recommended viscosity term formulation has been identified
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