REVISITING OF THE PRESSURE GRADIENT MODEL OF THE SPH METHOD FOR INCOMPRESSIBLE FLUIDS INCLUDING NEGATIVE PRESSURE

Abstract

In recent years, a number of bridges have been washed out due to torrential rains. When analyzing scour around piers, one of the causes of damage to bridges, using particle methods such as the SPH(Smoothed Particle Hydrodynamics) methods, the non-uniform distribution of particles and tensile instability caused by negative pressure occur. We especially focus on the pressure gradient model, which has been conventionally and frequently used for stable analysis, and discuss pressure gradient calculations suitable for negative pressure regions. Moreover we introduce a modified gradient model that satisfies first-order consistency as well as PS (Particle Shifting) scheme to maintain the particle distribution regularity. The modified SPH method reproduces von Karman vortex, and its validity is quantitatively examined by comparing the twin vortex size, drag coefficient, lift coefficient and Strouhal number with experimental data.