Study on the Self-Sustaining Inlet Boundary Conditions for Numerical Simulation on Local Scour

Abstract

In previous numerical simulations of local scour, the steady flow is normally adopted as the inlet boundary condition, and the approach flow is always assumed as a homogeneous isotropic turbulence. In the present study, the results turn out to be different from such previous cases, even without obstructions. Under conventional methods, the approach flow decays along the streamwise in the computational domain. Meanwhile, in order to ensure the simulation effect for some major projects such as the local scour around bridge piers and submarine pipelines, appropriate inlet boundary conditions and its self-sustaining character become some of the important factors. Therefore, in the present study, a novel self-sustaining model with the standard k-ɛ turbulence model is proposed to quickly obtain a homogeneous isotropic turbulence. The model parameters are discussed in the light of flume experiment data by sensitivity analysis. To verify the applicability of the proposed model and inlet boundary conditions, numerical simulations in an empty domain are also performed. It is shown that the novel self-sustaining model and corresponding inlet boundary can produce a homogeneous isotropic turbulence, which will help to guarantee fine numerical simulations for scour prediction with prescribed flow conditions.