| dc.description.abstract | Natural materials such as muds, silts, clays, and soils are generally cohesive non-Newtonian fluids with complex rheological properties, which a Newtonian model cannot characterize precisely. This study adopts a three-dimensional model, Splash3D, which resolves the Navier-Stokes equations with PLIC-VOF surface-tracking algorithm. However, the original version of Splash3D is only available for Newtonian fluid prediction. One of the main contributions of this study is compiling a non-Newtonian fluid model into Splash3D model. This non-Newtonian fluid model is named Discontinuous Bi-viscous Model (DBM), which deals with the rheology feature of natural materials. This compiled model is used to study mudflow, landslide tsunami, and scouring problems.
DBM illustrates a discontinuity in the stress-strain relation of the mixture, which contains both solid and liquid phases (un-yield/plug and yield/liquefied phases). A yield strain rate is introduced as the indicator to identify the slip surface, which separates the un-yield and yield region. The new version of DBM can switch to the conventional Bingham model flexibly, where the yield strain rate equals zero. DBM includes four variables as yield stress, yield strain rate, plug zone viscosity, and liquefied zone viscosity, which a rheometer can measure. In addition, the internal source wave maker, which can deliver both regular and irregular waves, is also integrated into the model.
The coupling model is carefully validated with theoretical solutions and laboratory data, including the mudflows, wave generations, force calculation, and scour profiles. All of them get good agreements. This study provides three major applications and discussions of DBM. The first is the mudflow of the gypsum tailings dam in East Texas in 1966. The second is the submarine landslide tsunamis in which the volume of submarine material is treated as a rheological material. The third is the local scour around complex bridge piers caused by river floods and the scouring nearby a mono-pile wind turbine caused by ocean waves. The model is also employed to undertake some important projects in Taiwan. The results are acceptable compared with the survey data. Detailed discussions are presented in the contents. | en_US |