Keywords

Large Woody Debris; 3D LWD Model; Computational Fluid Dynamics

Location

Session H6: Environmental Fluid Mechanics - Theoretical, Modeling and Experimental Approaches

Start Date

17-6-2014 3:40 PM

End Date

17-6-2014 5:20 PM

Description

Large Wood (LW) has been widely used in stream and watershed restoration projects due to the many ecological benefits it offers. Its use in streams, however, has unresolved challenges with regard to its impact on stream morphology, safety and lack of design guidelines. Laboratory or field study of LW is difficult due to irregular nature of LW structures. Computational fluid dynamics (CFO) modelling, therefore, becomes an attractive alternative. However, CFO modelling of LW has its own challenges: the difficulty of mesh representation and lack of reliable and practical 3O flow and mobile-bed models. In this paper, an LW research and development program at the U.S. Bureau of Reclamation is described in which a combined field and CFO modelling approach is used to understand the flow field around LW and the morphological changes induced by LW. A field study program is first described that will assist the verification of the CFO model. The computational strategy is then outlined. The latest scanner is used to obtain LW geometry in addition to stream bathymetry and topography. The geometry is processed so that surfaces are represented by the stereolithography (STL) file. The STL surfaces are then used to generate a suitable 3O mesh in an automated manner. Finally, we describe an integrated 3O flow and mobile-bed CFO model that adopts the 3O mesh as input and performs the computational modelling. A sample case is used to demonstrate the above processes.

 
Jun 17th, 3:40 PM Jun 17th, 5:20 PM

Large Wood Flow Hydraulics: A 3D Modelling Approach

Session H6: Environmental Fluid Mechanics - Theoretical, Modeling and Experimental Approaches

Large Wood (LW) has been widely used in stream and watershed restoration projects due to the many ecological benefits it offers. Its use in streams, however, has unresolved challenges with regard to its impact on stream morphology, safety and lack of design guidelines. Laboratory or field study of LW is difficult due to irregular nature of LW structures. Computational fluid dynamics (CFO) modelling, therefore, becomes an attractive alternative. However, CFO modelling of LW has its own challenges: the difficulty of mesh representation and lack of reliable and practical 3O flow and mobile-bed models. In this paper, an LW research and development program at the U.S. Bureau of Reclamation is described in which a combined field and CFO modelling approach is used to understand the flow field around LW and the morphological changes induced by LW. A field study program is first described that will assist the verification of the CFO model. The computational strategy is then outlined. The latest scanner is used to obtain LW geometry in addition to stream bathymetry and topography. The geometry is processed so that surfaces are represented by the stereolithography (STL) file. The STL surfaces are then used to generate a suitable 3O mesh in an automated manner. Finally, we describe an integrated 3O flow and mobile-bed CFO model that adopts the 3O mesh as input and performs the computational modelling. A sample case is used to demonstrate the above processes.