Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification
Lead Research Organisation:
Cardiff University
Department Name: Sch of Engineering
Abstract
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Organisations
Publications
Stoesser T
(2015)
Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed
in Water
Mulahasan S
(2017)
Effect of Floodplain Obstructions on the Discharge Conveyance Capacity of Compound Channels
in Journal of Irrigation and Drainage Engineering
Mohajeri S
(2015)
The structure of gravel-bed flow with intermediate submergence: A laboratory study
in Water Resources Research
McSherry R
(2017)
Large eddy simulation of free-surface flows
in Journal of Hydrodynamics
Cevheri M
(2016)
A local mesh refinement approach for large-eddy simulations of turbulent flows
in International Journal for Numerical Methods in Fluids
| Description | We have developed a numerical code that enables simulations on locally refined meshes. We have further refined our research code to be able to predict accurately free surface deformations due to bed roughness. We have simulated flows over artificial rough beds (fractal roughness) and we have quantified the contributions of secondary currents, viscous stress, turbulent stress and form-induced stress to the overall flow resistance of the rough bed. It has been determined that the Reynolds number (Re) of the flow has a large influence on the contribution of each of the above mentioned constituents to the overall resistance. At low Re the viscous terms dominate and form induced stresses contribute very little. At high Re, the turbulent stresses dominate whilst the form induced stress contribution is not very significant. The presence of secondary current and their relatively high contribution to resistance is an unexpected discovery. The origin of these secondary currents is not 100% understood and this requires further investigation. |
| Exploitation Route | The outcomes of this funding can be used to develop further commercial CFD codes in the way friction losses are computed. These models can then be applied to predict more accurately stream and river flows. Also, the level set method can be used in commercial solvers to calculate the deformation of the water surface due to gravity waves or turbulence. |
| Sectors | Environment |
| Description | We have met with stakeholders and potential end users and have presented early results. In 2017 we held an end-users workshop at Arup in Leeds and had approximately 25 participants from industry and government agencies. |
| First Year Of Impact | 2015 |
| Sector | Environment,Financial Services, and Management Consultancy |
| Impact Types | Societal,Economic |
| Title | Hydro3D |
| Description | We have improved our CFD model Hydro3D |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2016 |
| Provided To Others? | Yes |
| Impact | This tool is now being used by other Universities including Tsinghua and Birmingham. |
| Title | hydro3D code availability |
| Description | hydro3D is a finite difference Navier Stokes solver that permits accurate and efficient Large Eddy Simulation (LES) of turbulent flows. It has been developed by Prof. Thorsten Stoesser and co-workers at Cardiff University, UK, primarily for use in the simulation of environmental fluid dynamics. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2016 |
| Provided To Others? | Yes |
| Impact | No notable impact yet. |
| URL | http://hydro3dproject.github.io/ |
| Description | Meetings with Stakeholders |
| Form Of Engagement Activity | A formal working group, expert panel or dialogue |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Professional Practitioners |
| Results and Impact | We had several meetings with stakeholders/policy makers and industry, including Natural Resources Wales, HR Wallingford, Arup and CH2M to present our research including some of the work undertaken in this project. |
| Year(s) Of Engagement Activity | 2015,2016 |