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- Andersson, Anders G., et al.
(författare)
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Effect of spatial resolution of rough surfaces on numerically computed flow fields with application to hydraulic engineering
- 2014
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Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Informa UK Limited. - 1994-2060 .- 1997-003X. ; 8:3, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- In numerical simulations of flow over rough surfaces, the roughness is often not resolved but represented by a numerical model. The validity of such an assumption is investigated in this paper by Reynolds-Averaged Navier-Stokes simulations of flow over a surface with a large roughness. The surface was created from a high-resolution laser scanning of a real rock blasted tunnel. By reducing the geometrical resolution of the roughness in two steps, the importance of an appropriate surface description could be examined. The flow fields obtained were compared to a set-up with a geometrical flat surface where the roughness was represented by a modified form of the Launder and Spalding wall-function. The flow field over the surface with the lowest resolution was substantially different from those of the two finer resolutions and rather close to the results from the set-up with the wall-function. The results also yield that the finer the resolution is the more vorticity is formed close to the rough surface and more turbulence is generated.
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| 5. |
- Jonsson, Patrick, et al.
(författare)
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Smoothed particle hydrodynamics modeling of hydraulic jumps
- 2011
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Ingår i: Particle-based Methods – Fundamentals and Applications. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788489925670 ; , s. 490-501
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study focus on Smoothed Particle Hydrodynamics (SPH) modeling of twodimensional hydraulic jumps in horizontal open channel flows. Insights to the complex dynamics of hydraulic jumps in a generalized test case serves as a knowledgebase for real world applications such as spillway channel flows in hydropower systems. In spillways, the strong energy dissipative mechanism associated with hydraulic jumps is a utilized feature to reduce negative effects of erosion to spillway channel banks and in the old river bed. The SPH-method with its mesh-free Lagrangian formulation and adaptive nature results in a method that handles extremely large deformations and numerous publications using the SPH-method for free-surface flow computations can be found in the literature. Hence, the main objectives with this work are to explore the SPH-methods capabilities to accurately capture the main features of a hydraulic jump and to investigate the influence of the number of particles that represent the system. The geometrical setup consists of an inlet which discharges to a horizontal plane with an attached weir close to the outlet. To investigate the influence of the number of particles that represents the system, three initial interparticle distances were studied, coarse, mid and fine. For all cases it is shown that the SPH-method accurately captures the main features of a hydraulic jump such as the transition between supercritical- and subcritical flow and the dynamics of the highly turbulent roller and the air entrapment process. The latter was captured even though a single phase was modeled only. Comparison of theoretically derived values and numerical results show good agreement for the coarse and mid cases. However, the fine case show oscillating tendencies which might be due to inherent numerical instabilities of the SPH-method or it might show a more physically correct solution. Further validation with experimental results is needed to clarify these issues.
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