| 1. |
- Andersson, Anders G., et al.
(författare)
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CFD-modelling and validation of free surface flow during spilling of reservoir in down-scale model
- 2013
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Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Informa UK Limited. - 1994-2060 .- 1997-003X. ; 7:1, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Fully three dimensional modelling of the spilling from a reservoir with relatively complex geometry were performed and compared to experimental results from a physical scale model with the aim to advance the science of numerical modelling of free surface flow of real reservoirs. In the set-up in focus the water was spilled from the reservoir through three gates that could be manoeuvred separately. In the first case two of the gates were closed and the third gate was partly opened. In this experimental set-up the water surface in the reservoir was close to horizontal. Therefore it was here meaningful to compare a rigid lid modelling approximation to the more computational heavy method of Volume of Fluids. In the second case, all three gates were open, resulting in a nonhorizontal varied flow surface profile in the reservoir upstream critical sections at the spillway crests. This case was simulated with Volume of Fluids and the position of the air-water interface was derived for two turbulence models, the standard k-ε and SSG. Water levels, velocities and the shape of the water surface were compared to experiments. The simulation results capture qualitative features such as a vortex near the outlet and show good quantitative agreement with the experiments regardless of method used to simulate the free surface. In general, simulations with the standard k-ε and the more advanced SSG turbulence models give the same results with respect to the averaged quantities measured.
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| 2. |
- 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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| 3. |
- Liu, Ting, et al.
(författare)
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Three-Dimensional Computations Of Water-Air Flow In A Bottom Spillway During Gate Opening
- 2014
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Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Taylor & Francis. - 1994-2060 .- 1997-003X. ; 8:1, s. 104-115
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Tidskriftsartikel (refereegranskat)abstract
- Undesired entrainment of air in a bottom spillway often leads to problems in both safety and operational functions. A numerical analysis of a transient process of air entrainment into bottom spillway flows when a spillway gate is opened was conducted in this study. The Volume of Fluid (VOF) model was used. The 3D computational domain consisted of a spillway conduit, a moving bulkhead gate, a gate shaft, an upstream reservoir and a downstream outlet. The large number of cells, together with the dynamic mesh modelling of the moving gate, required substantial computational resources, which necessitated parallel computing on a mainframe computer. The simulations captured the changes in the flow patterns and predicted the amount of air entrainment in the gate shaft and the detrainment downstream, which help in the understanding of the system behaviour during opening of the spillway gate. The initial conduit water level and the gate opening procedure affect the degree of air entrainment in the gate shaft. To release the undesired air, a de-aeration chamber with a tube leading to the atmosphere was added to the conduit. Despite the incomplete air release, the de-aeration chamber was found to be effective in reducing water surface fluctuations in the downstream outlet.
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| 4. |
- Westerberg, Lars-Göran, et al.
(författare)
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Burner backflow reduction in regeneration furnace
- 2011
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Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Informa UK Limited. - 1994-2060 .- 1997-003X. ; 5:3, s. 372-383
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Tidskriftsartikel (refereegranskat)abstract
- In the present case from the steel industry, waste hydrochloric acid from the pickling process is regenerated using spray roasting. The process is driven by four burners placed symmetrically along the periphery of the cylindrical main section of the reactor. Severe problems with gas backflow and sintering of iron oxide inside the burner chamber have led to a complete shut down of the process 1-2 times every week, which is a frequency which significantly affects the productivity. In this study the influence of a kick-out on the gas flow in the vicinity of the burner chamber is investigated numerically. It is shown that the kick-out geometry creates a vortical low pressure region preventing the inflow of gas and hence the sintering of iron oxide. This has led to a significant increase in the productivity with no additional shut-downs than needed for the ordinary maintenance every 6-8 weeks.
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| 5. |
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