The presence of ice hinders the operation of small hydropower plants in cold regions like Mongolia. In order to study this problem, we propose a numerical model for analyzing the liquid-solid phase changes that occur in a free surface flow. This model is formulated using the lattice Boltzmann method (LBM). The single phase free surface model, along with the immersed boundary condition, is used to model the free surface flow and solid phase. The thermal lattice Boltzmann (LB) equation is combined with a non-iterative enthalpy based formulation to simulate heat transport and phase changes. These models are integrated in a way that holds physical relation. The performance and accuracy of the model is validated using experimental evaluations. The formation of open water in the downstream channel of the hydropower plant is successfully simulated to demonstrate the performance of the model. Results indicate that the proposed model can be use d for studying measures to control downstream ice in hydropower plants. It can also be applied to study the ice phenomena in open channel flows.
This paper reports on the progress of the liquid-solid phase transition modeling of water in open channel flow by using the lattice Boltzmann method with the immersed boundary modification. The phase transition in a fluid flow has a moving interface between the liquid and solid state, which leads complicated treatments in existing numerical models. By applying the immersed boundary modification in the lattice Boltzmann method and the non-iterative enthalpy approach for the separation of the states, the moving boundary of the melting or solidification front is solved without any difficulty. The ice bed and the submerged ice cover under dynamic flow conditions is exercised to demonstrate the model performance. The model is extremely suitable in the formulation in terms of its simple and compact framework extendable to any dimensions.
Takeshi OTAKE, Ayuruzana BADARCH and Tokuzo HOSOYAMADA 1 学生会員 長岡技術科学大学大学院 工学研究科 建設工学専攻(〒940-2188 新潟県長岡市上富岡町1603-1) 2 非会員 工修 長岡技術科学大学大学院 工学研究科博士課程 エネルギー環境工学専攻 3 正会員 工博 長岡技術科学大学 環境社会基盤工学 教授 Estuaries of the large river discharge river waters and sediment to the sea. The discharged sediment is mainly the wash load, which is affected by density currents, tide, inertia forces of river discharge. Sediment which has repulsive force in pure water, lost electrical charge when it meets sea water and finally made flocculation caused by molecular attractive force. To understand distribution of the sediment in sea bottom, above mentioned phenomena should be included in numerical simulation algorithm for sediment transport model. In this study, a numerical algorithm for sediment particle transport under the effects of flocculation is originated. The algorithm is mainly based on the Lagrangian method. The performance of the numerical method is confirmed by the Lock-exchange flow in laboratory scale case. Application of the method to field scale calculation is conducted for the Okozu diversion channel in the Shinano River mouth. Settling of the sediment through the pycnocline is visualized with high resolution.
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