Large Eddy Simulation of Internal Flow of a Mixed-Flow Pump

Large eddy simulation (LES) of internal flows of a mixed-flow pump is performed. The pump has 5 open impeller blades and twelve diffuser vanes. The objective of the present research is to verify the accuracy of the pump performance prediction by LES with a particular emphasis placed on the instability characteristics. The following two cases of computations are preformed for LES with different grid resolutions. In the first case, we perform LES of internal flow of the pump for a wide range of flow rate, including a flow rate from the shutoff point to the maximum flow. Secondly, we focus on internal flows at flow rates of 55%∼60%, where the instability characteristics take place, with finer computational grid compared to the first case. We use 8 million girds for the first case (the coarse LES), and 78 million girds for the second case (the fine LES). We intended to resolve the turbulent boundary layer (TBL) developed on the surfaces of impeller blades and diffuser vanes in the fine LES. We obtained a good agreement between the measured and predicted pump performance for a wide range of flow rate in the coarse LES, although the predicted total head drop at the flow rate of 55%∼60% is smaller than the measured one. In the fine LES, accuracy of pump performance prediction at 55%∼60% flow rate was improved.