Effect of turbulence modeling on realistic estimation of flow characteristics of liquid ejector pump

Ejector pumps are widely used in many industrial and engineering applications due to their simple constructions and ease of maintenance. The working fluid of ejector pump can be a gas or a liquid. When the ejectors are operated using incompressible fluids like liquids, they are often termed as Jet Pumps. One of the most important feature of these devices is that they provide the use of any ordinary centrifugal pump with a lower head but with a higher capacity, thus resulting into 2-3 folds increased mass flow rates. The realistic modeling of flow domain of ejector pump is necessary for its performance estimation and design improvements. Keeping in view the limitations and applicability of each turbulence model for specific genre of turbulent flows, the effect of RANS, modified RANS and LES modeling techniques is explored for correct estimation of flow characteristics of liquid ejector pump. In this research, the flow field of ejector pump, used in aircraft fuel system, is firstly simulated using Standard K-ε (RANS) model. The performance parameters obtained are then compared with experimental data which reveals the inadequacy of turbulence model in correct estimation of mass flow rates. For realistic modeling, the model constants are randomly tweaked to bring the simulated results closer to the experimental data. However, this methodology cannot be used for obtaining a priori simulation of subject pump. Therefore, LES is used to model the turbulent flow domain using WALE Sub Grid Scale model. The comparison of flow characteristics like turbulent eddy viscosity, Reynolds shear stresses and potential core estimation obtained from mentioned turbulence models is carried out to identify the reasons for erroneous results by Standard K-ε and to analyze the effect in turbulent flow characteristics by changing the model constants. This comparative data is overlapped with the results obtained from LES simulation to highlight the efficacy and advantages of later one in modeling the complex flow field of ejector pump.