Study of Turbulence Model for Performance and Flow Field Prediction of Pico Hydro Types Propeller Turbine

Abstract

The computational fluid dynamics (CFD) method is a method often used in predicting

the performance and flow field of turbine because it is cheap and fast. The accuracy of

CFD method is influenced by several aspects: boundary conditions, discretization of

space and time method, and the use of turbulence models. For turbulence model,

there is no clarity of the most accurate model, especially in the pico hydro type

propeller. Therefore, this study compared three turbulent models based on Reynolds

Average Navier-Stokes (RANS) two equations to predicts the performance of a pico

hydro propeller turbine: standard k-ε, Group Normalization (RNG) k-ε, and Shear Stress

Transport (SST) k- ω. This study used a three-dimensional simulation method,

transient, and six-degree of freedom features. The Grid Convergency index (GCI) and

Time-step Independence Index (TCI) were used to verify the simulation results. From

the results, the CFD results were similar to the experiment results (valid). Furthermore,

there was different prediction of performance due to differences in the turbulence

model but not too high. Based on this, for prediction of performance pico hydro

propeller turbine, the standard k-ε turbulence model was recommended for use.

However, for study flow field, RNG k-ε and SST k-ω were recommended because they

were not over-predicted in the dissipation rate calculation.