A dual-scale turbulence model is applied to simulate cocurrent upward gas-liquid bubbly flows and validated with available experimental data. In the model

liquid phase turbulence is split into shear-induced and bubbleinduced turbulence. Single-phase standard k-ε model is used to compute shear-induced turbulence and another transport equation is added to model bubble-induced turbulence. In the latter transport equation

energy loss due to interface drag is the production term

and the characteristic length of bubble-induced turbulence

simply the bubble diameter in this work

is introduced to model the dissipation term. The simulated results agree well with experimental data of the test cases and it is demonstrated that the proposed dual-scale turbulence model outperforms other models. Analysis of the predicted turbulence shows that themain part of turbulent kinetic energy is the bubble-induced one while the shear-induced turbulent viscosity predominates within turbulent viscosity

especially at the pipe center. The underlying reason is the apparently different scales for the two kinds of turbulence production mechanisms: the shear-induced turbulence is on the scale of the whole pipe while the bubble-induced turbulence is on the scale of bubble diameter. Therefore

the model reflects the multi-scale phenomenon involved in gas-liquid bubbly flows.