An explicit algebraic Reynolds stress model (EARSM) proposed by Wallin & Johansson was extended to simulate anisotropic buoyant turbulent flows. The collocated finite volume method was applied to solve the Navier-Stokes equations and the pressure coupling was treated in the SIMPLEC algorithm. A turbulent thermal mixing in T-junction flows was simulated to validate the model, A comparison with experiments and Fukushima et al's DNS results shows that the present model captures the characteristics of anisotropic buoyant turbulent flows. Meanwhile, the computation shows excellent numerical stability and the computation cost is only slightly higher than that of the eddy-viscosity turbulence model.