The purpose of this research is to study numerically the turbulent gas-particle two-phase flow characteristics using the Eulerian-Eulerian method. A computer code is developed for the numerical study by using the k - ${varepsilon}$ - $k_p$ two-phase turbulent model. The developed code is applied for particle-laden flows in which the particle volume traction is between $10^{-5}$ and $10^{-2}$ for the Stokes numbers smaller than unity. The gas and particle velocities and the particle volume traction obtained by using this code are in good agreement with those obtained by a commercial code for the gas-particle jet flows within a rectangular enclosure. The gas-particle jet injected into a vertical rectangular 3D enclosure is numerically modeled to study the effect of the Stokes number, the particle volume traction and the particle Reynolds numbers. The numerical results show that the Stokes number and the particle volume traction are important parameters in turbulent gas-particle flows. A small Stokes number (St ${leq}$ 0.07) implies that the particles are nearly at the velocity equilibrium with the gas phase, while a large Stokes number (St ${geq}$ 0.07) implies that the slip velocity between the gas and particle phase increases and the particle velocity is less affected by the gas phase. A large particle volume fraction (${alpha}_p;{geq};0.0001$) implies that the effect of the particles on the gas phase momentum increases, while a small particle volume traction (${alpha}_p;{leq};0.0001$) implies that the particles would have no or small effect on the gas flow field. For fixed Stokes number and particle volume traction, an increase of the particle Reynolds number results in a decrease of the slip velocity between the gas and particle velocities.