Hydrodynamic flow patterns and behavior induced by bubble plumes in a linearly stratified fluid are studied. To optimize air-diffuser destratification systems especially for the combined effect of adjacent plumes of air-diffuser systems on mixing patterns in a stratified fluid, we developed a two phase (air-water) destratification model using Computational Fluid Dynamics (CFD) software as a new analytical process. Lab experiments were also carried out to verify CFD models in thermally stratified freshwater. From this, we could successfully explain some phenomena including hydrodynamic behaviors of bubble plumes and turbulent flow patterns in three-dimensions to the details which were not possible with the previous one-dimensional plume models. The CFD simulation and experimental results indicate that mixing patterns strongly depend on the spacing of neighboring plumes. As the spacing becomes less than 1.5 times the water depth, the combined effect gets stronger at an increasing rate. As the Plume Number (PN) increases, the rate of increase rises, and the combined effect is even stronger. These findings suggest that the combined effect should be more quantitatively taken into consideration for design and operation of an air-diffuser destratification system. Includes 17 references, tables, figures.