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A fountain initially rises due to the momentum flux and eventually falls by the opposite buoyancy, which induces a two-layer structure for the fountain, an upflow and a returning counterflow surrounding that. The fountain has wide applications in building environment and industry in which the entrainment of fountain plays an important role. Therefore, a direct numerical simulation (DNS) is implemented to study the entrainment of a highly forced fountain at upflow-counterflow boundary and counterflow-environment boundary in quasi-steady state. The result shows the difference between the entrainment via mean flow and turbulence.