A fluid turbine apparatus which is able to increase the fluid velocity and consequently increase the rotation speed of the fluid turbine. The fluid turbine apparatus has a convergent section, a fluid turbine section and a divergent section. The fluid enters into the fluid turbine through the convergent section, passes through the fluid turbine and exits through the divergent section. The combination of the convergent section and the divergent section creates a Venturi effect and increases the fluid velocity and thus the energy density entering turbine for increasing the energy extracted by the turbine.