Abstract: By using two phase measuring technique of LDV, the suppression effects of sub millimeter particles to the water turbulence in mainstream zone of a horizontal pipe flow have been experimentally studied. This includes the investigation of the dependences of turbulence reduction on the parameters of particle size, flow development length, water flow Reynolds number, etc. According to the basic conditions that the appearance of vortex shedding phenomenon should be excluded and that the particles should respon...