Velocity distributions of solid particles in liquid-solid fluidized beds were obtained experimentally by the use of the four video pictures with appropriate time interval. First, each pairs of pictures with an appropriate successive time interval were compared in order to identify the trajectories of all particles then the locations of all the particles in the fourth picture were compared with those in the first picture in order to determine the velocities of all the particles. Based on this method the velocity distributions of particles were investigated for three types of flow rate and two types of particle numbers. It was clarified that in the case of small number of particles the velocity distributions for the horizontal direction was approximated as symmetric exponential distribution functions and those for vertical direction was asymmetric exponential distribution functions. It was found that the larger the flow rate is, the smaller the exponent becomes and in the case of vertical directions the exponents for the upward velocities are smaller than those for downwards ones. Furthermore, it was clarified that in the case of large number of particles Gaussian distribution function and t-distribution function are also obtained

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