The experimental projected angular distributions of black fragments produced in siliconemulsion collisions at 4.5A GeV/c (the Dubna momentum) are reported in detail. An obvious dependence of the projected angular distribution on polar angle is observed. We introduce the reaction plane flows using the momentum components in the reaction plane. Directed reaction plane flow and elliptic reaction plane flow are observed. A multisource ideal gas model which contains an expansion and a movement of the source is used to describe the experimental results and to extract the flow characteristics. The results of a Monte Carlo calculation are in good agreement with the experimental data.