In this study, the effects of the dense vertical internals on the liquid velocity field and turbulence parameters (Reynolds stresses, turbulent kinetic energy, and turbulent eddy diffusivities) are experimentally investigated for the first time by using advanced Radioactive Particle Tracking (RPT) technique. The experimental work was carried out in a Plexiglas bubble column with 5.5 in. (0.14 m) and a height of 72 in. (1.83 m) for the air-water system. In this work, thirty vertical Plexiglass internals of 0.5 in. (0.0127 m) outer diameter were used which covered similar to 25% (typical for Fischer-Tropsch processes) of the total cross-sectional area of the column where they arranged as the triangular pitch of 0.84 in. (0.0214 m). The superficial gas velocities based on both total cross-sectional area and free cross-sectional area available for the flow were utilized (0.08, 0.2, and 0.45 m/s), which covered the transition and churn-turbulent flow regime to meet the industrial applications of FT synthesis. The experimental data show that the presence of the internals at a given superficial gas velocity causes an increase in the axial centerline liquid velocity and a sharp decrease in turbulence parameters while the increase in superficial gas velocity in the presence of internals causes an increase in axial centerline liquid velocity and turbulent parameters. The obtained data are reliable as a benchmark data for validation computational fluid dynamics (CFD) simulation, and models. (C) 2016 Elsevier Ltd. All rights reserved.