- Vortical structures are the driving mechanism of transition to turbulence in porous media requiring adequately resolved observations along with analysis of the scale and energy of ﬂow within the pores. Of speciﬁc interest is to understand the vortex dynamics, energy, and turbulent mixing and transport properties in the scale of each pore and overall throughout the entire permeable media by enhancing the inertial effects with Reynolds number. Transition to turbulence, a general problem in porous media ﬂows, is inﬂuenced by random tortuous geometry generating complex ﬂow structures. In spite of many contributions in laminar cases, the vortical physics behind cases exceeding the steady laminar ﬂow has not been well investigated. Major questions are categorized as follows: (a) how does the global (macro-scale) mean velocity inﬂuence the local (pore-scale) vortical ﬂow structures,(b) what are the dominant mechanisms for energy growth emanated from swirling motions as opposed to turbulent kinetic energy, and (c) how does the inertial effects of vortical structures enhance the ﬂow mixing and transport in randomly packed porous media. Investigating the proposed problems, we implement high ﬁdelity velocimetry experiments: (1) to estimate the scale of vortical ﬂow structures in terms of size, time, and number density that are major contributors in transition regime locally in each pore and their impact on global vortical ﬂow statistics within a randomly packed porous system, (2) to scrutinize the evolution of ﬂow kinetic energy with Reynolds number in the entire bed that appears to affect differently in the local pore-scale ﬂow; i.e. some pores are affected by the energetic ﬂow structures, while some pores experience lower impact from the global mean ﬂow inertia; hence the effect on production and dissipation of energy, and (3) to investigate the trans-port and mixing characteristics of ﬂow such as dispersion and tortuosity during the transition regime. In this work, two-component Time-Resolved Particle Image Velocimetry (TR-PIV) technique is employed to visualize the ﬂow. Capturing velocity ﬁeld, and measuring the ﬂow structures as well as the turbulent characteristics in Reynolds numbers ranging from 100 to 1000 within a mono-dispersed randomly packed bed of hollow glass spheres is proposed. The approach for data analysis is based on (1) local and non-local vortex identiﬁcation, (2) conventional Eulerian turbulence statistics (turbulent kinetic energy budget), proper orthogonal decomposition, and dynamic mode decomposition, and (3) Lagrangian velocity variances from Eulerian mean velocities, tortuosity, and dispersion modeling. In each case, results are presented accordingly to demonstrate the overall mixing in porous media. Finally, a road map is provided on the pore- versus macro-scale effects on the energy of ﬂow and swirl structures, turbulence production and dissipation, as well as dispersion, and their contribution in interpreting the overall ﬂow mixing. Also, it is demonstrated that the shear and rotational contribution of vortical structures are inﬂuenced differently from pore- versus macro-scale Reynolds numbers which interprets the scale evolution during transition process. Finally, the effect of the vortex dynamics and ﬂow structure in randomly packed bed sphered by investigating scale, energy, and mixing characteristics.