In process industries, the study of granular mixing can substantially optimize energy costs and the quality of final products. In this work, we study the mixing of binary granular systems assisted by fluid flow through the assembly. The granular system is exposed to continuous fluid flow from the bottom to the top. Particle mixing is simulated by the coupling of Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). Parameters like particle stacking order, density ratio, and size ratio show a significant influence on mixing. The presence of tilted plates as a geometric intervention with different configurations plays a critical role in mixing efficiency. A new mixing index which captures the nature of contact creation, and the degree of mixing is proposed. The present work helps develop efficient strategies for particle mixing in fluidized beds. © 2021 Elsevier B.V.