The drag force acting on a system of densely packed particles is a common issue encountered during the fluidization of particles. In this process, the bulk motion is induced by the drag action of fluid flow. The discrete element method based on the Euler-Lagrange description can provide a realistic estimation of particle-fluid and particle-particle interactions; however, it is not possible to simulate the flow phenomena in a space smaller than a particle size by using this method. However, the study of flow on such a scale is crucial for the drag force analysis. Therefore, in the present study, the immersed boundary method, which is a direct numerical simulation, is used to investigate the drag force by simulating the flow around each particle. In this simulation, particles were positioned according to different types of spatial arrangements in order to represent the different degrees of voidage, and the flow around these particles.