Drag model for two-dimensional string-type agglomerate of micro particles

To establish a practical method to predict the fluid force on wide variety of particle matters, we propose an efficient model for drag force on string-type agglomerates. The Reynolds number is assumed in the range of Stokes approximation. The immersed-boundary method of body force type developed by the authors is applied for modeling and evaluation of the model. First, model equations to represent drag on basic shapes of two or three spheres are modeled. Considering the characteristics of flow around a sphere at Stokes range, we use cosine formula for the modeling. Then, the model equations are extended to represent the string-type agglomerates of arbitrary numbers of spheres. By testing for the cases of 8 and 16 particles, it is confirmed that our model reasonably reproduces the drag forces obtained by the direct numerical simulation.