Parallel modeling of cell suspension flow in complex micro-networks with inflow/outflow boundary conditions

Abstract We proposed a parallel framework with inflow/outflow boundary conditions for particle-based simulations of cell suspension flow through complex micro-networks that is often encountered in microcirculation and microfluidic devices. The behaviors of fluid and cells are modeled by a hybrid approach of smoothed dissipative particle dynamics (SDPD) and immersed boundary method (IBM). The simulation system is associated with two more domains, the inflow domain at the inlets and the outflow domains at the outlets, to implement the inflow/outflow boundary conditions. The inflow is duplicated into the system from a fully-developed flow generated in the inflow domain under a periodic boundary condition. The outflow is iteratively controlled by two adaptive forces to maintain mass and momentum conservation, and meanwhile, the fluid and cells leaving the outlets are removed from the system. A master-slave parallel configuration is constructed, where the master thread is responsible for dividing the simulation domain or allocating the simulation tasks to three types of slave threads, cell, inflow and hybrid slave threads. To save message communication, each cell is assigned to a separate thread by task decomposition, while the inflow/hybrid slave threads are divided by domain decomposition. Four validation studies were carried out for the fluid flows in a straight and a bifurcated tubes, the deformation of a capsule in a straight tube, as well as the rheology of many red blood cells (RBCs) in a straight tube. The results were compared with their corresponding analytical solutions or previously-published numerical results, and good agreements were observed on the velocity field, cell deformation, and rheological behaviors of cells. Moreover, two numerical experiments were conducted to demonstrate the capability of the proposed methodology. One is RBCs through a microvascular network with an inlet but four outlets, and the other is those through a serpentine microfluidic chip with several complex geometric features, including bifurcations, sharp corners, sudden expansion and multiple outlets. Both of these experiments not only demonstrated the capability of the new methodology, but also suggested a potential to simulate real-world biomedical problems, such as thrombus formation, tumor metastasis, drug delivery, and so on.