Two 45min keynote lectures will be given at the beginning of the first and the second day of the workshop. The keynote lectures of the workshop will be given by
College of Engineering, Peking University, Beijing
Title: SPH coupling with EBG for modeling fluid-flexible structure interactions
Abstract: In this paper, a coupling method of smoothed particle hydrodynamics (SPH) and element bending group (EBG) is developed for modeling the interaction of viscous fluid with flexible structures with large deformation. SPH particles are used to model the viscous fluid flow governed by Navier-Stokes equations, and EBG particles are used to model the dynamic movement and deformation of flexible objects (such as fibers). The interaction of the neighboring fluid (SPH) and solid (EBG) particles renders the interaction of fluid and flexible structure. The SPH-EBG coupling approach is first used to model dam break flows impacting on flexible plates. The good agreement of presented numerical results with existing experimental and numerical demonstrates the effectiveness of the SPH and EBG coupling approach in modeling fluid-flexible structure interactions. The SPH-EBG coupling approach is then applied to model the interaction of viscous fluid with a flexible fiber fixed at the middle point. In numerical simulation, flexible fibers of different lengths are immersed in a moving viscous fluid driven by a body force. The drag force on the fiber obtained from SPH-EBG simulation agrees well with experimental observations. It is shown that the flexible fiber demonstrates three typical bending modes, including the U-shaped mode, the flapping mode, and the closed mode, and that the flexible fiber experiences a drag reduction due to its reconfiguration by bending. It is also found that the U4/3 drag scaling law for a flexible fiber is only valid for the U-shaped mode, but not valid for the flapping and closed modes. The results indicate that the reconfiguration of a flexible fiber is caused by the fluid force acting on it, while vortex shedding is of importance in the translations of bending modes. It is also shown that there exists a transition criterion for the flexible fiber from the swing mode to the flapping mode. Two non-dimensional parameters for characterizing a fiber-fluid interaction system are given and these two parameters are inherently related to each other.
Institute of Complex Systems (ICS), Forschungszentrum Jülich (FZJ), Germany
Title: Smoothed dissipative particle dynamics or SPH at mesoscale: theory and applications
Abstract: Smoothed dissipative particle dynamics (SDPD) combines two popular techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved DPD approach. Advantages of the SDPD method over conventional DPD include the possibility of using an arbitrary equation of state, direct input of transport properties, and a well-defined physical scale of discretized elements or fluid particles. Another advantage of the SDPD method is that it can be directly embedded into the GENERIC framework providing thermodynamic consistency and satisfaction of the fluctuation-dissipation theorem. The SDPD method has been already applied to a number of mesoscopic problems involving complex fluids.
In this talk, the theoretical basis of SDPD will be reviewed and a number of applications of the method will be discussed. In particular, we will illustrate the application of SDPD to study membrane fluctuations of biological cells. Furthermore, we will discuss the problem of micro- and nano-particle margination (i.e., particle migration toward the walls) in blood flow, which is a crucial step in drug delivery, and show how simulations help to elucidate the physical mechanisms which govern migration of micro- and nano-carriers toward the walls in micro-vessels. Finally, we will present the flow behavior of blood cells in a microfluidic device which offers great opportunities for cell sorting.