Viscous fluids are common materials as frequently seen in daily life, and simulating their characteristic behaviors has been required for various applications, such as video games and virtual reality. Regardless of recent advances, however, behaviors of simulated viscous fluids do not necessarily agree with the real-world counterparts. To fill the gap between simulated fluids and real ones, in this talk, I will present the two-way coupling method for viscous fluids and solid objects which has been neglected in spite of the importance. I also talk about a parameter identification framework which enables for automatic parameter tuning based on example videos to better approximate the real fluid flows.