The source term can be incorporated in LBM as external force, as discussed before. The beauty of LBM in treating multi-phase flows is that there is no need to trace the interface between phase as in the case in NS. Hence, coding of multi-phase is much easier in LBM than in NS solver. In this book, we avoided to discuss this kind of problems for one simple reason. The method is relatively simple to imply but the reader needs background on the physics of the problem, before applying the LBM. Therefore, the complex flow is left to the readers interest. However, I am sure that the reader can easily extend the pervious codes to handle complex phenomena easily provided that the reader understand the underlying physics of the problem.