Vertebrate cardiogenesis is believed to be partially regulated by fluid forces imposed by blood flow in addition to myocardial activity and other epigenetic factors. To understand the flow field within the embryonic heart, numerical simulations using the immersed boundary method were performed on a series of models that represent simplified versions of some of the early morphological stages of heart development. The results of the numerical study were validated using flow visualization experiments conducted on equivalent dynamically scaled physical models. The chamber and cardiac cushion (or valve) depths in the models were varied, and Reynolds numbers ranging from 0.01 to 1000 corresponding to the scale of the early heart tube to the adult heart were considered. The observed results showed that vortex formation within the chambers occurred for Reynolds numbers on the order of 1-10. This transition to vertical flow appears to be highly sensitive to the chamber and cushion depths within the model. These fluid dynamic events could be important to induce shear sensing at the endothelial surface layer which is thought to be a part of regulating the proper morphological development and functionality of the valves.