The aim of this research is to develop cardiovascular (CV) fluid mechanics tools that can analyze and predict the vascular changes due to the growth and remodeling process (GR) during early embryonic cardiac development. Mechanical flow-induced loading, in addition to the genetic factors, is an essential regulator of the GR feedback process. Fluid-induced vascular network changes will be computed through transformative aims at the system level; that are coupled to the lower-level GR theories. The rich diversity of circulation systems found in nature inspired a novel reduced-order lumped parameter circulation model (LPM). For the first-time, LPM is integrated with multi-scale continuum mechanics vascular GR theories in order to establish a numerical feed-back loop between the GR response and instantaneous hemodynamic circuit parameters. A general network-based LPM model is proposed, again for the first time that covers the entire hydrodynamic network space where the numbers of vascular compartments, ventricles and their branching patterns evolve freely, but are subject to the cost functions founded on the biological optimality principles. Novel circuit similitude parameters that allow an unbiased energetic comparison will be developed. This framework will provide the global GR response of the entire circulation during development, energy/exergy budgets of complex congenital heart disease pathologies, and impact pediatric surgical treatments. At the organ level, The advanced boundary condition routines developed will transform the broader patient-specific CFD technology, which is currently used in clinical decision making. This project will have an impact on the pediatric and fetal cardiology, and CV surgery by giving researchers access to quantitative physiological information. Embryonic CV fluid dynamics is an emerging research field that challenges the human-centric bias and apathetic viewpoint of the static mature and healthy CV system at all educational levels.