An unsteady axial symmetric 2-D (two-dimensional) flow of blood within a diseased, flexible-walled porous arterial segment is examined to determine its flow behavior. While the lumen with its blood clots fatty plaques and cholesterol signifies the porous substance, the walls of blood vessels simulate the irregular contractions. The governing equations are numerically solved using the MAC (Marker and Cell) approach with appropriate initial as well as boundary conditions. The SOR (Successive-Over-Relaxation) method is used to solve the poisson-pressure equation, and the process of discretization is carried out on a changing grid with an irregular grid size. Until a steady state is reached, the velocity and pressure adjustments are applied in cycles. It has been found that when permeability decreases, flow significantly slows down while pressure drop and WSS rise. In cases of severe stenosis, the recirculation and separation zones are located. When the porous medium's permeability decreases, flow separation and recirculation decrease. Numerical and published experimental results are compared. By bridging the gap between theoretical research and real-world clinical applications, numerical simulation enhances blood flow analysis, surgical planning, diagnostic precision, and validates sophisticated models.