“…The forces that direct the blood flow are gravity and pressure gradient force, while the hindering forces are shear forces resulting from viscosity and turbulence [5,7]. The wall thickness to vessel radius (diameter) ratio due to arteries, are considered flat incompressible, thick viscoelastic [5,8,9] or elastic tubes [10], as well as thin elastic [5,[11][12][13] or viscoelastic tubes [5,14,15]. Therefore, these features show obvious nonlinearity.…”