Flow behavior through t- and y-junctionsin a model blood vessel

Abstract

Atherosclerosis isa very common cardiovascular disease that is responsible for most of the death every year. Atherosclerosis is the disease that is caused by the thickening of the blood vessel wall and by the blockage of the blood flow due to the formation of fatty plaque consisting of LDL cholesterol, toxins, calcium, dead blood cells, and so on. Several hemodynamic factors like flow recirculation, vortices, flow stagnation are responsible for the formation of plaque and thrombus or blood clot due to particle accumulation in localized blood vessel sites. In order to look for the better treatment in the atherosclerosis disease, it is essential to investigate the potential zones of blood flow disturbance in the cardiovascular network. The present study investigates the flow behaviour around T- and Y-junctions in blood vessel which correspond to the external iliac vein (EIV) and internal iliac vein (IIV) junctions. Both the experimental and computational techniques have been applied in order to observing the flow disturbance in the T- and Y-shaped venous junctions. For the simplicity in design and to get a basic understanding of flow behaviour, a square (10 mm × 10 mm) model of T-junction has been developed. Experiments have been carried out using dye flow visualization and unsteady pressure measurement. Water has been used as the working fluid.Pulsatile flow corresponding to 75 beats per minute (bpm) has been utilized using two computer program-controlled gear pumps at the two inlets of the junction. Unit flow ratio has been used to employ the external iliac vein (EIV) flow at the two inlets. Corresponding to the internal iliac vein (IIV)flow in one inlet channel, flow ratio of 3/2 has been used as well. Beside experiments, a computational approach based on finite volume method has been employed to simulate the flow in T- and Y-junctions. The computational results have been validated with experimental measurement. Both the experimental and computational analyses indicate large flow disturbance associated with intensive flow recirculation, vortex formation, and flow separation in both the downstream and upstream regions. Single and double ring-shaped and eye-shaped vortices has been observed in the flow field analysis. The deviation in pressure waveform fluctuation indicates intense flow disturbance in the downstream locations. The flow disturbance is found to be more severe in case of T-junction than in Y-junction. However, the intensity of flow disturbance becomes weaker in case of higher flow ratio compared to unit ratio. These flow recirculation zones comprehensively indicates the potential sites of particle accumulation in the venous junction that may cause subsequent plaque and thrombus formation. Nomenclature