Numerical Investigation of Stenosis and Degree of Aneurysm on Haemodynamics of Blood Vessels Saleem K. Kadhim * , Sinan Abdul-Ghafar Ali Control and System Engineering Department, University of Technology-Iraq, Baghdad 10066, Iraq Corresponding Author Email: Saleem.K.Kadhim@uotechnology.edu.iq https://doi.org/10.18280/mmep.090330 ABSTRACT Received: 13 January 2022 Accepted: 22 April 2022 Computational fluid dynamics is a computer simulation technique used to study the effects of stenosis and aneurysm degree on haemodynamics in the blood vessels such as blood velocity, pressure, and wall shear stress. The current study employed the numerical simulations of pulsed blood flow using the Carreau non-Newtonian rheological and Newtonian models to model the wall shear stresses and haemodynamics in blood vessels. Furthermore, the model included three stenosis areas with different diameters, 70%, 80%, and 90%, and two aneurysm areas with different diameters, 15% and 44%. The study observed the blood velocity, pressure, and wall shear stresses at the damaged blood vessels areas. It was found that the maximum velocity was observed from stenosis when the stenosis ratio was increased to 90%. Additionally, the velocity increased up to 3.4 times, which led to increased blood shear stresses to up to 8.4 times, when the start acceleration flow and peck flow were compared. It is known that the degree of damage on blood vessels produces the most significant influence on local blood pressure and shear stresses. Therefore, it was concluded that stenosis at 90% may probably lead to serious lesions and effectively block the bloodstream by the ensuing thrombus. Keywords: stenosis, aneurysm, blood pressure, wall shear stress, damage vessels area 1. INTRODUCTION Currently, heart-related diseases are the leading causes of death around the world. Arterial diseases such as stenosis and aneurysm could affect the haemodynamics of the blood vessels. Intravascular atherosclerotic plaques cause stenosis of an artery. Intravascular atherosclerotic plaques form on vessel walls and extend into vessel lumens. Any obstructions in the arteries would change the blood flow considerably, with alterations in pressure and shear stress on the walls of the blood vessels reported as the most common [1]. An in-depth understanding of the blood flow in stenosed arteries is crucial to comprehend its characteristics better. However, not enough analyses were carried out to investigate the impact of different degrees and types of disease have on the distribution of shear stress and pressure along the length of a blood vessel. Moreover, a comparative analysis of the pathological effects of different degrees and types of damages of the blood vessels (stenosis and aneurysm) and blood flow turbulence on blood pressure showed that most of the studies were separate and fragmented [1, 2]. Generally, increased blood pressure is established when blood pressure is measured. However, determining the blood pressure of a damaged blood vessel at the damaged location is challenging since it is local blood pressure, and its value could differ from the total pressure. In addition, determining the pressure and blood vessel wall tensions concerning pathological size is almost impossible. Therefore, scientists employ modern and different methods to diagnose vascular diseases, including the ultrasonic double-scanning duplex method [3]. Furthermore, experimental diagnostic research necessitates the use of specialised technology. Pannier et al. [4] only used experimental blood pressure measurement for certain patients with specific pathologies. Biswas and Chakraborty [5] adopted the blood as a two-fluid model to examine the effects of body acceleration and slip velocity at the walls. Due to a wall slip, they discovered that the velocity and blood flow rate increased, but the effective viscosity decreased. Additionally, due to body acceleration, blood flow rates and velocity were significantly increased. In another study, a model based on a radially non-symmetric artery was created by Singh A.K. and Singh, D.P. [6]. They discovered that as the yield stress was increased and flux reduced, the resistance to blood flow approached unity. The resistance-to-flow ratio did not significantly change when the viscosities were varied. Additionally, yield stress displayed the most significant degree of change, while flux showed the smallest. Shukla et al. [7] investigated the blood flow dynamics of stenosed arteries using the non-Newtonian fluid flow. The results showed that as the stenosis ratio grew, the flow resistance and wall shear stress increased. However, due to the blood's non-Newtonian behaviour, the increases were minor, indicating its rheological characters were advantageous to the functioning of the damaged arterial circulation. The blood flow through a stenosed artery with a uniform cross-section was studied by Prakash et al. [8]. Blood flow rate, wall shear stress, and flow resistance against the stenosis size were calculated. The findings showed that stenosis increased the wall shear stress and flow resistance while decreasing the blood flow rate. Mallik et al. [9] investigated multiple stenosis effects with viscosity modifications through a power law fluid Mathematical Modelling of Engineering Problems Vol. 9, No. 3, June, 2022, pp. 811-818 Journal homepage: http://iieta.org/journals/mmep 811