A Critical Review of Multiphase Modelling of Blood Flow in Human Cardiovascular System

In the human body, blood acts as a transporter of oxygen and other nutrients as well as carbon dioxide and other waste materials to and from all the organs. Therefore, continuous supply of blood to all the organs is critical for proper functioning of the human body. Blood is a complex fluid and has more than 40% flexible particles which include red blood cells, white blood cells, platelets and other proteins suspended in a water-like fluid, plasma. The dynamics of blood flow, known as haemodynamics, is critical in the development, diagnosis and treatment planning of vascular diseases and design and development of cardiovascular devices. Whilst the most advanced flow measurement techniques such as X-ray imaging, magnetic resonance imaging and ultrasound imaging are used in the diagnosis and treatment of vascular diseases, it is not possible to obtain the complete information of pressure and velocity field experimentally via in vivo methods. Therefore, in silico methods or computational modelling techniques are being increasingly employed not only to understand the haemodynamics but also for use in the clinical setting. Whilst blood is treated as a homogeneous, single-phase fluid in several studies, it is possible to capture several features of the flow of blood only by modelling it as a multiphase fluid. A number of approaches have been adopted to model multiphase flow of blood. A broad categorisation can be based on whether the cell boundary is captured explicitly, e.g. immersed boundary method, or the phases are treated as interpenetrating and two or more phases can exist simultaneously at a point, e.g. Euler–Euler method. In the literature, both the approaches have been adopted to model the flow of blood. Particle-based methods, such as smoothed particle hydrodynamics and dissipative particle dynamics have also been employed by researchers to study the complex interactions associated with the flow of blood. In this article, we discuss different multiphase modelling approaches and their application in the haemodynamics modelling.