Effect of Non-newtonian Behaviour on Fluid Structural Interaction for Flow Through a Model Stenosed Artery

AbstractThe cause and development of many cardiovascular diseases are related to the nature of blood flow and the mechanical behaviour of the blood vessel. Moreover, the plaque (stenosis) rapture can be occurred as a result of interaction between the blood and plaque, leading to the clot formation and stroke. In the present study, the interaction of blood flow with plaque (stenosis) was numerically modelled. A pulsatile flow was used to mimic the real blood flow through the artery. The rheological properties of blood are considered as Newtonian as well as non-Newtonian. Fibrous cap thickness was varied from 0.1mm to 2.0mm. Many vortex rings are appeared at the pre- and post-stenotic region in the Newtonian model than in the non-Newtonian model. Deformation of stenosis, wall shear stress (WSS) and vomises stress all are found high in non-Newtonian model for the fibrous cap thicknesses studied here. Moreover, in Newtonian model, the vonmises stress was found to be 6500 pa for the case of 50% stenosis with 0.1mm fibrous cap thickness on the other hand it was around 10500 pa in case of non-Newtonian model

Numerical Simulation of Sinusoidal Fluctuated Pulsatile Laminar Flow Through Stenotic Artery

A numerical investigation is carried out for laminar sinusoidal pulsating flow through a modeled arterial stenosis with a trapezoidal profile up to peak Reynolds number of 1000. Finite element based numerical technique is used to solve the fluid flow governing equations where the fluid is assumed to be viscous, incompressible and Newtonian. The effects of pulsation, stenosis severity, Reynolds number and Womersley number on the flow behavior are studied. The dynamic nature of pulsating flow disturbs the radial velocity distribution and thus generates recirculation zone in the poststenotic region. The peak wall shear stress develops for 65% stenosis (by area) is 3, 2.2, and 1.3 times higher than that for 30%, 45%, and 55% stenosis, respectively. Peak wall shear stress and wall vorticity appear to intense at the throat of the stenosis. It is also observed that the peak wall vorticity seems to increase with the increase of stenosis size and Reynolds number. However, the peak values of instantaneous wall vorticity are not greatly affected by the variation of Womersley number

Characteristics of transonic moist air flows around butterfly valves with spontaneous condensation

Effects of spontaneous condensation of moist air on the shock wave dynamics around butterfly valves in transonic flows are investigated by experimental and numerical simulations. Two symmetric valve disk shapes namely- a flat rectangular plate and a mid-plane cross-section of a prototype butterfly valve have been studied in the present research. Results showed that in case with spontaneous condensation, the root mean square of pressure oscillation (induced by shock dynamics) is reduced significantly with those without condensation for both shapes of the valves. Moreover, local aerodynamic moments were reduced in case with condensation which is considered to be beneficial in torque requirement in case of on/off applications of valves as flow control devices. However, total pressure loss was increased with spontaneous condensation in both the valves. Furthermore, the disk shape of a prototype butterfly valve showed better aerodynamic performances compared to flat rectangular plate profile in respect of total pressure loss and vortex shedding frequency in the wake region

Numerical Analysis of Bypass Mass Injection on Thrust Vectoring of Supersonic Nozzle

High speed aerospace applications require rapid control of thrust (i.e. thrust vectoring) in order to achieve better manoeuvrability. Among the existing technologies, shock vector control is one of the efficient ways to achieve thrust vectoring. In the present study, bypass mass injection (passive control) was used to generate shock vectoring in a planar supersonic Converging-Diverging (CD) nozzle. Two diffenrent bypass lines were used to inject mass in the diverging section varying their dimension in the span wise direction (10 mm ×10 mm2 square channel and 2.68 mm×38 mm2 rectangular channel) in such a way that, the mass flow ratio in both the case remain the same (4.9%) in order to compare the effect of bypass channel dimension in the resulting thrust vector angle and thrust performance. Reynolds-averaged Navier-Stokes (RANS) equations with k-omega SST turbulence model have been implemented through numerical computations to capture the three-dimensional steady characterstics of the flow field. Results showed a significant change in the shock structure with the fromation of recirculation zone near the bypass injection port in both the case with a variation of shock structure and thrust performance for different geometry bypass lines. It was found that, thrust vector angle increases as injection length increases in the span wise direction

Compressible flow characteristics around a biconvex arc airfoil in a channel

Shock wave-boundary layer interactions (SWBLI) are observed in several practical high-speed internal flows, such as compressor blades, turbine cascades, nozzles and so on. Shock induced oscillations (SIO), aerodynamic instabilities so-called buffet flows, flutter, aeroacoustic noise and vibration are the detrimental consequences of this unsteady shock-boundary layer interactions. In the present study, a numerical computation has been performed to investigate the compressible flow characteristics around a 12% thick biconvex circular arc airfoil in a two dimensional channel. Reynolds averaged Navier-Stokes equations with two equation k-ω shear stress transport (SST) turbulence model have been applied for the computational analysis. The flow field characteristics has been studied from pressure ratio (ratio of back pressure, pb to inlet total pressure, p01) of 0.75 to 0.65. The present computational results have been compared and validated with the available experimental data. The results showed that the internal flow field characteristics such as shock wave structure, its behavior (steady or unsteady) and the corresponding boundary layer interaction are varied with pressure ratio. Self-excited shock oscillation was observed at certain flow conditions. Moreover, the mode of unsteady shock oscillation and its frequency are varied significantly with change of pressure ratio