ORCID Profile
0000-0002-2850-7861
Current Organisation
University of Adelaide
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Publisher: AIP Publishing
Date: 03-2021
DOI: 10.1063/5.0042601
Abstract: Understanding the effect of the artery curvature on the pressure drop inside the arteries is of great importance due to the existence of several curved portions inside the coronary arterial system. In this paper, an experimental model is developed to account for the effect of the curvature of the coronary arteries on the pressure drop and Fractional Flow Reserve (FFR). FFR is an index for the evaluation of the functional significance of coronary stenosis and is defined as the ratio of the coronary pressure downstream of the stenosis to its upstream value. To measure the pressure drop and FFR across curved artery models, three-dimensional-printed curved artery models are fabricated and installed in the test section of the experimental rig. For ratios of curvature radius over the artery diameter ranging from 2 to 7, there are a minimum value for the pressure drop and, hence, a corresponding maximum value for FFR at a ratio of approximately 3. For the curved arteries with larger curvature radii, the pressure drop increases, and consequently, FFR decreases with an increase in the radius. The results showed that an accurate evaluation of the pressure drop and FFR inside a curved coronary artery can only be achieved by accounting for the effect of curvature parameters including the curvature angle and radius, such that neglecting the effect of the artery curvature results in an underestimation of the pressure drop by about 25%–35%. The developed equation is able to determine the pressure drop inside a curved coronary artery model noninvasively.
Publisher: SAGE Publications
Date: 2014
DOI: 10.1155/2014/359872
Abstract: The variability of specific heats, internal irreversibility, heat and frictional losses are neglected in air-standard analysis for different internal combustion engine cycles. In this paper, the performance of an air-standard Diesel cycle with considerations of internal irreversibility described by using the compression and expansion efficiencies, variable specific heats, and losses due to heat transfer and friction is investigated by using finite-time thermodynamics. Artificial neural network (ANN) is proposed for predicting the thermal efficiency and power output values versus the minimum and the maximum temperatures of the cycle and also the compression ratio. Results show that the first-law efficiency and the output power reach their maximum at a critical compression ratio for specific fixed parameters. The first-law efficiency increases as the heat leakage decreases however the heat leakage has no direct effect on the output power. The results also show that irreversibilities have depressing effects on the performance of the cycle. Finally, a comparison between the results of the thermodynamic analysis and the ANN prediction shows a maximum difference of 0.181% and 0.194% in estimating the thermal efficiency and the output power. The obtained results in this paper can be useful for evaluating and improving the performance of practical Diesel engines.
Publisher: Springer Science and Business Media LLC
Date: 18-09-2014
Publisher: Elsevier BV
Date: 12-2018
Publisher: World Scientific Pub Co Pte Lt
Date: 15-11-2017
DOI: 10.1142/S1793524517500085
Abstract: The paper provides an analytical investigation, homotopy analysis method (HAM), of the heat and mass transfer for magnetohydrodynamic Oldroyd-B nanofluid flow over a stretching sheet in the presence of convective boundary condition. The PDE governing equations, which consist of equations of continuity, momentum, energy and nanoparticles, are converted to ordinary differential equations using similarity transformations. The current HAM solution demonstrates very good correlation with those of the previously published studies in the special cases. The influences of different flow physical parameters such as the Deborah numbers in terms of relaxation and retardation times ([Formula: see text], [Formula: see text]), magnetic parameter (M), Prandtl number (Pr), Brownian motion parameter (Nb), thermophoresis parameter (Nt), Lewis number (Le), and Biot number (Bi) on the fluid velocity component [Formula: see text], temperature distribution [Formula: see text] and concentration [Formula: see text] as well as the local Nusselt number [Formula: see text] and the local Sherwood number [Formula: see text] are discussed in detail.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 03-2015
Publisher: Springer Science and Business Media LLC
Date: 31-05-2014
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 06-2013
Publisher: Public Library of Science (PLoS)
Date: 24-10-2014
Publisher: Elsevier BV
Date: 03-2017
Publisher: Wiley
Date: 28-05-2020
DOI: 10.1002/CNM.3347
Publisher: Elsevier BV
Date: 12-2022
Publisher: Springer Science and Business Media LLC
Date: 13-12-2016
Publisher: Hindawi Limited
Date: 2014
DOI: 10.1155/2014/692728
Abstract: A coupled system of nonlinear ordinary differential equations that models the three-dimensional flow of a nanofluid in a rotating channel on a lower permeable stretching porous wall is derived. The mathematical equations are derived from the Navier-Stokes equations where the governing equations are normalized by suitable similarity transformations. The fluid in the rotating channel is water that contains different nanoparticles: silver, copper, copper oxide, titanium oxide, and aluminum oxide. The differential transform method (DTM) is employed to solve the coupled system of nonlinear ordinary differential equations. The effects of the following physical parameters on the flow are investigated: characteristic parameter of the flow, rotation parameter, the magnetic parameter, nanoparticle volume fraction, the suction parameter, and different types of nanoparticles. Results are illustrated graphically and discussed in detail.
Publisher: Informa UK Limited
Date: 12-06-2014
Publisher: Pleiades Publishing Ltd
Date: 05-2018
Publisher: Elsevier BV
Date: 2016
Publisher: AIP Publishing
Date: 02-2020
DOI: 10.1063/1.5139701
Abstract: Non-invasive measurement of pressure drop has great clinical significance for the treatment of coronary artery diseases. The objective of this study is to develop a relationship that can estimate pressure drop in a stenosed coronary artery model as a function of different parameters such as blood viscosity, artery length and diameter, flow rate and flow profile, and shape and degrees of stenosis. Experimental pressure measurements from a wide range of degrees of stenosis and critical simplified geometries of stenosis along with different unsteady flow profiles are employed to evaluate the pressure drop equation. To calculate the blockage term of the pressure drop, several experimental cases are investigated, and the results show that the blockage factor is strongly dependent on the shape and degree of stenosis. Furthermore, different unsteady flow profiles are applied to calculate the pulsatile pressure drop term, and it is found that the pulsatility parameter is not a function of the flow profile or the shape of the stenosis. However, it is only a function of the degree of stenosis. To test the validity of the developed equation, pressure drops through stenosed coronary artery models with the real physiological flow profile of the left and right coronary arteries were predicted and compared with the experimental measurements. The proposed equation is able to determine the pressure drop inside a stenosed coronary artery non-invasively using the measurement of the flow profile inside the artery as well as the images of the stenosed coronary artery obtained based on the non-invasive methods.
Publisher: ASME International
Date: 09-2021
DOI: 10.1115/1.4051923
Abstract: Temporal variations of the coronary arteries during a cardiac cycle are defined as the superposition of the changes in the position, curvature, and torsion of the coronary artery axis markers and the variations in the lumen cross-sectional shape due to the distensible wall motion induced by the pulse pressure and contraction of the myocardium in a cardiac cycle. This review discusses whether modeling of the temporal variations of the coronary arteries is needed for the investigation of hemodynamics specifically in time-critical applications such as a clinical environment. The numerical modelings in the literature that model or disregard the temporal variations of the coronary arteries on the hemodynamic parameters are discussed. The results in the literature show that neglecting the effects of temporal geometric variations is expected to result in about 5% deviation of the time-averaged pressure drop and wall shear stress values and also about 20% deviation of the temporal variations of hemodynamic parameters, such as time-dependent wall shear stress and oscillatory shear index. This review study can be considered as a guide for future studies to outline the conditions in which temporal variations of the coronary arteries can be neglected while providing a reliable estimation of hemodynamic parameters.
Publisher: Elsevier BV
Date: 02-2017
Publisher: Springer Science and Business Media LLC
Date: 19-02-2019
Publisher: Springer Science and Business Media LLC
Date: 26-11-2016
Publisher: Begell House
Date: 2018
Publisher: Elsevier BV
Date: 03-2016
Publisher: MDPI AG
Date: 26-04-2016
DOI: 10.3390/E18050131
Publisher: Springer Science and Business Media LLC
Date: 28-09-2015
Publisher: AIP Publishing
Date: 08-2021
DOI: 10.1063/5.0058765
Abstract: In this study, the effect of the shape of the stenosis on the flow transition in an artery is investigated. Different shapes of the stenosis including round, oval, elongated, half-moon, bean-shape, and crescent with and without eccentricity at a constant degree of stenosis (73%) are studied. A computational model, validated against the in-house Particle Image Velocimetry experimental results, is used to investigate the flow behavior. The results showed that the length of the jet region after the stenotic section varies significantly for different shapes of the stenosis. Based on the analysis of turbulent kinetic energy, power spectral density, and the spectral entropy of stream-wise velocity fluctuations, it was shown that eddies are formed after the dissipation of jet flow downstream of the stenosis. It was also shown that the intensity of the velocity fluctuations differs for different shapes of the stenosis. Furthermore, using the proper orthogonal decomposition method, it was shown that the shape of the stenosis has a significant impact on the downstream coherent structures. It was found that regardless of the degree of stenosis, specific shapes of the stenosis, such as round concentric, create less serious hemodynamic complications compared to the other shapes of the stenosis.
Publisher: Springer Science and Business Media LLC
Date: 06-2021
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 04-2016
Location: Iran (Islamic Republic of)
No related grants have been discovered for Navid Freidoonimehr.