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Hsueh-chen Lee - One of the best experts on this subject based on the ideXlab platform.

  • a nonlinear weighted least squares finite element method for the carreau yasuda non Newtonian Model
    Journal of Mathematical Analysis and Applications, 2015
    Co-Authors: Hsueh-chen Lee
    Abstract:

    Abstract We study a nonlinear weighted least-squares finite element method for the Navier–Stokes equations governing non-Newtonian fluid flows by using the Carreau–Yasuda Model. The Carreau–Yasuda Model is used to describe the shear-thinning behavior of blood. We prove that the least-squares approximation converges to linearized solutions of the non-Newtonian Model at the optimal rate. By using continuous piecewise linear finite element spaces for all variables and by appropriately adjusting the nonlinear weighting function, we obtain optimal L 2 -norm error convergence rates in all variables. Numerical results are given for a Carreau fluid in the 4-to-1 contraction problem, revealing the shear-thinning behavior. The physical parameter effects are also investigated.

  • A nonlinear weighted least-squares finite element method for the Carreau–Yasuda non-Newtonian Model
    Journal of Mathematical Analysis and Applications, 2015
    Co-Authors: Hsueh-chen Lee
    Abstract:

    Abstract We study a nonlinear weighted least-squares finite element method for the Navier–Stokes equations governing non-Newtonian fluid flows by using the Carreau–Yasuda Model. The Carreau–Yasuda Model is used to describe the shear-thinning behavior of blood. We prove that the least-squares approximation converges to linearized solutions of the non-Newtonian Model at the optimal rate. By using continuous piecewise linear finite element spaces for all variables and by appropriately adjusting the nonlinear weighting function, we obtain optimal L 2 -norm error convergence rates in all variables. Numerical results are given for a Carreau fluid in the 4-to-1 contraction problem, revealing the shear-thinning behavior. The physical parameter effects are also investigated.

David Kilpatrick - One of the best experts on this subject based on the ideXlab platform.

  • non Newtonian blood flow in human right coronary arteries transient simulations
    Journal of Biomechanics, 2006
    Co-Authors: Barbara Mary Johnston, Peter Rex Johnston, Stuart Corney, David Kilpatrick
    Abstract:

    This study looks at pulsatile blood flow through four different right coronary arteries, which have been reconstructed from biplane angiograms. A non-Newtonian blood Model (the Generalised Power Law), as well as the usual Newtonian Model of blood viscosity, is used to study the wall shear stress in each of these arteries over the entire cardiac cycle. The difference between Newtonian and non-Newtonian blood Models is also studied over the whole cardiac cycle using the recently generalised global non-Newtonian importance factor. In addition, the flow is studied by considering paths of massless particles introduced into the flow field. The study shows that, when studying the wall shear stress distribution for transient blood flow in arteries, the use of a Newtonian blood Model is a reasonably good approximation. However, to study the flow within the artery in greater detail, a non-Newtonian Model is more appropriate.

  • Non-Newtonian blood flow in human right coronary arteries: steady state simulations.
    Journal of biomechanics, 2004
    Co-Authors: Barbara Mary Johnston, Peter Rex Johnston, Stuart Corney, David Kilpatrick
    Abstract:

    This study looks at blood flow through four different right coronary arteries, which have been reconstructed from bi-plane angiograms. Five non-Newtonian blood Models, as well as the usual Newtonian Model of blood viscosity, are used to study the wall shear stress in each of these arteries at a particular point in the cardiac cycle. It was found that in the case of steady flow in a given artery, the pattern of wall shear stress is consistent across all Models. The magnitude of wall shear stress, however, is influenced by the Model used and correlates with graphs of shear stress versus strain for each Model. For mid-range velocities of around 0.2 m s(-1) the Models are virtually indistinguishable. Local and global non-Newtonian importance factors are introduced, in an attempt to quantify the types of flows where non-Newtonian behaviour is significant. It is concluded that, while the Newtonian Model of blood viscosity is a good approximation in regions of mid-range to high shear, it is advisable to use the Generalised Power Law Model (which tends to the Newtonian Model in those shear ranges in any case) in order to achieve better approximation of wall shear stress at low shear.

Peter Hunter - One of the best experts on this subject based on the ideXlab platform.

  • non Newtonian blood flow analysis for the portal vein based on a ct image
    Abdominal Imaging, 2012
    Co-Authors: Adam Bartlett, Peter Hunter
    Abstract:

    In this paper we perform a Newtonian and a non-Newtonian blood flow analysis for a patient-specific portal vein (PV), which was digitized from a CT image. The non-linear relationship between the shear stress and shear rate was simulated using a Carreau Model. We found that, under normal physiological conditions, the computed data from the non-Newtonian Model was only marginally different from that of the Newtonian Model. However, when the portal flow was severely reduced (e.g., 10% of its normal value), the difference between the two Models was significant. Hence we suggest that the Newtonian Model is a good approximation for portal flow in physiological conditions whereas a non-Newtonian Model should be used in pathological conditions when the very low flow rate induces a much higher blood viscosity.

  • Abdominal Imaging - Non-Newtonian blood flow analysis for the portal vein based on a CT image
    Lecture Notes in Computer Science, 2012
    Co-Authors: Adam Bartlett, Peter Hunter
    Abstract:

    In this paper we perform a Newtonian and a non-Newtonian blood flow analysis for a patient-specific portal vein (PV), which was digitized from a CT image. The non-linear relationship between the shear stress and shear rate was simulated using a Carreau Model. We found that, under normal physiological conditions, the computed data from the non-Newtonian Model was only marginally different from that of the Newtonian Model. However, when the portal flow was severely reduced (e.g., 10% of its normal value), the difference between the two Models was significant. Hence we suggest that the Newtonian Model is a good approximation for portal flow in physiological conditions whereas a non-Newtonian Model should be used in pathological conditions when the very low flow rate induces a much higher blood viscosity.

Michel Deville - One of the best experts on this subject based on the ideXlab platform.

  • pulsatile flow of non Newtonian fluids through arterial stenoses
    Journal of Biomechanics, 1996
    Co-Authors: Cheng Tu, Michel Deville
    Abstract:

    The problem of blood flow through stenoses is solved using the incompressible generalized Newtonian Model. The Herschel-Bulkley, Bingham and power-law fluids are incorporated. The geometry corresponds to a rigid circular tube with a partial occlusion. Calculations are performed by a Galerkin finite-element method. For the pulsatile case, a predictor-corrector time marching scheme is used with an adaptive time step. Results are obtained for steady and pulsatile physiological flows. Computations show that the memory effects taken into account in the Model affect deeply the flow compared with Newtonian reference case. The disturbances are stronger by their vorticity intensity and persist after the geometrical obstacle. This is especially true for severe stenoses.

Barbara Mary Johnston - One of the best experts on this subject based on the ideXlab platform.

  • non Newtonian blood flow in human right coronary arteries transient simulations
    Journal of Biomechanics, 2006
    Co-Authors: Barbara Mary Johnston, Peter Rex Johnston, Stuart Corney, David Kilpatrick
    Abstract:

    This study looks at pulsatile blood flow through four different right coronary arteries, which have been reconstructed from biplane angiograms. A non-Newtonian blood Model (the Generalised Power Law), as well as the usual Newtonian Model of blood viscosity, is used to study the wall shear stress in each of these arteries over the entire cardiac cycle. The difference between Newtonian and non-Newtonian blood Models is also studied over the whole cardiac cycle using the recently generalised global non-Newtonian importance factor. In addition, the flow is studied by considering paths of massless particles introduced into the flow field. The study shows that, when studying the wall shear stress distribution for transient blood flow in arteries, the use of a Newtonian blood Model is a reasonably good approximation. However, to study the flow within the artery in greater detail, a non-Newtonian Model is more appropriate.

  • Non-Newtonian blood flow in human right coronary arteries: steady state simulations.
    Journal of biomechanics, 2004
    Co-Authors: Barbara Mary Johnston, Peter Rex Johnston, Stuart Corney, David Kilpatrick
    Abstract:

    This study looks at blood flow through four different right coronary arteries, which have been reconstructed from bi-plane angiograms. Five non-Newtonian blood Models, as well as the usual Newtonian Model of blood viscosity, are used to study the wall shear stress in each of these arteries at a particular point in the cardiac cycle. It was found that in the case of steady flow in a given artery, the pattern of wall shear stress is consistent across all Models. The magnitude of wall shear stress, however, is influenced by the Model used and correlates with graphs of shear stress versus strain for each Model. For mid-range velocities of around 0.2 m s(-1) the Models are virtually indistinguishable. Local and global non-Newtonian importance factors are introduced, in an attempt to quantify the types of flows where non-Newtonian behaviour is significant. It is concluded that, while the Newtonian Model of blood viscosity is a good approximation in regions of mid-range to high shear, it is advisable to use the Generalised Power Law Model (which tends to the Newtonian Model in those shear ranges in any case) in order to achieve better approximation of wall shear stress at low shear.