LES of non-newtonian physiological blood flow

Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition to turbulent non-Newtonian blood flow through a 3D model of arterial stenosis using the different non-Newtonian blood viscosity models. The computational domain has been chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the fourth harmonic of the Fourier series of the physiological pressure pulse (Womersley [1]). The computational results are presented in terms of the post-stenotic re-circulation zone, shear stress, mean and turbulent kinetic energy

LES of physiological pulsatile flow in a model arterial stenosis

Physiological pulsatile flow in a 3D model of arterial stenosisis investigated by applying Large Eddy Simulation(LES)technique. The computational domain has been chosen is as imple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the fourth harmonic of the Fourier series of the physiological pressure pulse. The flow Reynolds numbers which are typical of those found in human large artery are chosen in the present work. Transitions to turbulent of the pulsatile flow in the post stenosis are examined through the various numerical results and explained physically along with the relevant medical concerns

Physiological flow in a model of arterial stenosis

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Collective Memory and the Dutch East Indies

This book examines the afterlife of decolonization in the collective memory of the Netherlands. It offers a new perspective on the cultural history of representing the decolonization of the Dutch East Indies, and maps out how a contested collective memory was shaped. Taking a transdisciplinary approach and applying several theoretical frames from literary studies, sociology, cultural anthropology and film theory, the author reveals how mediated memories contributed to a process of what he calls “unremembering.” He analyses in detail a broad variety of sources, including novels, films, documentaries, radio interviews, memoires and historical studies, to reveal how five decades of representing and remembering decolonization fed into an unremembering by which some key notions were silenced or ignored. The author concludes that historians, or the historical guild, bear much responsibility for the unremembering of decolonization in Dutch collective memory

Natural convection flow from an isothermal horizontal cylinder in presence of heat generation

Natural convection laminar boundary layer flow from a horizontal circular cylinder with a uniform surface temperature at presence of heat generation has been investigated. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear systems of partial differential equations are solved numerically applying two distinct methods namely (i) implicit finite difference method together with the Keller box scheme and (ii) series solution technique. The results of the surface shear stress in terms of the local skin friction and the surface rate of heat transfer in terms of the local Nusselt number for a selection of the heat generation parameter γ (= 0.0, 0.2, 0.5, 0.8, 1.0) are obtained and presented in both tabular and graphical formats. Without effect of the internal heat generation inside the fluid domain for which we take γ = 0.0, the present numerical results show an excellent agreement with those of Merkin [J.H. Merkin, Free convection boundary layer on an isothermal horizontal circular cylinders, in: ASME/AIChE, Heat Transfer Conference, St. Louis, MO, August 9–11, 1976]. The effects of γ on the fluid velocity, temperature distribution, streamlines and isotherms are examined

LES of non-Newtonian physiological blood flow in a model of arterial stenosis

Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition-to-turbulent non-Newtonian blood flow through a 3D model of arterial stenosis by using five different blood viscosity models: (i) Power-law, (ii) Carreau, (iii) Quemada, (iv) Cross and (v) modified-Casson. The computational domain has been chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the first four harmonic series of the physiological pressure pulse (Loudon and Tordesillas [1]). The effects of the various viscosity models are investigated in terms of the global maximum shear rate, post-stenotic re-circulation zone, mean shear stress, mean pressure, and turbulent kinetic energy. We find that the non-Newtonian viscosity models enlarge the length of the post-stenotic re-circulation region by moving the reattachment point of the shear layer separating from the upper wall further downstream. But the turbulent kinetic energy at the immediate post-lip of the stenosis drops due to the effects of the non-Newtonian viscosity. The importance of using LES in modelling the non-Newtonian physiological pulsatile blood flow is also assessed for the different viscosity models in terms of the results of the dynamic subgrid-scale (SGS) stress Smagorinsky model constant, C<sub>s</sub>, and the corresponding SGS normalised viscosity

Investigation of physiological pulsatile flow in a model arterial stenosis using large-eddy and direct numerical simulations

Physiologicalpulsatileflow in a 3D model of arterialstenosis is investigated by using largeeddysimulation (LES) technique. The computational domain chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet using the first harmonic of the Fourier series of pressure pulse. In LES, the large scale flows are resolved fully while the unresolved subgrid scale (SGS) motions are modelled using a localized dynamic model. Due to the narrowing of artery the pulsatileflow becomes transition-to-turbulent in the downstream region of the stenosis, where a high level of turbulent fluctuations is achieved, and some detailed information about the nature of these fluctuations are revealed through the investigation of the turbulent energy spectra. Transition-to-turbulent of the pulsatileflow in the post stenosis is examined through the various numerical results such as velocity, streamlines, velocity vectors, vortices, wall pressure and shear stresses, turbulent kinetic energy, and pressure gradient. A comparison of the LES results with the coarse DNS are given for the Reynolds number of 2000 in terms of the mean pressure, wall shear stress as well as the turbulent characteristics. The results show that the shear stress at the upper wall is low just prior to the centre of the stenosis, while it is maximum in the throat of the stenosis. But, at the immediate post stenotic region, the wall shear stress takes the oscillating form which is quite harmful to the blood cells and vessels. In addition, the pressure drops at the throat of the stenosis where the re-circulated flow region is created due to the adverse pressure gradient. The maximum turbulent kinetic energy is located at the post stenosis with the presence of the inertial sub-range region of slope −5/3

Five-year outcome of clinical recovery and subjective well-being in older Dutch patients with schizophrenia

Outcome of schizophrenia in later life can be evaluated from different perspectives. The recovery concept has moved forward this evaluation, discerning clinical-based and patient-based definitions. Longitudinal data on measures of recovery in older individuals with schizophrenia are scant. This study evaluated the five-year outcome of clinical recovery and subjective well-being in a sample of 73 older Dutch schizophrenia patients (mean age 65.9 years; SD 5.4), employing a catchment-area based design that included both community living and institutionalized patients regardless of the age of onset of their disorder. At baseline (T1), 5.5% of participants qualified for clinical recovery, while at five-year follow-up (T2), this rate was 12.3% (p = 0.18; exact McNemar's test). Subjective well-being was reported by 20.5% of participants at T1 and by 27.4% at T2 (p = 0.27; exact McNemar's test). Concurrence of clinical recovery and subjective well-being was exceptional, being present in only one participant (1.4%) at T1 and in two participants (2.7%) at T2. Clinical recovery and subjective well-being were not correlated neither at T1 (p = 0.82; phi = 0.027) nor at T2 (p = 0.71; phi =-0.044). There was no significant correlation over time between clinical recovery at T1 and subjective well-being at T2 (p = 0.30; phi = 0.122) nor between subjective well-being at T1 and clinical recovery at T2 (p = 0.45; phi =-0.088). These results indicate that while reaching clinical recovery is relatively rare in older individuals with schizophrenia, it is not a prerequisite to experience subjective well-being