Large eddy simulation and preliminary modeling of the flow downstream a variable geometry swirler for gas turbine combustors

Eldrainy, Yehia A.; Saqr, Khalid M.; Aly, Hossam S.; Lazim, Tholudin Mat; Jaafar, Mohammad Nazri Mohd.

doi:10.1016/j.icheatmasstransfer.2011.05.017

Cited by 31 publications

(9 citation statements)

References 20 publications

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“…Pope 63 proposed the measure of LES turbulence resolution M x t ( , ) and showed that such measure provides valid ground for assessing the quality and validity of LES. Saqr 38,64 and Saqr et al 20,53,65,66 developed a form of Pope's LES resolution criterion that is suitable for application in any CFD code and tailored for the Smagorinsky-Lilly SGS model. This form has been utilized in the present work to ensure that LES resolved at least 80% of the total kinetic energy budget in all cases.…”

Section: Cfd Procedure Large Eddy Simulation Of Pulsatile Non-newtonmentioning

confidence: 99%

“…Moreover, we show for the first-time dynamic changes in viscosity induced by the complex arterial geometry that lead to spatiotemporally persistent flow stagnation and recirculation zones with shear-rate conditions that can possibly induce platelet aggregation and subsequent embolism. Finally, we report for the first time the presence of Rankine vortex [18][19][20] (a type of forced vortex similar to tornado core) in the cerebral circulation and its effect on blood flow and ischemia development.…”

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confidence: 94%

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The hemodynamic complexities underlying transient ischemic attacks in early-stage Moyamoya disease: an exploratory CFD study

Rashad

Saqr

Fujimura

et al. 2020

Sci Rep

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Moyamoya disease (MMD) is a rare cerebro-occlusive disease with unknown etiology that can cause both ischemic and hemorrhagic stroke. MMD is characterized by progressive stenosis of the terminal internal carotid artery (ICA) and development of basal brain collaterals. Early-stage MMD is known to cause hemodynamic insufficiency despite mild or moderate stenosis of the intracranial arteries, but the exact mechanism underlying this pathophysiological condition is undetermined. We used highresolution Large eddy Simulations to investigate multiple complex hemodynamic phenomena that led to cerebral ischemia in five patients with early-stage MMD. The effects of transitional flow, coherent flow structures and blood shear-thinning properties through regions of tortuous and stenosed arteries were explored and linked to symptomatology. It is evidently shown that in some cases complex vortex structures, such as Rankine-type vortices, redirects blood flow away from some arteries causing significant reduction in blood flow. Moreover, partial blood hammer (PBH) phenomenon was detected in some cases and led to significant hemodynamic insufficiency. PBH events were attributed to the interaction between shear-thinning properties, transitional flow structures and loss of upstream pressure-velocity phase lag. We clearly show that the hemodynamic complexities in early-stage MMD could induce ischemia and explain the non-responsiveness to antiplatelet therapy.Moyamoya disease (MMD) is a rare cerebrovascular disease, characterized by bilateral occlusive changes at the internal carotid artery (ICA) terminus and an abnormal collaterals development at the base of the brain 1 . MMD is more prevalent in East Asian populations and can present as either ischemic or hemorrhagic stroke 2 . MMD can occur in pediatric or adult populations 2-4 and can present as bilateral or unilateral disease involvement 5 . The basic pathology of MMD, including its temporal profile, is clearly indicated by Suzuki's angiographic staging 1 , demonstrating the pathologic conversion of the cerebral vascular supply from internal carotid (IC) to the external carotid (EC) system 6 . Insufficiency of this 'IC-EC conversion system' could result in either ischemic or hemorrhage MMD presentations.Recent advance in high resolution magnetic resonance (HR-MR) vascular wall imaging enabled us to diagnose MMD even in its early stage, by demonstrating the characteristic vascular wall structure such as outer-diameter narrowing and the concentric stenosis of the affected intracranial arteries 7-9 . All of these characteristic findings by HR-MR vascular wall imaging are precisely reflected by vascular wall pathology of MMD including medial layer thinning and the waving of internal elastic lamina 10,11 . Accurate diagnosis of the early-stage MMD is clinically important because it could manifest as transient ischemic attacks (TIA) and/or cerebral infarction due to the significant hemodynamic compromise, despite its mild or moderate stenosis. Nonetheless, the mechanism

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Section: Cfd Procedure Large Eddy Simulation Of Pulsatile Non-newtonmentioning

confidence: 99%

mentioning

confidence: 94%

The hemodynamic complexities underlying transient ischemic attacks in early-stage Moyamoya disease: an exploratory CFD study

Rashad

Saqr

Fujimura

et al. 2020

Sci Rep

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“…Besides, several convergence problems have been reported to exist for RSM simulations of vortex flows [18][19][20]. On the other hand several variants of the k-ε model have been used successfully to model swirling flows with recirculation zones and PVC in different combustion systems [21][22][23][24][25][26][27][28][29][30][31]. Jochmann et al [32] compared the performance of the latter model with the RSM for predicting PVC in a gas turbine combustor and found the only slight differences exist between both models.…”

Section: Turbulence Modelingmentioning

confidence: 99%

Effects of hydrogen addition on the structure and pollutant emissions of a turbulent unconfined swirling flame

Rohani

Saqr

2012

International Communications in Heat and Mass Transfer

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“…Although there have been several arguments regarding the correctness of using eddyviscosity turbulence models in modeling swirling flows, numerous recent works proved that the mean flow phenomena in swirling flows can be predicted accurately using such models. Eldrainy et al [18] demonstrated the validity of RANS/eddy-viscosity models in predicting the main characteristics of swirling flows with comparison to the LES results.Osama A. Marzouk and E. David Huckaby [19] performed several numerical simulations of a co-axial particle-laden swirling air flow using three versions of the k-epsilon turbulence model (standard, re-normalization group-RNG, and realizable). When comparing the results of the simulations with experimental mean velocity profiles, they demonstrated that the standard model achieved the best over-all performance.…”

Section: Turbulence Modelmentioning

confidence: 99%

Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber

et al. 2011

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International audienceNumerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800A degrees C by the mean of cooling holes technique

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Large eddy simulation and preliminary modeling of the flow downstream a variable geometry swirler for gas turbine combustors

Cited by 31 publications

References 20 publications

The hemodynamic complexities underlying transient ischemic attacks in early-stage Moyamoya disease: an exploratory CFD study

The hemodynamic complexities underlying transient ischemic attacks in early-stage Moyamoya disease: an exploratory CFD study

Effects of hydrogen addition on the structure and pollutant emissions of a turbulent unconfined swirling flame

Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber

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