A Study of the Effects of the Pore Size on Turbulence Intensity and Turbulence Length Scale in Forced Convection Flow in Porous Media

Huang, Ching-Wei; Su, T. S.; Srikanth, Vishal; Кузнецов, А. В.

doi:10.1615/ihtc16.cov.023328

Cited by 2 publications

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“…The formation of a recirculating vortex restricted in between the solid obstacles of the porous medium at low porosity is also reported in Linsong et al (2018). The solid surfaces restrict the vortices from growing larger than the pore space (Huang et al 2018). Desai & Vafai (1994) showed that higher gap width in an annulus geometry decreases the heat transfer rate in natural convection.…”

Section: Introductionmentioning

confidence: 74%

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The evolution of turbulent micro-vortices and their effect on convection heat transfer in porous media

2022

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New insight into the contribution of the microscale vortex evolution to convection heat transfer in porous media is presented in this paper. The objective is to determine how the microscale vortices influence convection heat transfer in turbulent flow inside porous media. The microscale temperature distribution is analysed using flow visualization in two dimensions using streamlines and in three dimensions using the Q-criterion. The pertinent observations are supplemented with a comparison of surface skin friction and heat transfer using: (i) surface skin-friction lines and (ii) the joint probability density function of the pressure and skin-friction coefficients, along with the Nusselt number. The microscale flow phenomena observed are corroborated with the features of the frequency spectra of the drag coefficient and macroscale Nusselt number. The large eddy simulation technique is used in this study to investigate the flow field inside a periodic porous medium. The Reynolds numbers of the flow are 300 and 500. The porous medium consists of solid obstacles in the shape of square and circular cylinders. Two distinct flow regimes are represented by using the porosities of 0.50 and 0.87. The results show that the surface Nusselt number distribution is dependent on whether the micro-vortices are attached to or detached from the surface of the obstacle. The spectra of the macroscale Nusselt number and the pressure drag are similar, signifying a correlation between the dynamics of heat transfer and the microscale turbulent structures. Both vortex shedding and secondary flow instabilities are observed that significantly influence the Nusselt number. The fundamental insight gained in this paper can inform the development of more robust macroscale models of convection heat transfer in turbulent flow in porous media.

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Section: Introductionmentioning

confidence: 74%

“…The solid surfaces restrict the vortices from growing larger than the pore space (Huang et al. 2018). Desai & Vafai (1994) showed that higher gap width in an annulus geometry decreases the heat transfer rate in natural convection.…”

Section: Introductionmentioning

confidence: 99%

The evolution of turbulent micro-vortices and their effect on convection heat transfer in porous media

2022

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Association of Bovine Arch Anatomy With Incident Stroke After Transcatheter Aortic Valve Replacement

Lo Russo,

Alarouri,

Al‐Abcha

et al. 2024

JAHA

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Background Acute ischemic stroke complicates 2% to 3% of transcatheter aortic valve replacements (TAVRs). This study aimed to identify the aortic anatomic correlates in patients after TAVR stroke. Methods and Results This is a single‐center, retrospective study of patients who underwent TAVR at the Mayo Clinic between 2012 and 2022. The aortic arch morphology was determined via a manual review of the pre‐TAVR computed tomography images. An “a priori” approach was used to select the covariates for the following: (1) the logistic regression model assessing the association between a bovine arch and periprocedural stroke (defined as stroke within 7 days after TAVR); and (2) the Cox proportional hazards regression model assessing the association between a bovine arch and long‐term stroke after TAVR. A total of 2775 patients were included (59.6% men; 97.8% White race; mean±SD age, 79.3±8.4 years), of whom 495 (17.8%) had a bovine arch morphology. Fifty‐seven patients (1.7%) experienced a periprocedural stroke. The incidence of acute stroke was significantly higher among patients with a bovine arch compared with those with a nonbovine arch (3.6% versus 1.7%; P =0.01). After adjustment, a bovine arch was independently associated with increased periprocedural strokes (adjusted odds ratio, 2.16 [95% CI, 1.22–3.83]). At a median follow‐up of 2.7 years, the overall incidence of post‐TAVR stroke was 6.0% and was significantly higher in patients with a bovine arch even after adjusting for potential confounders (10.5% versus 5.0%; adjusted hazard ratio, 2.11 [95% CI, 1.51–2.93]; P <0.001). Conclusions A bovine arch anatomy is associated with a significantly higher risk of periprocedural and long‐term stroke after TAVR.

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A Study of the Effects of the Pore Size on Turbulence Intensity and Turbulence Length Scale in Forced Convection Flow in Porous Media

Cited by 2 publications

References 0 publications

The evolution of turbulent micro-vortices and their effect on convection heat transfer in porous media

The evolution of turbulent micro-vortices and their effect on convection heat transfer in porous media

Association of Bovine Arch Anatomy With Incident Stroke After Transcatheter Aortic Valve Replacement

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