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Study of the flow around a cylinder from the subcritical to supercritical regimes
Zhang, Xian-Tao,Li, Zhi-Yu,Fu, Shi-Xiao,Ong, Muk Chen,Chen, Ying Techno-Press 2014 Ocean systems engineering Vol.4 No.3
The objective of the present simulations is to evaluate the applicability of the standard $k-{\varepsilon}$ turbulence model in engineering practice in the subcritical to supercritical flow regimes. Two-dimensional numerical simulations of flow around a circular cylinder at $Re=1{\times}10^5$, $5{\times}10^5$ and $1{\times}10^6$, had been performed using Unsteady Reynolds-Averaged Navier Stokes (URANS) equations with the standard $k-{\varepsilon}$ turbulence model. Solution verification had been studied by evaluating grid and time step size convergence. For each Reynolds number, several meshes with different grid and time step size resolutions were chosen to calculate the hydrodynamic quantities such as the time-averaged drag coefficient, root-mean square value of lift coefficient, Strouhal number, the coefficient of pressure on the downstream point of the cylinder, the separation angle. By comparing the values of these quantities of adjacent grid or time step size resolutions, convergence study has been performed. Solution validation is obtained by comparing the converged results with published numerical and experimental data. The deviations of the values of present simulated quantities from those corresponding experimental data become smaller as Reynolds numbers increases from $1{\times}10^5$ to $1{\times}10^6$. This may show that the standard $k-{\varepsilon}$ model with enhanced wall treatment appears to be applicable for higher Reynolds number turbulence flow.
Caitlin Fern Wee,Yao Hao Teo,Yao Neng Teo,Nicholas LX Syn,Ray Meng See,Shariel Leong,Alicia Swee Yan Yip,Zhi Xian Ong,Chi-Hang Lee,Mark Yan-Yee Chan,Kian-Keong Poh,Ching Ching Ong,Lynette LS Teo,Devin 한국심초음파학회 2022 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.30 No.3
Recent studies have shown that sodium/glucose cotransporter 2 (SGLT2) inhibitors might exert favourable changes on cardiac parameters as observed on cardiovascular imaging. We conducted a systematic review and meta-analysis to determine the effects of SGLT2 inhibitors on cardiac imaging parameters. Four electronic databases (PubMed, Embase, Cochrane, Scopus) were searched for studies in which the effects of SGLT2 inhibitors on cardiac imaging parameters were examined. Studies in which a population was administered SGLT2 inhibitors and analysed by echocardiography and/or cardiac magnetic resonance (CMR) imaging were included. Random-effects pair-wise meta-analysis models were utilized to summarize the studies. A total of 11 randomized controlled trials was included with a combined cohort of 910 patients. Comparing patients receiving SGLT2 inhibitors with subjects receiving placebo, the mean change in CMR-measured left ventricular mass (LVM) was −3.87 g (95% confidence interval [CI], −7.77 to 0.04), that in left ventricular end-systolic volume (LVESV) was −5.96 mL (95% CI, −10.52 to −1.41) for combined LVESV outcomes, that in left atrial volume index (LAVi) was −1.78 mL/m2 (95% CI, −3.01 to −0.55) for combined LAVi outcomes, and that in echocardiography-measured E/e′ was −0.73 (95% CI, −1.43 to −0.03). Between-group differences were not observed in LVM and LVESV after indexation. The only between-group difference that persisted was for LAVi. Treatment with SGLT2 inhibitors resulted in reduction in LAVi and E/e′ on imaging, indicating they might have an effect on outcomes associated with LV diastolic function.