Slip flow over micron-sized spherical particles at intermediate Reynolds numbers

Hamid Niazmand,Morteza Anbarsooz 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.9

A numerical investigation has been performed to identify the rarefaction effects on the flow structure of an isolated micron-sized spherical particle. An isothermal sphere in the slip flow regime 10-3 ≤ Kn ≤ 10-1 at intermediate Reynolds numbers (1 ≤ Re ≤ 50) is considered. The Navier-Stokes equations are solved by a control volume technique in conjunction with the velocity slip boundary condition. It was found that the wake region can shrink considerably as the Knudsen number increases. Furthermore, the skin friction and pressure drag coefficients decrease as the Knudsen number increases due to the reduction in normal velocity gradients and shrinkage of the wake region, respectively. Engineering correlations for predicting the total drag coefficient in the slip flow regime are presented.

Thermal and second-law analysis of a micro- or nanocavity using direct-simulation Monte Carlo.

Mohammadzadeh, Alireza,Roohi, Ehsan,Niazmand, Hamid,Stefanov, Stefan,Myong, Rho Shin Published by the American Physical Society through 2012 Physical review. E, Statistical, nonlinear, and so Vol.85 No.5

<P>In this study the direct-simulation Monte Carlo (DSMC) method is utilized to investigate thermal characteristics of micro- or nanocavity flow. The rarefied cavity flow shows unconventional behaviors which cannot be predicted by the Fourier law, the constitutive relation for the continuum heat transfer. Our analysis in this study confirms some recent observations and shows that the gaseous flow near the top-left corner of the cavity is in a strong nonequilibrium state even within the early slip regime, Kn=0.005. As we obtained slip velocity and temperature jump on the driven lid of the cavity, we reported meaningful discrepancies between the direct and macroscopic sampling of rarefied flow properties in the DSMC method due to existence of nonequilibrium effects in the corners of cavity. The existence of unconventional nonequilibrium heat transfer mechanisms in the middle of slip regime, Kn=0.05, results in the appearance of cold-to-hot heat transfer in the microcavity. In the current study we demonstrate that existence of such unconventional heat transfer is strongly dependent on the Reynolds number and it vanishes in the large values of the lid velocity. As we compared DSMC solution with the results of regularized 13 moments (R13) equations, we showed that the thermal characteristic of the microcavity obtained by the R13 method coincides with the DSMC prediction. Our investigation also includes the analysis of molecular entropy in the microcavity to explain the heat transfer mechanism with the aid of the second law of thermodynamics. To this aim, we obtained the two-dimensional velocity distribution functions to report the molecular-based entropy distribution, and show that the cold-to-hot heat transfer in the cavity is well in accordance with the second law of thermodynamics and takes place in the direction of increasing entropy. At the end we introduce the entropy density for the rarefied flow and show that it can accurately illustrate departure from the equilibrium state.</P>

Experimental study of argon dilution effects on NOx emission in a non-premixed flame in comparison with nitrogen

Abdolrasoul Rangrazi,Hamid Niazmand,Hamid Momahedi Heravi 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.8

The effects of nitrogen and argon dilution on NOX emission of turbulent propane-air non-premixed flame in a furnace are experimentally investigated. Dilution is an effective process in reducing NOX emission, since diluents cause an increase in the mass flow of the fuel, and consequently the temperature in the combustion chamber and NOX emission decreases. We measured NOX emission and temperature for a wide range of dilution and equivalence ratios. The results show that nitrogen dilution is more effective than argon dilution in reducing NOX emission. In addition,both dilutions caused the yellow color of the non-premixed flame to turn blue, which indicates more complete combustion and better mixing of fuel and oxidant.

Teucrium polium L. Improved Heart Function and Inhibited Myocardial Apoptosis in Isolated Rat Heart Following Ischemia-Reperfusion Injury

Maryam Mahmoudabady,Faezeh Sadat Talebian,Narges Amel Zabihi,Seyed Abdolrahim Rezaee,Saeed Niazmand 대한약침학회 2018 Journal of pharmacopuncture Vol.21 No.3

Objectives: Myocardial reperfusion is the only logical cure for ischemic heart disease. However, ischemic-reperfusion (I/R) injury is one of the underlying factors facilitating and accelerating the apoptosis in the myocardium. This study set to investigate the impact of Teucrium polium (TP) hydro-alcoholic extract on I/R induced apoptosis in the isolated rat heart. Methods: Isolated rat hearts were classified into six groups. The control samples were subjected to 80 min of perfusion with Krebs–Henseleit bicarbonate (KHB) buffer; in control-ischemia group, after primary perfusion (20 min) the hearts were exposed to global ischemia (20 min) and reperfusion (40 min). Pretreated groups were perfused with 500 μM of vitamin C and various TP concentrations (0.5, 1, 2 mg/ml) for 20 min, and then the hearts were exposed to ischemia and reperfusion for 20 min and 40 min, respectively. Cardiodynamic parameters including rate pressure product (RPP), heart rate (HR), the maximum up/down rate of left ventricular pressure (±dp/dt), left ventricular developed pressure (LVDP), and coronary artery flow (CF) were achieved from Lab Chart software data. The Bax and BCl-2 gene expressions were measured in heart samples. Results: Hearts treated with TP extract and vit C represented a meaningful improvement in cardiac contractile function and CF. The overexpression of Bcl-2, downregulation of Bax, and improvement of apoptotic index (Bax/Bcl-2) were observed in pretreated TP extract and vit C hearts. Conclusion: The TP extract was found to ameliorate the cardiac function in the reperfused myocardium. Also, it can hinder apoptotic pathways causing cardioprotection.

Teucrium polium L. Improved Heart Function and Inhibited Myocardial Apoptosis in Isolated Rat Heart Following Ischemia-Reperfusion Injury

Mahmoudabady, Maryam,Talebian, Faezeh Sadat,Zabihi, Narges Amel,Rezaee, Seyed Abdolrahim,Niazmand, Saeed KOREAN PHARMACOPUNCTURE INSTITUTE 2018 Journal of pharmacopuncture Vol.21 No.3

Objectives: Myocardial reperfusion is the only logical cure for ischemic heart disease. However, ischemic-reperfusion (I/R) injury is one of the underlying factors facilitating and accelerating the apoptosis in the myocardium. This study set to investigate the impact of Teucrium polium (TP) hydro-alcoholic extract on I/R induced apoptosis in the isolated rat heart. Methods: Isolated rat hearts were classified into six groups. The control samples were subjected to 80 min of perfusion with Krebs-Henseleit bicarbonate (KHB) buffer; in control-ischemia group, after primary perfusion (20 min) the hearts were exposed to global ischemia (20 min) and reperfusion (40 min). Pretreated groups were perfused with $500{\mu}M$ of vitamin C and various TP concentrations (0.5, 1, 2 mg/ml) for 20 min, and then the hearts were exposed to ischemia and reperfusion for 20 min and 40 min, respectively. Cardiodynamic parameters including rate pressure product (RPP), heart rate (HR), the maximum up/down rate of left ventricular pressure (${\pm}dp/dt$), left ventricular developed pressure (LVDP), and coronary artery flow (CF) were achieved from Lab Chart software data. The Bax and BCl-2 gene expressions were measured in heart samples. Results: Hearts treated with TP extract and vit C represented a meaningful improvement in cardiac contractile function and CF. The overexpression of Bcl-2, downregulation of Bax, and improvement of apoptotic index (Bax/Bcl-2) were observed in pretreated TP extract and vit C hearts. Conclusion: The TP extract was found to ameliorate the cardiac function in the reperfused myocardium. Also, it can hinder apoptotic pathways causing cardioprotection.