A numerical study of mixing in a microchannel with circular mixing chambers

Ansari, Mubashshir Ahmad,Kim, Kwang‐,Yong Wiley Subscription Services, Inc., A Wiley Company 2009 AIChE Journal Vol.55 No.9

<P><B>Abstract</B></P><P>The mixing of fluids in a microchannel is numerically investigated using three‐dimensional Navier–Stokes equations. The microchannel has circular mixing chambers that are designed to create a self‐circulating flow that operates at low Reynolds numbers. The investigations have been performed on a design that comprises of four circular mixing chambers that are joined together with constriction channels. The study has been carried out in two parts. Firstly, the mixing and the flow field are analyzed for a wide range (1–250) of the Reynolds number. Secondly, the effects of two design parameters, namely, the ratio, w/d, of the width of the constriction channel to the diameter of the circular chamber, and the angle, θ, between the outer walls of the chamber and the connection channel, on the mixing and the flow field have been evaluated. The mixing has been evaluated using a parameter, called mixing index, which is based on the variance of the mass fraction. The mixing index at the end of the device increases rapidly with the Reynolds number. The presence of a flow recirculation zone in the circular chamber is found to be effective in enhancing mixing, especially for larger Reynolds numbers. The mixing performance improves with an increase in θ, and with a decrease in w/d. The characteristics of the pressure drop have also been investigated as a function of the Reynolds number and geometric parameters. © 2009 American Institute of Chemical Engineers AIChE J, 2009</P>

A novel passive micromixer based on unbalanced splits and collisions of fluid streams

Ansari, Mubashshir Ahmad,Kim, Kwang-Yong,Anwar, Khalid,Kim, Sun Min IOP 2010 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.20 No.5

<P>A new passive micromixer based on the concept of unbalanced splits and cross-collisions of fluid streams is designed and fabricated. Experimental and numerical studies have been carried out on the micromixer at Reynolds numbers ranging from 10 to 80. The three-dimensional Navier–Stokes equations have been used to analyze the mixing and flow behavior of the micromixer, which is composed of two sub-channels of unequal widths which repeatedly undergo splitting and recombination. The difference between the mass flow rates in the two sub-channels creates an unbalanced collision of the two fluid streams. Mixing is mainly due to the combined effect of unbalanced collisions of the fluid streams and Dean vortices. The micromixer shows interesting mixing behavior for different ratios of the widths of the two split sub-channels. The sub-channels wherein the major sub-channel is twice as wide as the minor sub-channel exhibit the highest mixing performance at Reynolds numbers larger than 40. The results show the lowest mixing performance for the case of uniform width, where balanced collisions occur.</P>

Integrated vortex micro T-mixer for rapid mixing of fluids

Mubashshir Ahmad Ansari,김광용,김선민 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

This article reports a novel design of a micromixer showing efficient mixing by creating vortex flow in a microchannel. The main microchannel splits and recombines into two sub-channels at a tangential position that facilitates the generation of vortex flow. The height and width of the sub-channels are half the height and width of the main microchannel. The fluid flow and the mixing characteristics of the micromixer were demonstrated by performing numerical and experimental studies at different Reynolds numbers (Re = 2.5~40). The micromixer was fabricated using a standard soft lithography process. The fluid streams from the subchannels create vortex flow in the main microchannel which increases the interface area. The idea of creating multiple vortex flow zones by repeating the design of vortex T-mixer was successfully shown in mixing enhancement. The design of the micromixer is promising for mixing the fluids in a short length of the microchannel (5.5 mm at Re = 10 and 2.6 mm at Re = 40).

New 4′-substituted benzoyl-β-D glycoside from the fruit pulp of Terminalia belerica with antiplatelet and antioxidant potency

Vaseem Ahmad Ansari,Muhammad Arif,Md. Sarfaraj Hussain,Hefazat Hussain Siddiqui,Rakesh Kumar Dixit 한국한의학연구원 2016 Integrative Medicine Research Vol.5 No.4

Background The fruit Terminalia belerica is a rich source of vitamins, acids, and nutraceuticals which have free radical scavenging activity. Thus, the ethanolic extract of fruit and its isolated compound (Tb-01) were intended to estimate antiplatelet and antioxidant activities. Methods The ethanolic extract was submitted to Si-gel CC and the compound was isolated. The compound Tb-01 was characterized as benzoyl-β-D-(4′→10″ geranilanoxy)-pyranosides on the basis of spectral data [ultra violet (UV), infrared (IR), 1H nuclear magnetic resonance (NMR), 13C NMR, and Mass Spectroscopy] and chemical analyses. The ethanolic extract and Tb-01 at different concentrations were in vitro screened for antiplatelet and antioxidant activity. The antiplatelet activity was carried out by using platelet rich plasma prepared by centrifugation of rabbit whole blood (containing 0.9% sodium citrate as anticoagulant) and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl, reducing power, and nitric oxide anion scavenging activity models. Results The compound Tb-01 was an amorphous brownish powder, yield 0.64% (w/w), melting point 105–110 °C, Retardation factor/Retention Value (Rf value) at 0.42 in methanol:chloroform (20:80) solvent system, UV absorption maxima at 243 nm, and molecular peak [M + H]+ at 394.15 m/z. It was observed that the ethanolic extract and Tb-01 at different concentrations showed significant antiplatelet and antioxidant activity. The antioxidant activity, like scavenging of 1,1-diphenyl-2-picrylhydrazyl radicals, nitric oxide radical, and reductive power were found to be concentration-dependent and increased when increasing amounts of sample were used. Conclusion Mass spectra and 1H NMR confirmed the isolated compound structure which was supported by 13C NMR and IR spectra. Tb-01could be promising for future applications in the treatment of blood clots, pulmonary embolism, and other related diseases.

Groove 형상에 따른 수동형 미세유체혼합기 성능 연구

Muabshshir Ahmad Ansari,한태헌,Khalid Anwar,김선민,김광용 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Non-aligned bilayer square-wave bend microchannel for mixing

Mubashshir Ahmad Ansari,박철우,허남건,김대중 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.12

A numerical study has been conducted on a modified design of square-wave bend microchannel to enhance mixing performance. The channel domain is divided into two layers of equal heights. The position of the layers is non-aligned in the lateral direction to construct a bilayer bend channel. The idea was to modulate the dean vortices formed in the bends. The bilayer bend channel shows enhanced mixing performance compared with a simple bend channel. Unlike a simple bend channel, a bilayer bend channel exhibits the formation of multiple vortices at different positions. This study has employed three values of offset positions at different Reynolds numbers.

Evaluation of surrogate models for optimizationof herringbone groove micromixer

Mubashshir Ahmad Ansari,김광용 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.2

Surrogate models have been applied to shape optimizations of a micromixer with the aim of assessing the performance of the models. The surrogate models considered include polynomial response surface approximation, Kriging, and radial basis neural network. In addition, a weighted average model based on global error measures is constructed. A mixing index at the exit of the micromixer is used as the objective function. The mixing index is calculated based on Navier-Stokes equations. Two cases of optimization, one with two design variables and the other with three design variables, have been tested. The design variables are selected among the ratio of the groove depth to channel height, the angle of groove, and the ratio of groove width to groove pitch. D-Optimal design generated sampling points are used for sampling. It is found that although the weighted average model does not predict the best optimal point, it does show consistent and reliable performance.

Novel ground tire rubber abrasive flow finishing media for surface finishing application

Irfan Ahmad Ansari 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

Synthesis and application of alumina supported nano zero valent zinc as adsorbent for the removal of arsenic and nitrate

Hafiz Badaruddin Ahmad,Muhammad Zuber,Yasir Abbas,Mazhar Hussain,Naeem Akhtar,Tariq Mahmood Ansari,Khalid Mahmood Zia,Shafiq Ahmad Arain 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.2

Arsenic and nitrate are ill-famed environmental pollutants that are responsible for various lethal diseases. Their removal from drinking water is very essential. In present study, newly synthesized alumina supported nano zerovalentzinc (Alumina-nZvZ) has been tested to remove arsenic and nitrate. Quantitative analyses of arsenic have beenperformed spectrophotometrically and while that of nitrates ions colorimetrically. After optimization of time and amountof adsorbent, Langmuir, Freundlich and D-R isotherms were applied to determine different parameters for the assessmentof adsorption. Synthesized samples were characterized by scanning electron microscopy (SEM) to evaluate porosityand void size. Alumina coated with reduced ZnCl2 showed better efficiency for removal of arsenic and nitrate ions. Kinetics of adsorption was evaluated by using pseudo first-order and pseudo second-order rate equations.

DAROONAJ AQRABI - A review

Rather, Shameem Ahmad,Ansari, Abdul Nasir,Siddiqui, Mansoor Ahmad Cellmed Orthocellular Medicine and Pharmaceutical 2017 셀메드 (CellMed) Vol.7 No.4

Doronicum Hookeri of family Asteraceae is an important medicinal drug distributed in Himalayas at Lachen and Tungu, Sikkim, Nepal, Bhutan, Tibet between 12,000 to 14,000 ft. Its roots are widely used as folk medicine and are commonly known as "Darunaj-aqrabi" in Unani and as "Leopard's bane" in English. Roots are traditionally used as a constituent of, act as a stomachic and dissolves trapped gases. Antibacterial and antifungal activities of D. hookeri roots have been previously reported. The methanolic extract of root part possessed higher phenolic content and thus higher free radical scavenging and reducing activities. The methanolic extract of this plant showed scavenging and antioxidant activities in DPPH (2,2- diphenyl-1-picryhydrazy) radical scavenging assay.