Ganesh Natarajan

Bio: Ganesh Natarajan is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Finite volume method & Hypersonic speed. The author has an hindex of 11, co-authored 48 publications receiving 340 citations. Previous affiliations of Ganesh Natarajan include University of Minnesota.

Design and performance of a three-dimensional micromixer with curved ribs

Abstract: The present work elucidates the design and performance analysis of a three-dimensional microchannel for its capability in mixing two different liquids. Present studies are based on cross-T micromixer in which obstacles are introduced in the form of three-dimensional curved ribs. The mixing efficiency, quantified by the mixing index (M), has been calculated for the present micromixer. Results are also compared with those having straight ribs and found an enhancement of about 15% in mixing efficiency for obstacles with curved surfaces. However, this superior mixing has been achieved with a lower pressure drop, which provides an added advantage not traditionally realized for passive micromixers. Moreover, extensive parametric studies are also conducted to understand the effect of several geometrical parameters that can influence the mixing which include the height of obstacles (h), number of modules (Nm), angle of inclination (θ) and size of the obstacles and also the inlet Re. However, there has been seen to have certain optimum values of some of the parameters for achieving maximum degree of mixing. The use of the curved ribs is found to provide superior mixing for a wide range of Re.

Numerical assessment of mixing performances in cross-T microchannel with curved ribs

Abstract: The present study considers a measure for enhancing mixing capability in micromixers. It incorporates a new design of obstacle, in the form of thin curved ribs, inside the micromixer and explored numerically for its mixing capabilities. The ribs can be uniquely defined by its chord length (l) and its thickness ( $$t_o$$ ). An in-house three-dimensional finite volume solver based on quasi-incompressible formulation is employed for the simulations. Results show that the use of curved obstacles enhances mixing efficiency with a significantly lower pressure drop compared to that of using straight ribs. Also, a set of parametric studies is conducted for effects of parameters namely number of modules, angle of inclination, size and spacing between the curved obstacles and with inlet Re. The results show that mixing can be enhanced with the increase in the number of modules, sizes etc. of the obstacles. About $$45\%$$ mixing enhancement has been observed for the channel having curved obstacles with of four modules and $$60^{\circ }$$ angle of inclination than that of no obstacle case.

A Ghost-Cell Immersed Boundary Method for Flow in Complex Geometry

Abstract: An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in complex geometries is presented. A boundary condition is enforced through a ghost cell method. The reconstruction procedure allows systematic development of numerical schemes for treating the immersed boundary while preserving the overall second-order accuracy of the base solver. Both Dirichlet and Neumann boundary conditions can be treated. The current ghost cell treatment is both suitable for staggered and non-staggered Cartesian grids. The accuracy of the current method is validated using flow past a circular cylinder and large eddy simulation of turbulent flow over a wavy surface. Numerical results are compared with experimental data and boundary-fitted grid results. The method is further extended to an existing ocean model (MITGCM) to simulate geophysical flow over a three-dimensional bump. The method is easily implemented as evidenced by our use of several existing codes.

Numerical study of mixing in wavy micromixers: comparison between raccoon and serpentine mixer

Abstract: We numerically analyze the mixing and pressure drop characteristics for flow through wavy micromixer of two geometrical configurations, namely raccoon and serpentine for different values of amplitude of the waviness of the mixer (α), wavelength of the waviness (λ), Reynolds number(Re) and Schmidt number(Sc). Three different flow regimes are identified depending on the parameters influencing the mixing index. The mixing index for both the raccoon and serpentine mixer is very close to unity in the first regime (0.1

Alterations of Cowl Lip for the Improvement of Supersonic-Intake Performance

Abstract: This paper discusses the performance enhancement of supersonic air intake model through the implementation of blunted leading edge to the cowl lip section of the model. A supersonic air intake model with sharp cowl leading edge is initially considered to numerically investigate its performance. Mach 3, supersonic intake flow through the base model has been simulated using commercial CFD package Ansys Fluent-15. Comparison of numerical predictions and experimental measurements is presented to demonstrate the correctness and accuracy of numerical frame work followed in the present study. Higher order spatial accuracy of the solver along with suitably refined mesh helped in accurate capturing of the flow field. Modification to the cowl lip is proposed as an effective method to improve the performance of the supersonic air intake. Two different blunted cowl leading edge geometries were investigated to identify the possible enhancement in performance parameters. Improvement in mass capture and combustion stability attained through the use of forward shifted blunt cowl leading edge is presented. It is also revealed through the present study that the blunt cowl leading edge can reduce the intensity of shock wave boundary layer interaction occurring at the isolator entry section. Deviation in total pressure recovery and flow distortion observed with different supersonic air intake models are also discussed with reasons for the same. This study demonstrates the scope of overall improvement in scramjet engine performance through the use of suitably positioned blunt cowl leading edge.

마이크로 채널에서 두 유체 혼합 = Two-fluid mixing in a microchannel

Abstract: Abstract A numerical study of the mixing of two fluids (pure water and a solution of glycerol in water) in a microchannel was carried out. By varying the glycerol content of the glycerol/water solution, the variation in mixing behavior with changes in the difference in the properties of the two fluids (e.g., viscosity, density and diffusivity) was investigated. The mixing phenomena were tested for three micromixers: a squarewave mixer, a three-dimensional serpentine mixer and a staggered herringbone mixer. The governing equations of continuity, momentum and solute mass fraction were solved numerically. To evaluate mixing performance, a criterion index of mixing uniformity was proposed. In the systems considered, the Reynolds number based on averaged properties was Re =1 and 10. For low Reynolds number ( Re =1), the mixing performance varied inversely with mass fraction of glycerol due to the dominance of molecular diffusion. The mixing performance deteriorated due to a significant reduction in the residence time of the fluid inside the mixers.