H. V. R. Mittal

Bio: H. V. R. Mittal is an academic researcher from Indian Institute of Technology Mandi. The author has contributed to research in topic(s): Cylinder & Reynolds number. The author has an hindex of 5, co-authored 14 publication(s) receiving 75 citation(s). Previous affiliations of H. V. R. Mittal include United Arab Emirates University & King Abdullah University of Science and Technology.

Locked-on vortex shedding modes from a rotationally oscillating circular cylinder

Abstract: Numerical simulations of unsteady two-dimensional flow around a rotationally oscillating circular cylinder, placed in a uniform cross flow of a constant property Newtonian fluid, are performed at a fixed Reynolds number of 200. The investigation is based on the solutions of stream function-vorticity formulation of Navier-Stokes equations on non-uniform polar grids using a higher order compact (HOC) formulation. The flow field is mainly influenced by Reynolds number, R e , maximum angular velocity of the cylinder, α m , and the frequency ratio, f / f 0 , which represents the ratio between the frequency of oscillation, f, and the natural vortex shedding frequency, f 0 . The ranges considered for these parameters are 0.5 ⩽ α m ⩽ 6.0 and 0.5 ⩽ f / f 0 ⩽ 3.0 . The resulting vortex formation modes and lock-on phenomena behind the cylinder as well as the fluid forces acting on the cylinder are analyzed. Occurrence of new multiple lock-on regions is demonstrated in detail by the variation of f and α m . The instances of high drag reduction at high values of α m are confirmed. Comparisons with previous numerical and experimental results verify the accuracy and validity of the present study.

A class of finite difference schemes for interface problems with an HOC approach

Abstract: In this paper, we propose a new methodology for numerically solving elliptic and parabolic equations with discontinuous coefficients and singular source terms. This new scheme is obtained by clubbing a recently developed Higher Order Compact (HOC) methodology with special interface treatment for the points just next to the points of discontinuity. The overall order of accuracy of the scheme is at least second. We first formulate the scheme for one-dimensional (1D) problems and then extend it directly to two-dimensional (2D) problems in polar coordinates. In the process, we also perform convergence and related analysis for both the cases. Finally, we show a new direction of implementing the methodology to 2D problems in cartesian coordinates. We then conduct numerous numerical studies on a number of problems, both for 1D and 2D cases including the flow past circular cylinder governed by the incompressible Navier-Stokes (N-S) equations. We compare our results with existing numerical and experimental results. In all the cases our formulation is found to produce better results on relatively coarser grids. For the circular cylinder problem, the scheme used is seen to capture all the flow characteristics including the famous von-Karman vortex street. Copyright c © 2010 John Wiley & Sons, Ltd.

A numerical study of initial flow past an impulsively started rotationally oscillating circular cylinder using a transformation-free HOC scheme

Abstract: The initial development of the two dimensional viscous, incompressible flow induced by an impulsively started circular cylinder which performs time dependent sinusoidal rotational oscillations about its axis is investigated numerically. The investigation is based on the solutions of stream function-vorticity formulation of Navier-Stokes equations on non-uniform polar grids using higher order compact formulation. The numerical method is validated by comparing the computed results with existing experimental and numerical results for Reynolds numbers Re = 150 and 500. The effects of forced oscillation frequency f and peak rotation rate αm on the early development of the flow structure in the near wake region are discussed. Results are given for the initial development with time of the flow structure at the rear of the cylinder at Re = 200. The details of the formation, movement, closure points, and strengths of the vortices behind the cylinder are presented. The velocity profiles at different locations and vorticity profiles at the surface of the cylinder are also shown. The effect of increase in αm on the timing of the formation of the vortices, the closed wake length, and the thickness of the boundary layer is investigated.

A numerical study of forced convection from an isothermal cylinder performing rotational oscillations in a uniform stream

Abstract: Forced convection from a heated rotationally oscillating circular cylinder placed in a uniform cross flow of constant properties fluid is investigated. The two-dimensional governing equations of flow motion and energy are solved numerically on non-uniform polar grids using a higher order compact (HOC) formulation. The flow and thermal fields are mainly influenced by Reynolds number, Re, Prandtl number, Pr, maximum angular velocity of the cylinder, α m , and the frequency ratio, f / f 0 , which represents the ratio between the oscillation frequency, f, and the natural vortex shedding frequency, f 0 . The numerical simulations are performed at Re = 200 , Pr = 0.5 - 1.0 , α m ∈ [ 0.5 , 4.0 ] and f / f 0 ∈ [ 0.5 , 3.0 ] . The resulting lock-on phenomena behind the cylinder is detected and thermal field is determined. Comparisons with previous numerical and experimental results verify the accuracy and the reliability of the present study. Variations in heat transfer coefficients within the lock-on ranges are investigated to build a connection between the heat transfer and the lock-on regimes.

Solving Immersed Interface Problems Using a New Interfacial Points-Based Finite Difference Approach

Abstract: A new finite difference scheme based on the higher-order compact technique is presented for solving problems with complex immersed interfaces in arbitrary dimensions. The scheme is designed for gen...

Flow and heat transfer of hybrid nanofluid over a permeable shrinking cylinder with Joule heating: A comparative analysis

Abstract: The objectives of the present study are (i) to observe the duality of solutions, and (ii) to investigate the flow and heat transfer of the hybrid nanofluid past a shrinking cylinder in the appearance of Joule heating. The single phase nanofluid model with modified thermophysical properties are used for the mathematical model. The similarity transformation simplifies the model (PDEs) into similarity (ordinary) differential equations. bvp4c solver is used to compute the reduced equations. For the validation part, the analytical solution is developed using an exact analytical method and compared with the numerical values for several cases. First and second solutions are observable for the shrinking cylinder case only if suction parameter is applied. Meanwhile, only the first solution is found to be stable from the stability analysis. The application of high suction strength make the reduced heat transfer rate is lower for hybrid nanofluid (Cu-Al2O3/water) than alumina-water nanofluid but, opposite result is found for the skin friction coefficient. The addition of curvature parameter (flat plate to cylinder) can quicken the separation process of boundary layer. This results are conclusive to the pair of alumina and copper only.

Finite element examination of hydrodynamic forces in grooved channel having two partially heated circular cylinders

Abstract: The present pagination is devoted to report case study on an examination of hydrodynamic forces experienced by partially heated circular obstacles in a grooved channel. To be more specific, the channel is considered as a computational domain. The heated rectangular ribs are introduced to attain grooved geometry. The two partially heated circular-shaped cylinders are placed in between channel as obstacles. The fluid is initiated with the parabolic velocity profile from an inlet. The outlet is carried with both Neumann and adiabatic conditions. The mathematical model is constructed to narrate the flow field. The solution is obtained by using the finite element method. The outcomes are shared in terms of velocity and temperature contour plots. The impact of the change of the distance between the partially heated circular obstacles is debated on both drag and lift coefficients.

Using radial basis function-generated finite differences (RBF-FD) to solve heat transfer equilibrium problems in domains with interfaces

Abstract: When thermal diffusivity does not vary smoothly within a computational domain, standard numerical methods for solving heat equilibrium problems often converge to an inaccurate solution. In the present paper, we discuss a mesh-free, radial basis function-generated finite difference (RBF-FD)-based method for designing stencil weights that can be applied directly to data that crosses an interface. The approach produces a very accurate solution when thermal diffusivity varies smoothly on either side of an interface. It continues to produce high-quality results when a region between two interfaces is much smaller that the distance between adjacent discrete data nodes in the domain (as becomes the case for thin, nearly insulating layers). We give several test cases that demonstrate the method solving heat equilibrium problems to 4th-order accuracy in the presence of smoothly-curved interfaces.

Locked-on vortex shedding modes from a rotationally oscillating circular cylinder

Abstract: Numerical simulations of unsteady two-dimensional flow around a rotationally oscillating circular cylinder, placed in a uniform cross flow of a constant property Newtonian fluid, are performed at a fixed Reynolds number of 200. The investigation is based on the solutions of stream function-vorticity formulation of Navier-Stokes equations on non-uniform polar grids using a higher order compact (HOC) formulation. The flow field is mainly influenced by Reynolds number, R e , maximum angular velocity of the cylinder, α m , and the frequency ratio, f / f 0 , which represents the ratio between the frequency of oscillation, f, and the natural vortex shedding frequency, f 0 . The ranges considered for these parameters are 0.5 ⩽ α m ⩽ 6.0 and 0.5 ⩽ f / f 0 ⩽ 3.0 . The resulting vortex formation modes and lock-on phenomena behind the cylinder as well as the fluid forces acting on the cylinder are analyzed. Occurrence of new multiple lock-on regions is demonstrated in detail by the variation of f and α m . The instances of high drag reduction at high values of α m are confirmed. Comparisons with previous numerical and experimental results verify the accuracy and validity of the present study.

Non-Newtonian ferrofluid flow over an unsteady contracting cylinder under the influence of aligned magnetic field

Abstract: In this paper the basic design of the study is comparison between the magnetohydrodynamic (MHD) flow and heat transfer of non-Newtonian (Sodium Alginate) base fluid with three ferroparticles, that is Cobalt ferrite ( C o F e 2 O 4 ) , Manganese–Zinc ferrite ( M n − Z n F e 2 O 4 ) and Nickel–Zinc ferrite ( N i − Z n F e 2 O 4 ) over an unsteady contracting cylinder In this inspection the aligned magnetic field effects are taken into consideration The process of bringing the governing PDE's to the form of ODE's is achieved with the similarity transformations At this point the changed over conditions are numerically understood by Runge-Kutta method of fourth order with shooting technique The non-Newtonian behavior is discussed employing Casson model By means of visual image we explain and interpret the behaviours of several emerging parameters on the velocity and temperature profiles Calculation for the local skin friction coefficient and local Nusselt number are evaluated and examined for the deserving parameters Also, it is seen that the alignment of magnetic field helps in advancing the velocity profile Comparing the nanoparticles it is observed that C o F e 2 O 4 nanoparticle is dominant over the other for the local skin friction values whereas N i − Z n F e 2 O 4 nanoparticle has higher rate of heat transfer