KANNAN B T | SRM UNIVERSITY (original) (raw)

Papers by KANNAN B T

Purpose: This study aims to investigate the effects of nozzle momentum flux distribution on the f... more Purpose: This study aims to investigate the effects of nozzle momentum flux distribution on the flow field characteristics.

Design/methodology/approach : The nozzle configuration consists of a central nozzle surrounded by four nozzles. All nozzles have same diameter and constant separation between nozzles. OpenFOAM® is used for simulating the jet flow. Reynolds Averaged Navier Stokes (RANS) equations are solved iteratively with a first order closure for turbulence. Pitot-static tube with differential pressure transducer is used for mean velocity measurements. The comparison of computed results with experimental data shows similar trend and acceptable validation.

Findings: According to the results, the momentum flux distribution significantly alters the near field of multiple turbulent round jets. Highly non-linear decay region in the near field is found for the cases having higher momentum in the outer jets. As a result of merging, increased positive pressure is found in the mixing region. Higher secondary flows and wider mixing region are reported as a result of momentum transfer from axial to lateral directions by Reynolds stresses.

Research limitations/implications : The present study is limited to isothermal flow of air jet in air medium.

Social implications: Optimum momentum flux distribution in multijet injector of a combustor can reap better mixing leading to better efficiency and lesser environmental pollution.

Originality/value: As summary, the contributions of this paper in the field of turbulent jets are following: simulations for various momentum distribution cases have been performed. In all the cases, the flow at the nozzle exit is subsonic along with constant velocity profile. To simulate proper flow field, a large cylinder type domain with structured grid is used with refinements towards the nozzle exit and jet axis. The results show that the non-linearity increases with increase in momentum of outer jets. Longer merging zones are reported for cases with higher momentum in outer nozzles using area averaged turbulent kinetic energy. Similarly, wider mixing regions are reported using secondary flow parameter and visualizations.

Turbulent jet flows with multiple nozzle inlets are investigated computationally using OpenFOAM. ... more Turbulent jet flows with multiple nozzle inlets are investigated computationally using OpenFOAM. The configurations vary from single to five axisymmetric nozzles. First order closure is used with Reynolds Averaged Navier-Stokes equations. Computed results are compared with the available experimental data. The effect of nozzle configuration on the jet flow field is discussed with predicted mean flow and turbulent flow data. Near field of multiple jets shows non-linear behavior. Multiple jets show better performance in the near field based on entrainment, secondary flows and area averaged turbulent kinetic energy. The downstream evolution of multiple jets differs for configurations with and without central jet. The shape parameter confirms the evolution of multiple jets towards an axisymmetric jet.

Conventional method of defining half velocity widths is applicable only for axisymmetric jets. He... more Conventional method of defining half velocity widths is applicable only for axisymmetric jets. Hence, geometry based definition of half velocity width is used for non-circular jets. Usefulness of this method becomes less when there is no symmetry based on geometry. Hence, a new half velocity width is proposed based on equivalent area method. Newly proposed half velocity width is computed for a conventional circular jet and a non-circular jet. The comparison of half velocity widths obtained using conventional method and newly proposed method shows good agreement with each other for circular jet. Geometry based half width and equivalent area based half velocity width agree in the near field for the non-circular jet. Equivalent area based method is found as better representation of half velocity width for non-circular turbulent jets.

The present work is a numerical investigation which examines the effects of geometric parameters ... more The present work is a numerical investigation which examines the effects of geometric parameters on the axisymmetric jet impingement heat transfer. Two cases are considered such as flat plate, and grooved plate. Nozzle diameter (d) of 2 cm is fixed as constant, nozzle-to-plate spacing (H) of 4cm is used for validation and 8cm for all the other simulations. The jet flow is in the range of fully turbulent flow with Reynolds number of 23,000. Grid independent study reveals each model has its own style of dependency. Validation of the turbulence model for H/d=2 shows secondary peak at exact location. Results about effect of grooves are discussed in detail based on the surface Nusselt number and averaged Nusselt number.

The present work is a numerical simulation of a turbulent free jet issuing from an axisymmetric o... more The present work is a numerical simulation of a turbulent free jet issuing from an axisymmetric orifice into quiescent air environment. The numerical simulation was carried out by solving the Reynolds Averaged Navier-Stokes equations using OpenFOAM. The standard two-equation k-ɛ eddy viscosity turbulence model was used to simulate the turbulent flow field in a three dimensional cylindrical domain. The numerical predictions are compared with experimental data in order to assess the capability/limitations of the turbulence model to reproduce the physics involved and the code using jet case examined in this work. The standard k-ɛ model predictions in terms of centre line mean velocity decay, spread rate, entrainment, self-similarity, turbulence intensities and Reynolds stress, are found to reproduce the physics of the jet flow and agree approximately with experimental data. New information such as evolution of turbulent kinetic energy budget, length scales and time scales is provided.

This work reports the evolution of multiple turbulent jets that emanate from axisymmetric nozzles... more This work reports the evolution of multiple turbulent jets that emanate from axisymmetric nozzles arranged in a particular configuration. Five cases were considered for this work. Reynolds number based on the equivalent diameter was kept constant for all the cases. The measurements along the geometric centreline provides details about the axial evolution. Profiles of measured mean velocity shows the merger and growth of multiple jets at various axial downstream locations. Non-linear behaviour of multiple jets was found in the near field region. The evolutions of flow from nozzle configurations with and without central jets were found to be different.

This paper presents the results from numerical simulation of jet flow emanating from a cruciform ... more This paper presents the results from numerical simulation of jet flow emanating from a cruciform orifice. OpenFOAM was used for the simulations with RANS standard k-ε turbulence model. The results were validated with the experimental data of Quinn (2013). Mean flow quantities and turbulent quantities were discussed in detail. The evolution of cruciform shape to circular shape was described with various contours of mean flow and turbulent quantities. Possible reasons for the evolution of cross sectional shapes were discussed.

This paper discusses about the basics of astronomy and simple satellite orbits. Various orbital p... more This paper discusses about the basics of astronomy and simple satellite orbits. Various orbital parameters for a complex orbit and transfer orbits from a parking orbit to various higher elliptic and parabolic orbits has also been discussed. The actual orbits will not only be based on the influence of earth’s gravity but also based on the gravities of other celestial objects in the solar system in the real case, but we have considered the 2 body problem for simple analysis. The objective is to show case the difference, difficulties and advantages of low cost transfer orbits from high energy transfer orbits both theoretically and with the help of computer program. Transfer from a simple parking orbit to out of plane target orbit and a simple lunar swing-by orbit is the thrust area of our paper which was discussed more based on the Keplerian co-ordinate system.

Research limitations/implications : The present study is limited to isothermal flow of air jet in air medium.

Social implications: Optimum momentum flux distribution in multijet injector of a combustor can reap better mixing leading to better efficiency and lesser environmental pollution.