Mechanical Engineeringhttp://repository.iitgn.ac.in/handle/123456789/5872017-08-16T13:08:43Z2017-08-16T13:08:43ZSolitary waves in dimer binary collision model: a comparative study with granular dimersAhsan, ZaidJayaprakash, K. R.http://repository.iitgn.ac.in/handle/123456789/30362017-07-18T09:33:07Z2017-06-25T00:00:00ZSolitary waves in dimer binary collision model: a comparative study with granular dimers
Ahsan, Zaid; Jayaprakash, K. R.
We study the complex nonlinear mechanism of uni- and bi-directional energy channeling realized in a locally resonant
three-dimensional (3D) unit-cell model comprising of an external mass subjected to a 3D nonlinear local potential with a spherical
internal rotator in the limit of low energy excitation. We discuss two families of non-stationary regimes corresponding to in-plane
and out-of-plane energy channeling which are manifested by 3D transformation of general in-plane oscillations of the external
element to orthogonally reoriented in-plane and out-of-plane oscillations. The energy flow is fully controlled by the orientation of
the internal rotator. Numerical simulations are in very good correspondence with the multi scale analysis.
2017-06-25T00:00:00ZThree-dimensional energy channeling in the unit-cell model coupled to a spherical rotator I: bidirectional energy channelingJayaprakash, K. R.Starosvetsky, Yulihttp://repository.iitgn.ac.in/handle/123456789/30242017-07-13T09:09:51Z2017-07-01T00:00:00ZThree-dimensional energy channeling in the unit-cell model coupled to a spherical rotator I: bidirectional energy channeling
Jayaprakash, K. R.; Starosvetsky, Yuli
This work is the first one in a two part series devoted to the analysis of the complex nonlinear mechanism of three-dimensional energy channeling emerging in a locally resonant three-dimensional, single-cell unit. The system under consideration comprises of an external mass subjected to a three-dimensional linear local potential with an internal spherical rotator. In the present study we focus on the analysis of the regimes of three-dimensional, bidirectional energy transport realized in the limit of low-energy excitations. Unlike the previously reported studies, this system under consideration exhibits rich nonlinear phenomena concerning the dynamics and the bifurcation structure of highly non-stationary regimes. Thus, in the considered limit we unveil analytically the two distinct families of non-stationary regimes corresponding to the in-plane as well as the out-of-plane bidirectional energy channeling. This phenomenon of bidirectional energy channeling is manifested by the three-dimensional, recurrent transformation of general in-plane oscillations of the external element to the orthogonally reoriented in-plane and out-of-plane ones. This three-dimensional energy flow is fully controlled by the internal spherical rotator coupled to the external mass. Here we also show that the regimes corresponding to the bidirectional energy channeling as well as spontaneous energy locking reported in the previously considered planar cases can be generalized analytically to the three-dimensional case. To this end we use a regular multi-scale analysis which enables to characterize and predict the intrinsic mechanisms governing the highly non-stationary regimes of the three-dimensional energy flow. Numerical simulations are found to be in extremely good correspondence with the analysis.
2017-07-01T00:00:00ZGlobal stability analysis of axisymmetric boundary layer over a circular coneBhoraniya, RameshVinod, Narayananhttp://repository.iitgn.ac.in/handle/123456789/29792017-06-23T11:48:45Z2017-06-01T00:00:00ZGlobal stability analysis of axisymmetric boundary layer over a circular cone
Bhoraniya, Ramesh; Vinod, Narayanan
This paper presents a linear global stability analysis of the incompressible axisymmetric boundary layer on a circular cone. The base flow is considered parallel to the axis of the cone at the inlet. The angle of attack is zero and hence the base flow is axisymmetric. A favorable pressure gradient develops in the streamwise direction due to cone angle. The Reynolds number is calculated based on the cone radius
a
at the inlet and freestream velocity
U
∞
. The base flow velocity profile is fully nonparallel and nonsimilar. Linearized Navier-Stokes equations (LNSEs) are derived for the disturbance flow quantities in the spherical coordinates. The LNSEs are discretized using the Chebyshev spectral collocation method. The discretized LNSEs along with the homogeneous boundary conditions form a general eigenvalues problem. Arnoldi's iterative algorithm is used for the numerical solution of the general eigenvalues problem. The global temporal modes are computed for the range of Reynolds number from 174 to 1046, semicone angles
2
∘
,
4
∘
, and
6
∘
, and azimuthal wave numbers from 0 to 5. It is found that the global modes are more stable at higher semicone angle
α
, due to the development of favorable pressure gradient. The effect of transverse curvature is reduced at higher
α
. The spatial structure of the eigenmodes shows that the flow is convectively unstable. The spatial growth rate
A
x
increases with an increase in
α
from
2
∘
to
6
∘
. Thus, the effect of an increase in
α
is to reduce the temporal growth rate
ω
i
and increase the
A
x
of the global modes at a given Reynolds number.
2017-06-01T00:00:00ZMetal-based nanoenergetic materials: Synthesis, properties, and applicationsSundaram, DilipYang, VigorYetter, Richard A.http://repository.iitgn.ac.in/handle/123456789/29562017-07-19T04:52:01Z2017-07-01T00:00:00ZMetal-based nanoenergetic materials: Synthesis, properties, and applications
Sundaram, Dilip; Yang, Vigor; Yetter, Richard A.
Metal particles are attractive candidate fuels for various propulsion and energy-conversion applications, primarily due to their high energy densities. Micron-sized particles present several drawbacks, such as high ignition temperatures and particle agglomeration, resulting in low energy-release rates. Nanoparticles, on the other hand, are quite attractive due to their unique and favorable properties, which are attributed to their high specific surface area and excess energy of surface atoms. As a result, there is a growing interest in employing metal nanoparticles in propulsion and energy-conversion systems. The present work provides a comprehensive review of the advances made over the past few decades in the areas of synthesis, properties, and applications of metal-based energetic nanomaterials. An overview of existing methods to synthesize nanomaterials is first provided. Novel approaches to passivate metal nanoparticles are also discussed. The physicochemical properties of metal nanoparticles are then examined in detail. Low-temperature oxidation processes, and ignition and combustion of metal nanoparticles are investigated. The burning behaviors of different energetic material formulations with metal nanoparticles such as particle-laden dust clouds, solid propellants, liquid fuels and propellants, thermite materials, and inter-metallic systems are reviewed. Finally, deficiencies and uncertainties in our understanding of the field are identified, and directions for future work are suggested.
2017-07-01T00:00:00Z