Mechanical Engineeringhttp://repository.iitgn.ac.in/handle/123456789/5872017-06-28T19:08:53Z2017-06-28T19:08:53ZGlobal 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/123456789/29562017-05-30T05:43:38Z2017-07-01T00:00:00ZMetal-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.
2017-07-01T00:00:00ZGlobal stability analysis of axisymmetric boundary layer over a circular coneBhoraniya, RameshNarayanan, Vinodhttp://repository.iitgn.ac.in/handle/123456789/29422017-05-23T09:55:49Z2017-04-01T00:00:00ZGlobal stability analysis of axisymmetric boundary layer over a circular cone
Bhoraniya, Ramesh; Narayanan, Vinod
This paper presents linear biglobal stability analysis of axisymmetric boundary layer over a circular cone. An incompressible flow over a sharp circular cone is considered with zero angle of attack. The base flow velocity profile is fully non-parallel and non-similar. Linearized Navier-Stokes (LNS) equations are derived for disturbance flow quantities using the standard procedure. The LNS equations are discretized using Chebyshev spectral collocation method. The governing equations along with boundary conditions form a general eigenvalues problem. The numerical solution of general eigenvalues problem is obtained using ARPACK subroutine, which uses Arnoldis iterative algorithm. The global temporal modes are computed for the range of Reynolds number and semi-cone angles(α)for the axisymmetric mode(N=0). The flow is found temporally and spatially stable for 1° semi-cone angle and the range of Reynolds numbers considered. However, flow becomes temporally unstable and spatially stable with the increase in semi-cone angle(α). The wave-like behaviour of the disturbances is found at small semi-cone angles (α).
2017-04-01T00:00:00ZAn input reconstruction approach for command following in linear MIMO systemsChavan, Roshan A.Kadam, Sujay D.Rajiv, AbhijithPalanthandalam-Madapusi, Harish J.http://repository.iitgn.ac.in/handle/123456789/28992017-04-28T14:01:22Z2017-04-01T00:00:00ZAn input reconstruction approach for command following in linear MIMO systems
Chavan, Roshan A.; Kadam, Sujay D.; Rajiv, Abhijith; Palanthandalam-Madapusi, Harish J.
2017-04-01T00:00:00Z