Mechanical Engineeringhttp://repository.iitgn.ac.in/handle/123456789/5872018-05-20T17:45:44Z2018-05-20T17:45:44ZGlobal stability analysis of axisymmetric boundary layer over a circular cylinderBhoraniya, RameshNarayanan, Vinodhttp://repository.iitgn.ac.in/handle/123456789/36652018-05-15T10:46:17Z2018-05-01T00:00:00ZGlobal stability analysis of axisymmetric boundary layer over a circular cylinder
Bhoraniya, Ramesh; Narayanan, Vinod
This paper presents a linear global stability analysis of the incompressible axisymmetric boundary layer on a circular cylinder. The base flow is parallel to the axis of the cylinder at inflow boundary. The pressure gradient is zero in the streamwise direction. The base flow velocity profile is fully non-parallel and non-similar in nature. The boundary layer grows continuously in the spatial directions. Linearized Navier�Stokes (LNS) equations are derived for the disturbance flow quantities in the cylindrical polar coordinates. The LNS equations along with homogeneous boundary conditions forms a generalized eigenvalues problem. Since the base flow is axisymmetric, the disturbances are periodic in azimuthal direction. Chebyshev spectral collocation method and Arnoldi�s iterative algorithm is used for the solution of the general eigenvalues problem. The global temporal modes are computed for the range of Reynolds numbers and different azimuthal wave numbers. The largest imaginary part of the computed eigenmodes is negative, and hence, the flow is temporally stable. The spatial structure of the eigenmodes shows that the disturbance amplitudes grow in size and magnitude while they are moving towards downstream. The global modes of axisymmetric boundary layer are more stable than that of 2D flat-plate boundary layer at low Reynolds number. However, at higher Reynolds number they approach 2D flat-plate boundary layer. Thus, the damping effect of transverse curvature is significant at low Reynolds number. The wave-like nature of the disturbance amplitudes is found in the streamwise direction for the least stable eigenmodes.
2018-05-01T00:00:00ZA cable driven parallel robot for coconut farmNarayanan, ThejasVishnu, Rajendran S.Bhavani, Rao R.Singh, RatnakarVashista, Vineethttp://repository.iitgn.ac.in/handle/123456789/36172018-04-18T12:09:52Z0009-01-01T00:00:00ZA cable driven parallel robot for coconut farm
Narayanan, Thejas; Vishnu, Rajendran S.; Bhavani, Rao R.; Singh, Ratnakar; Vashista, Vineet
0009-01-01T00:00:00ZMetal-water mixtures for propulsion and energy-conversion applications: recent progress and future directionsSundaram, Dilip Srinivashttp://repository.iitgn.ac.in/handle/123456789/35822018-04-10T10:04:21Z2018-03-01T00:00:00ZMetal-water mixtures for propulsion and energy-conversion applications: recent progress and future directions
Sundaram, Dilip Srinivas
The metal-water system is attractive for propulsion and energy-conversion applications. Of all metals, aluminum is attractive due to its high energy density, relative safety, and low cost. Experimental studies provide new insight on the combustion and propulsive behaviors. The burning rate is found to be a strong function of both pressure and particle size. Furthermore, there is a wide scatter in the measured pressure exponents due to differences in particle size, pressure, pH, and equivalence ratio. A major problem with Al/H2O mixtures is incomplete combustion and poor impulses, thereby rendering Al/H2O mixtures unsuitable for practical applications. Efforts to improve the performance of Al/H2O mixtures have only met with moderate success. Although experiments have revealed these new trends, not much is offered in terms of the underlying physics and mechanisms. To explore the combustion mechanisms, theoretical models based on energy balance analysis have been developed. These models involve numerous assumptions and many complexities were either ignored or treated simplistically. The model also relies on empirical inputs, which makes it more a useful guide than a predictive tool. Future works must endeavor to conduct a more rigorous analysis of metal-water combustion. Empirical inputs should be avoided and complexities must be properly treated to capture the essential physics of the problem. The model should help us properly understand the experimental trends, offer realistic predictions for unexplored conditions, and suggest guidelines and solutions in order to realize the full potential of metal-water mixtures.
2018-03-01T00:00:00ZA review of super plastic formingChatterjee, RitamMukhopadhyay, Jyotihttp://repository.iitgn.ac.in/handle/123456789/35622018-04-04T11:47:26Z2018-03-01T00:00:00ZA review of super plastic forming
Chatterjee, Ritam; Mukhopadhyay, Jyoti
Super plasticity is the property exhibited by a few metals and alloys which involves, under tensile loading, very high elongation without necking until failure. This was first closely studied by Back ofen, Turner and Avery at MIT in 1964 [1]. Their pioneering work has since given rise to the multi-million dollar superplastic forming industry which has been highly successful in fabrication of complex shaped components mainly for the aerospace and automobile industries. The present paper reviews the developments related to superplastic forming that has taken place mainly over the past two decades. The process parameters, underlying mechanisms, constitutive equations and the process economics have been discussed in details. Furthermore, there is a brief discussion about quick-plastic forming which is an upcoming metal forming technique that promises to replace superplastic forming in the near future. This is largely due to the faster forming times associated with quick-plastic forming as compared to superplastic forming.
2018-03-01T00:00:00Z