Department of Mechanical Engineering

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

We study the stability of surface waves on the radial film flow created by a vertical cylindrical water jet striking a horizontal plate. In such flows, surface waves have been found to be unstable and can cause transition to turbulence. This surface-wave-induced transition is different from the well-known Tollmien-Schlichting wave-induced transition. The present study aims at understanding the instability and the transition process. We do a temporal stability analysis by assuming the flow to be locally two-dimensional but including spatial variations to first order in the basic flow. The waves are found to be dispersive, mostly unstable, and faster than the mean flow. Spatial variation is the major destabilizing factor. Experiments are done to test the results of the linear stability analysis and to document the wave breakup and transition. Comparison between theory and experiments is fairly good and indicates the adequacy of the model. © 2005 American Institute of Physics.

World University root node

Physics of Fluids

Waves on radial film flows

Near-wall structures in turbulent natural convection at Rayleigh numbers of 1010 to 1011 at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR = 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. The mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in Rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log-normal probability distribution function, independent of the Rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-Rayleigh-number turbulent natural convection are likely to be laminar mixed convection type. © 2005 Cambridge University Press.

Journal of Fluid Mechanics

Plume structure in high-Rayleigh-number convection

In this paper we present experimental measurements of buoyancy driven turbulent exchange flow in a vertical pipe (L/d ratios of 9-12). The flow is driven by an unstable density difference across the ends of the pipe, created using brine and distilled water. Away from either end, a fully developed region of turbulence exists with a linear density gradient. Using a mixing length model that accounts for the end effects, we obtain the turbulent scales and flux. The Nusselt number scales like the square root of the Rayleigh number (Nu ∼ Ra1/2). We give an empirical relation to quantify the end effects and hence calculate the flux of the salt (NaCl) given the aspect ratio of the pipe and the overall density difference across it. © 2005 Elsevier Ltd. All rights reserved.

International Journal of Heat and Mass Transfer

Experiments and a model of turbulent exchange flow in a vertical pipe

Coupled electrothermoelastic equations applicable to the analysis of smart structures have been derived from first principles. Using the equations and applying a layer-by-layer finite element model, the induced potential and mechanical deformations in the piezo and nonpiezo core material have been obtained for various cases of actuation and sensing of a smart beam under external mechanical load and actuation potential. The present study clearly brings out the essential difference between sensing and actuation. It is also brought out that the interaction between polarization and electric field in the piezo continuum leads to nonlinear distributed body force and nonsymmetric stress tensor. These nonlinear effects are found to have significant influence on the deformation of a smart beam under actuation. Shape control studies of multipatch smart beams have also been investigated.

AIAA Journal

Linear and Nonlinear Analysis of a Smart Beam Using General Electrothermoelastic Formulation

The vortex ring generated subsequent to the diffraction of a shock wave from the open end of a shock tube is studied using particle image velocimetry. We examine the early evolution of the compressible vortex ring for three-exit shock Mach numbers, 1.1, 1.2, and 1.3. For the three cases studied, the ring formation is complete at about tUb/D=2, where t is time, Ub is fluid velocity behind shock as it exits the tube and D is tube diameter. Unlike in the case of piston generated incompressible vortex rings where the piston velocity variation with time is usually trapezoidal, in the shock-generated vortex ring case the exit fluid velocity doubles from its initial value Ub before it slowly decays to zero. At the end of the ring formation, its translation speed is observed to be about 0.7 Ub. During initial formation and propagation, a jet-like flow exists behind the vortex ring. The vortex ring detachment from the tailing jet, commonly referred to as pinch-off, is briefly discussed. © 2004 American Institute of Physics.

Vortex ring formation at the open end of a shock tube: A particle image velocimetry study

Laminar natural convection at unity Schmidt number over a horizontal surface with a weak normal velocity at the wall is studied using an integral analysis. To characterise the strength of the blowing, we define a non-dimensional parameter called the blowing parameter. After benchmarking with the no blowing case, the effect of the blowing parameter on boundary layer thickness, velocity and concentration profiles is obtained. Weak blowing is seen to increase the wall shear stress. For blowing parameters greater than unity, the diffusional flux at the wall becomes negligible and the flux is almost entirely due to the blowing. © 2004 Elsevier Science Ltd.

International Communications in Heat and Mass Transfer

Integral analysis of laminar indirect free convection boundary layers with weak blowing for schmidt No. ∼1

Using laws of conservation, a general electro-thermo-elastic formulation has been developed for the analysis of smart structures. Based on this formulation a layer-by-layer finite element model has been developed using variational principle. It is shown that the layer-by-layer finite element modeling effectively captures the continuity of shear stress across the interface between piezo-layers and the metallic host material. Several studies of actuation and sensing of single and multi-patch smart beams have been carried out. The key difference between actuation and sensing has been brought out with regard to the variation of shear stress along the span at interfaces between piezo patch and the core. In addition, the influence of electric field along the span of a piezo cantilever beam has been studied and it is shown that this electric field produces a large transverse shear stress resulting in a step like deformation of the piezo beam. It is envisaged that this concept can be used to develop a switch in a MEMS device. Copyright © 2004 The American Institute of Aeronautics and Astronautics Inc. All rights reserved.

Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

Electro-thermo-elastic formulation and layer-by-layer modeling of a smart beam with piezoelectric patches

In this paper, we propose a new transaction model, named as Team Transaction for distributed, cooperative computing on mobile ad hoc networks. The proposed model captures the mobility and distributive properties inherently found in a vigorous team activity as in a game of soccer and also has an efficient recovery mechanism to cope up with the failures of mobile nodes. © Springer-Verlag 2004.

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Team transaction: A new transaction model for mobile ad hoc networks

Journal of Immunology and Immunopathology

Effect of cow's urine on immune status of experimental rats

This paper presents a study on the effect of nonlinearities of an elastomeric bearing on isolated lag dynamics and coupled rotor/fuselage ground resonance stability of an idealized bearingless rotor blade. The rotor blade is modeled as an elastic beam with a nonlinear elastomer and a rigid torque tube. First, amplitudedependent natural frequency of the blade in lag mode is analyzed using numerical perturbation technique. Then the problem of amplitude-dependent stability of the coupled rotor/fuselage system under ground resonance condition is investigated. The stability of the system is analyzed by two approaches, namely, 1) by eigenanalysis of the linearized equations and 2) by response of the nonlinear system to an initial disturbance by time integration. The results of the eigenanalysis indicate that the effect of amplitude seems to be more dominant on the progressive lag mode damping than on regressive lag mode damping. It is also observed that so far as the stability in ground resonance is concerned there exist optimum locations for the attachment of both the elastomer and torque tube. Results of the time-domain analysis of the nonlinear equations indicate clearly that the stability of the system is dependent on the magnitude of initial disturbance.