Department of Mechanical Engineering

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IIT Jodhpur

The experimental farmland-channel-wetland systems (FCWS) in Guilin, China have been recently designed based on wetland water recycling systems in Midwest USA. The present article develops a methodology for simplifying the prediction of residence time as a function of the flow rate and physical shape of these contaminant removal systems. A series of two-dimensional simulation studies on surface flow through FCWS wetland of different shapes are performed. Parameters influencing hydraulic characteristics such as empirical values of inlet and outlet flow conditions, and wetland shapes are utilized as inputs to the study. Roughness coefficient was assumed to be constant across the different wetland designs discussed in this article. The mean velocity values within the wetland decreases with increase in ratio of variant inlet widths and wetland inflow rates. The results from the simulation are used as inputs for performing a multivariate multiparameter regression algorithm. This framework models the residence time within the wetland independently as a function of shape, mass inflow, and inlet geometry. This simplified model can be used with ease to evaluate existing as well as new wetland system designs for potential improvement in its function of desalting and filtering waters. © 2013 Desalination Publications. All rights reserved.

World University root node

Desalination and Water Treatment

Simplified residence time prediction models for constructed wetland water recycling systems

Formation of freckles during directional solidification of hypereutectic aqueous ammonium- chloride in a bottom cooled cavity is studied numerically. The system studied is thermally stable but solutally unstable, which causes plume type convection and formation of channels in the growing solid mush. Solidification of hypereutectic solutions is usually characterized by detached and drifting solid crystals, thus resulting in multiphase convection. The numerical simulation is performed using a fixed grid single domain approach with single-phase and multiphase convection phenomena. For the multiphase convection modeling in the solidifying system under consideration, the mushy region is assumed to consist of an immobile coherent zone containing packed equiaxed crystals and a mobile noncoherent zone where the solid crystals are able to move. The two zones are demarcated by a critical solid fraction criterion, referred to as the coherency point. The overall effects of drifting solid phase on the freckles formation are compared with the results from conventional single-phase convection model. © 2013 by ASME.

Journal of Thermal Science and Engineering Applications

Study of freckles formation during directional solidification under the influence of single-phase and multiphase convection

The application of high strength low alloy (HSLA) steels has been limited by unavailability of suitable joining and filler metals in submerged arc welding (SAW) processes. The present work aims at the design and development of flux for Submerged Arc Welding of HSLA steel. In the work L8 array of Taguchi Design is used to formulate eight types of fluxes to vary basicity index (BI) from 1.26 to 2.81 and to study the effect of flux constituents and basicity index on tensile strength, microhardness and microstructure of the weld metal. Empirical models for ultimate tensile strength and microhardness at the centre of weld versus flux constituents and basicity index have been developed. From the experiments it is found that ultimate tensile strength increase with increase of basicity index with minimum at 1.26 increases upto 2.33 and then further decreases whereas opposite in case of microhardness which is highest at 1.26 and minimum at 1.9. Increase of CaO in the flux increases ultimate tensile strength but microhardness remains unaffected whereas increase of SiO2 decreases ultimate tensile strength but microhardness remains constant. Microhardness decreases critically with increase of CaF2. © (2013) Trans Tech Publications, Switzerland.

Materials Science Forum

Effect of flux constituents and basicity index on mechanical properties and microstructural evolution of submerged arc welded high strength low alloy steel

In the past two decades, the lattice Boltzmann method (LBM) has offered itself as an alternative framework compared to the Navier Stokes simulations. However, the applicability of this method to simulate moving boundary problems has not received sufficient attention. The present study primarily focuses on developing and employing the halfway bounceback LBM to analyse the flow dynamics associated with the flapping motion of finite-thickness wings. A two-dimensional numerical model for one and two-winged 'clap and fling' stroke has been developed to study the aerodynamic performance of insect flight. The influence of kinematic parameters such as the percentage overlap between translational and rotational phase ξ, the separation between two wings δ and different Reynolds numbers Re on lift generation has been studied and presented here. In addition, the time-dependent behaviour of the leading and trailing edge vortices and their role on lift generation in clap and fling type kinematics has been identified. Based on simulation data, regression analysis was carried out to express the mean lift coefficient as a function of the varied parameters. Results show that overlap ratio ξ is the most influential parameter in enhancing lift. With increase in separation δ, the reduction in drag is far more dominant than the decrease in lift. With an increase in Re (which ranges between 8 and 128), the mean drag coefficient decreases monotonously, whereas the mean lift coefficient decreases to a minimum and increases thereafter. This behaviour of lift generation at higher Re was characterised by the 'wing-wake interaction' mechanism which was absent at low Re.

31st AIAA Applied Aerodynamics Conference

A lattice Boltzmann framework for analysis of 'clap and fling' motion of finite thickness membranes

This work aims at developing an analytical tool for damage detection to reduce maintenance costs. Daubechies wavelets are used in combination with spectral element method in order to study the dynamic response of an undamaged and damaged rod. Studies are conducted for variation of parameters such as damage intensity and size and their identification. © 2012 AIAA.

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

Identification of damage and damage parameters in structures using daubechies wavelets with spectral element method

This paper presents energy optimum capture of orbiting objects using a dual-arm robot mounted on a service satellite. An attempt has been made to formulate energy efficient trajectories for the dual-arm robot such that the reaction moments acting on the base satellite are minimum. To achieve this, first a local optimization problem is formulated exploiting redundancy associated with the constraints for reactionless manipulation. This method, however, fails to provide optimal trajectories. In order to overcome this disadvantage, an optimal control problem is formulated which not only helps in achieving energy efficient trajectories but also ensures zero reaction moments to the base satellite. The proposed method is validated using a 6-link planar dual-arm robot mounted on a service satellite.

1st International and 16th National Conference on Machines and Mechanisms, iNaCoMM 2013

Energy optimum reactionless path planning for capture of tumbling orbiting objects using a dual-arm robot

Closed-loops are inherent in many practical robotic systems. In this chapter, analyses of closed-loop systems are presented using the dynamic formulation given in Chaps. 5,6 and 7. © 2013, Springer Science+Business Media Dordrecht.

Intelligent Systems, Control and Automation: Science and Engineering

Closed-Loop Systems

As frequently noted in the literature on robotics (Sugihara et al. 2002; Kurazume et al. 2003; Vukobratovic et al. 2007; Kwon and Park 2009) and mechanisms (Duffy 1978; Chaudhary and Saha 2007), a higher Degrees-of-Freedom (DOF) joint, say, a universal, a cylindrical or a spherical joint, can be represented using a combination of several intersecting 1-DOF joints. For example, a universal joint also known as Hooke’s joint is a combination of two revolute joints, the axes of which intersect at a point, whereas a cylindrical joint is a combination of a revolute joint and a prismatic joint. Similarly, the kinematic behavior of a spherical joint may be simulated by the combination of three revolute joints whose axes intersect at a point. The joint axes can be represented using the popular Denavit and Hartenberg (DH) parameters (Denavit and Hartenberg 1955). For the spherical joints, an alternative approach using the Euler angles can also be adopted, as there are three variables. For spatial rotations, one may also use other minimal set representations like Bryant (or Cardan) angles, Rodriguez parameters, etc. or non-minimal set representation like Euler parameters, quaternion, etc. The non-minimal sets are not considered here due the fact that the dynamic models obtained in this book are desired in minimal sets. The minimal sets, other than Euler/Bryant angles, are discarded here as they do not have direct correlation with the axis-wise rotations. It is worth mentioning that the fundamental difference between the Euler and Bryant angles lies in a fact that the former represents a sequence of rotations about the same axis separated with a rotation about a different axis, denoted as α–β–α, whereas the latter represents the sequence of rotations about three different axes, denoted as α–β–γ. They are also commonly referred to as symmetric and asymmetric sets of Euler angles in the literature. For convenience, the name Euler angles will be referred to both Euler and Bryant angles, hereafter. © 2013, Springer Science+Business Media Dordrecht.

Euler-Angle-Joints (EAJs)

The paper reviews the cost of different water supply and water treatment options around the world. The cost of supplying ground water is found to be proportional to the lift. The relationship between cost and volume of water treated by specific treatment options is assessed. Vehicular transportation of water is found to be very costly compared to wastewater treatment and compared to conventional water treatment and supply. Efforts have been made to differentiate the cost of water with respect to its application in various sectors. The capital cost of infrastructure required to extract, treat, supply, and reclaim water is also studied. Finally, the effects of precipitation, geographic aspects, population, financial, regulatory laws, and social attributes of a specific region are considered as they affect the cost of water. Global use of water in agriculture and the costs of agricultural irrigation are studied. Pressurized irrigation systems are costlier compared to flood or surface irrigation systems. © 2013 Desalination Publications.

Costs for water supply, treatment, end-use and reclamation

An analysis of the energy budget for the general case of a body translating in a stationary fluid under the action of an external force is used to define a power loss coefficient. This universal definition of power loss coefficient gives a measure of the energy lost in the wake of the translating body and, in general, is applicable to a variety of flow configurations including active drag reduction, self-propulsion and thrust generation. The utility of the power loss coefficient is demonstrated on a model bluff body flow problem concerning a two-dimensional elliptical cylinder in a uniform cross-flow. The upper and lower boundaries of the elliptic cylinder undergo continuous motion due to a prescribed reflectionally symmetric constant tangential surface velocity. It is shown that a decrease in drag resulting from an increase in the strength of tangential surface velocity leads to an initial reduction and eventual rise in the power loss coefficient. A maximum in energetic efficiency is attained for a drag reducing tangential surface velocity which minimizes the power loss coefficient. The effect of the tangential surface velocity on drag reduction and self-propulsion of both bluff and streamlined bodies is explored through a variation in the thickness ratio (ratio of the minor and major axes) of the elliptical cylinders. © 2013 Elsevier Ltd.

Journal of Fluids and Structures

A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications