Non-singular orbital elements for special perturbations in the two-body problem

Seven spatial elements and a time element are proposed as the state variables of a new special perturbation method for the two-body problem. The new elements hold for zero eccentricity and inclination and for negative values of the total energy. They are developed by combining a spatial transformation into projective coordinates (as in the Burdet–Ferrándiz regularization) with a time transformation in which the exponent of the orbital radius is equal to one instead of two (as commonly done in the literature). By following this approach, we discover a new linearization of the two-body problem, from which the orbital elements can be generated by the variation of parameters method. The geometrical significance of the spatial quantities is revealed by a new intermediate frame which differs from a local vertical local horizontal frame by one rotation in the instantaneous orbital plane. Four elements parametrize the attitude in space of this frame, which in turn defines the orientation of the orbital plane and fixes the departure direction for the longitude of the propagated body. The remaining three elements determine the motion along the radial unit vector and the orbital longitude. The performance of the method, tested using a series of benchmark orbit propagation scenarios, is extremely good when compared to several regularized formulations, some of which have been modified and improved here for the first time

Computational Fluid Dynamics (CFD) Picture of Water Droplet Evaporation in Air

The study of droplet evaporation is applied to many and varied fields: the present approach is oriented to sprinkler irrigation. This paper examines a parametric study on the evaporation in air of a single droplet, with the aim of highlighting the influence of each parameter alone on the evaporative process. Four parameters are investigated:air temperature, droplet initial velocity, droplet initial diameter, diffusion coefficient of vapour in air. Droplet evaporation is studied through numerical-CFD simulation employing STAR-CCM+ version 5.04.012 software, which treats the evaporative phenomenon hypothesizing quasi-steady conditions, given the interface low liquid-gas vapour concentration gradients. The results are provided as time- and space-dependent in-percentage evaporation rates, the latter ones after defining a specific distance, from the injection point, to be covered. Apart from a qualitatively predictable effect of air temperature and diffusion coefficient of vapour in air, droplet initial velocity and above all droplet initial diameter prove not at all to be negligible when managing an irrigation process, the latter being inversely proportional to droplet mass evaporation. These results prove that droplet evaporation is a complicate fluid dynamic effect and cannot be simply regarded as a diffusive process. The final discussion provides some practical remarks useful to irrigation operators

Shared Interests In Live Case-Based Learning – Students’ Dynamic Role In An Innovation Ecosystem

Teaching engineering students to navigate complex innovation ecosystems and deal with wicked problems is vital for contributing to sustainable development. Research shows that case-based learning with real-life challenges boosts motivation and learning outcomes. This paper presents a course that is in the core of an ecosystem where engineering students engage with hospitals, and work on the hospitals’ documented innovation needs. By design, the course setup has a double purpose: in a learning context, the course strengthens intrapreneurship education, with students acting in an empowered role like professional consultants. In an organizational context, the course enhances knowledge sharing, filling in the gap of innovation competences and resources needed to create value and stimulate intrapreneurial initiatives. The ecosystem has evolved as result of an iterated development of the course including the tools and frameworks that empower the students to act as autonomous innovation consultants in constant interaction with the process of mobilizing the case partners. Thus, this paper presents a study based on current experiences and learnings, focusing on the relationship between the facilitation of student empowerment in live case-based learning and the impact on both 1) engineering students’ motivation and learning outcomes; 2) value creation for the participating ecosystem. The paper builds on qualitative data from two sources: yearly follow-up interviews with case partners since 2018, and student reflection reports from 2022

Development of an Experimental/Numerical Validation Methodology for the Design of Exhaust Manifolds of High Performance Internal Combustion Engines

Several typical failure modes in the exhaust manifold of an internal combustion engine are commented on. In particular, thermal loading and the related thermal fatigue damage mechanism are addressed. The component under investigation is a cast exhaust manifold including the turbine involute. Finite Element simulations are performed, and a numerical methodology is presented to interpret and understand the observed failures, with the aim of developing a useful tool to virtually validate the component, before the manufacturing phase. The Finite Element analysis closely mimics the experimental validation procedure that considers several heating and rapid cooling cycles to simulate typical engine operating conditions. A static mechanical characterization at high temperatures of the materials involved is carried out, aimed at identifying a suitable alloy and its mechanical characteristics useful for feeding the numerical models. The developed design methodology proposes a damage criterion for thermal fatigue investigation, considering the elastoplastic behaviour of the material when subjected to high temperature cycles. In particular, the accumulated equivalent plastic strain range for a single thermal cycle (ΔPEEQ) is used, following the Ferrari expertise. The methodology appears to be well correlated with the experimental evidence, thus limiting the number of tests necessary for the approval of the component

EFFECTS OF ROTATION ON UNSTEADY FLUID FLOW AND FORCED CONVECTION IN THE ROTATING CURVED SQUARE DUCT WITH A SMALL CURVATURE

In recent years, the analysis of flow disposition in a curved duct (CD) has greatly attracted researchers because it is broadly used in engineering devices. In the present paper, unsteady flow characteristics of energy transfer (HT) in a rotating curved square duct (CSD) have been presented with the aid of spectral method. The key purpose of this study is to explore rotational effects and heat transfer (HT) of the duct. For this purpose, time-evolution calculation is performed over the Taylor number (-1500 ≤ Tr ≤ 1500) and other parameters are fixed; e.g., Dean number (Dn = 1000), Curvature (δ = 0.015) and Prandtl number (Pr = 7.0, for water). Firstly, time-dependent behavior is accomplished for both clockwise and anticlockwise rotations. It is found that the flow instabilities are certainly governed by the change of Tr that has been justified by sketching phase spaces (PS). To observe the flow features, velocities including axial flow (AF), secondary flow (SF) and temperature profiles are disclosed for both rotations; and it is elucidated that 2- to 6-vortex solutions are generated for physically realizable solutions. Axial flow (AF) shows that two maximum-velocity regimes are produced which induces secondary flow (SF), and, consequently, a strong bonding between the AF and SF has been built up. It is observed that as the rotation is increased, the fluid is mixed considerably which boosts HT in the fluid. Finally, an assessment between the numerical and experimental data has been given, and a good agreement is observed

Markov-based performance evaluation and availability optimization of the boiler–furnace system in coal-fired thermal power plant using PSO

The appropriate maintenance strategy is essential for maintaining the thermal power plant highly reliable. The thermal power plant is a complex system that consists of various subsystems connected either in series or parallel configuration. The boiler–furnace (BF) system is one of the most critical subsystems of the thermal power plant. This paper presents availability based simulation modeling of the boiler–furnace system of thermal power plant with capacity (500MW). The Markov based simulation model of the system is developed for performance analysis. The differential equations are derived from a transition diagram representing various states with full working capacity, reduced capacity, and failed state. The normalizing condition is used for solving the differential equations. Furthermore, the performance of the system is analyzed for a possible combination of failure rate and repair rate, which revealed that failure of the boiler drum affects the system availability at most, and the failure of reheater affects the availability at least. Based on the criticality ranking, the maintenance priority has been provided for the system.The availability of the boiler–furnace system is optimized using particle swarm optimization method by varying the number of particles. The study results revealed that the maximum system availability level of 99.9845% is obtained. In addition, the optimized failure rate and repair rate parameters of the subsystem are used for suggesting an appropriate maintenance strategy for the boiler–furnace system of the plant. The finding of the study assisted the decision-makers in planning the maintenance activity as per the criticality level of subsystems for allocating the resources

A Variational Method for the Propagation of Spacecraft Relative Motion.

A new formulation of the spacecraft relative motion for a generic orbit is presented based on the orbital propagation method proposed by Peláez et al. in 2006 [1]. Two models have been developed. In the first model the method is applied to each spacecraft using a time synchronization of the system dynamical states. In the second model we employ a local orbital reference frame with a linearization of gravitational terms, apply the method to the formation center of mass and propagate the relative dynamics with respect to the center of mass reference orbit. The models are compared in terms of computational speed for the case of a bounded triangular formatio

food production and irrigation and drainage systems development perspective and challenges

A critical problem challenging mankind today is how to manage the intensifying competition for water between expanding urban centres, traditional agricultural activities and in-stream water uses dictated by environmental concerns. In the agricultural sector, the prospects of increasing the gross cultivated area are limited by the dwindling number of economically attractive sites for large-scale irrigation and drainage projects. Therefore the required increase in agricultural production will necessarily rely largely on the affordability to apply new technologies, a more accurate estimation of crop water requirements, and on major improvements in the construction, operation, management and performance of existing irrigation and drainage systems. The failings of present systems and the inability to sustainably exploit surface and groundwater resources can be attributed essentially to poor planning, design, system management and development. This is partly due to the inability of engineers, planners and managers to adequately quantify the effects of irrigation and drainage projects on water resource systems and to use these effects as guidelines for improving technology, design and management [1-4]