Computation of the tip vortex flowfield for advanced aircraft propellers

The tip vortex flowfield plays a significant role in the performance of advanced aircraft propellers. The flowfield in the tip region is complex, three-dimensional and viscous with large secondary velocities. An analysis is presented using an approximate set of equations which contains the physics required by the tip vortex flowfield, but which does not require the resources of the full Navier-Stokes equations. A computer code was developed to predict the tip vortex flowfield of advanced aircraft propellers. A grid generation package was developed to allow specification of a variety of advanced aircraft propeller shapes. Calculations of the tip vortex generation on an SR3 type blade at high Reynolds numbers were made using this code and a parametric study was performed to show the effect of tip thickness on tip vortex intensity. In addition, calculations of the tip vortex generation on a NACA 0012 type blade were made, including the flowfield downstream of the blade trailing edge. Comparison of flowfield calculations with experimental data from an F4 blade was made. A user's manual was also prepared for the computer code (NASA CR-182178)

User's manual for PEPSIG NASA tip vortex version

The tip vortex flowfield plays a significant role in the performance of advanced aircraft propellers. The flowfield in the tip region is complex, three-dimensional and viscous with large secondary velocities. A computer code was developed to predict the tip vortex flowfield of advanced aircraft propellers. This document is the user's manual. The analysis and a series of test cases are presented in NASA-CR-182179

The Posthuman Reality of Feed-Based Social Media Systems

The conceptual boundary between the subject and user parallels the boundary between humanist and posthumanist definitions of human being, and the challenges of new media communications technology today impel this evolution. My dissertation discusses subjectivity as the self-differentiation of a particular set of processes, and the influence of communications media upon this process. Here, it includes the basis of differentiation for an I, including: the question of identity, potential agency, and knowledge. The collage of attributes that constitute a portrait of what I call the user, the subject of online social media, is demonstrably emergent, dispersed, and discursive; in terms of agency and sovereignty, the useras with other instances of posthuman subjectivityis contingent upon its media ecology and is decidedly less free than other definitions of subjectivity (such the self-sovereign individual of the social contract, which comes to be as a negation of contingency). The concept of self-sovereignty excludes the influences of history, and other influences upon the emergence of the subject, emphasizing an exclusively internal causation. The users existence, conversely, is processual and dispersed throughout networks; its being and agency are dividual, not individual. The subjectivity of the user must thus be thought in terms of its mediated contingency, as the self-sovereign agency that is characteristic of humanist traditions is less applicable to todays media ecologies. I argue that the traits of the subject in humanist traditions can be interpreted as the epiphenomena of societies whose information ecology was dominated by logocentric, typographic literacy. Today, with the advent of social media and its users, we can understand from a new vantage how subjectivities are modulated, amplified, and attenuated by technical distributions, particularly the unseen (and unseeable) non-human agents in the computation systems that constitute online social networks

Canon Fodder in the Institutional Vessel : The Missing Voice of the Student in Literary Canon and Curriculum Discourse

Are graduate students\u27 part of the “canon wars,” which have been waged among scholars and institutions for more than twenty years to determine what should remain part of the literary canon and therefore part of the curriculum; or are graduate students merely “canon fodder”? My research attempts to define the canon, then examines whether scholar-critics or academic institutions have listened to the voice of the students regarding the creation and continued teaching of the canon, and finally explores the chasm between the “accessible” and “selective” canon. I ask whether any pedagogical approach values the student when implementing the canon through the required readings. What happens when graduate students are granted authority in this conversation? Few teachers seem willing to make the leap from rhetoric to practical application; however, research demonstrates that giving students choices about what they read adds to a culture of empowerment and enthusiasm in the classroom. A student-influenced approach to the “canon wars” will not only make sense of the war, but also provide a context for future study and what it means for the canon and curricula to enter the student into the fray as more than mere “canon fodder.

Elastoplastic solutions to predict tunnelling-induced load redistribution and deformation of surface structures

In this paper, an elastoplastic two-stage analysis method is proposed to model tunnelling-induced soil-structure interaction and incorporated into a computer program `ASRE'. This solution allows considering both vertical and horizontal greenfield ground movements, gap formation and slippage, continuous or isolated foundations, and a variety of structural configurations and loading conditions. After introducing the proposed formulation, the model predictions are first compared with previously published data for validation. Then, to isolate the effects of various structural characteristics (relative beam-column stiffness, presence of a ground level slab, column height, number of storeys) and foundation types (continuous versus isolated), several example structures are analysed. Results demonstrate the value of the proposed analysis method to study a broad range of building characteristics very quickly, and show how the soil-structure interaction occurring due to underground excavations is altered by both foundation and superstructure configurations. In particular, the difference in behaviour between equivalent simple beams and framed structures on separated footings is clarified.Engineering and Physical Sciences Research Counci

An Interactive Tool for Discrete Phase Analysis in Two-Phase Flows

Under a NASA MSFC SBIR Phase 1 effort an interactive software package has been developed for the analysis of discrete (particulate) phase dynamics in two-phase flows in which the discrete phase does not significantly affect the continuous phase. This package contains a Graphical User Interface (based on the X Window system and the Motif tool kit) coupled to a particle tracing program, which allows the user to interactively set up and run a case for which a continuous phase grid and flow field are available. The software has been applied to a solid rocket motor problem, to demonstrate its ease of use and its suitability for problems of engineering interest, and has been delivered to NASA Marshall Space Flight Center

Incorporating the Impact of Engineering Solutions on Society into Technical Engineering Courses

In the era of market and workforce globalisation, engineers need a solid understanding of the impact that their products have locally, as well as globally. This is why the US Accreditation Board for Engineering and Technology (ABET) recently put a new spin on this requirement in engineering education. Specifically, outcome 3h of Engineering Criteria 2000 states that engineering graduates must have the broad education to understand the impact of engineering solutions in a global/ societal context. This outcome may be one of the most difficult to achieve, since it requires not only a strong technical understanding, but also an informed societal and historical perspective that is particularly difficult to achieve. In this paper, the authors identify some of the skills that engineering students need to be able to evaluate the impact of their solutions in a global/societal context, as well as the methods used by some universities to address this issue outside of technical engineering courses. The main focus of this article is the introduction of course design elements that help students to master those skills that can be incorporated into required and elective engineering courses. Examples are presented from a variety of thermal/fluid courses where these skills are taught in the Mechanical and Aerospace Engineering Department at San José State University, San José, USA

Open-Ended Problem-Solving Skills in Thermal-Fluids Engineering

Problem-solving skills have always been important in many professions. However, ABET EC 2000 recently placed a new focus on these skills in engineering education with outcome 3e, which states that engineering graduates must have an ability to identify, formulate and solve engineering problems. Problem-solving is defined as a process used to obtain a best answer to an unknown or a decision that is subject to some constraints. Problem-solving is not the same as textbook exercise solving, which is very common in engineering curricula. In the article, the authors first define engineering problem-solving and, in particular, what it means to identify and formulate a problem. This definition will set the stage for identifying the skills that students need to acquire and the attributes they must possess in order to be classified as competent problem solvers. Next, the authors introduce sample problems that help students to master these skills. Finally, the data gathered regarding student performance in these types of problems is presented and analysed

Navier-Stokes analysis of an oxidizer turbine blade with tip clearance with and without a mini-shroud

The Gas Generator Oxidizer Turbine (GGOT) Blade is being analyzed by various investigators under the NASA MSFC-sponsored Turbine Stage Technology Team design effort. The present work concentrates on the tip clearance region flow and associated losses; however, flow details for the passage region are also obtained in the simulations. The present calculations simulate the rotor blade row in a rotating reference frame with the appropriate coriolis and centrifugal acceleration term included in the momentum equations. The upstream computational boundary is located about one axial chord from the blade leading edge. The boundary conditions at this location have been determined by Pratt & Whitney using an Euler analysis without the vanes to obtain approximately the same flow profiles at the rotor as were obtained with the Euler stage analysis including the vanes. Inflow boundary layer profiles are then constructed assuming the skin friction coefficient at both the hub and the casing. The downstream computational boundary is located about one axial chord from the blade trailing edge, and the circumferentially averaged static pressure at this location was also obtained from the P&W Euler analysis. Results obtained for the 3-D baseline GGOT geometry at the full scale design Reynolds number show a region of high loss in the region near the casing. Particle traces in the near tip region show vortical flow behavior of the fluid which passes through the clearance region and exits at the downstream edge of the gap. In an effort to reduce clearance flow losses, the mini-shroud concept was proposed by the Pratt & Whitney design team. Calculations were performed on the GGO geometry with the mini-shroud. Results of these calculations indicate that the mini-shroud does not significantly affect the flow in the passage region, and although the tip clearance flow is different, the mini-shroud does not seem to prevent the above-mentioned vortical flow behavior. Since both flow distortion and total pressure losses are similar for both geometries, the addition of the mini-shroud does not seem to reduce the tip clearance flow effects

A controlled migration genetic algorithm operator for hardware-in-the-loop experimentation

In this paper, we describe the development of an extended migration operator, which combats the negative effects of noise on the effective search capabilities of genetic algorithms. The research is motivated by the need to minimize the num- ber of evaluations during hardware-in-the-loop experimentation, which can carry a significant cost penalty in terms of time or financial expense. The authors build on previous research, where convergence for search methods such as Simulated Annealing and Variable Neighbourhood search was accelerated by the implementation of an adaptive decision support operator. This methodology was found to be effective in searching noisy data surfaces. Providing that noise is not too significant, Genetic Al- gorithms can prove even more effective guiding experimentation. It will be shown that with the introduction of a Controlled Migration operator into the GA heuristic, data, which repre- sents a significant signal-to-noise ratio, can be searched with significant beneficial effects on the efficiency of hardware-in-the- loop experimentation, without a priori parameter tuning. The method is tested on an engine-in-the-loop experimental example, and shown to bring significant performance benefits