8,068 research outputs found
Propfan experimental data analysis
A data reduction method, which is consistent with the performance prediction methods used for analysis of new aircraft designs, is defined and compared to the method currently used by NASA using data obtained from an Ames Res. Center 11 foot transonic wind tunnel test. Pressure and flow visualization data from the Ames test for both the powered straight underwing nacelle, and an unpowered contoured overwing nacelle installation is used to determine the flow phenomena present for a wind mounted turboprop installation. The test data is compared to analytic methods, showing the analytic methods to be suitable for design and analysis of new configurations. The data analysis indicated that designs with zero interference drag levels are achieveable with proper wind and nacelle tailoring. A new overwing contoured nacelle design and a modification to the wing leading edge extension for the current wind tunnel model design are evaluated. Hardware constraints of the current model parts prevent obtaining any significant performance improvement due to a modified nacelle contouring. A new aspect ratio wing design for an up outboard rotation turboprop installation is defined, and an advanced contoured nacelle is provided
Using visual analytics to develop situation awareness in astrophysics
We present a novel collaborative visual analytics application for cognitively overloaded users in the astrophysics domain. The system was developed for scientists who need to analyze heterogeneous, complex data under time pressure, and make predictions and time-critical decisions rapidly and correctly under a constant influx of changing data. The Sunfall Data Taking system utilizes several novel visualization and analysis techniques to enable a team of geographically distributed domain specialists to effectively and remotely maneuver a custom-built instrument under challenging operational conditions. Sunfall Data Taking has been in production use for 2 years by a major international astrophysics collaboration (the largest data volume supernova search currently in operation), and has substantially improved the operational efficiency of its users. We describe the system design process by an interdisciplinary team, the system architecture and the results of an informal usability evaluation of the production system by domain experts in the context of Endsley's three levels of situation awareness
Freeform Extrusion of High Solids Loading Ceramic Slurries, Part II: Extrusion Process Control
Part I of this paper provided a detailed description of a novel fabrication machine for high solids
loading ceramic slurry extrusion and presented an empirical model of the ceramic extrusion
process, with ram velocity as the input and extrusion force as the output. A constant force is
desirable in freeform extrusion processes as it correlates with a constant material deposition rate
and, thus, good part quality. The experimental results in Part I demonstrated that a constant ram
velocity will produce a transient extrusion force. In some instances the extrusion force increased
until ram motor skipping occurred. Further, process disturbances, such as air bubble release and
nozzle clogging that cause sudden changes in extrusion force, were often present. In this paper a
feedback controller for the ceramic extrusion process is designed and experimentally
implemented. The controller intelligently adjusts the ram motor velocity to maintain a constant
extrusion force. Since there is tremendous variability in the extrusion process characteristics, an
on-off controller is utilized in this paper. Comparisons are made between parts fabricated with
and without the feedback control. It is demonstrated that the use of the feedback control reduces
the effect of process disturbances (i.e., air bubble release and nozzle clogging) and dramatically
improves part quality.Mechanical Engineerin
Freeform Extrusion of High Solids Loading Ceramic Slurries, Part I: Extrusion Process Modeling
A novel solid freeform fabrication method has been developed for the manufacture of
ceramic-based components in an environmentally friendly fashion. The method is based on the
extrusion of ceramic slurries using water as the binding media. Aluminum oxide (Al2O3) is
currently being used as the part material and solids loading as high as 60 vol. % has been
achieved. This paper describes a manufacturing machine that has been developed for the
extrusion of high solids loading ceramic slurries. A critical component of the machine is the
deposition system, which consists of a syringe, a plunger, a ram actuated by a motor that forces
the plunger down to extrude material, and a load cell to measure the extrusion force. An
empirical, dynamic model of the ceramic extrusion process, where the input is the commanded
ram velocity and the output is the extrusion force, is developed. Several experiments are
conducted and empirical modeling techniques are utilized to construct the dynamic model. The
results demonstrate that the ceramic extrusion process has a very slow dynamic response, as
compared to other non-compressible fluids such as water. A substantial amount of variation
exists in the ceramic extrusion process, most notably in the transient dynamics, and a constant
ram velocity may either produce a relatively constant steady-state extrusion force or it may cause
the extrusion force to steadily increase until the ram motor skips. The ceramic extrusion process
is also subjected to significant disturbances such as air bubble release, which causes a dramatic
decrease in the extrusion force, and nozzle clogging, which causes the extrusion force to slowly
increase until the clog is released or the ram motor skips.Mechanical Engineerin
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