Assessment of casting filling by modeling surface entrainment events using CFD

The reliability of cast components is dependent on the quality of the casting process. During this highly transient filling phase the prevention of free surface turbulence and consequential oxide entrainment is critical to ensure the mechanical integrity of the component. Past research has highlighted a number of events that lead to entrainment of surface oxides. Using FLOW-3D, flow structures that result in surface entrainment events have been simulated and an algorithm developed that allows entrainment and defect motion to be tracked. This enables prediction of the quantity and motion of oxide film generated from each event. The algorithm was tested experimentally and compared to experimental data from previously published work. A quantitative criterion is proposed to assess the damage of each type of event. Complete running systems have also been studied to understand how they could be assessed for quality of filling based on the flows within them

The modelling of oxide film entrainment in casting systems using computational modelling

As Campbell stated in 2006, “the use of entrainment models to optimise filling systems designs for castings has huge commercial potential that has so far being neglected by modellers”. In this paper a methodology using computational modelling to define entraining events and track the entrained oxide films is presented. Research has shown that these oxide films present within the casting volume are highly detrimental to casting integrity, thus their entrainment during mould filling is especially undesirable. The method developed for the modelling of oxide entrainment has been validated against previously published data by Green and Campbell (1994) [31]. The validation shows good quantitative correlation with experimental data. However there is scope for further development which has the potential to both improve the accuracy and further validate the technique

Single-channel digital command-detection system

System, fabricated of highly-reliable digital logic elements, operates on binary pulse-code-modulated signals and derives internal synchronization from data signal. All-digital implementation of detector develops synchronization from data signal by computer cross-correlation of command modulation signal with its expected forms in sequence and adjusts detector phases in accordance with correlation peaks

Helicopter noise research at the Langley V/STOL tunnel

The noise generated from a 1/4-scale AH-1G helicopter configuration was investigated in the Langley V/STOL tunnel. Microphones were installed in positions scaled to those for which flight test data were available. Model and tunnel conditions were carefully set to properly scaled flight conditions. Data presented indicate a high degree of similarity between model and flight test results. It was found that the pressure time history waveforms are very much alike in shape and amplitude. Blade slap when it occurred seemed to be generated in about the same location in the rotor disk as on the flight vehicle. If model and tunnel conditions were properly matched, including inflow turbulence characteristics, the intensity of the blade-slap impulse seemed to correlate well with flight

Method and apparatus for a single channel digital communications system

A method and apparatus are described for synchronizing a received PCM communications signal without requiring a separate synchronizing channel. The technique provides digital correlation of the received signal with a reference signal, first with its unmodulated subcarrier and then with a bit sync code modulated subcarrier, where the code sequence length is equal in duration to each data bit

Four-quark flux distribution and binding in lattice SU(2)

The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU(2) field theory at separations up to 1 fm at beta=2.4. The four-quark case is equivalent to a qbar q qbar q system in SU(2) and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results.Comment: 46 pages including 71 eps figures. 3D color figures are available at www.physics.helsinki.fi/~ppennane/pics

Length-length and weight-length relationships of seven deep-water fishes in the Gulf of Mexico

Regression coefficients for equations of the form Y = a + bX were estimated for total length (TL) and whole weight (W) as a function of standard length (SL) and fork length (FL) and vice versa for seven deep-water fishes. All lengths were measured in millimeters and all weights in grams. There was a significant correlation between weight and length and the types of length measurements for all species. However, the amount of variation explained by each regression varied among species. Weight-length regressions were less precise than length-length regression, as they generally are, because weights of small fish measured at sea are more inaccurate than those of large fish.Marine Scienc