Computer analysis of flow perturbations generated by placement of choke bumps in a wind tunnel

An inviscid analytical study was conducted to determine the upstream flow perturbations caused by placing choke bumps in a wind tunnel. A computer program based on the stream-tube curvature method was used to calculate the resulting flow fields for a nominal free-stream Mach number range of 0.6 to 0.9. The choke bump geometry was also varied to investigate the effect of bump shape on the disturbance produced. Results from the study indicate that a region of significant variation from the free-stream conditions exists upstream of the throat of the tunnel. The extent of the disturbance region was, as a rule, dependent on Mach number and the geometry of the choke bump. In general, the upstream disturbance distance decreased for increasing nominal free-stream Mach number and for decreasing length-to-height ratio of the bump. A polynomial-curve choke bump usually produced less of a disturbance than did a circular-arc bump and going to an axisymmetric configuration (modeling choke bumps on all the tunnel walls) generally resulted in a lower disturbance than with the corresponding two dimensional case

Time division radio relay synchronizing system using different sync code words for in sync and out of sync conditions Patent

Time division relay synchronizer with master sync pulse for activating binary counter to produce signal identifying time slot for statio

Full-scale testing of an Ogee tip rotor

Full scale tests were utilized to investigate the effect of the ogee tip on helicopter rotor acoustics, performance, and loads. Two facilities were used: the Langley whirl tower and a UH-1H helicopter. The text matrix for hover on the whirl tower involved thrust values from 0 to 44 480 N (10,000 lb) at several tip Mach numbers for both standard and Ogee rotors. The full scale testing on the UH-1H encompassed the major portion of the flight envelope for that aircraft. Both near field acoustic measurements and far field flyover data were obtained for both the ogee and standard rotors. Data analysis of the whirl tower test shows that the ogee tip does significantly diffuse the tip vortex while providing some improvement in hover performance at low and moderate thrust coefficients. Flight testing of both rotors indicates that the strong impulsive noise signature of the standard rotor can be reduced with the ogee rotor. Analysis of the spectra indicates a reduction in energy in the 250 Hz and 1000 Hz range for the ogee rotor. Forward flight performance was significantly improved with the ogee configuration for a large number of flight conditions. Further, rotor control loads were reduced through use of this advanced tip rotor

The Dynamics of Emerging Market Equity Flows

We study the interrelationship between capital flows, returns, dividend yields and world interest rates in 20 emerging markets. We estimate a vector autoregressionn with these variables to measure the degree to which lower interest rates contribute to increased capital flows and shocks in flows affect the cost of capital among other dynamic relations. We precede the VAR analysis by a detailed examination of endogenous break points in capital flows and the other variables. These structural breaks are traced to the liberalization of emerging equity markets. Our evidence of structural breaks call into question past research which estimates VAR models over the full sample. After a liberalization, we find that equity flows increase by 1.4% of market capitalization. We also show that shocks in equity flows initially increase returns which is consistent with a price pressure hypothesis. While the effect is diminished over time, there also appears to be a permenant impact. This is consistent with our finding that our proxy for the cost of capital, dividend yields, decreases. Finally, our analysis of the transitition dynamics from pre-liberalization to post-liberalization suggests that when capital leaves, it leaves faster than it came in. These results may help us understand the dynamics of the recent crises in Latin America and East Asia.

Porcine Malignant Edema

On Dec. 23, 1940, near Brookfield, Mo., an outbreak of malignant edema in a herd of swine was observed. According to the owner 20 hogs developed clinical symptoms within 36 hours following his detection of the first sick animal. After this period no other affected animals appeared. A fox terrier dog known to have eaten a jowl from an infected carcass developed typical malignant edma symptoms within three days and died within a week

Revisiting the 1954 Suspension Experiments of R. A.Bagnold

In 1954 R. A. Bagnold published his seminal findings on the rheological properties of a liquid-solid suspension. Although this work has been cited extensively over the last fifty years, there has not been a critical review of the experiments. The purpose of this study is to examine the work and to suggest an alternative reason for the experimental findings. The concentric cylinder rheometer was designed to measure simultaneously the shear and normal forces for a wide range of solid concentrations, fluid viscosities and shear rates. As presented by Bagnold, the analysis and experiments demonstrated that the shear and normal forces depended linearly on the shear rate in the 'macroviscous' regime; as the grain-to-grain interactions increased in the 'grain-inertia' regime, the stresses depended on the square of the shear rate and were independent of the fluid viscosity. These results, however, appear to be dictated by the design of the experimental facility. In Bagnold's experiments, the height (h) of the rheometer was relatively short compared to the spacing (t) between the rotating outer and stationary inner cylinder (h/t=4.6). Since the top and bottom end plates rotated with the outer cylinder, the flow contained two axisymmetric counter-rotating cells in which flow moved outward along the end plates and inward through the central region of the annulus. At higher Reynolds numbers, these cells contributed significantly to the measured torque, as demonstrated by comparing Bagnold's pure-fluid measurements with studies on laminar-to-turbulent transitions that pre-date the 1954 study. By accounting for the torque along the end walls, Bagnold's shear stress measurements can be estimated by modelling the liquid-solid mixture as a Newtonian fluid with a corrected viscosity that depends on the solids concentration. An analysis of the normal stress measurements was problematic because the gross measurements were not reported and could not be obtained

Aerodynamic design for improved manueverability by use of three-dimensional transonic theory

Improvements in transonic maneuver performance by the use of three-dimensional transonic theory and a transonic design procedure were examined. The FLO-27 code of Jameson and Caughey was used to design a new wing for a fighter configuration with lower drag at transonic maneuver conditions. The wing airfoil sections were altered to reduce the upper-surface shock strength by means of a design procedure which is based on the iterative application of the FLO-27 code. The plan form of the fighter configuration was fixed and had a leading edge sweep of 45 deg and an aspect ratio of 3.28. Wind-tunnel tests were conducted on this configuration at Mach numbers from 0.60 to 0.95 and angles of attack from -2 deg to 17 deg. The transonic maneuver performance of this configuration was evaluated by comparison with a wing designed by empirical methods and a wing designed primarily by two-dimensional transonic theory. The configuration designed by the use of FLO-27 had the same or lower drag than the empirical wing and, for some conditions, lower drag than the two-dimensional design. From some maneuver conditions, the drag of the two-dimensional design was somewhat lower

A real-time PCR method for quantification of the total and major variant strains of the Deformed wing virus

Funding: ELB was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) EASTBIO Doctoral Training Partnership (http://www.bbsrc.ac.uk) [grant number BB/J01446X/1] and an Eastern Association Regional Studentship (EARS) and The Morley Agricultural Foundation awarded to ASB. CRC was supported by a KTN BBSRC CASE studentship (BB/M503526/1) (http://www.bbsrc.ac.uk), part-funded by the Scottish Beekeeping Association (https://www.scottishbeekeepers.org.uk/) and the Animal Health - Disease Prevention, Scottish Government awarded to ASB CRC. This project received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 613960 (SMARTBEES) (http://www.smartbees-fp7.eu/) awarded to ASB. The funders had no role in study design, data collection and analysis decision to publish, or preparation of the manuscript. Acknowledgments The authors wish to thank Mr W. Thrale, Mr Z. Blackmore, Mr J. Quinlan, and Mr J. Palombo for sample collection from the South East of England and Margie Ramsey for Beinn Eighe National Nature Reserve sample collection.Peer reviewedPublisher PD