Externally blown flap impingement parameters

The performance of two externally blown flap (EBF) wind tunnel models was compared with an engine exhaust flap impingement correlation parameter. One model was a four engine EBF triple slotted flap transport. Isolated engine wake surveys were conducted to define the wake properties of five separate engine configurations for which performance data were available. The other model was a two engine EBF transport for which the engine wake properties were estimated. The correlation parameter was a function of engine exhaust dynamic pressure at the flap location, area of engine exhaust flap impingement, total exhaust area at the flap location, and engine thrust. The distribution of dynamic pressure for the first model was measured; however, the distribution for the second model was assumed to be uniform

Rotor induced-inflow-ratio measurements and CAMRAD calculations

Comparison of the inflow calculations between an analytical rotor wake method and rotor inflow measurements using a laser velocimeter was presented. The inflow measurements were made near a 4-bladed rotor system using rectangular planform blades operating in forward flight at a thrust coefficient of 0.0064, and at 3 rotor advance ratios: 0.15, 0.23, and 0.30. The inflow measurements were made at azimuthal increments of 30 degrees at 3.0 inches (approximately 1 chord) above the plane formed by the tips of the blades, and radial locations from 20 to 110 percent of blade span. The experimental measurements showed that as the advance ratio (m) increased, the induced upflow region moved progressively from the forward 20 percent of the rotor disc at m = 0.15 to covering most of the forward half of the rotor disc at m = 0.30. The induced inflow characteristics at all advance ratios were found to be unsymmetrical about the longitudinal centerline. The maximum downwash was found to be in the rear portion of the disc and skewed toward the advancing blade side. The comparisons with the analytical method Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD) show that the region of induced upflow over the rotor disc was effectively modeled only at the advance ratio of 0.15. The method consistently indicated the largest values of induced inflow ratio to be on the retreating-blade side of the rotor disc (opposite from that measured). The importance of the choice of rotor trim option is examined and results of two trim selections are detailed

Reduction of high-speed impulsive noise by blade planform modification of a model helicopter rotor

The reduction of high speed impulsive noise for the UH-1H helicopter was investigated by using an advanced main rotor system. The advanced rotor system had a tapered blade planform compared with the rectangular planform of the standard rotor system. Models of both the advanced main rotor system and the UH-1H standard main rotor system were tested at 1/4 scale in the 4 by 7 Meter Tunnel. In plane acoustic measurements of the high speed impulsive noise demonstrated that the advanced rotor system on the UH-1H helicopter reduced the high speed impulsive noise by up to 20 dB, with a reduction in overall sound pressure level of up to 5 dB

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

Longitudinal aerodynamics of a low-wing lift-fan transport including hover characteristics in and out of ground effect

A wind-tunnel investigation was conducted in the Langley V/STOL tunnel to determine the longitudinal aerodynamic characteristics of a six-fan, tip-driven (remote) lift-fan VTOL transport throughout transition. The large midspan lift-fan pods and cruise fans were removed to determine their influence on the stability and control of the configuration. Data were obtained in the hovering mode for ranges of model height above ground. The data are presented without analysis or discussion

Rotor performance characteristics from an aeroacoustic helicopter wind-tunnel test program

An investigation of helicopter rotor noise at model scale was conducted in the Langley 4 by 7 meter tunnel. The program described was the first of a planned three-phase project whose purpose was to examine the characteristic noise mechanism involved in main rotor/tail rotor interaction noise. This first phase was conducted with a main rotor only, in order to identify the characteristic noise generated by only the main rotor. The aerodynamic operating conditions of the rotor system were defined during the test. The acoustic data were properly referenced

A laser velocimeter flow survey above a stalled wing

A laser velocimeter operating in the backscatter mode was used to survey the flow about a stalled wing installed in the Langley V/STOL tunnel. Mean velocities and magnitudes of velocity fluctuations were calculated from measurements of two orthogonal components of velocity. Free shear mixing layers above and below a large separated flow region were defined. Velocity power spectra were calculated at two points in the flow field. The flow-field survey was carried out about a rectangular aspect-ratio-8 wing with an airfoil section. The wing angle of attack was 19.4 deg, the Mach number was 0.148, and the nominal Reynolds number was 1 x 1 million

Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study

Background: It is well documented that exercise-induced muscle damage (EIMD) decreases muscle function and causes soreness and discomfort. Branched-chain amino acid (BCAA) supplementation has been shown to increase protein synthesis and decrease muscle protein breakdown, however, the effects of BCAAs on recovery from damaging resistance training are unclear. Therefore, the aim of this study was to examine the effects of a BCAA supplementation on markers of muscle damage elicited via a sport specific bout of damaging exercise in trained volunteers. Methods: Twelve males (mean ± SD age, 23 ± 2 y; stature, 178.3 ± 3.6 cm and body mass, 79.6 ± 8.4 kg) were randomly assigned to a supplement (n = 6) or placebo (n = 6) group. The damaging exercise consisted of 100 consecutive drop-jumps. Creatine kinase (CK), maximal voluntary contraction (MVC), muscle soreness (DOMS), vertical jump (VJ), thigh circumference (TC) and calf circumference (CC) were measured as markers of muscle damage. All variables were measured immediately before the damaging exercise and at 24, 48, 72 and 96 h post-exercise. Results: A significant time effect was seen for all variables. There were significant group effects showing a reduction in CK efflux and muscle soreness in the BCAA group compared to the placebo (P < 0.05). Furthermore, the recovery of MVC was greater in the BCAA group (P < 0.05). The VJ, TC and CC were not different between groups. Conclusion: The present study has shown that BCAA administered before and following damaging resistance exercise reduces indices of muscle damage and accelerates recovery in resistance-trained males. It seems likely that BCAA provided greater bioavailablity of substrate to improve protein synthesis and thereby the extent of secondary muscle damage associated with strenuous resistance exercise. Clinical Trial Registration Number: NCT01529281

League tables for literacy survey data based on random effect models.

Data from the International Adult Literacy Survey are used to illustrate how league tables can be obtained from summary data, consisting of percentages and their standard errors, using random effects models estimated by nonparametric maximum likelihood