Engineering Papers⌕ Search

Engineering topics

Tauber, M. E.

Publications and source records attributed to Tauber, M. E..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Measurement and prediction of model-rotor flow fields

This paper shows that a laser velocimeter can be used to measure accurately the three-component velocities induced by a model rotor at transonic tip speeds. The measurements, which were made at Mach numbers from 0.85 to 0.95 and at zero advance ratio, yielded high-resolution, orthogonal velocity values. The measured velocities were used to check the ability of the ROT22 full-potential rotor code to predict accurately the transonic flow field in the crucial region around and beyond the tip of a high-speed rotor blade. The good agreement between the calculated and measured velocities established the code's ability to predict the off-blade flow field at transonic tip speeds. This supplements previous comparisons in which surface pressures were shown to be well predicted on two different tips at advance ratios to 0.45, especially at the critical 90 deg azimuthal blade position. These results demonstrate that the ROT22 code can be used with confidence to predict the important tip-region flow field, including the occurrence, strength, and location of shock waves causing high drag and noise.

Owen, F. K.↗
NASA NTRS1984

Computerized aerodynamic design of a transonically 'quiet' blade

The high noise levels produced by helicopters are major sources of concern. There are many sources of the noise, but during high-speed forward flight, impulsive noise dominates the noise spectrum. The cause of the high-speed impulsive noise is the propagation into the far field of shock waves that form on the advancing blade. This mechanism has been labeled 'delocalization'. It has been shown, however, that by judicious design of the blade-tip planform, delocalization can be prevented. The objective of the present study is to illustrate how blade-tip configurations (both planform and airfoil shape) can be systematically varied to identify shapes that avoid delocalization and simultaneously improve aerodynamic performance. This has been done using the latest version of the ROT22 transonic, full-potential, quasi-steady, rotor flow-field code. A hypothetical modern rotor blade was postulated, and tip modifications consisting of taper, sweep, and airfoil section alterations were investigated. Planform modifications were found to be most effective in eliminating delocalization.

Tauber, M. E.↗
NASA NTRS1983

Comparison of calculated and measured pressures on straight and swept-tip model rotor blades

Using the quasi-steady, full potential code, ROT22, pressures were calculated on straight and swept tip model helicopter rotor blades at advance ratios of 0.40 and 0.45, and into the transonic tip speed range. The calculated pressures were compared with values measured in the tip regions of the model blades. Good agreement was found over a wide range of azimuth angles when the shocks on the blade were not too strong. However, strong shocks persisted longer than predicted by ROT22 when the blade was in the second quadrant. Since the unsteady flow effects present at high advance ratios primarily affect shock waves, the underprediction of shock strengths is attributed to the simplifying, quasi-steady, assumption made in ROT22.

Tauber, M. E.↗
NASA NTRS1982

Aerodynamic predictions II

The development of technology to aid in the design of advanced rotor blades to improve both aerodynamic and acoustic performance is discussed. The development of advanced computer codes to calculate the subsonic and transonic flow field about rotor blades and to model such high noise producing phenomena as shock waves and blade/vortex interaction is examined. The codes are verified by comparison with experimental data. Making the codes available to industry and to provide some training for the industrial users is emphasized.

Tauber, M. E.↗
NASA NTRS1980

Computerized three-dimensional aerodynamic design of a lifting rotor blade

A three-dimensional, inviscid, full-potential lifting rotor code was used to demonstrate that pressure distributions on both advancing and retreating blades could be significantly improved by perturbing local airfoil sections. The perturbations were described by simple geometric shape functions. To illustrate the procedure, an example calculation was made at a forward flight speed of 85 m/sec (165 knots) and an advance ratio of 0.385. It was found that a minimum of three shape functions was required to improve the pressures without producing undesirable secondary effects in high-speed forward flight on a hypothetical modern rotor blade initially having an NLR-1 supercritical airfoil. Reductions in the shock strength on the advancing blade could be achieved, while simultaneously lessening leading-edge pressure gradients on the retreating blade. The major blade section modifications required were blunting of the upper surface leading edge and some reshaping of the blade's upper surface resulting in moderately thicker airfoils.

Tauber, M. E.↗
NASA NTRS1979

Gas drag in primordial circumplanetary envelopes - A mechanism for satellite capture

Known properties of the current solar system and Bodenheimer's (1977) model of early Jovian evolution are employed to develop a mechanism for satellite capture based on gas drag in primordial circumplanetary envelopes. In particular, the deceleration and fragmentation of two parent bodies passing through an extended primordial Jovian nebula may account for the clusters of prograde and retrograde satellites of Jupiter. Subsequently, the fragments probably underwent limited orbital evolution, and were dispersed by collision with a stray body. The heavy element cores of the outer planets may also be due to primordial gas drag capture. Nebular drag capture of the Martian satellites Phobos and Deimos, Neptune's Nereid and Triton, and Saturn's Phoebe and Iapetus is also conceivable.

Pollack, J. B.↗
NASA NTRS1979

Computation of subsonic and transonic flow about lifting rotor blades

An inviscid, nonconservative, three-dimensional potential flow code has been developed for computing the quasi-steady flow about an isolated lifting rotor blade. Calculations from the code were compared with chordwise pressure measurements obtained in a wind tunnel on a nonlifting rotor at transonic tip speeds at advance ratios from 0.40 to 0.55. The overall agreement between theoretical calculations and experiment was good. To illustrate the early capability of the program, the flow about a hypothetical lifting rotor blade having twist, airfoil thickness taper, and a 20 deg sweptback tip was analyzed at azimuthal positions of 60, 90, and 120 deg for an advance ratio of 0.342. A typical run on a CDC 7600 computer required about 5 min for one rotor position at transonic tip speeds.

Arieli, R.↗
NASA NTRS1978

Trajectory module of the NASA Ames Research Center aircraft synthesis program ACSYNT

A program was developed to calculate trajectories for both military and commercial aircraft for use in the aircraft synthesis program, ACSYNT. The function of the trajectory module was to calculate the changes in the vehicle's flight conditions and weight, as fuel is consumed, during the flying of one or more missions. The trajectory calculations started with a takeoff, followed by up to 12 phases chosen from among the following: climb, cruise, acceleration, combat, loiter, descent, and paths. In addition, a balanced field length was computed. The emphasis was on relatively simple formulations and analytic expressions suitable for rapid computation since a prescribed trajectory had to be calculated many times in the process of converging an aircraft design, or finding an optimum configuration. The trajectory module consists of about 2500 cards and operational on a CDC 7600 computer.

Tauber, M. E.↗
NASA NTRS1978

An analytic study of impact ejecta trajectories in the atmospheres of Venus, Mars, and earth

Calculations have been made to determine the effects of atmospheric drag and gravity on impact ejecta trajectories on Venus, Mars, and earth. The equations of motion were numerically integrated for a broad range of body sizes, initial velocities, and initial elevation angles. A dimensionless parameter was found from approximate analytic solutions which correlated the ejecta range, final impact angle, and final impact velocity for all three planets.

Tauber, M. E.↗
NASA NTRS1978

Analytic investigation of advancing blade drag reduction by tip modifications

Analytic techniques were applied to study the effect on the performance of the nonlifting advancing blade when the outboard 5% of the blade is modified to reduce drag. The tip modifications studied consisted of reducing airfoil thickness, sweepback, and planform taper. The reductions in instantaneous drag and torque were calculated for tip speed ratios from about 0.19 to 0.30, corresponding to advancing blade tip Mach numbers of 0.855 to 0.936, respectively. Approximations required in the analysis introduce uncertainties into the computed absolute values of drag and torque; however, the differences in the quantities should be a fairly reliable measure of the effect of changing tip geometry. For example, at the highest tip speed, instantaneous drag, and torque were reduced by 20% and 24%, respectively, for tip sweep of 40 deg on a blade using an NACA 0010 airfoil and by comparable amounts for 30-deg sweep on a blade having an NACA 0012 airfoil section. The present method should prove to be a useful, inexpensive technique for identifying promising configurations for additional study and testing.

Tauber, M. E.↗
NASA NTRS1976

A program for calculating turbofan-driven lift-fan propulsion system performance

The performance of a turbofan-powered lift fan propulsion system for vertical takeoff and landing (VTOL) aircraft is calculated. The program formulation consists of taking bleed air from a turbofan engine, heating the bleed air in an interburner, and passing it through a tip turbine to drive a lift fan. Two options are available: bleed air from the engine exhaust, or bleed air that has passed through the engine fan only. This computer program will benefit persons unfamiliar with the thermodynamics of engine cycle analysis.

Tauber, M. E.↗
NASA NTRS1976

Impact craters on Venus

Calculations are made to determine the sizes of stony and iron meteoroids which could penetrate the atmosphere of Venus and cause hypervelocity impact craters on the planet's surface. Using scaling relationships based on kinetic energy, impact crater size is related to meteoroid size. Finally, it is determined that the smallest impact craters that might exist on Venus are on the order of 150 to 300 meters in diameter.

Tauber, M. E.↗
NASA NTRS1972

'Thunder' - Shock waves in pre-biological organic synthesis.

Theoretical study of the gasdynamics and chemistry of lightning-produced shock waves in a postulated primordial reducing atmosphere. It is shown that the conditions are similar to those encountered in a previously performed shock-tube experiment which resulted in 36% of the ammonia in the original mixture being converted into amino acids. The calculations give the (very large) energy rate of about 0.4 cal/sq cm/yr available for amino acid production, supporting previous hypotheses that 'thunder' could have been responsible for efficient large-scale production of organic molecules serving as precursors of life.

Bar-Nun, A.↗
NASA NTRS1969

Atmospheric entry into Jupiter

Blunt and conical body optimum heat shield shapes for Jupiter atmospheric entry, noting shallow flight path

Tauber, M. E.↗