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NASA NTRS1983

On some flow characteristics of conventional and excited jets

Improved correlations of jet centerline velocity and static temperature decay data for convergent nozzles are developed. From these empirical correlations, a relationship was devised by which the static temperature decay for a nonisothermal jet plume can be determined from cold-flow jet centerline velocity decay data or prediction. This relationship is shown to apply as well to jet plumes for various nozzle shapes. It is assumed, by analogy, that this relationship also applies to acoustically excited jet plumes. Jet plume spreading with and without excitation is discussed. Finally, the radial velocity and temperature profiles for conventional and enhanced mixing jet flows are shown and their implication for excited flows is discussed.

Vonglahn, U. H.↗

NASA NTRS1984

On some flow characteristics of conventional and excited jets

Von Glahn, U. H.↗

NASA NTRS2000

Towards LES Models of Jets and Plumes

As pointed out by Rodi standard integral solutions for jets and plumes developed for discharge into infinite, quiescent ambient are difficult to extend to complex situations, particularly in the presence of boundaries such as the sea floor or ocean surface. In such cases the assumption of similarity breaks down and it is impossible to find a suitable entrainment coefficient. The models are also incapable of describing any but the most slowly varying unsteady motions. There is therefore a need for full time-dependent modeling of the flow field for which there are three main approaches: (1) Reynolds averaged numerical simulation (RANS), (2) large eddy simulation (LES), and (3) direct numerical simulation (DNS). Rodi applied RANS modeling to both jets and plumes with considerable success, the test being a match with experimental data for time-averaged velocity and temperature profiles as well as turbulent kinetic energy and rms axial turbulent velocity fluctuations. This model still relies on empirical constants, some eleven in the case of the buoyant jet, and so would not be applicable to a partly laminar plume, may have limited use in the presence of boundaries, and would also be unsuitable if one is after details of the unsteady component of the flow (the turbulent eddies). At the other end of the scale DNS modeling includes all motions down to the viscous scales. Boersma et al. have built such a model for the non-buoyant case which also compares well with measured data for mean and turbulent velocity components. The model demonstrates its versatility by application to a laminar flow case. As its name implies, DNS directly models the Navier-Stokes equations without recourse to subgrid modeling so for flows with a broad spectrum of motions (high Re) the cost can be prohibitive - the number of required grid points scaling with Re(exp 9/4) and the number of time steps with Re(exp 3/4). The middle road is provided by LES whereby the Navier-Stokes equations are formally filtered with the filter chosen to only exclude the smallest turbulent motions. If successful, LES should provide much of the detail available to DNS but at more bearable cost. Fatica et al. in comparing LES with DNS for a low Reynolds number jet showed that the LES could simulate the temporally evolving behavior including growth of the jet thickness. It is the intention of this report to explore the application of an LES model to jets and plumes. As always, before tackling complex situations, the model must be tested for the simplest of cases and so we address only two, a non-buoyant axisymmetric jet issuing steadily from an orifice into a semi-infinite stationary environment and a buoyant jet in the same environment. The work is a continuation of Basu and Mansour.

Webb, A. T.↗

NASA NTRS1982

Aerodynamic interactions with turbulent jet exhaust plumes

The importance of aerodynamic interactions associated with external flow-field effects on turbulent jet exhaust plume structure is discussed. A viscous/inviscid prediction technique is presented which combines the overlaid mixing and inviscid plume components of the JANNAF Standardized Plume Flow-Field (SPF) model with inviscid external flow and boundary-layer analyses for treating nozzle afterbodies at subsonic/transonic speeds. Validation of the technique via comparisons between predictions and experiment for cold-air jet plumes is presented. Predicted spatial temperature distributions for hot, nonafterburning plumes are presented and compared to results obtained from more simplified prediction techniques in order to assess the importance of the aerodynamic interactions associated with external boundary layers and pressure gradients. It is demonstrated that these interactions play a significant role in determining the near-field turbulent mixing and inviscid plume shock structure. The implication of these results to plume radiation predictions is discussed.

Wilmoth, R. G.↗

NASA NTRS2009

Liquid Water on Enceladus from Observations of Ammonia and Ar-40 in the Plume

Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell-as suggested most recently by the discovery of salts in E-ring particles derived from the plume-or warm ice that is heated, causing dissociation of clathrate hydrates. Here we report that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, Ar-40. The presence of ammonia provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate. We conclude, from the overall composition of the material, that the plume derives from both a liquid reservoir (or from ice that in recent geological time has been in contact with such a reservoir) as well as from degassing, volatile-charged ice. As part of a general comprehensive review of the midsize saturnian satellites at the conclusion of the prime Cassini mission, PI McKinnon and co-I Barr contributed to three review chapters.

Waite, J. H., Jr.↗

NASA NTRS1985

Preliminary analysis of tone-excited two-stream jet velocity decay

Acoustic research related to jet flows has established that sound, by amplifying the naturally occuring large-scale structures in turbulent shear layers, can cause a more rapidly decay of the jet plume velocity and temperature and an increase in jet spreading rate. One possible application of this sound-flow interaction phenomenon is to future STOL aircraft that may require modified jet plume characteristics in order to reduce the loads and temperatures on the deflected flaps during take-off and landing operations. The tone-excitation effect on the velocity decay of model-scale, two-stream jet plumes is analyzed. Measured data are correlated in terms of parameters that include excitation sound level and outer-to-inner stream velocity ratio. The effect of plume tone-excitation on far-field jet noise is examined and its implication for large-scale two-stream jets is discussed.

Vonglahn, U. H.↗

NASA NTRS2006

Visualization of a Capsule Entry Vehicle Reaction-Control System (RCS) Thruster

Planar laser-induced fluorescence (PLIF) was used to visualize the reaction control system (RCS) jet flow emanating from the aft-body of an Apollo-geometry capsule test article in the NASA Langley Research Center 31-Inch Mach 10 Air wind tunnel. The RCS jet was oriented normal to the aft surface of the model and had a nominal Mach number of 2.94. The composition of the jet gas by mass was 95% nitrogen (N2) and 5% nitric oxide (NO). The RCS jet flowrate varied between zero and 0.5 standard liters per minute and the angle of attack and tunnel stagnation pressure were also varied. PLIF was used to excite the NO molecules for flow visualization. These flow visualization images were processed to determine the trajectory and to quantify the flapping of the RCS jet. The spatial resolution of the jet trajectory measurement was about 1 mm and the single-shot precision of the measurement was estimated to be 0.02 mm in the far field of the jet plume. The jet flapping, measured by the standard deviation of the jet centerline position was as large as 0.9 mm, while the jet was 1.5-4 mm in diameter (full width at half maximum). Schlieren flow visualization images were obtained for comparison with the PLIF. Surface pressures were also measured and presented. Virtual Diagnostics Interface (VIDI) technology developed at NASA Langley was used to superimpose and visualize the data sets. The measurements demonstrate some of the capabilities of the PLIF method while providing a test case for computational fluid dynamics (CFD) validation.

Danehy, P. M.↗

NASA NTRS1994

A six degree of freedom, plume-fuel optimal trajectory planner for spacecraft proximity operations using an A* node search

Spacecraft proximity operations are complicated by the fact that exhaust plume impingement from the reaction control jets of space vehicles can cause structural damage, contamination of sensitive arrays and instruments, or attitude misalignment during docking. The occurrence and effect of jet plume impingement can be reduced by planning approach trajectories with plume effects considered. An A* node search is used to find plume-fuel optimal trajectories through a discretized six dimensional attitude-translation space. A plume cost function which approximates jet plume isopressure envelopes is presented. The function is then applied to find relative costs for predictable 'trajectory altering' firings and unpredictable 'deadbanding' firings. Trajectory altering firings are calculated by running the spacecraft jet selection algorithm and summing the cost contribution from each jet fired. A 'deadbanding effects' function is defined and integrated to determine the potential for deadbanding impingement along candidate trajectories. Plume costs are weighed against fuel costs in finding the optimal solution. A* convergence speed is improved by solving approach trajectory problems in reverse time. Results are obtained on a high fidelity space shuttle/space station simulation. Trajectory following is accomplished by a six degree of freedom autopilot. Trajectories planned with, and without, plume costs are compared in terms of force applied to the target structure.

Jackson, Mark Charles↗

NASA NTRS1986

Progress towards a model to describe jet/aerodynamic-surface interference effects

A first generation model is presented which relates the pressure distribution on an aerodynamic surface to properties of the jet plume. The characteristics of a jet in a cross flow are of primary importance in determining the pressure distribution on the aerodynamic surface and are assumed to be (1) a pair of contrasting vortices associated with a jet in a crossflow, (2) entrainment of crossflow fluid into the jet plume, and (3) a wake region near the aerodynamic surface and extending downstream from the jet orifice. The model is applied to the configuration of a round jet exhausting perpendicularly through a flat plate into a uniform crossflow for a range of jet-to-crossflow velocity ratios from three to ten. It is demonstrated that the model is capable of describing the measured pressure distribution on the flat plate with model parameters that are compatable with the incomplete description of the vortex pair that is available. The fore and moments on one plate are presented as functions of jet-to-crossflow velocity ratios.

Fearn, R. L.↗

NASA NTRS1993

An experimental study of the flow field surrounding a subsonic jet in a cross flow

An experimental investigation of the flow interaction of a 5.08 cm (2.00 in.) diameter round subsonic jet exhausting perpendicularly to a flat plate in a subsonic cross flow was conducted in the NASA Ames 7x1O ft. Wind Tunnel Number One. Flat plate surface pressures were measured at 400 locations in a 30.48 cm (12.0 in.) concentric circular array surrounding the jet exit. Results from these measurements are provided in tabular and graphical form for jet-to-crossflow velocity ratios ranging from 4 to 12, and for jet exit Mach numbers ranging from 0.50 to 0.93. Laser doppler velocimeter (LDV) three component velocity measurements were made in selected regions in the developed jet plume and near the flat plate surface, at a jet Mach number of 0.50 and jet-to-crossflow velocity ratios of 6 and 8. The results of both pressure and LDV measurements are compared with the results of previous experiments. In addition, pictures of the jet plume shape at jet velocity ratios ranging from 4 to 12 were obtained using schleiren photography. The LDV measurements are consistent with previous work, but more extensive measurements will be necessary to provide a detailed picture of the flow field. The surface pressure results compare closely with previous work and provide a useful characterization of jet induced surface pressures. The results demonstrate the primary influence of jet velocity ratio and the secondary influence of jet Mach number in determining such surface pressures.

Dennis, Robert Foster↗

NASA NTRS1977

Results of tests using a 0.0125-scale model (70-QT) of the space shuttle vehicle orbiter in the AEDC VKF tunnel B (IA22), volume 2

Tabulated data of an experimental investigation are presented which was conducted in the AEDC/VKF Tunnel B to obtain interaction effects of RCS thruster jet plumes on SSV aerodynamics during staging to simulate RTLS abort. Interaction effects of the orbiter RCS thruster jet plumes on the orbiter and ET aerodynamics were investigated. RCS thruster jet plumes were simulated using both air and a 15 percent argon 85 percent helium gas mixture. The ET angle of attack range was -40 to +25 deg at sideslip angles of 0, 3, and 6 degrees. Orbiter angle of attack was varied from -15 to +10 degrees at sideslip angles of 0 and 3 deg. External tank full scale separation distances simulated were 0 to 1400 in. axially; 0 to 54 in. laterally; and a range of -100 to 1000 in. vertically. Data were also obtained on the ET in the interference-free flow field. Quiescent (no tunnel flow) thruster plume interaction data were obtained on the orbiter and orbiter-ET combination. Tests were conducted at Mach number 6 and a Reynolds number of 0.86 million per foot.

Daileda, J. J.↗

NASA NTRS2005

Thruster Plume Plasma Diagnostics: A Ground Chamber Experiment for a 2-Kilowatt Arcjet

Although detailed near field (0 to 3 cm) information regarding the exhaust plume of a two kilowatt arc jet is available (refs. 1 to 6), there is virtually little or no information (outside of theoretical extrapolations) available concerning the far field (2.6 to 6.1 m). Furthermore real information about the plasma at distances between (3 to 6 m) is of critical importance to high technology satellite companies in understanding the effect of arc jet plume exhausts on space based power systems. It is therefore of utmost importance that one understands the exact nature of the interaction between the arc jet plume, the spacecraft power system and the surrounding electrical plasma environment. A good first step in understanding the nature of the interactions lies in making the needed plume parameter measurements in the far field. All diagnostic measurements are performed inside a large vacuum system (12 m diameter by 18 m high) with a full scale arc jet and solar array panel in the required flight configuration geometry. Thus, necessary information regarding the plume plasma parameters in the far field is obtained. Measurements of the floating potential, the plasma potential, the electron temperature, number density, density distribution, debye length, and plasma frequency are obtained at various locations about the array (at vertical distances from the arc jet nozzle: 2.6, 2.7, 2.8, 3.2, 3.6, 4.0, 4.9, 5.0, 5.4, 5.75, and 6.14 m). Plasma diagnostic parameters are measured for both the floating and grounded configurations of the arc jet anode and array. Spectroscopic optical measurements are then acquired in close proximity to the nozzle, and contamination measurements are made in the vicinity of the array utilizing a mass spectrometer and two Quartz Crystal Microbalances (QCM's).

Galofaro, Joel T.↗

NASA NTRS2004

Cross-Stream PIV Measurements of Jets With Internal Lobed Mixers

With emphasis being placed on enhanced mixing of jet plumes for noise reduction and on predictions of jet noise based upon turbulent kinetic energy, unsteady measurements of jet plumes are a very important part of jet noise studies. Given that hot flows are of most practical interest, optical techniques such as Particle Image Velocimetry (PIV) are applicable. When the flow has strong azimuthal features, such as those generated by chevrons or lobed mixers, traditional PIV, which aligns the measurement plane parallel to the dominant flow direction is very inefficient, requiring many planes of data to be acquired and stacked up to produce the desired flow cross-sections. This paper presents PIV data acquired in a plane normal to the jet axis, directly measuring the cross-stream gradients and features of an internally mixed nozzle operating at aircraft engine flow conditions. These nozzle systems included variations in lobed mixer penetration, lobe count, lobe scalloping, and nozzle length. Several cases validating the accuracy of the PIV data are examined along with examples of its use in answering questions about the jet noise generation processes in these nozzles. Of most interest is the relationship of low frequency aft-directed noise with turbulence kinetic energy and mean velocity.

Bridges, James↗

NASA NTRSDate not supplied

On the Interaction Between a Flow Instability and Inertial Particles in Supersonic Jet Plume-Surface Interaction

Extraterrestrial landings often require spacecraft to deploy supersonic jets directed at dusty planetary surfaces to ensure controlled descents. This interaction, termed plume-surface interaction (PSI), critically influences crater formation and the dynamics of ejected particles, which can obscure vision, damage onboard sensors, and impact nearby infrastructure with significant particle velocities. The physics of PSI remain poorly understood due to the complexities in simulating the involved multiphysics and experimentally replicating reduced atmospheric pressure conditions. This article discusses a collaborative effort to investigate PSI in reduced atmospheric pressure environments using a Mach 5.3 jet impinging on a granular bed. The results highlight observations of an azimuthal pattern in the ejecta distribution, characterized by alternating ejecta streaks of varying particle concentrations. This phenomenon suggests the presence of a low Reynolds number instability, a notable discovery given the supersonic nature of the jet.

PSI↗

NASA NTRS1995

Aerodynamic Performance Predictions of Single and Twin Jet Afterbodies

The multiblock three-dimensional Navier-Stokes method PAB3D was utilized by the Component Integration Branch (formerly Propulsion Aerodynamics Branch) at the NASA-Langley Research Center in an international study sponsored by AGARD Working Group #17 for the assessment of the state-of-the-art of propulsion-airframe integration testing techniques and CFD prediction technologies. Three test geometries from ONERA involving fundamental flow physics and four geometries from NASA-LaRC involving realistic flow interactions of wing, body, tail, and jet plumes were chosen by the Working Group. An overview of results on four (1 ONERA and 3 LaRC) of the seven test cases is presented. External static pressures, integrated pressure drag and total drag were calculated for the Langley test cases and jet plume velocity profiles and turbulent viscous stresses were calculated for the ONERA test case. Only selected data from these calculations are presented in this paper. The complete data sets calculated by the participants will be presented in an AGARD summary report. Predicted surface static pressures compared favorably with experimental data for the Langley geometries. Predicted afterbody drag compared well with experiment. Predicted nozzle drag was typically low due to over-compression of the flow near the trailing edge. Total drag was typically high. Predicted jet plume quantities on the ONERA case compared generally well with data.

Carlson, John R.↗

NASA NTRS1992

Experimental results for a hypersonic nozzle/afterbody flow field

The flow field created by the interaction of a single-expansion-ramp-nozzle (SERN) flow with a hypersonic external stream has been experimentally characterized using a generic nozzle/afterbody model in the 3.5-foot hypersonic wind tunnel of the NASA Ames Research Center. The presented results include oil-flow and shadowgraph flow visualization photographs, afterbody surface-pressure distributions, boundary layer rake measurements, and Preston-tube skin-friction measurements. The design, construction, and operation of the model was found to be successful. Surface oil-flow patterns show that the jet-plume flow attaches to the afterbody surface at jet pressure ratios between 154 and 234. The oil flow also shows the pattern of lines where the jet flow separates from the ramp, apparently as a result of interaction of the jet-plume internal shock wave with the ramp boundary layer.

Spaid, Frank W.↗

NASA NTRS2006

Reducing Propulsion Airframe Aeroacoustic Interactions With Uniquely Tailored Chevrons: 3. Jet-Flap Interaction

Propulsion airframe aeroacoustic (PAA) interactions, resulting from the integration of engine and airframe, lead to azimuthal asymmetries in the flow/acoustic field, e.g., due to the interaction between the exhaust jet flow and the pylon, the wing and its high-lift devices, such as, flaps and flaperons. In the first two parts of this series we have presented experimental results which show that isolated and installed nozzles with azimuthally varying chevrons (AVCs) can reduce noise more than conventional chevrons when integrated with a pylon and a wing with flaps at take-off conditions. In this paper, we present model-scale experimental results for the reduction of jet-flap interaction noise source due to these AVCs and document the PAA installation effects (difference in noise between installed and isolated nozzle configurations) at both approach and take-off conditions. It is found that the installation effects of both types of chevron nozzles, AVCs and conventional, are reversed at approach and take-off, in that there is more installed noise reduction at approach and less at take-off compared to that of the isolated nozzles. Moreover, certain AVCs give larger total installed noise benefits at both conditions compared to conventional chevrons. Phased microphone array results show that at approach conditions (large flap deflection, low jet speed and low ambient Mach number), chevrons gain more noise benefit from reducing jetflap interaction noise than they do from quieting the jet plume noise source which is already weak at these low jet speeds. In contrast, at take-off (small flap deflection, high jet speed and high ambient Mach number) chevrons reduce the dominant jet plume noise better than the reduction they create in jet-flap interaction noise source. In addition, fan AVCs with enhanced mixing near the pylon are found to reduce jet-flap interaction noise better than conventional chevrons at take-off.

Thomas, Russ H.↗

NASA NTRS1981

Mixer nozzle aeroacoustic characteristics for the energy efficient engine

Aeroacoustic tests are conducted on scale model mixer nozzle configurations, a separate flow nozzle, and a baseline conical nozzle in an anechoic chamber free-jet facility to investigate exhaust system designs. Far-field acoustic data and exhaust jet plume aerodynamic data are obtained for various combinations of exhaust jet velocity and simulated flight speed, with corrected microphone data at a constant 12.2 m arc distance, and scaled acoustic data at a sideline distance of 457 m. It is found that jet plume aerodynamic and acoustic characteristics of lobed mixer exhaust systems are similar to those of a conical nozzle operating at the same specific thrust, although differences occur at high frequencies, where the sound pressure level of the mixer nozzle is 1-5 dB higher than that of a conical nozzle. In addition, no direct correlation is found between exit plane turbulence levels and plume development or acoustic characteristics for mixer exhaust configurations.

Gliebe, P. R.↗