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Results for “supersonic jet flow”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Subsonic and supersonic jet flow and acoustic characteristics and supersonic suppressors

To study the similarities and differences between subsonic and supersonic jets, velocity and impact pressure fluctuations were determined along the axis over a jet Mach number range of 0.6 to 1.4 for a 2 in. diameter convergent nozzle and for a one inch diameter jet flow. Static pressure distribution fluctuations due to shear and turbulence in the jet flow for subsonic and supersonic jets were related to acoustic radiation to the far field. Also determined were flow and acoustic characteristics of a single shroud, and multiple shroud tube and shroud suppressors for supersonic and subsonic exhaust velocities. A compressor consisting of 191 tubes and 191 shrouds decreased the primary Mach number drastically for both jet Mach numbers of 1.4 and 0.7; rms impact and static pressure fluctuations on the axis were also reduced from values existing for an equivalent area single nozzle.

Nagamatsu, H. T.↗
NASA NTRS1986

Aeroacoustics of contoured plug-nozzle supersonic jet flows

Experimental investigations of the acoustic far-field, the shock associated noise, and the characteristics of the repetitive shock structure of supersonic jet flows issuing from a plug-nozzle having an externally expanded contoured plug with a pointed termination, operated at a range of supercritical pressure ratios of 2.0 to 4.5 are reported. The supersonic jet flow from the contoured plug is shown to be shock-free and virtually wakeless at a pressure ratio of 3.60 (flow Mach number, 1.49). By comparison with the noise characteristics of underexpanded jet flows from an equivalent convergent nozzle, substantial reductions in the total (mixing and the shock associated) noise levels are obtained when the contoured plug nozzle is operated either in the fully-expanded (shock-free) mode or in the over- and the underexpanded modes.

Dosanjh, D. S.↗
NASA NTRS1989

Three-dimensional calculations for underexpanded and overexpanded supersonic jet flows

A three-dimensional code is developed to simulate the characteristics of the jet exhaust plume issuing from nonaxisymmetric nozzles at different flight conditions. In the present paper, the time-iterative Space Marching Scheme (SMS) is used to simulate the shock-cell structure of underexpanded supersonic jet issued from round and square nozzles. Also, the computational results are compared with the experimental data from underexpanded and overexpanded supersonic round jets. The agreement with the experimental data validates the applicability of the new technique for predicting the shock-cell structure of supersonic jet flows. The computational results reveals that the azimuthal structure of the supersonic square jet changed as the jet progressed downstream of the exit nozzle.

Abdol-Hamid, Khaled S.↗
NASA NTRS1975

Ambient and induced pressure fluctuations in supersonic jet flows

An experimental investigation of the ambient static pressure fluctuations and induced acoustic fields in supersonic jet flows has been undertaken to identify possible noise sources and the mechanisms involved in the propagation of disturbances within the flows. The axisymmetric cold air jet under investigation exhausted from a 7-in. exit diameter C-D nozzle run in two conditions: one yielding a fully expanded flow and the other an overexpanded flow. The survey of static pressure fluctuations consisted of measurements of the overall levels and spectra of the fluctuations along the centerline of the two flows and the variation in level across various transverse sections. The second aspect of the study involved the development of a procedure for tracing the propagation of externally induced periodic pressure disturbances inside the jet.

Barra, V.↗
NASA NTRS1985

Aeroacoustics of contoured and solid/porous conical plug-nozzle supersonic jet flows

The acoustic far field, the shock-associated noise and characteristics of the repetitive shock structure of supersonic jet flows issuing from a contoured plug-nozzle and uncontoured plug-nozzle having a short conical plug of either a solid or a combination of solid/porous surface with pointed termination operated at a range of supercritical pressure are reported. The contoured and the uncontoured plug-nozzles had the same throat area and the same annular-radius ratio.

Dosanjh, D. S.↗
DOE OSTI2024

One-dimensional temperature measurement of supersonic jet flow by resonantly ionized photoemission thermometry of molecular nitrogen

As the field of fluid dynamics progresses, the demand for sophisticated diagnostic methods to accurately assess flow conditions rises. In this work, resonantly ionized photoemission thermometry (RIPT) has been used to directly target and ionize diatomic nitrogen (N 2 ) to measure one-dimensional (1D) temperature profiles in a supersonic jet flow. This technique can be considered non-intrusive as the premise uses resonantly enhanced multiphoton ionization (REMPI) to target molecular nitrogen. This resonance excites N 2 into absorption bands of the P, Q, and R rotational branches of N 2 ( b 1 Π u ). The ideal (3 + 1) REMPI scheme excites from the ground state and ionizes N 2 ( b 1 Π u ← X 1 Σ g + ) where de-excitation results in photoemission from the first negative band of ionized N 2 + ( B 2 Σ u + → X 2 Σ g + ) as nitrogen returns to the ground state. The resulting emission can be observed using an intensified camera, thus permitting inference of the rotational temperature of ground-state molecular nitrogen. A linearly regressive Boltzmann distribution is applied based on previous calibration data for this technique to quantify the temperature along the ionized line. This work applies this technique to a pure N 2 supersonic jet in cross-flow and counter-flow orientations to demonstrate N 2 RIPT’s applications in a supersonic flow. Temperature variations are observed at different locations downstream of the exit in cross-flow, and axisymmetric in counter-flow, to generate profiles characterizing the flow dynamics. Due to the collisional effects resulting from the number density of N 2 at higher pressures, a (3 + 2) REMPI scheme is observed throughout this text.

Clark, Aleksander (ORCID:0009000855600042)↗
NASA NTRS1987

Aeroacoustics of supersonic jet flows from contoured and solid/porous conical plug-nozzles

The results of an experimental study of the acoustic far-field, the shock associated noise, and the nature of the repetitive shock structure of supersonic jet flows issuing from plug-nozzles having externally-expanded plugs with pointed termination operated at a range of supercritical pressure ratios Xi approaching 2 to 4.5 are reported. The plug of one of these plug-nozzles was contoured. The other plug-nozzles had short conical plugs with either a solid surface or a combination of solid/porous surface of different porosities. The contoured and the uncontoured plug-nozzles had the same throat area and the same annulus-radius ratio K = R sub p/R sub N = 0.43. As the result of modifications of the shock structure, the acoustic performance of improperly expanded jet flows of an externally-expanded short uncontoured plug of an appropriate geometry with suitably perforated plug and a pointed termination, is shown to approach the acoustic performance of a shock-free supersonic jet issuing from an equivalent externally-expanded contoured plug-nozzle.

Dosanjh, Darshan S.↗
NASA NTRS1994

Structure of supersonic jet flow and its radiated sound

The present paper explores the use of large-eddy simulations as a tool for predicting noise from first principles. A high-order numerical scheme is used to perform large-eddy simulations of a supersonic jet flow with emphasis on capturing the time-dependent flow structure representating the sound source. The wavelike nature of this structure under random inflow disturbances is demonstrated. This wavelike structure is then enhanced by taking the inflow disturbances to be purely harmonic. Application of Lighthill's theory to calculate the far-field noise, with the sound source obtained from the calculated time-dependent near field, is demonstrated. Alternative approaches to coupling the near-field sound source to the far-field sound are discussed.

Mankbadi, Reda R.↗
NASA NTRS1993

The structure of supersonic jet flow and its radiated sound

Large-eddy simulation of a supersonic jet is presented with emphasis on capturing the unsteady features of the flow pertinent to sound emission. A high-accuracy numerical scheme is used to solve the filtered, unsteady, compressible Navier-Stokes equations while modelling the subgrid-scale turbulence. For random inflow disturbance, the wave-like feature of the large-scale structure is demonstrated. The large-scale structure was then enhanced by imposing harmonic disturbances to the inflow. The limitation of using the full Navier-Stokes equation to calculate the far-field sound is discussed. Application of Lighthill's acoustic analogy is given with the objective of highlighting the difficulties that arise from the non-compactness of the source term.

Mankbadi, Reda R.↗
NASA NTRS1983

Nearfield observations of tones generated from supersonic jet flows

The physics of discrete tone generation (screech) from improperly expanded supersonic jets have been investigated experimentally. Both nearfield acoustic survey and phase-averaged schlieren flow visualization were conducted. The dominant mode of flow oscillation that occurred during intense screech and its coupling with the internal shock structure and external sound field were established. Deductions made from the observed coupling mechanism revealed the importance of Helmholtz number and shock cell spacing in the maintenance of screech. Measured amplitude variation of screech are compared with computed amplitude variation of the dominant instability. The results suggest that jet instability plays a direct role in the generation of screech.

Yu, J. C.↗
NASA NTRS2003

Sound Propagation from a Supersonic Jet Flowing through a Rigid-walled Duct with a J-Deflector

An experimental study is performed on the acoustical characteristics of a scale-model, perfectly expanded, cold supersonic jet of gaseous nitrogen (Mach 2.5, nozzle exit diameter of 1 inch) flowing through a rigid-walled duct having an upstream J-deflector. The nozzle is mounted vertically, with the nozzle exit plane at a height of 73 jet diameters above ground level. Relative to the nozzle exit plane, the location of the duct inlet is varied at 10, 5, and -1 jet diameters. Far-field sound pressure levels were obtained at 2 levels (54 jet diameters and 10 jet diameters above ground) with the aid of 9 acoustic sensors equally spaced around a circular arc of radius equal to 80 jet diameters. Comparisons of the acoustic field were made with and without the duct.

Kandula, Max↗
NASA NTRS1986

Computation of multi-dimensional viscous supersonic jet flow

A new method has been developed for two- and three-dimensional computations of viscous supersonic flows with embedded subsonic regions adjacent to solid boundaries. The approach employs a reduced form of the Navier-Stokes equations which allows solution as an initial-boundary value problem in space, using an efficient noniterative forward marching algorithm. Numerical instability associated with forward marching algorithms for flows with embedded subsonic regions is avoided by approximation of the reduced form of the Navier-Stokes equations in the subsonic regions of the boundary layers. Supersonic and subsonic portions of the flow field are simultaneously calculated by a consistently split linearized block implicit computational algorithm. The results of computations for a series of test cases relevant to internal supersonic flow is presented and compared with data. Comparison between data and computation are in general excellent thus indicating that the computational technique has great promise as a tool for calculating supersonic flow with embedded subsonic regions. Finally, a User's Manual is presented for the computer code used to perform the calculations.

Kim, Y. N.↗
NASA NTRS1976

Sonic environment of aircraft structure immersed in a supersonic jet flow stream

Test methods for determining the sonic environment of aircraft structure that is immersed in the flow stream of a high velocity jet or that is subjected to the noise field surrounding the jet, were investigated. Sonic environment test data measured on a SCAT 15-F model in the flow field of Mach 1.5 and 2.5 jets were processed. Narrow band, lateral cross correlation and noise contour plots are presented. Data acquisition and reduction methods are depicted. A computer program for scaling the model data is given that accounts for model size, jet velocity, transducer size, and jet density. Comparisons of scaled model data and full size aircraft data are made for the L-1011, S-3A, and a V/STOL lower surface blowing concept. Sonic environment predictions are made for an engine-over-the-wing SST configuration.

Guinn, W. A.↗
NASA NTRS2014

Wedge Shock and Nozzle Exhaust Plume Interaction in a Supersonic Jet Flow

Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the nozzle exhaust plume. Aft body shock waves that interact with the exhaust plume contribute to the near-field pressure signature of a vehicle. The plume and shock interaction was studied using computational fluid dynamics and compared with experimental data from a coaxial convergent-divergent nozzle flow in an open jet facility. A simple diamond-shaped wedge was used to generate the shock in the outer flow to study its impact on the inner jet flow. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the opposite plume boundary. The sonic boom pressure signature of the nozzle exhaust plume was modified by the presence of the wedge. Both the experimental results and computational predictions show changes in plume deflection.

Castner, Raymond↗