Numerical study of the flow and the near acoustic fields of an underexpanded round free jet generating two screech tones
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Citations
Oscillation Modes in Screeching Jets
Antisymmetric Oscillation Modes in Rectangular Screeching Jets
Acoustic feedback loops for screech tones of underexpanded free round jets at different modes
An experimental investigation of coupled underexpanded supersonic twin-jets
Overview of the Use of Large-Eddy Simulations in Jet Aeroacoustics
References
Über die stationären Wellen in einem Gasstrahl
Investigation of the mixing layer of underexpanded supersonic jets by particle image velocimetry
Screech Tones from Rectangular Jets with Spanwise Oblique Shock-Cell Structures
Etude expérimentale de l'effet du vol sur le bruit de choc de jets supersoniques sous-détendus
Predictions of Supersonic Jet Mixing and Shock-Associated Noise Compared With Measured Far-Field Data
Related Papers (5)
Frequently Asked Questions (11)
Q2. What are the future works in "Numerical study of the flow and the near acoustic fields of an underexpanded round free jet generating two screech tones" ?
The convection velocity of large-scale structures in the jet shear layers is evaluated, and values similar to experimental data are found. The mixing noise component seems due to the sudden intrusion of turbulent structures into the potential core, near its end.
Q3. What is the strength of the forcing chosen?
The strength of the forcing is chosen in order to obtain turbulent intensities of around 6% of the fully expanded jet velocity at the nozzle exit.
Q4. How is the convection velocity at the nozzle exit?
the convection velocity is close to the value 0:35uj ’ 0:5ue at the nozzle exit, as expected for instabilities initially growing in the mixing layers just downstream of the nozzle.
Q5. What was the first to use schlieren pictures in experiments?
The results from this jet were also used to generate schlieren-like images, in a study of Castelain et al.,17 in order to asses the quality of the estimation of the convection velocity in the jet shear layers using schlieren pictures in experiments.
Q6. How many times did Raman43 observe two screech tones switching in time?
Fornon-ideally expanded jets exiting from a rectangular nozzle with a single-bevelled exit, Raman43 also observed two screech tones switching in time.
Q7. What is the central frequency of the broadband shock-associated noise?
the size of the sixth shock cell, Ls6 ¼ 2:35r0, located around z ¼ 15r0, is used in the relation (9) to compute the central frequency of the broadband shock-associated noise as a function of angle .
Q8. What is the mechanism of the broadband shock-associated noise?
In this mechanism, the broadband shock-associated noise is generated by the interactions between the turbulent structures propagating downstream in the jet shear layers and the shocks of the quasi-periodic shock cell structure.
Q9. What is the mean convection velocity of the cell structures in the jet?
In order to apply equation (8) to the simulated jet, the mean convection velocity is considered equal to 5 uc 4 ¼ 0:65uj in the region 5r0 5 z5 15r0, as suggested in Figure 12.
Q10. What is the frequency of the first mode of the broadband shock-associated noise?
For screeching jets, Tam et al.13 suggested that the central frequency of the first mode N¼ 1 of the broadband shock-associated noise tends to the screech frequency at ¼ 180 .
Q11. Where is the local convection velocity of the turbulent structures?
The local convection velocity of the turbulent structures is estimated at the center of the shear layer, where the velocity fluctuations are maximum, as presented in Figure 11.