Research ArticleAPPLIED SCIENCES AND ENGINEERING

Improving supersonic flights with femtosecond laser filamentation

See allHide authors and affiliations

Science Advances  02 Nov 2018:
Vol. 4, no. 11, eaau5239
DOI: 10.1126/sciadv.aau5239
  • Fig. 1 Experimental Arrangement.

    (A) Computer-assisted drawing view of the experimental setup. The supersonic air flow emerges from the left. The test model is located 160-mm downstream of the nozzle exit section. The laser beam (shown in dark red) is steered from below by mirrors toward the test model from where it emerges toward the left. It is focused by a converging lens (focal length, 1000 mm), with its focal point 50-mm upstream of the model nose. Side windows on the test section provide an optical access to the test model in the flow. (B) Photograph of the test model in the presence of the femtosecond laser pulse in an M = 3 supersonic flow. White and violet correspond to the broadband continuum and plasma luminescence from the filament, respectively. The conical emission near the front nose is due to the plasma emission in the recirculating bubble. Photo credit: Aurélien Houard, LOA-CNRS.

  • Fig. 2 Experimental drag signal measured by the balance (in black) and drag computed from the simulation for a deposited energy of 10 mJ (in blue).

    The laser pulse is at t = 0. The corresponding energy of the 50-fs laser pulse emerging from the front nose is 100 mJ. The red curves show the reconstructed drag signal obtained by convoluting the computed drag signal with estimates of the balance transfer function (damped second-order system) by adding either a constant delay (continuous line) or a secondary spring-mass system (dashed line) to account for the model nose deformation (see the supplementary materials).

  • Fig. 3 Formation of a low-density core by the laser energy deposition.

    (A) Schlieren image in static air recorded 17.2 μs after the laser pulse, showing the central low-density core and the lateral shock wave. The location of the pressure sensors is shown by the two white arrows. (B) Density variations induced by the laser filament during a test run, 40.3 μs after the laser pulse. The variations are given relative to the stream number density n0 = 6.4 × 1018cm− 3 in the absence of laser.

  • Fig. 4 Interaction of the laser energy deposition with the supersonic flow.

    Time-resolved schlieren images in the presence of Mach 3 air flow coming from the left, recorded at different delays after the laser shot: 0.3 μs (A), 47 μs (B), 94 μs (C), 153 μs (D), 200 μs (E), and 324 μs (F). The formation of a bubble upstream of the front nose is followed by a downstream expansion flow along the test model surface and the recovery of initial conditions after 300 μs.

  • Fig. 5 Comparison of experimental and numerical results.

    Schlieren image of the shock wave disturbance obtained 12 μs (A), 65 μs (B), and 83 μs (C) after the laser pulse. The corresponding numerical schlieren images obtained from the numerical simulation are respectively shown in (D), (E), and (F), and the calculated gas density field is shown in (G), (H), and (I).

  • Fig. 6 Effect of an off-axis energy deposition.

    (A) Image of the shock wave disturbance obtained after 200 μs by a laser propagating slightly off axis. Since the shock front in the upper part of the figure is detached from the object surface, it leads to a net asymmetric drag that steers the object upward. (B) Corresponding signal from the piezoelectric pressure gauges in arbitrary units (a.u). The two pressure gauges are mounted vertically in a plane centered on the model axis, as shown in Fig. 3. The upper and lower curves of the figure show the signals detected by the corresponding gauges. Only the upper lying gauge responds significantly, indicating an upward directed decrease in drag.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/11/eaau5239/DC1

    Section S1. Experimental setup

    Section S2. Characteristics of the femtosecond laser

    Section S3. Details of the test model

    Section S4. Extraction of the change of drag induced by the laser pulse

    Section S5. Wavefront sensor device to measure the filament induced changes of air density

    Section S6. Simulations

    Fig. S1. General view of the experimental setup.

    Fig. S2. Response of the strain gauge to a femtosecond laser pulse and to a percussion shock from a falling sphere.

    Movie S1. Schlieren images showing the time evolution of the laser energy deposition in the Mach 3 flow.

    Movie S2. Schlieren images showing the time evolution of the laser energy deposition in quiescent air at atmospheric pressure.

  • Supplementary Materials

    The PDF file includes:

    • Section S1. Experimental setup
    • Section S2. Characteristics of the femtosecond laser
    • Section S3. Details of the test model
    • Section S4. Extraction of the change of drag induced by the laser pulse
    • Section S5. Wavefront sensor device to measure the filament induced changes of air density
    • Section S6. Simulations
    • Fig. S1. General view of the experimental setup.
    • Fig. S2. Response of the strain gauge to a femtosecond laser pulse and to a percussion shock from a falling sphere.

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.avi format). Schlieren images showing the time evolution of the laser energy deposition in the Mach 3 flow.
    • Movie S2 (.avi format). Schlieren images showing the time evolution of the laser energy deposition in quiescent air at atmospheric pressure.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article