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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 3 — Feb. 11, 2013
  • pp: 3617–3626
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Large-aperture, tapered fiber–coupled, 10-kHz particle-image velocimetry

Paul S. Hsu, Sukesh Roy, Naibo Jiang, and James R. Gord  »View Author Affiliations


Optics Express, Vol. 21, Issue 3, pp. 3617-3626 (2013)
http://dx.doi.org/10.1364/OE.21.003617


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Abstract

We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed particle-image velocimetry (PIV) in turbulent combustion flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of 5.3 mJ and 2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally (bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. Proof-of-concept measurements show significant promise for the performance of fiber-coupled, high-speed PIV using a tapered optical fiber in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine.

© 2013 OSA

1. Introduction

Particle image velocimetry (PIV) has proven to be a useful flow and combustion-diagnostics tool for measuring the velocity of a flow field over a large area [1

1. R. J. Adrian, “Twenty years of particle image velocimetry,” Exp. Fluids 39(2), 159–169 (2005). [CrossRef]

,2

2. T. O. H. Charrett, S. W. James, and R. P. Tatam, “Optical fibre laser velocimetry: a review,” Meas. Sci. Technol. 23(3), 032001 (2012). [CrossRef]

]. Recently, high-repetition-rate (1–10 kHz) PIV laser systems have been developed that enable time-series measurements of high-frequency events such as thermo-diffusive instability and acoustic instability in turbulent combustion flows [3

3. D. L. Wisman, S. D. Marcum, and B. N. Ganguly, “Electrical control of the thermodiffusive instability in premixed propane-air flames,” Combust. Flame 151(4), 639–648 (2007). [CrossRef]

6

6. P. S. Hsu, N. Jiang, J. R. Gord, and S. Roy, “Fiber-coupled, 10 kHz simultaneous OH planar laser-induced fluorescence/particle-image velocimetry,” Opt. Lett. 38(2), 130–132 (2013). [CrossRef]

]. This technique is often used together with planar laser-induced fluorescence (PLIF) for simultaneous measurements of velocity and species concentration in turbulent flames [7

7. T. R. Meyer, G. J. Fiechtner, S. P. Gogineni, J. C. Rolon, C. D. Carter, and J. R. Gord, “Simultaneous PLIF/PIV investigation of vortex-induced annular extinction in H2-air counterflow diffusion flames,” Exp. Fluids 36(2), 259–267 (2004). [CrossRef]

]. However, combustors and engine test facilities that contain high-pressure/-temperature liquid, gas, or equally reactive materials are often challenging to access, even with a simple optical method such as PIV. Additionally, the harsh environments associated with these combustion facilities (i.e., dust particles, uncontrolled humidity, vibration, and large thermal gradients) may restrict the operation of sensitive laser systems. Recent works by Jiang et al. have shown that long, complicated optical paths (~15 m) can be employed to mitigate such problems that are encountered in hypersonic wind-tunnel facilities when using PLIF and PIV [8

8. N. Jiang, M. Webster, W. R. Lempert, J. D. Miller, T. R. Meyer, C. B. Ivey, and P. M. Danehy, “MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel,” Appl. Opt. 50(4), A20–A28 (2011). [CrossRef] [PubMed]

,9

9. N. Jiang, J. Bruzzese, R. Patton, J. Sutton, R. Yentsch, D. V. Giatonde, W. R. Lempert, J. D. Miller, T. R. Meyer, R. Parker, T. Wadham, M. Holden, and P. M. Danehy, “NO PLIF imaging in the CUBRC 48-inch shock tunnel,” Exp. Fluids 53(6), 1637–1646 (2012). [CrossRef]

]. An alternative has been suggested which involves the use of a beam-delivery system based on a 3D-articulated light arm and bulk optics (e.g., the LaserPulse Light Arm for PIV Model 610015manufactured by TSI Inc.). However, this type of beam-delivery system has a limited working distance (~2 m), does not provide sufficient flexibility and ability to access non-windowed test sections, and is relatively expensive. In contrast, a fiber-based optical-beam-delivery approach not only overcomes the aforementioned difficulties for a PIV system performing in harsh optical environments but also provides sufficient flexibility and working distance.

In this study we developed a fiber-coupled, 10-kHz PIV system that employs a large-aperture, tapered step-index fiber to permit efficient delivery of high pulse energy for high-speed flow-velocity measurements. This fiber has delivery capability that is improved with respect to pulse energy and coupling efficiency as compared with that of the standard, large-core step-index fiber used in Ref [6

6. P. S. Hsu, N. Jiang, J. R. Gord, and S. Roy, “Fiber-coupled, 10 kHz simultaneous OH planar laser-induced fluorescence/particle-image velocimetry,” Opt. Lett. 38(2), 130–132 (2013). [CrossRef]

]. Particularly, such improvement was achieved without sacrificing beam quality, which makes this fiber very suitable for fiber-coupled, high-speed PIV applications. The fundamental transmission characteristics of high-PRR, 532-nm, nanosecond (ns)-duration laser pulses were studied for the tapered fiber. The effects of high-PRR, visible laser irradiation on fiber transmission are discussed.

2. Design and testing of large-aperture, tapered–fiber, high-power beam-delivery system

2.1 Design of large-aperture, tapered fiber

An ideal optical fiber for PIV beam delivery must meet two essential criteria: 1) transmission of sufficient laser pulse energy for generation of a PIV signal with reasonable signal-to-noise ratio (SNR) without causing fiber damage, 2) minimization of beam-profile distortion (i.e., with a smaller beam-quality factor M2). The transmission could be enhanced by increasing the fiber core size (maximum transmission µ core area); however, this would result in degradation of the beam quality M2 (i.e., the ability of the laser beam to be propagated and focused). In general, the transmission capability of the ideal optical fiber is expected to be equivalent to or greater than that of the typical silica fiber with a core diameter of ~1000 μm [12

12. D. J. Anderson, R. D. Morgan, D. R. McCluskey, J. D. C. Jones, W. J. Easson, and C. A. Greated, “An optical fiber delivery system for pulsed laser particle image velocimetry illumination,” Meas. Sci. Technol. 6(6), 809–814 (1995). [CrossRef]

,14

14. J. Estevadeordal, T. R. Meyer, S. P. Gogineni, M. D. Polanka, and J. R. Gord, “Development of a fiber-optic PIV system for turbomachinery applications,” in Proceedings of 43rd AIAA Aerospace Sciences Meeting and Exhibit, AIAA-2005-0038 (2005).

] but with the beam quality equivalent to or better than that of the 600-μm-core fiber (M2 ~90) [12

12. D. J. Anderson, R. D. Morgan, D. R. McCluskey, J. D. C. Jones, W. J. Easson, and C. A. Greated, “An optical fiber delivery system for pulsed laser particle image velocimetry illumination,” Meas. Sci. Technol. 6(6), 809–814 (1995). [CrossRef]

].

The geometry and length of the large-aperture, tapered step-index fiber are shown in Fig. 1
Fig. 1 Geometry of a large-aperture, tapered silica fiber.
. The core diameter of the fiber-entrance surface is 940 μm; therefore, high transmission is expected. The fabricated fiber has an approximately 2:1 taper, with a tapered length of ~3 cm at the distal (output) end (fiber tapering by Silicon Lightwave Technology Inc.). Such a taper can be formed by heating a small section of a silica fiber and gently pulling the heat-softened-section part. The large-aperture input end and tapered output end improve the coupling efficiency and maximum power transmission and preserve moderate beam quality (lower M2 at fiber exit) for PIV applications. Furthermore, the delivered beam maintains low intensity in the non-tapered region (99.5% of the fiber length) and only becomes high intensity in the short tapered region; this fiber design minimizes nonlinear effects such as stimulated Brillouin scattering (SBS) that can potentially damage the fiber [22

22. A. V. Smith and B. T. Do, “Bulk and surface laser damage of silica by picosecond and nanosecond pulses at 1064 nm,” Appl. Opt. 47(26), 4812–4832 (2008). [CrossRef] [PubMed]

]. Although the beam quality can be improved by increasing the taper ratio, this would result in higher optical loss in the tapered region. For maintaining the losses at a low level, the taper transition should be very smooth (adiabatic tapering). In the present study, because of the limitation on the tapering machine, the longest taper length achieved was ~3 cm, and the resultant optical loss was ~0.2 dB (6%). The detailed fiber-transmission characteristics are discussed below.

2.2 High-power, tapered-fiber beam-delivery system

A schematic diagram of the optical system for coupling high-power, high-PRR, 532-nm ns laser beams through the tapered fiber is shown in Fig. 2
Fig. 2 Optical arrangement for conditioning the laser light and coupling it into the optical fiber.
. After the laser beam was passed through two 0.25° diffractive optical elements (DOEs) (HOlO/OR, RD-203-Q-Y-A and RPC Photonics, EDC-0.25), it was coupled into the fiber using an f = + 70-mm spherical lens. The fiber was placed in a six-axis kinematic mount, which was attached to a 1D translational stage that moved along the direction of the laser-beam propagation. The input end of the fiber was positioned at the focal point of the lens such that the beam filled ~80% of the core area. The use of DOEs not only smoothes the input-beam profile but also increases the number of spatial modes existing in the beam [15

15. D. P. Hand, J. D. Entwistle, R. R. J. Maier, A. Kuhn, C. A. Greated, and J. D. C. Jones, “Fibre optic beam delivery system for high peak power laser PIV illumination,” Meas. Sci. Technol. 10(3), 239–245 (1999). [CrossRef]

]. This setup minimizes the formation of a hot spot that can potentially damage the entrance surface of the fiber. It also prevents the occurrence of the self-focusing effect within the fiber. The intensity cross section of the focused spot produced at the fiber entrance surface is shown in Fig. 2.

2.3 Transmission characteristics of the tapered-fiber beam-delivery system

The experimental setup and the method employed for the fiber-transmission test are the same as those used for the fiber-transmission test described in Ref [23

23. P. S. Hsu, W. D. Kulatilaka, N. Jiang, J. R. Gord, and S. Roy, “Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy,” Appl. Opt. 51(18), 4047–4057 (2012). [CrossRef] [PubMed]

]. The fiber end surface had been polished by the vendor, and no marks were observed under a microscope at 100x magnification. In all of the fiber-transmission tests, the fibers were coiled at a bending radius of ~50 cm. The indicator of fiber damage was a sudden increase in fiber attenuation (decrease of transmission by 90%). To evaluate the capability of the tapered fiber to deliver high-power, high-PRR laser pulses, we studied the laser-induced damage threshold (LIDT), the long-term transmission behavior, and the beam quality.

2.3.1 LIDT

The lasers used for the LIDT study were a 10-Hz Nd:YAG laser (Spectra Physics, PRO 350) and a high-speed kHz-repetition-rate PIV laser (Quantronix, Dual-Hawk). All of the fiber damage was observed on the fiber entrance surface. As shown in Fig. 3
Fig. 3 Maximum output of 532-nm ns laser pulses from MSIFs (550-μm core) and tapered MSIFs with the use of DOE and bulk-optics (conventional) couplers as a function of pulse repetition rate.
, the use of the tapered fiber in conjunction with DOEs can significantly enhance the LIDT of the fiber. The LIDT (tested at 10 Hz) of the tapered-fiber beam-delivery system is approximately a factor of seven higher than that of the conventional fiber-optic beam-delivery system (standard 550-μm-core multimode step-index fiber (MSIF) with conventional coupling via bulk optics [11

11. P. S. Hsu, A. K. Patnaik, J. R. Gord, T. R. Meyer, W. D. Kulatilaka, and S. Roy, “Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows,” Exp. Fluids 49(4), 969–984 (2010). [CrossRef]

,23

23. P. S. Hsu, W. D. Kulatilaka, N. Jiang, J. R. Gord, and S. Roy, “Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy,” Appl. Opt. 51(18), 4047–4057 (2012). [CrossRef] [PubMed]

]). Because the large-aperture, tapered fiber is capable of coupling the full pulse energy output from the high-speed PIV laser (~7 mJ/pulse at 1 kHz, ~5.5 mJ/pulse at 5 kHz, ~3.3 mJ/pulse at 10 kHz), the LIDT of the silica fiber was tested with a 550-μm-core MSIF. In our experience the damage-threshold intensity of the two fibers should be very similar. When the input intensity of the 10-Hz (8-ns-duration), 1-kHz (95-ns-duration), 5-kHz (112-ns-duration), and 10-kHz (160-ns-duration) beams at the front surface of the silica fiber exceeded ~1 GW/cm2, ~24 MW/cm2, ~15 MW/cm2, and ~5 MW/cm2, respectively, fiber-surface catastrophic damage was observed, and the transmission decreased by 90% or more . The observed lower LIDT caused by the higher PRR pulses may be due to cumulative thermal effects in the fiber. Also note that the increase in the pulse duration of the higher PRR pulses may also decrease the LIDT (LIDT µ τ-0.5) [11

11. P. S. Hsu, A. K. Patnaik, J. R. Gord, T. R. Meyer, W. D. Kulatilaka, and S. Roy, “Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows,” Exp. Fluids 49(4), 969–984 (2010). [CrossRef]

,20

20. R. M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, 2003).

].

The coupling efficiency (i.e., the ratio of input-beam energy to output-beam energy) of the tapered fiber is ~80%, which is higher than that of the standard 550-μm-core MSIF (~70%). The 80% coupling efficiency is achieved under the condition of a 6% power penalty due to fiber tapering. The high coupling efficiency of the tapered fiber results from the large entrance aperture that enables coupling of higher-order modes. Such high coupling efficiency and high power transmission make the tapered fiber an ideal candidate for efficient, high-power, PIV beam delivery. The tapered-fiber beam-delivery system is capable of delivering >2.5 mJ (at 10 kHz) of pulse energy through a 6-m-long fiber. Such energy in our experience is sufficient to form a 10-cm-tall laser sheet for performing PIV in reacting flows with a good SNR.

2.3.2 Long-term transmission

Figure 4(a)
Fig. 4 (a) Long-time transmission for a 6-m-long tapered fiber. Energies of 5.3 mJ (solid line) and 2 mJ (dashed line) represent the initial energy of 1- and 10-kHz pulses, respectively, that are output from the fiber. (b) Fiber transmission of dual laser pulses at different pulse-separation time intervals, Δt. The pulse energy for each 1-kHz laser beam is ~2.7 mJ (total 5.4 mJ).
displays the typical long-term transmission of the 6-m-long tapered fiber with 1- and 10-kHz pulses for different transmission pulse energies. For both cases the transmission was maintained at about ~95% of the original value. Figure 4(b) shows that the tapered fiber is able to transmit stable dual laser pulses (E ~2.7 mJ/pulse) that are separated by a very short time interval (∆t ~2 μs). Thus, the designed tapered-fiber beam-delivery system can be used for PIV measurements in high-speed flows.

2.3.3 Output-beam quality

The quality of the fiber-transmitted laser beam is important to the fiber-coupled PIV system because the quality of the delivered beam must be such that the light can be focused into a thin laser sheet of sufficient extent to fill the area of interest. Typically, 600-μm or smaller core size fibers (NA of 0.22) are capable of providing moderate beam quality for PIV measurements [13

13. D. J. Anderson, J. D. C. Jones, W. J. Easson, and C. A. Greated, “Fiber-optic-bundle delivery system for high peak power laser particle image velocimetry illumination,” Rev. Sci. Instrum. 67(8), 2675–2679 (1996). [CrossRef]

,15

15. D. P. Hand, J. D. Entwistle, R. R. J. Maier, A. Kuhn, C. A. Greated, and J. D. C. Jones, “Fibre optic beam delivery system for high peak power laser PIV illumination,” Meas. Sci. Technol. 10(3), 239–245 (1999). [CrossRef]

]. Figure 5
Fig. 5 Thickness of light sheets generated by 550-μm-core MSIF, 940-μm-core MSIF, and tapered MSIF as a function of working distance. Shown in the inset is the beam- output profile from the tapered fiber.
shows that under the same optical arrangement, the beam output from the large-aperture, tapered fiber (entrance 940 μm and exit 550 μm) is capable of forming a thinner sheet than that from the 940-μm-core fiber. A similar order of beam-focusing ability was obtained for the tapered fiber and 550-μm-core fiber (M2 ~90). The taper of the fiber can decrease the core size and, hence, effectively reduce the number of modes that propagate through the fiber, leading to improved beam quality at the fiber exit [24

24. Y. Jung, Y. Jeong, G. Brambilla, and D. J. Richardson, “Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber,” Opt. Lett. 34(15), 2369–2371 (2009). [CrossRef] [PubMed]

,25

25. J. Kerttula, V. Filippov, V. Ustimchik, Y. Chamorovskiy, and O. G. Okhotnikov, “Mode evolution in long tapered fibers with high tapering ratio,” Opt. Express 20(23), 25461–25470 (2012). [CrossRef] [PubMed]

]. The beam quality can be further improved by means of a higher tapering ratio [25

25. J. Kerttula, V. Filippov, V. Ustimchik, Y. Chamorovskiy, and O. G. Okhotnikov, “Mode evolution in long tapered fibers with high tapering ratio,” Opt. Express 20(23), 25461–25470 (2012). [CrossRef] [PubMed]

]. By increasing the tapering ratio of the current fiber to 6:1 (core size ~150 μm), the estimated beam quality M2 can be improved to ~20, which is ideal for PIV applications [15

15. D. P. Hand, J. D. Entwistle, R. R. J. Maier, A. Kuhn, C. A. Greated, and J. D. C. Jones, “Fibre optic beam delivery system for high peak power laser PIV illumination,” Meas. Sci. Technol. 10(3), 239–245 (1999). [CrossRef]

]. The increase in tapering ratio will result in an increase in optical loss, but this can be minimized by making the taper transition very smooth (adiabatic tapering) [24

24. Y. Jung, Y. Jeong, G. Brambilla, and D. J. Richardson, “Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber,” Opt. Lett. 34(15), 2369–2371 (2009). [CrossRef] [PubMed]

,25

25. J. Kerttula, V. Filippov, V. Ustimchik, Y. Chamorovskiy, and O. G. Okhotnikov, “Mode evolution in long tapered fibers with high tapering ratio,” Opt. Express 20(23), 25461–25470 (2012). [CrossRef] [PubMed]

]. Also, a nearly top-hat beam profile was acquired using the tapered fiber, as shown in the inset of Fig. 5. Such a beam profile is highly desirable for PIV applications that require homogenous laser sheets for uniform illumination of the tracer particles. Recently, Yalin et al. proposed to use large-clad fibers to improve the beam quality of the fiber output [26

26. S. Hurand, L. A. Chauny, H. El-Rabii, S. Joshi, and A. P. Yalin, “Mode coupling and output beam quality of 100-400 μm core silica fibers,” Appl. Opt. 50(4), 492–499 (2011). [CrossRef] [PubMed]

,27

27. F. Loccisano, S. Joshi, I. S. Franka, Z. Yin, W. R. Lempert, and A. P. Yalin, “Fiber-coupled ultraviolet planar laser-induced fluorescence for combustion diagnostics,” Appl. Opt. 51(27), 6691–6699 (2012). [CrossRef] [PubMed]

]. We are in the process of exploring large-clad fibers in conjunction with fiber tapering technique for generating high-output beam quality (low M2) to improve the spatial resolution of the PIV measurements.

3. Fiber-coupled, 10-kHz PIV measurements

The experimental apparatus for the fiber-coupled, high-speed PIV system is shown in Fig. 6
Fig. 6 Schematic of fiber-coupled, high-speed PIV system.
. The 10-kHz, 160-ns-duration, 532-nm laser pulses were generated by frequency doubling the output of a diode-pumped Nd:YAG laser (Quantronix, Dual-Hawk). The separation time between the two PIV pulses was 20 μs. The laser-to-fiber coupling employed for the fiber-coupled PIV system is the same as that used for the fiber-transmission test discussed in Sect. 2. The laser beam was coupled into the 6-m-long tapered fiber, and the energy of each pulse, as measured at the fiber output, was ~2.5 mJ. The output of the fiber was collimated by an f = + 50-mm spherical lens and focused onto a probe volume using an f = + 100-mm, 50.8-mm-square cylindrical lens, which generated a laser sheet that was ~30 mm tall with a thickness of ~1 mm at the probe volume. Collection of the scattered light from the seed particles was performed using a dual-frame CMOS camera (Photron, SA5), coupled with an 85-mm f/1.8 lens. A 3-nm narrow-bandpass filter centered at 532 nm (Semrock, LL01-532-50) was employed to eliminate unwanted signals originating from background sources and flame emission. The image pairs were processed using LaVision DaVis v8.03 commercial PIV software. As a simple demonstration, we used the delivery system to obtain PIV images of a laboratory-based propane–air flame that was seeded with 1-μm Al2O3 particles. The flame employed for the PIV studies was a premixed propane–air flame with an equivalence ratio ϕ = 1.06 that was stabilized over a 30-mm-diameter home-built burner having an adiabatic flame temperature of ~2000 K. The detailed features of the burner are described in Ref [4

4. J. Schmidt, S. Kostka, A. Lynch, and B. Ganguly, “Simultaneous particle image velocimetry and chemiluminescence visualization of millisecond-pulsed current–voltage-induced perturbations of a premixed propane/air flame,” Exp. Fluids 51(3), 657–665 (2011). [CrossRef]

]. To create a controlled transient event in the flame, a millisecond-time-scale high voltage was applied to disturb the flame.

To examine the impact of fiber delivery on the PIV measurements, we acquired velocity-vector images of a steady flow (i.e., no applied voltage) with the tapered-fiber-delivered laser sheet and with a free-space laser sheet that had very similar properties. Figure 7
Fig. 7 Sample image showing the PIV correlation obtained with each delivery system in a steady, premixed propane–air flow. Data collected with the fiber-delivered system are shown in (a) and those collected with the directly delivered system are shown in (b).
shows that a similar order of measurement accuracy was obtained with and without fiber coupling. The slight velocity-profile difference for the two cases may be the result of clogging of the burner by seed particles, which affects the flow-velocity patterns.

To create a turbulent flame, we added an anode ~13 mm above the burner surface (cathode) and applied a high DC voltage of ~2kV at a frequency of ~15 Hz to disturb the flame. The strong electric field alters the ionic structure of the propane–air flame, which results in a phase transition from a stable, laminar flame to a highly unstable flame as well as a modification of the flame speed. Partial sequences of 10-kHz PIV images and velocity-vector maps for the electric-field-induced turbulent flames are shown in Fig. 8
Fig. 8 Partial, instantaneous velocity-vector maps acquired from an atmospheric-pressure, turbulent propane–air flame on a burner being pulsated by an applied DC voltage of + 2 kV at a frequency of ~15 Hz.
. Areas near the flame top show a small “hole” where no cross-correlation data exist. This hole in the PIV data is the result of the anode having blocked the seed particles. The acquired PIV data exhibit time-dependent velocity profiles that are very similar to those previously observed from the direct-beam measurements reported in Ref [4

4. J. Schmidt, S. Kostka, A. Lynch, and B. Ganguly, “Simultaneous particle image velocimetry and chemiluminescence visualization of millisecond-pulsed current–voltage-induced perturbations of a premixed propane/air flame,” Exp. Fluids 51(3), 657–665 (2011). [CrossRef]

].

4. Conclusions

Fiber-coupled, 10-kHz PIV imaging that employs a large-aperture, tapered step-index fiber has been demonstrated in turbulent reacting flows. A similar order of measurement accuracy was obtained with and without fiber coupling. The tapered fiber is capable of reliably and efficiently delivering the laser energy at a kHz PRR required for performing high-speed PIV measurements. The maximum energy that can be transmitted by the tapered-fiber beam-delivery system is greater than that possible with a conventional fiber-optic beam-delivery system, and the quality of the delivered light sheet is superior to that obtained from a single large-core fiber of power-handling capacity equivalent to that of the tapered fiber. This achievement together with future developments, such as an image fiber bundle for PIV image collection, will constitute a major step in the transition of the PIV diagnostic tool from research laboratories to reacting-flow facilities of practical interest.

Acknowledgments

The authors gratefully acknowledge useful discussions with Mr. Jacob Schmidt of Spectral Energies, LLC. Funding for this research was provided by the Air Force Research Laboratory under Contract No. FA8650-12-C-2200 and by the Air Force Office of Scientific Research (Dr. Chiping Li, Program Manager).

References and links

1.

R. J. Adrian, “Twenty years of particle image velocimetry,” Exp. Fluids 39(2), 159–169 (2005). [CrossRef]

2.

T. O. H. Charrett, S. W. James, and R. P. Tatam, “Optical fibre laser velocimetry: a review,” Meas. Sci. Technol. 23(3), 032001 (2012). [CrossRef]

3.

D. L. Wisman, S. D. Marcum, and B. N. Ganguly, “Electrical control of the thermodiffusive instability in premixed propane-air flames,” Combust. Flame 151(4), 639–648 (2007). [CrossRef]

4.

J. Schmidt, S. Kostka, A. Lynch, and B. Ganguly, “Simultaneous particle image velocimetry and chemiluminescence visualization of millisecond-pulsed current–voltage-induced perturbations of a premixed propane/air flame,” Exp. Fluids 51(3), 657–665 (2011). [CrossRef]

5.

S. D. Marcum and B. N. Ganguly, “Electric-field-induced flame speed modification,” Combust. Flame 143(1-2), 27–36 (2005). [CrossRef]

6.

P. S. Hsu, N. Jiang, J. R. Gord, and S. Roy, “Fiber-coupled, 10 kHz simultaneous OH planar laser-induced fluorescence/particle-image velocimetry,” Opt. Lett. 38(2), 130–132 (2013). [CrossRef]

7.

T. R. Meyer, G. J. Fiechtner, S. P. Gogineni, J. C. Rolon, C. D. Carter, and J. R. Gord, “Simultaneous PLIF/PIV investigation of vortex-induced annular extinction in H2-air counterflow diffusion flames,” Exp. Fluids 36(2), 259–267 (2004). [CrossRef]

8.

N. Jiang, M. Webster, W. R. Lempert, J. D. Miller, T. R. Meyer, C. B. Ivey, and P. M. Danehy, “MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel,” Appl. Opt. 50(4), A20–A28 (2011). [CrossRef] [PubMed]

9.

N. Jiang, J. Bruzzese, R. Patton, J. Sutton, R. Yentsch, D. V. Giatonde, W. R. Lempert, J. D. Miller, T. R. Meyer, R. Parker, T. Wadham, M. Holden, and P. M. Danehy, “NO PLIF imaging in the CUBRC 48-inch shock tunnel,” Exp. Fluids 53(6), 1637–1646 (2012). [CrossRef]

10.

A. A. P. Boechat, D. Su, D. R. Hall, and J. D. C. Jones, “Bend loss in large core multimode optical fiber beam delivery systems,” Appl. Opt. 30(3), 321–327 (1991). [CrossRef] [PubMed]

11.

P. S. Hsu, A. K. Patnaik, J. R. Gord, T. R. Meyer, W. D. Kulatilaka, and S. Roy, “Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows,” Exp. Fluids 49(4), 969–984 (2010). [CrossRef]

12.

D. J. Anderson, R. D. Morgan, D. R. McCluskey, J. D. C. Jones, W. J. Easson, and C. A. Greated, “An optical fiber delivery system for pulsed laser particle image velocimetry illumination,” Meas. Sci. Technol. 6(6), 809–814 (1995). [CrossRef]

13.

D. J. Anderson, J. D. C. Jones, W. J. Easson, and C. A. Greated, “Fiber-optic-bundle delivery system for high peak power laser particle image velocimetry illumination,” Rev. Sci. Instrum. 67(8), 2675–2679 (1996). [CrossRef]

14.

J. Estevadeordal, T. R. Meyer, S. P. Gogineni, M. D. Polanka, and J. R. Gord, “Development of a fiber-optic PIV system for turbomachinery applications,” in Proceedings of 43rd AIAA Aerospace Sciences Meeting and Exhibit, AIAA-2005-0038 (2005).

15.

D. P. Hand, J. D. Entwistle, R. R. J. Maier, A. Kuhn, C. A. Greated, and J. D. C. Jones, “Fibre optic beam delivery system for high peak power laser PIV illumination,” Meas. Sci. Technol. 10(3), 239–245 (1999). [CrossRef]

16.

J. P. Parry, J. D. Shephard, M. J. Thomson, M. R. Taghizadeh, J. D. C. Jones, and D. P. Hand, “Optical fiber array for the delivery of high peak-power laser pulses for fluid flow measurements,” Appl. Opt. 46(17), 3432–3438 (2007). [CrossRef] [PubMed]

17.

R. A. Robinson and I. K. Ilev, “Design and optimization of a flexible high-peak-power laser-to-fiber coupled illumination system used in digital particle image velocimetry,” Rev. Sci. Instrum. 75(11), 4856–4862 (2004). [CrossRef]

18.

H. Gebauer, M. Jupe, G. Bataviciute, D. Ristau, and R. Kling, “Measurement of laser power resistance of fibers for PIV systems,” Proc. SPIE 7132, 713219, 713219-8 (2008). [CrossRef]

19.

T. J. Stephens, M. J. Haste, D. P. Towers, M. J. Thomson, M. R. Taghizadeh, J. D. C. Jones, and D. P. Hand, “Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement,” Appl. Opt. 42(21), 4307–4314 (2003). [CrossRef] [PubMed]

20.

R. M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, 2003).

21.

J. Schmidt, S. Kostka, S. Roy, J. R. Gord, and B. Ganguly, “KHz-rate particle-image velocimetry of induced instability in premixed propane/air flame by millisecond pulsed current–voltage,” Combust. Flame 160(2), 276–284 (2013). [CrossRef]

22.

A. V. Smith and B. T. Do, “Bulk and surface laser damage of silica by picosecond and nanosecond pulses at 1064 nm,” Appl. Opt. 47(26), 4812–4832 (2008). [CrossRef] [PubMed]

23.

P. S. Hsu, W. D. Kulatilaka, N. Jiang, J. R. Gord, and S. Roy, “Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy,” Appl. Opt. 51(18), 4047–4057 (2012). [CrossRef] [PubMed]

24.

Y. Jung, Y. Jeong, G. Brambilla, and D. J. Richardson, “Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber,” Opt. Lett. 34(15), 2369–2371 (2009). [CrossRef] [PubMed]

25.

J. Kerttula, V. Filippov, V. Ustimchik, Y. Chamorovskiy, and O. G. Okhotnikov, “Mode evolution in long tapered fibers with high tapering ratio,” Opt. Express 20(23), 25461–25470 (2012). [CrossRef] [PubMed]

26.

S. Hurand, L. A. Chauny, H. El-Rabii, S. Joshi, and A. P. Yalin, “Mode coupling and output beam quality of 100-400 μm core silica fibers,” Appl. Opt. 50(4), 492–499 (2011). [CrossRef] [PubMed]

27.

F. Loccisano, S. Joshi, I. S. Franka, Z. Yin, W. R. Lempert, and A. P. Yalin, “Fiber-coupled ultraviolet planar laser-induced fluorescence for combustion diagnostics,” Appl. Opt. 51(27), 6691–6699 (2012). [CrossRef] [PubMed]

OCIS Codes
(060.2270) Fiber optics and optical communications : Fiber characterization
(060.2310) Fiber optics and optical communications : Fiber optics
(120.1740) Instrumentation, measurement, and metrology : Combustion diagnostics
(120.7250) Instrumentation, measurement, and metrology : Velocimetry

ToC Category:
Instrumentation, Measurement, and Metrology

History
Original Manuscript: December 19, 2012
Revised Manuscript: January 25, 2013
Manuscript Accepted: January 27, 2013
Published: February 5, 2013

Citation
Paul S. Hsu, Sukesh Roy, Naibo Jiang, and James R. Gord, "Large-aperture, tapered fiber–coupled, 10-kHz particle-image velocimetry," Opt. Express 21, 3617-3626 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-3-3617


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References

  1. R. J. Adrian, “Twenty years of particle image velocimetry,” Exp. Fluids39(2), 159–169 (2005). [CrossRef]
  2. T. O. H. Charrett, S. W. James, and R. P. Tatam, “Optical fibre laser velocimetry: a review,” Meas. Sci. Technol.23(3), 032001 (2012). [CrossRef]
  3. D. L. Wisman, S. D. Marcum, and B. N. Ganguly, “Electrical control of the thermodiffusive instability in premixed propane-air flames,” Combust. Flame151(4), 639–648 (2007). [CrossRef]
  4. J. Schmidt, S. Kostka, A. Lynch, and B. Ganguly, “Simultaneous particle image velocimetry and chemiluminescence visualization of millisecond-pulsed current–voltage-induced perturbations of a premixed propane/air flame,” Exp. Fluids51(3), 657–665 (2011). [CrossRef]
  5. S. D. Marcum and B. N. Ganguly, “Electric-field-induced flame speed modification,” Combust. Flame143(1-2), 27–36 (2005). [CrossRef]
  6. P. S. Hsu, N. Jiang, J. R. Gord, and S. Roy, “Fiber-coupled, 10 kHz simultaneous OH planar laser-induced fluorescence/particle-image velocimetry,” Opt. Lett.38(2), 130–132 (2013). [CrossRef]
  7. T. R. Meyer, G. J. Fiechtner, S. P. Gogineni, J. C. Rolon, C. D. Carter, and J. R. Gord, “Simultaneous PLIF/PIV investigation of vortex-induced annular extinction in H2-air counterflow diffusion flames,” Exp. Fluids36(2), 259–267 (2004). [CrossRef]
  8. N. Jiang, M. Webster, W. R. Lempert, J. D. Miller, T. R. Meyer, C. B. Ivey, and P. M. Danehy, “MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel,” Appl. Opt.50(4), A20–A28 (2011). [CrossRef] [PubMed]
  9. N. Jiang, J. Bruzzese, R. Patton, J. Sutton, R. Yentsch, D. V. Giatonde, W. R. Lempert, J. D. Miller, T. R. Meyer, R. Parker, T. Wadham, M. Holden, and P. M. Danehy, “NO PLIF imaging in the CUBRC 48-inch shock tunnel,” Exp. Fluids53(6), 1637–1646 (2012). [CrossRef]
  10. A. A. P. Boechat, D. Su, D. R. Hall, and J. D. C. Jones, “Bend loss in large core multimode optical fiber beam delivery systems,” Appl. Opt.30(3), 321–327 (1991). [CrossRef] [PubMed]
  11. P. S. Hsu, A. K. Patnaik, J. R. Gord, T. R. Meyer, W. D. Kulatilaka, and S. Roy, “Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows,” Exp. Fluids49(4), 969–984 (2010). [CrossRef]
  12. D. J. Anderson, R. D. Morgan, D. R. McCluskey, J. D. C. Jones, W. J. Easson, and C. A. Greated, “An optical fiber delivery system for pulsed laser particle image velocimetry illumination,” Meas. Sci. Technol.6(6), 809–814 (1995). [CrossRef]
  13. D. J. Anderson, J. D. C. Jones, W. J. Easson, and C. A. Greated, “Fiber-optic-bundle delivery system for high peak power laser particle image velocimetry illumination,” Rev. Sci. Instrum.67(8), 2675–2679 (1996). [CrossRef]
  14. J. Estevadeordal, T. R. Meyer, S. P. Gogineni, M. D. Polanka, and J. R. Gord, “Development of a fiber-optic PIV system for turbomachinery applications,” in Proceedings of 43rd AIAA Aerospace Sciences Meeting and Exhibit, AIAA-2005-0038 (2005).
  15. D. P. Hand, J. D. Entwistle, R. R. J. Maier, A. Kuhn, C. A. Greated, and J. D. C. Jones, “Fibre optic beam delivery system for high peak power laser PIV illumination,” Meas. Sci. Technol.10(3), 239–245 (1999). [CrossRef]
  16. J. P. Parry, J. D. Shephard, M. J. Thomson, M. R. Taghizadeh, J. D. C. Jones, and D. P. Hand, “Optical fiber array for the delivery of high peak-power laser pulses for fluid flow measurements,” Appl. Opt.46(17), 3432–3438 (2007). [CrossRef] [PubMed]
  17. R. A. Robinson and I. K. Ilev, “Design and optimization of a flexible high-peak-power laser-to-fiber coupled illumination system used in digital particle image velocimetry,” Rev. Sci. Instrum.75(11), 4856–4862 (2004). [CrossRef]
  18. H. Gebauer, M. Jupe, G. Bataviciute, D. Ristau, and R. Kling, “Measurement of laser power resistance of fibers for PIV systems,” Proc. SPIE7132, 713219, 713219-8 (2008). [CrossRef]
  19. T. J. Stephens, M. J. Haste, D. P. Towers, M. J. Thomson, M. R. Taghizadeh, J. D. C. Jones, and D. P. Hand, “Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement,” Appl. Opt.42(21), 4307–4314 (2003). [CrossRef] [PubMed]
  20. R. M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, 2003).
  21. J. Schmidt, S. Kostka, S. Roy, J. R. Gord, and B. Ganguly, “KHz-rate particle-image velocimetry of induced instability in premixed propane/air flame by millisecond pulsed current–voltage,” Combust. Flame160(2), 276–284 (2013). [CrossRef]
  22. A. V. Smith and B. T. Do, “Bulk and surface laser damage of silica by picosecond and nanosecond pulses at 1064 nm,” Appl. Opt.47(26), 4812–4832 (2008). [CrossRef] [PubMed]
  23. P. S. Hsu, W. D. Kulatilaka, N. Jiang, J. R. Gord, and S. Roy, “Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy,” Appl. Opt.51(18), 4047–4057 (2012). [CrossRef] [PubMed]
  24. Y. Jung, Y. Jeong, G. Brambilla, and D. J. Richardson, “Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber,” Opt. Lett.34(15), 2369–2371 (2009). [CrossRef] [PubMed]
  25. J. Kerttula, V. Filippov, V. Ustimchik, Y. Chamorovskiy, and O. G. Okhotnikov, “Mode evolution in long tapered fibers with high tapering ratio,” Opt. Express20(23), 25461–25470 (2012). [CrossRef] [PubMed]
  26. S. Hurand, L. A. Chauny, H. El-Rabii, S. Joshi, and A. P. Yalin, “Mode coupling and output beam quality of 100-400 μm core silica fibers,” Appl. Opt.50(4), 492–499 (2011). [CrossRef] [PubMed]
  27. F. Loccisano, S. Joshi, I. S. Franka, Z. Yin, W. R. Lempert, and A. P. Yalin, “Fiber-coupled ultraviolet planar laser-induced fluorescence for combustion diagnostics,” Appl. Opt.51(27), 6691–6699 (2012). [CrossRef] [PubMed]

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