High-Speed Local Heating Microdevices Enable Analysis of Biomolecular Behavior on Millisecond Time Scale

Long-lasting emission from femtosecond excitation of nitrogen-based flows shows promise as a useful mechanism for a molecular tagging velocimetry instrument. The technique, known as femtosecond laser electronic excitation tagging (FLEET), was invented at Princeton a decade ago and has quickly been adopted and used in a variety of high-speed ground test flow facilities. The short temporal scales offered by femtosecond amplifiers permit nonresonant multiphoton excitation, dissociation, and weak ionization of a gaseous medium near the beam's focus without the generation of a laser spark observed with nanosecond systems. Gated, intensified imaging of the resulting emission enables the tracking of tagged molecules, thereby measuring one to three components of velocity. Effects of local heating and acoustic disturbances can be mitigated with the selection of a shorter-wavelength excitation source. This review surveys the development of FLEET over the decade since its inception, as it has been implemented in several test facilities to make accurate, precise, and seedless velocimetry measurements for studying complex high-speed flows.

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Motion of Descending Solid Particles and Local Flow Around the Particles in Downward Turbulent Water Duct Flow (Keynote)

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-09021 ◽

2011 ◽

Author(s):

Yoshimichi Hagiwara ◽

Hideto Fujii ◽

Katsutoshi Sakurai ◽

Takashi Kuroda ◽

Atsuhide Kitagawa

Keyword(s):

Reynolds Number ◽

Time Scale ◽

High Speed ◽

Fluid Velocity ◽

Stokes Number ◽

Solid Particles ◽

Duct Flow ◽

Local Flow ◽

Particle Reynolds Number ◽

Turbulent Water

The Stokes number, the ratio of the particle time scale to flow time scale, is a promising quantity for estimating changes in statistics of turbulence due to particles. First, we explored the Stokes numbers in some recent studies. Secondly, we discussed the results of our direct numerical simulation for turbulent flow with a high-density particle in a vertical duct. In the discussion, we defined the particle Reynolds number from the mean fluid velocity in the near-particle region at any time. We evaluated a new local Stokes number for the particle. It is found that the Stokes number is effective for the prediction of the distance between the particle center and one wall. Finally, we carried out experiments for turbulent water flow with aluminum balls of 1 mm in diameter in a vertical channel. The motions of aluminum balls and tracer particles in the flow were captured with a high-speed video camera. We found that the experimental results for the time changes in the wall-normal distance of the ball and the particle Reynolds number for the ball are similar to the predicted results.

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Interplanetary Response to Solar Long Time-Scale Phenomena

Symposium - International Astronomical Union ◽

10.1017/s0074180900067413 ◽

1980 ◽

Vol 91 ◽

pp. 105-125

Author(s):

C. D'Uston ◽

J. M. Bosqued

Keyword(s):

Solar Wind ◽

Time Scale ◽

High Speed ◽

Coronal Holes ◽

Observational Evidence ◽

Solar Wind Flow ◽

Speed Solar Wind ◽

Long Time ◽

Outer Corona ◽

High Speed Solar Wind

In this paper, we briefly review the experimental knowledge gained in the recent years on the interplanetary response to solar long-time scale phenomena such as the coronal magnetic structure and its evolution. Observational evidence that solar wind flow in the outer corona comes from the unipolar diverging magnetic regions of the photosphere is discussed along with relations to coronal holes. High-speed solar wind streams observed within the boundary of interplanetary magnetic sectors are associated with these structures. Their boundaries appear as very narrow velocity shears.

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