Motion of tracer particles in supersonic flows

Tedeschi, G.; Gouin, Henri; Elena, M.

doi:10.1007/s003480050291

Cited by 97 publications

(44 citation statements)

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“…In extreme cases the latter effect might prevent any PIV measurements due to the complete absence of particle tracers over large regions of the flow domain such as in the core of vortices and in separated flow regions. Accounts of previous studies dealing with the determination of the unsteady motion of small spherical particles in fluid flows can be found in Mei (1996), providing a general mathematical review; whereas a specific study in the high-speed regime is given by Tedeschi et al (1999). The problem of the particle motion in turbulent compressible shear layers was treated numerically by Samimy and Lele (1991) concluding that an accurate tracing requires that the particles Stokes number should not exceed 0.1.…”

Section: Introductionmentioning

confidence: 99%

Particle tracer response across shocks measured by PIV

et al. 2010

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The experimental approach used for the evaluation of the particle response time across a stationary shock wave is assessed by means of PIV measurements. The study focuses on the experimental requirements for a reliable and unbiased measurement of the particle response time s p and length n p based on a single-exponent decaying law. A numerical simulation of the particle response experiment returns the parameters governing the measurement: namely the normalized spatial and temporal resolution, shock strength, and digital resolution. Representing the velocity decay in logarithmic coordinates it is shown that measurements performed with laser pulse separation time up to s p and interrogation window up to n p still yield unbiased results for the particle response. A set of experiments on the particle response across a planar oblique shock wave was conducted to verify the results from the numerical assessment. Liquid droplets of DEHS and solid tracer particles of silicon and titanium dioxide with different primary crystal size are compared. The resulting temporal response ranges from 2 to 3 ls, corresponding to values commonly reported in literature, to almost 0.3 ls when particles are properly dehydrated and a filter is applied before injection into the wind tunnel. It is the first experimental evidence of particle tracers with a measured response time lower than 0.4 ls. The same procedure is applied to attempt the measurement of individual particle tracers by particle tracking velocimetry to estimate the spread in the distribution of tracer time response. The latter analysis is limited by the particle image tracking precision error, which biases the results introducing a wider broadening of the particle velocity distribution.

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Section: Introductionmentioning

confidence: 99%

Particle tracer response across shocks measured by PIV

et al. 2010

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“…Both include the effect of compressibility and variable Knudsen number. The TAU module was validated with literature data from Tedeschi et al (1999). With the presented module, single particle trajectories, as well as wall particle impingement points and particle density distributions along the conical flow field, can be modeled, extracted and compared to experimental data.…”

Section: Particle Module Extensionsmentioning

confidence: 99%

“…Since this module is designed for sub-to transonic flows, it was necessary to extend the implementation of the equations of motion to cover compressible, rarefied conditions. This included implementation of suitable drag coefficient models, chosen with the Tedeschi (Tedeschi et al 1999) and Henderson model (implemented as given in Thomas 1991). Both include the effect of compressibility and variable Knudsen number.…”

Section: Particle Module Extensionsmentioning

confidence: 99%

Experiments on a smooth wall hypersonic boundary layer at Mach 6

2018

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The turbulent boundary layer along the surface of high-speed vehicles drives shear stress and heat flux. Although essential to the vehicle design, the understanding of compressible turbulent boundary layers at high Mach numbers is limited due to the lack of available data. This is particularly true if the surface is rough, which is typically the case for all technical surfaces. To validate a methodological approach, as initial step, smooth wall experiments were performed. A hypersonic turbulent boundary layer at Ma = 6 ( Ma e = 5.4 ) along a 7• sharp cone model at low Reynolds numbers Re ≈ 3000 was characterized. The mean velocities in the boundary layer were acquired by means of Pitot pressure and particle image velocimetry (PIV) measurements. Furthermore, the PIV data were used to extract turbulent intensities along the profile. The mean velocities in the boundary layer agree with numerical data, independent of the measurement technique. Based on the profile data, three different approaches to extract the skin friction velocity were applied and show favorable comparison to literature and numerical data. The extracted values were used for inner and outer scaling of the van Driest transformed velocity profiles which are in good agreement to incompressible theoretical data. Morkovin scaled turbulent intensities show ambiguous results compared to literature data which may be influenced by inflow turbulence level, particle lag and other measurement uncertainties.

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“…Mach Number corrections are included in the ρ/ρ w term, which is given below: (24) 3. Tedeschi et al (1999). This work was done with very small droplets, on the order of 1 µm.…”

Section: Particle Drag Lawsmentioning

confidence: 99%

Direct Comparison of Particle-Tracking and Sectional Approaches for Shock Driven Flows

Schwer¹,

Kailasanath²

2009

International Journal of Spray and Combustion Dynamics

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Dispersed-phase flows are important for a wide variety of problems, and several numerical approaches for the solution of dispersed-phase flows have been proposed and implemented in the past. The present research implements two popular approaches to dispersed-phase flows: the Lagrangian particle-tracking approach and the Eulerian sectional approach. A direct comparison between the two methods is made for a range of shock driven seeded flow-fields. First, different drag models are investigated using the particle-tracking method for a range of conditions, and then direct comparisons between the two methods are made for shock speed attenuation and shock-wave profiles. In addition, resolution requirements are investigated to determine the number of sections and the number of particles required to obtain good agreement between the methods, and then two-dimensional simulations are done to investigate the effect of each method on more complicated flow-fields. Results showed both methods can be used to obtain very similar results, although each method has benefits and drawbacks. The glass particles were then replaced with water droplets, and the effect of vaporization and droplet breakup were then investigated. Although vaporization was well represented with the sectional approach, different droplet breakup models had to be implemented for the different approaches, with some significant differences in the resultant droplet distributions. The reason for this is that breakup models require a droplet deformation time before breaking up, and thus a droplet history. This droplet history is difficult to implement in sectional approaches (and Eulerian methods in general), and so the breakup model must be changed. Similar profiles could be reproduced with the sectional method, but significant differences persisted. The results did show, however, that the Eulerian sectional approach is a viable method for computing complex, multi-dimensional flow-fields and can provide significant numerical advantages when compared with Lagrangian particle-tracking methods, especially in flooded environments such as examined here.

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Motion of tracer particles in supersonic flows

Cited by 97 publications

References 0 publications

Particle tracer response across shocks measured by PIV

Particle tracer response across shocks measured by PIV

Experiments on a smooth wall hypersonic boundary layer at Mach 6

Direct Comparison of Particle-Tracking and Sectional Approaches for Shock Driven Flows

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