A Method to Obtain Planar Mixture Fraction Statistics in Turbulent Flows Seeded With Tracer Particles

2011 ◽  
Author(s):  
M. Pernpeintner ◽  
M. Lauer ◽  
C. Hirsch ◽  
T. Sattelmayer
Keyword(s):  
Turbulent Flows ◽  
Particle Density ◽  
Scattered Light ◽  
Mixture Fraction ◽  
Light Sheet ◽  
Piv Measurements ◽  
Experimental Procedure ◽  
Free Jet ◽  
Tracer Particles ◽  
Inversion Procedure

We present a new method to obtain the mixture fraction probability density functions (PDF) of turbulent mixing in planar sections of a flow field which is seeded with PIV tracer particles. We derive a model how the observed scattered light obtained locally in a laser light sheet results from the local mixture fraction PDF and the particle density PDF. From this model we develop an analytical as well as a numerical inversion procedure that allows the deconvolution of the mixture fraction PDF from the light intensity PDF using the measured seeding PDF. We explain the experimental procedure necessary to apply the new technique on the example of a turbulent free jet. The results of both the analytical and the numerical method are compared and the method is then validated against the literature data. Since the method seems applicable whenever PIV measurements can be made it bears high potential for combustor development as it allows to obtain mixing statistics using basically the same measurement hardware.

scholarly journals Simultaneous temperature, mixture fraction and velocity imaging in turbulent flows using thermographic phosphor tracer particles

2012 ◽  
Vol 20 (20) ◽  
pp. 22118 ◽  
Author(s):  
Benoit Fond ◽  
Christopher Abram ◽  
Andrew L Heyes ◽  
Andreas M Kempf ◽  
Frank Beyrau
Keyword(s):  
Turbulent Flows ◽  
Mixture Fraction ◽  
Velocity Imaging ◽  
Tracer Particles ◽  
Thermographic Phosphor

A General Closure Model for the Time-Averaged Radiative Transfer Equation in Turbulent Flows

2010 ◽  
Author(s):  
Pedro J. Coelho
Keyword(s):  
Radiative Transfer ◽  
Turbulent Flows ◽  
Radiation Intensity ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Mixture Fraction ◽  
Joint Probability ◽  
Turbulent Fluctuations ◽  
Proposed Model ◽  
Local Properties

The time-averaged form of the radiative transfer equation (RTE) includes emission and absorption correlations that need to be modeled. There is no general formulation to estimate the absorption coefficient-radiation intensity correlation, which is generally neglected (optically thin fluctuation approximation–OTFA). Here, a model to compute this correlation, as well as the other correlations in the time-averaged form of the RTE, is described. The formulation is based on the solution of two additional differential equations. The unclosed correlations in these equations are estimated assuming that the joint probability density function (pdf) of the radiation intensity and mixture fraction is a two-dimensional clipped Gaussian distribution. The model is applied to a turbulent jet diffusion flame, and a preliminary assessment of the model is reported. It is shown that fluctuations of the radiation intensity, caused by turbulence, imply the existence of a correlation between the radiation intensity and local properties. The assumption of the shape of the joint pdf of mixture fraction and radiation intensity yields satisfactory predictions if the turbulent fluctuations are moderate, but becomes inaccurate near the flame edge where turbulent fluctuations are very large. Nevertheless, the present results suggest that the proposed model may yield better predictions than the OTFA.

scholarly journals PIV measurements of turbulent flows in a 61-pin wire-wrapped hexagonal fuel bundle

2017 ◽  
Vol 65 ◽  
pp. 47-59 ◽  
Author(s):  
Thien Nguyen ◽  
Nolan Goth ◽  
Philip Jones ◽  
Saya Lee ◽  
Rodolfo Vaghetto ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Piv Measurements ◽  
Fuel Bundle

PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel

2011 ◽  
Author(s):  
Takayuki Mori ◽  
Risa Kimoto ◽  
Kenji Naganuma
Keyword(s):  
Flow Field ◽  
Velocity Profiles ◽  
Marine Propeller ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Tip Vortices ◽  
Systems Research ◽  
Tracer Particles ◽  
Cavitation Tunnel ◽  
Blade Tip

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

Evaluation of Turbulent Kinetic Energy Dissipation Rate in a Free Jet Flow from PIV Measurements

2012 ◽  
Vol 7 (1) ◽  
pp. 53-69
Author(s):  
Vladimir Dulin ◽  
Yuriy Kozorezov ◽  
Dmitriy Markovich
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
Turbulent Velocity ◽  
Small Scale ◽  
Velocity Fluctuations ◽  
Piv Measurements ◽  
Free Jet

The present paper reports PIV (Particle Image Velocimetry) measurements of turbulent velocity fluctuations statistics in development region of an axisymmetric free jet (Re = 28 000). To minimize measurement uncertainty, adaptive calibration, image processing and data post-processing algorithms were utilized. On the basis of theoretical analysis and direct measurements, the paper discusses effect of PIV spatial resolution on measured statistical characteristics of turbulent fluctuations. Underestimation of the second-order moments of velocity derivatives and of the turbulent kinetic energy dissipation rate due to a finite size of PIV interrogation area and finite thickness of laser sheet was analyzed from model spectra of turbulent velocity fluctuations. The results are in a good agreement with the measured experimental data. The paper also describes performance of possible ways to account for unresolved small-scale velocity fluctuations in PIV measurements of the dissipation rate. In particular, a turbulent viscosity model can be efficiently used to account for the unresolved pulsations in a free turbulent flow

Thermal Characterization of a Turbulent Free Jet With Planar Laser-Induced Fluorescence

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Sara Seitz ◽  
Lesley M. Wright
Keyword(s):  
Thermal Structure ◽  
Thermal Characterization ◽  
Light Sheet ◽  
Calibration Procedure ◽  
Laser Induced Fluorescence ◽  
Concentration Gradients ◽  
Measure Concentration ◽  
Free Jet ◽  
Planar Laser Induced Fluorescence ◽  
Planar Laser

Abstract Two-color, toluene-based, planar laser-induced fluorescence (PLIF) is utilized to characterize the thermal structure of a turbulent, free jet. The PLIF technique has been used to measure concentration gradients for combustion applications, but its use to quantify thermal gradients is limited. To validate the method, compressed air is seeded with toluene particles. The seeded airflow is heated to temperatures varying from 300 to 375 K, and the heated jet exits a 1.27-cm diameter orifice into quiescent, room temperature air. The jet Reynolds number is varied from 5000 to 15,000. As the jet exits the orifice, the toluene particles fluorescence across a 266 nm laser light sheet which ultimately provides a two-dimensional temperature distribution of the free jet. The rigorous calibration procedure for the PLIF technique is described along with the seeding nuances needed to quantify the thermal structure of the jets. The PLIF technique has been demonstrated for this fundamental flow field, and it has proven to be applicable to more complex heat transfer and cooling applications. Furthermore, the time-averaged temperature distributions obtained in this investigation can be used in the validation of turbulent computational fluid dynamics (CFD) solvers.

scholarly journals Visualization of the Ludford column

2013 ◽  
Vol 721 ◽  
pp. 438-453 ◽  
Author(s):  
Oleg Andreev ◽  
Yurii Kolesnikov ◽  
André Thess
Keyword(s):  
Liquid Metals ◽  
Basic Feature ◽  
Direct Access ◽  
Experimental Procedure ◽  
Stagnant Region ◽  
Tracer Particles ◽  
Image Velocimetry ◽  
Truncated Cylinder ◽  
First Time ◽  
Flow Experiments

AbstractWhen a liquid metal flows around a truncated cylinder in the presence of a magnetic field which is parallel to the axis of the cylinder, a stagnant region develops above the cylinder. We call this region a Ludford column. The Ludford column represents the magnetohydrodynamics (MHD) analogue of the well-known Taylor columns in rotating flows. Whereas Taylor columns can be easily visualized using dye, the visualization of Ludford columns has remained elusive up to now because liquid metals are opaque. We demonstrate that this fundamental limitation of experimental MHD can be overcome by using a superconducting 5 T magnet. This facility permits us to perform MHD experiments in which the opaque liquid metals are replaced with a transparent electrolyte while maintaining the key MHD effects. We report results of a series of flow experiments in which an aqueous solution of sulphuric acid flows around a bar with square cross-section (which for simplicity shall be referred to as a cylinder). We vary the Reynolds number in the range $5\lt Re\lt 100$ and the Hartmann number in the range $0\lt Ha\lt 14$. The experimental procedure involves flow visualizations using tracer particles as well as velocity measurements using particle image velocimetry (PIV). Our experiments provide direct access to the Ludford column for the first time and reveal the spatial structure of this basic feature of MHD flows.

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