scholarly journals Developing the laser doppler anemometry method for the diagnostics of kinematic parameters of a turbulent flow in the near wall region

2021 ◽  
Vol 2057 (1) ◽  
pp. 012096
Author(s):  
V G Meledin ◽  
S V Dvoinishnikov ◽  
I K Kabardin ◽  
A S Chubov ◽  
G V Bakakin ◽  
...  
Keyword(s):  
Velocity Vector ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Wall Region ◽  
Kinematic Parameters ◽  
Local Flow ◽  
Positioning Device ◽  
Measurement Area ◽  
Measuring Unit ◽  
Near Wall

Abstract The aim of the work is to develop a laser Doppler anemometry method for diagnosing turbulent aerodynamic flows in the near wall region. This will enable measuring two projections of the velocity vector in the range of 0.001 … 400 m/s with a relative error not exceeding 0.1%. The measurement area is 0.1×0.1x0.5mm. The positioning device allows moving the measuring unit in the area of 250×250x250 mm with an accuracy of 0.1 mm. This method also provides the ability to measure local flow rate fluctuations.

scholarly journals Development of the method of laser Doppler anemometry for diagnostics of turbulent flows at high speed

2021 ◽  
Vol 2119 (1) ◽  
pp. 012110
Author(s):  
M R Gordienko ◽  
I K Kabardin ◽  
V G Meledin ◽  
A K Kabardin ◽  
M Kn Pravdina ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Flow Rate ◽  
High Speed ◽  
Velocity Vector ◽  
Laser Doppler Anemometry ◽  
Laser Doppler ◽  
Local Flow ◽  
Positioning Device ◽  
Measurement Area ◽  
Measuring Unit

Abstract The aim of the work was to develop a laser Doppler anemometry method for high-speed turbulent aerodynamic flow diagnostic. As a result, this allowed us to measure two projections of the velocity vector in the range of 0.1 - 400 m/s with a relative error not exceeding 0.5%. The measurement area was 0.1x0.1x0.5mm. The positioning device moved the measuring unit in the area of 250 x 250 x 250 mm with an accuracy of 0.1 mm. This method also provides the ability to measure local flow rate fluctuations.

scholarly journals Turbulent boundary layers over permeable walls: scaling and near-wall structure

2011 ◽  
Vol 687 ◽  
pp. 141-170 ◽  
Author(s):  
C. Manes ◽  
D. Poggi ◽  
L. Ridolfi
Keyword(s):  
Turbulent Flows ◽  
Laser Doppler Anemometry ◽  
Wall Turbulence ◽  
Shear Instability ◽  
Wall Structure ◽  
Wall Region ◽  
Mean Velocity ◽  
Wide Range ◽  
Permeable Walls ◽  
Near Wall

AbstractThis paper presents an experimental study devoted to investigating the effects of permeability on wall turbulence. Velocity measurements were performed by means of laser Doppler anemometry in open channel flows over walls characterized by a wide range of permeability. Previous studies proposed that the von Kármán coefficient associated with mean velocity profiles over permeable walls is significantly lower than the standard values reported for flows over smooth and rough walls. Furthermore, it was observed that turbulent flows over permeable walls do not fully respect the widely accepted paradigm of outer-layer similarity. Our data suggest that both anomalies can be explained as an effect of poor inner–outer scale separation if the depth of shear penetration within the permeable wall is considered as the representative length scale of the inner layer. We observed that with increasing permeability, the near-wall structure progressively evolves towards a more organized state until it reaches the condition of a perturbed mixing layer where the shear instability of the inflectional mean velocity profile dictates the scale of the dominant eddies. In our experiments such shear instability eddies were detected only over the wall with the highest permeability. In contrast attached eddies were present over all the other wall conditions. On the basis of these findings, we argue that the near-wall structure of turbulent flows over permeable walls is regulated by a competing mechanism between attached and shear instability eddies. We also argue that the ratio between the shear penetration depth and the boundary layer thickness quantifies the ratio between such eddy scales and, therefore, can be used as a diagnostic parameter to assess which eddy structure dominates the near-wall region for different wall permeability and flow conditions.

Acoustic power flow measurement in a thermoacoustic resonator by means of laser Doppler anemometry (L.D.A.) and microphonic measurement

2000 ◽  
Vol 60 (1) ◽  
pp. 1-11 ◽  
Author(s):  
H. Bailliet ◽  
P. Lotton ◽  
M. Bruneau ◽  
V. Gusev ◽  
J.C. Valière ◽  
...  
Keyword(s):  
Flow Measurement ◽  
Power Flow ◽  
Laser Doppler Anemometry ◽  
Acoustic Power ◽  
Laser Doppler

Direct numerical simulations of Rayleigh–Bénard convection in water with non-Oberbeck–Boussinesq effects

2019 ◽  
Vol 881 ◽  
pp. 1073-1096 ◽  
Author(s):  
Andreas D. Demou ◽  
Dimokratis G. E. Grigoriadis
Keyword(s):  
Numerical Simulations ◽  
Two Dimensions ◽  
Direct Numerical Simulations ◽  
Wall Region ◽  
Number Range ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Near Wall

Rayleigh–Bénard convection in water is studied by means of direct numerical simulations, taking into account the variation of properties. The simulations considered a three-dimensional (3-D) cavity with a square cross-section and its two-dimensional (2-D) equivalent, covering a Rayleigh number range of $10^{6}\leqslant Ra\leqslant 10^{9}$ and using temperature differences up to 60 K. The main objectives of this study are (i) to investigate and report differences obtained by 2-D and 3-D simulations and (ii) to provide a first appreciation of the non-Oberbeck–Boussinesq (NOB) effects on the near-wall time-averaged and root-mean-squared (r.m.s.) temperature fields. The Nusselt number and the thermal boundary layer thickness exhibit the most pronounced differences when calculated in two dimensions and three dimensions, even though the $Ra$ scaling exponents are similar. These differences are closely related to the modification of the large-scale circulation pattern and become less pronounced when the NOB values are normalised with the respective Oberbeck–Boussinesq (OB) values. It is also demonstrated that NOB effects modify the near-wall temperature statistics, promoting the breaking of the top–bottom symmetry which characterises the OB approximation. The most prominent NOB effect in the near-wall region is the modification of the maximum r.m.s. values of temperature, which are found to increase at the top and decrease at the bottom of the cavity.

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