Analysis of signal-to-noise ratio of the laser Doppler velocimeter

Lading, Lars

doi:10.1007/bf01414737

Cited by 11 publications

(6 citation statements)

References 4 publications

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“…Then, substituting Equations (14) and (17) into Equation (19), the relationship can be obtained between laser scanning rate and scanning spacing (the row spacing) as follows…”

Section: Selection Criterion Of Laser Scanning Ratementioning

confidence: 99%

Modal shape measurement of fiber-reinforced composite plate with high efficiency and precision based on laser linear scanning method

Yongle

et al. 2018

Measurement and Control

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The laser linear scanning method is proposed to measure the modal shape of fiber-reinforced composite thin plate with high efficiency and precision. First, by establishing the laser scanning frame model of the composite plate, the corresponding extraction principle of modal shape data and laser scanning rate selection criterion are explained in detail to clarify the theoretical principle of laser linear scanning method. The corresponding test procedure of modal shape, drawing method from the shape scanning data, and control method of the constant laser scanning rate are also proposed based on the developed laser linear scanning system. Then, a TC300 carbon fiber/resin composite thin plate is taken as a research object to verify the effectiveness and reliability of such a method, through comparing the results obtained by the traditional experimental modal method and finite element method. Moreover, the influences of constraint boundary condition, excitation level, laser scanning rate, scanning spacing, scanning path mode, the fiber angles, and fiber material damage on modal shape results are also discussed. It has been found that laser linear scanning method can improve test efficiency of modal shape of the composite plate with high preciseness. Except for scanning path mode, the other parameters have a major impact on each shape morphology, and their effects can be quantitatively analyzed by identifying the positions and clarity of nodal lines of each modal shape. Especially, the high-density modal shape results and their equal amplitude lines in different projection views can be used to determine whether or not the composite plate is damaged as well as its damaged degrees.

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“…Then, substituting Equations (14) and (17) into Equation (19), the relationship can be obtained between laser scanning rate and scanning spacing (the row spacing) as follows…”

Section: Selection Criterion Of Laser Scanning Ratementioning

confidence: 99%

Modal shape measurement of fiber-reinforced composite plate with high efficiency and precision based on laser linear scanning method

Yongle

et al. 2018

Measurement and Control

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“…Measuring points are spaced 0.125 diameters apart to obtain a detailed picture of the recirculation bubble downstream of the cylinder. A beam power of 3 W is maintained to eliminate noise from small particles [48,49], and velocities from particles yielding a signal-to-noise ratio less than +1 dB are omitted to avoid bias in the velocity calculation [50].…”

Section: Measurements Takenmentioning

confidence: 99%

Verification testing in computational fluid dynamics: an example using Reynolds‐averaged Navier–Stokes methods for two‐dimensional flow in the near wake of a circular cylinder

Richmond-Bryant¹

2003

Numerical Methods in Fluids

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SUMMARYVeriÿcation testing was performed for various Reynolds-averaged Navier-Stokes methods for uniform ow past a circular cylinder at Re = 5232. The standard and renormalized group (RNG) versions of the k-method were examined, along with the Boussinesq, Speziale and Launder constitutive relationships. Wind tunnel experiments for ow past a circular cylinder were also performed to obtain a comparative data set. Preliminary studies demonstrate poor convergence for the Speziale relationship.Veriÿcation testing with the standard and RNG k-models suggests that the simulations exhibit global monotonic convergence for the Boussinesq models. However, the global order of accuracy of the methods was much lower than the expected order of accuracy of 2. For this reason, pointwise convergence ratios and orders of accuracy were computed to show that not all sampling locations had converged (standard k-model: 19% failed to converge; RNG k-model: 14% failed to converge). When the non-convergent points were removed from consideration, the average orders of accuracy are closer to the expected value (standard k-model: 1.41; RNG k-model: 1.27). Poor iterative and global grid convergence was found for the RNG k-=Launder model. The standard and RNG k-models with the Boussinesq relationship were compared with experimental data and yielded results signiÿcantly di erent from the experiments.

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“…These expressions can then be used to calculate the signal-to-noise ratio for the various configurations [7]. (4) Other configurations.…”

Section: Kr O V B= Fmentioning

confidence: 99%

“…the average power of the photocurrent and the power spectrum for the various cases. We will not do the detailed calculations here, but only give the results referring to [7]:…”

mentioning

confidence: 99%

A fourier optical model for the laser Doppler velocimeter

Lading¹

1972

Opto-electronics

Self Cite

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The treatment is based on a fourier optical model. It is shown how the various configurations (i.e. "differential mode" and reference beam mode with both one and two incident beams) are incorporated in the model, and how it can be extended to three dimensions.The particles are represented by a sum of weighted delta functions of random position with respect to their influence on the scalar field.The influence of the receiver configuration is investigated : it is shown that the aperture size is roughly inversely proportional to the effective area in the measuring plane from which beams are heterodyned on the detector.The purpose of the pinhole, namely to filter the measuring volume out from the rest of space, is shown to depend on the aperture size. The diameter of the pinhole should never be smaller than the real image-found by geometrical optics -of the measuring volume (naturally), but its filtering ability vanishes as the aperture size converges towards zero.The results based on fourier optics are compared with the rough estimates obtainable by using the "antenna formula" for heterodyning (A RQ ,~ A2).

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Analysis of signal-to-noise ratio of the laser Doppler velocimeter

Cited by 11 publications

References 4 publications

Modal shape measurement of fiber-reinforced composite plate with high efficiency and precision based on laser linear scanning method

Modal shape measurement of fiber-reinforced composite plate with high efficiency and precision based on laser linear scanning method

Verification testing in computational fluid dynamics: an example using Reynolds‐averaged Navier–Stokes methods for two‐dimensional flow in the near wake of a circular cylinder

A fourier optical model for the laser Doppler velocimeter

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