Calculation of Calibration Curves for the Phase Doppler Technique: Comparison between Mie Theory and Geometrical Optics

Al-Chalabi, S.; Hardalupas, Y.; Jones, Alan R.; Taylor, A. M. K. P.

doi:10.1007/978-1-4757-1983-3_10

Cited by 16 publications

(8 citation statements)

References 7 publications

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“…aperture 1 2 Figure 4a shows the response curve of the instrument with the centre of the collection lens at (%, flo) of (150 ~ 0 ~ when the phase shift is calculated at the centre of the two apertures. The high frequency oscillations of the response curve were observed also by A1-Chalabi et al (1988) and Sankar and Bachalo (1991) and were caused by the interference of surface reflection with FIR. The complexity of the scattered fringe patterns, which, for example, for a water droplet of 47 lam diameter is identified by the contours of scattered light intensity of Fig.…”

Section: L Integration O/'light Intensity Over the Collection Apertmentioning

confidence: 96%

“…Although it is known that the high frequency oscillations of the response curve are reduced by the integration of the scattered light intensity over the collection apertures (Saffman, 1986;A1-Chalabi et al, 1988), it is not clear why the low frequency oscillations are reduced and this observation will be examined in the next paragraphs. The intensity distributions of the scattered light corresponding to the interference between either the first or the second part of FIR from both beams is shown in Fig.…”

Section: L Integration O/'light Intensity Over the Collection Apertmentioning

confidence: 99%

“…Theoretical analysis of the response curves of the phase-Doppler instrument in the off-axis forward-scatter region (Hardalupas, 1989;Saffman et al, 1984;Sankar and Bachalo, 1991) has shown that the intensity of the light scattered by transparent spherical particles can be considered as the result of the interference of reflected and refracted rays from the particle from each beam. A linear relationship between the measured phase shift and particle diameter is obtained provided that the intensity of one of the contributions to the scattered light dominates the others, and that the finite size of the collection apertures is sufficiently large to remove the high frequency oscillations (A1-Chalabi et al, 1988;Hardalupas and Taylor, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…However, the application of the technique at angles between the main rainbow and direct backscatter is not straight forward, since the light scattered is due mainly to the first internal reflection through the particle (van de Hulst, 1957) rather than refraction as in the forward scatter region. A1-Chalabi et al (1988) questioned the application of the technique in the backscatter region, because at least two parts of first internal reflection interfere with each other as well as with the surface reflection and cause low and high frequency departures from linearity of the response curve. Sankar and Bachalo (1991) calculated the response curve after integration of the intensity of the scattered light over the collection apertures and showed that it becomes linear over a limited size range, which was also observed by the Mie scattering calculations of Bauckhage et al (1988).…”

Section: Introductionmentioning

confidence: 99%

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Backscatter phase-Doppler anemometry for transparent non-absorbing spheres

Hardalupas

Liu

1993

Experiments in Fluids

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The application of phase-Doppler anemometer for scattering angles between the main rainbow and direct backscatter, was examined by calculating the spatial intensity distribution and the phase of the light scattered by a particle crossing the measuring volume. Geometrical optics was assumed and contributions to the scattered light due to reflection on the external surface of the particle and first internal reflection were considered. The response curve of the technique was calculated for different particle refractive indices, beam intersection angles, collection angles and spacings between the collection apertures. Linear response curves were obtained after integration of the intensity of the scattered light over sufficiently large rectangular collection apertures, but they became non-monotonic after a critical value of phase shift, which varied with the optical arrangement between around 220 ~ and 360 ~ did not scale with common scaling parameters used for forward scatter light, and limited the possible size range of the instrument for one optical arrangement. The particle refractive index determined the collection angle and limited sizing to particles with little uncertainty in refractive index, since a 5 % change in refractive index led to uncertainties in size of the order of 100%. An alternative sizing technique is suggested for the backscatter region.

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Section: L Integration O/'light Intensity Over the Collection Apertmentioning

confidence: 96%

Section: L Integration O/'light Intensity Over the Collection Apertmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Backscatter phase-Doppler anemometry for transparent non-absorbing spheres

Hardalupas

Liu

1993

Experiments in Fluids

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“…Nonlinearities (typically oscillations) have also been predicted for small droplets and certain light scattering angles by Mie scattering calculations (Saffman et al, 1984;Al-Chalabi et al, 1988;and Sankar and Bachalo, 19911, although the calculations show that increasing the integration of the scattered light at the receiver by reducing the focal length of the receiving lens damped out these oscillations. In contrast, Houser and Bachalo (1985) report linear PDPA response for nebulized, monodisperse polystyrene latex spheres (PSL) in the 0.54-2.88-pm range.…”

Section: Introductionmentioning

confidence: 93%

Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

Ceman

Rader

O’Hern

1993

Aerosol Science and Technology

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The experimental response of the phase Doppler particle analyzer (Aerometrics, Inc., Sunnyvale, CAI to monodisperse oleic acid droplets in the 2.3-24-pm range is presented for three optical configurations. Significant nonlinearities for droplets with diameters < 20 p m were seen when using the standard configuration of a 495-mm focal length receiving lens at an off-forward scattering angle of 0 = 30". Of particular concern are response oscillations < 7 p m that lead to multivalued regions. In order to reduce these nonlinearities, two improvements to the standard receiver configuration were studied as suggested by theoretical studies reported in the literature. First, the receiver focal length was shortened to 240 mm (at 0 = 30") to increase the integration of scattered light. --As expected, the instrument response did significantly improve over the standard case, both in terms of linearity and scatter, for droplets > 5 pm. A significant departure from linearity (undersizing by 1.7 p m for a 2.3-pm indicated droplet diameter) was observed below this size, although the multivalued region of response was greatly reduced. Second, the receiving lens (focal length of 240 mm) was configured at a collection angle of 70°, close to the Brewster angle for oleic acid droplets where interference from reflected light should be minimized. Surprisingly, the performance of this configuration was comparable to the standard case (even though a shorter focal length was used), and inferior to the 240-mm/3O0 configuration.

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