Gaussian and Exponential Approximations of the Modulation Transfer Function

Rao, U. V. Gopala; Jain, V. K.

doi:10.1364/josa.57.001159

Cited by 8 publications

(2 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Astigmatic aberrations are minimized by compensator blocks. Hence, the PSF at each depth position should have almost a circular shape with its half-width being equal to half-width of the line spread function (LSF) (Rao and Jain 1967). In order to assess the LSF, intensity profiles across sharp edges (cf.…”

Section: Depth Of Field and Smallest Visible Drop Sizementioning

confidence: 99%

“…The line spread function is obtained by numerical differentiation of the edge spread function (Claxton and Staunton 2008). The halfwidth of the line spread function is equal to the width of the PSF in x-direction and is obtained by matching the derived intensity profile with a Gaussian fit (Rao and Jain 1967).…”

Section: Depth Of Field and Smallest Visible Drop Sizementioning

confidence: 99%

See 1 more Smart Citation

Three-dimensional imaging of swirled spray injection in a generic aero engine burner under realistic operating conditions

Klinner

Willert

2021

Exp Fluids

View full text Add to dashboard Cite

Tomographic shadowgraph imaging is applied to reconstruct the instantaneous three-dimensional spray field immediately downstream of a generic aero engine fuel injector. Within the swirl passage of the injector model, a single kerosene jet undergoes air-blast atomization in a cross-flow configuration at Weber numbers of $$\text {We}=360-770$$ We = 360 - 770 , air pressures of $$p_a=4-7\,\text{ bar }$$ p a = 4 - 7 bar and air temperatures of $$T_a=440-570\,\text{ K }$$ T a = 440 - 570 K . High-speed, high magnification shadowgraphy is used to visualize the initial fuel atomization stages within the fuel injector before the spray enters the spray chamber. The 4-camera tomographic measurement setup is described in detail and includes a depth-of-field analysis with respect to droplet size based on Mie simulations and calibration data of the point-spread function. For a volume size of $$16\times 13\times 10\,\text{ mm}^3$$ 16 × 13 × 10 mm 3 , the smallest resolvable droplet diameter is estimated to be $$d=10\,\mu \text{ m }$$ d = 10 μ m within the focal plane and increases to $$d \approx 20\,\mu \text{ m }$$ d ≈ 20 μ m toward the edges of the volume. Droplet velocities above the resolution limit were retrieved by 3-d cross-correlation of two volumetric reconstructions recorded at two consecutive time-steps. This is accompanied by an error analysis on the random error dependency on the camera viewing geometry. The results indicate increasing motion and fluctuations of the spray tail with increasing temperature and Weber number. Validation against PDA data further downstream of the burner plate revealed consistency for size classes $$d=10\,\mu \text{ m }$$ d = 10 μ m and $$d=15\,\mu \text{ m }$$ d = 15 μ m . Deviations from PDA occur in regions with strong velocity gradients due to different spatial resolutions, the presence of reconstruction ambiguities (ghost particles), uncertainties inherent to the two-frame cross-correlation of spray volumes and the finite LED pulse duration. Graphical Abstract

show abstract

Section: Depth Of Field and Smallest Visible Drop Sizementioning

confidence: 99%

Section: Depth Of Field and Smallest Visible Drop Sizementioning

confidence: 99%