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2.23.The two-stage solidification of a sessile supercooled drop, observed by Jung et al. [64]. The upper row of photos illustrate the rapid growth of the ice dendrite. Within 18 ms, the ice dendrite covered the surface of the 5 µL drop. The lower row of photos shows the second stage solidification of the drop which took 13 seconds. . . . . 42 2.24.Experiment regime of the impact of supercooled water drop. . . . . . 47 3.1. The analytically predicted velocity and temperature profiles of water drops in free fall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.2. The analytically predicted transient temperature fields inside the drop of φ1.5 mm (left) and φ3 mm (right). . . . . . . . . . . . . . . . 56 3.3. Construction of the supercooling passage, and creation of the dry nitrogen atmosphere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.4. The body of the drop generator consisted of a cylinder container with water and a T-junction. The diameter of the nozzle was too small for liquid to flow through it by gravity alone. A pressure pulse was delivered by fash switch of the solenoid valve. The vent hole was open to the atmosphere. A gas pulse applied sufficient pressure to force out a single drop. Then the gas escaped to the atmosphere through the vent, preventing further drops from escaping. Water drops of φ230 µm was generated with a φ102 µm nozzle [29]. . . . . 59 3.5. Construction of the pneumatic drop generator with big T-conjunction. 60 3.6. Construction of the pneumatic drop generator with small T- conjunction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 3.7. Pneumatic drop generator with big T-conjunction, 7.5 cm exit tube, 500 µm pinhole, 0.1 bar pressure, 4 ms pulse width. . . . . . . . . . . . 62 3.8. Pneumatic drop generator with big T-conjunction, 7.5 cm exit tube, 800 µm pinhole, 0.1 bar pressure, 3 ms pulse width. . . . . . . . . . . . 62 3.9. Pneumatic drop generator with small T-conjunction, 10 cm exit tube, 500 µm pinhole, 0.1 bar pressure, 3 ms pulse width. . . . . . . . . . . . 62 3.10.Pneumatic drop generator with small T-conjunction, 4.5 cm exit tube, 500 µm pinhole, 0.1 bar pressure, 4 ms pulse width. . . . . . . . 62 3.11.Pneumatic drop generator with small T-conjunction, 6 cm exit tube, 800 µm pinhole, 0.1 bar pressure, 3 ms pulse width. . . . . . . . . . . . 63 List of Figures 243
3.12.Time t =0 corresponds to the start of the electrical pulse. The pressure in the cavity oscillated at a constant frequency while its amplitude gradually decreased. The gauge pressure was initially positive, but then became negative for a short time as it oscillated. Water emerged when the pressure exceeded a level, and detached while the remaining liquid started to withdraw at the negative pressure. This pressure oscillation inside the chamber can be modeled as a Helmholtz resonator with a damping frequency as f = a A , where 2π lV A is the cross-sectional area of the neck and l is the effective length (defined as l = l n + 0.8 A, with l n the neck length, V the volume of the cavity and a the speed of sound in air [29]. . . . . . . . . . . . . . 63 3.13.Pneumatic drop generator with big T-conjunction, 4.5cm exit tube, 500µm pinhole, 0.1bar pressure, 3ms pulse width . . . . . . . . . . . . 65 3.14.Pneumatic drop generator with small T-conjunction, 10 cm exit tube, 500 µm pinhole, 0.2 bar pressure, 3 ms pulse width. . . . . . . . . . . . 65 3.15.Pneumatic drop generator with big T-conjunction, 26 cm exit tube, 500 µm pinhole, 0.2 bar pressure, 3 ms pulse width. . . . . . . . . . . . 65 3.16.Pneumatic drop generator with small T-conjunction, no exit tube, 500 µm pinhole, 0.3 bar pressure, 4 ms pulse width. . . . . . . . . . . . 66 3.17.Pneumatic drop generator with big T-conjunction, no exit tube 500 µm pinhole, 0.5 bar pressure, 4 ms pulse width. . . . . . . . . . . . 66 3.18.Pneumatic drop generator with big T-conjunction, 7.5 cm exit tube, 500 µm pinhole, 0.1 bar pressure, 20 ms pulse width. . . . . . . . . . . 67 3.19.Pneumatic drop generator with small T-conjunction, 4.5 cm exit tube, 500 mm pinhole, 0.1 bar pressure, 10 ms pulse width. . . . . . . 67 3.20.Observation plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.21.The cold plate was cooled by circulating refrigerant in the internal channel. The Peltier element created a cold surface to absorb the humidity in the air, effectively eliminating the condensation on the impact surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.22.The aluminum impact surface was provided by the slider. The impact surface was renewed after each impact by pulling out the slider for around 10 mm. The insulating glasses provided the optical access. The configuration of the shadowgraph imaging is shown on the right. 71 244 List of Figures
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Drop Impact on Dry Surfaces with Ph
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Hiermit versichere ich, die vorlieg
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Fachgebiet Reaktive Strömungslehre
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to non-monotonic threshold impact v
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Splash, einseitiger Splash sowie de
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3.4.2. Calibration of the Infrared
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Nomenclature Latin capitals Unit A
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k angular wavenumber rad m −1 k R
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F G ge i K L lam m max min n opt r
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1 Introduction 1.1 Motivation Aircr
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of the WCE acquired experimentally
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passage was cooled down to −196
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SLD icing conditions have been defi
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−9 ◦ C and layers of freezing r
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adjacent downstream control volume,
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conventional methods. Papadakis et
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Figure 2.5.: Ice horn and clear ice
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This model showed good agreement un
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Xu et al. proposed the following sc
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Figure 2.9.: Splash thresholds of t
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Chen and Wang [28] observed the dro
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2.14 shows. On stainless steel, tin
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years ago [157]. Another peculiarit
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Figure 2.17.: At an ambient pressur
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The temperature needs to be found o
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The Stefan number St S completely c
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T(x, 0) = T A < T m , 0 < x < ∞ b
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Figure 2.20: Fraction of solidifica
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The mathematical description of the
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asal plane. Without all these facto
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Part I. Impact of Supercooled Water
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3 Experimental Setup This chapter i
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drop and the tube as between such t
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of nucleation ice dendrite growth,
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The boundary condition is then 1
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0.021 W m −1 K −1 at −165 ◦
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outlet of the liquid. There are two
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The maximum depth of water in the c
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Figure 3.11.: Pneumatic drop genera
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Figure 3.13.: Pneumatic drop genera
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Adjusting the Pulse Width Longer el
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(a) Shadowgraph imaging (b) The sid
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Figure 3.21.: The cold plate was co
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Figure 3.25.: The transmittance of
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eproducible. The SHS was created by
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Figure 3.30.: Planck’s law The ot
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Figure 3.32.: Heterogeneity of the
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Figure 3.35.: The valid region afte
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Divided by dΩ, Eq. 3.33 is related
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Figure 3.39.: The wavelength depend
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Figure 3.41.: Orientation dependenc
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wavelength, so that the value for r
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Temperature Gradient In light of th
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(a) 0.00 ms (b) 1.39 ms (c) 2.79 ms
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Figure 3.48.: Synchronization syste
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Figure 3.50.: Experimental setup fo
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(a) 0 ms (b) 0 ms (c) 0.6 ms (d) 0.
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Figure 4.2.: The dynamic spreading
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Figure 4.4.: Influence envelope of
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(a) 0 ms (b) 0.4 ms (c) 0.8 ms (d)
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(a) 0 ms (b) 1.39 ms (c) 2.79 ms (d
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(a) 0 ms (b) 0.05 ms (c) 0.1 ms (d)
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(a) −4 ◦ C, at 6.8 ms. (b) −1
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The contact temperature is closer t
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Obviously, the contact temperature
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Figure 4.13.: The dimensionless min
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always after the receding reached t
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Part II reports the experimental in
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to realize a high-speed rotation of
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Figure 5.2.: Impact surface with di
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Various such devices were developed
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than the values reported in literat
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Figure 5.7.: The monodisperse drop
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This performance is a reminiscence
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Figure 5.11.: The merging distance
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signal and the excitation signal of
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The analogy with a capacitor led to
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The real situation in the applicati
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Figure 5.15.: Static electric field
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Figure 5.19.: Phase shift and pulse
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disadvantage is that the number of
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Zoom Lens Working Distance Spatial
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the impact surface was not a sharp
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5.5 Synchronization Both single pul
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The last note on these two pulse tr
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Figure 5.28.: Calculation of the im
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6 Results and Discussion This chapt
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(a) 0 µs (b) 2 µs (c) 4 µs (d) 6
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high impact velocities approaching
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(a) 32 µs (b) 84 µs (c) 100 µs F
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(a) (b) (c) Figure 6.8.: Examinatio
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Our observations show that the lame
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6.3 Velocity of the Uprising Jet In
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(a) 1 µs (b) 3 µs (c) 4 µs Figur
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(a) 0 µs (b) 8 µs (c) 32 µs Figu
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(a) 45° target (b) 75° target (c)
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Nevertheless, the drop volume was e
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was surface tension. These factors
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the motion of the impinging water,
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of the single-side splash, the latt
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Page 217 and 218: (a) 0 µs (b) 10 µs (c) 11 µs (d)
Page 235 and 236: A.7 5° target (a) 0 µs (b) 24 µs
Page 255 and 256: (a) (b) (c) (d) (e) (f) Figure B.4.
Page 257 and 258: (a) 0 ms (b) 0.4 ms (c) 0.5 ms (d)
Page 259 and 260: (a) 0 ms (b) 0.35 ms (c) 1 ms (d) 1
Page 261: 2.15.Prompt splash (left) was docum
Page 265 and 266: 3.31.The extension ring (left) betw
Page 267 and 268: 4.7. Infrared imaging: total reboun
Page 269 and 270: 5.5. The custom made vibrating orif
Page 271 and 272: 5.14.Static electric field between
Page 273 and 274: 6.6. Capillary wave created by the
Page 275 and 276: A.5. Drop diameter: 189 µm, impact
Page 277 and 278: A.29.Drop diameter: 203 µm, impact
Page 280: List of Tables 2.1. MVD of Freezing
Page 283 and 284: Imaging and Computer Simulations. T
Page 285 and 286: [42] GENT, R. W., N. P. DART and J.
Page 287 and 288: [70] KOROLEV, ALEXEI V., GEORGE A.
Page 289 and 290: [99] MUNDO, CHR., M. SOMMERFELD and
Page 291 and 292: [125] RYERSON, CHARLES C., GEORGE G
Page 293 and 294: [153] ŠIKALO Š., C. TROPEA and E.
Page 296: Curriculum Vitae Personal Informati
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