Spreading of droplets impacting different wettable surfaces at a Weber number close to zero

Liu, Xin; Zhang, Xuan; Min, Jingchun

doi:10.1016/j.ces.2019.06.058

Cited by 74 publications

(25 citation statements)

References 45 publications

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“…2 shown, after the droplet impacts, the droplet first spreads to a circular film under inertial force and reaches the maximum spreading (side-view image at 5.4 ms or top-view image at 4.0 ms), which is similar to the spreading on a regular homogeneous surface. [41][42][43][44] At the maximum spreading, the circular film covers both the hydrophilic part and the superhydrophobic part of the experimental surface with an adhesion length (e) of 1 mm. Then, the film begins to retract.…”

Section: Impacting Droplet Morphology and Directional Transportation Mechanismmentioning

confidence: 99%

Directional Transportation of Impacting Droplets on Wettability-Controlled Surfaces

et al. 2020

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Although a superhydrophobic surface could realize rapid rebounding (i.e., short contact time) of an orthogonal impacting droplet, the rebounding along the original impacting route may limit its engineering application; in contrast, the directional transportation seems to be more promising. Here, we achieve directional transportation of a droplet impacting on a wettability-controlled surface. When the droplet eccentrically impacts on the boundary between the superhydrophobic part and the hydrophilic part, it undergoes spreading, retracting, departure, throwing and breaking up stages, and finally bounces off directionally. The directional transportation distance could even reach more than ten times of the droplet size, considered the adhesion length (i.e., covering length on the hydrophilic part by the droplet at the maximum spreading) is optimized. However, there is a critical adhesion length, above which the directional transportation does not occur. To be more generalized, the adhesion length is de-dimensionalized by the maximum spreading radius, and the results show that as the dimensionless adhesion length increases, the transportation distance first increases and then decreases to zero. Under the present impacting conditions, the optimal dimensionless adhesion length corresponding to the maximum transportation distance is near 0.4, and the critical dimensionless adhesion length is about 0.7. These results provide fundamental understanding of droplet directional transportation, and could be useful for related engineering applications.

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Section: Impacting Droplet Morphology and Directional Transportation Mechanismmentioning

confidence: 99%

Directional Transportation of Impacting Droplets on Wettability-Controlled Surfaces

et al. 2020

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“…(36). In addition to the experimental measurements, a series of models for predicting * have been developed based on different approaches [14,[41][42][43][44][45][48][49][50][51][52][53]. Several widely used or recently established models [43,48,53] were selected for predicting the * in Case 1-6, and the predicted results were compared with the results from the experimental measurements and CFD simulations, as shown in Fig.…”

Section: Results Comparisonmentioning

confidence: 99%

“…The accuracy of this method depends on the calculation of each energy component during droplet impact, especially the prediction of the energy dissipation. It is worth mentioning that both of the two methods require the maximum spread factor of the droplet, and different correlations have been established for predicting the maximum spread factor based on different approaches, including momentum conservation [50], scaling analysis [51,52] and energetic analysis [14, 41-45, 48, 49, 53].…”

Section: Introductionmentioning

confidence: 99%

Analysis and prediction of the gas-liquid interfacial area for droplets impact on solid surfaces

Xie

Ding

Ingham

et al. 2020

Applied Thermal Engineering

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Highlights The interfacial areas of droplets during impact on solid surfaces are analysed.  A new correlation for predicting the maximum gas-liquid interfacial area is proposed. The dynamic contact angle with local grid refinement is implemented in the CFD model. The impact of droplets on both hydrophobic and hydrophilic surfaces are studied. The inner flow field of droplets during impact onto a solid surface is described.

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“…In addition, the side-view images captured enabled visualization of the dynamic contact angle θ d of the expanding droplet . Knowledge of θ d is considered important for investigating the spreading dynamics of a droplet on a hydrophilic substrate. − Post processing images in ImageJ software, θ d values for the DIW droplet impinging on PMMA, treated glass, and Teflon were found to be 115 ± 3, 120 ± 3, and 133 ± 3°, respectively.…”

Section: Materials and Methodologymentioning

confidence: 99%

Droplet Impact and Spreading on Inclined Surfaces

2021

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Introducing surface inclination in the case of droplet impact on solid substrates results in complicated dynamics post impact. The present work investigates the dynamics involved in the spreading phase of the droplet on inclined substrates. Experiments are conducted with water droplets impinging on inclined dry solid substrates with varying wettability values. The results reveal the presence of three phases in the droplet spread behavior. In the first phase, the droplet is observed to depict a close radial symmetry and is dominated by inertia forces. Phase 1 ends when the upstream droplet lamella post impact gets pinned to the surface or starts retracting as a consequence of surface forces becoming dominant. A scaling analysis developed to predict the pinning time of the droplet shows that the pinning time is independent of impact velocity, which is also observed during experiments. The asymmetries in the radial evolution of the droplet appear in phase 2 and become dominant in phase 3. Phase 2 terminates when the droplet attains the maximum lateral spread, which is established as a function of the normal component of the Weber number. Phase 3 is initiated when the droplet starts retracting in the lateral direction while the longitudinal expansion continues. Using an energy-based model constructed to predict the maximum spread, we show that the impact inertia of the droplet controls the longitudinal droplet spread in phases 1 and 2, while the gravity forces are primarily responsible for the droplet spread in phase 3. The model results were validated with the experiments conducted in-house and were found to be in good agreement.

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Spreading of droplets impacting different wettable surfaces at a Weber number close to zero

Cited by 74 publications

References 45 publications

Directional Transportation of Impacting Droplets on Wettability-Controlled Surfaces

Directional Transportation of Impacting Droplets on Wettability-Controlled Surfaces

Analysis and prediction of the gas-liquid interfacial area for droplets impact on solid surfaces

Droplet Impact and Spreading on Inclined Surfaces

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