CN101776561B - Fluid boundary control-based quantitative measurement method for fluid slippage on super-hydrophobic surface - Google Patents
Fluid boundary control-based quantitative measurement method for fluid slippage on super-hydrophobic surface Download PDFInfo
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- CN101776561B CN101776561B CN200910264029XA CN200910264029A CN101776561B CN 101776561 B CN101776561 B CN 101776561B CN 200910264029X A CN200910264029X A CN 200910264029XA CN 200910264029 A CN200910264029 A CN 200910264029A CN 101776561 B CN101776561 B CN 101776561B
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Abstract
The invention discloses a fluid boundary control-based quantitative measurement method for fluid slippage on a super-hydrophobic surface, which is characterized by comprising the following steps: preparing the super-hydrophobic surface, treating the prepared super-hydrophobic surface, clamping the treated super-hydrophobic surface on a rheological test platform, and calibrating the position of a clamp and mapping the clamp; and performing rheological test operation on the super-hydrophobic surface and performing rheological test operation on the fluid on a smooth hydrophobic surface under the same test condition to acquire torques applied to the clamp when the fluids are at the same shear speed under the two conditions, and calculating the slippage length according to the measured torques. The method has a wider test range, and not only can measure the length of the fluid slippage on the super-hydrophobic surface on which the super-hydrophobic area is circular and the outside of the super-hydrophobic area is the smooth hydrophobic surface, but also can measure the length of the fluid slippage on the prepared common super-hydrophobic surface.
Description
Technical field
The present invention relates to super hydrophobic surface fluid slippage drag reduction technology field, refer in particular to a kind of super hydrophobic surface fluid slippage measuring technique based on fluid boundary control, it is applicable to the measuring sliding length and the research of the fluid that can be in super-hydrophobic state on the super hydrophobic surface.
Background technology
Because its special super-hydrophobic effect, super hydrophobic surface is paid close attention in research in recent years widely, and the report of existing a large amount of super hydrophobic surface technologies of preparing is as the river thunder seminar of the Chinese Academy of Sciences report to super hydrophobic surface.On this basis, super hydrophobic surface progressively is applied in the engineering to prevent that liquid from adhering to, keeping cleaning surfaces.Existing research shows that all the peculiar super-hydrophobic effect of super hydrophobic surface is to realize that by the compound contact interface between liquid and surface this compound interface is made of jointly liquid-solid boundary and liquid gas interface.According to slippage drag reduction theory, this compound contact interface helps the generation of fluid slippage, can be used for engineering fluid drag reduction field, and therefore, super hydrophobic surface has huge application potential in fluid drag-reduction research and engineering application.
Sliding phenomenon is generally portrayed by slip length, and according to the definition of Navier to slip length, for smooth hydrophobic surface, the fluid slip length is that fluid velocity is that zero point is to the distance between the surface, as shown in Figure 1.Fluid 1 has sliding velocity v on smooth hydrophobic surface 2
s, then slip length b is:
b＝v
s/(dv/dz) (1)
Wherein v is the speed of fluid, can be expressed as the function v (z) about z.For super hydrophobic surface, according to the definition of convection cell slip lengths such as Lauga, the fluid slip length be the point that disappears of fluid average velocity to the distance between the surface, then according to definition, fluid slip length computing formula is on the super hydrophobic surface:
b＝v
s/(dv/dz)＝v
sη/τ (2)
V wherein
sBe the average slip speed of fluid on super hydrophobic surface, dv/dz is the average shear rate that fluid bore on the super hydrophobic surface, and η is the viscosity of fluid, and τ is the average shear stress that fluid bears.Up to the present, people such as Philip, Lauga and Charlaix seminar in succession to the super hydrophobic surface fluid slippage carried out theory and modeling effort.Yet because the shortcoming of its measuring technology, the experimental study work of at present super hydrophobic surface fluid slippage drag reduction aspect being carried out is very few.At first to super hydrophobic surface fluid slippage development experimental study be people such as Ou Jia, they adopt and make up tube method the slippage situation of super-hydrophobic pipeline inner fluid is studied.Because performance difficulty, their method is used seldom in the field of study.2006, employing flow graphs such as Choi to the super hydrophobic surface fluid slippage study.The cone-plate anchor clamps that they adopt the flow graph system first to the super hydrophobic surface fluid slippage study, set up test model.Yet, because the filling in the gap of liquid between super hydrophobic surface and hydrophobic surface (test fixture) has the uneven characteristics of xsect, these characteristics as shown in Figure 2, the side appearance profile of the fluid 1 between anchor clamps 3 and the super hydrophobic surface 5 is not the required standard drum type profile of test, brought bigger slip length deviation (to call the slip length test deviation that the super hydrophobic surface wettability causes in the following text) when therefore, the method for employing Choi is tested.Bocquet seminar has also proposed the query of this respect to the method for Choi, they think that the slip length test deviation difference that the super hydrophobic surface wettability causes is big more than the slip length true value, test result can not illustrate the fluid drag-reduction performance of super hydrophobic surface, but they do not provide and improve one's methods.Li Jian etc. are a kind of by the fluid slip length on the control boundary method test super hydrophobic surface in Chinese Science Bulletin the 24th interim proposition in 2009, but their tested object is only limited to special processing super hydrophobic surface (guarantees that in process super-hydrophobic region area is less than the anchor clamps area, and other zones are smooth hydrophobic surface), then be difficult to test for the fluid slippage on the super hydrophobic surface that has prepared with non-regular borders.
Summary of the invention
The objective of the invention is the method for propositions such as Li Jian is improved, it is expanded in the measuring sliding length of the fluid that can be in super-hydrophobic state on the general super hydrophobic surface.
The technical scheme of invention is as follows:
A kind of super hydrophobic surface fluid slip length measuring technology based on boundary Control is characterized in that this method carries out as follows:
1) at first prepares super hydrophobic surface, the super hydrophobic surface of preparation is handled, the super hydrophobic surface after handling is clamped on the rheometer test platform, carry out chucking position demarcation and anchor clamps mapping by the guidance of rheometer test handbook.
2) fluid of interpolation rheometer test volume that handbook is advised on super hydrophobic surface, carry out the rheometer test operation, and under same condition, the fluid on the smooth hydrophobic surface is carried out the rheometer test operation, obtain the moment of torsion that is applied to when fluid under two kinds of situations is in identical shear rate on the anchor clamps, and calculate slip length according to measuring torquer.
In the said method, anchor clamps can be defined as standard fixture, and promptly diameter is cone-plate anchor clamps or the plate jig of Φ 20mm, Φ 40mm or Φ 60mm, also can be the special anchor clamps of customization, and diameter is determined on demand.The process of super hydrophobic surface being handled according to the anchor clamps diameter is as follows: the processing diameter circular masks littler than anchor clamps diameter, reprocess the mask of another aperture and anchor clamps equal diameters, with two masks of preparation with one heart attached to (super hydrophobic surface adopts the additive method preparation on the super hydrophobic surface, irrelevant with the concrete implementation detail of this patent, will not describe in detail), super hydrophobic surface to masked covering carries out hydrophilic treatment afterwards, make the super hydrophobic surface of the gap between two masks have hydrophilic coating, present hydrophilicity.
In the said method, need guarantee during the clamping super hydrophobic surface between anchor clamps and the lip-deep hydrophilic circle ring area to neutrality, realization to the process of neutrality is: the surface is positioned on the test platform → manual mobile anchor clamps make anchor clamps near the surface, the distance of surface and anchor clamps is less than the distance relation on 500 μ m → observation lip-deep hydrophilic coating zone boundary and anchor clamps border, the fine setting surface location makes the hydrophilic coating zone boundary equate with the gap at four direction on anchor clamps border.
In the said method, fluid slip length definition is (2) formula on the super hydrophobic surface, and the fluid slip length computing formula when adopting plate jig to measure is:
b＝(1-M
SH/M
H)D/((d
1/d
2)
4-(1-M
SH/M
H)) (3)
The computing formula of fluid slip length b when adopting the cone-plate anchor clamps to measure is:
M wherein
SHAnd M
HBe respectively the moment of torsion that obtains when super hydrophobic surface and smooth hydrophobic surface tested, d
1Be the diameter in the super-hydrophobic zone that hydrophilic region surrounded, d
2Be the overall diameter of hydrophilic region, equal the anchor clamps diameter, α is cone-plate anchor clamps bus and the angle of testing the plane.Following formula is that the fluid apparent viscosity that will measure on smooth hydrophobic surface is as fluid viscosity η, and the average shear stress that measures on the super hydrophobic surface (2) formula that is updated to derived out, and hypothesis fluid slip length and sliding velocity wherein satisfies Navier sliding relationship (1).
The present invention has following technical advantage:
Significantly improve measuring accuracy, the same with method in the Li Jian literary composition, the slip length test deviation that the super hydrophobic surface wettability causes among the present invention has guaranteed the measuring accuracy of system.
Guarantee the stability of the ultra-hydrophobicity of super hydrophobic surface in the test process, the pressure that fluid bears among the present invention is lower, and fluid super-hydrophobic state exchange from the teeth outwards can not take place.
Test specification is more extensive, the method of testing of Li Jian is extended in the measurement of the fluid slip length on the general super hydrophobic surface that has prepared, and is to be the fluid slippage on the super hydrophobic surface of smooth hydrophobic surface outside circle, the super-hydrophobic zone not only at super-hydrophobic zone on the surface.
Description of drawings
The definition of Fig. 1 surfactant fluid slip length
Fig. 2 is based on the special synoptic diagram of sprawling of fluid in the super hydrophobic surface fluid slip length test of flow graph platform
Fig. 3 super hydrophobic surface processing procedure synoptic diagram
Fig. 4 adopts the super hydrophobic surface fluid slippage test philosophy figure based on boundary Control of plate jig
Fig. 5 adopts the super hydrophobic surface fluid slippage test philosophy figure based on boundary Control of cone-plate anchor clamps
1 test fluid flow, 2 smooth hydrophobic surface, 3 plate jigs, 4 cone-plate anchor clamps, 5 super hydrophobic surfaces, 6Cassie contact area, 7Wenzel contact area, 8 masks, 9 hydrophilic coatings.
Embodiment
Below in conjunction with concrete implementation of processes details and the working condition that Fig. 3～5 explanation the present invention propose.
Embodiment one (adopting plate jig to measure) as Fig. 3, Fig. 4
The process synoptic diagram of Fig. 3 for the super hydrophobic surface that has prepared is handled.At first process two masks 8, the diameter d of circular masks
1Than anchor clamps d
2Diameter is little, and effect is better during little 1～3mm, the aperture d of circular hole mask
2With the anchor clamps diameter d
2Equate that outer shape does not have specific (special) requirements, shown in Fig. 3 (a).The mask 8 for preparing is covered on the super hydrophobic surface 5, shown in Fig. 3 (b).The super hydrophobic surface 5 that is coated with mask 8 is carried out hydrophilic treatment, generally adopt metal spraying or spray hydrophilic metal material and handle, also can adopt other hydrophilic coating disposal route, carry out having on super hydrophobic surface 5 after hydrophilic coating is handled and the mask surface 8 coating 9 as thin as a wafer, shown in Fig. 3 (c).After removing mask, on the super hydrophobic surface 5 on the mask 8 unlapped circle ring areas, has residual hydrophilic coating 9, shown in Fig. 3 (d).The distribution of hydrophilic coating 9 on super hydrophobic surface 5 is shown in Fig. 3 (e), and hydrophilic coating 9 is a toroidal, at this moment, if fluid spreads into the inner radius of annulus, sprawls continuing, till reaching annulus external diameter border.
Fig. 4 is for adopting the test philosophy of plate jig.Fig. 4 (a) is the position relation between plate jig 3, fluid 1 and the super hydrophobic surface 5 when the fluid on the super hydrophobic surface 51 is tested, in the zone that hydrophilic coating covers, fluid 1 forms Wenzel contact area 7 (generally speaking with super hydrophobic surface 5, slip length when fluid is in the Wenzel contact is very little, can ignore), and super hydrophobic surface 5 that should the zone surrounded forms Cassie contact area 6 with fluid 1.The equal diameters of the external diameter of Wenzel contact area and anchor clamps 3, the side face shaping of fluid 1 between super hydrophobic surface after the processing 5 and anchor clamps 3 is the cydariform of standard, satisfies the shape requirement that flow graph system convection cell is sprawled.The moment of torsion on the plate jig 3 of being applied to that adopts being applied to of measuring under this situation moment of torsion on the plate jig 3 and smooth hydrophobic surface 2 test case (shown in Fig. 4 (b)) obtain compares and can calculate the slip length of fluid on super hydrophobic surface 5, and computing formula adopts computing formula (3).
The present invention is that with the difference of the method for propositions such as Li Jian at first the processing procedure to the surface is different, but all reach the purpose that controlling liquid is sprawled the border, it is follow-up that super hydrophobic surface is carried out the process of rheometer test is also identical, therefore, the correctness of this method can be confirmed by the result in the Li Jian literary composition.
Embodiment two (adopting the cone-plate anchor clamps to measure) as Fig. 3, Fig. 5
Be to adopt cone-plate anchor clamps 4 to measure with the difference of embodiment one, employed fluid slip length computing formula adopts computing formula (4).
Claims (2)
1. based on the super hydrophobic surface fluid slip length method of testing of boundary Control, it is characterized in that: this method is carried out as follows:
1) at first prepares super hydrophobic surface, super hydrophobic surface to preparation is handled, the super hydrophobic surface for preparing is carried out processing procedure is: the processing diameter circular mask littler than anchor clamps diameter, reprocess the mask of another aperture and anchor clamps equal diameters, with the preparation two masks with one heart attached on the super hydrophobic surface; Afterwards the super hydrophobic surface that is covered by mask is carried out hydrophilic treatment, make the super hydrophobic surface of the gap between two masks have hydrophilic coating, present hydrophilicity; Super hydrophobic surface after handling is clamped on the rheometer test platform, carries out chucking position demarcation and anchor clamps mapping; The concrete grammar that super hydrophobic surface after handling is clamped on the rheometer test platform is: super hydrophobic surface is positioned on the test platform, manual mobile anchor clamps make anchor clamps near the surface, the distance of super hydrophobic surface and anchor clamps is less than 500 μ m, the hydrophilic coating zone boundary on the observation super hydrophobic surface and the distance relation on anchor clamps border, fine setting super hydrophobic surface position makes the hydrophilic coating zone boundary equate with the gap at four direction on anchor clamps border;
2) to carrying out the rheometer test operation on the super hydrophobic surface, and under same test condition, the fluid on the smooth hydrophobic surface is carried out the rheometer test operation, obtain the moment of torsion that is applied to when fluid under two kinds of situations is in identical shear rate on the anchor clamps, and calculate slip length according to measuring torquer, the computing formula that anchor clamps are adopted when adopting the cone-plate anchor clamps to measure is:
M wherein
SHAnd M
HBe respectively the moment of torsion that obtains when super hydrophobic surface and smooth hydrophobic surface tested; d
1Be the diameter in the super-hydrophobic zone that hydrophilic region surrounded, d
2Be the overall diameter of hydrophilic region, d
2Equal the anchor clamps diameter; α is cone-plate anchor clamps bus and the angle of testing the plane; The computing formula that anchor clamps are adopted when adopting plate jig to measure is:
b＝(1-M
SH/M
H)D/((d
1/d
2)
4-(1-M
SH/M
H))
M wherein
SHAnd M
HBe respectively the moment of torsion that obtains when super hydrophobic surface and smooth hydrophobic surface tested; d
1Be the diameter in the super-hydrophobic zone that hydrophilic region surrounded, d
2Be the overall diameter of hydrophilic region, d
2Equal the anchor clamps diameter; D is the gap between plate jig and the test plane.
2. the super hydrophobic surface fluid slip length method of testing based on boundary Control according to claim 1, it is characterized in that: the diameter of anchor clamps is Φ 20mm, Φ 40mm or Φ 60mm.
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| CN103675332B (en) * | 2013-12-27 | 2015-07-29 | 大连海事大学 | Device and the measuring method of sliding velocity is measured under a kind of microscale |
| CN106840976B (en) * | 2017-03-10 | 2023-08-29 | 清华大学 | Rheometer-based improved interface sliding parameter measurement device and method |
| CN108645757B (en) * | 2018-05-03 | 2019-12-24 | 华中科技大学 | Device and method for measuring effective sliding length of super-hydrophobic surface |
| CN109387390B (en) * | 2018-11-23 | 2022-04-15 | 江苏大学 | Sediment anaerobic incubator |
| CN115372205A (en) * | 2022-08-12 | 2022-11-22 | 江苏集萃精密制造研究院有限公司 | Rotary rheometer rotor assembly with honeycomb sandwich structure |
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| Xin Li,et.al.Hydration and Dewetting near Fluorinated superhydrophobic plates.《J.AM.CHEM.SOC》.2006,第128卷12439-12447. * |
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