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蚯蚓非光滑体表形貌与降阻特性 总被引:2,自引:1,他引:1
以赤子爱胜蚓(Eisenia foetida)为研究对象,制备了舒张态、静息态、收缩态3种体表试样。利用OLYMPUS体视显微镜及OLYCIATMM3图像分析系统,对蚯蚓体表形貌进行分析,结果表明蚯蚓体表形貌属于典型的波纹形非光滑结构,体部纹理小而密,非光滑单元密度较大,头部纹理大而稀,非光滑单元密度较小。头部舒张态、静息态、收缩态非光滑结构单元体宽度和高度之比分别为1.65︰1︰0.78和0.23︰1︰1.27;而体部舒张态、静息态、收缩态非光滑结构单元体宽度和高度之比分别为1.65︰1︰0.81和0.33︰1︰1.28。利用微黏附力测试系统,对蚯蚓体表展平试样和钢试样进行土壤滑动阻力试验,结果表明蚯蚓体表试样的降阻效果由大到小依次是收缩态、静息态、舒张态;而且,头部比体部降阻效果明显;与钢试样相比,头部和体部收缩态的降阻率分别为39%和29%。该研究可为生物非光滑表面仿生研究以及揭示蚯蚓体表形貌和润滑耦合仿生机制提供基础数据。 相似文献
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研究了弥散Al2O3粒子的尼龙1010基复合涂层和喷涂T8钢—浸渍聚有机硅氧烷的复合涂层两类化学非光滑表面及聚乙烯、聚苯乙烯、尼龙6、尼龙1010、T8钢、45钢和Al2O3粗糙表面的润湿性。导出了弥散球形粒子型化学非光滑表面上液体接触角与其组成相固有接触角关系的方程,该方程与尼龙1010—Al2O3粒子复合涂层表面接触角试验结果吻合良好。在尼龙1010基体中加入适量Al2O3粒子后,液体接触角未发生明显变化;T8钢喷涂层浸渍聚有机硅氧烷后,表面憎水性明显增强;材料的固有接触角越远离90°,表面粗糙性对接触角的影响越明显。 相似文献
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为了探讨激光微造型表面仿生非光滑效应中粗糙度提高的工艺,运用SEM扫描电镜和图像处理技术提取荷叶表面微纳米形貌特征,在犁铧钢(18CrMnTi)表面进行激光微造型表面仿生正交试验研究。研究表明,图像处理中Sobel边缘算法有效地提取了SEM图片表面微纳米形貌层次特征,图像阈值取255时,提取表面形貌特征最多,犁铧钢仿生表面基本上再现了荷叶表面形貌;激光表面微造型极显著因素的主次关系是阈值>打标次数>电流强度,表面仿生最优值处的微造型粗糙度参数,即表面轮廓算术平均偏差(Ra)、微观不平度十点高度(Rz)和最大轮廓高度(Ry)提高的倍数分别为86.11、232.29和116.06。研究结果为激光微造型表面仿生多层次提取表面形貌信息和提高表面粗糙度工艺提供参考。 相似文献
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换热器铝基微细通道微纳结构表面制备及其传热特性 总被引:2,自引:2,他引:0
在农业工程中,微细通道传热技术在储粮仓温度控制、农产品干燥系统和太阳能热水系统有着广泛的应用。该文使用CuCl2溶液刻蚀铝基微细通道表面并采用超声波清洗的方式得到微纳结构表面,呈现出超亲水性;在微纳结构表面的基础上用氟硅烷溶液修饰后得到超疏水表面,只经过砂纸打磨处理的为普通光滑表面。使用3种不同表面的微细通道进行流动沸腾试验,试验工质为R141b,操作压力为142 kPa,在不同质量流率、热流密度下研究不同润湿性表面对传热特性的影响。试验结果表明,在低热流密度下,超疏水表面有着最佳的传热特性,相对于普通光滑表面传热系数最大提高31.6%;当热流密度升高到一定值后,超亲水表面的传热系数最大,相对于普通光滑表面传热系数最大提高20.6%。继续提高加热功率,超疏水表面的传热系数开始下降,甚至低于普通光滑表面。该文通过改变微通道的表面特性,研究微纳结构表面对微通道流动沸腾传热特性的影响,为制造出更高换热特性的微细通道换热器提供了新的思路,从而实现节能与高效传热。 相似文献
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Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces is evaluated by a reformulation of the Cassie‐Baxter equation, assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor that depends on the Young’s Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water‐wetting behaviours ranging from wettable to extremely hydrophobic, with contact angles > 150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS‐coated smooth glass plates, except for the clay soil. Contact angles measured on plane surfaces were related to contact angles measured on rough grain surfaces using the new model based on the combined Cassie‐Baxter Wenzel equation, which takes into account the particle packing density on the sample surface. 相似文献
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植被分布对地表糙率影响 总被引:1,自引:0,他引:1
[目的]分析在植被淹没或非淹没状态不同植被覆盖密度影响下,地表糙率的变化规律与特征,为进一步研究植被对地表糙率的影响提供参考。[方法]试验以塑料棒模拟植被分布,模拟出不同密度,分别进行放水试验。[结果]在植被淹没与非淹没状态下地表糙率的变化不同,在非淹没状态时,地表糙率随着平均水深的增加呈减小的趋势,在淹没水深小时,地表糙率随着平均水深的增加而先增大后减小,而当淹没水深很大时,地表糙率趋向于一个稳定值。[结论]地表糙率取值随植被覆盖密度的增大而增大;同一下垫面情况下,不同的水流方向,地表糙率取值不相同。 相似文献
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A quantitative approach is presented to the analysis of slope roughness on debris covered slope in an arid area. The surface roughness increases with increasing slope angle. As slope flow depth is very thin, slope roughness affects the flow line. Hence the angle of the flow line — the effective slope — is less than the slope angle. 相似文献
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为查明黄土区林下地表随机糙度的特征及地表随机糙度随植物生长季的变化规律,以晋西黄土区蔡家川流域13个径流小区为研究对象,利用针状糙度计对其地表随机糙度进行测量,分析不同林分密度的地表随机糙度。结果表明:地表随机糙度与林分密度呈较好的正相关;13个径流小区在3个生长时期地表随机糙度不同,具体表现为生长旺盛期>生长初期>生长末期,呈现倒"V"型;同一地块,荒草坡地表随机糙度大于灌木林地表随机糙度;天然林的地表随机糙度变化幅度小于人工林的地表随机糙度。 相似文献
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The ability to quantitatively and spatially assess soil surface roughness is important in geomorphology and land degradation studies. This paper describes the results of an experiment designed to investigate whether hyperspectral directional reflectance factors can describe fine‐scale variations in soil surface roughness. A Canadian silt loam soil was sieved to an aggregate size range of 1–4.75 mm and exposed to five different artificial rainfall durations to produce soils displaying progressively decreasing levels of surface roughness. Each soil state was measured using a point laser profiling instrument at 2 mm spatial resolution, in order to provide information on the structure and spatial arrangement of soil particles. Hyperspectral directional reflectance factors were measured using an Analytical Spectral Devices FieldSpec Pro Spectroradiometer (range 350–2500 nm), at a range of measurement angles (θr=?60° to +60°) and illumination angle conditions (θi= 28°–74°). Directional reflectance factors varied with illumination and view angles, and with soil structure. Geostatistically‐derived indicators of soil surface roughness (sill variance) were regressed with directional reflectance factors. The results showed a strong relationship between directional reflectance and surface roughness (R2= 0.94 where θr=?60°, θi= 67°–74°). This fine‐scale quasi‐natural experiment allowed the control of slope, initial aggregate size and rainfall exposure, permitting an investigation into factors affecting a soil’s bidirectional reflectance response. This has highlighted the relationship between fine‐scale variations in surface roughness, illumination angle and reflectance response. The results show how the technique could provide a quantitative measure of surface roughness at fine spatial scales. 相似文献
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盐渍化土壤水分微波雷达反演与验证 总被引:2,自引:1,他引:1
土壤介电常数是微波遥感进行土壤含水率测量的物理基础,尤其介电常数实部是必须解决的问题,土壤介电特性的研究显得尤为重要。该文目的是试验与评价C波段RADARSAT-2 SAR(synthetic aperture radar)数据模拟土壤介电特性,进而反演土壤水分的性能。以受盐渍化影响较严重的内蒙古河套灌区解放闸灌域为试验区,首先回归分析了介电常数实部与SAR四极化后向散射系数、地表粗糙度的复杂关系,并与Oh经验模型对照,其决定系数R2为0.859 7,模拟精度较高;然后验证常用的2个介电常数模型,Dobson半经验模型、Hallikainen简化实部经验模型模拟的介电常数实部与实测值的决定系数R~2分别为0.935 9、0.869,表明2个模型均能模拟地表土壤水分与介电常数实部的密切关系;最后构建了Dobson模型、Hallikainen简化实部模型反演土壤含水率的模型,并与统计回归模型比照,其模拟数值与土壤实测值的决定系数R2分别为0.803 8、0.737 4、0.842 1,均方根误差RMSE分别为5.2%、5.7%、5%。Dobson模型与统计回归模型反演结果与实地土壤墒情分布较为吻合,具有良好的精度和适用性,从而建立了一个较为完整的土壤介电特性研究体系,为微波遥感监测土壤水分奠定了基础。 相似文献
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Soil water repellency is a transient soil property varying with soil–water contact time. The purpose of the present study was to determine the time dependence of the sessile drop contact angle and its relation to repellency persistence estimated using the water drop penetration time (WDPT) test with hydrophobized sand. The contact angle decreased exponentially and almost reached apparent equilibrium after 20 min of soil–water contact time. Time dependence of the contact angle can mainly be attributed to the adsorption of water molecules onto low-energy hydrophobic organic matter surfaces. Contact angles initially greater than 90° decreased to less than 90° within about 40 s. However, the WDPT of these samples was longer than 3600 s. The WDPT responded to the initial contact angle, but not to the contact angle decreased with soil–water contact time. This was considered to be caused by differences in the surface free energy between the surface and the lower layers. Repellency persistence, or the WDPT, can be considered to be the time taken to increase the surface free energy to overcome water repellency, not only on the surface in contact with the droplet, but also in the adjacent layers below the surface. 相似文献
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《Soil Science and Plant Nutrition》2013,59(3):366-370
Abstract Gravity-driven fingered flow may readily occur in dry sand layers with small capillary force at the same order of magnitude as gravitational force. Capillary force is related to the contact angle. The present study examined the effects of contact angle on fingered flow development, finger size and fingertip velocity during non-ponding infiltration into dry sand layers. For contact angles of 48–87°, an induction zone always formed in the sand layer, and only one finger developed from the induction zone. Fingertip width reached a minimum value when the contact angle was approximately 70°, and the width and velocity of fingertips were negatively correlated. This finding suggests that a contact angle of approximately 70° has a physical significance for fingered flow to determine fingertip velocity and width. In addition, when the contact angle was 91°, the supplied water did not spontaneously penetrate the sand surface; instead, water drops built up on the surface and two fingers directly formed from the surface. This indicates that 90° is indeed the critical contact angle for water repellency and affects fingered flow development during non-ponding infiltration. 相似文献