Jianqiao Li

Wetting Behaviours of a Single Droplet on Biomimetic Micro Structured Surfaces

Natural surfaces with super hydrophobic properties often have micro or hierarchical structures. In this paper, the wetting behaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated. A theoretical model is proposed to study wetting transitions. The results of theoretical analysis are compared with those of experiment indicating that the proposed model can effectively predict the wetting transition. Furthermore, a numerical simulation based on the meso scale Lattice Boltzmann Method (LBM) is performed to study dynamic contact angles, contact lines, and local velocity fields for the case that a droplet displays on the micro structured surface. A spherical water droplet with rs = 15 µm falls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·s−1 and an initial vertical distance of 20 µm from droplet centre to the top of pots. In spite of a higher initial velocity, the droplet can still stay in a Cassie state; moreover, it reaches an equilibrium state at t ≈ 17.5 ms, when contact angle is 153.16° which is slightly lower than the prediction of Cassie-Baxter’s equation which gives θCB = 154.40°.

Restudies on Body Surface of Dung Beetle and Application of Its Bionics Flexible Technique

A scanning electron microscope was used to observe the structures of the setae on the surface of a dung beetle Copris ochus, Motschulsky. There are lots of setae on the body surface, especially on the ventral part surface and lateral to the legs which are different in size, arrangement and shape. These setae have different lengths and many thorns on the whole seta. The top ends of these setae stand up without furcations which direct uprightly towards the surface of the touched soil. By the method of removing these setae, getting the insect weight before and after digging into the dung we affirm farther that the setae on the beetle body surface form the anti-stick and non-adherent gentle interface. The soil machines and components made by imitating the gentle body surface of beetles have favorable non-adherent results.

Biomimetic Approaches to Functional Surfaces, Surface Wetting and Fluids Drag Reduction

In the natural world,plants and animals haveevolved over time to best adapt to the environment.Theyinteract very effectively with the surrounding environmentby exchanging energies and mass flow across theircuticles of specific micro structures and functions toachieve perfect energy balance.Such different functionsmay include the limitation of uncontrolled loss of water,protection from solar radiation,micro effect of inducedturbulence on flow drag reduction,defence againstpathogens,changing surface wettability and hydropho-

Bionic Design for Reducing Adhesive Resistance of the Ridger Inspired by a Boar’s Head

The main feature of the boars head used to root around for food is the front part, which is similar to the ridger in terms of function, load, and environment. In this paper, the boars head was selected as the biological prototype for developing a new ridger. The point cloud of the head was captured by a 3D scanner, and then, the head surface was reconstructed using 3D coordinates. The characteristic curves of the front part of the boars head were extracted, and then, five cross-sectional curves and one vertical section curve were fitted. Based on the fitted curves, five kinds of bionic ridgers were designed. The penetrating resistances of the bionic ridgers and traditional ridger were tested at different speeds in an indoor soil bin. The test results showed that bionic ridger B had the best penetrating resistance reduction ratio of 16.67% at 4.2 km/h velocity. In order to further evaluate the performance of the best bionic ridger (bionic ridger B), both the bionic ridger and traditional ridger were tested in a field under the same working conditions. The field results indicate that the bionic ridger reduces penetrating resistance by 6.91% compared to the traditional ridger, and the test results validate that the bionic ridger has an effect on reducing penetrating resistance.

An Experimental Study on the Gait Patterns and Kinematics of Chinese Mitten Crabs

Despite the many studies on eight-legged animals and the importance of their mechanics of terrestrial locomotion, the mechanical energy of crabs in voluntary locomotion on uneven, unpredictable terrain surfaces has received little attention thus far. In this paper, motion video images of Chinese mitten crab (Eriocheir sinensis Milne-Edwards) locomotion on five types of terrains were recorded using a high-speed three-dimensional (3D) recording video system. The typical variables of locomotion such as gait patterns, duty factor, mechanical energy of the mass center, mass-specific rate of the total mechanical power of the mass center, and percentage recovery, were analyzed. Results show that the Chinese mitten crab uses random gaits instead of the alternating tetrapod gait with the increasing terrain roughness. The duty factors of the rows of the leading legs are greater for all terrains than those of the rows of the trailing legs. On smooth terrain, the duty factors of the rows of the trailing legs are greater than that on rough terrains. Kinematic measurements and calculations reveal that similar to mammals, birds, and arthropods, the Chinese mitten crab uses two fundamental gaits to save mechanical energy: the inverted pendulum gait and the bouncing gait. The bouncing gait is the main pattern of mechanical energy conservation. The low probability of injury and energy expenditure due to adaptations to various terrains induce the Chinese mitten crab to modify the mass-specific rate of the total mechanical power of the mass center. The statistical results of percentage recovery also reveal that the Chinese mitten crab has lower energy recovery efficiency over rough terrains compared with smooth terrains.

Pressure-Bearing Parameter Identification for Martian Soil Based on a Terramechanics Model and Genetic Algorithm

AbstractA wheel-terrain interaction mechanics model based on terramechanics and simplified force and moment reconstruction is introduced. The model comprises pressure-bearing parameters (combined d...