Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the mechanism of drag reducing agents and the influencing factors of drag reduction characteristics. The factors affecting the degradation of polymer additives and the anti-degradation properties of surfactants are discussed. A mixture of polymer additive and surfactant has the characteristics of high shear resistance, a lower critical micelle concentration (CMC), and a good drag reduction effect at higher Reynolds numbers. Therefore, this paper focuses more on a drag reducing agent mixed with a polymer and a surfactant, including the mechanism model, drag reduction characteristics, and anti-degradation ability.

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The biomimetic superhydrophobic surface derived from lotus effect is one of the hotspot issues in recent years and also a specific application case of biomimetic in modern industry. Based on the excellent characteristics of bionic superhydrophobic surface, such as self-cleaning, anti-icing, drag reduction, and anti-corrosion, it has great application value in the fields of industry, military, and biomedicine. Based on the effect of water contact angle and water sliding angle of superhydrophobic surface on the hydrophobicity, we discussed the wetting behavior of biomimetic superhydrophobic surface, the important properties of biomimetic superhydrophobic surface were reviewed in detail, and we provided the necessary theoretical basis for the application of superhydrophobic surface. The methods of fabrication of biomimetic superhydrophobic surface were summarized and elaborated three kinds of low-cost and simple methods of spraying, chemical etching, and flame treatment, and the development trend of biomimetic superhydrophobic surface was also prospected.

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This article presents a new approach aiming to reducing pump vibration by modifying its baseplate structure. The finite element models of the vertical pump were established and validated by the experimental impact test. The natural frequencies of pump were mapped in both experimental and numerical methods. The weak stiffness of the baseplate was identified as the root cause for the pump vibration. A topology optimization was used for enhancing the stiffness of baseplate and controlling its weight. The new baseplate was designed according to the inputs from optimization results and manufactured by the casting method. Both the vibration tests and the numerical simulations were carried out to investigate the vibration behaviors of the optimized pump model. The differences of vibration characteristics between original and optimized pumps were evaluated using 1/3 octave-band filter technique. Results show that the vibration was suppressed, and the resonance at 31.5 Hz was eliminated using the optimized baseplate. In particular, the maximum vibration amplitude of the vertical pump was reduced from 4.05 to 1.75 mm/s at the low flow rate condition. It was experimentally confirmed that the vibration amplitude of the optimized model complies with the requirements of the International Organization for Standardization standard and ensures the pump can operate stable for a long time.