Numerical investigation on the influence of surface tension and viscous force on the bubble dynamics with a CLSVOF method

Zhiying Wang,Yikai Li,Biao Huang,Deming Gao 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6

We numerically investigated the rising of bubbles in a quiescent liquid layer. The numerical simulation is performed by solving the incompressible, multiphase Navier-Stokes equations via computational code in axisymmetric coordinates using a Coupled level-set and volume-of-fluid (CLSVOF) method. The numerical results show that the CLSVOF method with a novel algebraic relation between F and f for axisymmetric two-phase flows not only can predict the bubble surface accurately, but also overcome the deficiency in preserving volume conservation. The effects of the Reynolds number Re and the Bond number Bo on the bubble deformation and its motion are investigated. The results show that with the increasing of Re (10 < Re < 150), the bubble shape transfers from oblate ellipsoidal cap to toroidal when Bo = 116. With the increasing of Bo (10 < Bo < 700), the bubble shape transfers from oblate ellipsoidal to toroidal when Re = 30. Although the toroidal bubble shapes are reached in these two cases, the transition modes are different. For the case Bo = 116, the bubble front is pierced by an upward jet from the rear of the bubble. While for the case Re = 30, the rear of the bubble is pierced by a downward jet from the front part.

Drag reduction characterizations of turbulent channel flow with surfactant additive by proper orthogonal decomposition and wavelet transform

Lu Wang,Zhiying Zheng,Weihua Cai,Fengchen Li 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.1

To explore the drag-reducing characteristics of turbulent channel flows with surfactant additive at relatively high Reynolds number from the perspectives of energy spectrum and multi-scale resolution, the two-dimensional fluctuation velocity fields of turbulent channel flows with/without surfactant additive at Reynolds number of Re = 590 obtained by large eddy simulation are decomposed by two-dimensional proper orthogonal decomposition (POD) and wavelet transform (WT). POD results show that the low-order eigenmode occupying most energy can be used to capture large-scale vortex structures, and fewer eigenmodes can be employed to capture coherent structures (CSs) in surfactant solution case compared with that in the Newtonian fluid. The spatial structures depicted by POD eigenmode state that buffer layer has a tendency to move towards the center of the channel in surfactant solution. Through wavelet analysis of fluctuation velocity fields in the streamwise-wall-normal planes, it is found that CSs mainly distribute in the near-wall region and the amount of CSs is smaller in surfactant solution. The results of local Reynolds shear measure (LRM) show that local contribution of CSs to the intermittency in turbulent channel flow of surfactant solution decreases, indicating the inhibition of intermittency by surfactant additive. In order to investigate the drag-reducing characteristics at different locations along the wall-normal direction, the fluctuation velocity fields in the streamwise-spanwise planes at different wall-normal locations are decomposed by two-dimensional WT. The results show that surfactant additive mainly affects the flow in the near-wall region (especially in the buffer layer) and thus induces drag reduction effect.

Numerical investigation of the influence of structures in bogie area on the wake of a high-speed train

Dongwei Wang,Chunjun Chen,Zhiying He 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.5

The flow around a high-speed train with three underbody structures in the bogie area is numerically investigated using the improved delayed detached eddy simulation method. The vortex structure, pressure distribution, flow field structure, and unsteady velocity of the wake are analyzed by vortex identification criteria Q, frequency spectral analysis, empirical mode decomposition (EMD), and Hilbert spectral analysis. The results show that the structures of the bogie and its installation cabin reduce the momentum of fluid near the tail car, thus it is easy to induce flow separation and make the fluid no longer adhere to the side surface of the train, then forming vortices. Under the action of the vortices on the side of the tail car, the wake vortices have a trend of spanwise motion. But the deflector structure can prevent the separation on the side of the tail car. Besides, the bogie fairings do not affect the formation process and mechanism of the wake vortices, but the fairings prevent the low-speed fluid in the bogie installation cabin from flowing to the side of the train and reduce the number of the vortices in the wake region.

Biological Potential of Bioorganic Fertilizer Fortified with Bacterial Antagonist for the Control of Tomato Bacterial Wilt and the Promotion of Crop Yields

( Kai Wu ),( Zhiying Fang ),( Lili Wang ),( Saifei Yuan ),( Rong Guo ),( Biao Shen ),( Qirong Shen ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.10

The application of Bacillus sp. in the biological control of plant soilborne diseases has been shown to be an environmentally friendly alternative to the use of chemical fungicides. In this study, the effects of bioorganic fertilizer (BOF) fortified with Bacillus amyloliquefaciens SQY 162 on the suppression of tomato bacterial wilt were investigated in pot experiments. The disease incidence of tomato wilt after the application of BOF was 65.18% and 41.62% lower at 10 and 20 days after transplantation, respectively, than in the control condition. BOF also promoted the plant growth. The SQY 162 populations efficiently colonized the tomato rhizosphere, which directly suppressed the number of Ralstonia solanacearum in the tomato rhizosphere soil. In the presence of BOF, the activities of defense-related enzymes in tomato were lower than in the presence of the control treatment, but the expression levels of the defense-related genes of the plants in the salicylic acid and jasmonic acid pathways were enhanced. It was also found that strain SQY 162 could secrete antibiotic surfactin, but not volatile organic compounds, to suppress Ralstonia. The strain could also produce plant growth promotion compounds such as siderophores and indole-3-acetic acid. Thus, owing to its innate multiple-functional traits and its broad biocontrol activities, we found that this antagonistic strain isolated from the tobacco rhizosphere could establish itself successfully in the tomato rhizosphere to control soilborne diseases.

Screening and identification of Aspergillus activity against Xanthomonas oryzae pv. oryzae and analysis of antimicrobial components

Bei Jiang,Zhiying Wang,Chuxuan Xu,Weijia Liu,Donghua Jiang 한국미생물학회 2019 The journal of microbiology Vol.57 No.7

To screen for Aspergillus activity against Xanthomonas oryzae pv. oryzae and analyse the antimicrobial components involved, 60 Aspergillus spp. were isolated and purified from fruits, soil and other habitats. As-75, an Aspergillus strain that can antagonize Xanthomonas oryzae pv. oryzae, was identified based on the zone of inhibition formed during co-culture. According to morphological, ITS rDNA gene sequencing and phylogenetic tree results, the strain showed close homology to Aspergillus sclerotiorum. The biochemical characterization tests showed that the fermentation broth of strain As-75 exhibited a high capacity for environmental adaptation. The results of the antimicrobial spectrum experiments demonstrated that As-75 exhibited fairly strong antagonistic activity against five plant pathogenic fungi and six plant pathogenic bacteria in vitro. The fermentation broth of strain As-75 displayed maximum stability under fluorescent illumination at temperatures below 60°C at pH 6.5. A substance with antagonistic activity was obtained from strain As-75 via fractional extraction, silica gel column chromatography and thinlayer chromatography. Through mass spectrometry, nuclear magnetic resonance and electrospray ionization mass spectrometry (ESI-MS) analyses, the target compound was identified as (2Z)-2-butenedioic acid-2-(1-methylethenyl)-4-methyl ester; its molecular weight of 170.06 daltons and formula of C8H10O4 identify it as a novel compound. Trials of the preventative and curative effects demonstrated that compound S1 exhibited a better control efficiency than the control against rice bacterial blight. Additionally, the M1 processing method was better, and the efficiency of compound S1 in preventing rice bacterial blight in six rice varieties, TN1, IR24, ZF802, Zhonghua 11, Wuyunjing 21, and Nipponbare, was 78.3%, 77.5%, 74.2%, 75.3%, 70.9%, and 72.1%, respectively.

Molecular Cloning of Three UDP-Glucuronate Decarboxylase Genes That Are Preferentially Expressed In Gossypium Fibers From Elongation to Secondary Cell Wall Synthesis

Yuxin Pan,Xingfen Wang,Hengwei Liu,Guiyin Zhang,Zhiying Ma 한국식물학회 2010 Journal of Plant Biology Vol.54 No.5

UDP-xylose (UDP-Xyl) is a nucleotide sugar used as substrate for producing non-cellulose materials, e. g., hemicellulose and pectic polysaccharide, in the fibers of cotton (Gossypium). Its biosynthesis is catalyzed from UDP-glucuronic acid (UDP-GlcA) by UDP-glucuronate decarboxylase (UXS). Here, we first cloned GhUXS1 in Gossypium hirsutum and Gossypium barbadense based on a transcript-derived fragment that originated from our cDNA–AFLP transcriptome profiling in cotton. GhUXS2and GhUXS3 were also isolated via homology-based cloning. GhUXS nucleotide sequences were identical between the two species, and the deduced amino acid residues had the conserved motif of the UXS family, i.e.,GxxGxxG, Ser residues, and YxxxK. GhUXS1 was expressed in Escherichia coli and generated UXS activity that converted UDP-GlcA to UDP-Xyl. Semiquantitative RT-PCR results showed that GhUXSs transcripts were preferentially expressed during fiber development, from elongation through the stage of secondary cell wall synthesis. Although at the same number of days postanthesis they were more abundant in G. hirsutum, expression was sustained for a longer period in G. barbadense. These different patterns of expression may affect quality and partially explain why the latter species has better fiber strength.

Functional Analysis of a Subtilisin-like Serine Protease Gene from Biocontrol Fungus Trichoderma harzianum

Haijuan Fan,Zhihua Liu,Rongshu Zhang,Na Wang,Kai Dou,Gulijimila Mijiti,Guiping Diao,Zhiying Wang 한국미생물학회 2014 The journal of microbiology Vol.52 No.2

The subtilisin-like serine protease gene ThSS45 has beencloned from Trichoderma harzianum ACCC30371. Its codingregion is 1302 bp in length, encoding 433 amino acids,with a predicted protein molecular weight of 44.9 kDa andpI of 5.91. ThSS45 was shown by RT-qPCR analysis to bedifferentially transcribed in response to eight different treatments. The transcription of ThSS45 was up-regulated whengrown in mineral medium, under carbon starvation, andnitrogen starvation, and in the presence of 1% root powder,1% stem powder, and 1% leaf powder derived from Populusdavidiana × P. bolleana (Shanxin poplar) aseptic seedlings. The highest increase in transcription approached 3.5-foldthat of the control at 6 h under induction with 1% poplarroot powder. The transcription of ThSS45 was also slightlyup-regulated by 1% Alternaria alternata cell wall and 5% A. alternata fermentation liquid. Moreover, the analyses of codingand promoter regions of ThSS45 homologs indicatedthat serine protease may be involved in both mycoparasitismand antibiotic secretion. ThSS45 was cloned into the pGEX-4T-2 vector and then expressed in Escherichia coli BL21. Therecombinant protein, with an expected molecular weight ofapproximately 69 kDa, was then purified. When transformantBL21-ss was induced with 1 mM IPTG for 6 h, thepurified protease activity reached a peak of 18.25 U/ml atpH 7.0 and 40°C. In antifungal assays the purified proteaseobviously inhibited the growth of A. alternata mycelia.

A Dislocation Density Based Crystal Plasticity Model of 3D Complex Sheet Metal Forming

Haiming Zhang,Xianghuai Dong,Qian Wang,Zhiying Chen 한국소성가공학회 2011 기타자료 Vol.2011 No.8

A dislocation density based crystal plasticity model is used to simulate sheet metal forming processes under different temperature. In the present model, dislocation densities in each slip system are taken as internal state variables. An extended Kocks-Mecking-Estrin evolution law is adopted to describe the athermal storage, and the strain rate and temperature sensitive annihilation, of dislocation densities. The critical resolved stress on a specified slip system is related with dislocation densities in all slip systems, the corresponding mesoscopic coefficients of interaction between different slip systems are determined by recent dislocation dynamics simulations. On the basis of thermally activated dislocation motion, this physically based model is capable of describing the softening resulted from dynamic recovery. This model incorporated with a hyperelastic constitutive law is then implemented into an explicit finite element code, to make it deal with the strong nonlinear problems more efficiently. An iteration-free semi-implicit method, which is more suitable for explicit FEM, is adopted as the integration algorithm of the model. This model is used to investigate the deformation characteristics of warm forming of Al-Mg alloy under different temperatures. The simulation results show that the model is robust and efficient, has the potential to be used in the practical engineering simulation. It also confirms that the micromechaincs models can be used to simulate conventional sheet metal forming.

UTrustDisk: An Efficient Data Protection Scheme for Building Trusted USB Flash Disk

( Yong Cheng ),( Jun Ma ),( Jiangchun Ren ),( Songzhu Mei ),( Zhiying Wang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.4

Data protection of removable storage devices is an important issue in information security. Unfortunately, most existing data protection mechanisms are aimed at protecting computer platform which is not suitable for ultra-low-power devices. To protect the flash disk appropriately and efficiently, we propose a trust based USB flash disk, named UTrustDisk. The data protection technologies in UTrustDisk include data authentication protocol, data confidentiality protection and data leakage prevention. Usually, the data integrity protection scheme is the bottleneck in the whole system and we accelerate it by WH universal hash function and speculative caching. The speculative caching will cache the potential hot chunks for reducing the memory bandwidth pollution. We adopt the symmetric encryption algorithm to protect data confidentiality. Before mounting the UTrustDisk, we will run a trusted virtual domain based lightweight virtual machine for preventing information leakage. Besides, we prove formally that UTrustDisk can prevent sensitive data from leaking out. Experimental results show that our scheme`s average writing throughput is 44.8% higher than that of NH scheme, and 316% higher than that of SHA-1 scheme. And the success rate of speculative caching mechanism is up to 94.5% since the access pattern is usually sequential.