**1. Introduction**

LNG is mostly methane with small amounts of ethane, propane, butane and nitrogen, which is expected to be the second-largest energy source in energy composition in 2030 [1]. However, there may be a leak of liquefied natural gas (LNG) in the presence of an ignition source that will cause a fire or explosion in a fully or partially hazardous environment [2].

In view of this, several studies have been published on storage tank accidents [3–6]. Scholars in China and overseas have conducted many studies on the prediction of possible hazards associated with LNG vapor dispersion. Koopman et al. [7] carried out the Burro series of tests in 1980 to observe the diffusion of LNG vapor clouds under different conditions after LNG leaked to the water surface. It was found that the leakage mode of LNG has a certain influence on the vapor cloud diffusion. In 1983, the Coyote series of tests [8] were conducted to study the ignition and flash evaporation processes of LNG, and the

**Citation:** Li, X.; Zhou, N.; Chen, B.; Zhang, Q.; Rasouli, V.; Liu, X.; Huang, W.; Kong, L. Numerical Simulation of Leakage and Diffusion Process of LNG Storage Tanks. *Energies* **2021**, *14*, 6282. https://doi.org/10.3390/ en14196282

Academic Editor: Marcin Kami ´nski

Received: 28 July 2021 Accepted: 16 September 2021 Published: 2 October 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

rapid phase transition, vapor cloud diffusion and pool fire were all observed in this test. Brown et al. [9] carried out Falcon series of experiments to study the leakage and diffusion of LNG under obstacles. They accurately evaluated the effectiveness of the fence so as to mitigate the harm of LNG gas cloud diffusion.

In addition, several mathematical models have been developed to simulate heavy gas diffusion based on experimental data, such as DEGADIS, SLAB [10], FEM3 [11,12], etc. First of all, field tests can reproduce the actual situation of LNG leakage and diffusion; in addition, the cycle was too long and the repeatability was poor. Therefore, CFD simulation was used as a promising alternative to calculate the diffusion distance of LNG. Giannissi et al. [13] simulated the LNG diffusion under an open and obstructed condition based on Falcon series experiments. It was proved that the leak source model greatly affected LNG diffusion, and the best case to simulate the leakage source was to model the source as having two phases. Vílchez et al. [14] used the DEGADIS model to predict the explosive distances of vapor clouds after LNG leakage and they defined the diffusion safety factor (DSF) to estimate these distances. Li et al. [15] evaluated the effect of safety clearance on the diffusion of cylindrical floating LNG with FLACS software. The results demonstrated that the safety gap increased the size of the gas cloud far from the cylindrical FLNG release position but decreased the size of the gas cloud near the release position.

Zhang et al. [16] studied the process of LNG leakage and diffusion in different wind directions. The results showed that the LNG spread farthest along the horizontal downwind direction. Marsegan et al. [17] carried out a numerical simulation of LNG diffusion under active and passive barriers and found that the active barrier effectively reduced the diffusion area of LNG by accelerating the entrainment between air and gas. Nguyen et al. [18] conducted a liquid pool evaporation experiment with different leak rates on the water surface. They proposed a model to express the function relationship between evaporation rate, leakage rate and time based on the experimental results and one-dimensional heat conduction model. Gopalaswami et al. [19] developed a transient three-dimensional multiphase model in CFX based on the comprehensive test data and numerical simulation data, which was found that wind affected the evaporation and diffusion of LNG by carrying additional heat and unsaturation. Ikealumba et al. [20] studied the effects of atmospheric and ocean stability on LNG diffusion where they found that the instability caused by the waves would aggravate the leakage hazard of LNG ships. Luo et al. [21] proposed an integrated multiphase CFD model to simulate the complete process of LNG leakage on the water surface, concluding that water storage would shorten the horizontal diffusion distance of the gas cloud. Dasgotra et al. [22] simulated the diffusion of heavy gas in natural gas storage facilities. They found that the average diameter of the gas cloud ranged from 0 to 500 m under relatively stable weather conditions. Giannissi et al. [23] investigated the effect of environmental humidity on the diffusion of LNG, and concluded that in the case of high environmental humidity, the explosion distance of gas cloud would be reduced.

The above studies mainly focus on the potential hazards which are associated with LNG leakage and the influence degree of external environmental factors on the dispersion effect of LNG leakage. However, few considerations have been given to phase change. Therefore, in this study, the effect of phase change on dispersion during LNG release is studied to analyze the behavior characteristics of LNG liquid pool expansion and gas cloud diffusion, and the effect of the leaking aperture on the gas cloud diffusion process is also studied.


**Acknowledgements**

ly. Further research on such issues could launch to plasma polymerization process to large-

The properties of CNTs and its application in the preparation of polymer hybrid materials have been very active research fields over the last decade. The preparation of polymer-CNTs hybrid materials faces considerable research challenges because their performance depends on the dispersion of CNTs in the polymer matrix and interfacial interactions between the CNTs and the polymer. In order to achieve the maximum performance, the surface modifi‐ cation of CNTs through several functionalization methods is one of the most used strategies to achieve this goal. Nowadays, the global environmental trends provide convincing reasons for exploring greener chemistry methods for functionalization of CNTs, which represent ad‐

Microwave, ultrasound and plasma technology have emerged as promising green ap‐ proaches since they have demonstrated to reduce the energy consumption, shorter reaction times and increase yields. These greener methods offer a range of energies that are not avail‐ able from other conventional sources such as thermal, so leave open the possibility to ex‐ plore more efficient functionalization routes, taking into account the 12 principles of "*Green*"

Despite the progress described within this chapter, there are still considerable research chal‐ lenges within this field that remain to be addressed. The successful functionalization of CNTs depends on availability of active sites on CNTs surface; however, the mechanisms that generate these sites remain unclear. Therefore, an in-depth understanding of the mecha‐ nisms of interaction between microwave/ultrasound/plasma-CNTs is required. For satisfy‐ ing this need, further studies on correlation between the irradiation conditions and the level of the functionalization are suggested, in order to establish the most efficient and greener

In addition, the incorporation of a dispersion stage of CNTs in gas phase previous to irradia‐ tion is highly recommended, because the surface area exposed to irradiation is increased

As a general statement, the "*Green*" chemistry methods based on microwave, ultrasound and plasma energy can be easily incorporated to emerging fields of nanotechnology, in par‐ ticular into strategies for preparation polymer-CNTs hybrid materials. However, there are

and therefore the interactions with the matter are highly promoted.

still a number of important research challenges to study.

scale applications.

**5. Summary and final remarks**

186 Syntheses and Applications of Carbon Nanotubes and Their Composites

ditional research challenges.

chemistry as a framework.

conditions for each particular system.

The authors acknowledge the financial support from project 132699 funded by CONACyT, México.


**Acknowledgements**

histone ubiquitination and prevents its nuclear translocation and ubiquitin ligase activity [163]. Human PIWIL4 function is crucial in accurate spermatogenesis, and genetic polymorphisms of PIWIL4 gene are significantly correlated with defective spermatogenesis associated

In *Drosophila*, PIWI proteins induce ovary tissue morphogenesis through c-Fos inactivation at posttranscriptional level [165]. They are implicated in development of eye color [144]. In silkworm, fempiRNA, a piRNA located on female W-chromosome, is pivotal in sex determination by repressing masculinization mRNA at posttranscriptional level [167]. At early stages of human embryonic lungs development, PIWIL1, PIWIL2, and PIWIL4 levels of expression are strongly upregulated from 6th week to 9th week and then decline [168]. In human, PIWIL1 and PIWIL2 have crucial role in neural polarization and radial migration during maturation

The PIWI-piRNA pathway has pivotal role in numerous physiological processes.

PIWI proteins and piRNAs are instrumental in synaptic plasticity and stabilization of longterm memory through serotonin-dependent suppression of CREB2 at transcription level that is induced by methylation of CpG islands in the promoter region of the *CREB2* gene [59]. In rodents, several piRNAs are upregulated in hippocampal neurons and Miwi associated with piRNAs control dentritic spine development and morphogenesis [149]. Mili expression is associated with anxiety and locomotory drive [54]. In humans, PIWIL1 controls cortical neuron activity through modulation of microtubule-associated proteins (MAPs) expression [169]. Furthermore, mutations of PIWIL2 and PIWIL4 are significantly correlated with autism [170].

PIWI proteins and piRNAs have crucial role in self-renewal, regeneration, and homeostasis. In planarian *Schmidtea mediterranea*, SMEDWI-2 and SMEDWI-3 increase division of adult stem cells to induce regeneration in injured tissues [113]. In jellyfish, Cniwi is upregulated during transdifferentiation of striated muscle into smooth muscle [171].  PIWIL2 and PIWIL4 modulate pancreatic β-cells function and insulin secretion. Alterations of their levels

of expression were observed in diabetic conditions [55].

with spermatogenesis defect and male infertility [164].

of the cerebral cortex region of the brain [59].

*<IP_ADDRESS>. Organogenesis*

248 Chromatin and Epigenetics

*3.4.8. Physiological processes*

*<IP_ADDRESS>. Brain plasticity*

*<IP_ADDRESS>. Regeneration*

retinal cells [130].

*<IP_ADDRESS>. Metabolism*

This work was supported by grant INCa-DGOS-4654.


*2.2. Chromosomal Location, Phylogenetic Analysis, Prediction of Subcellular Localization, Gene Structure, Cis-Acting Elements, and Conserved Motifs Analyses*

For gene location visualization on the respective chromosomes, the retrieved gene ID information in gtf3 file format of all the *GhSAMSs* was used in Tbtools software to map the genes onto the chromosomes. The coding sequence of *GhSAMS* members was downloaded from the official website of Phytozome (https://Phytozome.jgi.doe.gov; accessed on 9 June 2020). Homolog genes from closely related plant species (Table S1) were also downloaded from the Phytozome website and later used to perform the phylogenetic analysis via the neighbor-joining method in the MEGA 7.0 program, with the specification of 1000 bootstrap replicates [26]. ClustalX software was used to align all the protein sequences before generating a phylogenetic tree diagram for evolutionary relationships analysis [27]. The Poisson correction was applied to estimate the distance between sequences. WoLF Psort online software was used to predict *GhSAMS* genes' subcellular localization (https://wolfpsort.hgc.jp; accessed on 15 June 2020) [28].

*GhSAMS* genes' structure analysis was conducted via the Gene Structure Display Server website (http://gsds.cbi.pku.edu.cn; accessed on 19 June 2020) [29]. In-depth prediction of the cis-regulatory DNA elements in the *GhSAMS* promoter region (2000 bp upstream nucleotide sequence) was achieved by the online PlantCARE server software (Bristol, England) [30]. MEME server (https://meme-suite.org, version 5.4.1; accessed on 13 Jully 2020), with the default setting, was used to predict conserved motifs within the gene structures ().


**Acknowledgements**

The remarkable variability of Serro Azul and the interesting association with glossy seeds (SAB) with resistance to anthracnose and bruchids raises further research questions and opportunities for new crosses. As previously suggested, seed coat glossiness might after all have an important role in protecting seeds against biotic stresses, as SAB has shown. Conversely, we have not demonstrated that the disease resistance of SAB plants has association with glossiness, which needs more experiments. Either way, this is an important feature which might be explored in depth with the population derived from this landrace to appropriately answer this question. Landraces such as Serro Azul hold particularities that should not be disregarded, after all, local communities need those seeds for their supply, and they have traits of high interest to be explored by breeders, especially concerning the threat of anthracnose and insects

From this example to a wider set of landraces, several traits of interest might be improved with the use of distinct allele combinations if not new alleles provided by such genetic materials. Burle et al. [24] analyzed 279 landraces of common bean from Brazil and discovered considerable genetic diversity among all the accessions evaluated. Those genotypes are distributed from colder to warmer and from wetter to drier areas in the country. The local adaptation implicated in such genotypes has implicated in potential sources of disease and insect-resistant accessions. Moreover, the climatic diversity provides the potential for adapting to distinct abiotic stresses. New sources for tolerance to drought, soil salinity, high and low temperatures are to be investigated from these collections. In fact, Burle et al. [10] continued the previous work and integrated phenotypic evaluations to the genetic analysis of the same 279 landraces. The authors screened these accessions based on 22 morphological traits, including resistance to rust and common bacterial blight, yield, flowering time, determinacy and growth habit, seed coat color and brilliancy, among others. The study provided valorous information for supporting initiatives toward conservation and management of the accessions. It also allowed to detect the particularities of landraces and how they can be explored

In this chapter, we described the importance of the conservation and study of landraces of common bean. As an example, to go through the extent of morphological, biochemical and genetic aspects of landraces, we outlined the previous results as well as the new findings about the Brazilian landrace Serro Azul. This landrace has been produced by local farmers from Sao Paulo state and has remarkable features for exploring variation of seed and yield traits in common bean, constituting an additional and valuable genetic resource for germplasm collections. We also showed a genetic diversity analysis of Serro Azul by examining the molecular variability within subsamples of SAB and SAF, based on amplified fragment length polymorphic (AFLP) markers. Furthermore, a detached leaf assay for screening anthracnose resistance was employed for both variants within this landrace, revealing remarkable differences between the highly resistant Serro Azul Brilhante (glossy seed coat) and the susceptible Serro Azul Fosco (opaque seed coat). Together, these results demonstrated the importance of

in controlled crosses for designing new populations and cultivars.

to common bean cultivation.

190 Rediscovery of Landraces as a Resource for the Future

**7. Conclusions**

We thank Monica Rossi Lanzoni and Prof. Adriana Pinheiro Martinelli for their assistance in the microscopy analyses. We also thank the assistance and materials provided by the Agronomic Institute of Campinas for performing the analyses with the races of *C. lindemuthianum* and the valorous technical assistance of Ana Luiza Ahern Beraldo in the experiments. The results presented in this chapter received funding from the National Council for Scientific and Technological Development (CNPq).