Computational Fluid Dynamics Modelling of Two-Phase Bubble Columns: A Comprehensive Review

Bubble columns are used in many different industrial applications, and their design and characterisation have always been very complex. In recent years, the use of Computational Fluid Dynamics (CFD) has become very popular in the field of multiphase flows, with the final goal of developing a predictive tool that can track the complex dynamic phenomena occurring in these types of reactors. For this reason, we present a detailed literature review on the numerical simulation of two-phase bubble columns. First, after a brief introduction to bubble column technology and flow regimes, we discuss the state-of-the-art modelling approaches, presenting the models describing the momentum exchange between the phases (i.e., drag, lift, turbulent dispersion, wall lubrication, and virtual mass forces), Bubble-Induced Turbulence (BIT), and bubble coalescence and breakup, along with an overview of the Population Balance Model (PBM). Second, we present different numerical studies from the literature highlighting different model settings, performance levels, and limitations. In addition, we provide the errors between numerical predictions and experimental results concerning global (gas holdup) and local (void fraction and liquid velocity) flow properties. Finally, we outline the major issues to be solved in future studies

Computational fluid dynamics simulation of the heterogeneous regime in a large-scale bubble column

Bubble columns are used in many industrial applications, but the complex fluid dynamics phenomena has limited their design and optimization processes. Computational Fluid Dynamics (CFD) is a promising tool to investigate the complex multi-scale flow physics characterising multiphase reactors. In this work, a CFD Eulerian-Eulerian modelling approach is developed to describe the hydrodynamics of a large-scale bubble column operated over a wide range of superficial gas velocities (0.0188 – 0.20 m/s). Available experimental results were used for the model validation. A drag law for oblate bubbles was considered and coupled with a drag modification function to include the effects of bubble–bubble interactions. The numerical approach was tested considering a mono-dispersed approximation and including coalescence and breakup by using a Population Balance Model (PBM). The role played by the lift force was investigated and, for the reactor configuration considered, it turned out to be essential in the description of the local flow properties

Promotion of proliferation and metastasis of hepatocellular carcinoma by LncRNA00673 based on the targeted-regulation of notch signaling pathway

we read with great interest the paper by Dr. Chen et al1, recently published in European Review for Medical and Pharmacological Sciences and titled ‘‘Promotion of proliferation and metastasis of hepatocellular carcinoma by LncRNA00673 based on the targeted-regulation of notch signaling pathway’’. Authors concluded that lncRNA00673 is highly expressed and may be a potential target for the treatment of Hepatocellular Carcinoma (HCC). Moreover, according to authors, it can promote the proliferation and metastasis of HCC by the regulation of Notch signaling pathway. We congratulate the authors for their interesting work

Computational fluid dynamics modelling of the regular wave flow regime in air-water downwards annular flows

Although the global flow characteristics of annular gas-liquid flows have been studied experimentally for more than 50 years, the spatiotemporally-resolved details of these flows have remained relatively unexplored until recently, with data provided via advanced experimental methods based, e.g., on optical techniques. Similarly, the numerical modelling of annular flows is still an immature process. The present work aims to provide a computational fluid dynamics (CFD) model based on the volume of fluid (VOF) method for simulating annular gas-liquid flows, setting the stage for a deeper investigation of these flows at global and local scales. The work focuses on the most common downwards annular flow (DAF) flow pattern: the regular wave regime. 3-D and 2-D axisymmetric transient simulations have been performed using a commercial code (ANSYS Fluent 2021 R1). The code is validated through available experimental data regarding topological flow properties, mainly film thickness and wave statistics. The validation results suggest that 3-D simulations are needed to provide predictions that agree with the experimental data, highlighting strong 3-D features in the flow

Laparoscopic Excision of Endometriosis May Require Unilateral Parametrectomy

Nerve-sparing complete excision of endometriosis may not be possible. In these patients, unilateral parametrectomy may be a reasonable alternative management strategy

Capability of non liner eddy viscosity model in predicting complex flows

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.The research field of the study is related with turbulence modeling. The general objective is the implementation in a commercial code, of two equations Non Linear Eddy Viscosity Model (NLEVM) which removes Boussinesq linear approximation for the Reynolds stress tensor. The work described in the paper implements a second order k-ε model based over Shih, Zhu and Lumley (1993) [1] and Craft, Launder and Suga (1996) [2] in the finite volume commercial code ANSYS-FLUENT v. 6.3.26, by writing additional subroutines. The model has been validated through experimental and DNS data available in the literature. The benchmarks shown in this paper are the straight Square Duct [8] and the Backward-Facing Step [9, 10]. After the validation, the model has been used for predicting the flow behavior for complex industrial applications. The geometry used is similar to the bowl-shape downcomer of nuclear reactor. This is an application field of interest still under study by the same research group and an international consortium.vk201

Islands as Time Capsules for Genetic Diversity Conservation: The Case of the Giglio Island Mouflon

The use of multidisciplinary approaches of investigation including biological, biogeographical, historical, morphological, and genetic analysis, can be useful in identifying and preserving biodiversity. The present study focuses on the characterisation and conservation of a mouflon population (Ovis gmelini musimon) from the Mediterranean island of Giglio. Here we provide the first molecular data on the Giglio population and compare it with mouflons from Sardinia, Elba, and Corsica using both nuclear and mitochondrial markers. Our results suggest that the Giglio mouflon harbours genetic variability likely of Sardinian origin but not represented in the current Sardinian mouflon diversity. Although not presenting the typical characteristics of an invasive alien species, the Giglio mouflon is being subjected to eradication through culling or trapping and surgical sterilization. The molecular evidence we report highlights that such actions are causing the irremediable loss of ancestral genetic variants of the genus Ovis. Finally, we highlight how a multidisciplinary approach is necessary to aid the conservation and management of the anthropochorous populations of Mediterranean mammals

Cognitive Impairment and Age-Related Vision Disorders: Their Possible Relationship and the Evaluation of the Use of Aspirin and Statins in a 65 Years-and-Over Sardinian Population

Neurological disorders (Alzheimer’s disease, vascular and mixed dementia) and visual loss (cataract, age-related macular degeneration, glaucoma, and diabetic retinopathy) are among the most common conditions that afflict people of at least 65 years of age. An increasing body of evidence is emerging, which demonstrates that memory and vision impairment are closely, significantly, and positively linked and that statins and aspirin may lessen the risk of developing age-related visual and neurological problems. However, clinical studies have produced contradictory results. Thus, the intent of the present study was to reliably establish whether a relationship exist between various types of dementia and age-related vision disorders, and to establish whether statins and aspirin may or may not have beneficial effects on these two types of disorders. We found that participants with dementia and/or vision problems were more likely to be depressed and displayed worse functional ability in basic and instrumental activities of daily living than controls. Mini mental state examination scores were significantly lower in patients with vision disorders compared to subjects without vision disorders. A closer association with macular degeneration was found in subjects with Alzheimer’s disease than in subjects without dementia or with vascular dementia, mixed dementia, or other types of age-related vision disorders. When we considered the associations between different types of dementia and vision disorders and the use of statins and aspirin, we found a significant positive association between Alzheimer’s disease and statins on their own or in combination with aspirin, indicating that these two drugs do not appear to reduce the risk of Alzheimer’s disease or improve its clinical evolution and may, on the contrary, favor its development. No significant association in statin use alone, aspirin use alone, or the combination of these was found in subjects without vision disorders but with dementia, and, similarly, none in subjects with vision disorders but without dementia. Overall, these results confirm the general impression so far; namely, that macular degeneration may contribute to cognitive disorders (Alzheimer’s disease in particular). In addition, they also suggest that, while statin and aspirin use may undoubtedly have some protective effects, they do not appear to be magic pills against the development of cognitive impairment or vision disorders in the elderly

A Reappraisal of Lymphadenectomy in Common Gynecological Cancers

Objectives: Lymph node dissection (LND) in gynecological malignancies has always been a cornerstone in the diagnosis of metastasis, it is also considered an important prognostic factor, and a reliable guide to management strategies. However, its incidence of complications, namely lymphedema, vascular injuries and other lesions, has led to a reconsideration of its efficacy and a comparison of the role of systematic vs. sentinel lymph node (SLN) dissection. Mechanism: Review of the literature using keywords such as “lymph nodes”, “sentinel lymph nodes”, “morbidity and mortality”, “gynecological cancers”, “endometrial cancer”, “ovarian cancer”, and “cervical cancer”. Findings in Brief: In the case of endometrial cancer, several studies have investigated the efficacy of SLN compared with systematic LND. Most of the results demonstrated the efficacy of SLN dissection in endometrial cancer, with the added benefit of lower morbidity. In patients with ovarian cancer, the mainstay of treatment is debulking with optimal cytoreductive surgery. Recent studies have compared systematic lymphadenectomy to non-lymphadenectomy, with an additional advantage in the cases of lymphadenectomy. However, since its publication, the lymphadenectomy in ovarian cancers (LIONS) trial, has revolutionized the standard of care for patients with advanced ovarian cancer and has called into question the increased morbidity and mortality in systematic lymphadenectomy. In cervical cancers, lymph node status is considered to be the most important prognostic factor. In this case, limiting lymphadenectomy to the borders of the inferior mesenteric artery seems promising, and studies are currently being carried out to investigate the feasibility of SLN dissection instead of systematic lymph node dissection. Conclusions: SLN dissection is associated with lower morbidity and mortality, and has been shown to be superior to systematic lymphadenectomy in several studies. However, more research and specific guidelines are needed to better select either one or the other method in the management of gynecological cancers. Copyright: © 2023 The Author(s)