On the role of surface permeability for the control of flow around a circular cylinder

The circular cylinder with porous materials coating (PMC) is studied in detail to reveal the sensitivity of surface permeability to the flow control and noise reduction. Two-dimensional simulations were firstly used to identify the critical values of permeability and thickness. Parametric study results show that, there is a critical permeability value which produces the minimum force fluctuation and maximum noise reduction. Additionally, the porous coating can work more efficient for noise reduction with larger thickness. The further three-dimensional simulation is employed to understand the underlying physical mechanisms of flow control. The results show that the spanwise vorticity is modified more than that of other directions and behaves more synergistically. The pressure field adjacent to the cylinder surface indicates that the adverse pressure gradient is changed to the favorable pressure gradient around the porous surface which contributes partly to the vortex shedding suppression

Numerical simulation study on suppression effect of water mist on PMMA combustion under external radiant heat flux

Numerical model was built with fire dynamic simulator and theocratical simulation was carried out to investigate the suppression effect of water mist on ignition and combustion process of typical solid material polymethyl methacrylate under external radiant heat flux. Characteristic parameters such as ignition time, surface temperature, heat release rate and temperature distribution of flame central plane during ignition and combustion process under different thermal radiant fluxes were obtained and compared with experimental results. The suppression effect of spray droplets on ignition and combustion process was analyzed and discussed. The results show the theoretical calculations of combustion characteristic parameters are in good agreement with experimental measurements. Water mist droplets can effectively delay the ignition time. Quantitative data proves that the water mist flow rate at 0.9 L/(min·m2) can delay the ignition time of samples by about 1,100 s while the radiant heat flux is 50 kW/m2. The simulation results can provide theoretical support and data reference for typical solid material fire prevention and fire extinguishment in practice

Current Advances in the Biosynthesis, Metabolism, and Transcriptional Regulation of α-Tomatine in Tomato

Steroid glycoalkaloids (SGAs) are a class of cholesterol-derived metabolites commonly found in the Solanaceae plants. α-Tomatine, a well-known bitter-tasting compound, is the major SGA in tomato, accumulating extensively in all plant tissues, particularly in the leaves and immature green fruits. α-Tomatine exhibits diverse biological activities that contribute to plant defense against pathogens and herbivores, as well as conferring certain medicinal benefits for human health. This review summarizes the current knowledge on α-tomatine, including its molecular chemical structure, physical and chemical properties, biosynthetic and metabolic pathways, and transcriptional regulatory mechanisms. Moreover, potential future research directions and applications of α-tomatine are also discussed