Experimental and numerical investigation of different geometrical parameters in a centrifugal blood pump

Purpose Due to the importance of public health and economics, cardiovascular disease has become one of the most important debates and challenges for scientists. However, few studies have been done to address this challenge. The main objective of this document is to provide an optimal model to improve the performance of the left ventricular assist device and reduce costs. In this way, in the present study, the experimental and numerical procedures were developed to analyze the effects of the geometrical features and operational parameters on the performance of a centrifugal blood pump (CBP). Methods In order to achieve this aim, first, experimental tests were carried out to study the influence of the working fluid temperature and the rotational speed on the CBP. Subsequently, the performance of the CBP was assessed using computational fluid dynamics (CFD), and comparison was made against the experimental data. In addition, the influence of mounting an inducer on the overall performance of CBP was also investigated. Results Good agreement between the CFD and the data was obtained. The CFD results showed that increasing the fluid temperature and rotational speed leads to an increase in the hydraulic efficiency, pressure difference, and power. In addition, the reduction of the pressure difference and hydraulic efficiency with increasing the surface roughness was observed. While mounting an inducer on the pump did not significantly impact its overall performance, the highest value of the wall shear stress dropped moderately on the impeller and, therefore, unveiled the possibility of improving the performance of such designs.

Optimization Design of Energy-Saving Mixed Flow Pump Based on MIGA-RBF Algorithm

Mixed flow pumps driven by hydraulic motors have been widely used in drainage in recent years, especially in emergency pump trucks. Limited by the power of the truck engine, its operating efficiency is one of the key factors affecting the rescue task. In this study, an automated optimization platform was developed to improve the operating efficiency of the mixed flow pump. A three-dimensional hydraulic design, meshing, and computational fluid dynamics (CFD) were executed repeatedly by the main program. The objective function is to maximize hydraulic efficiency under design conditions. Both meridional shape and blade profiles of the impeller and diffuser were optimized at the same time. Based on the CFD results obtained by Optimal Latin Hypercube (OLH) sampling, surrogate models of the head and hydraulic efficiency were built using the Radial Basis Function (RBF) neural network. Finally, the optimal solution was obtained by the Multi- Island Genetic Algorithm (MIGA). The local energy loss was further compared with the baseline scheme using the entropy generation method. Through the regression analysis, it was found that the blade angles have the most significant influence on pump efficiency. The CFD results show that the hydraulic efficiency under design conditions increased by 5.1%. After optimization, the incidence loss and flow separation inside the pump are obviously improved. Additionally, the overall turbulent eddy dissipation and entropy generation were significantly reduced. The experimental results validate that the maximum pump efficiency increased by 4.3%. The optimization platform proposed in this study will facilitate the development of intelligent optimization of pumps.

Factors Controlling the Hydraulic Efficiency of Green Roofs in the Metropolitan Area of Milan (Italy)

Green roofs (GRs) are considered sustainable solutions for the adaptation of urban water management to climate change. The use of GRs is particularly promising in urban environments like the Metropolitan Area of Milan, the most urbanized area in Italy. In this work, we evaluated the subsurface runoff coefficient at the event-time scale, for more than one year of observations, of 68 small-scale test beds comprising different configurations of green roofs (e.g., different vegetations, types and depths of growing media, and different slopes) installed in the Metropolitan Area of Milan. The objectives of this study are three-fold. Firstly, the controlling factors of the hydraulic have been assessed for efficiency. We calculated a mean drainage flow rate of 51%, finding that growing media play a significant role in determining the drainage flow during the spring, at the beginning of the vegetative period. During this season, water retention in fertilized beds increases significantly. At the beginning of the summer, the vegetation cover is able to significantly reduce the drainage flow, playing an even more crucial role with respect to the growing medium material. However, we found that the vegetation type (grass field and Sedum) does not play a significant role in the retention processes. Secondly, the delay of the peak flow rate was determined. We found a precipitation peak delay from 1 to 2 h, which would be sufficient to guarantee environmental benefits for urban drainage. Finally, the factors controlling the hydraulic efficiency of GRs for individual precipitation events were assessed. We found that soil moisture and cumulated precipitation are both significant factors determining the drainage flow rate. In conclusion, we point out that soil moisture is one of the main parameters characterizing GR drainage and should be further considered in future research efforts devoted to the analysis of GR performance.

Pit and tracheid anatomy explain the hydraulic safety- but not the hydraulic efficiency of 28 conifer species

Conifers face increased drought mortality risks because of drought-induced embolism in their vascular system. Variation in embolism resistance may result from species differences in pit structure and function, as pits control the air seeding between water transporting conduits. This study quantifies variation in embolism resistance and hydraulic conductivity for 28 conifer species grown in a 50-year-old common garden experiment and assesses the underlying mechanisms. Conifer species with a small pit aperture, high pit aperture resistance and large valve effect were more resistant to embolism, as they all may reduce air seeding. Surprisingly, hydraulic conductivity was only negatively correlated with tracheid cell wall thickness. Embolism resistance and its underlying pit traits related to pit size and sealing were stronger phylogenetically controlled than hydraulic conductivity and anatomical tracheid traits. Conifers differed in hydraulic safety and hydraulic efficiency, but there was no trade-off between safety and efficiency because they are driven by different xylem anatomical traits that are under different phylogenetic control.

Hydraulic Efficiency of Green-Blue Flood Control Scenarios for Vegetated Rivers: 1D and 2D Unsteady Simulations

Flood hazard mitigation in urban areas crossed by vegetated flows can be achieved through two distinct approaches, based on structural and eco-friendly solutions, referred to as grey and green–blue engineering scenarios, respectively; this one is often based on best management practices (BMP) and low-impact developments (LID). In this study, the hydraulic efficiency of two green–blue scenarios in reducing flood hazards of an urban area crossed by a vegetated river located in Central Tuscany (Italy), named Morra Creek, were evaluated for a return period of 200 years, by analyzing the flooding outcomes of 1D and 2D unsteady hydraulic simulations. In the first scenario, the impact of a diffuse effect of flood peak reduction along Morra Creek was assessed by considering an overall real-scale growth of common reed beds. In the second scenario, riverine vegetation along Morra Creek was preserved, while flood hazard was mitigated using a single vegetated flood control area. This study demonstrates well the benefits of employing green–blue solutions for reducing flood hazards in vegetated rivers intersecting agro-forestry and urban areas while preserving their riverine ecosystems. It emerged that the first scenario is a valuable alternative to the more impacting second scenario, given the presence of flood control areas.

Recent Studies on the Properties of Pervious Concrete; A Sustainable Solution for Pavements and Water Treatment

Pervious concrete a sustainable solution with limited fines or no fines and interconnected voids, has many environmental benefits, such as reducing the stormwater run-off, improving the groundwater table, reducing water pollution, and mitigating urban heat island. Many research works have been done in Pervious Concrete (PC) by varying different parameters such as, types of aggregate, aggregate gradation, water-to-cement (w/c) ratio, cement-to-aggregate ratio, geopolymer binder, ultra-high strength Matrix and compaction techniques. All these parameters have direct influences on the strength, porosity, permeability, hydraulic efficiency and durability characteristics of PC. The main aim of this paper is to review the recent work carried out in pervious concrete under six different categories (i) Effect of binders, coarse aggregate, admixtures and fibers used in PC (ii) Mechanical and durability properties (iii) pore structure characteristics (iv) Study on Clogging Effect (v) Role of PC in the water purification process and (vi) Numerical model in PC.