Effect of location in a cylinder wake on dynamics of a flexible energy harvesting plate

© 2019 Penerbit Akademia Baru. Flexible plate in the wake of a bluff body may be exploited to harvest energy, for example by attaching piezoelectric sheets on both surfaces of the plate. A computational investigation on flow-induced vibration of a flexible plate in the wake of a cylinder is undertaken to understand the effects of plate location on their vibrations and hence, energy harvesting potential. Based on cylinder diameter D (0.1m), flow at a sub-critical Reynolds number of 10000 was considered in the present study. The fluid-structure interaction was implemented via a closely-coupled partitioned scheme that employs a Scale-Adaptive Simulation (SAS) of the Shear Stress Transport (SST) method to model flow turbulence. A flexible plate was placed at several locations (streamwise: x/D = 0.5, 1.0, 1.5, 2.0; crossflow: y/D = 0, 0.25, 0.5) downstream of the cylinder and their flow-induced response were compiled and analysed. Benchmarking of present model showed good agreement with previous experimental investigations. Results suggest that maximum deflection may be found if flexible plate is placed in the region between cylinder surface and x/D < 1.0. Oscillation of flexible plate placed at y/D = 0.25 shows similar amplitude, if not slightly higher, than if plate is placed at wake centerline. Present findings suggest that energy output may be optimised by positioning flexible energy harvesting plates at favourable locations in the wake region

A review on the applicability of remanufacturing in extending the life cycle of marine or offshore components and structures

One of the most significant and value-added End of Life (EoL) recovery strategies in the Circular Economy is remanufacturing in which the functionality and performance of products are retained. In the marine industry, the intensity of remanufacturing is low compared to other transportation industries such as aerospace, automotive and rail. This paper discusses current issues on Design for Remanufacturing (DfRem) in the marine industry and provides insights into how remanufacturing plays a significant role in enhancing reliability and safety during the extended life of marine products and structures. Today, with the large number of ships approaching EoL, remanufacturing should be the way forward due to its positive impact on the environment and socio-economy. While marine components such as engines, propeller shafts, compressors and pumps have been successfully remanufactured in many parts of the world, remanufacturing of large structures such as hull and vessels have not been reported thus far. As in all other industries, remanufacturing has to be initiated with a paradigm shift in the business models, designing parts and structures for efficient remanufacturing, and the establishment of relevant policies and standards in order to pave the way towards a more sustainable marine industry in the future

Bifurcation Simulation Modeling Review

This paper reviews the advances made on studies related to bifurcation. Bifurcation has been an area of interest by researchers in hydraulics, hydrology and river engineering disciplines. This paper reviews the findings of nearly 10 years of researches into modeling bifurcation system with numerous simulation techniques. Efforts have been made to simulate behavior of bifurcation through the uses of numerical and physical models. The numerical approach under the pretext of computational fluid dynamic is an approach that uses the fundamental theory of fluid mechanics and hydraulics that simulates flow behavior

Root canal instrumentation efficacy of non-fused and fused primary molar roots:a micro-computed tomography study

Purpose Pulpectomy may be indicated in restorable primary teeth exhibiting irreversible pulpitis or pulpal necrosis. The purpose of this study was to compare the cleaning and shaping efficacy of NiTi systems (Reciproc(R) Blue and MTwo(R)) with manual stainless-steel instrumentation in primary molars using micro-CT analysis. Methods Fifty-seven maxillary second primary molars were scanned using micro-CT. Teeth with three divergent roots were divided randomly (n = 15) according to instrument type (K file, MTwo (R), and Reciproc (R) Blue). Teeth with root fusion were instrumented manually as a separate group (n = 12). Pre- and post-instrumentation micro-CT images were superimposed, and the instrumentation area (IA) and procedural complications were recorded. Results No statistically significant differences in IA between file systems was observed in the non-fused teeth. The mean IA of fused roots was significantly lower than in the non-fused distobuccal (p = 0.003) and palatal (p 60%) occurred in both non-fused and fused primary teeth with fewer procedural complications observed after manual instrumentation

High temperature oxygen NEXAFS valence band spectra and conductivity of LaFe3/4Ni1/4O3 from 300 K to 773 K

LaFe3/4Ni1/4O3 was subjected to oxygen near edge x-ray absorption fine structure (NEXAFS) spectroscopy for 300 K < T < 773 K. The spectra show in the pre-edge a small hole doped peak originating from Ni substitution. The relative spectral weight of this transition to the weight of the hybridized O(2p) - Fe(3d) transitions scales with T and has a maximum at around 600 K. The characteristic energies of the thermal activated spectral intensity and conductivity suggest that the concentration of charge transferred electrons from O(2p) to Ni(3d) increases and that the pre-edges account in part for the polaron activated transport

The Effects of Air Flow in the Wake of a Large Vehicle on Trailing a Passenger Car

Road driving condition under drafting is known to have an influence on the aerodynamic forces of the vehicle. Large vehicles such as busses and trucks traveling at high speeds give results in the formation of a large turbulent flow in the wake region. This turbulent flow is very unsteady in nature hence its influence on the air flow within its vicinity will also be unsteady. This paper investigates the relative values of drag and lift forces acting on a passenger car trailing a large vehicle (drafting) under unsteady conditions. The simulation is conducted using Computational Fluid Dynamics software, FLUENT for a two-dimensional flow domain at Re 3.18x106 for a trailing distance of 0 to 30 meters. The unsteady effect is studied at 15 time intervals for each time step. Turbulence is simulated using the Reynolds-Average Navier Stokes (RANS) k-ε model. Results show that aerodynamically, the critical drafting distance is between three to five meters where the lowest drag is found to occur at three meters. The results show the suitable distance for drafting which may serve as useful information for vehicle fuel economy and stability

Improving total sediment load prediction using genetic programming technique (Case Study: Malaysia)

Predicted total sediment load is usually used to identify the intensity of a sedimentation process. Currently, the existing available models to predict total load are mostly developed based on data collected from flumes, channels and rivers located in western countries. These models known as sediment transport model may not be valid to predict total sediment load of rivers in the tropics due to significant differences in the hydrological and sediment characteristics conditions. A new technique called Genetic programming (GP) technique is used to develop a new model to improve the prediction of total sediment load for rivers in tropical Malaysia. The new model named Evolutionary Polynomial Regression (EPR) model is compared with other three available sediment transport models using the different techniques including, Regression Equation, Modified Graf and Multiple Regression. Statistical analyses based on 82 data sets show the sediment transport model using this new technique perform well compare to other models

Recombinant sclerostin antagonizes effects of ex vivo mechanical loading in trabecular bone and increases osteocyte lacunar size

Sclerostin has emerged as an important regulator of bone mass. We have shown that sclerostin can act by targeting late osteoblasts/osteocytes to inhibit bone mineralization and to upregulate osteocyte expression of catabolic factors, resulting in osteocytic osteolysis. Here we sought to examine the effect of exogenous sclerostin on osteocytes in trabecular bone mechanically loaded ex vivo. Bovine trabecular bone cores, with bone marrow removed, were inserted into individual chambers and subjected to daily episodes of dynamic loading. Cores were perfused with either osteogenic media alone or media containing human recombinant sclerostin (rhSCL) (50 ng/ml). Loaded control bone increased in apparent stiffness over time compared with unloaded bone, and this was abrogated in the presence of rhSCL. Loaded bone showed an increase in calcein uptake as a surrogate of mineral accretion, compared with unloaded bone, in which this was substantially inhibited by rhSCL treatment. Sclerostin treatment induced a significant increase in the ionized calcium concentration in the perfusate and the release of -CTX at several time points, an increased mean osteocyte lacunar size, indicative of osteocytic osteolysis, and the expression of catabolism-related genes. Human primary osteocyte-like cultures treated with rhSCL also released -CTX from their matrix. These results suggest that osteocytes contribute directly to bone mineral accretion, and to the mechanical properties of bone. Moreover, it appears that sclerostin, acting on osteocytes, can negate this effect by modulating the dimensions of the lacunocanalicular porosity and the composition of the periosteocyte matrix

CRIg-expressing peritoneal macrophages are associated with disease severity in patients with cirrhosis and ascites

Infections are an important cause of morbidity and mortality in patients with decompensated cirrhosis and ascites. Hypothesizing that innate immune dysfunction contributes to susceptibility to infection, we assessed ascitic fluid macrophage phenotype and function. The expression of complement receptor of the immunoglobulin superfamily (CRIg) and CCR2 defined two phenotypically and functionally distinct peritoneal macrophage subpopulations. The proportion of CRIg(hi) macrophages differed between patients and in the same patient over time, and a high proportion of CRIg(hi) macrophages was associated with reduced disease severity (model for end-stage liver disease) score. As compared with CRIg(lo) macrophages, CRIg(hi) macrophages were highly phagocytic and displayed enhanced antimicrobial effector activity. Transcriptional profiling by RNA sequencing and comparison with human macrophage and murine peritoneal macrophage expression signatures highlighted similarities among CRIg(hi) cells, human macrophages, and mouse F4/80(hi) resident peritoneal macrophages and among CRIg(lo) macrophages, human monocytes, and mouse F4/80lo monocyte-derived peritoneal macrophages. These data suggest that CRIg(hi) and CRIg(lo) macrophages may represent a tissue-resident population and a monocytederived population, respectively. In conclusion, ascites fluid macrophage subset distribution and phagocytic capacity is highly variable among patients with chronic liver disease. Regulating the numbers and/or functions of these macrophage populations could provide therapeutic opportunities in cirrhotic patients