Temperature-dependent variable viscosity and thermal conductivity effects on non-Newtonian fluids flow in a porous medium

Purpose The purpose of this paper is to consider the simultaneous flow of Casson Williamson non Newtonian fluids in a vertical porous medium under the influence of variable thermos-physical parameters. Design/methodology/approach The model equations are a set of partial differential equations (PDEs). These PDEs were transformed into a non-dimensionless form using suitable non-dimensional quantities. The transformed equations were solved numerically using an iterative method called spectral relaxation techniques. The spectral relaxation technique is an iterative method that uses the Gauss-Seidel approach in discretizing and linearizing the set of equations. Findings It was found out in the study that a considerable number of variable viscosity parameter leads to decrease in the velocity and temperature profiles. Increase in the variable thermal conductivity parameter degenerates the velocity as well as temperature profiles. Hence, the variable thermo-physical parameters greatly influence the non-Newtonian fluids flow. Originality/value This study considered the simultaneous flow of Casson-Williamson non-Newtonian fluids by considering the fluid thermal properties to vary within the fluid layers. To the best of the author’s knowledge, such study has not been considered in literature.

Parametric optimization of friction stir welding process parameters of dissimilar welded joints using grey relational analysis and desirability function approach

Purpose The main purpose of the present work is to study the multi response optimization of dissimilar friction stir welding (FSW) process parameters using Taguchi-based grey relational analysis and desirability function approach (DFA). Design/methodology/approach The welded sheets were fabricated as per Taguchi orthogonal array design. The effects of tool rotational speed, transverse speed and tool tilt angle process parameters on ultimate tensile strength and hardness were analyzed using grey relational analysis, and DFA and optimum parameters combination was determined. Findings The tensile strength and hardness values were evaluated from the welded joints. The optimum values of process parameters were estimated through grey relational analysis and DFA methods. Similar kind of optimum levels of process parameters were obtained through two optimization approaches as tool rotational speed of 1150 rpm, transverse speed of 24 mm/min and tool tilt angle of 2° are the best process parameters combination for maximizing both the tensile strength and hardness. Through these studies, it was confirmed that grey relational analysis and DFA methods can be used to find the multi response optimum values of FSW process parameters. Research limitations/implications In the present study, the FSW is performed with L9 orthogonal array design with three process parameters such as tool rotational speed, transverse speed and tilt angle and three levels. Practical implications Aluminium alloys are widely using in automotive and aerospace industries due to holding a high strength to weight property. Originality/value Very limited work had been carried out on multi objective optimization techniques such as grey relational analysis and DFA on friction stir welded joints made with dissimilar aluminium alloys sheets.

Effect of fragment impact on shaped charge jet formation and penetration into steel target

Purpose This paper aims to investigate the effects of fragment impacts to shaped charge warheads in terms of shaped charge jet formation geometries and penetration performances. Design/methodology/approach In experimental process, a fragment was accelerated to a shaped charge warhead by means of a powder gun to a velocity more than 1,000 m/s, and this impact led to conical damage in the explosive of the warhead. Deformation on the warhead was visualized using X-ray technique to observe holes generated during fragment impact. Penetration test was performed against AISI 1040 steel plates with the damaged shaped charge warhead. Penetration performance of shaped charge jet, which deviated from the symmetry axis, was simulated by using SPEED software with 3-D Eulerian method to validate the numerical modelling method by comparing penetration test and simulation results of damaged warhead. Findings Simulation and test results showed good correlation for the warhead in terms of penetration depth and hole geometry at the impact surface of steel plates. In addition, the effects of the numbers and the geometries of fragment holes on shaped charge jet penetration performances were investigated with validated numerical methods. Simulation results showed that the increase in the number of fragment holes in the explosive of the warhead led to particulation of shaped charge jet that diminished penetration depth in the target plate. Additionally, simulation results also showed that the fragment hole geometry in the explosive after different fragment impact angles affected the amount of jet deviation from the symmetry axis as well as penetration depth in the target plate. Practical implications The results obtained from the current study revealed that fragment impact angle and different number of fragment impact reduced the penetration performance of shaped charge warhead by influencing the symmetry of shaped charge jet negatively. Originality/value The current study fulfils the need to investigate how fragment impact on the shaped charge warhead affect the formation symmetry of shaped charge jet as well as penetration performance by experimental and numerical methods. Penetration performance result of asymmetric jet is compared by experimental and numerical studies. A detailed methodology on numerically modelling of the effect of fragment impact angle and number of fragment impact on shaped charge jet performance is given in this study.

Flood hazard mapping and analysis under climate change using hydro-dynamic model and RCPs emission scenario in Woybo River catchment of Ethiopia

Purpose The purpose of this paper is to prepare flood hazard map and show the extent of flood hazard under climate change scenarios in Woybo River catchment. The hydraulic model, Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to simulate the floods under future climate scenarios. The impact of climate changes on severity of flooding was evaluated for the mid-term (2041–2070) and long-term (2071–2100) with relative to a baseline period (1971–2000). Design/methodology/approach Future climate scenarios were constructed from the bias corrected outputs of five regional climate models and the inflow hydrographs for 10, 25, 50 and 100 years design floods were derived from the flow which generated from HEC-hydrological modeling system; that was an input for the HEC-RAS model to generate the flood hazard maps in the catchment. Findings The results of this research show that 25.68% of the study area can be classified as very high hazard class while 28.56% of the area is under high hazard. It was also found that 20.20% is under moderate hazard and about 25.56% is under low hazard class in future under high emission scenario. The projected area to be flooded in far future relative to the baseline period is 66.3 ha of land which accounts for 62.82% from the total area. This study suggested that agricultural/crop land located at the right side of the Woybo River near the flood plain would be affected more with the 25, 50 and 100 years design floods. Originality/value Multiple climate models were assessed properly and the ensemble mean was used to prepare flood hazard map using HEC-RAS modeling.

Numerical analysis of safety distances of reinforced concrete structures subjected to blast loading by Perform-3D

Purpose The purpose of this study is to develop the performance model of buildings designed by the seismic code 2800 against the explosion wave and determination of safety distance. Design/methodology/approach Analytical models of three-, five- and ten story structures that used moment frame system and also a ten-storey building with shaer wall designed based on the seismic code 2800 in term of design and nonlinear analysis were generated for use with Perform-3D software. Extensive parametric analysis is executed on different explosive loads with 100, 500, 1,000 and 5,000 Trinitrotoluene, soil types 2 and 3, models eqs and eqbs, the number of story buildings and the effect of shear wall to determine the safety distance based on collapse threshold performance (CP) level criterion. Findings The results indicate that by increasing the explosives mass from 100 to 5,000 kg and the number of the stories three and five induce increasing the safety distance of CP level in buildings to 4.5 meter and 3 meter times, respectively. Ten-story structures modeled on shear wall show very good performance because of stiffness rising and high energy absorption. In addition, by increasing the stories from five to ten, the amount of the safety distance reduces the CP level to 3.9 meter times. Originality/value The results of this work are meaningful for explosion-resistant design and damage assessments of reinforced concrete moment framed structures subjected to explosive explosion.

Assessment of non-linear behavior and ductility of reinforced concrete structures

Purpose The calculation and design of the structures are carried out with the aim of obtaining a sufficiently ductile behavior to allow the structure to undergo displacements, without risk of sudden breaks or loss of stability. The purpose of this study is to develop and validate a computer program (Thin beam2), allowing the modeling and simulation of the nonlinear behavior of reinforced concrete elements, on the other part, it is estimating the local and global ductility of the sections or elements constituting these structures. Design/methodology/approach The authors present two nonlinear analysis methods to carry out a parametric study of the factors influencing the local and global ductility of reinforced concrete structures. The first consists in evaluating the nonlinear behavior at the level of the cross-section of the reinforced concrete elements used in the elaborate Sectenol 1 program, it allows us to have the local ductility. The second, allows us to evaluate the nonlinear behavior of the element used in the modified thin beam 2 program, it allows us to estimate the overall ductility of the element. Findings The validation results of the Thin beam2 program are very satisfactory, by conferring the analytic and experimental results obtained by various researchers and the parametric study shows that each factor such as the compressive strength of the concrete has a favorable effect on ductility. Conversely, the normal compression force and the high resistance of tensioned reinforcements adversely affect ductility. Originality/value The reliability of the two programs lies in obtaining the local and global ductility of reinforced concrete structures because the calculation and design of the structures are carried out with the aim of obtaining ductile behavior without risk of breakage and instability.

CloudJS: novel cloud-based design framework for text-file encryption

Purpose Cloud computing is becoming increasingly popular as it facilitates convenient, ubiquitous, on-demand network access to a shared pool of configurable computing resources and applications that can be quickly retrieved and released. Despite its numerous merits, it faces setbacks in data security and privacy. Data encryption is one of the most popular solutions for data security in the cloud. Various encryption algorithms have been implemented to address security concerns. These algorithms have been reviewed along with the Jumbling Salting algorithm and its applications. The framework for using Jumbling Salting to encrypt text files in the cloud environment (CloudJS) has been thoroughly studied and improvised. The purpose of this paper is to implement the CloudJS algorithm, to discuss its performance and compare the obtained results with existing cloud encryption schemes. Design/methodology/approach The paper uses six research questions to analyze the performance of CloudJS algorithm in the cloud environment. The research questions are about measuring encryption time and throughput, decryption time and throughput, the ratio of cipher to the plain text of CloudJS algorithm with respect to other Cloud algorithms like AES and DES. For this purpose, the algorithm has been implemented using dockers-containers in the Linux environment. Findings It was found that CloudJS performs well in terms of encryption time, decryption time and throughput. It is marginally better than AES and undoubtedly better than DES in these parameters. The performance of the algorithm is not affected by a number of CPU cores, RAM size and Line size of text files. It performs decently well in all scenarios and all resultant values fall in the desired range. Research limitations/implications CloudJS can be tested with cloud simulation platforms (CloudSim) and cloud service providers (AWS, Google Cloud). It can also be tested with other file types. In the future, CloudJS algorithm can also be implemented in images and other files. Originality/value To the best of the knowledge, this is the first attempt to implement and analysis of a custom encryption algorithm (CloudJS) in the cloud environment using dockers-containers.

Significance of fabrication parameters over the mechanical and metallurgical properties of AMMC joint formed by microwave hybrid heating

Purpose The purpose of the study is to fabricate a joint between two aluminium metal matrix composites using microwave hybrid heating (MHH). Design/methodology/approach Taguchi design of experiments was applied to conduct the experimental study. The mechanical properties such as ultimate tensile strength, micro-hardness and porosity were studied. Grey Relational Analysis was applied to understand the significance of fabrication parameters of best performing sample. The dominant factor of fabrication was analysed using ANOVA. The best performance sample was further characterised using X-ray diffraction and field emission scanning electron microscopy. Energy dispersive X-ray was used to analyse the elemental composition of the sample. Findings The Aluminium Metal Matrix Composite (AMMC) joint was successfully fabricated using MHH. The mechanical properties were mainly influenced by the fabrication factor of exposure time. Originality/value The formation of AMMC joint using MHH might explore the way for the industries in the field of joining.

Application of topology optimization method for the gothic greenhouse design

Purpose This research presents a design method for designing greenhouse structures based on topology optimization. Moreover, the structural design of a gothic greenhouse is proposed in which its structural strength has been improved by using this proposed method. In this method, the design of the structure is done mathematically; therefore, in the design process, more attention can be focused on the constraint space and boundary conditions. It was also shown how the static reliability and fatigue coefficients will change as a result of the design of the greenhouse structure with this method. Another purpose of this study is to find the weakest part of the greenhouse structure against lateral winds and other general loads on the greenhouse structure. Design/methodology/approach In the proposed method, the outer surface and the allowable volume as a constraint domain were considered. The desired loads can be located on the constraint domain. The topology optimization was used to minimize the mass and structural compliance as the objective function. The obtained volume was modified for simplifying the construction. The changes in the shape of the greenhouse structure were investigated by choosing three different penalty numbers for the topology optimization algorithm. The final design of the proposed structure was performed based on the total simultaneous critical loads on the structure. The results of the proposed method were compared in the order of different volume fractions. This showed that the volume fraction approach can significantly reduce the weight of the structure while maintaining its strength and stability. Findings Topology optimization results showed different strut and chords composition because of the changes in maximum mass limit and volume fraction. The results showed that the fatigue was more hazardous, and it decreased the strength of structure nearly three times more than a static analysis. Further, it was noticed that how the penalty numbers can affect topology optimization results. An optimal design based on topology optimization results was presented to improve the proposed greenhouse design against destruction and demolition. Furthermore, this study shows the most sensitive part of the greenhouse against the standard loads of wind, snow, and crop. Originality/value The obtained designs were compared with a conventional arch greenhouse, and then the structural performances were shown based on standard loads. The results showed that in designing the proposed structure, the optimized changes increased the structure strength against the standard loads compared to a simple arch greenhouse. Moreover, the stress safety factor and fatigue safety factor because of different designs of this structure were also compared with each other.

Investigation of vibratory bed effect on abrasive drag finishing: a DEM study

Purpose The purpose of this paper is to investigate the effect of a vibratory bed, as an assistant agent, on the improvement of the drag finishing process. The dynamics and kinematic of the process were surveyed in microscale for different frequencies and amplitudes and the results were compared to the basic process. Design/methodology/approach The discrete element tool was used to find out the effect of the vibratory bed on the drag finishing process. To this end, the Hertz-Mindlin model was used to investigate the contact of abrasive particles and workpiece. At the first stage, the numerical model was validated with the experimental results, and then the effect of different parameters on the finishing process was evaluated and compared with the basic case. Findings The chosen numerical model was in good agreement with the results measured in the previous literature. Moreover, the results show that not only vibrated bed enhances the contacts of abrasive particles to the workpiece, but it also increases the uniformity of the finished surface. Originality/value In comparison to the experiments, the discrete element technique consumes lower cost and time to estimate the optimum conditions of the finishing process, as well as it provides a good understanding of this phenomenon on the micro-scale.