Scientia Iranica
Volume:28 Issue: 1, Jan-Feb 2021

To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathe-matical model for calculations. The architecture of the water-air amphibious aerial vehicle is especially crucial to the whole product, which impacts its performances in many different sides. a new architecture of low-submerged ducted water-air amphibious aerial vehi-cle with double rotor wings is designed on the basis of the studies home and abroad. Both of the system architecture and the dynamic model are established and both of the water-flow and airflow are analyzed with Fluent based on the 3D structure models built by Solidworks software, which mainly aims at the impact factors of body thrust force and lift force. And the CFD simulations of the layout are also accomplished based on the former analysis results as well. Compared with the results from PSO algorithm, kriging model and orthogonal test, the most suitable shape architecture is optimized. Finally, the optimized results were simulated by Fluent. The results show that the Global optimization thought based on the Kriging model and the PSO algorithm significantly improve the lift and drive performance of cross-domain aircraft and computer operational efficiency.

The present study describes MHD micropolar fluid as a result of curved stretching surface with Cattaneo-Christov theory of heat diffusion. The new heat model with the relaxation time is employed in this paper, in spite of classical theory of heat flux presented by Fourier. The curvilinear coordinates are used to model the governing equations. The nonlinear PDE’s are changed into ODE’s by using suitable transformation. The nonlinear ODE’s are solved with the help of OHAM by using BVPh2. The variation of several parameters are indicated and examined graphically. We observed that the pressure and velocity rises by enhancing the radius of curvature.

The vibration of the delaminated composites concerns the structure safety and dynamic behavior of the composite structures as it can be vital in the presence of delamination. In this research paper, the finite element simulations, numerical simulations and the experimental work are combined to analyze the vibration behavior at different delamination size, different stacking sequences and different boundary conditions. The finite element analysis software packages like Ansy and Abqus are used to fetch the vibration response of carbon fiber reinforced polymer composite plate for different boundary conditions, stacking sequences and delamination sizes. Experiments are carried out to study the vibration behavior. Numerical results were obtained using the first order shear deformation theory. Rayleigh-Ritz method was used to derive the governing equations to find the natural frequencies and the results were computed using Matlab tool. The results from finite element, numerical and experimental analysis were then compared and verified that the maximum percentage of error is ignorable. It is seen that the natural frequencies of carbon fiber reinforced polymer decreased with an increase in delamination size subjected to all boundary conditions. The higher values of natural frequencies found for all sides clamped boundary conditions.

Unwanted vibrations of the vehicles are regarded as harmful threats to the human health from various biomechanical and psychophysical aspects. Road roughness has been considered as the main cause of unwanted vibrations in bus vehicles. Vertical seat vibrations have been found via simulation of a ten degree of freedom (10-DOF) model of an intercity bus vehicle under harmonic and random excitations caused by road roughness. To suppress undesirable vibrations, mass-spring-damper passive absorbers are proposed in a thirteen degrees of freedom (13-DOFs) model of the bus. By optimizing the characteristics of the embedded passive absorbers under each seat, and implementation of the designed absorbers, it is observed that the vertical displacement amplitudes in the frequency response of the seats are reduced especially near the bus resonance frequencies. In addition, the vertical displacement and acceleration amplitudes are decreased in the random excitation of the road roughness. According to the results, optimized mass-spring-damper absorbers are suggested as a practical solution to suppress the unwanted vibration effects in the bus vehicle.

Traumatic brain injury is caused by physical brain injury. A computational model for considering the response of a neuronal cell under blast loading is presented. The neuronal cell consists of four components including the nucleus, cytoplasm, membrane, and also the network of microtubules with different arrays including crossing, stellate as well as random orientations. The effect of the sub-cellular components, specifically the network of microtubules, on a Traumatic Brain Injury’s consequences was studied as a novel and state-of-the-art innovation. Nucleus, cytoplasm, and membrane are assumed viscoelastic, while the network of microtubules follows elastic behavior. Finite element methods and fluid-structure interactions are considered to solve the coupled equations of the solid and the fluid. The results show that the presence of a network of microtubules, regardless of the types of arrays, reduces the total displacement of the cell as well as the von Mises stress. The membrane von Mises stress decreases 50 percent from 30 to 15 Pascal in presence of the network of the microtubules. Results of this research could be used in different fields including treatment of some diseases and pathological conditions such as kidney stones, sports injuries, traumatic astronauts, and ultimately prevention and treatment of traumatic brain injuries.

Calibration of hot-wire and hot-film probes at low velocities is a difficult task because the dynamic pressure at these velocities is very low and may not be measured easily. To overcome this problem, substituent techniques have been presented in the literature that rely on other phenomena and utilize different hardware. This paper describes a simple and low-cost method which proposes to move the anemometer probe in quiescent air (here by means of a swinging arm) and track this motion with a camera. After processing of the images, velocity time history of the probe is found by numerical calculations. Calibration curve is then obtained without any predetermined relationship. Using a medium-speed video camera that is often found in laboratories would avoid the need to a position sensor and a complicated arm on which this sensor is mounted. This technique can be used not only for pendulums but also for other means of moving probes in quiescent medium.

In this research, a combined cascade organic Rankine cycle (CORC) and ejector refrigeration loops incorporated with the concentrating linear Fresnel solar collector (LFSC) is proposed as a pre-cooling section to reduce electricity work consumption in a mixed refrigerant (MR) hydrogen liquefaction process. The exergy, exergoeconomic and exergoenvironmental analyses of the system during a year and special days are conducted in detail. Moreover, the annual thermodynamic, economic and environmental impact (EI) performances of the proposed system are evaluated by varying the substantial design parameters. Parametric study indicates that increasing the back pressure of turbine in the low temperature (LT) loop improves all aforementioned performances of the system. Meanwhile, bi-objective optimization based on non-dominated sorting genetic algorithm (NSGA-II) and LINMAP, TOPSIS and Shannon entropy decision makers are used to ascertain the optimum COPEx and economic/EI factors of the system concerned. Referring to the results, COPEx is improved by 10% and the cost and EI per exergy unit of LH2 reduce to 0.0309 $/MJ and 1.361 Pts/MJ through TOPSIS method.

There are many pieces of research considering slip phenomenon in centrifugal compressors to drive equations for prediction of the slip factor. Inevitably, some simplifications have been imposed on the flow field characteristics and effects of many parameters have been neglected. In this research slip phenomenon is investigated experimentally and numerically in one centrifugal compressor with complex blade curves and splitter blades considering the main effective parameters. Three-dimensional simulation of the compressor viscus flow field with suitable turbulence method was performed using CFD methods. Experimental work was carried out at several rotational speeds and mass flow rates which enabled slip factor results of the compressor as well as, approving accuracy of the simulation results. Effect of main parameters such as rotational speed, mass flow rate, blade number, blade exit angle, diffuser design and tip clearance on slip phenomenon were studied. It was observed that slip factor increases, as rotational speed and flow rate increase. Also changing the blade number from 6 to 9 in constant rotational speed and mass flow rate, caused 27 percent increase in slip factor. For a detailed insight, a variation of performance parameters such as pressure ratio and isentropic efficiency with slip factor were investigated, as well.

In this study, at first, the dynamic progressive failure of Glass-Fiber-Reinforced aluminum laminates (GLARE) under low-energy impact with intra laminar damage models implementing strain-based damage evolution laws, Puck failure criteria using ABAQUS-VUMAT,were modeled. For interface delamination, bilinear cohesive model; and for aluminum layers the Johnson-Cook model was implemented;and the fatigue life of the fiber metal laminates of GLARE subjected to impact was obtained; and the numerical and experimental results of the model were compared with each other. With regard to the very good match betweenthe numerical and experimental results, the results of the finite element model were generalized and expanded, and with the use of the multilayer neural network, the numerical model was extracted and then, by applying the meta-innovative algorithm, the maximum fatigue life of GLARE was determined atthe highest level with very low-velocity impact,and the best configuration of three-layer GLARE was selected.The findings indicated that the best configuration of hybrid composite GLARE based on conventional commercial laminates that can tolerate low-velocity impacts with 18J impact energy and a 349MPa fatigue load with a frequency of 10Hz was [Al/0-90-90-0/Al/0-90-0/Al/0-90-90-0/Al] with 13016 cycle lifetime.

Flexibility and simple tooling make the incremental sheet forming (ISF) a great process to create complex shapes from mild steel sheets. It is a significant issue to reduce the surface roughness (SR) which is a weakness in the manufacturing the mild steel parts in ISF process. The purpose of this study is to investigate the effects of the ISF process parameters on the SR of the mild steel sheets. Feed rate, tool diameter, vertical step and spindle speed are chosen as four input variables in the experimental tests. Taguchi design of experiment (DOE) and the analysis of variance (ANVOA) are used to optimize the SR by investigating the parameters effects and their interactions. According to the obtained results, the vertical step reduction and increase in tool diameter, decrease the roughness on the surface of the mild steel sheets during the single-point incremental forming (SPIF). In addition, the tool speed in term of both rotation and feed have little effect on the surface roughness. The results of a validation test demonstrates that the Taguchi technique and the ANOVA can effectively optimize the level of each variable to ensure the best SR.

Loop heat pipes (LHPs) are high efficiency devices which can be used in solar systems. The main objectives of this research are to propose a novel solar combined cooling heating and power (SCCHP) system based on loop heat pipe (LHP) evaporator, and to present thermodynamic analyses to effectively improve the utilization of loop heat pipes for distributed renewable energy sources. Also a parametric analysis is carried out to investigate the effect of the key variable parameters on the system performance for three operation modes (solar mode, solar and storage mode and storage mode). The results showed that, for the solar and solar and storage operation modes, the main source of the exergy destruction is the solar loop heat pipe evaporator while for the storage operation mode, the main source of the exergy destruction is the hot storage tank. The energy efficiency of the proposed system is 70.52% for the solar mode, 72.09% for the solar and storage mode, and 64.77% for the storage mode and the exergy efficiency of the proposed system is 12.36% for the solar mode, 14.78% for the solar and storage mode, and 47.45% for the storage mode.

At high angles of attack, the dynamic stall phenomenon could be appearing owing to the vortex shedding particularly in an oscillating airfoil. The consequences of this event are a considerable decrease in the lift and an increase in the drag as well as the pitching moment coefficients. The flow was assumed to be unsteady and turbulent at a Mach number 0.2 and for Reynolds number 1million. This research was done for a range of angle of attack 15o±10o. In order to carry out the numerical analysis of the problem, the 2-D compressible turbulent Navier-Stokes equations based on “Roe” scheme with second-order accuracy were solved. Turbulence modeling was carried out using the three-equation k-kL-ω model. Regarding the obtained results, it was observed that this flow control method had a significant ability in eliminating the dynamic stall. It was also revealed that the phase difference between the jet and airfoil oscillations is more affected by the dynamic stall decrement. In these changes, use of the SJ with 0.1 momentum coefficient, led to the highest amplitude of lift at φ=-30°, and the multiplication of drag amplitude and amplitude of moment coefficient at φ=-10° offered the best performance in addition to the considerable decrease.

In this paper, a new in-pipe robot is designed and modeled, which is equipped by a manipulator in order to perform repairing tasks within the pipelines. Also, in order to provide a good manipulation process, impedance control is designed and implemented for the robot. Most of the in-pipe robots are limited to perform inspecting operations and are not capable of conducting manipulating tasks. In order to cover the mentioned deficiency, the robot is redesigned by adding a manipulator on the main body of the moving platform. Afterward, the model of the overall robot is extracted. Finally, impedance control is also designed and implemented for the robot so that not only the position of the end-effector can be controlled, but also the required force to cover the repairing task can be precisely provided. The correctness of modeling and efficiency of the proposed mobile in-pipe robot is verified by conducting some simulation scenarios in MATLAB. It will be seen that by the aid of the proposed mechanism and employing the designed force controlling strategy, the manipulation process of the robot in the pipes can be realized successfully.