Scientia Iranica
Volume:30 Issue: 2, Mar -Apr 2023

The aim is to characterize the role of symmetry pattern on the flow control induced by dielectric barrier discharge plasma actuators. Two DBD actuators are employed for in-phase excitation with duty cycle 50% leading to symmetric wake pattern and out-phase excitation for two pulsing frequencies St=0.2 and St=1 at Re=1000 which forms quasi-symmetric and asymmetric flow structures respectively. The modes deduced from POD and DMD methods represent the competition between symmetric (S) and asymmetric mode (K) in all cases. The harmonic in-phase plasma actuation with 50% duty cycle is the most effective flow control method with lowest power consumption. The harmonic out-phase excitation is not much effective; however adjustment of the actuator position can form the symmetric pattern with minimum power consumption. The superharmonic out-phase plasma actuation reduces the wake region however is not effective in lift reduction significantly and consumes high amount of energy. This indicates that phase difference and plasma location influence on the size and symmetry of the vortical structure. Then, based on the symmetry properties of the designed wake pattern created by frequency and phase difference of the plasma actuator, the effective active flow control can be performed. The numerical results are validated with experiments.

Microfluidic technology and Micro Electromechanical Systems (MEMS) have received much attention in science and engineering fields over the last few years. MEMS can be found in many areas like heat exchangers, chemical separation devices, bio-chemical analysis and micro pumps. Keeping these facts in mind, the prime purpose of the current paper is to present the flow of Carreau nanofluids through the micro-channel with the electro-osmosis, Joule heating and chemical reactions. The effect of external magnetic field is also considered into account. For the formulation of the problem, the Cartesian coordinate system is considered. The perturbed solutions have been presented by making use of regular perturbation method. The graphical results also prepared corresponding to numerous values of fluid flow phenomenon like velocity, temperature, solutal nano-particle concentration, Sherwood number and Nusselt number with different fluid variables. It is concluded from our analysis that; velocity decrement is identified with respect to the enhancing the magnetic parameter (Hartmann number). The Schmidt number, Radiation term, Prandtl number and chemical reaction term increase the solutal nano-particle concentration. The outcomes of the Newtonian liquid model can be obtained from our scrutiny. The present scrutiny has many applications in engineering sciences such as electromagnetic micro pumps and nano-mechanics.

Apart from the widely used polymeric fibers, Quartz fiber is the one which possess various characteristics. Quartz polymeric fiber in combination with Cyanate Ester resin produces high-performance composite which has excellent properties and used primarily in military applications. The present investigation aims at developing a model to predict the output characteristics of hole in the drilling of Quartz composite laminate. Output parameters considered are thrust force, torque, exit delamination factor, hole diameter, cylindricity and surface roughness. Vacuum Assisted Resin Transfer Moulding (VARTM) process was adopted for the manufacturing of the laminate. Full factorial design of experiments was considered for the selected input parameters and experiments were carried out. Further model was developed to predict the output parameters employing Back Propagation Neural Network (BPNN) method and found that the optimal network architecture is 3-45-15-10-6 with Mean Squared Error (MSE) of 0.0105 . Experimental results were analyzed and studied the influence of input parameters in this drilling process. The testing data show a good match with the output parameters predicted from the model and maximum error obtained is 7.58%. Further, the model developed was validated with new batch of experiments and the values obtained are satisfactory with maximum error of 7.17%.

In the present research, energy in the geothermal fluid is utilized to generate power. In the first case of power generation, the model of the geothermal double-effect instantaneous evaporation cycle is employed, and in the second one, the single-effect evaporation combined cycle and Rankine cycle with different organic fluids are utilized. The effect of several organic fluids in the combined cycle is examined. The SPECO method has also been applied in economic analysis. Given the analysis, net power generation is the highest for the combined cycle with water vapor and the lowest for the double-effect instantaneous evaporation cycle with a considerable difference. Increasing the separator pressure at constant evaporator temperature reduce the power generation cost for combined cycles. The lowest power generation cost is related to the combined cycle with operating fluid R113, and the highest amount of power generation cost is related to the combined cycle with ammonia fluid. The Exergoeconomic coefficient, which indicates the ratio of the purchase price components to the sum of costs associated with total exergy destruction and the cost associated with purchasing cycle components, is also the highest for the combined cycle with R113 and the lowest for the double-effect instantaneous evaporation cycle.

The present paper investigated the effect of train speed and ground clearance on aerodynamic forces on a simplified high-speed train. For this purpose, 20 different cases, including trains with five different speeds and four varied ground clearances were numerically simulated. The results showed that increasing the train speed has a dual effect on increasing the vertical upward lift forces. Non-dimensional ground clearances above than 0.22 at speeds above 250 km/h, results in the upward lift forces dramatically and leaded to instability of the train. At ground clearances below than 0.092, increasing the speed increased the downward force, enhancing the stability of the train. Moreover, further analyzing the ground clearance effect demonstrated that in ground clearance value of about 0.048 lift force has an approximately constant value at different train speeds. The air velocity profiles under the train revealed a dimensionless rise with increasing ground clearance except at the front of the train. This increase was precisely apparent at speeds of 350 km / h and resulted in a 29% increase in some sections below the train. This rise in speed can disrupt the balance of passengers and pedestrians, and workers around the train.

This paper deals with the design of a deformable nose for the non-penetrating projectile in order to prevent its body deformation. Numerical, analytical and experimental studies have been carried out to analyze the effect of different nose shapes on the projectile deformation when it hits the brick wall. The projectile consists of an aluminum nose, a thin-walled steel cylinder body, and an end connector. This non-penetrating projectile can be used to carry a cargo that must reach its destination safely, for example in firefighting applications. To pursue this goal, the criterion utilized for the best design in this paper is stress and strain analysis. The geometric shape of the noses includes three types: type (a), type (b), and type (c). The first type of nose was flat shape. This nose was detached from the projectile by impact and did not prevent the projectile deformation. The second type of nose was a combination of flat and conical shapes. The projectile was also deformed by this nose. The third type of nose was a combination of flat, conical, and spherical shapes. Due to the maximum absorption of the impact energy, this type of nose prevented the deformation of the cargo and projectile.

An efficient numerical method is offered to discuss the effects of variable heatflux, viscous dissipation, and the slip velocity on the viscous Casson heat transfer(CHT) because the unsteady stretching sheet taken into reckoning the effect ofheat generation or absorption. The finite element method (FEM) is applied tosolve the resulting the ODEs which describe the problem. The effect of the factorsgoverning the HT such as unsteadiness parameter, slip velocity parameter, Cassonparameter, local Eckert number, heat generation parameter and the Prandtl numberare explored and given. Also, the local skin-friction coefficient and the local Nusseltnumber at the stretching sheet are computed and discussed. Finally, the obtainedsolutions confirm that the given procedure is an easy and efficient tool for assayingthe solution of such fluid models.