Yanbu Journal of Engineering and Science (YJES)
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NUMERICAL EXPERIMENTS ON SHOCK WAVE DIFFRACTION AROUND RAMP SPLITTER USING SMALL AND LARGE SHOCK TUBES
No full textThe experimental studies on shock wave diffraction have been done on conventional small-scale experimental shock tube which reveals spatial and temporal limitations. The wave reflected from the walls of the test section interferes with the evolution of the shear layer and its associated vortex. The computational fluid dynamics can simulate flow patterns of large-scale shock tube that are difficult, expensive, or impossible to study using measurements. The present numerical research is dedicated for diffraction of unsteady compressible flow around 172 ramp splitter using small and four-time larger shock tubes. Both scales are realistic sizes that are likely to be found in the real life applications. Therefore, the objectives of the research are to achieve a better understanding of spiral vortex evaluation, shock-vortex interaction and the associated Kelvin-Helmholtz instability that are not covered by experiment shadowgraphs. The present numerical method is a cell centered finite volume. The second-order AUSM+ scheme is applied to calculate the inviscid fluxes of the unsteady Euler equations. The simulations are performed using quadrilateral mesh. Mesh adaption of five additional levels each refined by a factor of four is applied in regions where density gradients exceed 5% of the local normalized value. Results are presented for weak and strong shock waves of the Mach numbers 1.31 and 1.59. The numerical results reveal excellent agreement with the corresponding experimental shadowgraphs. It is found that the refracted shock moving inside the vortex is affected by the rotation and centrifugal forces which have not been noted before
Real-Time Three-Phase Dynamic Full ACPF Distribution System Model
No full textPower flow is the backbone for power system operation and control. Power system balancing, where supply of energy has to equal demand all time, is a very important operation constraint for electric power systems. In recent years, penetration of Distributed Energy Resources (DERs) especially Renewable Energy Sources (RESs) into the distribution system has increased. RESs are known by their intermittent behavior in nature. Hence, as the number of these RESs increases, the sudden frequent change in power flow increases. Therefore, new obstacles to the operation and control of power systems arise. Power distribution system is also sparse and large system. Moreover, most traditional power flow solutions are based on iterative techniques which obviously take time. Therefore, computation time is a real problem when finding power flow solutions at distribution system especially with the unpredictability of RESs. To overcome these problems, a real-time linearized three-phase AC Power Flow (ACPF) model at distribution system is proposed. In this paper the linearized ACPF at distribution system is molded as follows. First Quasi linearized ACPF equations are developed for short period of time based on Newton’s Raphson (NR) method. Second sparse reordering algorithm techniques are used to reorder the node numbering of the power distribution system to reduce computational time. Then, simulation on IEEE 4 bus power system and IEEE 37 bus power distribution system are presented to validate the proposed model. Furthermore, Monte Carlo simulation is used to test the robustness of the proposed model
Investigation of the Molecular Structures, Electronic Properties and Vibrational Spectrum of Trifluoroacetophenone Using Density Functional Theory
No full textTrifluroacetophenone is considered a highly efficient, inexpensive, and green organocatalyst that is used in organic synthesis. Geometry optimization, electronic properties, and frequency calculations of 2,2,2-trifluoroacetophenone are performed using the B3LYP density functional theory method and the 6-311++G(d, p) basis set. The geometrical parameters, frontier molecular orbitals, molecular electrostatic potential surface, and simulated infrared spectrum are reported. The structural parameters are compared with available X-ray diffraction experimental values, and the calculated electronic properties are compared with those of its structural analogue, acetophenone
OPTIMIZATION OF PROCESSING PARAMETERS FOR A POLYMER BLEND USING TAGUCHI METHOD
No full textBlending of thermoplastic polyurethane (TPU) with poly dimethyl siloxane rubber (PDMS) is an attractive approach, where one can combine the strength, toughness and biocompatibility of TPU with flexibility, inertness, high temperature resistance, low temperature flexibility and biocompatibility of PDMS. But the control of
the factors determining the overall properties of such a blend like mixing time, temperature and rotor speed is difficult. Hence, an attempt has been made to optimize these processing parameters using statistical technique as per Taguchi. Four factors and
three levels were chosen for carrying out the analysis using L9 Orthogonal Array as per Taguchi methodology. Tensile strength and impact strength of the blends under different processing conditions were evaluated as the quality characteristics. Analysis of Variance (ANOVA) was used in determining the significance of factors. The levels of significant factors were optimized using Signal to Noise ratio. It was found that a balance between the two properties were obtained when melt blending was carried out at
190 ̊C at 100 rpm rotor speed for 9 minutes for a blend of TPU with PDMS in the proportion of 70/30 by volume. Confirmatory tests were carried out to verify the optimized formulation. Blend morphology studies revealed that PDMS phase gets uniformly dispersed in a matrix of TPU. These blends are expected to be utilized for biomedical applications such as surgical implants and biomedical devices
Piezoelectric Transducer as an Energy Harvester: A Review
No full textOver the years, energy harvesting technologies have been used in various self-powered systems. These technologies have several methods of application depending on their usage. Renewable energy is one of the types of energy harvesting technologies where energy is generated from naturally replenished sources. One of the energy harvesting methods that is commonly used is piezoelectric transducers. Piezoelectric materials are groups of elements that can be used to generate electricity when mechanical energy is applied. When external mechanical stress is applied, the inner lattice is deformed, resulting in the separation of the positive and negative centers of the molecule and thus the generation of a small dipole. Therefore, this paper aims to discuss the output of the piezoelectric transducer by reviewing it depending on two different material types and in other energy harvesting structures. Furthermore, a comparison was made in order to compare the power output of the two materials. Similarly, the most used piezoelectric transducer structures for power harvesting applications were revised. In addition, the parameters that affect the value of the generated power output were discussed using the figures of merit (FOM) concept. Moreover, the according to the FOM concepts, when stress is applied, the electrical energy extracted from a piezoelectric energy harvesting material is determined by the change in stored electrical energy within a piezoelectric material. The figures of merit (FOM) depend on the piezoelectric strain and its permittivity. The piezoelectric strain directly relates to FOM, while the permittivity has an inverse relationship with FOM. Thus, the highest strain constant and low permittivity material will provide the highest energy output. Additionally, lead-based (PZT) material has a strain coefficient d33 equal to 390 Coul/Nx10-12, and permittivity value ranging from 1000 to 3500 and can generate power output that is equal to 52mW at 100Hz, which is higher than the output of the lead-free-based material Barium Titanate (BaTiO3). The output of piezoelectric also depends on the piezoelectric transducer’s structure. The circular diaphragm’s power output is greater than the bimorph cantilever’s power output due to the presence of a proof mass in the center of the diaphragm that provides prestress to the piezoelectric which improves the low-frequency performance of the energy harvester
GEOTECHNICAL PROPERTIES OF NAJRAN SOIL, KINGDOM OF SAUDI ARABIA
No full textCollapsible soils consist of loose, dry, low-density materials that collapse and compact under the addition of water or excessive loading. These soils are distributed throughout the world, specifically in areas of young alluvial fans, debris flow sediments, and loess (wind-blown sediment) deposits. The basic objectives of this study are to describe the properties and characteristics of collapsible soils such as: Origin and occurrence, structure, and composition of collapsible soils. This study also investigates the collapsibility characteristics and behavior of the materials with particular reference to their response to wetting under different stress levels. Undisturbed soil samples from Najran area situated in the south of Saudi Arabia have been collected and studied by using both single and double oedometer tests. The results show that the highest value of collapse potential (CP=11.07%) of Najran soil as given by double Oedometer tests which represents a severe trouble according to [1]
An improved Aquila optimization with fuzzy model based energy efficient cluster routing protocol for wireless sensor networks
No full textDue to the latest advances in microelectronics, wireless sensor networking (WSN) has been introduced in many applications. The flow of event data in WSN applications requires timely and reliable distribution so that immediate response and appropriate action can be taken. However, the limited power supply to the sensor terminal causes a transmission between the delay on the way to the base station and the power consumption. Clustering techniques are essential in developing the WSN routing algorithm that improves network operating time and power efficiency. However, due to the unbalanced power consumption between the terminals, the WSN is the optimal, energy efficient routing. In this work, we propose an energy efficient cluster based routing protocol (EEC-HO) for WSN using hybrid optimization algorithm. We introduce an improved Aquila optimization with fuzzy (IAO-Fuzzy) model for optimal and efficient cluster formation and cluster head (CH) computation. The main objective of proposed IAO-Fuzzy model used to compute the trust degree of each node, the highest trust node is considered as CH. After that, the hybrid beetle search induced decision making (BSDM) algorithm for optimal path selection to transfer data transfer between two nodes
Hygrothermal Performance of Roofs with High Initial Construction Moisture Subjected to Hot Climate
No full textMoisture accumulation in the building components/assemblies that form building envelopes can lead to material deterioration and moisture related issues such as mould growth. As a part of the building envelope, this study focusses on assessing the moisture performance and energy performance (i.e., hygrothermal performance) of roofing systems. As roofs can be built with high initial construction moisture, numerical simulations were conducted with and without high initial construction moisture in order to investigate: (a) the hygrothermal performance of cool and black roofs having material layer with high initial construction moisture content, (b) the time needed so that the moisture content reaches acceptable level as per the building code requirements, (c) whether moisture accumulation and mould growth occur in the roofs, and (d) the energy savings as a result of installing white/cool roof instead of black roof. An advanced numerical model is used to conduct the numerical simulations for black and cool roofs when they are subjected to hot climate. This model solves simultaneously the Heat, Air and Moisture (HAM) transport equations in all layers of the building assemblies. The model was extensively validated by comparing its predictions with the experimental data of different building components at various operating conditions. For the roofing systems investigated in this paper, the results showed that mould growth occurred in the black and cool roofs only for the case with high initial construction moisture. The mould has totally disappeared after 378.8 day for the black roof and 479.3 day for the cool roof. The temperatures of the cool roof were much lower than those for the black roof. The total yearly energy load with the black roof was 77% greater than that with the cool roof
Generation Transcritical Flow Influenced by Dissipation over a Hole
No full textTranscritical flow of a stratified fluid over an obstacle for negative forcing amplitude (hole) that generation upstream and downstream, connected by an unsteady solution is examined. In the weakly nonlinear, weakly dispersive regime, the problem is formulated in the forced Korteweg-de Vries-Burgers framework. This is done by including the influence of the viscosity of the fluid beyond the Korteweg-de Vries approximation. The results show that the influence of viscosity is crucial in determining various wave properties, including the amplitudes of solitary waves in the upstream and downstream directions, as well as the widths of the bores. We focused here on weak damping and the outcomes are prepared for transcritical, supercritical, and subcritical flows. In general, the outcomes are not qualitatively similar to those from the forced Korteweg-de-Vries equation when the value of the viscous is small, interesting differences emerge as the magnitude of the value of viscous increases
Arbitrary (k, l) States-Solutions of the Dirac and Schrödinger Equations Interacting with Improved Spatially-Dependent Mass Coulomb Potential with an improved Coulomb-like tensor interaction Model for H-atoms from 3D-RNCS and 3D-NRNCS symmetries
No full textThe deformed Dirac equation has been investigated, in the context of 3D-relativistic noncommutative space (3D-RNCS) symmetries, using the improved spatially dependent mass Coulomb potential with an improved Coulomb-like tensor interaction (ISDM(CP- CLTI)) model under the conditions of spin symmetry and pseudospin symmetry. The ISDM(CP-CLTI) model is the combining the spatially dependent mass Coulomb potential with the Coulomb-like tensor interaction (CP-CLTI) and the two central terms that are generated to the topological defects of spacespace. Within the confines of the parametric Bopp shift method and conventional perturbation theory, the new relativistic and non-relativistic energy eigenvalues for the hydrogen atoms (H-atoms), such as He, Li+2, and Be³+ under the ISDM(CP-CLTI) model have been derived. The novel values E (n, C, то, т₁, H, O, 7, X. j, l, s, m) and E (n, C, mo, m₁, ,H, O, 7, X. j, 1, 1, 3, m) that we discovered examined to be dependent on the noncommutativity parameters (NP) (Θ, σ, χ), mixed potential depths C/q, mo, m₁, H), and quantum atomic discrete quantum numbers (j, k, l, s, m, l, š, m). We have obtained several interesting special examples within the framework of relativistic extended quantum mechanics, which we believe will be of interest to the expert researcher. We were able to retrieve the typical results of relativistic and non-relativistic examples in the literature when we applied the three simultaneous constraints (Θ,σ, χ) → (0,0,0). Compared to previous models that are known from the literature, our new model had novel physical characteristics