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Mixing and agitation processes are essential in many industries for the homogenization of simple and complex fluids. However, for non-Newtonian fluids, which may thin or thicken under shear stress, specific challenges arise. In this context, researchers have used standard anchor agitators to scrape the walls of the tanks, primarily generating tangential flow. In this context, researchers have used standard anchor stirrers to scrape the walls of the tank, primarily generating a tangential flow. Although this method is effective, it has certain limitations that motivate the main objective of this study, namely to promote both axial flows while maintaining the tangential flow. This research focuses on the numerical modeling of laminar flow in a mechanically agitated tank containing a shear-thinning non-Newtonian fluid. It examines the impact of the fluid’s behavior index, the Reynolds number, as well as various stirrer configurations, including a standard anchor and a flexible blade anchor, to optimize mixing. An innovative agitator design has introduced unique adaptability with a single design modification, enabling transitions between axial flow, which promotes better homogeneity and tangential flow, suited for standard operations. This versatility has proven particularly beneficial for complex fluids with variable rheological properties. The differential equations governing these physical phenomena, including the continuity, momentum and energy equations, are solved using the finite element method. The main results showed that the new flexible blade anchor configuration enhances axial velocity and reduces dead zones at the bottom of the tanks while maintaining an overall tangential flow. Additionally, this configuration provides a significant benefit in terms of energy consumption. Indeed, this new configuration with the largest inclination angle achieved the best results, reducing power requirements by up to 50% under moderate operating conditions. These results highlight the optimization of mixing processes, improving not only the efficiency and quality of the agitation system but also reducing the energy consumption.

In this work, typical design, production, and testing procedures for a small unmanned helicopter are explained and performed. In doing so, preliminary sizing of the helicopter and three main disciplines are conducted: aerodynamic analytical and numerical simulations, power calculations, and structure analysis assessment. First, a thorough survey is implemented to obtain the trends for the maximum take-off weight versus some design constraints such as rotor diameter, motor power, payload, and empty weight. Performance calculation results are obtained to figure out all aspects that correspond to the specified mission. The designed rotor geometry along with the aerodynamic characteristics and flight performance variables is then validated using the blade element theory and numerical simulations. Second, based on the power curves obtained for different flight regimes, an electric brushless motor is selected. The numerical simulations (Computational Fluid Dynamics) analysis is used to enhance the selection which implies that the motor power should be greater than 5.4 kW to overcome the drag forces. The motor power selection corresponds to a maximum rotor pitch angle of 15^∘ and a maximum rotor speed of 1450 RPM. Then, the aerodynamic loads are used as an input for the structural analysis using one-way coupling of fluid–structure interaction (FSI) and consequently designing the internal structure of the blade. Eventually, the internal structure manufactured using carbon fiber-reinforced polymer (CFRP) by applying a combined technique between wet layup and compression molding. The blade is statically tested compared with numerical finite element model results. The fuselage structure along with hub and tail units is manufactured and assembled with the existing on-shelf components to examine the helicopter lift capability with different payloads up to 9 kg. The results show that the detailed design process is significant for manufacturing such blades and the helicopter is capable of lifting off the ground with various payloads depending on the rotor pitch angles (8^∘, 12^∘, and 15^∘) at a constant rotor speed of 1450 RPM.

The aerodynamic characteristics of a propeller near the rigid ground and static water surface have been investigated numerically and experimentally. The aerodynamic performance of the propeller in various elevations from the ground and the static water surface and tilt angle settings at constant propeller rotational speed have been evaluated. The results indicated that ground and water surface can strongly affect the aerodynamic performance of rotating propellers in close distances up to 1.24 times its diameter. A decrease in the distance between the propeller rotation plane and the surface leads to a remarkable increase of the propeller efficiency up to 15%. Similarly, it has been found that the tilt angle has also noticeable effect on the near-surface aerodynamic characteristics of the propeller. At a tilt angle above 25^∘ almost at any distance from the surface, near-surface effects tend to vanish and propeller thrust reaches its value of free flight condition. Drawing a comparison between near-ground thrust values of the propeller and the thrust values over the surface of water at any predetermined distance from surfaces and tilt angle indicated that the rigid ground has notably higher thrust efficiency than the flexible water surface. At a height of 0.3D (D is propeller diameter) from the ground surface, thrust increased by about 15% while the growth of thrust efficiency near the water surface was about 8%. CFD and Experimental results confirm each other.

The buoyancy driven exchange flow through the large openings in horizontal partitions occurs in many practical situations such as in enclosed regions with a ceiling opening and a heat source such as fire. The density difference between two compartments arises partly due to difference in composition and partly from the difference in temperature. A heavier fluid located on the top of a lighter fluid and separated by a horizontal vent constitutes a gravitationally unstable system. Horizontal vents produce flow, which are unstable with irregular oscillatory behavior. However, when lower compartment is slightly pressurized the flow becomes stable and unidirectional. A numerical study has been performed to characterize the bi-directional flow and transition to unidirectional flow through a horizontal vent in an enclosure, due to differences in pressure and density across the vent. Fresh and salt water has been considered as working fluids to create density difference across the vent with a pressure field imposed in the lower compartment. The pressure in the lower region was increased to find the critical pressure corresponding to transition to unidirectional from bi-directional flow. Unsteady, 2D axisymmetric, incompressible Navier–Stokes equation along with species, turbulence and continuity equation have been solved with finite volume method using the in-house computational fluid dynamics (CFD) code. Several cases were examined to compute the critical pressure for various density differences for low opening aspect ratio. The code has been validated with reported experiments and used to simulate various other practical cases occurred during fire induced flow through such openings.

Turbulent Schmidt number as an important parameter in computational fluid dynamic (CFD) simulations is strongly dependent on height, whereas it is mostly considered to be constant in the literature. This paper presents a new variable turbulent Schmidt number formulation which can calculate the relative concentrations (RCs) in neutral atmospheric conditions more accurately. To achieve this aim, RCs from continuous releases are calculated in different distances by the analytical Gaussian plume mode. CFD simulations are carried out for single stack dispersion on a flat terrain surface and an inverse procedure is then applied so that different turbulent Schmidt numbers are used as inputs to determine the RCs to select the “best-fit” turbulent Schmidt number value. This process is continued for different heights to fit a curve to obtain the new formulation for turbulent Schmidt number varying with height. The values are compared with experimental results. The comparison indicates that the new formulation for turbulent Schmidt number is more accurate and reliable than previous research works.

Lateral intakes are hydraulic structures used for domestic, agricultural and industrial water conveyance, characterized by a very complex three-dimensional morphodynamic behavior: since streamlines near the lateral intake are deflected, some vortices form, pressure gradient, shear and centrifugal forces at the intake generate flow separation and a secondary movement, responsible for local scour and sediment deposition. On the other side, the modeling of flows, besides the sediment transport, in curved channels implies some more complications in comparison with straight channels. In this research, this complex process has been investigated experimentally and numerically, with the mechanism of sediment transport, bed topography evolution, flow pattern and their interactions. Experiments were performed in the Laboratory of Tarbiat Modares University, Iran, where a U-shaped channel with a lateral intake was installed and dry sediment was injected at constant rate into a steady flow. Due to the spiral flow, the bed topography changes significantly and the bed forms in turn affect the sediment entering the intake. Different from the previous works on this topic which were mainly based on laboratory experiments, here, Computational Fluid Dynamics (CFD) numerical simulations with FLUENT software were also performed, specifically with the two-phase Eulerian Model (EM) and Discrete Phase Model (DPM), at the aim of evaluating their performance in reproducing the observed physical processes. This software is used for a large variety of CFD problems, but not much for simulating sediment transport phenomena and bed topography evolution. The comparison of the results obtained through the two models against the laboratory experimental data proved a good performance of both the models in reproducing the main features of the flow, for example, the longitudinal and vertical streamlines and the mechanism of particles movement. However, the EM reveals a better performance than DPM in the prediction of the secondary flows and, consequently, of the bed topography evolution, whereas the DPM well depicts the particles pattern, predicts the location of trapped particles and determines the percentage of sediment entering the intake.

The numerical models so calibrated and validated were applied to other cases with different positions of the intake in the bend. The results show that mechanism of sediment entrance into the intake varies in different position. If the intake is installed in the second half of the bend, the sediment accumulates along the inner bank of the bend and enters the intake from downstream edge of intake; on the other side, if it is placed in the first half of the bend, the sediment accumulates along both the inner and the outer bends and, therefore, more sediment enters the intake. Also the results of the simulations performed with the DPM model for different positions of the lateral intake show that for all discharge ratios, the position of 120^∘ is the one which guarantees the minimum ratio of sediment diverted to the intake (Gr).

Magnetohydrodynamic analysis of the nanofluid flow is extremely noteworthy in industrial applications. This study investigates the application of the nonhomogeny magnetic source on the migration of fluid with nanoparticles within the angled junction. In this work, Ferro particles are injected into the water flow to intensify the influence of the FHD on nanomaterial flow. To perform computational study on nanofluid in the junction, the FVM with SIMPLEC model was selected. According to our results, the existence of the nonhomogeny magnetic field produces the circulation in the vicinity of the junction and decreases the mineral sedimentation on the junction wall. In existence of two magnetic sources, Nu augments by 20% when the Reynolds number of nano flow is augmented from 50 to 100. When results of four sources of nonhomogeny FHD sources are compared with that of two magnetic sources, it is detected that the mean Nusselt number approximately increases 57 % inside the domain.

In recent decades, cardiovascular disease and stroke are recognized as the most important reason for the high death rate. Irregular bloodstream and the circulatory system are the main reason for this issue. In this paper, Computational Fluid dynamic method is employed to study the impacts of the flow pattern inside the cerebral aneurysm for detection of the hemorrhage of the aneurysm. To achieve a reliable outcome, blood flow is considered as a non-Newtonian fluid with a power-law model. In this study, the influence of the blood viscosity and velocity on the pressure distribution and average wall shear stress (AWSS) are comprehensively studied. Moreover, the flow pattern inside the aneurysm is investigated to obtain the high-risk regions for the rupture of the aneurysm. Our results indicate that the wall shear stress (WSS) increases with increasing blood flow velocity. Furthermore, the risk of aneurysm rupture is considerably increased when the AWSS increases more than 0.6. Indeed, the blood flow with high viscosity expands the high-risk region on the wall of the aneurysm. Blood flow indicates that the angle of the incoming bloodstream is substantially effective in the high-risk region on the aneurysm wall. The augmentation of the blood velocity and vortices considerably increases the risk of hemorrhage of the aneurysm.

The morbidity and mortality of aneurysm rupture have raised significantly in current years. In this research, numerical investigations have been performed to disclose the impacts of hemodynamic on the breach and growth of the Intracranial Aneurysms (IA) in the middle cerebral artery (MCA). To perform this research, computational fluid dynamic (CFD) methodology is employed to model the non-Newtonian blood stream through the IA. 3D model of IA is chosen for the analysis blood flow. Wall shear stress (WSS) was evaluated and compared at the high-risk region, where the probability of rupture is high. This study offers precise information and insight about the influence of blood viscosity and velocity on the danger of the aneurysm rupture in the MCA. Our outcomes show that the location and orientation of the aneurysm have direct impacts on the growth of the aneurysm. The main attention of this research is to reveal more vibrant facts about the primary reasons for the rupture of the aneurysm and present connection among the rupture points and the local hemodynamic features. This work tries to demonstrate the critical area on the aneurysm surface by analyzing the WSS and pressure distribution.

The aerodynamic behavior of sweptback wing configurations with bio-inspired humpback whale (HW) leading-edge (LE) tubercles has been investigated through computational and experimental techniques. Specifically, the aerodynamic performance of tubercled wings with symmetric (NACA 0015) and cambered (NACA 4415) airfoils is validated against the baseline model at various angles of attack ($\alpha )$. The $t$/$c$ ratio of the HW flipper is strategically reduced to 0.15 for ascertaining the flow control potential of the bio-inspired wings with sweptback configuration. It is a novel effort to quantify the effect of the leading-edge protuberances on stall delay, flow separation control and distribution of streamline vortices at unique $t$/$c$ ratio outside the thickness range of HW flipper morphology. Four tapered sweptback wing models (Baseline A, Baseline B, HUMP 0015, HUMP 4415) are used with the amplitude-to-wavelength ($A∕\lambda )$ ratio of 0.24 and Reynolds number about $Re=1.83\times 10^5$. The chordwise pressure distributions are recorded at the peak, mid and trough regions of the tubercled wings through a detailed wind tunnel testing and validated with numerical analysis. Additionally, the flow characteristics over the bio-inspired surfaces have been qualitatively analyzed through the laser flow visualization (LFV) technique to reveal the influence of laminar separation bubbles (LSBs). The essential aerodynamic characteristics such as boundary layer trip delay, vortex mixing, stall delay, and flow control at different AoA are addressed through consistent experimental data. As the sweptback configuration is a primary choice for airplane wings, the improved aerodynamic characteristics of the tubercled wings can be effectively utilized for the design of novel lifting surfaces, hydroplanes and wind turbines in the near future.

In computational fluid dynamics (CFD), there is a transformation of methods over the years for building commercially coded software. Each method has predicted its own set of importance, but the exportation and prediction of data are some of the crucial elements for post-processing and validating results. In the present investigation, a detailed comparative analysis is performed over finite difference method (FDM) and finite volume method (FVM) method for the 1D steady-state heat conduction problem over a 1-m-long plate. The comparison was made between solution creation and validation between FDM and FVM for the analytical and computational scheme. The convergence-dependent study is performed as multi-objective optimization to predict how artificial neural network (ANN) can be used to verify and validate the solution of CFD.

The aim of this paper is to provide an implicit transient numerical formulation of novel minichannel-coupled passive thermal arrangement to cool down unidentical IC chips on substrate board. In the proposed design, PCM is integrated in the minichannel which is kept at the periphery of IC chips. Through means of direct conduction from substrate board, phase change material absorbs latent heat and allows it to change its phase from solid to liquid by providing effective thermal cooling performance in system. A comparative study is developed between without PCM, with minichannel-coupled PCM and optimized single minichannel near the heat source. Results show that between paraffin wax, N-Eicosane and ATP 78 PCM, N-Eicosane can provide effective cooling performance. With the N-Eicosane temperature in the system controlled from 53.234^∘C of the generic model to 51.520^∘C and a significant 1.74^∘C of temperature drop compared with the generic model, an additional 0.5^∘C of temperature reduction occurs as compared with the case of paraffin wax PCM and 1.35^∘C when compared with ATP 78 PCM.

In the recent decades, the main reason for the high death rate is related to cardiovascular disease and stroke. In this paper, numerical studies have been done to investigate the hemodynamic effects on the rupture of middle cerebral artery (MCA) in different working conditions. In this work, the effects of the blood viscosity and velocity on the pressure distribution and average wall shear stress (AWSS) are fully investigated. Also, the flow pattern inside the aneurysm is investigated to obtain the high-risk regions for the rupture of the aneurysm. Our findings show that the wall shear stress increases with increasing the blood flow velocity. Meanwhile, the risk of aneurysm rupture is considerably increased when the AWSS increases more than 0.6. In fact, the blood flow with high viscosity expands the high-risk region on the wall of the aneurysm. Blood flow indicates that the angle of the incoming bloodstream is substantially effective in the high-risk region on the aneurysm wall. The augmentation of the blood velocity and vortices considerably increases the risk of hemorrhage of the aneurysm.

The precise evaluations of intracranial aneurysms (IAs) are highly prominent for the treatment and control of aneurysm rupture. Computational fluid dynamic (CFD) simulations based on angiography image is a reliable tool for the recognition of high-risk region and aneurysm status in recent years. In our study, the CFD is used to investigate the impacts of blood hematocrit and coiling techniques on the risk of aneurysm rupture. To do this, wall shear stress (WSS), oscillatory shear index (OSI) and pressure distribution on the wall of an aneurysm are comprehensively evaluated in various coding porosities and blood viscosities. One-way Fluid Solid Interaction (FSI) technique is applied to investigate the non-Newtonian, pulsatile blood stream inside the sac of the aneurysm. Impacts of two coiling porosities and blood hematocrits of 0.3 and 0.5 on blood features inside the sac are also analyzed. The influence of the blood mass flow rate in four different time instants of blood cycles on the size of the high-risk region on the aneurysm wall is demonstrated. Our results show that more than 40% reduction is noticed when the hematocrit (HCT) of blood is reduced from 0.5 to 0.3 in different time instants. Our findings also reveal that decreasing the porosity from 0.96 to 0.74 in the peak systolic stage results in a 28% reduction in the maximum OSI at specific HCT = 0.4.

In this paper, the variable camber morphing strategy is adopted in a NACA airfoil through computational investigation to enhance the lift to drag ratio ($L∕D)$ specifically for military UAV applications. The typical mission profile is also focused on enhancing the aerodynamic performance of the UAV during various flight segments by variable camber morphing. The airfoil camber is changed dynamically at different instances based on the mission profile requirements thereby altering the $L∕D$ characteristics. The concept of bio-inspired aerodynamics has received a greater attention in recent years because of the proven nature oriented real-time application. Hence, the concept of bio-inspired variable camber morphing is proposed herein that minimizes the use of unconventional control surfaces to attain the required performance at different segments of flight. MQ9 Reaper UAV model is chosen to implement the proposed variable camber morphing strategy at the mission flight segments. NACA 4412 cambered airfoil has been considered as the baseline model airfoil for the present study because of its higher zero lift angle characteristics. The lower camber of the airfoil section is changed from 1% to 3% at different angles of attack (AoA) for the time instances such as 1s, 2s and 3s, respectively. The lift coefficient ($C_l)$ of the airfoil is also significantly increased through camber morphing at different flight segments during each time step with negligible flow separation as observed through streamline patterns. Hence, the friction drag coefficient is also retained under optimum level as concluded through the boundary layer profiles.

CFD-modeling for numerical investigation is used in a wide range of applied tasks, e.g. in fluid mechanics. To better understand the effect of operational parameters on the final results, some tasks are associated with carrying out monotonous, repetitive calculations for a wide range of operational parameters such as velocity, flow direction and temperature. In this paper, a Python-based code for automation of the repeating calculations in CFD-modeling was developed and described. The automation code was tested for CFD-modeling in Ansys Fluent for two flow dynamic tasks: a simple 2D-geometry — NACA0018 airfoil, and a complex 3D-geometry — packed bed with heat transfer. Three different computers with various computational power were used for the comparison. The results of CFD-modeling were compared with the experimental data. The efficiency of using Python-based code was evaluated through comparison with the results of manual (without automation) calculation. It was established that the application of the Python-based code does not affect the accuracy of numerical results. At the same time, utilization of the Python-based code can save up to 25% of computation time for the simple 2D-geometries with a moderately low number of elements in the mesh, and up to 15% for the complex 3D-geometries with a number of elements in several millions. The compiled Python-based code is attached as supplementary material to this paper.

In this research work, we proposed a modern structured packing (SP) with perforated sheets with a specific surface area of 860${\mathrm{\text{m}}}^2$/${\mathrm{\text{m}}}^3$, which was determined using numerical techniques. This work aims to evaluate the major characteristics of PACK-860 for instance, height equivalent to a theoretical plate (HETP), dry pressure drop (DPD) and wet pressure drop (WPD). Additionally, the flow construction was defined for specific packing via computational simulation. To evaluate the value of HETP, DPD and WPD, the three-dimensional (3D) computational fluid dynamics (CFD) simulation with the Eulerian–Eulerian (EE) multi-phase method applied in this paper. According to the findings of this research, the performance of the mass transfer (MT), WPD and DPD was enhanced with the perforated-on sheets of packing. Based on the observation, numerical results are consistent well with the theoretical data which reveals the consistency of CFD tools for modeling methods to separation applications.

The importance of the blood flow feature on the hemorrhage of the cerebral aneurysm is confirmed by surgeons and scientists. In this paper, the effects of blood hemodynamics on the growth and rupture of the Internal Carotid Intracranial (ICA) are fully investigated. This study tries to demonstrate the blood feature inside the ICA at different time stages. Besides, the effect of coiling on blood characteristics is extensively studied in this research. Computational Fluid dynamic (CFD) is used for the analysis of the blood hemodynamics on the wall shear stress and pressure distribution within the aneurysm. Obtained results indicate that reducing the coiling porosity from 0.89 to 0.79 declines maximum WSS by about 26% and 61% for $\mathrm{\text{HCT}}=0.35$ and 0.45, respectively, at the peak systolic stage. Our findings show that decreasing the porosity (or increasing coiling fraction) would decrease the maximum OSI by more than 55% in high blood viscosity of $\mathrm{\text{HCT}}=0.45$.

The geometrical aspects of the saccular aneurysm are an important factor for the rupture of aneurysm. In this paper, the effects of the sac centerline on the aneurysm rupture are fully investigated. Our attention is to disclose the important factors related to aneurysm rupture in different time instants. CFD method is applied for the analysis of WSS, OSI, pressure and velocity inside the saccular aneurysm with different sac centerlines. Our results also show that the coiling technique could sufficiently decrease the risk of rupture since decreasing the coil porosity (increasing the coil permeability) would increase the OSI and pressure and decrease WSS and blood velocity inside the aneurysm sac.

This study recommends a novel structured packing (SP) PACK-860X with a specific surface area of 860m²/m³, which is defined utilizing a numerical method. We attempt to investigate the main properties of PACK-860X for illustration, height equal to a theoretical plate (HETP), dry pressure drop (DPD) and wet pressure drop (WPD). In addition, the flow pattern is expressed for packing through computational simulation. To assess the amounts of HETP, WPD and DPD, the 3D CFD simulation with the Eulerian–Eulerian multi-phase technique is employed in this work. Based on the results of this work, WPD and DPD are improved. According to the data, numerical outcomes are in good agreement with the theoretical results, which shows the reliability of CFD methods for modeling the separation processes.