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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.

This paper describes a simple shared-memory parallel implementation of an octree adaptive mesh Computational Fluid Dynamics (CFD) code with an explicit time discretization scheme. The parallel performance of the code when running a realistic simulation gives a serial code fraction of no more than 13%. This should be suitable for small multicore engineering workstations where a simple code is desired and medium-sized simulations are sufficient.

In this paper, the effect of geometrical parameters of centrifugal fan on performance has been presented with a system approach. Often, the operators or the design engineers focus on the immediate requirements of the engine/equipment and they neglect the broader question of how the fan parameters are affecting the equipment. For instance, change in fan angles will change the performance e.g., airflow rates and efficiency. However, it also affects the contaminants build-up on the blades. Blade angle with higher angle of attack will promote contaminants build-up on blade surfaces, which in turn causes performance degradation and unstable operation. The system approach in fan parameter selection will result in a more reliable system. Significance of other fan parameters is also discussed. We present an experimental setup and validated computational fluid dynamic (CFD) model. Fan power consumption is determined experimentally and compared with the CFD model. Further parametric simulations were carried out to investigate the effect on fan performance. Effect of system resistance, inlet and outlet angle, blade thickness, and no-uniform spaced blades has been described with discussions on industrial relevance. A fan with higher flow rates is desirable to reduce engine temperatures and enhance the durability. However, higher flow rates result in more fan power consumption at a given fan speed. The test results suggest that a fan with higher power coefficient does not affect the vehicle's mileage significantly. This paper will help design engineers in making informed decision about the interaction between the fans and system, and its effect during the operation.

The ventricular assist device (VAD) assists the patients with heart diseases for limited and prolonged periods. This device synchronizes with normal heart activities to help foster its performance. Consequently, its sensitive design requires high accuracy. The pumps are the essential part of every VAD which should operate in wide ranges of flow and pressure. As there are various types of VAD under different designs, it is neither practical nor plausible to experimentally/clinically investigate their performances. Therefore, in the concurrent study, a numerical study was carried out on four different generation prototypes of VAD pumps for reaching an optimum design. Using computational fluid dynamics (CFD) method, the software derived, showed and streamlined the flow field shear stress both inside the VAD and its blades. Furthermore, the vortices and flow rate-pressure curves were observed. The results showed that the curved blade pumps operate better compared to that of the straight blade types, concerning the provision of enough pressure and less damage to the red blood cells. The results have implications not only for comparing different types of VAD designs but also for understanding the resulted shear stresses and pressures as a result of the blade’s structure.

In this study, the flow structure and effect of different pump rotational speeds on a centrifugal pump’s performance are experimentally and numerically investigated. The internal flow field pattern within the pump has been analyzed and discussed using the CFD technique. The numerical results are compared with experimental data under a wide range of operating conditions. The comparison results between them have indicated a considerable agreement. The pressure variations are gradually increasing from inlet to outlet impeller of the pump. The results note that when the impeller rotates near the tongue region, the pressure in this region was higher than in other parts. Also, the interaction between the impeller and volute tongue region is actually according to the impeller blades’ relative position concerning the tongue region. Furthermore, the pressure and velocity variations within a centrifugal pump increase with rotational impeller speed.

Smoothed Particle Hydrodynamics (SPH) is fast emerging as a practically useful computational simulation tool for a wide variety of engineering problems. SPH is also gaining popularity as the back bone for fast and realistic animations in graphics and video games. The Lagrangian and mesh-free nature of the method facilitates fast and accurate simulation of material deformation, interface capture, etc. Typically, particle-based methods would necessitate particle search and locate algorithms to be implemented efficiently, as continuous creation of neighbor particle lists is a computationally expensive step. Hence, it is advantageous to implement SPH, on modern multi-core platforms with the help of High-Performance Computing (HPC) tools. In this work, the computational performance of an SPH algorithm is assessed on multi-core Central Processing Unit (CPU) as well as massively parallel General Purpose Graphical Processing Units (GP-GPU). Parallelizing SPH faces several challenges such as, scalability of the neighbor search process, force calculations, minimizing thread divergence, achieving coalesced memory access patterns, balancing workload, ensuring optimum use of computational resources, etc. While addressing some of these challenges, detailed analysis of performance metrics such as speedup, global load efficiency, global store efficiency, warp execution efficiency, occupancy, etc. is evaluated. The OpenMP and Compute Unified Device Architecture$(CUDA)$ parallel programming models have been used for parallel computing on Intel Xeon$(R)$ E5-$2630$ multi-core CPU and NVIDIA Quadro M$4000$ and NVIDIA Tesla p$100$ massively parallel GPU architectures. Standard benchmark problems from the Computational Fluid Dynamics (CFD) literature are chosen for the validation. The key concern of how to identify a suitable architecture for mesh-less methods which essentially require heavy workload of neighbor search and evaluation of local force fields from neighbor interactions is addressed.

The paper compares one-point quadrature and analytic integration as efficient alternatives to the standard two-points Gaussian quadrature for CFD finite element codes that use 4-node, bi-linear, quadrilateral elements. The differentially-heated square cavity problem, for which benchmark solutions exist, is used to compare the accuracy and computation time of the three integration methods. The results obtained show that one-point quadrature requires less computational time than analytic integration. Unlike the analytic integration, one-point quadrature also required minor modifications to existing finite-element codes that use two-points quadrature. Moreover, the code that applies Gauss quadrature is easily vecorizable, which is beneficial on supercomputers. In general, one-point quadrature requires an "hour-glass" correction to be made, but for the cavity-flow considered here this was not necessary thanks to the Dirichlet boundary condition applied over a large part of the solution domain.

Computational Fluid Dynamics (CFD) is used to simulate the flow filed in a rotor-casing assembly for different elliptic rotor aspect ratios and inlet flow velocities. The flow was simulated with the rotor fixed at its extreme positions, i.e. vertical and horizontal arrangement. The flow field results were used to ascertain the changes in the efficiency of a rotor-casing assembly. This included: inlet pressure, maximum velocity, and maximum turbulence values. A more fundamental quantity, integrated entropy generation was also calculated. Entropy generation is based on the second law of thermodynamic and accounts for all types of irreversibilties within the assembly. Of the different traditional quantities calculated, only the inlet pressure results were inline with the entropy generation results.

Atherosclerotic plaque formation has been linked to haemodynamic risk factors, such as low and oscillating wall shear stresses (WSS). Experimental and numerical methods have been developed to investigate the mechanisms involved. Computational fluid dynamics (CFD) methods have the advantages of low cost and easily manageable numerical results. In order to obtain physiologically realistic results, CFD can be linked with medical imaging methods, which allow the extraction of in vivo vascular geometry and flow data to be used as input for haemodynamic simulations. Most of the image-based CFD approaches have been based on MRI, which has the disadvantages of relatively high cost and limited availability. Hence, a novel technique based on 3D ultrasound was developed with the advantages of low cost, fast acquisition and high spatial resolution. A methodology was developed to extract geometric information from the ultrasound images, reconstruct the surfaces and generate computational grids for flow simulations of the human carotid artery bifurcation. Additionally, a scheme was devised to utilize Doppler flow information for CFD boundary conditions. Accuracy and reproducibility of the combined imaging and modeling approach were evaluated in vitro and in vivo and the developed protocol was applied to normal subjects. The main conclusion of this work is the feasibility of 3D and Doppler ultrasound based CFD simulations for clinical applications. However, there are several limitations when applying this methodology in carotid bifurcations, i.e. the location of the carotid bulb relative to the jaw bone, which obscures the ultrasound path when the bifurcation is high in the neck. Future work should focus on minimizing the limitations and improve automation and reliability of image processing and reconstruction.

Uncertainty evaluation in metrological applications with computationally expensive model functions can be challenging if it is not clear if the model can be locally linearized and the law of the propagation of uncertainty of the Guide to the Expression of Uncertainty in Measurement can be applied. The use the Monte Carlo method as presented in GUM supplement 1 is not practical as it requires a vast number of model evaluations, which can be very time consuming in case of computationally expensive model functions. For this type of model functions smart sampling approaches can be used to assess the uncertainty of the measurand. In this paper a computational fluid dynamics model of sonic gas flow through a Venturi nozzle is studied. Various smart sampling methods for uncertainty quantification of the model's output parameter mass flow rate are assessed. Other sources of uncertainty of the model are briefly discussed, and a comparison with measurement data and with the results of a 1-dimensional simplified model are made.

The paper presents massively parallel simulation of the flow characteristics in a submersible axial flow pump using OpenFoam code. The calculation is done on a SUGON high-performance computers using 160 CPU core. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the pressure and the velocity of flow distribution in the impeller region is relatively higher than other regions.

To investigate the dynamic performance of spring-loaded pressure relief valve (PRV) under high temperature and high pressure steam (HTHPS) conditions, experiments according to ASME PTC 25 and a new transient numerical simulation method were carried out. The validity of accuracy of the simulation was confirmed by comparing the results of simulation and experiments. It was found that the usage of a vessel (connected to the outlet of PRV) whose diameter is one order higher than the PRV orifice diameter is necessary in the simulation of HTHPS PRV. During the PRV experiments, friction existed between moving disc and fixed components, which could alleviated the fluttering. The experiments and simulation on performance of HPHT steam PRV should be strictly carried out using HPHT steam not air to avoid inacceptable uncertainties.

The purpose of this article is to obtain the transient distribution of flow and valve core stress of the hydraulic poppet valve during opening process. Based the dynamic mesh technology and fluid-solid theory, a numerical model was established using the CFD software. Through comparing the steady displacement simulation results with theoretical values, motion situations of flow, it is shown that the stress of a fixed area changes during the opening process of the valve plug, and the pressure gradient is very large in the valve port. There is a “negative pressure” area in the flow field and the size keeps changing with time, which may cause cavitations. Furthermore, the stress distributions are different even though the displacements of the valve plug are the same due to different velocities at different time. These results provide the basis for the design and optimization of hydraulic poppet valves.

In In order to obtain the transient characteristics of hydraulic poppet valve during opening process, a hydraulic poppet valve dynamic numerical model was proposed based on the CFD and dynamic mesh technique. It is shown that the steady state flow and transient flow fluctuations both decrease along with the increase of the spring stiffness. Furthermore, as the total force on the hydraulic poppet valve plug increase to step up the spring stiffness, the steady state displacement of the valve plug decreases and the valve plug arrives at the equilibrium position faster, which is good for reducing impact and vibration.

This paper presents an innovative design concept for a biomimetic dolphin-like underwater glider. As an excellent combination, it offers the advantages of both robotic dolphins and underwater gliders to realize high-maneuverability, high-speed and long-distance motions. As the first step, a skilled and simple dolphin-like prototype with only gliding capability is developed. The hydrodynamic analysis in the glider using Computational Fluid Dynamics (CFD) method is executed to explore the key hydrodynamic coefficients of dolphin-like glider including lift, drag and pitching moment, and also to analyze the dynamic and static pressure distribution. Finally, experimental results have shown that the dolphin-like glider could successfully glide depending on the pitching torques only from buoyancy-driven system and controllable fins without traditional internal movable masses.

Hydraulic performance analysis was discussed for a type of turbine on generator used for LWD. The simulation models were built by CFD analysis software FINE/Turbo, and full three-dimensional numerical simulation was carried out for impeller group. The hydraulic parameter such as power, speed and pressure drop, were calculated in two kinds of medium water and mud. Experiment was built in water environment. The error of numerical simulation was less than 6%, verified by experiment. Based on this rationalization proposals would be given to choice appropriate impellers, and the rationalization of methods would be explored.