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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.

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.

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.