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After introduction on a new multislice computed tomography (MSCT) scanner, it has become possible to produce high-speed CT angiography (CTA) that selected preferred method for imaging in emergent vascular conditions. On the other hand, the imaging of blood vessels is often referred to as magnetic resonance angiography (MRA). Both of angiography offers the good quality of three-dimensional information of the vessels. In this study, patient specific model were reconstructed using multi-slice computed tomography (CT) and magnetic resonance imaging (MRI). The optimal transit time from intravenous injection to enhancement cardiovascular system was determined using a contrast bolus tracking technique with CT examination and phase contrast magnetic resonance angiography (PC-MRA). The purpose of this study was to describe a novel blood flow visualization and analysis in the human cardiovascular system in more detail by constructing actual three-dimensional (3D) flow and simulated model using computational flow dynamics (CFD) methods. CFD streamlines were displayed using a special illumination technique with blood pressure display, which gives a much better spatial understanding of the field's structure than ordinary constant-colored lines. Real vector display using PC-MRA was also expressed to compare with the CFD simulation. On conclusion, patient specific approach using actual blood flow with PC-MRA and CFD were effective to estimate blood flow state of the cardiovascular system.

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.

Several new ideas for anisotropic adaption of un- structured triangular grids are presented with par- ticular emphasis to fluid flows computations in- volving multiscale phenomena.

To predict the sailing resistance of a high-speed vessel accurately, variations in hull gesture during the voyage need to be considered. Using computational fluid dynamics (CFD), both the Reynolds-averaged Navier–Stokes (RANS) equations and the ship's motion's equation are solved, giving the ship's navigation attitude and resistance. The numerical calculation then provides the values of high speed vessel's resistance and navigation attitude. Compared with the corresponding experimental data, the results show that this method's accuracy meets the requirements for engineering application. Ship designers can use the CFD result to design the shape of ship hull.

This paper describes a computational study undertaken to compute dynamic stability derivatives for a UAV in angles of attack ranging from -10 degrees to 20 degrees, based on the computational fluid dynamics (CFD)-force oscillation technology. A time-accurate method of simulating dynamic flow around low speed UAV is established and validated with a dynamic stall case of NACA0012 airfoil. The S-A and SST k−ω turbulence models are evaluated for their applicability in low-Reynolds flow. An integration method is used for calculating pitching and rolling dynamic derivatives. Time steps, iterations, amplitude and reduced frequency are analyzed for their effects on results. Based on the simulation database, the reasons for amplitude having slightly influenced dynamic derivatives and dynamic derivatives dramatically changing near the low reduced frequency are discussed. The results show that the dynamic derivatives obtained with integration method are reasonable.

Ship energy conservation is currently a hot research area in the field of ship and marine engineering. An effective way of reducing a ship's wave resistance is to use a bulbous bow, and this has been widely used in all types of merchant ships. In this study, a drag-reduction bulbous bow was added above the sonar cover of DTMB5415. With three kinds of drag-reduction bulbous bows designed, the best installation location for each bulbous bow is first found without taking the ship's pitching and heaving movements into account. Then, the influence of the twin-bulbous-bow on DTMB5415's navigation performance is studied by taking the ship's pitching and heaving into account. The results show that all three optimized types of twin-bulbous-bows designed are effective in reducing drag.

Air-intake filter of the ventilation system on offshore platform plays an important role in providing sufficient and clean air and is normally composed of the inertial stage and the multi-layer gauze stage. In this article, numerical simulation and experimental research were carried on to study the flow field characteristics of the air-intake filter. Flow in the inertial stage was regarded as a 2D case, and the multi-layer gauze stage was simplified to an orthogonal array type. With FLUENT code, the quadratic polynomial of the resistance with velocity, the permeability α and the pressure jump coefficient C₂ of the composite stages were obtained on the basis of certain simplifications. Accordingly, one source term was added into the momentum equation, and the flowing characteristics of the filter compounding the inertial stage and the gauze stage were computed based on the porous medium model. The simulating results of the total pressure loss are validated by the designed wind-tunnel experiment satisfactorily. This method has much reference value on the design and optimization of the air-intake filter on offshore platforms and other occasions.

In this paper, to investigate a compound casting process for creating Al coating layer for Mg alloy, a computational fluid dynamics (CFD) model is developed using the VOF method to simulate the molten Mg drop impact on the Al substrate at solid state. A spreading factor, which is the ratio to the varied diameter of the Mg droplet after impacting on the Al substrate and its initial diameter before the impact, is used to describe and measure the impact process generated by the Mg drop, which could be divided into several steps: spreading, retracting and oscillating, and equilibrium as final step. Some key parameters are investigated via parametric studies: impact velocities, initial diameters of drop, the temperature of the Al substrate, which have important influences on the quality of compound casting products. The spread diameter of the Mg drop increases when the impact velocity and initial diameter of drop increase. While the impact velocities and initial diameters of the drop are larger than critical values, the liquefied Mg may partially have bubbles. The higher the temperature of the Al substrate is, the larger the spread diameters could be obtained, though oscillating and equilibrium steps take more time to finish in the CFD simulations developed.

OpenFOAM is an object-oriented C++ library of classes and routines of use for writing CFD codes. It has a set of basic features similar to any commercial CFD solver, such as turbulence models and discretization schemes. The paper presents the numerical studies of sediment wear in a centrifugal pump impeller using OpenFOAM code, which is an Open Source CFD Package. The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. Hashish erosion model was implemented in this code. The sand volume fraction distribution, sand erosion rate distribution, wall shear strain rate distribution and wall stress distribution in the impeller were analyzed. Simulation results have shown that the main sediment wear of impeller is at the suction side of the inlet and the pressure side of the outlet.

A new kind of Opposite Axial Piston Engine (OAPE) in small scale specially designed for the portable generating system was presented. The working theory of OAPE was studied, based on which the combustion process was simulated in FLUENT. Then the internal flow field and the variation of temperature and pressure in cylinder were recorded. Results show the flame front is a sphere centered at the spark point. The maximal pressure in power cylinder is 2.13Mpa and maximal pressure in charge cylinder is 0.235Mpa. The work done by power cylinder per cycle is 1.24J, while the charge cylinder consumes 0.22J per cycle.

This paper describes a piecewise linear control allocation method based on Computational Fluid Dynamics (CFD) aero-data for a blended wing body (BWB) aircraft with redundant control surfaces. The conventional control allocation methods usually assume that linear efficiency existence between the control surfaces deflection and the virtual control torque. But from the calculated CFD aero-data of the BWB aircraft, the characteristic of the elevons and split rudders to the control torque is nonlinear, which may bring control errors by using conventional linear methods. The piecewise linear approximate method is used to estimate the nonlinear control efficiency of surface deflection. In order to obtain the surface commands, a piecewise linear programing control allocation (PLPCA) scheme is applied by considering the constraints of the deflection position and rate. The simulation result shows that the PLPCA scheme can allocate the control surfaces reasonably and generate better virtual moment command than that of the linear programing control allocation (LPCA).

This paper investigates the influence of the hotel atrium design on energy consumption from an integrated perspective. The computer simulation techniques were used to assess the effects of the SC and passive energy-saving. The simulation results indicate that the effectively design air supply system can perform two major functions, separation and utilize natural air to help reduce refrigeration zone and cooling upper zone. The following case study demonstrates that the integrated method allows the hotel atrium to save energy and maintain comfort in summer season.

Full evacuation is a key concern for supertall buildings due to the high population density and long travel distance. Using the elevator would speed up evacuation, but there are fire safety concerns. A design of fire safe elevator system combining the refuge place with fire safe elevator is studied. In the proposed design, fire safe elevator is surrounded by the refuge places with at least 2 hours’ fire resistance rating. During the fire, the elevators would be controlled to stop only at the stories with refuge places. This arrangement can protect both the occupants and the elevators. Smoke spread to the system is studied by the Computational Fluid Dynamics (CFD) code Fire Dynamics Simulator (FDS). Different arrangements of smoke extraction with pressurization systems are evaluated by analyzing the smoke dispersion and pressure distributions in this fire safe elevator system.

Hot stamping is now the main forming process to produce the ultra-high strength components in an automotive body structure. Tooling in hot stamping has multiple cooling channels to maintain a lower temperature of the tooling. It is also important that the cooling channels are designed to ensure uniformity of the temperature distribution on the final part. This will stop part warpage. This paper will show the steps in analyzing a large tool, where the tool has been partitioned into sections. Moreover, suggestions will be made in how to balance the water flows in each section.

A 3-D Eulerian-Eulerian multiphase Computational Fluid Dynamics (CFD) model combined with Population Balance Modeling (PBM) were presented for two phase bubbly flow in vertical pipes. The discrete bubble sizes prescribed in the dispersed phase were tracked by solving an additional set of transport equations, which these equations were progressively coupled with the flow equations during the simulations. Important flow quantities such as local void fraction, liquid velocity and normal turbulent stresses were calculated and compared against experimental data from literature. Good agreement with the experimental data was obtained. It was found that void fraction profile exhibited a sharp peak near the wall. The liquid velocity profile was flattened by the presence of the vapor phase (i.e. the bubbles), and all three normal fluctuations were affected by the presence of the vapor phase. These fluctuations do not increase monotonically as the void fraction increases. Thus this CFD-PBM modeling can be used for prediction of wall peaking and coring phenomena, and radial void distribution.

We describe the implementation of the Smoothed Particle Hydrodynamics (SPH) method on graphical processing units (GPU) using the Compute Unified Device Architecture (CUDA) developed by NVIDIA. The entire algorithm is executed on the GPU, fully exploiting its computational power. The code vfaces all three main components of an SPH simulation: neighbor list constructions, force computation, integration of the equation of motion. The simulation speed achieved is one to two orders of magnitude higher than the equivalent CPU code. Applications are shown for simulating the paths of lava flows during volcano eruptions. Both static problems with purely thermal effects (such as lava lake solidification) and dynamic problems with a complete lava flow were simulated.

The influence of centrifugal accelerations on the particles in magnetorheological fluids due to high rotational speeds in brakes and clutches is often described with an undesirable increase of the off-state torque or an irreversible decomposition of the MRF when no magnetic field is applied. In this contribution this effect is studied by analyzing the flow fields caused by the rotary motion of the enclosed boundaries in radial and axial shear gaps from the fluid dynamics point of view. By an analytical approach for describing the particle behavior, changes in the particle distribution can be calculated. The approach is based on the simulation of several tracks of individual particles for different rotational speeds. The results of the simulation are compared with measurements performed on a test actuator for identifying a move of the particle concentration in radial shear gaps by measuring changes in magnetic flux density distribution.

Numerical flow simulations are an important part of the design and verification of measurement configurations. Three examples are presented: variable density flow, particle flow behind pipe junctions and turbulent buoyancy-driven flow. Potentially it can used for uncertainty estimations.