Cardiovascular disease remains the leading cause of death in Cardiovascular disease remains the leading cause of death in developed countries. After the introduction of stents in the 1980s mortality rates declined, yet those gains have since plateaued, signaling the need for a new generation of treatments that are safer and more effective. To achieve this goal, it is important to understand both the physical device-body interaction as well as the physiological changes induced by the device.
Computational tools are uniquely capable of accounting for cardiac/vascular tissue mechanics, blood flow, and the interaction between them, yet are currently under-utilized due to their complexity. The SIMULIA Living Heart Model (LHM), an anatomically and physiologically realistic 3D model of a human heart, provides a platform to better understand the human heart in healthy and diseased states as well as to improve the efficacy of cardiovascular medical devices and to guide the clinical treatment of heart disease. In this paper, we focus on the modeling of blood flow which encompasses a wide variety of conceptual and technical approaches. These range from 0D/1D lumped parameter models (LPMs) of the cardiovascular system to highly detailed 3D fluid-structure interaction (FSI) co-simulations.Using applications from medical device design and patient care, we discuss best practices in the context of the problem being modeled and the level of accuracy desired.
As the consciousness of energy saving and carbon reduction and comfortable environment is paid increasing attention to, the common objective of various countries with decreasing energy is to develop and popularize high efficiency and low running noise blowers. This study uses CFD to calculate the flow field and performance of a blower and compare with the experimental measurement.
The characteristic curve of blower shows that the simulated and experimental values are close to each other, the difference between the values is only 0.4%. This analysis result proofs the CFD package is a highly reliable tool for the future blower design improvement. In addition, this study discusses the noise distribution of blower flow field, the periodic pressure output value calculated by CFD is used in the sound source input of sound pressure field, so as to simulate and analyze the aerodynamic noise reading of the flow field around the blower. The result shows that the simulated value of flow field around the fan has as high as 80.5 dB(A) ~ 81.5 dB(A) noise level and is agree with measurement (82 dB(A)). The noise level is low but has a sharp noise. According to the numerical results, designer of the blower modify the tongue geometry and remove the sharp noise.
The paper is devoted to the mathematical modeling of the dynamics of geophysical flows on mountain slopes, e.g., rapid landslides, debris flows, avalanches, lava flows, etc. Such flows can be very dangerous for people and various objects. A brief description is given of models that have been used so far, as well as of new, more sophisticated, models, including those developed by the authors. In these new models, nonlinear rheological properties of the moving medium, entrainment of the underlying material, and the turbulence are taken into account. The results of test simulations of flows down long homogeneous slopes are presented, which demonstrate the influence of rheological properties, as well as of turbulence and mass entrainment, on the behavior of the flow.
Buildings are responsible for the significant amount of energy consumption and C02 emission. Obviously, façades are the most important building element considering energy consumption, environmental effects and user’s comfort. Therefore, different design strategies are being developed according to different climatic zones for sustainable, energy-efficient, high-performance buildings. Buildings are responsible for the significant amount of energy consumption and C02 emission.
Obviously, façades are the most important building element considering energy consumption, environmental effects and user’s comfort. Therefore, different design strategies are being developed according to different climatic zones for sustainable, energy-efficient, high-performance buildings. Today, different systems such as double-wall façades, ventilated windows, solar and green walls are already being used in building envelopes. The first priority of these systems is decreasing energy consumption by utilization of natural ventilation and solar energy. Such systems operate independently from the central HVAC systems; hence, do not reduce the installation cost of mechanical works. Moreover, their investment, operating, maintenance and cleaning costs are very high compared to conventional facade systems. Therefore, innovative and low-cost façade systems, which are responsible for less energy consumption, continue to be the subject of research. In this study, a newly developed façade system is discussed.
In the air conditioning sector, batteries are essential equipment. For this reason, they are included in almost every analysis. In many cases, we need accurate solutions to make changes on our HVAC unit design. CFD analysis can show us internal pressure loses and other air flow characteristics of an HVAC unit. During the design process, we make many changes on the unit design. At this point, CFD analysis provides us an economical solution for testing our preliminary designs before the final design. For this reason, we need to create the correct model for coils in our CFD analysis.
In CFD analysis meshing a coil's real geometry is a very expensive job. You have to create a very dense mesh between coil's lamellas. Creating a dense mesh extends the solution time and consumes too much system resources but it gives more accurate solutions. If you don't have enough system resources then you should try porous medium definition for the coil. For porous medium definition, neither a dense mesh nor a high system resource is necessary. In many cases, porous medium definition works well if you can define the coil's volume resistance correctly in three dimensions. Porous medium solutions are less accurate than real geometry solutions. Here we must make a decision between accuracy and resources. The third option is FlowVision's unique feature named "Gap Model" which provides the real geometry solutions without the need for dense meshing. Current study covers comparison of these three different coil definitions according to their positive and negative aspects.
CFD calculations of NREL Phase VI rotor under wide range of operation conditions were conducted using FlowVision software. Computations were performed for various wind speeds with axial inflow, constant RPM and constant blade pitch. The rotation of the blades was modeled via different approaches; steady-state with frozen rotor using rotating reference frame and transient with moving boundaries or sliding surfaces. In addition to this, an ‘Overlapping Boundary Layer (OBL)’ was implemented to resolve the boundary layer for a selected case. Turbulence models ‘k-ε-AKN and k-ω Shear Stress Transport (SST) were used and compared. Except the OBL case, FlowVision wall function approximation was employed for all calculations with y+ values between 30 and 100.
Overall results were compared for all of the above-mentioned numerical approaches and showed good agreement with the experimental data. k-ω SST turbulence model is found to perform better to predict stall onset. The stall occurrence and general torque trend as a function of wind speed is fairly well captured. Comparisons of the static pressure distribution around blades with experimental data at different span-wise sections for different wind speeds are presented and good agreement is observed.
In the present paper the simulation of the explosion of condensed explosives in the air. The method used simulation by specifying the scope of compressed gas as the point source of the explosion. Describes the behavior of the blast wave on the middle and far distances from the source of the explosion, in which a pressure profile does not depend on the geometry of the source. The paper proposed to develop a method scope of the compressed gas provides the account properties of the products of the explosion for any explosive composition. Numerical investigation of the explosion of an explosive charge in the open countryside, in the presence of walls and rigidly fixed in the model of the urban environment. Shown good agreement with the experimental results and the peak pulse pressure both direct and reflected waves in each of the above cases.
The paper studies the experience in application of CFD FlowVision software for analytical validation of sodium-cooled fast reactor structure components and the results of performed verification, namely:
- development and implementation of new model of turbulent heat transfer in liquid sodium (LMS) in FlowVision software and model verification based on thermohydraulic characteristics studied by experiment at TEFLU test facility;
- simulation of flowing and mixing of coolant with different temperatures in the upper mixing chamber of fast neutron reactor through the example of BN-600 (comparison with the results obtained at the operating reactor).
Based on the analysis of the results obtained, the efficiency of CFD codes application for the considered problems is shown, and the proposals for CFD codes verification development as applied to the advanced sodium-cooled fast reactor designs are stated.
In this paper, the modeling and simulation of the blood flow in the real patient heart is described. In order to cure the patients with cardio vascular disorder it is important to make appropriate choice of an artificial heart valve, it is important to exactly understand the behavior of the heart blood flow of the specific patient under treatment. The presented approach is based on the Magnetic Resonance Imaging/Tomography, which provides the necessary input to create the heart shape (“its geometry”) and its variation in time (tens or hundreds of frames) to define the internal time-dependent heart volumes for one heartbeat. Once this geometry is defined, the CFD software is applied to simulate the internal blood flow and further on visualize it to enable its further analysis. The applied CFD tool is FlowVision, due to its possibility to fully automatically perform the mesh generation of arbitrary shapes, as the heart geometry requires. In addition, FlowVision applies the dynamic mesh refinement by taking into account the motion of the heart-modeled surface, required by the CFD Euler model. The presented CFD approach to simulate the human internal blood flow is validated with data from MRI/MRT scans of the real heart and the respective simulation test cases are presented.
Cardiovascular disease is the leading cause of death in developed countries and continues to drive significant research aimed at improving diagnosis and treatment. In cases where therapeutic medical device intervention is warranted, it is important to account for device-heart interaction over both the short and long term. In the short term, cardiac motion can significantly impact device stability and performance (as in the case of artificial heart valves), while over the long term, modified blood flow patterns may lead to structural remodeling that can have adverse effects on cardiovascular function. Computational tools used for device design, sizing, and placement must therefore be able to account for cardiac/vascular tissue mechanics, blood flow, and the interaction between them. Moreover, such tools must allow for patient-specific modeling and provide interactive visualization capabilities that can support clinical decision-making and reduce operator error.
Blood flow velocity at different time points in the FSI simulation
In this paper, we describe a methodology for bidirectional fluid-structure interaction between the general purpose CFD code FlowVision and the SIMULIA Living Heart Human Model (LHHM), a dynamic, anatomically realistic, four-chamber heart model that considers the interplay and coupling of electrical and mechanical fields acting in concert to regulate the heart filling, ejection, and overall pump functions. The LHHM natively includes a 1D fluid network model capable of representing dynamic pressure/volume changes in the intra- and extra-cardiac circulation. In the current work, we first replace this network model with a full 3D blood model (solved in FlowVision) that provides detailed spatial and temporal resolution of cardiac hemodynamics driven by motions of the beating heart and constrained with appropriate time-varying boundary conditions derived from the literature. After validating this approach, we activate bidirectional coupling between the blood flow CFD model and the LHHM electromechanical model using the SIMULIA co-simulation engine and discuss modeling details and results of interest.
Hydroplaning is a major cause of wet-road accidents. The main contact element between the ground and vehicle is the tire. Tire safety and performance are therefore critically important. Wet roads present several uncontrollable factors. This paper uses CFD (Computational Fluid Dynamics) to analyze wet road hydroplaning effects. Fluid dynamics cannot be easily measured using normal experiments. Therefore the braking distance and record rolling vary by encoder. We propose another method to analysis it. By this result, the large groove and tire depth can reduce hydroplaning effects. A second method is modifying the tire void pattern which can reduce the hydroplaning extent by 29%.
The FDA (U.S. Food & Drug Administration) has partnered with academia and industry the Critical Path Initiative program to create a Guidance Document for industry-wide use proper validation and use of CFD models in the assessment of medical device safety.
CFD simulations are increasingly being used to determine flow patterns and fluid forces in order to evaluate blood-contacting medical devices. It is due to its potential to calculate the values of physical parameters that may affect the level of blood damage the device may cause, such as shear stress or dwell time. Although CFD can decrease the need for expensive prototyping and laboratory testing, there are no standardized and reliable methods available for using CFD techniques in this field.
The purpose of this project is to determine the limits of the applicability of CFD techniques by comparing some parameters (such as gauge pressure or shear stresses) of the computational simulations of a blood pump in several working conditions against suitable experimental models. The different conditions included a wide range of velocity profiles at the inlet or different rotor velocities.
FlowVision moving body capability, together with the real CAD geometry import, has allowed the numerical simulation of this complex case with a relatively simple mesh. Time-dependent results during a whole revolution of the rotor have been obtained, providing consistent and more realistic data for the different scenarios. As example, variables as the pressure gauge behave cyclic with a period of a 1⁄4 of the revolution time, which is consistent with the number of blades.