Three-Dimensional Numerical Simulation of Non-Newtonian Blood in Two Coronary Stents

2010 ◽  
Author(s):  
F. Gori ◽  
A. Boghi
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Casson Fluid ◽  
Coronary Stents ◽  
Unsteady State ◽  
Cfd Simulations ◽  
3D Geometry ◽  
Time Variations ◽  
Rigid Walls ◽  
Newtonian Behavior

The objective of the present study is to carry out CFD simulations in a realistic 3D geometry of two coronary stents in physiological conditions and to assess the influence of the non-Newtonian behavior of blood, modeled as Casson fluid. The stents used are made of 12 rings and are similar to real coronary ones. Artery is modeled as a cylinder with rigid walls and the blood is assumed as incompressible non-Newtonian fluid in laminar flow. A commercial computational fluid dynamic code is used with a mesh composed of non uniform tetrahedrons. The simulations are performed in steady and unsteady state. Wall Shear Stress, as well as its time variations and the non-Newtonian behavior, are investigated in unsteady state. Results suggest that the Newtonian behavior is leading to an overestimation of the restenosis percent.

Design of a rotor blade tip for the investigation of dynamic stall in the transonic wind-tunnel Göttingen

2016 ◽  
Vol 120 (1232) ◽  
pp. 1509-1533 ◽  
Author(s):  
B. Lütke ◽  
J. Nuhn ◽  
Y. Govers ◽  
M. Schmidt
Keyword(s):  
Experimental Data ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Fe Model ◽  
Stress Distributions ◽  
Cfd Simulations ◽  
Blade Tip

ABSTRACTThe aerodynamic and structural design of a pitching blade tip with a double-swept planform is presented. The authors demonstrate how high-fidelity finite element (FE) and computational fluid dynamic (CFD) simulations are successfully used in the design phase. Eigenfrequencies, deformation, and stress distributions are evaluated by means of a three-dimensional (3D) FE model. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are compared to experimental data for a light dynamic stall case atMa= 0.5,Re= 1.2 × 106. The results show a very good agreement as long as the flow stays attached. Tendencies for the span-wise location of separation are captured. As soon as separation sets in, discrepancies between experimental and numerical data are observed. The experimental data show that for light dynamic stall cases atMa= 0.5, a factor of safety ofFoS= 2.0 is sufficient if the presented simulation methods are used.

Three-Dimensional Numerical Simulation of the Fluid Dynamics in a Coronary Stent

2009 ◽  
Author(s):  
F. Gori ◽  
A. Boghi ◽  
M. Amitrano
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Coronary Stent ◽  
Shear Stresses ◽  
Unsteady State ◽  
Hemodynamic Variables ◽  
Stent Geometry ◽  
Severe Coronary Artery ◽  
Wall Shear ◽  
Artery Disease

Stents are commonly used to restore blood flow in patients with severe coronary artery disease. Local hemodynamic variables, as wall shear stress, have an important role in the restenosis and their distribution depends on the stent geometry. The objective of the present study is to carry out CFD simulations in a realistic 3D geometry of a coronary stent in physiological conditions. A comparison is performed between two reconstructed stents, made of 12 rings and similar to the real coronary ones, which differ by the position of the struts, where the first type is with closed cells and the second one with open cells. The artery is modeled as a cylinder with rigid walls and the blood is assumed as incompressible Newtonian fluid in laminar flow with constant physical properties. The commercial computational fluid dynamic code FLUENT is used with a mesh composed of non uniform tetrahedrons. The simulations are performed in steady and unsteady state. Wall shear stresses, WSS, as well as its time variations, are investigated in unsteady state with the conclusion that the stent with closed cells have a better fluid dynamic behavior.

Fluid Dynamic Design and Optimization of Two Stage Centrifugal Fan for Industrial Burners

2011 ◽  
Author(s):  
C. Ferrari ◽  
M. Pinelli ◽  
P. R. Spina ◽  
P. Bolognin ◽  
L. Borghi
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Stage ◽  
Centrifugal Fan ◽  
Cfd Simulations ◽  
Two Stage ◽  
Dynamic Design ◽  
Design And Optimization ◽  
Preliminary Design Stage

In this paper, the fluid dynamic design of a two-stage centrifugal fan for industrial burner application is presented. The design is carried out by means of an integrated 1D/3D numerical procedure based on the use of CFD simulations. The CFD simulations are used either at the preliminary design stage to choose among competitive one- or two-dimensional geometries and then to test the generated three-dimensional geometries. The results show how the different design choices could impact on the performance parameters and, finally, how the analysis of the various alternatives allows the determination of the overall geometry of a complete and performing two-stage centrifugal fan.

Reducing the Effects of Blast to the Head Through Load Partitioning

2013 ◽  
Author(s):  
Mark A. Rapo ◽  
Tim Baumer ◽  
Philemon C. Chan ◽  
James F. MacKiewicz
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Field Tests ◽  
Navier Stokes ◽  
Head Acceleration ◽  
Cfd Simulations ◽  
Blast Overpressure ◽  
Head Protection ◽  
Size Standard

Warfighters who survive encounters with improvised explosive devices (IEDs) may incur mild traumatic brain injury (mTBI) due to blast overpressure effects. Since existing head injury criteria are mostly based on head kinematics, head acceleration is one key metric to be measured. A blast wave travels at supersonic speed with a very sharp peak overpressure rise followed by a rapid decay within a short duration. For the surface area that is covered by the helmet, the cushion/suspension subsystem is responsible for mitigating the blast effects on the head, while the exposed area of the head or face would receive a direct blast loading. Computational fluid dynamic (CFD) simulations of a blast on an upright warfighter show a significant reduction in peak force to the head when a helmet is worn. For a helmet with an attached eye-shield, the load to the head from a front blast can be reduced further. A field study was conducted to verify that the increased load partitioned away from face and to the helmet and cushioning system would result in decreased head acceleration. Blast field tests were conducted using 4 lbs. of cylindrical C4 charges at 92″ standoff. Head acceleration was measured using combinations of a free hanging mid-size standard ISO headform fitted with Team Wendy (TW) pads, an advanced combat helmet (ACH), and an eye-shield. Tests were performed with the blast hitting the front, side and back of the helmeted headform system. Headform accelerations ranging from 120–465g were recorded based on blast direction and the amount of head protection. To validate the three-dimensional Navier-Stokes’ based CFD simulations, a custom-designed blast overpressure bust (BOB) containing 22 surface pressure sensors was mounted on top of the BTD to measure the pressure distribution over the head and face when exposed to a blast. The incident overpressure of the blast was 0.25MPa, with reflected pressures reaching 1.0MPa.

A Study on Utilization of Three-Dimensional Sensor Lip Image for Developing a Pronunciation Recognition System

2019 ◽  
Vol 63 (5) ◽  
pp. 50402-1-50402-9 ◽  
Author(s):  
Ing-Jr Ding ◽  
Chong-Min Ruan
Keyword(s):  
Principal Component Analysis ◽  
Automatic Speech Recognition ◽  
Feature Fusion ◽  
Three Dimensional ◽  
Principal Component ◽  
Recognition System ◽  
Geometrical Characteristics ◽  
3D Geometry ◽  
Different Types ◽  
The Disabled

Abstract The acoustic-based automatic speech recognition (ASR) technique has been a matured technique and widely seen to be used in numerous applications. However, acoustic-based ASR will not maintain a standard performance for the disabled group with an abnormal face, that is atypical eye or mouth geometrical characteristics. For governing this problem, this article develops a three-dimensional (3D) sensor lip image based pronunciation recognition system where the 3D sensor is efficiently used to acquire the action variations of the lip shapes of the pronunciation action from a speaker. In this work, two different types of 3D lip features for pronunciation recognition are presented, 3D-(x, y, z) coordinate lip feature and 3D geometry lip feature parameters. For the 3D-(x, y, z) coordinate lip feature design, 18 location points, each of which has 3D-sized coordinates, around the outer and inner lips are properly defined. In the design of 3D geometry lip features, eight types of features considering the geometrical space characteristics of the inner lip are developed. In addition, feature fusion to combine both 3D-(x, y, z) coordinate and 3D geometry lip features is further considered. The presented 3D sensor lip image based feature evaluated the performance and effectiveness using the principal component analysis based classification calculation approach. Experimental results on pronunciation recognition of two different datasets, Mandarin syllables and Mandarin phrases, demonstrate the competitive performance of the presented 3D sensor lip image based pronunciation recognition system.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

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