scholarly journals The Numerical Diffusion Effect on the CFD Simulation Accuracy of Velocity and Temperature Field for the Application of Sustainable Architecture Methodology

2020 ◽  
Vol 12 (23) ◽  
pp. 10173
Author(s):  
Vladimíra Michalcová ◽  
Kamila Kotrasová
Keyword(s):  
Temperature Field ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Flow ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Simulation Accuracy ◽  
Numerical Diffusion ◽  
Diffusion Temperature

Numerical simulation of fluid flow and heat or mass transfer phenomenon requires numerical solution of Navier–Stokes and energy-conservation equations, together with the continuity equation. The basic problem of solving general transport equations by the Finite Volume Method (FVM) is the exact calculation of the transport quantity. Numerical or false diffusion is a phenomenon of inserting errors in calculations that threaten the accuracy of the computational solution. The paper compares the physical accuracy of the calculation in the Computational Fluid Dynamics (CFD) code in Ansys Fluent using the offered discretization calculation schemes, methods of solving the gradients of the transport quantity on the cell walls, and the influence of the mesh type. The paper offers possibilities on how to reduce numerical errors. In the calculation area, the sharp boundary of two areas with different temperatures is created in the flow direction. The three-dimensional (3D) stationary flow of the fictitious gas is simulated using FVM so that only advective transfer, in terms of momentum and heat, arises. The subject of the study is to determine the level of numerical diffusion (temperature field scattering) and to evaluate the values of the transport quantity (temperature), which are outside the range of specified boundary conditions at variously set calculation parameters.

Experimental and Numerical Analysis of a Motorcycle Air Intake System Aerodynamics and Performance

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
M. A. Abd Halim ◽  
N. A. R. Nik Mohd ◽  
M. N. Mohd Nasir ◽  
M. N. Dahalan
Keyword(s):  
Combustion Process ◽  
Three Dimensional ◽  
Engine Performance ◽  
Internal Flow ◽  
Rapid Expansion ◽  
Navier Stokes ◽  
Turbulent Fluctuation ◽  
Ansys Fluent ◽  
Induction System ◽  
Acceleration And Deceleration

Induction system or also known as the breathing system is a sub-component of the internal combustion system that supplies clean air for the combustion process. A good design of the induction system would be able to supply the air with adequate pressure, temperature and density for the combustion process to optimizing the engine performance. The induction system has an internal flow problem with a geometry that has rapid expansion or diverging and converging sections that may lead to sudden acceleration and deceleration of flow, flow separation and cause excessive turbulent fluctuation in the system. The aerodynamic performance of these induction systems influences the pressure drop effect and thus the engine performance. Therefore, in this work, the aerodynamics of motorcycle induction systems is to be investigated for a range of Cubic Feet per Minute (CFM). A three-dimensional simulation of the flow inside a generic 4-stroke motorcycle airbox were done using Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) solver in ANSYS Fluent version 11. The simulation results are validated by an experimental study performed using a flow bench. The study shows that the difference of the validation is 1.54% in average at the total pressure outlet. A potential improvement to the system have been observed and can be done to suit motorsports applications.

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.

scholarly journals The study of the numerical diffusion in computational calculation

2020 ◽  
Vol 310 ◽  
pp. 00039
Author(s):  
Kamila Kotrasova ◽  
Vladimira Michalcova
Keyword(s):  
Heat Transfer ◽  
Differential Equation ◽  
Numerical Simulation ◽  
Continuity Equation ◽  
Cfd Simulation ◽  
Flow Process ◽  
Ansys Fluent ◽  
Numerical Diffusion ◽  
Mesh Density ◽  
Computational Calculation

The numerical simulation of flow process and heat transfer phenomena demands the solution of continuous differential equation and energy-conservation equations coupled with the continuity equation. The choosing of computation parameters in numerical simulation of computation domain have influence on accuracy of obtained results. The choose parameters, as mesh density, mesh type and computation procedures, for the numerical diffusion of computation domain were analysed and compared. The CFD simulation in ANSYS – Fluent was used for numerical simulation of 3D stational temperature flow of the computation domain.

The Impact of Gas Modeling in the Numerical Analysis of a Multistage Gas Turbine

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Massimiliano Maritano ◽  
Stefano Cecchi
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Ratio Distribution ◽  
Real Gas ◽  
Turbine Performance ◽  
Wall Boundary Conditions ◽  
Heavy Duty Gas Turbine ◽  
The Impact

In this work a numerical investigation of a four stage heavy-duty gas turbine is presented. Fully three-dimensional, multistage, Navier-Stokes analyses are carried out to predict the overall turbine performance. Coolant injections, cavity purge flows, and leakage flows are included in the turbine modeling by means of suitable wall boundary conditions. The main objective is the evaluation of the impact of gas modeling on the prediction of the stage and turbine performance parameters. To this end, four different gas models were used: three models are based on the perfect gas assumption with different values of constant cp, and the fourth is a real gas model which accounts for thermodynamic gas properties variations with temperature and mean fuel∕air ratio distribution in the through-flow direction. For the real gas computations, a numerical model is used which is based on the use of gas property tables, and exploits a local fitting of gas data to compute thermodynamic properties. Experimental measurements are available for comparison purposes in terms of static pressure values at the inlet∕outlet of each row and total temperature at the turbine exit.

Numerical simulations of three-dimensional plunging breaking waves: generation and evolution of aerated vortex filaments

2015 ◽  
Vol 767 ◽  
pp. 364-393 ◽  
Author(s):  
P. Lubin ◽  
S. Glockner
Keyword(s):  
Stokes Equations ◽  
Early Stage ◽  
Flow Direction ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Vortex Filaments ◽  
Navier Stokes Equations ◽  
Main Flow Direction

AbstractThe scope of this work is to present and discuss the results obtained from simulating three-dimensional plunging breaking waves by solving the Navier–Stokes equations, in air and water. Recent progress in computational capabilities has allowed us to run fine three-dimensional simulations, giving us the opportunity to study for the first time fine vortex filaments generated during the early stage of the wave breaking phenomenon. To date, no experimental observations have been made in laboratories, and these structures have only been visualised in rare documentary footage (e.g. BBC 2009 South Pacific. Available on YouTube, 7BOhDaJH0m4). These fine coherent structures are three-dimensional streamwise vortical tubes, like vortex filaments, connecting the splash-up and the main tube of air, elongated in the main flow direction. The first part of the paper is devoted to the presentation of the model and numerical methods. The air entrainment occurring when waves break is then carefully described. Thanks to the high resolution of the grid, these fine elongated structures are simulated and explained.

Analyzes of Film Cooling Effectiveness from Cylindrical and Staggered Compound Cooling Holes with Alignment Angle of 30 Degree at the End of Combustor

2014 ◽  
Vol 695 ◽  
pp. 389-392
Author(s):  
Shahin Salimi ◽  
Nor Azwadi Che Sidik ◽  
Leila Jahanshaloo ◽  
Kianpour Ehsan
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Ansys Fluent ◽  
Cooling Effectiveness ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Alignment Angle ◽  
Compound Angle

A numerical simulation has been performed for the investigation of flow and heat transfer characteristics of a film cooling injected through a hole with cylindrical and compound angle orientation. This paper presents the effects of coolant injector configuration of cylindrical and compound cooling holes with alignment angle of 30 degree at blowing ratio, BR = 3.18 on the film cooling effectiveness near the end wall surface of a combustor simulator. In the current research a three dimensional representation of Pratt and Whitney gas turbine engine was simulated and analyzed with a commercial finite volume package ANSYS FLUENT 14.0. This study has been performed with Reynolds-averaged Navier-Stokes turbulence model (RANS) on internal cooling passages The results indicate that using compound angle cooling holes injection, give much better protection than that obtained when simple angle cooling holes were used.

Enhanced understanding of leakage in mechanical seals with elliptical dimples based on CFD simulation

2019 ◽  
Vol 72 (1) ◽  
pp. 24-30
Author(s):  
Sen Jiang ◽  
Hua Ji ◽  
Tianhao Wang ◽  
Donglin Feng ◽  
Qian Li
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Leakage Rate ◽  
Geometric Feature ◽  
Maximum Pressure ◽  
Mechanical Seals ◽  
Ansys Fluent ◽  
Content Type ◽  
Surface Textures ◽  
Influencing Mechanism

Purpose The shapes of surface textures have been designed to control the leakage of mechanical seals in recent years. The purpose of this paper is to demonstrate the influence of geometric properties of elliptical dimples on the leakage rate. Design/methodology/approach A new geometric feature point is expressed using an analytical solution to locate the high-pressure zones. Furthermore, a numerical model of the three-dimensional flow field for the mechanical seal with elliptical dimples is developed using ANSYS Fluent to demonstrate the influencing mechanism. Findings The location of the proposed geometric converging point coincides with the maximum pressure point under different orientation angles. An inward flow on the leakage section observed from the simulation results is responsible for decreasing the leakage rate. Originality/value The influencing mechanism of the elliptical dimple on the leakage rate is demonstrated, which can facilitate the design of surface textures.

Evaluation of numerical diffusion of the finite volume method when modelling surface waves

2019 ◽  
pp. 106-119
Author(s):  
Елена Сергеевна Тятюшкина ◽  
Андрей Сергеевич Козелков ◽  
Андрей Александрович Куркин ◽  
Вадим Викторович Курулин ◽  
Валентин Робертович Ефремов ◽  
...  
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Calculation Method ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Diffusion ◽  
Volume Method

Обсуждается применение метода конечных объемов при решении уравнений Навье-Стокса для моделирования поверхностных волн. Сформулирована задача о распространении поверхностных волн, которая используется для оценки численной диффузии в решении уравнений Навье-Стокса. Предлагается методика оценки численной диффузии, выражаемой коэффициентом уменьшения амплитуды волны при прохождении ею одной своей длины (коэффициентом затухания). Дана оценка размеров сетки и шага по времени, выраженных в безразмерных величинах относительно параметров волны, необходимых для обеспечения приемлемого значения коэффициента затухания. Показана степень влияния каждого из сеточных параметров на увеличение коэффициента затухания. The application of numerical simulation methods based on the solution of the full three-dimensional Navier-Stokes equations for modelling of wave propagation on the water surface requires the construction of a grid model containing countable nodes throughout the entire volume of water medium. Insufficient grid resolution leads to insufficient detailing of the fields of velocity and pressure, as well as volume fraction of the liquid, which increases the numerical diffusion of the method and, ultimately, leads to an underestimation of oscillation amplitudes of the medium. A large time step also results in a “blurring” of the solution and significantly reduces its stability, especially when using the schemes which compress the front of the media interface. This paper presents the results of an assessment of acceptable grid sizes and time steps expressed in dimensionless parameters with respect to the wave parameters necessary to ensure accuracy of the solution sufficient for geophysical applications. The estimate is given for the method of calculating three-dimensional multiphase flows with a free surface based on solving the Navier-Stokes equations in a one-velocity approximation based on a completely implicit connection between velocity and pressure using the finite volume method. The finite volume method for the numerical solution of the Navier-Stokes equations is implemented for use on arbitrary unstructured grids. The methodology for estimation of numerical diffusion of the calculation method is proposed. This estimation is expressed as a percentage of the wave amplitude decrease at the distance equal to the one wavelength. In turn the methodology is based on the parameters entered to estimate the acceptable grid sizes and time step for the calculation method. Based on the described methodology, the results of the estimation of the grid resolution in the horizontal and vertical directions, the estimation of the time step, and the evaluation of the influence of the discretization scheme of the convective term are presented.

Simulation Study on the Performance of Vertical Axis Wind Turbine

2013 ◽  
Vol 465-466 ◽  
pp. 270-274 ◽  
Author(s):  
N. Afzanizam Samiran ◽  
A.A. Wahab ◽  
Mohd Sofian ◽  
N. Rosly
Keyword(s):  
Output Power ◽  
Flow Characteristic ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Savonius Rotor ◽  
Torque Coefficient

The present study considered the design improvement of Savonius rotor, in order to increase the efficiency of output power. An investigation was conducted to study the effect of geometrical configuration on the performance of the rotor in terms of coefficient of torque, coefficient of power and power output. Modification of conventional geometry has been designed by combining the effect of number of blades and shielding method. CFD simulation was conducted to analyze the flow characteristic and calculate the torque coefficient of all the rotor configurations. The continuity and Reynolds Averaged Navier-Stokes (RANS) equations and realizable k-ε epsilon turbulence model are numerically solved by commercial software Ansys-Fluent 14.0. The results obtained by transient and steady method for the conventional two bladed Savonius rotor are in agreement with those obtained experimentally by other authors and this indicates that the methods can be successfully applied for such analysis. The modified 3 and 4 bladed rotors with hybrid shielding method gave the highest maximum power coefficient which 0.37 at TSR 0.5 and output power exceed 4 watts with rotor dimensions of 0.2m width and 0.2m height. This blade configuration also is the best configuration by several percentages compared to the other model from the previous study

Stress analyses of various curvature arched groundsills

2020 ◽  
Author(s):  
Yu-Jen Hou ◽  
Hung-Pin Huang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Structural Analysis ◽  
Water Conservation ◽  
Maximum Stress ◽  
Flow Direction ◽  
Three Dimensional ◽  
Analysis Software ◽  
Ansys Fluent ◽  
Soil And Water

<p>In Taiwan, arched groundsill is frequently used as soil-and-water conservation structures for stabilizing creek bed, guiding flow direction, decreasing the slope of creek bed and reducing the scour effect. Even though much more arched grounsill was built in wild creek recently, its mechanical mechanism is still unclear.</p><p>In order to explore the characteristics of arched groundsill, this study intends to find out the scale of stress, moment and displacement distribution on the various curvature arched groundsills by means of the structural analysis software, ABAQUS. Simultaneously, the three-dimensional computational fluid dynamics software, ANSYS-FLUENT, is applied to show the flow condition of different setups. Preliminary result shows that the maximum stress and displacement of arched groundsill increase with curvature. The maximum moment decreases slightly firstly and increases sharply later with curvature.</p>

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