Study on Three-Dimensional Wind Field Characteristics of Thunderstorm Microbursts Using Computational Fluid Dynamics

2011 ◽  
Vol 243-249 ◽  
pp. 5033-5036
Author(s):  
Bai Feng Ji ◽  
Wei Lian Qu ◽  
Yan Li ◽  
Yi Fei Wang ◽  
Zhong Shan He
Keyword(s):  
Wind Field ◽  
Computational Simulation ◽  
Three Dimensional ◽  
Simulation Method ◽  
Computational Method ◽  
Navier Stokes ◽  
Transmission Tower ◽  
Lower Altitude ◽  
Structural Failures ◽  
Wind Distribution

Thunderstorm microbursts, which are sources of extreme wind loadings in nature, have caused numerous structural failures, especially collapses of transmission tower around the world. It is important to study wind field characteristics of thunderstorm microbusts from the perspective of wind-resistant design. In this paper, the three-dimensional wind field characteristics of thunderstorm microbursts were studied using computational simulation method. Firstly, the three-dimensional wind field of microburst was computational simulated using time-filtered Reynolds Averaged Navier-Stokes (RANS) numerical computational method. Then, the three-dimensional wind field characteristics including the wind distribution of wind velocity at different heights, the wind contours at lower altitude positions were studied in detail. The results indicate that the three-dimensional wind field of microbursts winds presents quite different characteristics at different heights and radial positions.

Transient Simulation of a Three-Dimensional Moving Downburst

2012 ◽  
Vol 446-449 ◽  
pp. 3875-3878
Author(s):  
Bai Feng Ji ◽  
Wei Lian Qu
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Wind Field ◽  
Three Dimensional ◽  
Simulation Method ◽  
Transient Simulation ◽  
Dynamics Simulation ◽  
Transmission Tower ◽  
Transient Wind

Thunderstorm microbursts, which are sources of extreme wind loadings in nature, have caused numerous structural failures, especially collapses of transmission tower around the world. Numerical simulation using computational fluid dynamics (CFD) has recently made significant progress in simulating downbursts. In this paper, transient simulation of a three-dimensional moving downburst was studied using computational fluid dynamics simulation method. Transient simulation of a three-dimensional moving downburst was conducted using time-filtered Reynolds Averaged Navier-Stokes (RANS) numerical simulation method. The three-dimensional transient wind field characteristics in a moving downburst were studied in detail. The results indicate that transient wind field characteristics in a moving downburst present quite different characteristics compared with stationary downburst at different heights and radial positions.

Experimental Measurements and Computational Solutions for Aerodynamic Forces on an Ahmed Body at Various Ground Clearances

2003 ◽  
Author(s):  
Ilhan Bayraktar ◽  
Drew Landman ◽  
Tuba Bayraktar
Keyword(s):  
Large Scale ◽  
Bluff Body ◽  
Ground Plane ◽  
Computational Simulation ◽  
Simulation Method ◽  
Full Scale ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Ground Clearance ◽  
Ahmed Body

Reliable computer solutions to external aerodynamic flow fields on road vehicles are extremely desirable to road vehicle designers. In a previous publication a study was performed to validate a Reynolds-averaged unsteady Navier-stokes solution for the aerodynamic characterization of a large-scale bluff body. In the present study, the external aerodynamics of this body as a function of ground clearance are explored. Experimental force measurements are obtained in a full-scale wind tunnel using an Ahmed body model and test conditions representative of full-scale operating conditions. A Reynolds averaged Navier-Stokes solver is employed for computational simulation of the external flowfield at the same conditions. Experimental and computational force coefficients versus vehicle ground clearance are presented for fixed ground, moving ground, and suction slot road simulations. Experimental results using boundary layer suction are compared to computational results with a moving ground plane in order to better understand the effect of a road simulation method.

scholarly journals Simulation of 3D-Unsteady Stator/Rotor Interaction in Turbomachinery Stages of Arbitrary Pitch Ratio

1996 ◽  
Author(s):  
Alexander R. Jung ◽  
Jürgen F. Mayer ◽  
Heinz Stetter
Keyword(s):  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Solution Process ◽  
Computational Method ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Time Stepping ◽  
Flow Phenomena ◽  
Pitch Ratio

This paper presents a computational method for the calculation of unsteady three-dimensional viscous flow in turbo-machinery stages. The method is based on a Finite-Volume Navier-Stokes solver for structured grids in a multiblock topology. The meshes at the stator/rotor interface are overlapped by two grid cells. An implicit residual smoothing method applicable to global time-stepping is used to accelerate the solution process. The problem of periodic boundary treatment for unequal pitches is handled using a method of time-inclined computational domains for three dimensions. The method applies a time transformation to the stator domain and to the rotor domain and uses different time-steps in the two domains. The results of a numerical simulation of the flow in a transonic turbine stage with a pitch ratio of 1.364 are presented. The time-averaged solution is compared to experimental data and satisfactory agreement is stated. Complex 3D-unsteady flow phenomena (shock motion, vortex shedding) are observed. Unsteady blade pressure fluctuations at various positions in spanwise direction are shown and the fluctuations are found to vary considerably along span. Instantaneous distributions of static pressure, Mach number, and entropy are presented.

Aerodynamic Design of Turbomachinery Blading in Three-Dimensional Flow: An Application to Radial Inflow Turbines

1993 ◽  
Vol 115 (3) ◽  
pp. 602-613 ◽  
Author(s):  
Y. L. Yang ◽  
C. S. Tan ◽  
W. R. Hawthorne
Keyword(s):  
Parametric Design ◽  
Design Method ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Turbine Rotor ◽  
Computational Method ◽  
Navier Stokes ◽  
Design Calculation ◽  
Analysis Tool ◽  
Turbine Wheel

A computational method based on a theory for turbomachinery blading design in three-dimensional inviscid flow is applied to a parametric design study of a radial inflow turbine wheel. As the method requires the specification of swirl distribution, a technique for its smooth generation within the blade region is proposed. Excellent agreements have been obtained between the computed results from this design method and those from direct Euler computations, demonstrating the correspondence and consistency between the two. The computed results indicate the sensitivity of the pressure distribution to a lean in the stacking axis and a minor alteration in the hub/shroud profiles. Analysis based on a Navier–Stokes solver shows no breakdown of flow within the designed blade passage and agreement with that from a design calculation; thus the flow in the designed turbine rotor closely approximates that of an inviscid one. These calculations illustrate the use of a design method coupled to an analysis tool for establishing guidelines and criteria for designing turbomachinery blading.

Flow Studies in Canine Artery Bifurcations Using a Numerical Simulation Method

1992 ◽  
Vol 114 (4) ◽  
pp. 504-511 ◽  
Author(s):  
X. Y. Xu ◽  
M. W. Collins ◽  
C. J. H. Jones
Keyword(s):  
Newtonian Fluid ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Simulation Method ◽  
Velocity Profiles ◽  
Navier Stokes ◽  
Element Mesh ◽  
Finite Volume Approach

Three-dimensional flows through canine femoral bifurcation models were predicted under physiological flow conditions by solving numerically the time-dependent threedimensional Navier-stokes equations. In the calculations, two models were assumed for the blood, those of (a) a Newtonian fluid, and (b) a non-Newtonian fluid obeying the power law. The blood vessel wall was assumed to be rigid this being the only approximation to the prediction model. The numerical procedure utilized a finite volume approach on a finite element mesh to discretize the equations, and the code used (ASTEC) incorporated the SIMPLE velocity-pressure algorithm in performing the calculations. The predicted velocity profiles were in good qualitative agreement with the in vivo measurements recently obtained by Jones et al. [1]. The non-Newtonian effects on the bifurcation flow field were also investigated, and no great differences in velocity profiles were observed. This indicated that the non-Newtonian characteristics of the blood might not be an important factor in determining the general flow patterns for these bifurcations, but could have local significance. Current work involves modeling wall distensibility in an empirically valid manner. Predictions accommodating these will permit a true quantitative comparison with experiment.

Numerical Simulation of Steady Liquid-Metal Flow in the Presence of a Static Magnetic Field

2004 ◽  
Vol 71 (6) ◽  
pp. 786-795 ◽  
Author(s):  
Amnon J. Meir ◽  
Paul G. Schmidt ◽  
Sayavur I. Bakhtiyarov ◽  
Ruel A. Overfelt
Keyword(s):  
Magnetic Field ◽  
Liquid Metal ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Metal Flow ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Dissipative Heat ◽  
Novel Approach ◽  
Liquid Metal Flow

We describe a novel approach to the mathematical modeling and computational simulation of fully three-dimensional, electromagnetically and thermally driven, steady liquid-metal flow. The phenomenon is governed by the Navier-Stokes equations, Maxwell’s equations, Ohm’s law, and the heat equation, all nonlinearly coupled via Lorentz and electromotive forces, buoyancy forces, and convective and dissipative heat transfer. Employing the electric current density rather than the magnetic field as the primary electromagnetic variable, it is possible to avoid artificial or highly idealized boundary conditions for electric and magnetic fields and to account exactly for the electromagnetic interaction of the fluid with the surrounding media. A finite element method based on this approach was used to simulate the flow of a metallic melt in a cylindrical container, rotating steadily in a uniform magnetic field perpendicular to the cylinder axis. Velocity, pressure, current, and potential distributions were computed and compared to theoretical predictions.

scholarly journals Computational Simulation of Fully Trimmed Flight of a Helicopter in Hover

2019 ◽  
Vol 26 (1) ◽  
pp. 175-181
Author(s):  
Wieńczysław Stalewski ◽  
Wiesław Zalewski ◽  
Katarzyna Surmacz ◽  
Maximilian Pulfer ◽  
Frieder Hirsch
Keyword(s):  
Computational Models ◽  
Computational Simulation ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Precise Adjustment ◽  
Flight Controls ◽  
Independent Parameters ◽  
Geometry And Kinematics

Abstract In trimmed flight of a helicopter, all the forces and moments, aerodynamic, inertial, and gravitational, are in balance. Keeping the helicopter in trimmed state, needs a precise adjustment of flight controls. The methodology of simulation of a fully trimmed flight of rotorcraft has been developed and applied to simulate hover of a helicopter. The presented approach is based on a solution of Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. In contrast to typical solutions of such problem, in the newly developed methodology, the flight controls corresponding to the trimmed-flight conditions are also determined based on the solution of URANS equations. The methodology is based on coupling of several computational models of Computational Fluid Dynamics and Flight Dynamic. The URANS equations are solved in a three-dimensional region surrounding the flying helicopter, using the ANSYS FLUENT code. The approach is truly three-dimensional, with truly modelled geometry and kinematics of main and tail rotor blades. This applies to modelling of blade flapping and lead-lag motion, too. The trimming procedure uses six independent parameters (i.e. collective and cyclic pitch of main rotor blades, collective pitch of tail rotor blades, pitch, and bank angles of a helicopter) that should be adjusted so as to balance all forces and moments acting on the helicopter. The detailed description of the developed methodology as well as the results of simulation of trimmed hover of the helicopter was presented.

Aerodynamic Design of Turbomachinery Blading in Three-Dimensional Flow: An Application to Radial Inflow Turbines

1992 ◽  
Author(s):  
Y. L. Yang ◽  
C. S. Tan ◽  
W. R. Hawthorne
Keyword(s):  
Parametric Design ◽  
Design Method ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Turbine Rotor ◽  
Computational Method ◽  
Navier Stokes ◽  
Design Calculation ◽  
Analysis Tool ◽  
Turbine Wheel

A computational method, based on a theory for turbomachinery blading design in three-dimensional inviscid flow, is applied to a parametric design study of a radial inflow turbine wheel. As the method requires the specification of swirl distribution, a technique for its smooth generation within the blade region is proposed. Excellent agreements have been obtained between the computed results from this design method and those from direct Euler computations, demonstrating the correspondence and consistency between the two. The computed results indicate the sensitivity of the pressure distribution to a lean in the stacking axis and a minor alteration in the hub/shroud profiles. Analysis based on Navier-Stokes solver shows no breakdown of flow within the designed blade passage and agreement with that from design calculation; thus the flow in the designed turbine rotor closely approximates that of an inviscid one. These calculations illustrates the use of a design method coupled to an analysis tool for establishing guidelines and criteria for designing turbomachinery blading.

Viscous Simulation Method for Unsteady Flows Past Multicomponent Configurations

1992 ◽  
Vol 114 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Kamran Fouladi ◽  
Oktay Baysal
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Simulation Method ◽  
Parent Body ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Navier Stokes Equations ◽  
Time Period ◽  
Cavity Opening ◽  
Averaging Time

An algorithm is developed to obtain numerical simulations of flows about complex configurations composed of multiple and nonsimilar components with arbitrary geometries. The algorithm uses a hybridization of the domain decomposition techniques for grid generation and to reduce the computer memory requirement. Three-dimensional Reynolds-averaged, unsteady, compressible, and full Navier-Stokes equations are solved on each of the subdomains by a fully vectorized, finite-volume, upwind-biased, approximately factored, and multigrid method. The effect of Reynolds stresses is incorporated through an algebraic turbulence model with several modifications for interference flows. The algorithm is applied to simulate supersonic flows past an ogive-nose-cylinder near or inside a cavity. The cylinder is attached to an offset L-shaped sting when placed above the cavity opening. The unsteady nature of these flowfields and the interaction of the cavity shear layer with the cylinder are simulated. These cases illustrate two significantly different and important interference characteristics for an internally carried store separating from its parent body. Unsteadiness of the cavity flow has a more pronounced effect on the normal forces acting on the cylinder when the cylinder is placed inside the cavity. The time averaged surface pressures compare favorably with the wind tunnel data, despite the averaging time period for the computations being three orders of magnitude smaller than that of the experimental measurements.

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