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FloEFD Validation Examples

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FloEFD Validation and Software Test Matrix

Before the release of each version of FloEFD a suite of 300 test cases are run through the different CAD embedded versions of the software

The test matrix ranges from simple 2D tests to industrial scale 3D benchmarks (see the following slides for a sample set of FloEFD validations)

The validation suite includes many classical CFD benchmark cases including a wide range of flow turbulence scenarios and regimes suitable for a General Purpose CFD code

The following slides illustrate some of the benchmarks each FloEFD release has to meet.


0

5

10

15

0 0.2 0.4 0.6 0.8 1

Y (mm)

X/LR

separationstreamlines,calculation

vortexcenter,calculation

Resistance

Velocity profiles

Recirculation zone

FloEFD Validation: Flow in 2D Channels with bilateral and unilateral expansions (Backward Facing Steps)

1

1Idelchik, I.E., Handbook of Hydraulic Resistance.2nd ed., McGraw Hill, New York, 1979

00.10.20.30.40.50.60.70.80.9

1

0.0 0.2 0.4 0.6 0.8 1.0

s

A0/A1

theoryEFD.Lab

1

2

2Yanshin, B.I.: Hydrodynamic Characteristics of Pipeline Valves and Elements. Convergen Sections, Divergent Sections and Valves. “Mashinostroenie”, Moscow, 1965

FloEFD


T VX VY Streamlines

Nusselt number vs. Rayleigh number

0123456789

10

1.E+03 1.E+04 1.E+05 1.E+06

Nuav

Ra

Refs.10,11

Ref.12

EFD.Lab

FloEFD Validation: Natural Convection in a Square Cavity

Dimensionless Velocities vs. Rayleigh Number

References10 Davis, G. De Vahl; Jones, I.P.: Natural Convection in a Square Cavity: a Comparison Exercise. Int. J. for Num. Meth. In Fluids, v.3, pp. 227-248 (1983)11 Emery, A., Chu, T.Y.: Heat Transfer across Vertical Layers. J. Heat Transfer, v. 87, p. 110 (1965)12 Denham, M.K., Patrick M.A.: Laminar Flow over a Downstream Facing Step in a Two-Dimensional Flow Channel. Trans. Instn. Chem. Engrs., v. 52, pp. 361-367 (1974)

FloEFD


FloEFD Validation: Couette Flow between Parallel Flat Plates at Re = 3.4 x 104

A classical plane flow is one between two parallel infinite flat plates spaced at a distance h from one another and moving at velocity U in opposite directions ,

Dimensionless velocity profiles for different meshes (10, 20, 40, 80 mesh cells across the channel) compare well with experimental data illustrating that with relatively coarse meshes good predictions can be expected when using FloEFD.

h

y

x

u(y)

U

-U

-1.0-0.8-0.6-0.4-0.20.00.20.40.60.81.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

u/U

y/(h/2)

experiment (Ref.9)FloEFD, 10 cellsFloEFD, 20 cellsFloEFD, 40 cellsFloEFD, 80 cells

References1. Schlichting, H. Boundary-Layer Theory. McGraw-Hill, New York, 1979.

1)


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 Re

Sh

0.1

1

10

100

1000

1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

ReD

NuD Calculation, steady-state

Calculation, time-dependent

Flow Trajectories over and past a Circular Cylinder at Re=41:Qualitative Comparison with Experiment (Ref 9)

Strouhal Number vs. Reynolds Number (Ref 4) Drag Coefficient vs. Reynolds Number (Ref 3)

Nusselt Number vs. Reynolds Number(Ref 6)

FloEFD Validation: Flow and Heat Transfer over a Circular Cylinder for Low Reynolds Numbers

References3. Panton, R.L., Incompressible Flow. 2nd ed., John Wiley & Sons, Inc., 19964. White, F.M., Fluid Mechanics. 3rd ed., McGraw-Hill, New York, 19946. Holman, J.P., Heat Transfer. 8th ed., McGraw-Hill, New York, 19979. Davis, G. De Vahl: Natural Convection of Air in a Square Cavity: a Bench Mark Numerical Solution. Int. J. for Num. Meth. In Fluids, v. 3, pp. 249-264 (1983)


FloEFD Validation: Unsteady Vortex Shedding Flow over a Circular Cylinder at Re=3.7x105

Mesh Density(cells per cylinder

diameter)

Deviation from experimental data

(%)

FloEFD, 20 cells per diameter 0.82 -18 650

FloEFD, 40 cells per diameter 0.95 -5 330

FloEFD, 80 cells per diameter 1.02 2 170

Experiment (Driver and Seegmiller 1985) 1.0 n/a n/a

dC maxy

Driver, D.M. and Seegmiller, H.L. (1985). Features of a Reattaching Turbulent Shear Layer in Divergent Channel Flow. AIAA Journal, Vol. 23, p. 163.

Predicted turbulent transient flow velocity fields over a circular cylinder calculated with FloEFDfor different computational meshes having:

a) 20 quad cells per diameter, b) 40 quad cells per diameter,c) 80 quad cells per diameter, &d) Similar real flow shadowgraph from

Driver and Seegmiller (1985)

Circular cylinder drag coefficients calculated with FloEFD in comparison with experimental data (Driver and Seegmiller1985).


Mach number distribution

Classical benchmark of air flow at inlet M=3 in a 2D (planar) convergent-divergent channel

FloEFD Validation: Supersonic Flow in a 2-D Convergent-Divergent Channel

ReferencePoint

1 2 3 4 5

X ordinate (m) 0.0042 0.047 0.1094 0.155 0.1648

Y ordinate (m) 0.0175 0.0157 0.026 0.026 0.0157

Mach Number (Theory)

3.000 2.427 1.957 2.089 2.365

Mach Number(FloEFD)

3.000 2.429 1.965 2.106 2.380

Difference (%) 0.0 0.1 0.4 0.8 0.6


FloEFD Validation: Smoothing step-shaped velocity profile by a porous screen of different drag coefficient ( ζ )

References2. Panton, R.L., Incompressible Flow. 2nd ed., John Wiley & Sons, Inc., 1996


Flow Streamlines: Smoke Visualisation, left (Ref 19), FloEFD result, right

43 / (Ref 14)

41 /

FloEFD Validation: Cooling a Pin-Fin Heat Sink Due to Natural Convection

References14. Enchao Yu, Yogendra Yoshi: Heat Transfer Enhancement from Enclosed Discrete Components using Pin-Fin Heat Sinks Int. J. of Heat & Mass Transfer, v. 45, pp. 4957-4966 (2002)19. Jyotsna, R., Vanka, S.P.: Multigrid Calculation of Steady, Viscous Flow in a Triangular Cavity. J. Comput. Phsy., v. 122, pp. 107-117 (1995)


Caviatition on a Hydrofoil (1); QuantitativeComparison

Cavitation Number,

Pressure Coefficient vs. Cavitation NumberCavitation Length vs. Cavitation Number


V=8 m/s, Chord length = 0.305 m

Angle of attack () – 3.5о

Cavitation number,

Caviatition on a Hydrofoil (2); QualitativeComparison

Reference

24. Wesley, H.B., Spyros, A.K.: Experimental & Computational Investigation of Sheet Cavitationon a Hydrofoil. Presented at 2nd Joint ASME/JSME Fluid Engineering Conference & ASME/EALA 6th

International Conference on Laser Anemometry. The Westin Resort, Hilton Head Island, SC, USA August 13-18, 1995


Component Mass Fraction, %

Fuel (Methane) 3.29

Oxidizer (Air) 96.71

0

400

800

1200

1600

0 0.2 0.4 0.6 0.8 1

R/D

Tem

pera

ture

(K)

CalculationExperimental measurement 1

Experimental measurement 2

0

400

800

1200

1600

0 0.2 0.4 0.6 0.8 1

R/D

Tem

pera

ture

(K)

Calculation Experimental measurement 1

Experimental measurement 2

Reference

27. Nandula, S.P., Pitz, R.W., Barlow, R.S., Fiechtner, G.J., Rayleigh/Raman/LIF Measurements in a Turbulent Lean Premixed Combustor” AIAA 96-0937, 34th Aerospace Sciences Meeting & Exhibit, Reno, NV, January 15-18, 1996

Combustion of a Premixed Methane/Air Mixture


FloEFD Validation: Flow in a 90o-bend of a 3D square duct

Velocity profiles at different cross sections in different longitudinal planes

AA1

AA1

Reference8. Van Dyke, Milton, An Album of Fluid Motion. The Parabolic Press, Stanford, California, 1982.


Hydraulic resistance coefficient Torque coefficient

Flow through a Cone Valve

Reference13. Yanshin, B.I.: Hydrodynamic Characteristics of Pipeline Valves and Elements.Convergent Sections, Divergent Sections, and Valves. “Mashinostroenie”, Moscow,1965.


-1-0.8-0.6-0.4-0.2

00.20.40.60.8

11.21.41.6

0 30 60 90 120 150 180

Ct, Cn

Attack angle, degree

Ct, experimetCt, EFD.LabCn, experimentCn, EFD.Lab

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0 30 60 90 120 150 180

mz

Attack angle (degree)

Experiment

Calculation

Aerodynamic drag coefficient vs. attack angleAerodynamic torque coefficient vs. attack angle

Supersonic air flow at incident M=1.3 over a segmental conic body at different attack angles in the 0…180° range.

Supersonic Flow over a Segmental Conic Body

Reference5. Artonkin, V.G., Petrov, K.P., Investigations of aerodynamic characteristics ofsegmental conic bodies. TsAGI Proceedings, No. 1361, Moscow, 1971 (in Russian).


Flow Around the Ahmed Car Body

Slant angle = 35°

0

100

200

300

400

500

600

700

800

-1600 -1400 -1200 -1000 -800 -600 -400 -200 0 200 400 600 800

x, mm

z, m

m

ReferenceLienhart, H., Stoots, C., Becker, S. Flow and turbulence structures in the wake of a

simplified car model (Ahmed model). DGLR Fach Symp. der AG STAB, Stuttgart University, 2000.

AhmedBody Slant Angle

AbsoluteDifference

% Difference

25° 0.298 0.284 -0.014 -4.8

35° 0.257 0.274 0.017 6.6


Injection of a particle into a uniform fluid flow field:

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 0.05 0.1 0.15 0.2 0.25

y, m

x, m

EFD.Lab

analytical solution

Re = 0.1

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.00 0.05 0.10 0.15 0.20 X, m

Vp = 1 m/s,analytical solutionVp = 1 m/s,EFD.LabVp = 2 m/s,analytical solutionVp = 2 m/s,EFD.LabVp = 3 m/s,analytical solutionVp = 3 m/s,EFD.Lab

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.00 0.03 0.06 0.09 0.12 0.15 X, m

EFD.Lab

Re = 105

Particle trajectory in the Y-direction gravity

Dispersed-phase flows (droplets and solid particles’ trajectories)

Reference18. Henderson, C.B. Drag Coefficients of Spheres in Continuum and Rarefied Flows.AIAA Journal, v.14, No.6, 1976.


Comparison of predicted and measured total pressure drop for a Stairmand HE cyclone

0

500

1000

1500

2000

2500

3000

0 5 10 15 20 25 30

U inlet, m/s

dP, P

a

ExperimentEFD calculations

Time evolution of the total pressure drop of a Stairmand HE cyclone at 10 m/s gas inlet velocity

0

100

200

300

400

0.3 0.7 1.1 1.5 1.9

Time, s

dP, P

a

Experiment

EFD calculation

Stairmand High Efficiency Gas Cyclone (Non-isotropic swirling Flows)

Reference Griffiths, W.D., Boysan, F., 1996, “Computational fluid dynamics (CFD) and empirical modellingof the performance of a number of cyclone samplers”, J. Aerosol Sci, Vol 27, №2, 281-304


Reference

Winklhofer, E., Kull, E., Kelz, E., and Morozov, A., 2001, “Comprehensive Hydraulic and Flow Field Documentation in Model Throttle Experiments Under Cavitation Conditions.” ILASS Europe 2001.

L=0.001 m, H=0.000299 m,

W=0.0003 m, Rin=0.00002 m

100 bar

33 bar

100 bar

100 bar

25 bar

15 bar

Mass flow rate through the injector versus pressure drop

0.004

0.005

0.006

0.007

0.008

0.009

20 30 40 50 60 70 80 90 100

(Pin - Pb), bar

G, k

g/s

calculationexperiment

Fuel Injector Cavitation

Inlet

Outlet

Nozzle Wall


Modified equilibrium combustion model approach in FloEFD:— Combustion starts upon mixing (no pre-mixing)— “Limited Combustion Rate” option when

premixed. Requires the separate simulation of an igniter to start the combustion simulation

FloEFD Validation: Vortex Combustor Benchmark

600

800

1000

1200

1400

1600

1800

2000

0 0.1 0.2 0.3 0.4 0.5 0.6

Position [m]

Tem

pera

ture

of F

luid

[K

]

X=0.027

ReferenceSayre A, N. Lallemant, J. Dugue, R. Weber, 1994, Scaling Characteristics of Aerodynamics and Low-NOx Properties of Industrial Natural Gas Burners, The Scaling 400 Study, Part IV: The 300 kW BERL Test Results, IFRF Doc No F40/y/11, The Netherlands.

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