SilverP:Quality Review AC1-08

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L1T2 3 element airfoil

Application Challenge 1-08 © copyright ERCOFTAC 2004

Application Challenge (AC) Title: The L1T2 multi element airfoil

AC Author and Thematic Area: CFS Engineering and DERA (partners 5 and 6)

Reviewer (Name/Organisation) : Bonnet, University of Poitiers

1

TOP LEVEL CHECK

YES

NO

CO

1.1

Is this AC an Industrial test case for judging CFD competency?

X

1.2

Are the design/assessment parameters (DOAPs) defined?

X

1.3

Have these assessment parameters been measured?

X

1.4

Are CFD calculations available ?

X

H

M

L

1.5

Importance of AC to Industrial Sector (IS)?

X

Comments:

The external turbulence level appears to be high (6.8%) and should be probably taken into account for CFD (this point has to be clarified from the value of 1.068 given as the turbulence factor by Moir).

The data are limited to mean values, without any turbulent results and no velocity vectors provided. The analysis of the CFD results are limited to mean characteristics; for example, the effects of the physical models cannot be directly stated.

The presence in the experiments of a short laminar

bubble must be kept in mind while comparing CFD to experiments

Please identify Underlying Flow Regimes for this AC:

Flow around airfoils and blades. Wake/boundary layer interaction. Flow separation. Drag. Wakes. Laminar/turbulent transition. Boundary layers under various pressure gradients. Boundary layer under influence of free-stream turbulence.

DETAILED CHECK

2

GEOMETRY

YES

NO

CO

2.1

Is the geometry fully specified?

X

2.2

Are the locations of boundaries specified?

X

2.3

Are the boundary types specified?

X

2.4

Is the geometry clearly illustrated?

X

2.5

Is the geometry available in digital form?

X

Comments:

The geometry is given in digital form so fully specified.

3

FLOW PHYSICS AND FLUID DYNAMICS DATA

YES

NO

CO

3.1

Are the physics of key processes identified?

X

3.2

Are the properties of the fluid specified?

X

3.3

Are the governing non-dimensional parameters (GNDPs) identified?

X

Comments:

TEST DATA

4

OVERVIEW of test data

YES

NO

CO

4.1

Have all the experiments been adequately defined?

X

4.2

Are the measurement techniques used described?

X

4.3

Has a summary of test runs been provided (matrix)?

X

4.4

Are there any important scaling issues/simplifications/uncertainties associated with the test geometry?

X

H

M

L

4.5

Impact of uncertainties on DOAPs ?

X

Comments:

5

EXP1 (Copy and complete this section for each set of test data)

YES

NO

CO

5.1

Is the experimental setup defined unambiguously?

X

5.2

Are the geometrical parameters defined?

X

5.3

Are the values of GNDPs specified?

X

5.4

Are the measured parameters (MPs) fully described?

X

5.5

Are measured data available in digital format?

X

5.6

Have conditions at all boundaries been specified?

X

5.7

Are any of the boundary data uncertain?

5.8

Is a realistic estimate of data accuracy given?

X

X

H

M

L

5.9

Impact of uncertainties on DOAPs ?

X

Comments:

Reapetability is not known but the accuracies are provided.

CFD SIMULATIONS

6

OVERVIEW of CFD simulations

YES

NO

CO

6.1

Have all the CFD runs been adequately defined?

X

6.2

Are the solution techniques used described?

X

6.3

Has a summary of runs been provided (matrix)?

X

6.4

Are there any important uncertainties associated with the computational domain geometry?

X

H

M

L

6.5

Impact of uncertainties on DOAPs ?

X

Comments:

7

CFD1 (Copy and complete this section for each set of CFD data)

YES

NO

CO

7.1

Is the modelling strategy defined?

X

7.2

Is the modelling strategy appropriate for the physical problem?

X

Solution strategy

7.3

Is the code (and version) specified?

X

7.4

Are the equations solved described adequately?

X

7.5

Is the numerical discretisation scheme used specified?

X

7.6

Is the solution algorithm described?

X

Computational Domain

7.7

Is the domain fully described?

X

7.8

Boundary conditions fully detailed?

X

7.9

Is the domain used an idealisation/simplification?

X

7.10

Is the mesh used fully described?

X

7.11

Is the mesh quality appropriate?

X

Boundary Conditions

7.12

Are the boundary conditions fully defined?

X

7.13

Are they appropriate?

X

7.14

Do these replicate conditions in test rig?

X

7.15

Were sensitivity runs carried out to explore effects of uncertainties in boundary data?

X

Application of physical models

7.16

Were turbulence models and other physical models applied in an appropriate and consistent way?

X

Numerical Accuracy

7.17

Is there any demonstration/estimation of numerical (discretisation) accuracy?

X

7.18

Was a mesh sensitivity study carried out?

X

7.19

Was sufficient iteration convergence achieved?

X

H

M

L

7.20

Impact of uncertainties on DOAPs ?

X

Comments:

The QinetiQ computations fulfill the usual quality requirements, excepted the systematic study of the effects of grid refinements. However, several grids have been tested. The comparisons with experiments appear satisfactory. Most of the flow characteristics are captured. Lift coefficients can be advantageously be computed for industrial applications because small discrepancies in Cp can have different impacts on coefficients.

7.21

7.22

7.23

7.24

7.25

7.26

7.27

7.28

7.29

7.30

7.31

7.32

7.33

7.34

7.35

7.36

7.37

7.38

7.39

7.40

8

EVALUATION - Comparison of Test data and CFD

YES

NO

CO

8.1

Is the comparison of CFD and test data clearly presented?

X

8.2

Are the discussion, conclusions and recommendations adequately supported by the available experimental and CFD results?

X

Comments:

The comparisons are limited to a few characteristics. No systematic analysis of influence of numerics or models are not provided.

Answers to the D29 L1T2 multi element airfoil

1) The decision is positive.

2) 1 Top level check, comments:

a) 6.8 % comes from the paper from Moir where it is stated that “the tunnel turbulence factor is 1.068”. I interpret as 6.8%, but I should admit that this statement is somewhat misleading... can be interpreted as 1.068%? if such is the case, the precision in the numbers is strange!

b)The presence of a short buble is recognized. I assume that it is important for the physics. However, we can change the statement as “The presence in the experiments of a short laminar bubble must be kept in mind while comparing CFD to experiments”

3) Part 7: CFD1:

It is clear that if Cp’s are poerfectly computed, lift coefficient is oK. However, small dicrepancies between computations and measurements in term of Cp can induce significant differneces in term of integral coefficient; this will depen on the location of the discrepancies. This is why I suggest to compute coefficients (that is an easy task) to be safe.

4) Part 8: CFD:

The last sentence can be omitted (“more details...”.

© copyright ERCOFTAC 2004

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Contributors: Antony Hutton; Jan Vos - QinetiQ; CFS Engineering SA

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