Flow behind a blunt trailing edge

Underlying Flow Regime 2-01 © copyright ERCOFTAC 2004

Quality Review

There are a number of unsatisfactory features, as indicated in the comments on later pages. If these could be addressed satisfactorily in the text, it might become a useful UFR, but probably only in the turbomachinery context.

Underlying Flow Regime Title: Flow behind a blunt trailing edge

UFR Author and UFR number: UFR2-01

Reviewer (Name/Organisation) : Ian Castro, University of Southampton (P16)

1	TOP LEVEL CHECK	YES	NO	CO
1. 1	Is the selected test-case study a good representation of the assigned UFR?		q
1. 2	Does the test-case study include both flow measurements and CFD calculations?		q	q
1. 3	Does the document under review comply with the D32 template		q	q
1. 4	Should any parts be expanded, condensed or deleted?		q	q
1. 5	Are the illustrations and their captions clear and informative?	q
1. 6	Are the references adequate and complete?		q	q
1. 7	If any hyperlinks are used, do these function correctly?	q	q

Comments:

1.1 But only really in the context of turbomachines 1.4 See various later comments 1.5 Probably more geometrical detail required 1.7 None used, but access to data sets would be helpful

DETAILED CHECK

2	REVIEW OF UFR STUDIES AND CHOICE OF TEST CASE	YES	NO	CO
2. 1	Have past studies of the UFR been reviewed adequately?		q	q
2. 2	Is the chosen test-case study selected from an established database or comparison exercise?	q
2. 3	Have the test-case experiments been devised for CFD validation?	q	q	q

Comments:
2.2 Unclear precisely why this test case is 'preferred for computational tests' (to quote the author).

3	DESCRIPTION OF THE STUDY TEST CASE	YES	NO	CO
3. 1	Is the geometry described adequately, including an appropriate sketch?	q
3. 2	Are the flow parameters defining the flow regime specified?		q	q
3. 3	Are the principal measured quantities (i.e. those by which success or failure of CFD is to be judged) specified?		q
3. 4	Is the description fully self-contained and sufficiently detailed ? (the level of detail required depends on whether a hyperlink to a detailed database is provided)	q		q

Comments:
3.1 Difficult to tell if there's enough detail supplied to allow a proper CFD model to be set up without further information. 3.3 Yes, perhaps, but not explicitly

3.4 No hyperlinks, so perhaps the data in Figs. 3-5 should be tabulated.

4	Test CASE EXPERIMENTS	YES	NO	CO
4. 1	Is the test-case facility described adequately?		q
4. 2	Are the measurement techniques explained?		q	q
4. 3	Is the quality/accuracy of the measured data discussed?		q	q
4. 4	Are the following quality aspects addressed in this discussion :-
a)	Closeness of flow to target/design conditions?	q
b)	Accuracy estimation of measured quantities?		q	q
c)	Checks on global conservation of conserved quantities?	q		q
d)	Consistency in the measurements of different quantities?		q
e)	Other (briefly describe)			q
4. 5	Is the evidence of data quality judged to be sufficient?		q	q
4. 6	Is the information provided at the flow boundaries sufficient to specify or estimate reasonably well the boundary conditions required for a CFD calculation?	q
4. 7	Is the overall discussion self-contained and sufficiently detailed? (the level of detail required depends on whether a hyperlink to a detailed database is provided)		q	q

Comments:

4.1 Perhaps, but see comment at 3.1
4.4a What are the set-up differences that lead to either steady or unsteady regimes?
4.4d only to a limited degree

4.6 Detailed geometry is oly available via a rather crude picture (fig.1) and a few parameter values.

5	CFD METHODS	YES	NO	CO
5. 1	Is an overview given of the methods used?		q	q
5. 2	Have the following aspects of the methods used been explained adequately:-
a)	The codes employed?	q
b)	The turbulence/physical models used?		q
c)	The wall treatments applied?	q
d)	The numerical boundary conditions?	q
5. 3	Are comments made on how well the boundary conditions replicate conditions in the test rig?	q		q
5. 4	Is the quality of the calculations discussed?		q
5. 5	Are the following quality aspects addressed in this discussion?			q
a)	The discretisation scheme(s) and solver(s)?		q	q
b)	The sufficiency of grid resolution(s) ?	q
c)	Sensitivities to uncertainties in the boundary conditions	q		q
d)	Comparisons between separate calculations using the same physical model	q		q
e)	Other (briefly describe)			q
5. 6	Is the evidence of CFD quality judged to be sufficient in all cases?	q		q

Comments:

5.2a No specific code is mentioned
5.2b Algebraic mixing length model is mentioned, but details not discussed, although references are given.
5.2c,d Not clear whether what is stated is sufficient. And if the RANS model is taken down to y+=0.3, is not a low-Reynolds number version required?
5.4 Only cursorily.

6	COMPARISON OF CFD CALCULATIONS WITH EXPERIMENT	YES	NO	CO
6. 1	Are key comparisons of CFD results with experiment presented in the form of tables or plots?		q	q
6. 2	Do these comparisons include the assessment quantities?		q	q
6. 3	Are further comparisons available via hyperlinks to a results database?	q		q
6. 4	Is the performance of the CFD calculations judged by comparison with experiments discussed and analysed in all cases?		q	q

Comments:

7	BEST PRACTICE ADVICE FOR THE UFR	YES	NO	CO
7. 1	Are model abilities for this test case discussed and analysed in sufficient detail?	q
7. 2	Are recommendations provided on which models should be used for this UFR?		q	q
7. 3	Are these recommendations supported by the evidence?		q	q

Comments:
7.1 Results appear reasonable, but it's unclear whether even simpler models might suffice for the limited quantities discussed (surface pressure, mid-span Mach number and shedding frequency). The text implies that there were different experimental regimes - steady and unsteady. Is this really so? If so, what differences in experimental parameters led to such differences? And steady state conditions were computed (Section 5), as well as unsteady, but they seem to have been obtained with an unsteady RANS. More clarity needed here.