1 shock-induced boundary layer separation in round c-d nozzles khairul zaman inlets and nozzles...

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Shock-induced boundary layer separation in Round C-D nozzles

Khairul Zaman

Inlets and Nozzles Branch, NASA GRC

Cleveland, OH 44135

Co-investigators: Timothy Bencic, Amy Fagan and Michelle Clem

Optics and Photonic Branch

Supported by

Commercial Supersonic Technology and

Transformative Tools and Technologies Projects

SWBLI Workshop, Dayton, OH

April 14-15, 2015

NASA Glenn Research Center

SWBLI Wkshp, Dayton, April 14-15, 2015 Zaman/GRC

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Background:

Shock-induced BL separation occurs in Convergent-divergent (C-D) nozzles when run in overexpanded condition. Such condition occurs, e.g., during certain flight regimes and also with rocket nozzles during start-up.

These flows are noisy and may involve detrimental unsteady loads.

As a first step in any analysis one requires the knowledge of mean shock location within the divergent section for a given nozzle pressure ratio (NPR).



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Background:

Shock location within C-D nozzles have been studied in many previous investigations

Stodola experiment (1903) AndersonData with rocket nozzles Morrisette & Goldberg

1978

However, systematic database especially for lower design Mach number nozzles, typical of aircraft application, is lacking.



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Objective:

Conduct experiment with a set of C-D nozzles to study steady-state shock-location as a function of ‘jet Mach number’ Mj (or NPR)

Analyze results vis-à-vis an available correlation and 1D theory

Experimental method: Pressure sensitive paint static pressure taps and shadowgraph

Note: Mj is ‘Mach number’ had the jet expanded fully for a given NPR.



AIAA Paper 2011-1031 Zaman/Bencic/Clem/FaganWith new data manuscript submitted for Journal publication

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Experimental Facility

Open jet rig

MD=1.8 Noz


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Facility:Nozzle characteristics

Nozzle Design Mach No., MD

Throat diameter Dt

Div. section length

M14 1.4 1.8952 1.832

M16 1.6 1.7900 2.382

M18 1.8 1.6702 2.630

M18L 1.8 1.6702 3.351

M22 2.2 1.4148 3.351

M28 2.8 1.0730 4.002

For these nozzles: exit diameter = 2”, Length = 7.5”

CAD image of M22

x (in)

r(i

n)

0 1 2 3 4 5 6 7 80.5

1

1.5

2

2.5

MD=

2.82.2

1.81.61.4

1.8L

Internal contours


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FacilityAdditional nozzles

Large M21LgDE=3.5, Dt=2.567 Total length = 15Div sec length, L=4.2MD=2.1

Small M18SmGeometrically Similar to M18 DE=1.485MD=1.8


Mj [=] 0.4 – 1.7; ReD [=] 0.35x106 – 0.58x107 covered in experiment

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Sample raw PSP dataM18 Nozzle


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MJ

Wal

lPre

ssu

re,p

w/p

a

0.5 1 1.5

0.5

1

1.5

2 p1p2p3p4p5p6p7p8

PSP Data

MJ

Wal

lPre

ssu

re,p

w/p

a

0.5 1 1.5

0.5

1

1.5

2 p1p2p3p4p5p6p7p8

Data from 8 pressure taps

Comparison of PSP data with static pressure tap dataM18L

Pressure tap data PSP data


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x / De

Wal

lPre

ssu

re,p

w/p

a

-1.5 -1 -0.5 00.5

1

1.5

2

2.5

MJ=0.4MJ=0.5MJ=0.6MJ=0.66MJ=0.7MJ=0.8MJ=0.9MJ=1.0MJ=1.1MJ=1.2MJ=1.3MJ=1.4MJ=1.5MJ=1.6

M18

x / De

Wal

lPre

ssu

re,p

w/p

a

-1.5 -1 -0.5 0

0.5

1

1.5

2

2.5

MJ=0.4MJ=0.5MJ=0.6MJ=0.7MJ=0.8MJ=0.9MJ=1.0MJ=1.1MJ=1.2MJ=1.3MJ=1.4MJ=1.5MJ=1.6MJ=1.66MJ=1.73

M18L

Profiles of wall pressure from PSP dataM18 and M18L

At separation, pw /pa 0.5 noted before Papamoschou & Johnson 2010


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Morrisette & GoldbergNASA TP 1978

Reshotko & TuckerNACA TN 1955

Shock location vs. Mj

M18L

Mj

(x-x

*)/L

1 2 30

0.2

0.4

0.6

0.8

1

PSPPressure taps1-D theoryMG correlation

M18L


DesignN. Shock @exit

Throat choked

1-D

th

eory

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MGRT correlation (Morrisette & Goldberg 1978 )Per Reshotko & Tucker (1955) (Eq. 3) assuming H1=1.286 and H2=2.2, M2 /M1=0.762 is obtained.

With M2= 0.762M1 find p2 /p1 (oblique shock Eqns. 128 and 132, Ames Table).

For a given x-location of the shock, find nozzle diameter at that x. Calculate Mach number assuming fully expanded flow up to this point. This is M1 (upstream of oblique shock). From M1, find corresponding wall pressure p1 /p0. Assuming p2 = pa , p0 /pa is found which yields Mj.


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M14 and M16

Mj

(x-x

*)/L

1 20

0.2

0.4

0.6

0.8

1M16

Mj

(x-x

*)/L

1 20

0.2

0.4

0.6

0.8

1M14


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M18 and M18L

Mj

(x-x

*)/L

1 2 30

0.2

0.4

0.6

0.8

1M18

Mj

(x-x

*)/L

1 2 30

0.2

0.4

0.6

0.8

1M18L


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M22 and M28

Mj

(x-x

*)/L

1 2 30

0.2

0.4

0.6

0.8

1M28

Mj

(x-x

*)/L

1 2 30

0.2

0.4

0.6

0.8

1M22


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Mj

(x-x

*)/L

0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

0.2

0.4

0.6

0.8

1

M14M16M18M18LM22M28


For the six 2” nozzles


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For the six 2” nozzles

Mj / MD

(x-x

*)/L

0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

M14M16M18M18LM22M28tanh curve fit


y=(tanh(x-0.65))*0.5+0.5, x=Mj /MD , y=(x-x*)/L=5 for Mj/MD <0.65 and =8 for Mj/MD >0.65

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For the large and small nozzles

Mj / MD

(x-x

* )/L

0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

M18M18 SmallM22M21 Largetanh curve fit


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Acceleration parameter K for different nozzles

Thus, BL before separation must be turbulent for M21Lg case

For other nozzles cannot be sure but also likely to be

turbulent


r /D

E

x/DE

K(=

U'/U

2x1

0-6)

-3 -2 -1 00

5

10

15

20M14M18M18LM28M21Lg

LaminarTurbulent

Narasimha & Sreenivasan1979

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Conclusions:

Shock-induced boundary layer separation location documented for C-D nozzles of MD in the range 1.4-2.8.

PSP technique satisfactorily provided relative trends of wall pressure.

Data compared with a correlation from rocket nozzle literature; it agreed better for nozzles of higher MD but deviated at low MD.

All data correlated simply with the ratio of ‘jet Mach number’ to design Mach number (Mj /MD). A correlation equation is provided.

The correlation is found to be valid over a wide range of Re (0.35x106 – 0.58x107). An analysis indicates that the state of the boundary layer prior to separation is likely to be turbulent for all cases studied.



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x / De

Wal

lPre

ssu

re,p

w/p

a

-1.5 -1 -0.5 00.5

1

1.5

2

2.5

3

3.5

MJ=0.4MJ=0.5MJ=0.6MJ=0.7MJ=0.8MJ=0.9MJ=1.0MJ=1.1MJ=1.2MJ=1.3MJ=1.4MJ=1.5MJ=1.6

M14

x / De

Wal

lPre

ssu

re,p

w/p

a

-1.5 -1 -0.5 0

0.5

1

1.5

2

2.5

3


M16

Profiles of wall pressure from PSP dataM14 and M16


Backup 1

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x / De

Wal

lPre

ssu

re,p

w/p

a

-1.5 -1 -0.5 0

0.5

1

1.5

2

2.5


M22

x / De

Wal

lPre

ssu

re,p

w/p

a

-2 -1.5 -1 -0.5 0

0.5

1

1.5

2

MJ=0.4MJ=0.5MJ=0.6MJ=0.7MJ=0.8MJ=0.9MJ=1.0MJ=1.1MJ=1.2MJ=1.3MJ=1.4MJ=1.5MJ=1.6

M28

Profiles of wall pressure from PSP dataM22 and M28


Backup 2

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Minimum pressure at static pressure tapsM18L

(x - x*)/L

Min

imu

mp

w/p

a

Mjco

rres

po

nd

ing

tom

inim

um

pw/p

a

0 0.2 0.4 0.6 0.8 10.5

0.6

0.7

0.8

0

0.5

1

1.5

=>

<=

AIAA Paper 2011-1031 Zaman/Bencic/Clem/Fagan

Backup 3

1 shock-induced boundary layer separation in round c-d nozzles khairul zaman inlets and nozzles...

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