A series of inlet analysis codes (2-D, axisymmetric, 3-D) were developed which can analyze complicated flow through complex inlet geometries in a reasonably efficient manner. The codes were verified and are being used extensively to analyze practical inlet geometries both at Langley as well as industries. Newly installed VPS 32 computer will allow more complex configurations to be analyzed. Scalar FORTRAN versions are available to increase transportability of the codes for use on other Scalar computers and on the Cray vector processing computer

Kumar, Ajay

Trexler, Carl A.

English

NASA Technical Reports Server

[N88- 14936lp
ANALYSIS AND PERFORMANCE PREDICTION OF SCRAMJET
INLETS UTILIZING A THREE-DIMENSIONAL
NAVIER-STOKES CODE
_51o.....0 7
Ajay Kumar and Carl A. Trexler
NASA Langley Research Center
Hampton, Virginia
F.'_EC2_P_'GPAGE BL_|'_ i_.OTFiLM_D
PA__INTF-NTIONALLY. BLANK
187
https://ntrs.nasa.gov/search.jsp?R=19880005554 2020-03-20T09:06:19+00:00Z
Scramjet inlets have high geometric complexity as well as a 
highly complex flow field. The flow is primarily three- 
dimensional, possibly turbulent. It involves complex shock and 
expansion wave interactions. It also involves strong 
shock/boundary-layer interactions resulting in separated 
regions. Further, due to the aft placement of the cowl, the 
internal flow ahead of the cowl is exposed to the external flow 
resulting in interaction between the two. 
PR IMAR ILY THREE-DIMENSIONAL, POSSIBLY TURBULENT 
I NVOLVES COMPLEX SHOCK AND EXPANS I ON WAVE INTERACT IONS 
INVOLVES STRONG SHOCKIBOUNDARY -LAYER INTERACT IONS RESULT I NG I N SEPARATED 
REG IONS 
INVOLVES INTERACTION BETWEEN INTERNAL AND EXTERNAL FLOW F I E L D  RESULTING I N  
FLOW SP I LLAGE 
188 
INLET RESEARCH
Due to the complex nature of the flow, most scramjet inlet
research to date has been experimental with little supporting
analytical work. However, with the increasing availability of
high-speed, large-storage computers and advanced computing
techniques, it has become feasible to numerically simulate flow
fields associated with high-speed inlets. The goal of the
present research is to provide an accurate and efficient inlet
analysis tool that allows promising design configurations to be
developed with less reliance on extensive wind-tunnel testing.
3-D EULER/NAVIER-STOKES INLET ANALYSIS CODE
The research to provide inlet analysis software started with
the development of a two-dimensional Euler and Navier-Stokes
code; this was followed by the three-dimensional Euler and
Navier-Stokes code. An axisymmetric version of the code is also
available. In this presentation, I will discuss only the three-
dimensional analysis results. This figure briefly describes
the features of the code.
• Governing equations in conservation form
• Boundary-fitted curvilinear coordinates
• Algebraic turbulence model
o MacCorrnack's explicit or explicit-implicit scheme
• Fully vectorized
IR9
CODE ORGANIZATION AND PERFORMANCE
Special attention has been given to organize the code for
maximum use of the central core of the computer. The code is
fully vectorized and calculations are performed in planes with
temporary reusable vectors maintained only in two local planes.
Further, to save on storage requirements, the transformation
metric data are calculated in each time-step. On the CDC VPS 32
computer, the code can accommodate a maximum of 1.4 x 106 grid
points without going out of primary memory of the system. It has
a compute rate of about .7 x 10 -5 sec per grid point per time
step. For more details, see reference i.
• The code is written in Star Fortran and uses 32-bit word arithmetic
• Transformation metric data are calculated in each time step
• Calculations are performed in planes with temporary reusable vectors
maintained only in two local planes
I-1
I+1 I
I I
Predictor step completed
Corrector step started
•Maximum grid size that can be used without going out of primary
memory is approximately 1.4 million points
• Compute rate is. 7 x I0-5 sec/grid point for one complete time-step
(i.e. both predictor and corrector step)
• Typical solution can be obtained in 20-150 minutes CPU time for up
to 100,000 grid points
190
SYMMETRIC WEDGE CORNER AND SCHEMATIC OF CORNER FLOW
To verify the code, calculations were made for laminar and
turbulent flow for a 3-D symmetric wedge corner shown in the
figure. The flow in such a corner is representative of the type
of flow inside a scramjet inlet. A schematic of the basic
characteristics of the corner flow is also presented in the
figure. It has very complex structure that includes wall shocks,
corner shock, internal shocks, and slip lines.
In the present analysis, a grid of 39 x 61 x 61 points is
used with suitable refinement near the corner walls.
Calculations are made for the following conditions:
M = 3.0
N R = 3.9 x 105; laminar flow
i.i x 106; turbulent flow
T = 105°K
T = 294 °K
w
1 CORNERSHOCK
2 INTERNALSHOCK
3 SLIP LINE
4 WALL SHOCK
4
(a) (b)
191
DENSITY CONTOURSFOR SYMMETRICWEDGECORNER
The figure shows the density contours for the laminar flow
as obtained from the present code. Experimentally determined
contours are also shown. It is seen that the calculations have
predicted the corner flow features very well and are in very good
agreement with the experiment.
Z-Z
w.
X
.5
0
O
O
LAMINAR FLOW
o EXPERIMENTALRESULTS(Ref.2)
Y- YW
X
192
SURFACE PRESSURE DISTRIBUTION FOR SYMMETRIC WEDGE CORNER
This figure presents a comparison of the sidewall pressure
distribution with experiment for the laminar and turbulent
flow. The predicted results compare well with the experimental
results.
1.8
Pressure 1.6
ratio 1.4
1.2
1.0
.8
0
2. 0 _- Present results
8_ •
1. o Experimental results (Ref.
Pressure 1. 6
ratio 1.4 _ '_ Laminar flow
1:°E-8 -_oo
2,0-
o_ Turbulent flow
°oo-o-_oooo
.2 .4 .6 .8 1.0
Distance from corner edge
2)
193
HIGH-SPEED INLET CONFIGURATIONS
The next four figures present a variety of high-speed inlet
configurations that have been analyzed with the 3-D Navier-Stokes
code. Results on two other configurations will be presented
later.
GEOMETRY OF THE PARAMETRIC SCRAM JET ENGINE
HI = 7.2,W = 6.4,G = 1.6
10° 22.834(INLET SWEEP ENDS
_ ALONG THE DASHED LINE)
0 5 i0 15 20 25 30 35
STAT ION 15 l---x
4.166[" 22.834 o -,- -, 3o
FLOW
STATION 25 =:::X>
_L__ --S I DEWALL(ALL DIMENSIONS IN INCHES)
GEOMETRY OF AFT INLET CONFIGb'RATION
0 2 4 6 8 10
_. I 1 I I I
1.9o9 _-_-- ...f-RAMP
" 45_ \ , L_u ur _. f-6.865
zt _ I S'DEWALL "-_/'_
L_.. \ _ COMPRESSION ------------',_ .... _ --_..
C9SIDEPLATES _ o./1_ COWL
5.233 o
2.0
l
T0;- -
(ALL DIMENSIONS IN INCHES)
A I
194
TYPICAL MITS INLET CONFIGURATION
Top view
Bow shock
F,_owl I nter nal
_,m,u..,._n_mam._.. side plate
_'='_=_'mms'_mz_ann'/boundaries
Swept back
side p,ate 7 Flowfield k_J
/ of interest ,,_ ....
oat view __vlew
gow sh___,_,_,_lwm_"_._-...__
12.5° Cone
Side view
SUPERSONIC INLET DUCT
Recta n g le Ellipse C ircle
Flow
/
I
I
195
PHYSICAL DOMAIN OF COMPUTATION
Before any results on the inlets are presented, a brief
description is given on how the present analysis accounts for the
interaction of internal flow with the external flow. As
mentioned earlier, this interaction occurs due to the aft
placement of the cowl, which exposes the flow inside the inlet to
the flow outside the inlet in the region ahead of the cowl. In
order to account for this interaction, a portion of the outside
flow under the cowl plane must be included in the analysis.
Ideally one should go down and around the sidewalls far enough so
that the free-stream conditions can be applied on the free
boundaries but this would greatly increase the computational
requirements. In the present analysis, the region is extended as
shown in the figure by the dashed line (only half of the flow is
calculated due to symmetry). This limited extension of the
computational domain should be sufficient because in the actual
engine, several such modules will be placed side by side.
I
I
l
I
SYMMETRY
LINE
f Jl
f Jl
/A
f A
/M
196
LINE DIAGRAMOF SINGLE-STRUT, REVERSE-SWEEPINLET
The first configuration is a single-strut, reverse-sweep
inlet shown here in a line diagram. It has wedge-shaped
sidewalls which are swept back at an angle of 30 ° . A compression
strut is located in the center passage of the inlet, which is also
swept, but it is swept forward at an angle of 30 ° . The throat
width is held constant at all heights in the inlet, which results
in an unswept throat. The cowl closure starts at D. Various
other geometrical parameters are shown on the line diagram. Flow
is calculated at the following conditions:
M1 = 4.03, Pl = 8724 N/m2, T1 = 65°K
These correspond to experimental conditions.
H1 , , = 6°= 2.75 in. W= 1.005 in. W/G=4.16, 6s
/_' _ III
III
III
,., III
III
"'" iii
"'" iii
"'" III
,-, iii
,-, iii
"'" III
,-, III
Section at DD'
D' B'
B\ /
730°\ o_,o / Throat_ xx
___)U 1 I \
Z \'-1 ,/,, , ,,
\i I x
_"X AV _ _ A'
D
xc = xT= 5. 22 in._ Cowl
Plane AA'
197
PRESSURECONTOURSIN PLANES PARALLEL TO THE COWLPLANE
(M1 = 4.03)
This figure shows the pressure contours in three planes
corresponding to z/H 1 = 0.145, 0.5, and 0.89. One of the
problems associated with single-strut inlets with similar sweep
on the sidewalls and the strut is that for a given Mach number,
the shock waves from the sidewalls and the strut will coalesce
into a stronger shock wave which is not desireable for the
operation of the inlet over a Mach number range with fixed
geometry. In the present configuration, it appears that the
shock wave coalescence problem is alleviated. Due to the
opposite sweep, shock waves coalesce only in certain planes but
not all across the inlet height at a given Mach number. For
example, the pressure contours show that for the present
conditions, shock waves coalesce in the planes near the top
surface but not in the planes near the cowl.
z/H1=0.89
zlH 1=0.145
198
VELOCITY VECTOR FIELD IN PLANES PARALLEL TO THE COWL PLANE
(M 1 = 4.03)
This figure shows the velocity vector field in the same
three planes. The separated flow regions on the sidewalls
substantiate the observation made from the pressure contours.
z/H 1
iiiiiiii4iiiiiiii4iiii+ i  +  +o...
199
SIDEWALL PRESSURE DISTRIBUTIONS
This figure shows a comparison of the static sidewall
pressure distributions with the experiment. It is seen that the
predicted pressure levels compare very well with the experimental
results up to the inlet throat. Deviations seen downstream of the
throat are due to the fact that the experimental model had
significantly different geometry than that used in the present
calculations.
[ o SIDEWALLSWEEP= 30°
15_ STRUTSWEEP= 3(P
WIG= 4.16
P/Pl lO _ _ M1 = 4"03
5 _-_.,._._.,r_k,,,,," _H I = 0.89
0
15 ----" PRESENT RESULTS
o EXPERIAAENTALRESULTS
10
P/Pl
5 dH I = 0.5
0
P/Pl 5 Z/H1 = 0.145
0 2 4 6 8
X, in.
200
LINE DIAGRAMOF TWO-STRUTINLET
The second configuration for which results are presented
here is a two-strut scramjet inlet. A line diagram of the inlet
is shown below. This inlet also has wedge-shaped sidewalls which
are swept back at an angle of 30 ° Two compression struts are
located in the center passage of the inlet and are also swept
back at an angle of 30 ° • Sweep of all compression surfaces ends
along line EF and the cowl closure starts at F. Various other
geometrical parameters are shown on the line diagram. Flow is
again calculated at Mach 4.03 in order to be able to compare with
the experimental results.
2. 75 i k. \,, iCowll i l
• \ ,, II i
l B\ " .\z ,,:F i'
Section along ZZ'
T
2.8 in.
J_ 6°---,,-----_---_
4
-_v_':.Plane AA'
I
J
..... - Plane BB'
201
COMPUTATIONALGRID
This figure shows the computational grid in one of the cross
planes and in the symmetry plane. The calculations presented
here are made with a grid of 41 x 51 x 37 points in x, y , z-
directions, respectively. Out of the 37 planes in the z-
direction, ii planes lie under the cowl plane to account for the
interaction between the internal and external flow.
Discretization of this inlet is further complicated by the struts
embedded in the flow field. In order to accommodate the strut,
the present analysis makes the strut surfaces coincident with two
grid planes in the y-direction and further allows i0 more grid
planes to go through the strut. This results in slight blunting
of the strut leading edge, but this blunting is relatively small
due to grid concentration in the neighborhood of the strut
surfaces. A typical cross-plane grid is shown in the figure. If
a particular cross plane lies above the cowl plane, the grid
points lying within the strut are disregarded and proper boundary
conditions are applied on the strut surfaces, but if the cross
plane lies below the cowl plane, all grid points in the plane are
used in the calculations.
Symmetry plane
Cross plane
202
ORIGINAL }>?:,'7 7"
O_E EOOR QUA _%_2_'[
VELOCITY VECTOR FIELD AND PRESSURE CONTOURS IN PLANE LOCATED
AT MID-INLET HEIGHT
This figure shows the velocity vector field and static
pressure contours in a plane located at mid-inlet height. Slight
blunting of strut leading edges and associated small distortions
are obvious from this figure. The velocity vector plot shows
several regions of separated flow caused by the shock/boundary-
layer interaction and the pressure contour plot shows clearly the
shock and expansion waves and their interactions.
203
VELOCITY VECTORFIELD AND PRESSURECONTOURS
IN THE SYMMETRYPLANE
This figure shows the velocity vector field and static
pressure contours in the symmetry plane. The velocity vector
field shows a downturn in flow direction ahead of cowl resulting
in some flow spillage. The downturn is caused by the sidewall
sweep and the interaction between the flow inside and outside of
the inlet. Once the inlet flow passes behind the cowl leading
edge, it is turned back parallel to the cowl plane, and this
turning results in a cowl shock which can be seen in the pressure
contour plot on this figure.
ORIGINAL PAGEIS
OF POORQUALITy
204
SURFACEPRESSUREDISTRIBUTIONS IN A TWO-STRUTSCRAMJETINLET
Static pressure distributions on the sidewall at two inlet
heights are shown in this figure. As seen from the figure, the
predicted pressure distributions compare very well with the
experimental data.
PIP1
1.5-
0
Sidewall
I I I I I I
1 2 3 4 5 6
X, in.
_-- Present results
0 Experimental results (Trexler)
_ Sidewall
I I I I I I I
7 0 1 2 3 4 5 6
X, in.
2O5
SURFACEPRESSUREDISTRIBUTION IN A TWO-STRUTSCRAMJETINLET
This figure shows a comparison of the predicted static
pressure distribution with the experiment on the strut inner
surface at mid-inlet height. Here again, the predicted results
compare very well with the experiment.
Although not discussed much here, the flow captured by the
inlet is an important measure of inlet performance. An accurate
prediction of inlet capture also provides support to the procedure
used here to account for the interaction between the internal and
external flow ahead of the cowl. In the present analysis of the
two configurations discussed here, predicted inlet flow capture
compared very well with the experimentally predicted value.
Strut (Center Passage)
15
10
P/P]
5
- ---- Present results
0 Experimental results (Trexler)
H=O.
I I I I I I I
0 1 2 3 4 5 6 7
X, in.
206
PCONCLUDING REMARKS
• A series of inlet analysis codes (2-D, axisymmetric, 3-D)have been
developed which can analyze complicated flow through complex inlet
geometries in reasonably efficient manner
• The codes have been verified and are being used exLensively to analyze
practical inlet geometries both at Langley as well as industries
• Newly installed VPS 32 computer will allow more complex configurations
to be analyzed
• Scalar Fortran versions available to increase transportability of the codes
for use on other Scalar computers and on Cray vector processing
computer
207
••
REFERENCES
Kumar, Ajay: Numerical Analysis of a Scramjet Inlet Flow
Field Using the Three-Dimensional Navier-Stokes Equations•
CPIA Publication 373, Feb. 1983, pp. 25-39.
West, J. E.; and Korkegi, R. H.: Supersonic Interaction in
the Corner of Intersecting Wedges at High Reynolds Numbers•
AIAA Journal, vol. i0, no. 5, May 1972, pp. 652-656.
208


Analysis and performance prediction of scramjet inlets utilizing a three-dimensional Navier-Stokes code

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server