1
Computational Fluid Dynamics Simulation of
Hypersonic Engine Components
by
Jack R. Edwards
Associate Professor
Department of Mechanical and Aerospace Engineering
North Carolina State University, Raleigh, NC
2
Overview
Computational fluid dynamics simulation of hypersonic engine
components
–
a major research thrust area in Aerospace Engineering at
NCSU since the Mid 1980s.
Current areas of emphasis
:
•
Nose

to

tail simulations of complete engine flowfields (NASA
Glenn; Edwards and McRae)
•
Modeling of turbulent Schmidt number and Prandtl number effects
in supersonic combustion (NASA Langley; Hassan and Edwards)
•
Modeling of supercritical

fluid and barbotage injection of
hydrocarbon fuels (AFRL/PRA; Edwards)
•
Algorithmic enhancements to NASA’s VULCAN flow solver
(NASA Langley; Edwards and McRae)
•
Hybrid large

eddy / Reynolds

averaged modeling of scramjet
component flowfields (NIA Seed Grant; Edwards)
3
Personnel
Dr. Jack R. Edwards,
Associate Professor
•
CFD algorithm development for reacting / multi

phase flows
Dr. Hassan A. Hassan
, Professor
•
Transition and Turbulence Modeling
Dr. D. Scott McRae,
Professor
•
Solution Adaptive Gridding Methods
Jason Norris
, Keith McDaniel, Ming Tian: Ph.D. students
Ana Pinto, Michael Schoen: M.S. students
Adam Amar: Undergraduate research assistant
4
Unique Contributions
Low

Diffusion Flux

Splitting Schemes (LDFSS)
•
High

resolution upwind

differencing methods
•
Extensions for real fluids, gas

solid flows, multi

phase mixture
flows, chemically reacting flows, etc
•
Several parallel, multi

block, implicit flow solvers built around
LDFSS techniques
k

Transition / Turbulence Models
•
Coordinate

invariant two

equation model for wall

bounded and
free

shear flows at all speeds
•
Transition model accounts for Tollmein

Schlicting, crossflow,
bypass, and second

mode disturbance growth
•
Predicts onset and extent of transition and has been coupled with
the Spalart

Allmaras and the
k

model
5
Unique Contributions
Dynamic Solution

Adaptive Gridding Techniques
•
Improved feature resolution through point

clustering
•
Extensions for time

accurate flows, multi

block grids with non

contiguous interfaces, unstructured grids
•
Recent applications to high

speed inlet unstart and pollutant source
tracking in air

quality models
Hybrid Large

Eddy / Reynolds

Averaged (LES/RANS)
Simulation methods
•
Techniques combine RANS strategies near solid surfaces with
LES strategies further away
•
Transition facilitated by flow

dependent blending functions
•
Applications to shock / boundary layer interactions in internal
flows
6
Resources
NCSC IBM SP

2 (720 processors, 1 teraflop; soon to be
replaced with a linux Beowulf cluster)
4

processor Compaq ES

40
2

processor Microway DS

20
1

processor Compaq XP

1000
Several Sun, SGI workstations
Several PCs
LaTEX, Tecplot, Ensight, animation software
VULCAN (NASA Langley), CHEM3D (Dow Chemical)
REACTMB variants (NCSU)
All codes parallelizable with MPI message

passing
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High

Speed Propulsion
Time

dependent simulations of Scramjet inlet / isolator /
combustor interactions
Nose

to

tail simulations of NASA Glenn’s GTX Rocket

Based Combined

Cycle engine concept
Addition of time

derivative preconditioning and parallel
implicit schemes to NASA’s VULCAN flow solver
Simulation of injection of supercritical fuels
Simulation of aerated

liquid injection of hydrocarbon
fuels (Barbotage)
8
Independent Ramjet Stream Cycle in RBCC Engines
Injectors add fuel to the incoming air.
Mixing in ramjet stream precedes ignition.
Thermal throat is present.
Location of thermal throat can be modulated by variations in fuel injection.
Thermal Throat
Flame Front
Rocket exhaust
Fuel injection and
premixing
9
Rocket

Based Combined

Cycle Simulations
10
Rocket

Based Combined

Cycle Simulations
11
Rocket

Based Combined

Cycle Simulations: Rocket

shutoff with
Nitrogen Purge
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Aerated

liquid (Barbotage) injection experiments
The Air Force Research Lab
(AFRL) aerated

liquid injector is
schematically illustrated in Fig. 01;
Rectangular configuration with a
dimension of
6.4
mm x
2.0
mm;
A square cross section with
dimension,
D
, of
2.0
mm used for
the final discharge passage,
L/D=20
, converging angle
θ
=
50
°
;
Water as the test liquid, and
nitrogen as the aerating gas.
Fig
.
01
,
Schematic
of
the
injector
assembly
and
internal
flow
structure
13
Volume fraction contours (GLR = 0.08%)
Bernoulli inflow B.C. for the liquid phase
14
GLR=2.45% Photos and simulations
15
Hybrid LES/RANS Simulation Techniques
General approach: unsteady RANS (Reynolds

Averaged Navier

Stokes) near solid surfaces
–
LES (large

eddy simulation) in outer part
of the boundary layer and in free

shear layers
Transition between RANS / LES based on flow

dependent blending
functions based on ratios of turbulence length scales
–
best results
when transition occurs in outer part of log layer
RANS models: k

and Menter’s k

LES subgrid model: Yoshizawa’s one

equation SGS model
Applications to cavity flameholder configurations, flow behind
projectiles, shock / boundary layer interactions
16
Hybrid LES/RANS Simulation Techniques
Instantaneous axial velocity (25 degree compression / expansion
corner
)
17
Hybrid LES/RANS Simulation Techniques
x
'
,
c
m
p
w
/
p

5
0
5
0
.
5
1
1
.
5
2
2
.
5
3
3
.
5
4
4
.
5
5
E
X
P
H
y
b
r
i
d
(
k

,
F
=
F
3
,
f
i
n
e
g
r
i
d
)
H
y
b
r
i
d
(
k

,
F
=
F
3
,
c
o
a
r
s
e
g
r
i
d
)
R
A
N
S
(
k

)
Wall pressure distributions (25
degree compression/ expansion
corner)
u
/
u
e
y
'
,
c
m
0
0
.
1
0
.
2
0
.
3
0
.
4
0
.
5
0
.
6
E
x
p
H
y
b
r
i
d
(
k

,
F
=
F
3
,
f
i
n
e
g
r
i
d
)
H
y
b
r
i
d
(
k

,
F
=
F
3
,
c
o
a
r
s
e
g
r
i
d
)
R
A
N
S
(
k

)
x
'
=
1
.
2
5
c
m
2
.
3
5
c
m
3
.
1
0
c
m
1
1
1
0
Velocity profiles in recovery
region (25 degree compression /
expansion corner)
18
NIA

Sponsored Work
Primary Goal: to extend earlier work in hybrid LES/RANS simulations to
three

dimensional flows characteristic of dual

mode scramjet engines
Year 1 accomplishments
•
Addition of generalized multi

block capability to hybrid LES/RANS
solver
•
Addition of full reactive

flow capability
•
Development of better blending functions to shift modeling from
unsteady RANS to LES
Test cases underway:
•
Investigation of separation

shock unsteadiness in compression

corner
interactions
•
Simulation of reactive flow downstream of UVA single

ramp, dual

mode injector using hybrid LES/RANS
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NIA

Sponsored Work: Separation

Shock Unsteadiness
Prediction of response of turbulent boundary layer to shock interaction
(representative of high

speed flows within inlet / isolator configurations)
Large

scale, low

frequency unsteadiness of regions of shock

separated
flow observed in experiments
Can hybrid LES/RANS methods predict this type of unsteadiness?
20
NIA

Sponsored Work: Separation

Shock Unsteadiness
Time

dependent surface pressure contours
21
NIA

Sponsored Work: Separation

Shock Unsteadiness
Average surface pressure distributions
PDF of separation

shock position
22
Leveraging NIA

Sponsored Work
“
Hybrid LES/RANS Simulations of Complex Internal Flows with
Multiple Shock / Boundary Layer Interactions” Edwards and Hassan;
AFOSR; pending
“Database and Model Development for Combined

Cycle Mode
Transition” McDaniel, Cresci, Edwards, Goyne, O’Brian, Riggins,
Schetz; NASA NGLTP; pending (submitted by NIA)
MURI White Paper on Combined Cycle Engines, Frankel, Edwards,
McDaniel, Goyne, Hanson, Sung, Dutton, Loth; AFOSR; pending
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Challenges
Demise of North Carolina Supercomputing Center (July 1, 2003)
–
loss of 720 processor IBM SP

3
Mitigation strategies:
•
32 processor IBM P690 (NCSU)
•
32 processor IBM Bladecenter (NCSU)
•
128 processor IBM Bladecenter (NCSU; under construction;
expandable)
•
Access to 1024 processor IBM SP

3 at Oak Ridge National
Laboratories
24
Simulation of a time

dependent coatings process
25
Pollutant Capture in Circulating Fluidized Beds
Three

phase system: two solids phases, one multi

component gas phase
Sub

models for fine particulate matter agglomeration,
sulfur dioxide sorption, mercury capture onto activated
carbon
High

resolution LDFSS extension for separated gas

solid
flows
26
Solids voidage time evolution
27
Fine PM number density time evolution
28
Fine PM flow rates
29
Supercavitating water flow about a projectile
30
New Directions
Atmospheric turbulence modeling and solution

adaptive
meteorological simulations
Level

set methods and immersed

boundary algorithms
•
Human

induced contaminant transport
•
Diesel engine injector simulations
•
Two

phase bubble dynamics
Hybrid LES/RANS simulations of
•
Shock

train propagation
•
Ramped

injector flowfields
•
Biological systems (lung bronchii, aortic aneurisms)
31
Level

Set / Immersed Boundary Methods: 2

D
Simulation of “feet” moving in a box filled with air
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