Launch Ascent and Vehicle Aerodynamics (LAVA) (Computational Fluid Dynamics (CFD) solver) contribution to HiLiftPW-3 (3rd AIAA CFD High Lift Prediction Workshop). Including HL-CRM (NASA High Lift Common Research Model) and JSM (Joint Statistical Modeling) case studies

Denison, Marie

Housman, Jeff

Jensen, James

Kiris, Cetin

Stich, Gerrit-Daniel

NASA Technical Reports Server

LAVA	Contribution	to	
HiLiftPW-3
James	Jensen,	Marie	Denison,	Gerrit Stich,	Jeff	Housman,	
and	Cetin	Kiris
Computational	Aerosciences Branch
NASA	Ames	Research	Center
PID	033
3rd High	Lift	Prediction	Workshop
Denver,	CO		June	3-4,	2017
https://ntrs.nasa.gov/search.jsp?R=20190025379 2019-08-31T12:06:19+00:00Z
Summary	of	cases	completed:
- LAVA,	Overset	Structured,	SA-QCR2000
Case Alpha=8,	
Fully turb,	grid	
study
Alpha=16,	
Fully turb,	grid	
study
1a	(full	gap) yes yes
1c	(partial	seal) yes yes
HiLiftPW-3,	Denver	CO,	June	2017 2
Case Polar,	 Fully	turb Polar,	specified
transition
Polar,	w	
transition	
prediction
2a (no	nacelle) yes no no
2c (with	nacelle) yes no no
- LAVA,	Unstructured	Polyhedral,	SA
Case Polar,	 Fully	turb Polar,	specified
transition
Polar,	w	
transition	
prediction
2c (with	nacelle) yes no no
Case	 2D	Verification	
study
3 yes
LAVA Framework
Far Field
Acoustic Solver
Structural 
Dynamics
Object	Oriented	Framework
Domain	Connectivity/	Shared	Data
C++	/	Fortran	with	MPI	Parallelism	
LAVA
Multi-Physics:
Multi-Phase
Combustion
Chemistry
Electro-Magnetics
……
6 DOF 
Body Motion
Post-Processing
Tools
Conjugate 
Heat Transfer
Other Solvers
& Frameworks
Not Yet Connected
Connected Existing
Future
3
Framework
Developing
Other Development Efforts
• Higher order methods
• Curvilinear grid generation
• Wall modeling
• LES/DES/ILES Turbulence
• HEC (optimizations, accelerators, 
etc) Kiris at al. AST-2016 and AIAA-2014-0070 
Prismatic Layers
Structured 
Curvilinear
Navier-Stokes
Unstructured 
Arbitrary Polyhedral
Navier-Stokes
Structured 
Cartesian AMR
Navier-
Stokes
Lattice
Boltzmann
Actuator Disk
Models
• High quality body fitted grids 
• Low computational cost
• Reliable higher order 
methods
• Grid generation largely 
manual and time consuming
• Essentially no manual grid 
generation
• Highly efficient Structured 
• Adaptive Mesh Refinement 
(AMR)
• Low computational cost
• Reliable higher order methods
• Non-body fitted -> Resolution 
of boundary layers inefficient
• Partially automated grid 
generation
• Body fitted grids 
• Grid quality can be challenging
• High computational cost
• Higher order methods yet to 
fully mature
LAVA Computational Grid Paradigms
4
Structured 
Cartesian AMR
Unstructured Arbitrary 
Polyhedral
Structured 
Curvilinear
• 3D Structured Curvilinear RANS solver
• 2nd order accurate Modified Roe Flux 
Difference Splitting for the convective terms
• 2nd order central differencing for the viscous 
terms
• SA turbulence model with QCR-2000 for 
viscous flux tensor 
• 2nd Order 
• Cell Centered
• MUSCL Scheme
• AUSMPW+ Flux Function
• SA Turbulence Model
LAVA Solver Details
5
Unstructured Arbitrary Polyhedral Structured Curvilinear
HiLiftPW-3,	Denver	CO,	June	2017
All	simulations	are	cold	starts	with	no	CFL	
ramping
Brief	overview	of	grid	system(s)
Overset	Grid	for	Case	2c 6
Grid	System Case(s) If committee	grid,	report	any	problems/issues
If	user	grid,	reason	for	generating	grid	system
Committee	(Grid	A,	Structured	Overset) 1a and	1c Observed	solution	decoupling	in	unexpected	areas	of	the	grid
Committee	(Grid	A,	Structured	Overset) 2a	and	2c Used	custom domain	connectivity	with	committee	grids
User	(Unstructured	Polyhedral) 2c	 Custom	generated	with	different	wake	refinements
Unstructured	Grid	for	Case	2c
Generating	the	Overset	Structured	Committee	Grids	for	Case	2
• Generated	with	the	Chimera	Grid	Tools	(CGT)	
• The	grid	was	generated	as	a	medium	grid	using	the	parameters	from	the	
gridding	guidelines	document	provided	by	the	committee
• Trailing	edge	had	25	points	instead	of	the	9	specified	in	the	document
• Spanwise spacing	at	the	root	and	tip	of	elements	was	based	on	local	cell	sizes
• Used	separate	wake	meshes	rather	than	a	region	of	uniform	spacing	in	the	volumes
HiLiftPW-3,	Denver	CO,	June	2017 7
Case	2a
Case	2c
Reasoning	Behind	Wake	Grids
HiLiftPW-3,	Denver	CO,	June	2017 8
Wake	Streamlines
Final	“Geometric”	Wake	Grids
• Decided	to	use	a	“geometric”	
based	wake	grid
• Original	plan	was	to	generate	an	wake	grid	based	on	the	streamlines	
• The	streamlines	vary	greatly	with	angle	of	attack	so	the	streamline	
based	wakes	were	not	general	
Differences	Between	Mesh	Paradigms
• Overset	meshes	allow	more	control	in	areas	such	as	the	
leading	edges	of	the	elements
• Unstructured	mesh	can	capture	small	geometrical	features	
with	less	complexity	in	the	grid	
HiLiftPW-3,	Denver	CO,	June	2017 9
Inboard	Slat-Wing	Junction	(Overset) Inboard	Slat-Wing	Junction	(Unstructured)
LAVA	Modified	Implicit	Hole	Cutting	(MIHC)	Procedure
HiLiftPW-3,	Denver	CO,	June	2017 10
• First	the	DCF	routines	in	OVERFLOW	are	used	to	provide	a	minimum	hole	cut	
and	ensure	that	the	required	number	of	fringe	layers	are	available	(with	
minimum	hole)	for	the	flow	solver	(double	fringe	in	this	case)
• The	global	wall-distance	is	also	computed	and	stored	to	file
• Next	the	MIHC	code	is	applied	to	the	overset	grid	system	with	the	minimum	
holes	cut
Minimum	Hole Final	Hole
Wake	Grids
• The	different	connectivity	codes	incorporated	the	wake	grids	differently
HiLiftPW-3,	Denver	CO,	June	2017 11
MIHC	Wake	Grids Peg5	Wake	Grids
HL-CRM	(Case	1)	Topology	Difference
HiLiftPW-3,	Denver	CO,	June	2017 12
• Saw	larger	than	
expected	solution	
decoupling	in	the	
slat	Cp plots
• First	suspicion	was	
that	the	surfaces	
were	not	identical	
but	they	were	made	
by	splitting	one	
surface	mesh
• Different	volume	
grid	generation	
methods
• Leads	to	a	different	
amount	of	solution	
decoupling	at	the	
grid	interfaces
HL-CRM	(Case	1)	Topology	Difference	
HiLiftPW-3,	Denver	CO,	June	2017 13
• Slide	showing	
improvement	as	the	
mesh	is	refined
HL-CRM	(Case	1a)	Grid	Convergence	Effect
HiLiftPW-3,	Denver	CO,	June	2017 14
• Lift	is	converging	well	at	both	angles	and	has	converged	to	an	
almost	identical	value	from	both	solvers	at	both	angles
• Drag	is	converged	at	⍺=8	and	is	converging	at	⍺=16
• The	solvers	are	within	10	drag	counts	of	each	other	at	both	angles	
of	attack
JSM	(Case	2a)	Force	and	Moment	Comparisons
15
JSM	(Case	2a)	Cp Comparisons	D-D
HiLiftPW-3,	Denver	CO,	June	2017 16
• At	both	angles	of	attack	the	flap	is	fairly	different	
between	the	two	solvers
• At	⍺=18.58° the	difference	in	the	solutions	at	the	flap	
becomes	even	more	pronounced
• Overflow	appears	to	match	the	peak	better	and	LAVA	
appears	to	match	better	in	the	recovery	region
JSM	(Case	2a)	Cp Comparisons	G-G
• The	differences	between	the	solvers	is	more	
pronounced	at	this	station
• At	the	higher	angle	of	attack	the	differences	
become	more	pronounced
• On	the	flap	LAVA	is	closer	to	the	experiment	at	
the	peak	and	Overflow	is	closer	at	the	TE	
HiLiftPW-3,	Denver	CO,	June	2017 17
JSM	(Case	2c)	Force	and	Moment	Comparisons
18
JSM	(Case	2c)	Cp Comparisons	D-D
HiLiftPW-3,	Denver	CO,	June	2017 19
• At	the	lower	angle	of	attack	Overflow	is	more	closely	
matching	the	experimental	data	but	at	the	higher	angle	
of	attack	LAVA	more	closely	matches	the	experiment
• On	the	slat	Overflow	and	the	LAVA	Unstructured	result	
are	closer	to	the	experiment	at	both	angles	of	attack
JSM	(Case	2c)	Cp Comparisons	G-G
• At	the	low	angle	on	the	flap	we	see	a	similar	
trend	as	before;	Overflow	is	closer	to	the	
experiment	near	the	peak	but	LAVA	is	closer	in	
the	recovery	region
• At	the	high	angle	of	attack	all	of	the	solvers	have	
similar	predictions
HiLiftPW-3,	Denver	CO,	June	2017 20
Run	Time	and	Resource	Usage	Comparison
HiLiftPW-3,	Denver	CO,	June	2017 21
• Insert	table	with	representative	run	times	and	resources	for	Case	2c
Summary
• Generated	the	committee	overset	grid	system	for	
the	JSM	model	(Case	2a	and	Case	2c)
• Observed	some	unexpected	solution	decoupling	in	
Case	1	due	to	the	way	the	grids	had	been	
generated
• LAVA	force	results	agreed	well	with	the	Overflow	
results	for	Case	1
• The	Cp and	Force	results	are	similar	between	all	of	
the	solvers	for	both	Case	2a	and	Case	2c
• The	differences	within	the	results	can	be	mostly	
attributed	to	the	differences	in	the	turbulence	
models,	specifically	the	inclusion	of	RC
HiLiftPW-3,	Denver	CO,	June	2017 22
Acknowledgements
• Transformational	Tools	and	Technologies	(TTT)	
project	under	ARMD
• NAS	for	computer	time	on	Pleiades
HiLiftPW-3,	Denver	CO,	June	2017 23


LAVA Contribution to HiLiftPW-3

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