Carlson, Jan-Renee

Lee, Henry

Pulliam, Thomas

Rumsey, Chris

NASA Technical Reports Server

SIMULATIONS OF THE NASA LANGLEY 14- 
BY 22-FOOT SUBSONIC TUNNEL  
FOR THE JUNCTURE FLOW EXPERIMENT
April 16, 2018
Henry Lee
Science and Technology Corp.
 Thomas Pulliam
NASA Ames Research Center
Chris Rumsey & Jan-Renee Carlson
NASA Langley Research Center
https://ntrs.nasa.gov/search.jsp?R=20190025480 2019-08-31T13:31:21+00:00Z
Sponsored by NASA’s Transformative Aeronautics Concepts Program’s 
Transformational Tools and Technologies (T3) project 
• Substantial effort to investigate the origin of separation bubbles found in wing-
body juncture zones
• Primary goal is to gather validation level data, for future CFD code & turbulence 
model development
• Multi-year effort including several large-scale wind tunnel tests
• First set of entries just finished: Nov 2017-April 2018
• Planned Entries in 2019, 2020
Juncture Flow Experiment
2
Juncture Flow Physics
Model proposed 
by Barber et al.
• Flow physics of juncture flows is complex
• Several vortical structures coexist: e.g., 
Horseshoe Vortex (HSV), corner vortex, stress-
induced vortex
• Many factors: incoming boundary layer momentum 
thickness, wing bluntness, and wing sweep, etc
3
Juncture Flow LDV
4
• Use internal Laser 
Doppler Velocimetry 
(LDV) system
– Mounted inside of 
the fuselage
– Movable three-axis 
traverse system
– Measure the flow 
field through window 
on fuselage
– Closest possible 
location to wing-
body juncture
Juncture Flow LDV
4
• Use internal Laser 
Doppler Velocimetry 
(LDV) system
– Mounted inside of 
the fuselage
– Movable three-axis 
traverse system
– Measure the flow 
field through window 
on fuselage
– Closest possible 
location to wing-
body juncture
Juncture Flow Model Details
5
Wing is a truncated 
DLR-F6
14x22 Wind Tunnel
Mach 0.2
Reynolds Number 2.4M 6
14x22 Wind Tunnel
Mach 0.2
Reynolds Number 2.4M 6
High Speed Leg
Introduction
• Juncture Flow (JF) Experiment
• Heavy collaboration between CFD and WT design 
team
• CFD used extensively in the experiment design
• Companion CFD runs for all risk assessment 
experiments
• Publications so far:
• AIAA 2016-1557, AIAA 2017-4127,  
AIAA 2016-4126, NASA TM-2016-219348, etc
• Tasked to perform various parametric studies using 
CFD:
• Effect of support hardware
• Effect of wind tunnel walls on measurements
7
Introduction cont.
• CFD parametric studies approach:
• Run 14x22 empty tunnel
• Grid resolution study
• Tunnel speed calculations
• Solution acceleration approaches
• Run 14x22 with JFM installed
• Run with various support hardware 
included
• Determine effect of wind tunnel walls
8
Introduction: Difficulties discovered
• CFD simulations of 14x22 empty tunnel
• CFD tunnel is very sensitive to changes in back pressure
• Long process: 
• Manual changes to back pressure
• Slow to propagate downstream
• Corner Separation
• CFD simulations with JFM installed
• Determining tunnel speed - calibration point covered by 
model
• Corner separation present in most cases
• Tunnel speed is very sensitive
• Inflow/Outflow BC issues 
9
14x22 Empty Tunnel Studies
• Overset structured grids, built with Chimera Grid Tools
• Coarse (9.3M), Medium (41.6M), Fine (118.7M)
• Overflow 2.2N
• 3rd-Order Roe upwind RHS, ARC3D Beam-Warming scalar pentadiagonal 
LHS
• Low-Mach preconditioning
• Spalart-Allmaras turbulence model + rotational correction + QCR
• Fully Turbulent, Steady State
• Inflow BC: Total Pressure/Temperature (P0, T0)
• Outflow BC: Back Pressure (Pratio = P0/Pexit)
• Mach= 0.2, RE = 2.4 Million
14x22 Overflow Baseline Grid
10
14x22 Tunnel Speed Calculation
• Tunnel Speed Calculation 
• Direct probe at (17.75,0.0,0.0) 
• Calibration point
• Model is often located here
• Calculated using wind tunnel method:
• Uses total pressure & static pressure “probe” values from their locations
• Calibrated equations -> tunnel speed
11
14x22 Tunnel Speed Calculation
11
Grid Calculated Mach Direct Mach Probe
Coarse 0.2023 0.1995
Medium 0.2029 0.2004
Fine 0.2025 0.2000
Mach values are nearly identical: can calculate wind tunnel 
speeds using same method
14x22 Grid Refinement (Overflow)
12
• Mach number of 
tunnel vs iteration
• Tunnel speed is 
calculated using 
pressure probes
Coarse
Fine
Medium
14x22 Grid Refinement (Overflow)
13
Coarse
Fine
Medium
14x22 Grid Refinement (Overflow)
13
• Spikes/drops caused by 
manual changes in back 
pressure
• Each change required 
10,000 steps to “settle”
• Solutions require 100,000 
to 1,000,000+ steps!
Coarse
Fine
Medium
14x22 Grid Refinement (Overflow)
14
Fine
MediumCoarse
14x22 Grid Refinement (Overflow)
14
• Coarse grid tunnel 
speed was extremely 
noisy 
Fine
MediumCoarse
14x22 Grid Refinement
• Red isosurfaces - reverse flow
• Large diffuser separation in Coarse grid
• Tunnel Mach number was “noisy” due to corner 
separation
15
Coarse Medium Fine
Juncture Flow Model with WT walls
16
JFM 8% model with
roll sting and mast
Using medium WT grid
Side View Test Section
Sting
Mast
JFM 8% Conditions 
• RE = 2.4M based on yehudi break chord 21.97 inches
• T = 560 Rankine (hot day in the tunnel, Q~55)
• Mach = 0.2
• Process:
• Speed calculation with WT walls computed with Static/Stagnation pressure 
probe calculations
• Inflow BC: Stagnation T & P, Outflow BC: Pback ratio (iterated)
17
Top View
Side View
Top View
Side View
14x22 with JFM Corner Separation
14x22 JFM
14x22 JFM+Sting
18
AOA 5 degrees
14x22 JFM+Sting+Mast
• Cases were very hard 
to converge
• Mach response to ratio 
changes were erratic
14x22 with JFM Corner Separation
14x22 JFM
14x22 JFM+Sting
19
AOA 5 degrees
14x22 JFM+Sting+Mast
• Most configurations at 
some +AOA had 
corner separation
14x22 Inflow/Outflow BC’s
• Inflow/Exit BC’s are based on inviscid assumptions: 
• Running regions near BC inviscid may help speed up 
convergence
• May reduce corner separation
• Blue sections are run as Inviscid
• Same exit pressure ratio (1.02188) used for both
20
Inviscid Diffuser Extension
Inviscid Inlet + Inviscid Diffuser Extension
14x22 Inviscid BC’s (Overflow)
• Slice down middle of test section, mach contours
• Inviscid Inlet has a slightly lower speed in test 
section
• Very similar results 21
Inviscid Diffuser Extension
Inviscid Inlet + Inviscid Diffuser Extension
14x22 Inviscid BC’s (Overflow)
• Inviscid Inlet suppresses the separation present in the 
corners of the inlet
• Both suppress diffuser corner separation 22
Inviscid Diffuser Extension Inviscid Inlet + Inviscid Diffuser Extension
JFM 8% Installed in 14x22
23
Top View
Side View
• Increment Analysis: Support Hardware, WT Extension
• 14x22 WT: JFM, JFM+Sting, JFM+Sting+Mast (42-46M Grid 
points)
• 14x22 WT Extended: JFM+Sting+Mast (84M-88M Grid Points) 
(Inviscid Diffuser)
• 14x22 WT Extended with inviscid inlet & diffuser (didn’t finish in 
time)
JFM 8% Support Hardware Effect
24
JFM
JFM+Sting
JFM+Sting+Mast
Effect of the 
support 
hardware on:
• Wing/Bubble
• Solution
All results at 
AOA 5 degrees
14x22 JFM Support Hardware Comparison 𝜶=5.0º
14x22 JFM+Sting 14x22Ext JFM+Sting+Mast
14x22 JFM 14x22 JFM+Sting+Mast
25
14x22 JFM ΔCp Comparison 𝜶=5.0º
14x22 JFM
14x22 JFM+Sting
14x22Ext JFM+Sting+Mast
 (base solution) 26
14x22 JFM+Sting+Mast
14x22 JFM Bubble Comparison 𝜶=5.0º
14x22 JFM+Sting 14x22Ext JFM+Sting+Mast
14x22 JFM 14x22 JFM+Sting+Mast
27
14x22 Tunnel Extension Effect
14x22 w/Extension
JFM+Sting+Mast
14x22 wo/Extension
JFM+Sting+Mast
AOA 5 degrees
28
14x22 Tunnel Extension Effect
14x22 JFM+Sting+Mast
AOA 5 degrees
14x22 JFM+Sting+Mast 
w/Extension
Pexit ratio = 1.0196 Pexit ratio = 1.02185
29
1.016
1.017
1.018
1.019
1.02
1.021
1.022
1.023
-10 -7.5 -5 -2.5 0 2.5 5 7.5 10
Ba
ck
	P
re
su
re
	R
at
io
Angle	of	Attack	[deg]
Back	Pressure	Ratio	vs	Angle	of	Attack
WTExt-JFMStingMast
WT-JFMStingMast
WTJFMSting
WT-JFM
14x22 Back Pressure Ratio Mach 0.2
30Back Pressure Ratio = P0/Pexit
14x22 8% JFM Increment Summary
• Support Hardware
• Pressures were very similar for all results
• Bubble size was insensitive to support hardware, and 
tunnel extension (preliminary result) 
• 14x22 WT vs 14x22 WT with Inviscid Extension
• Suppresses the corner separation in the diffuser
• Back pressure does not need to be as high
• Extension Exit Pressure ratio is closer to empty tunnel 
value (1.022) 
• Tunnel speed settles out much faster
• Need to still look at effect of adding Inviscid Inlet on JFM
31
Future Work
32
• Compare CFD WT to CFD Free Air
• Compare with WT data once available
• Cp profiles, oil flows
• Velocity & Reynolds stress profiles
• Automate back pressure ratio (PID controller)
Acknowledgements 
NASA’s Transformational Tools and Technologies (T3) Project
Chris Rumsey and the Juncture Flow committee:
NASA Langley: P. Balakumar, Mark Cagle, Dick Campbell, Jan-
Renee Carlson, Andy Davenport, Kevin Distill, Judy Hannon, 
Luther Jenkins, Bil Kleb, Mujeeb Malik, Cathy McGinley, Joe 
Morrison, Frank Quinto, Don Smith, Sandy Webb
NASA Ames: Henry Lee, Thomas Pulliam, James Bell, Nettie 
Roozeboom, Laura Simurda, Greg Zilliac
Boeing: Mike Beyer, Neal Harrison, Peter Hartwich, Philippe 
Spalart, Tony Sclafani, John Vassberg
AUR: Gwibo Byun and Roger Simpson
Virginia Tech: Aurelien Borgoltz and Todd Lowe
University of Kentucky: Jim Coder
Bill Oberkampf
33
Discussion
34
• How else can we improve modeling with WT walls?
• What do we need to do to this dataset to best help 
CFD community improve their models?
Preliminary CFD Free Air vs CFD WT
35
CFD Free Air
CFD WT
AOA 5 degrees


Simulations of the Nasa Langley 14- by 22-Foot Subsonic Tunnel for the Juncture Flow Experiment

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