Marsell, Brandon

NASA Technical Reports Server

JOHN f. KENNfDY SPACE aNTER 
https://ntrs.nasa.gov/search.jsp?R=20130011592 2019-08-31T00:29:40+00:00Z
Agenda 
JOHN E KENNEDY SPACE CENTER 
• Introduction 
• Problem 
• Background 
• Experiment 
• Star ccm+ CFD model 
• Results 
• . Conclusion 
2 
Introduction 
JOHN F. KENNEDY SPACE CENTER 
• Launch Services Program 
- Provide leadership, expertise and cost effective services in the 
commercial arena to satisfy agency wide (NASA) space 
transportation requirements and maximize the opportunity for 
mission success 
- Interface between launch service provider (commercial) and NASA 
spacecraft 
- Requires engineering success 
• Mission Analysis Division 
- Verify and validate mission engineering/analysis 
- Conduct any analysis required by NASA's unique missions 
- Reduce ·technical risk to NASA missions 
3 
Problem 
JOHN F. KENNEDY SPACE CENTER 
• Fuel Slosh 
- Liquid propellants account for most of the mass on a launch vehicle 
- During flight, these liquids "slosh" back and forth within the tanks 
- This sloshing motion causes forces on the vehicle which must be 
accounted for in the flight software 
- Both frequency and damping rate for all liquid propellant tanks must 
be accurately predicted in order to create an efficient autopilot design 
- The idea is to keep the rocket flying straight! 
» This will lead to engineering success 
• Typical propellant tanks on NASA missions 
- 2 on booster stage 
- 2 on upper stage 
- 1-16 tanks on payload 
4 
Background 
JOHN F. KENNEDY SPACE CENTER 
• Guidance Navigation and Controls (GN&C) analyses use 
simplified mechanical analog models 
- Spring mass system 
- Pendulum system 
• These simplified models require 
parameters as inputs 
- Pendulum mass 
- Fixed mass 
- Pendulum length 
- Hinge point 
- Fixed mass location 
---
Spmg I DampeI"{ 
CamImaIioo 
--
-
• These parameters vary as a function of fill level 
5 
Background 
JOHN F. KENNEDY SPACE GNTER 
• ' How to derive these parameters 
- Experimental data 
» Expensive 
» Time consuming 
» Lots of data reduction necessary 
- CFD 
» Quick 
» Inexpensive 
» Simple 
- Analytical Methods 
» Very easy to apply 
» Only valid with simple geometry 
• CFD must first be validated 
- Producing engineering success 
6 
Experiment 
JOHN F. KENNEDY SPACE CENTER 
• Carried out at Embry-Riddle 
Aeronautical University 
• Simplified case 
- 8 inch diameter sphere 
- Water 
- 60% fill level 
- Linear excitation 
- Step impulse and hold 
- No breaking waves 
Experimental Results 
L ........•.. .1 "h. _ _ 
0.6 ; ... , ................ ;............. .. -
0.4 
~ 0.2 
6 
QI 0 e 
0 : : . . 
LL -0.2 : .. ... . .... . ...... . 
-0.4 
-0.6 
-0.9 
-1
0 
: 
2 4 6 8 10 12 14 16 
Time (s) 
Star-CCM+ Model 
JOHN F. KENNEDY SPACE CENTER 
• Same geometry was modeled using Star-CCM+ 
Volume of Fluid (VOF) 
» Phase 1 = water 
» Phase 2 = air 
Implicit unsteady 
» 2nd order Time 
» Timestep 0.0025 s 
» Total time 20 s 
Gravity 
» 19 
Constant density (incompressible) 
» 997.561 kg/mJ\3 - water 
» 1.18415 kg/mJ\3 - air 
Three dimensional 
!6 eightinchsphere.aeooo 
. 0 Ceometry 
t [J Contlnu, 
.. . Wesh 1 
t • Phy,lc, 1 
, [J Nod.l, 
t ~ Eul.rian Nu~lphas. 
t [J Eul.rian Phases 
... c:l Phase! 
.. [J Phas.2 
~ Gradl.nts 
~ Gravity 
~ 1m puett Unsteady 
~ L .... ln ... 
" Nultlphan Equation of Stale 
.. W ~uttlphlSe InterlCtlon 
.. 8 MultiphaSt Mi~urt 
W Segreg&ted ~Iow 
• Thrte Dimensional 
~ Volum. of Flu id (VOF) 
0- CJ Reference Valuu 
.. CI Inttll.l Condttlons 
t [J R'gion, 
, • Regionl 
t [J Boundaries 
.. . Detautt Boundary 
0- a Fea.urt Curves 
.. D Mesh Conditions 
0- 0 Mesh Values 
• CJ Physics Conditions 
.. CJ Physics VaJuu 
.. (J Derived Pvu 
. + (J Solvers 
fi, Implicit Unnudy 
00 " Segregated Flow 
... Ii< S.g .. gll.d VOF 
t (J Stopping Crit.rI, 
~ Nu:Jmum Inner herulons 
~ Naxlmum Phy,lcai Tim. 
~ Maximum Steps 
~ StopFIl. 
a Solution Histones 
.. a Solution VI.ws 
~ [J RepOri' 
.. 0 Monitors 
t CI P1ot, 
.. ~ ForceX Monitor Am 
.. ~ ForceY Monitor Aot 
.. ~ FoneZ Monitor ptDt 
.. Rulduals 
o-[J 
.. Cl Representations 
• Cl Tools 
Star-CCM+ Model 
JOHN f KENNEDY SPACE CENTER 
• Mesh 
- Used simple (new shape part) sphere 
- Surface remesher 
- Trimmer Mesh 
» Works well with VOF formulation 
» Need high resolution throughout domain 
- Prism layer mesher for accurate 
viscous damping 
- 3.1 M cells 
• Boundary Condition 
- 1 region 
» Walls 
» No-slip 
9 
Star-CCM+ Model 
JOHN F. KENNEDY SPACE CENTER 
• Stopping Criteria 
- Maximum inner iterations = 10 
» Reduced residual by at least 2 orders of magnitude 
- Maximum physical time = 20 s 
- Maximum steps disabled 
• Reports/monitors/plots 
- Fluid forces on tank walls 
» Pressure and viscous 
» X, Y, Z direction 
» Plot every time step 
• Initial condition 
- Fluid velocity = 0.065 m/s 
Star CCM Resu Its 
0.8 .. " 
0.6 . 
0.4 . ,. , " '.. .. .. .. .. " " "" '" " " ..... 
......... 0.2 ' .. , .. , . '., ' 
~ 
Q) 0 , .... " .. 
e 
o 
l.L -0.2 
Results 
JOHN F. KENNEDY SPACE CENTER 
Star CCM Results Comparison 
StarCCM+ 
0 .8 
0.6 
0 .4 
0.2 
.--.. 
Z 
......-.. 
Q) 0 0 
..... 
0 
LL 
-0 .2 
-0.4 
-0.6 
-0 .8 
-1 
2 0 4 6 8 
Time (8) 
10 12 14 16 
Results Frequency 
JOHN f KENNEDY SPACE CENTER 
to'". _______ -, ________ ~--------_r--------II---~FIT~EX~pe~rim~e~nt~F~o~~e~x----r_------~--------~--------_r--------~ 
S 10.2 
~ It, ... __ -.Mf(ffl", 
to·
4 L---------.l-----------!---------+--------+---------}-------16~------~7--------_t8 --------!9~------~10 023 
Frequency (Hz) 
_______ -. ________ ~---------,--------~----~F~IT~C~FD~F~o~~e~x~----r_------~--------_r---------r------~ to'~ 
2.026 
3.589 
lo~L-------1-----------!---------~3~------~---------t5--------16~------_77--------_}8--------!9~------~10 
o 2 Frequency (Hz) 
Results Frequency 
JOHN f KENNEDY SPACE GNTER 
• difference roughly 5% 
• Very sensitive to fill level 
- Experiment was filled using fluid volume 
- CFD initialized using fill level converted from volume 
- Frequency content in "stinger"? 
13 
Damping Ratio 
JOHN f. KENNEDY SPACE CENTER 
• Logarithmic decrement Il. 
- ~=In(peak oscillation I peak one cycle later) 
• Damping ratio V 
- Y= M2TT 
- 2.9% difference 
- Very difficult to calculate 
properly 
Damping Ratio 
Experiment 0.004002 
. 
Star ccm+ 0.003887 
Oscillation Peaks 
04 .. . ............ ......... ......................... . 
Z 0.2 ................. ' .' 
'-" 
G) 0 
~ 
o 
LL -0.2 
-04 : ...... : .... : ..... , .....•....... : ..... ........... : .. 
-0.6 ' ' ... ;. .. .. ...... 
-0.8 ....... .. .... ... -
-1 ..' ......... ...... ............... . .. 
o 6 8 10 12 14 16 18 20 
Time (s) 
14 
Conclusion 
JOHN F. KENNEDY SPACE CENTER 
• Star-CCM+ validated for low amplitude, simple geometry slosh 
modeling 
• Both frequency and damping rate match fairly well 
- Frequency off a bit more than desired but that could be caused by 
inaccurate fill procedures during experimental testing 
- Further research will be carried out to investigate the causes 
• Increases LSP confidence in this method for slosh calculations 
• Will add to LSP's engineering success! 
15 


Experimental Validation of Star CCM+ for Liquid Container Slosh Dynamics

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