Experimental Study of Initial Condition Dependence for Turbulence Design in Shock Driven Flows
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IWPCTM 12, Moscow, Russia 12 July 2010 1/14 Experimental Study of Initial Condition Dependence for Turbulence Design in Shock Driven Flows Sridhar Balasubramanian , K. Prestridge, B.J. Balakumar, G. Orlicz P-23 Neutron Science and Technology Group, Extreme Fluids Team Los Alamos National Laboratory Acknowledgments : Malcolm Andrews, Ray Ristorcelli, Rob Gore, Fernando Grinstein & Akshay Gowardhan Research supported by Los Alamos National Laboratory Directed Research and Development Program (LDRD-DR)
description
Experimental Study of Initial Condition Dependence for Turbulence Design in Shock Driven Flows. Sridhar Balasubramanian , K. Prestridge, B.J. Balakumar, G. Orlicz P-23 Neutron Science and Technology Group, Extreme Fluids Team Los Alamos National Laboratory. - PowerPoint PPT Presentation
Transcript of Experimental Study of Initial Condition Dependence for Turbulence Design in Shock Driven Flows
IWPCTM 12, Moscow, Russia12 July 2010
1/14Experimental Study of Initial Condition Dependence for Turbulence Design in Shock Driven Flows
Sridhar Balasubramanian, K. Prestridge, B.J. Balakumar, G. Orlicz
P-23 Neutron Science and Technology Group, Extreme Fluids Team Los Alamos National Laboratory
Acknowledgments: Malcolm Andrews, Ray Ristorcelli, Rob Gore, Fernando Grinstein & Akshay Gowardhan
Research supported by Los Alamos National Laboratory Directed Research and Development Program (LDRD-DR)
IWPCTM 12, Moscow, Russia12 July 2010
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How is shock-driven (Richtmyer-Meshkov) turbulence affected by initial conditions?
• Buoyancy-driven turbulence can be affected at late-time by initial conditions, and memory of the IC’s are not lost (Dimonte et al., Phys Fluids 2004, Ramaprabhu et al., JFM 2005).
• Carefully imposed initial conditions effect the growth rate of turbulent Rayleigh-Taylor (R-T) mixing (Banerjee & Andrews, 2009, Ramaprabhu et al., 2005, Dimonte et al., 2004, Mueschke, 2004).
• Work has not yet been done to test the dependence of initial conditions on shock-driven turbulent flows.
IWPCTM 12, Moscow, Russia12 July 2010
3/14Current shock tube configuration allows diagnostic access for simultaneous PIV/PLIF measurements
• Layer Configuration: Light-Heavy-Light (Air-SF6-Air)
• Atwood Number = 0.67
• Incident Shock Mach Number = 1.2
• Primary Wavelength, = 3.6 mm
• PLIF Resolution ~ 54 m/pixel
•(to resolve scalar concentration gradients)
•PIV Resolution ~ 156 m/vector
Nozzle to create curtain
IWPCTM 12, Moscow, Russia12 July 2010
4/14New, longer test section allows observation of late-time flow structures
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Initial Condition
New Test Section (L~0.45m)
Incident shock
Reflected shock
Expansion fan
Reflected Expansion fan
IWPCTM 12, Moscow, Russia12 July 2010
5/14New stereo PIV diagnostic has been added to capture 3-D velocity field in a plane
Side view of IC’s
End view of the IC’s
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IWPCTM 12, Moscow, Russia12 July 2010
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X mm
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m)
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V m/s-0.438169
-0.574201
-0.710233
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Frame 001 24 Mar 2010 C:Experiments7PIVExpLD01aAnalysisPIVShot08.L.vec | C:Experiments7PIVExpLD01aAnalysisPIVShot09.L.PIV through the initial conditions shows the exit and peak velocities of the curtain for input into simulations
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Only select vectors shown for clarity
IWPCTM 12, Moscow, Russia12 July 2010
7/14Detailed IC measurements are critical to understanding the sensitivity of the late-time flow to initial conditions
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3-D Numerical ICsSF6 Volume Fraction
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Experimental velocity profiles at 9 vertical planes
I A(1 Bcoskx)
1 Be y 2 2 /(1a coskx )2
A=0.50, B=0.198, k=1745.3, a=-0.0398, =835.6
Experimental concentration profiles at 20 mm from nozzle exit
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Centerline of curtain
IWPCTM 12, Moscow, Russia12 July 2010
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Dependence of growth patterns and mixing width on initial conditions in RM unstable fluid layers. Physica Scripta 2008. Balakumar, Orlicz, Tomkins, Prestridge
We can control the initial conditions and observe late-time modes and turbulence after reshock
IC formed by nozzle geometry
Reshocking late-time structures
IWPCTM 12, Moscow, Russia12 July 2010
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Can amplitude & wavelength in IC’s allow us to predict the late-time flow behavior?
Varicose curtain, Reshocked at 615µs, (Balakumar et al. POF 2008)
We know that morphologies with multiple wavelengths, such as this, lead to turbulence upon reshock.
Will either of these morphologies become turbulent upon reshock??
Question: Can we predict the onset and nature of the turbulence and somehow link that to the initial conditions??
Reynolds number 4000 at t=565 s
12,000 at t=800 s
/Re hhh
/Re hkk
IWPCTM 12, Moscow, Russia12 July 2010
10/14The power spectral density gives us a metric for when the flow has enough modes to become turbulent upon reshock
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PSD
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Inte
nsity
0s80s130s180s230s280s530sTransition?
No transition?
2-D FFT of concentration signal (avg over span)
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cur
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Widths of k=1.5 peaks
IWPCTM 12, Moscow, Russia12 July 2010
11/14A series of experiments was performed to test the predictions of turbulent transition from the PSD analysis
Reshock times
90 µs
170 µs
280 µs
FIRST SHOCK RESHOCK
Can we quantify these observable differences?
IWPCTM 12, Moscow, Russia12 July 2010
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The PSD of structures after reshock show a broadening and loss of features indicating transition to turbulence
10-1 100 101 10210-4
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ixel
Inte
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t=90st=170st=280st=600s
Differences in the amount of mixing are seen between early time reshock (90s, 170 s) and late time reshock (280 s, 600 s).
Reshock timings
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I/<I>
Reshock at late times gives lower value of I suggesting
that there is more mixing
2-D FFT of concentration signals, 250 µs after reshock
IWPCTM 12, Moscow, Russia12 July 2010
13/14First 3-D simulations of the gas curtain capture many of the large-scale features, but validation is ongoing
Reshock at 90 µs, Experiment & Simulation
Reshock at 170 µs, Experiment & Simulation
3-D ILES simulations performed at LANL by Akshay Gowardhan & Fernando Grinstein
3-D Initial Conditions
IWPCTM 12, Moscow, Russia12 July 2010
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Sinuous initial conditionsShocked once
We can form complex initial conditions using new nozzle designs that will become turbulent after first shock, instead of after reshock
Varicose initial conditionsReshocked at 90µsWavelength=3.6mmAmplitude=3.2mm
(sinuous data from Balakumar et al., 2008, PhysicaScripta)
Wavelength=7mmAmplitude=6.5mm
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Time (s)
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reshock @90sBalakumar et al., offset by b= 0.49 mm(Physica Scripta, 2008)
IWPCTM 12, Moscow, Russia12 July 2010
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Summary & Future Plans
• Measured 3-D characteristics of our well-controlled experimental initial conditions, providing (for the first time) enough constraints on 3-D simulations for IC sensitivity studies.
• Preliminary PLIF measurements have helped us understand which multi-mode conditions will lead to the development of turbulence.
• Velocity field measurements (PIV) of the turbulence will allow us to characterize the turbulent fluctuations to determine the extent of the impact of the initial modes on the turbulence quantities.
• Feasibility of designing multi-mode nozzles with initial conditions that will transition to turbulence upon first shock.
