1. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 1 Preliminary Numerical Simulation of a Suborbital Experiment to Investigate the Behaviour of Liquid and Gaseous Hydrogen under Compensated Gravity and Non-Isothermal Boundary Conditions Sebastian Schmitt, Michael Dreyer ZARM, University of Bremen Am Fallturm, Bremen, Germany Sebastian.Schmitt@zarm.uni-bremen.de

2. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 2 Motivation Possible Experiment Design Simplification LH 2 H2H2 front view (cut) top view (cut)

3. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Phase Change on Molecular Scale – The Accomodation Coefficient June 13-14, 2013 | Madrid 3 [1] Van P. Carey. Liquid-Vapor Phase-Change Phenomena. Taylor & Francis, Limited, 2008. [2] C.W. Hirt, D Milano, and M.R. Barkhudarov. Modeling phase change and homogeneous bubbles. Technical report, Flow Science, Inc., 2001.

4. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Thermodynamic Observation of the Bubble June 13-14, 2013 | Madrid 4 LH 2 H2H2 cv

5. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 5 Effects of Evaporation and Thermal Expansion dVdV 18 x dV dVdV 21 x dV Phase Change Thermal Expansion For hydrogen expansion rates are in the same range

6. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Expected Effects of RSIZE on Bubble June 13-14, 2013 | Madrid 6

7. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Numerical Model June 13-14, 2013 | Madrid 7

8. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Solver Initial time step: t 0 = 1e-8 s Maximum time step: t max = 1e-5 s Simulation time: t = 20 s Pressure solver:Implicit, GMRES Fluid advection:Split Lagrangian method Two fluid interface slip:Velocity & Temperature activated Momentum advection:2 nd order monotonicity preserving Physics Bubble and phase change:Two-fluid phase change Density evaluation:1 st order Heat transfer: Full energy equation, 1 st order, implicit Surface tension:Explicit Viscosity & turbulence:Viscous flow, laminar June 13-14, 2013 | Madrid 8

9. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity PropertyValue*Unit ρlρl 65.162kg/m 3 c p,l 13.086kJ/kg λlλl 104mW/(m K) ρgρg p/(R T)kg/m 3 c p,g f(T)kJ/kg λgλg f(T)mW/(m K) σ1.24mN/m 2 θ90° h410.57kJ/kg R3.327kJ/(kg K) June 13-14, 2013 | Madrid 9 * All material properties are from: NIST Standard Reference Database 23, Version 9.0.6

10. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity 10 Bubble Rise with Temperature contour June 13-14, 2013 | Madrid

11. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity Outcome June 13-14, 2013 | Madrid 11 Relationship between phase change and RSIZE Exponential for very low values of RSIZE Rise of RSIZE leads to an overshoot High values have little effect on phase change No statement about bubble size

12. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 12 Relationship between bubble size and RSIZE Progression similar to evaporation Only for very little RSIZE in feasible range Little effect of thermal expansion on bubble growth?

13. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 13 Conclusion Phase change is very sensitive for low values of RSIZE Bubble size quickly exceeds the feasible range Stagnation of evaporation with increase of RSIZE Evaporation is steering the bubble growth

14. 13th Annual FLOW-3D Users Conference Center of Applied Space Technology and Microgravity June 13-14, 2013 | Madrid 14 Thank You for Your Attention! The project on which this report is based was supported financially by the German Federal Ministry of Education and Research (BMBF) under grant number 50 RL 1120. The responsibility for the contents of this publication rests with the author(s). Special thanks to Holger Faust for the animation