1. 1 CLiFF - Convective Liquid Flow Firstwall Liquid Walls: Concepts, Modeling, and Experiments Neil B. Morley University of California, Los Angeles Presented to: Chamber Technology Peer Review UCLA, April 26, 2001

2. LW Concepts, Modeling and Experiments2 APEX LW Modeling and Experiment Contributors UCLA - N. Morley, S. Smolentsev, A. Ying, K. Gulec, M. Abdou, M. Youssef, N. Ghoneim, S. Sharafat, H. Huang, T. Sketchley, B. Freeze*, D. Gao*, M. Dagher*, J. Burris* PPPL - B. Kaita, R. Woolley, L. Zakharov, S. Jardin IFS - M. Kotschenreuther, H. Rappaport SNL - M. Ulrickson, R. Nygren, T. Tanaka, J. McDonald LLNL - R. Moir, T. Rognlien UW - M. Sawan ORNL - B. Nelson, P. Fogarty, S. Zinkle ANL - D. Sze INEEL - K. McCarthy UIUC - D. Ruzic, J-P. Alain* *Indicates student

3. LW Concepts, Modeling and Experiments3 LW Concepts, Modeling and Experiments: Outline Liquid wall concepts for fusion Modeling development, progress and results Experiment planning and progress Summary

4. LW Concepts, Modeling and Experiments4 Plasma-Liquid Interactions Several LW “classes” identified during idea exploration phase TLW - Thick Liquid Walls. Nearly all solid surfaces covered by a thick (~40-50 cm) liquid layer: e.g. flowing poloidally on curved back- wall. CLiFF - Convective Liquid Flow First-wall. Thin (~1-2 cm) liquid layer flowing on curved back-wall that protects nearly all solid surfaces from surface heat/particle flux. EMR, Magnetic Propulsion, others: Electromagnetically restrained or pumped flows similar to TLW or CLIFF ideas with applied or induced current in LM to push flow against back-wall or pump liquid along flow direction. Early schematic of an TLW-EMR idea proposed by Woolley PPPL Symmetry axis

5. LW Concepts, Modeling and Experiments5 Other Possible LW Concepts that show promise SWIRL: Swirling Thick Liquid Vortex (~40-50 cm). A subset of TLW developed for cylindrical vessels like in the FRC or IFE SOAKER HOSE: Banks of bleeding tubes with liquid metal forced radially away from plasma between gaps in tube banks with applied EM forces. Divertor: Various concepts exist for a liquid divertor - research pursued in concert with ALPS program Many others ideas were proposed and assessed in idea exploration phase of APEX LW for FRC Chamber using SWIRL

6. LW Concepts, Modeling and Experiments6 LW have many design options and tradeoffs

7. LW Concepts, Modeling and Experiments7 Scientific Issues for Liquid Walls 1. Thermofluid Issues -Interfacial Transport and Turbulence Modifications at Free-Surface -Hydrodynamic Control of Free-Surface Flow in Complex Geometries, including Penetrations, Submerged Walls, Inverted Surfaces, etc. -MHD Effects on Free-Surface Flow for Low- and High-Conductivity Fluids 2. Effects of Liquid Wall on Core Plasma -Discharge Evolution (startup, fueling, transport, beneficial effects of low recycling - Plasma stability including beneficial effects of conducting shell and flow 3. Plasma-Liquid Surface Interactions - Limits on operating temperature for liquid surface

8. LW Concepts, Modeling and Experiments8 APEX has followed the Snowmass Recommendations for LW Research Fundamental Design, Theory and Modeling: This is needed for all concepts and experiments and should include: 3D Hydrodynamics/Free surface codes with appropriate turbulence and MHD models Turbulent, wavy surface, and droplet heat and mass transport modeling Plasma impurity transport modeling System modeling and concept analysis and design Thermal-Fluid Flibe Free Surface Flow Experiments: A series of scaled hydrodynamic experiments is needed to simulate Flibe liquid wall dynamics and heat transfer. LM-MHD Free Surface Flow Experiments: A series of magneto-hydrodynamic experiments in magnetic fields representative of the tokamak and other magnetic configurations is needed. These experiments should explore both passive free surface flow in relevant fields and field gradients, and the active electro-magnetically pumped concepts as well. Also, a series of experiments is needed in which heat transfer is studied in liquid metal free surface flows with relevant MHD effects. Flibe Chemistry and Handling Experiments: Experience in handling and utilizing high temperature Flibe is needed before it can be realistically developed for reactor applications. Such experiments will focus on safety, corrosion, TF control, target debris recovery, and tritium handling.

9. LW Concepts, Modeling and Experiments9 Outline Liquid wall concepts for fusion Modeling development, progress and results Experimental planning and progress Summary

10. LW Concepts, Modeling and Experiments10 Hydrodynamics Free Surface Phenomena Electromagnetism Passive & Active Scalar Transport -Interfacial Transport and Turbulence Modifications at Free-Surface - Hydrodynamic Control of Free-Surface Flow in Complex Geometries, including Penetrations, Submerged Walls, Inverted Surfaces, etc. - MHD Effects on Free-Surface Flow for Low- and High- Conductivity Fluids Many interacting phenomena Predicting LW behavior requires understanding underlying phenomena

11. LW Concepts, Modeling and Experiments11 Design Focused - Approximate models for Engineering Scale Flows Develop “laminarized” (LM) or RANS-turbulent (FLIBE) flow models with geometric simplifications to reduce complexity of Navier-Stokes and Maxwells Eqs. Use these modeling tools to explore flow phenomena, test numerical model formulations, and provide some basis for quantitative development of APEX/ALIST/ALPS LW designs Integrated Understanding Focused - Complete treatment of interacting phenomena Develop nearly complete 3D simulations including all magnetic field, electric current and velocity components and some or all scales of turbulence, complex geometries and free surfaces. Simulate full interactions of LW flows - possibly in reduced parameter ranges APEX is using a two-pronged modeling approach to investigate LWs

12. LW Concepts, Modeling and Experiments12 High conductivity - e.g. liquid metals Effect of strong magnetic fields and complex geometries on flow control, surface waves, and velocity profiles Effect of velocity profiles and surface waves on heat transfer Low conductivity - e.g. Flibe and other molten salts Effect of strong magnetic fields on turbulence and surface and wall heat transfer Effect of complex geometry on flow control and surface waves For thick liquid Flibe flows - MHD effects on flow control must also be considered Model development is specific to conductivity of working liquid

13. LW Concepts, Modeling and Experiments13 Axisymmetric models: 2 to 2.5-D V-P-B variables developing, time dependent flows height function or VOF method 3 components of B, 3 components of V, applied current Spatially/temporally varying toroidal magnetic field Fully Developed Models: 1 to 2D V-B Effects of conducting walls and 2 components of B Linear gradients of field components and applied current Linear stability analysis Non-Symmetric Averaged Models: 1.5D V-P-B Developing, time dependent flows Height function method 2 components of B - Hartmann drag, field gradients, and opposing Lorentz force are included through averaging LM-MHD model development has increased understanding of LW flows and numerical methods for prediction Free surface flow velocity jets produced from MHD interaction - UCLA calculation Design-focused models have been providing basic description of the flows for design - and for more advanced numerical formulations

14. LW Concepts, Modeling and Experiments14 Example Results: Quantification of dividing wall conductivity and separation requirements based on the calculations of constant-B MHD effects Quantification of allowable wall-normal field in flows with axisymmetry Surface temperature in Li, Sn CLiFF, based on reduced velocity profiles Numerical confirmation of the magnetic propulsion idea in toroidal field Flow predictions in NSTX fields of Li flow on centerstack, divertor and outboard midplane in varying toroidal magnetic field New Questions: Is flow through 1/R toroidal field stable? Can applied current stabilize it? How serious are the toroidal movement and resultant bulk instabilities in Li CLiFF due to interaction of streamwise currents with wall-normal fields? How strong is the drag coming from wall-normal field variations and startup fields in NSTX? MHD Plasma/Liquid coupling? LM-MHD modeling has produced a steady stream of important results… and more questions!

15. LW Concepts, Modeling and Experiments15 Gradients in toroidal field produces stream- wise electric current flow (shown below) If flow is thin, drag effects may not be sever, but velocity profile can be modified But pressurization, pushing liquid outward at free surface may effect stability Understanding MHD field gradient effects on drag and stability Upper section Lower section

16. LW Concepts, Modeling and Experiments16 Understanding multi-component MHD effects and predicting flow profiles Flow drag is very sensitive to surface- normal fields. Especially if flow is axisymmetric or has field gradients Interaction with streamwise currents can induce a toroidal motion as well. Incorporation of these effects into design is key for feasibility

17. LW Concepts, Modeling and Experiments17 Magnetic Propulsion is one way to use MHD forces to overcome drag B Z1 B Z2 Increase of the field gradient, (B Z1 - B Z2 )/L, results in the higher MHD drag (blue curves 1-6) Applying an electric current leads to the magnetic propulsion effect and the flow thickness decrease (red curves 7-9) In calculations: L=20 cm; h 0 =2 cm; U 0 =5 m/s Innovative idea from L. Zakharov (PPPL) where applied current is used to induce pressure gradient that propels flow!

18. LW Concepts, Modeling and Experiments18 Extension of 3D free surface codes to include limited MHD Effects caused by wall-normal magnetic field in flows with axial symmetry Effects caused by a spatial and temporal variations in toroidal magnetic field in flows with axial symmetry Alternate heat flux boundary condition at free surface for improved accuracy Fully 3D field effects currently under development Improved understanding has led to extension of state-of-the-art in free surface modeling 2-D simulation of flow development under strong toroidal magnetic field gradient - UCLA

19. LW Concepts, Modeling and Experiments19 Preliminary 3D results for lithium flow in a wall-normal field gradient Flow direction 3D Tools just now being applied to cases with strong MHD forces Required to address fusion reactor environment Careful testing and benchmarking is required to ascertain validity of modeling results 3-D simulation of flow development under wall normal magnetic field gradient - UCLA

20. LW Concepts, Modeling and Experiments20 Jet start-up without / with grid adaption - HyperComp Phase I SBIR Grid adaption or multi-resolution for surface and boundary layer resolution Parallel Algorithms for tractable computing times 3D Unstructured Meshes for complex geometries High-order advection and free surface tracking algorithms APEX cooperation with SBIR is leading to even greater modeling capabilities

21. LW Concepts, Modeling and Experiments21 Turbulence modification in strong magnetic fields Two-equation turbulence models (the so-called k-e model) with include terms describing the effect of the magnetic field and presence of free surface Development of DNS and LES models that can directly simulate the turbulence development and dissipation under free surface and MHD conditions Modeling Approach for LW MHD turbulence in low conductivity fluids Flow Control in complex geometries Issues of penetrations, nozzles, mixing promoters, etc. addressed with 3D VOF codes

22. LW Concepts, Modeling and Experiments22 Strong redistribution of turbulence by a magnetic field is seen. Frequency of vortex structures decreases, but vortex size increases. Stronger suppresion effect occurs in a spanwise magnetic field Free surface approximated as a free slip boundary. Work proceeding on a deformable free surface solution. “DNS of turbulent free surface flow with MHD at Ret = 150” - Satake, Kunugi, and Smolentsev, Computational Fluid Dynamics Conf., Tokyo, 2000 Ha=20, Streamwise Ha=0 Ha=10, Spanwise Extending the state-of-the-art in DNS with MHD and free surface effects

23. LW Concepts, Modeling and Experiments23 Comparison of UCLA model to experimental data MHD K-  TURBULENCE MODEL Extending the state-of-the-art in RANS with MHD and free surface effects 1.5-D MHD K-  Flow Model unsteady flow height function surface tracking turbulence reduction near surface is treated by specialized BCs effect of near-surface turbulence on heat transfer modeled by variation of the turbulent Prandtl number

24. LW Concepts, Modeling and Experiments24 Significant results from continuously advancing MHD-k  model Other Examples... 2 to 3 cm, 10 m/s turbulent Flibe flow in ARIES RS type geometry can be established Mean MHD effects in Flibe CLiFF are negligible, but mean MHD effects in thick Flibe flow are important Design parameters for FLIHY flibe hydrodynamics simulation experiments Surface Temperature Predictions for CLiFF Slight changes in turbulent Prandtl number (due to surface waviness or increased surface turbulence) can dramatically affect surface temperature: 40  C difference seen in Flibe CLiFF case Flat surface Bulk Surface temperature change in a 2 MW/m 2 heat flux Wavy surface

25. LW Concepts, Modeling and Experiments25 3D Hydrodynamic simulations needed to investigate flibe flow control Geometric complexity requires 3D simulations using tools like Flow3D, HIMAG, and Telluride - penetrations - mixing promoters - nozzles Prediction of gross flow motion for thin low conductivity flows (friction factors modified for MHD and curvature effects) Flow around circular penetration - HIMAG

26. LW Concepts, Modeling and Experiments26 Calculated velocity and surface depth SWIRL Concepts: Structural cylinders with a liquid vortex flow covering the inside surface. Applicable to FRC, ST and IFE Computer Simulation: 3-D time- dependent Navier-Stokes Equations solved with RNG turbulence model and VOF algorithm for free surface tracking Results: Adhesion and liquid thickness uniformity (> 50 cm) met with a flow of V axial = 10 m/s, V ,ave = 11 m/s Modeling flow for alternative plasma confinement schemes

27. LW Concepts, Modeling and Experiments27 Next steps for liquid wall modeling Complex geometry LM flow control around penetrations, jet streams emerging from nozzles, etc. 3D and 2D (or helical) turbulence and its effect on surface heat transfer Temporal and spatially varying fields 3D LM-MHD in complex geometries and supply lines Coupling of MHD LWs to MHD plasma physics Experimental verification MHD LES and DNS with free surface 3D MHD LES and complex geometry Collaboration with physics

28. LW Concepts, Modeling and Experiments28 LW Concepts, Modeling and Experiments: Outline Liquid wall concepts for fusion Modeling development, progress and results Experimental planning and progress Summary

29. LW Concepts, Modeling and Experiments29 Experimental research approach based on key issues and flexibility Experimental data for verification of the numerical predictions and testing of ideas in conjunction with the model development efforts Two flexible free surface flow test stands at UCLA have already been planned, designed and constructed M-TOR facility for LM-MHD flows in complex geometry and multi-component magnetic fields FLIHY Facility for molten salt turbulent flow simulation and surface heat and mass transfer measurements Other small scale testing at PPPL and UIUC to use in-house capabilities to look at specific issues MTOR- Designed in collaboration among UCLA, PPPL and ORNL

30. LW Concepts, Modeling and Experiments30 Exploring Free Surface LM-MHD in MTOR Experiment Flexible user facility to study: Toroidal field and gradient effects: Free surface flows are very sensitive to drag from toroidal field Hartmann walls and 1/R gradient 3-component field effects on drag and stability: Complex drag and stability issues arise with field gradients, 3-component fields Effect of applied electric currents: Magnetic Propulsion and other active electromagnetic restraint and pumping ideas Geometric Effects: axisymmetry, expanding / contacting flow areas, inverted flows, penetrations NSTX Environment simulation: module testing and design Conceptual view of midplane and divertor experiments for NSTX module MTOR Magnetic Torus and LM Flowloop

31. LW Concepts, Modeling and Experiments31 Time-of-flight Current Status MTOR Facility: beginning first experiments PPPL DC power supply tested Water coolant loop installed Small Ga loop (1L) operating 16 L Ga alloy currently shipping for use with EM pumping loop already at UCLA Safety consultation with GA completed Ultrasound diagnostics working, automatic data acquisition still under development Typical ultrasound plot with and without liquid metal present (top) Ga flowing in open channel (bottom)

32. LW Concepts, Modeling and Experiments32 With Magnetic Field - reduction in wave height Without Magnetic Field 10 cm f=10Hz Surface waves height reduction by Magnetic Field explained by linear MHD theory with ohmic dissipation, from H. Ji PPPL Basic Science research initiative collaborating with APEX laser reflection data

33. LW Concepts, Modeling and Experiments33 MTOR Coil wiring Development of cost-effective facilities with education mission LIMIT experiment at UIUC Flowing Ga section for MTOR SNL Test of IR MTOR built with recycled components with heavy student involvement FLIHY dual use with Jupiter-II monies from Japan Tabletop LIMIT experiment at the UIUC to show axisymmetric center- stack flow for NSTX Sharing and collaboration on diagnostic systems is required by small budgets. E.g. Ultrasound, PIV, IR and visible high speed photography

34. LW Concepts, Modeling and Experiments34 Free Surface Heat Transfer using Low Conducting High Prandtl Number Fluid Turbulence at and near the free (deformable and wavy) surface ITurbulence at and near the free (deformable and wavy) surface Heat transfer enhancement techniques II Heat transfer enhancement techniques Understanding Basic Hydraulic Phenomena For Liquid Wall Design Demonstration of liquid wall concepts using hydrodynamically scaled experiments IDemonstration of liquid wall concepts using hydrodynamically scaled experiments Accommodation of penetrations IIAccommodation of penetrations Flow recovery system design IIIFlow recovery system design Closed channel heat transfer enhancement for Jupiter-II Collaboration Quantitative turbulence measurements of complex channel and MHD effects I Quantitative turbulence measurements of complex channel and MHD effects penetration un-wetted back wall Deflected liquid layer FLIHY Facility is designed for multiple applications of Flibe flow Flow around elliptical penetration with no backwall topology modifications - UCLA simulation

35. LW Concepts, Modeling and Experiments35 FLIHY will allow exploration of flow control and interfacial transport Large scale test sections with water/KOH working liquid will generate LW flows around penetrations Tracer dye and IR camera techniques will be used to measure interfacial transport at free surface PIV and LDA systems for quantitative turbulence comparison to DNS for JUPITER-2 Collaboration FLIHY Experiment at UCLA - Interfacial Transport Test

36. LW Concepts, Modeling and Experiments36 FLIHY experiment pre-analysis relies on k-e modeling for design Test section length and flow height determined to allow fully developed flow regime based on K  calculations 2 m Require IR heater power estimated with K  calculations to achieve measurable surface temperature rise

37. LW Concepts, Modeling and Experiments37 Penetration of dye from free surface can be used to infer heat transfer charateristics - Reynolds Analogy Profile of dye penetration (red dots) Local free surface (blue dots) flow direction ~2 m/s Dye Diagnostics for Interfacial Mass Transport Measurements

38. LW Concepts, Modeling and Experiments38 Water jet hot droplets Hot droplet penetrating jet Dynamic Infrared measurements of jet surface temperature Impact of hot droplets on cold water jet (~8 m/s) thermally imaged in SNL/UCLA test

39. LW Concepts, Modeling and Experiments39 Observe the behavior of flow: i.e. attachment, wave trains, flow depth near sidewall - High Speed Camera 1000 frame/s, 512*256 pixel - Strobe with variable frequency Measure flow rate and fluid depth for comparison to numerical models - Pressure sensors, flow meter and thermocouples - Ultrasonic and laser height measurement technique Capability to mount various penetrations sections Penetrations on curved surfaces, scaled to CLiFF similarity

40. LW Concepts, Modeling and Experiments40 JUPITER-II Thermofluid Task Objectives 1. Understand underlying Science and Phenomena for low conductivity, high Prandtl liquid flow and heat transfer through: a. Conducting experiments using Flibe simulant b. Modeling and analysis of fundamental phenomena 2. Compare experimental and modeling results to provide guidance and database for designs and next generation stage of larger experiments 3. Identify and assess new innovative techniques for enhancement of heat transfer (a major feasibility issue for Flibe designs)

41. LW Concepts, Modeling and Experiments41 Main Areas of Collaborative Scientific Interest between JUPITER and APEX Turbulent Hydrodynamics and heat transfer near solid walls and at liquid/vacuum interfaces of Flibe simulants flowing in closed channels and swirl pipes, and on flat and curved plates, with and without MHD effects Identification of instrumental and experimental techniques: Radiant heating, laser and ultrasonic surface topology reconstruction, infra-red temperature measurements, laser Doppler and particle image velocimetry, others. Development and benchmarking of new modeling techniques: MHD turbulence interactions and turbulence wall and free surface interactions in k-e, DNS, LES

42. LW Concepts, Modeling and Experiments42 MHD and complex pipe shape effects on turbulence and high Pr heat transfer Pipe and free surface test section on improved FLIHY Low temperature and transparent structures /windows allow for optical turbulence diagnostics: Particle Image Velocimetry Dye, IR, Ultrasound, and Hot-film anemo- meters may also be used Thermofluid Test sections for JUPITER-II

43. LW Concepts, Modeling and Experiments43 TASK 1-1-B Thermofluid Experiments and Modeling Schedule for 6 years 2001, 42002, 42003, 42004, 42005, 42006, 4 Heat Transfer Experiment with HTS Test sections; Swirl tube, Packed bed tube etc. Numerical Analysis of heat transfer enhancement HTS Thermo-fluid Experiments & Analysis (Tohoku Univ.) MHD Experiments (UCLA) Thermofluid Flow Experiments FLI-HY Loop (UCLA) Modeling (DNS, LES) Pipe and free surface flows with/without Magnetic Fields C&R Continue with Heat Transfer? Continue with MHD, or another option? Continue with Flibe Loop? Non MagnetWith Magnet Visualization and Velocity Measurement Experiments (Straight tube, Swirl tube, Packed bed tube, etc. Surface stability and visualization experiments Heat Transfer Experiment indicated by HTS Experiment Surface heat transfer experiments Visualization and Heat Transfer experiments, same as 2001-03 under Magnetic Field (Swirl Tube, Packed Bed Tube, etc.) Large Integrated Flibe Loop Conceptual Design Evaluation

44. LW Concepts, Modeling and Experiments44 Summary Liquid walls are an innovative approach to fusion technology APEX is analyzing LW feasibility with a suite of modeling tools and predictive capabilities. APEX approach: emphasize phenomena and underlying science utilize and extending state-of-the-art tools in CFD develop unique capabilities where none have existed previously collaborate with world experts in turbulence and MHD APEX has developed experimental capabilities to begin investigation of LW flows. APEX approach: low cost, high flexibility facilities joint education and research mission collaboration among US and international communities Milk drop splash using VOF - Kunugi