ENHANCED NUMERICAL MODELING IN SIMULATION OF A GENERIC PROPELLANT TANK SLOSH BAFFLE

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Gillian Phelps
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Héctor Gutiérrez Mechanical and Aerospace Engineering Department Florida Institute of

1 ENHANCED NUMERICAL MODELING IN SIMULATION OF A GENERIC PROPELLANT TANK SLOSH BAFFLE Sunil Chintalapati Joel M. Faure Ran Zhou Michael Vergalla Dr. Daniel R. Kirk Dr. Héctor Gutiérrez Mechanical and Aerospace Engineering Department Florida Institute of Technology 46 th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit Nashville, TN July 27, 2010

2 OVERVIEW Overview of slosh dynamics Novel link between MathWorks MATLAB &ANSYS FLUENT Demonstration of link and comparison with ground experiment Simulation of generic complex motion maneuver 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

3 Sloshing is detrimental Fluid reorientation Undesirable momentum Coffee slosh example MOTIVATION 6-DOF dynamic mesh model User defined functions Grid options for various situations related to liquid rocket propulsion Regular gravity or microgravity Bulk fluid motion or fluid spatter (droplets) MATLAB-FLUENT link Eliminates use of UDF To include couple motion and force feedback Capable of adding multiple enhancements in a single simulation Figure: Coffee sloshing example Ref: 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

4 BACKGROUND Parametric study of a propellant tank slosh baffle (AIAA-JPC-2008) Two dimensional study of slosh baffle performance in regular and microgravity Identified parameters for evaluating baffle performance Bond number scaling Laminar vs. turbulence modeling Experimental methodology of slosh dynamics 2-DOF motion table Parabolic flight testing Numerical characterization of slosh dynamics 6DOF, Dynamic mesh model FLUENT benchmarked Validated at Florida Tech 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

5 BAFFLE EXPERIMENTAL SETUP Linear Translation in X-axis Motion Table Setup: Tank in Lighting Control box, Work Station, Overview, LabView instrumentation, and New Encoder Position Sensor 7/28/2014 Rotation about Y-axis Figure: Triaxial accelerometer Figure: Gyroangular accelerometer Figure: Encoder position sensor Florida Institute of Technology /Joint Propulsion Conference

6 COMPUTATIONAL SETUP Gambit 2.4 used for geometry creation ANSYS FLUENT 12.1, transient VOF model Geo-reconstruct scheme used for fluid interface tracking Second order discretization for momentum Domain dimensions and statistics Slice of domain depicting structured grid Grid T d (m) T h (m) b h (m) b t (m) b w (m) # cells a cv (m 3 ) Type Grid-study-domain na na na E-06 structured Experimental Tank E-08 structured Microgravity Tank E-05 structured Domain overview 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

7 GRID SENSITIVITY CRITERION 1 of 3 1. Pressure monitor : Monitors static pressure of fluid at specified location GRID SENSITIVITY STUDY MATRIX Grid # Interval Size (m) Total Cells t r (mins) a cv (m 3 ) Mesh Type E-04 structured E-05 structured E-04 structured E-06 structured E-05 structured E-06 structured 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

8 GRID SENSITIVITY CRITERION 2 of 3 2. Fluid interface monitor: Fluid interface is the area of interest for current study, thus is one other parameter for grid sensitivity study GRID SENSITIVITY STUDY MATRIX Grid # Interval Size (m) Total Cells t r (mins) a cv (m 3 ) Mesh Type E-04 structured E-05 structured E-04 structured E-06 structured E-05 structured E-06 structured 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

9 GRID SENSITIVITY CRITERION 3 of 3 3. MATLAB: Slice of domain oriented towards the initial slosh wave is compared with similar slice of different mesh density at same time instance. Results of difference show below Color black depicts area of no difference Color green depicts area difference in fluid interface _ = Grid6 Grid5 Difference 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

10 MATLAB SETUP MATLAB calls ANSYS FLUENT as a function to solve the fluids dynamics aspect of simulation Capable of coupling CFD and any model to solve any number of complex problems Replace the need for FLUENT s User Defined Functions (UDF) with more user friendly programs such as MATLAB The whole process is automated and is controlled by MATLAB 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

11 EXPERIMENT RESULTS 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

12 CFD RESULTS 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

13 Sample: Worst case at 1.9 sec EXPERIMENT- CFD RESULTS Note: Orientation of experimental tank is slightly of x-axis Note: Camera location is along top surface of experimental tank Table: Comparison of experiment and CFD results TYPE EXP(in) CFD(in) Difference (%) Axis height Peak height Wetted wall /28/2014 Florida Institute of Technology /Joint Propulsion Conference

14 Sample: Best case at 3.9 sec EXPERIMENT- CFD RESULTS Table: Comparison of experimental and CFD results TYPE EXP(in) CFD(in) Difference(%) Axis height Peak height Wetted wall /28/2014 Florida Institute of Technology /Joint Propulsion Conference

15 EXPERIMENT- CFD RESULTS 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

16 ENHANCEMENT 1 Simulation time is compromised of motion profile implemented by MATLAB for the first 30 sec Angular velocity vector in FLUENT is in inertial frame The tank is set on a rotating frame with variable angular velocities to induce violent slosh Tank as a moving frame of reference in FLUENT 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

17 MOTION PROFILE ANIMATION 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

18 ENHANCEMENT RESULTS Motion profile successfully implemented by MATLAB into FLUENT Variable angular acceleration to induce violent slosh as a input for motion profile shows massive fluid reorientation in domain Duration of motion profile is 30 seconds Note: Baffle effectiveness is not the critical parameter here 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

19 CONCLUSION & FUTURE WORK Charting a proper approach to grid studies Introducing a novel link between MATLAB and FLUENT Comparison of simulation (MATLAB-FLUENT) with ground slosh experiment Successfully implement complex maneuver similar to a docking/orbit transfer Two way communication and validation of MATLAB-FLUENT link FLUENT solving fluid dynamics part MATLAB solving updated motion profile due to momentum imparted to tank by the fluid Experimental fluid interface and CFD fluid interface mapping Neural network add-on Update time-step based on residual behavior and courant number Reduction in computational run time- faster results Capable of simulation complicated motion profiles Structural complexities i.e. Isogrid, Toughened ribbed structures used as inner lining for fuel tanks Extends heat transfer surface area, mitigates slosh wave 7/28/2014 Florida Institute of Technology /Joint Propulsion Conference

Set up and solve a transient problem using the pressure-based solver and VOF model.

Set up and solve a transient problem using the pressure-based solver and VOF model. Tutorial 18. Using the VOF Model This tutorial was run using ANSYS FLUENT 12.1. The results have been updated to reflect the change in the default setting of node-based smoothing for the surface tension