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4th annual SU2 Conference, Varenna, Italy, October 23-25 2023

Faculty of Engineering and Technology

Department of Aerospace Engineering

Assessment of Thermochemistry modelling for Hypersonic Non-Equilibrium flow in Martian atmosphere (CO2-species) using SU2-NEMO and Mutation++

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A U NACHIKETH KUMAR, DR. GOPALAKRISHNA NARAYANA

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Presentation Outline

  • Introduction
  • Motivation
  • Aims and Objectives
  • Geometry
  • Freestream Conditions

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  • Solver
  • Numerical Modelling
  • Results
  • Conclusion
  • Reference

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Introduction

Non-Equilibrium Flow

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  • The high kinetic energy of the freestream gets converted into internal energy of the gas across the shock wave, creating a very high temperature in the shock layer.

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  • These temperatures are high enough to cause vibrational excitation, dissociation and recombination of gas molecules and ionization, so called high temperature effects and real gas effects.

Atmosphere Re-entry and majority of hypersonic high enthalpy flows are often characterized by Non Equilibrium Flows

Figure 2: Flow region in shock layer

Figure 1: Flow features of blunt re-entry vehicle [2]

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Motivation

  • The prediction of the surface heat flux is still of great significance and challenge in Non-equilibrium hypersonic flow. As high-temperature flows consists complex vibrational and chemical kinetics.

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  • Given the relatively low characteristic vibrational temperature of the CO2 molecule, it is expected that excited vibrational modes play a significant role in Non-equilibrium flow features

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  • This phenomenon represents a severe constraint on the design of Martian hypervelocity vehicles.

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  • The influence of real gas effects on this design limiting phenomenon are hither to poorly understood

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Courtesy: NASA

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Aims and Objectives

  • Model aerothermodynamic environment of the flow field existing during Martian atmospheric entry with CO2 as gas species

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  • Extend the understanding of nonequilibrium effect on heat flux in CO2 dominated flows by means of numerical modeling and simulation

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  • Validation of SU2-NEMO modelling capabilities for high enthalpy, reacting flows with Experimental data

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  • Assessment of heat flux augmentation due to different thermochemical numerical modelling assumptions

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  • Code to code comparison with FLUENT solver and SU2 NEMO Solutions

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  • To evaluate the heat transfer predicting capability of the SU2 solver.

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Dept of Aerospace Engineering MSRUAS

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Geometry

Large angle blunt cone body

All dimensions are in mm

Figure 3: Geometry of 120 blunt cone with base radius of 50 mm and nose radius of 25 mm [1].

Figure 4: Geometry of 60 blunt cone with base radius of 40 mm and nose radius of 35 mm[1].

60 APEX ANGLE BLUNT CONE

120 APEX ANGLE BLUNT CONE

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Freestream Conditions

Nozzle flow properties

Test Case (Enthalpy)

3.6 MJ/kg

Mach Number, M∞

5.87

Pressure, P∞ (kPa)

0.572

Temperature T∞(K)

739.85

Density ρ∞ (kg/m3)

0.0041

Velocity V∞ (m/s)

2364.6

Table 1: Properties in nozzle supply region for HST[1]

Test Case (Enthalpy)

3.6 MJ/kg

Pressure, Po (kPa)

10233.5

Temperature To(K)

2877

Density ρo (kg/m3)

14.12

Table 2: Freestream conditions for HST-3 (From Experimental paper) [1] .

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Figure 5: Schematic of IIsc FPST (HST-3) [1]

Test Gas: Co2, Carbon Dioxide

Nozzle Supply

Test model

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Freestream Conditions

Gas species composition and reaction

Species

Mole Fraction

CO2

0.889

CO

0.071

O2

0.035

O

0.0012

C

4e-13

Reactions

A (mole/cm s k)

n

Ea (cal/mole)

CO2=CO+O

1.29E14

0.5

103923

CO=C+O

9.18E19

-3.1

256343

CO2+O=CO+O2

2.17E14

0

67132

O2=O+O

1.14E16

-1

118018

C+O2=CO+O

1.2E14

0

3994

Table 4: Reaction set for CO2 Test Gas [1]

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Table 3: Mole fraction of species in the nozzle supply region predicted using CHEMKIN [1].

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Solver

NEMO and Mutation ++

SU2-NEMO

(NonEquilibrium MOdels solver)

CFD Software

Local State

Physicochemical properties

Physicochemical models

Algorithms

Databases

Thermochemical Library

Mutation ++ consists algorithms for the computation of thermodynamic properties, transport (viscosity, thermal conductivity and diffusion) and chemical kinetic gas properties, finite rate chemistry in chemical non-equilibrium

Mixture File

Reaction File

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Figure 6: Solver workflow

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Numerical Modelling

Grid Details and boundary conditions

Axisymmetric Axis

Fairfield

Outlet

Wall

Axisymmetric Axis

Outlet

Fairfield

Wall

Boundary conditions

Specifications

Farfield

Pressure Farfield( P=0.572 kPa, T=739.85K)

Outlet

Supersonic Outlet

Wall

Isothermal wall (T=300K)

Axis

Axisymmetric axis

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Grid Size: 0.5 Million

Figure 9a and 9b: Near wall inflation layer

Figure 7: 120 deg Blunt cone domain

Figure 8: 60 deg Blunt cone domain

Y plus=1

First layer spacing=1e-6

Table 5: Boundary Conditions

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Numerical Modelling

Solution Methodology

Solver Parameter

Methodology

SOLVER

NEMO_NAVIER_STOKES

FLUID_MODEL

MUTATIONPP

GAS_MODEL=

CO2_5_rm { C O CO CO2 O2 }

GAS_COMPOSITION

{ 1.13706e-13, 4.544e-4, 0.047066, 0.925971, 0.026507}

VISCOSITY_MODEL

SUTHERLAND

NUM_METHOD_GRAD

WEIGHTED_LEAST_SQUARES

CONV_NUM_METHOD_FLOW

AUSM

CONV_NUM_METHOD_TURB

SCALAR_UPWIND

TIME_DISCRE_FLOW

EULER_EXPLICIT

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Table 5: Configuration file settings

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Results

Mutation ++ on Gas Species at P=10233.5 kPa in Nozzle supply region

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C02

C0

02

0

C

C02

C0

02

0

C

Figure 10: Species mole fraction variation

Figure 11: Species Diffusion flux variation

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Results

Mach Contour - 120 angle, Surface pressure comparison

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Figure 12a: EQUILIBRIUM

Figure 12b: NON- EQUILIBRIUM

Reaction

Figure 12c: NON- EQUILIBRIUM

Frozen

Thermochemical model

Shock Stand off Distance

Equilibrium

4 mm

Non-Equilibrium Reaction

2.2 mm

Non-Equilibrium Frozen

2.2 mm

Table 6 : Shock stand off distance in 120 blunt cone

Figure 13: Surface pressure for 120 blunt cone

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Results

Temperature contour - 120 angle, Heat flux comparison

Figure 14a: EQUILIBRIUM

Figure 14b: NON- EQUILIBRIUM Reaction

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Translational Temperature (Top)

Vibrational Temperature (Bottom)

Translational Temperature (Top)

Vibrational Temperature (Bottom)

Translational Temperature (Top)and(Bottom)

Figure 14c: NON- EQUILIBRIUM Frozen

Figure 15: Surface Heat flux over 120 blunt cone

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Results

Mach Contour - 60 angle, surface pressure comparison

Figure 16a: EQUILIBRIUM

Figure 16b: NON- EQUILIBRIUM

Reaction

Figure 16c: NON- EQUILIBRIUM

Frozen

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Thermochemical model

Shock Stand off Distance

Equilibrium

4.5 mm

Non-Equilibrium Reaction

3 mm

Non-Equilibrium Frozen

3 mm

Table 7: Shock stand off distance in 60 blunt cone

Figure 17: Surface pressure for 60 blunt cone

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Results

Temperature Contour - 60 angle, , Heat flux comparison

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Figure 18a: EQUILIBRIUM

Figure 18b: NON- EQUILIBRIUM Reaction

Figure 18c: NON- EQUILIBRIUM Frozen

Translational Temperature (Top)

Vibrational Temperature (Bottom)

Translational Temperature (Top)

Vibrational Temperature (Bottom)

Translational Temperature (Top)and(Bottom)

Figure 19: Surface Heat flux over 60 blunt cone

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Results

Stagnation line properties - 120 angle

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Figure 22: Degree of thermal NON- EQUILIBRIUM Reaction (Top) Frozen(Bottom)

Figure 20: Species mass fraction

Figure 21: Ttr and Tve temperature profile along stagnation line in 120 blunt cone

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Results

Stagnation line properties - 60 angle

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Figure 25: Degree of thermal NON- EQUILIBRIUM Reaction (Top) Frozen(Bottom)

Figure 24: Ttr and Tve temperature profile along stagnation line in 60 blunt cone

Figure 23: Species mass fraction

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Results

Surface Pressure distribution; Code to Code with fluent

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Figure 26: Surface pressure over 120 blunt cone

Figure 27: Surface pressure over 60 blunt cone

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Results

Surface Heat Flux distribution; Code to Code with fluent

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Figure 28: Surface Heat flux over 120 blunt cone

Figure 29: Surface Heat flux over 60 blunt cone

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Conclusion

Remarks and future scope

  • Heat flux analysis demonstrated significant differences for equilibrium , non-equilibrium and frozen Thermochemistry assumptions
  • Heat flux and surface pressure was overpredicted by equilibrium model. Reaction and frozen model showed no significant changes while predicting pressure , but exhibited considerable differences in predicting the heat flux.
  • Large amount of discrepancy was found near the stagnation region where the shocks are stronger.
  • Equilibrium model predicted higher shock standoff compared to Non-equilibrium models.
  • Code to code results comparison between FLUENT and SU2-NEMO solvers confirms SU2 having good heat flux prediction capability in nonequilibrium conditions.
  • No significant amount of thermal non-equilibrium was observed behind the blunt shock associated with 120 apex blunt cone, indicating low relaxation time of Co2 molecule.
  • State of population inversion in vibration level was found in conical section of 60 degree Apex blunt cone.

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Future Scope

  • Implementation of Catalytic wall

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  • Numerical analysis on 3d Model

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  • Computation of Radiative heat flux, Gas Surface Interaction (GSI)

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References

Literature paper

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  1. Experimental Investigation of High-Speed Aerothermodynamics Over Large Angle Blunt Cone Forebodies Entering Martian, Mohammed Ibrahim. S, PhD Thesis.
  2. Hypervelocity aerothermodynamics of blunt bodies including real gas effects, Park, Gisu, Publication Date: 2010 DOI: https://doi.org/10.26190/unsworks/23325
  3. Mutation++: MUlticomponent Thermodynamic And Transport properties for IONized gases in C++ James B. Scoggins ∗ , Vincent Leroy2 , Georgios Bellas-Chatzigeorgis3 , Bruno Dias, Thierry E. Magin von Karman Institute for Fluid Dynamics, B-1640 Rhode-St-Genèse, Belgium
  4. SU2-NEMO: An Open-Source Framework for High-Mach Nonequilibrium Multi-Species Flows WT. Maier, J T. Needels ,C Garbacz ,FMorgado , J J. Alonso and M Fossati, https://doi.org/10.3390/aerospace8070193
  5. Effect of thermal nonequilibrium on the shock interaction mechanism for carbon dioxide mixtures on double-wedge geometries, Physics of Fluids 34, 026108 (2022), https://doi.org/10.1063/5.0078233
  6. Characterization of nonequilibrium shock interaction in CO2-N2 flows over double-wedges with respect to Mach number and geometry, Physics of Fluids (June 2023)
  7. Numerical Study of Shock Interference Patterns for Gas Flows with Thermal Nonequilibrium and Finite-Rate Chemistry, AIAA SciTech Forum
  8. Evaluation of radiative heat transfer for interplanetary re-entry under vibrational nonequilibrium conditions
  9. Nonequilibrium aerothermodynamics for a capsule re-entry vehicle, Engineering Applications of Computational Fluid Mechanics Vol. 3, No. 4, pp. 543–561 (2009).

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THANK YOU

Stay healthy

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