A Navier-Stokes solver for high speed equilibrium flows and application to blunt bodies

Prabhu, Ramadas K.; Stewart, James R.; Thareja, Rajiv R.

doi:10.2514/6.1989-668

Cited by 22 publications

(13 citation statements)

References 5 publications

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“…This is the physical behavior you would expect for a blunt body bow shock when comparing results using perfect gas properties to equilibrium air properties [Anderson 1989]. within the numerical convergence criteria used in the two simulations and the ability of the author to read the plots provided by Prabhu (1989) From Figure 4.2 it can be seen that using perfect gas properties causes the temperature in the stagnation region to be more than twice that using equilibrium air properties. This occurs since the perfect gas model does not account for all the modes of energy storage of the molecules.…”

Section: Inviscid Blunt Bodymentioning

confidence: 94%

“…To verify the inviscid part of the AVUS code the results are compared to the results of Prabhu et al (1989) for a two-dimensional blunt body. To verify the viscous part of the code, results are compared to those of Rosen (1991) for supersonic and hypersonic laminar flow over a flat plate, and to those of Tannehill et al (1990) for hypersonic, laminar flow over a two-dimensional wedge and axisymmetric cone.…”

Section: Adding Chemical Equilibrium To Avusmentioning

confidence: 99%

“…To validate that the equilibrium air chemistry was added to the AVUS code properly, the published results of several investigators were used. To verify the inviscid part of the new AVUS code, results have been compared to the work of Prabhu et al (1989) …”

Section: Adding Chemical Equilibrium To Avusmentioning

confidence: 99%

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Study of the Issues of Computational Aerothermodynamics Using a Riemann Solver

Henderson

2008

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This work is part of a project to more accurately model hypersonic flow. A number of issues in hypersonic flow are addressed.The first issue addressed is that of air properties at increased temperatures. In particular the thermodynamic and transport properties of chemical equilibrium air are found for temperatures up to 30,000 K for a pressure range from 1x10 −4 to 100 atm. This work provides properties at slightly higher temperatures for the lower pressure region than can be found in the literature. This work also covers adding equilibrium air chemistry to the computational fluid dynamics computer code known as AVUS.The second issue addressed is commonly referred to as the carbuncle phenomenon. The carbuncle phenomenon is a numerical instability that affects the capturing of strong shocks when using a Riemann solver with low numerical dissipation. The carbuncle phenomenon manifests itself in the inability to compute uniform flow conditions downstream of a normal or nearly normal shock. Prior work has been done in this area to accurately capture strong shocks; and great progress has been made in reducing the effects of the carbuncle phenomenon. Even with these improvements the heat transfer profiles in the stagnation region still show some distortion from small upstream perturbations convected downstream to the wall. It has been determined that the grid quality in the region of the shock is a major factor in the inability of Riemann solvers to accurately capture the flow in the stagnation region. For this reason this work performs a grid study and makes recommendations as to what types of structured grids should be used to accurately capture strong shocks and predict iii heat transfer profiles at the body surface. This grid study shows that some types of grids suffer more than others from the carbuncle problem. The reason for this is the numerical dissipation that is introduced from the numerical routine. This work shows that grid aspect ratio and the alignment of the grid to the flow can be used to reduce the effects of the carbuncle phenomenon. This work also shows that another mechanism for the carbuncle phenomenon is the alignment of the grids with the shock. The heat transfer profile cannot be properly captured if the grid is not aligned well with the shock.The third issue addressed in this work is the domain of applicability of the perfect gas model, the equilibrium air model, the nonequilibrium air model, and the thermo-chemical nonequilibrium air model. A computational study is carried out using AVUS to determine the regions of applicability of these air models for a blunt body at various velocities and altitudes. This type of altitude-velocity plot has already been produced by previous researchers, but the dividing lines between the different gas models were found using residence times. This work looks at temperature and heat transfer profiles for a blunt body in a high speed air flow to determine the dividing lines between the regions of applicability of the different air models. Unlike the previous wo...

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Section: Inviscid Blunt Bodymentioning

confidence: 94%

Section: Adding Chemical Equilibrium To Avusmentioning

confidence: 99%

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Study of the Issues of Computational Aerothermodynamics Using a Riemann Solver

Henderson

2008

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“…within the numerical convergence criteria used in the two simulations and the ability of the author to read the plots provided by Prabhu (1989) From Figure 4.2 it can be seen that using perfect gas properties causes the temperature in the stagnation region to be more than twice that using equilibrium air properties. This occurs since the perfect gas model does not account for all the modes of energy storage of the molecules.…”

mentioning

confidence: 99%

Effects-Based Operations at the Operational Level of War: Exploring the Living System Alternative

Dees¹

2008

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-RB-WP-TR-2008-3133 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTESPAO Case Number: WPAFB 08-3904; Clearance Date: 02 Jul 2008. Report contains color. ABSTRACTThis work is part of a project to more accurately model hypersonic flow. A number of issues in hypersonic flow are addressed. The first issue addressed is that of air properties at increased temperatures. Thermodynamic and transport properties of chemical equilibrium air are found for temperatures up to 30,000 K for a pressure range from 1x10 -4 to 100 atm. This work also covers adding equilibrium air chemistry to the computational fluid dynamics computer code known as AVUS. The second issue addressed is the carbuncle problem. A grid study is performed and recommendations as to what types of structured grids should be used to reduce the carbuncle problem are made. Grid aspect ratio and the alignment of the grid to the flow can be used to reduce the effects of the carbuncle phenomenon. Another mechanism causing the carbuncle phenomenon is the alignment of the grids with the shock. The third issue addressed is the domain of applicability of the perfect gas model, equilibrium air model, nonequilibrium air model, and thermo-chemical nonequilibrium air model. A computational study is carried out using AVUS to determine the regions of applicability of these air models for a blunt body at various velocities and altitudes.Full ABSTRACT (full)This work is part of a project to more accurately model hypersonic flow. A number of issues in hypersonic flow are addressed. The first issue addressed is that of air properties at increased temperatures. In particular the thermodynamic and transport properties of chemical equilibrium air are found for temperatures up to 30,000 K for a pressure range from 1x10 -4 to 100 atm. This work provides properties at slightly higher temperatures for the lower pressure region than can be found in the literature. This work also covers adding equilibrium air chemistry to the computational fluid dynamics computer code known as AVUS. The second issue addressed is commonly referred to as the carbuncle phenomenon. The carbuncle phenomenon is a numerical instability that affects the capturing of strong shocks when using a Riemann solver with low numerical dissipation. The carbuncle phenomenon manifests itself in the inability to compute uniform flow conditions downstream of a normal o...

show abstract

“…procedure to generate equilibrium air thermodynamic properties that were then curve ®tted to simulate numerically high-temperature shock tube¯ows. As another representative example, Prabhu et al 3 and Yee et al 4 use the Srinivasan curve ®ts for their numerical predictions of inviscid and viscous hypersonic¯ows. If a set of curve ®ts in turn depends on exponential correlations for the equilibrium constants, then when improved correlations become available, the curve ®ts will have to be revised.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of equilibrium air by an exact two-equation model for Euler and Navier-Stokes CFD algorithms

Iannelli

1997

Int. J. Numer. Meth. Fluids

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A Navier-Stokes solver for high speed equilibrium flows and application to blunt bodies

Cited by 22 publications

References 5 publications

Study of the Issues of Computational Aerothermodynamics Using a Riemann Solver

Study of the Issues of Computational Aerothermodynamics Using a Riemann Solver

Effects-Based Operations at the Operational Level of War: Exploring the Living System Alternative

Thermodynamic properties of equilibrium air by an exact two-equation model for Euler and Navier-Stokes CFD algorithms

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