Stagnation Point Heat Transfer Measurements in Partially Ionized Air

Rose, P. H.; Stankevics, J. O.

doi:10.21236/ad0406269

Cited by 13 publications

(22 citation statements)

References 2 publications

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“…However, the ambipolar diffusion coefficient for the charged particles was computed using Eq. (22) and the limiting forms discussed in that section. The limiting forms for isothermal and nonisothermal plasmas provide the bounds of the diffusion coefficient for the ambipolar condition.…”

Section: Flight-test Data From the Ram-c IImentioning

confidence: 99%

“…The viscosity and thermal conductivity of the mixture were computed from Wilke's semi-empirical mixing rule. 21 The thermal conductivity of the electrons was ignored because the freestream velocity considered in the present study was limited to 10 km/s and, according to Rose and Stankevics, 22 the heat conduction due to electrons does not present a serious engineering problem for flight velocities up to 16 km/s.…”

Section: Transport Effectsmentioning

confidence: 99%

“…The ambipolar diffusion is modeled in the present study per Eq. (22), D a ≈ D I [1 + (T e /T I )]. For the two limiting cases of T e ∼ T I and T e T I , the ambipolar diffusion coefficients of D a = 2D I and D a = D I were used in predicting electron density in the shock layer and near the surface.…”

Section: Vibrational Population Depletion Effects and Diffusion Studiesmentioning

confidence: 99%

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Governing Equations for Weakly Ionized Plasma Flowfields of Aerospace Vehicles

Josyula¹,

Bailey²

2003

Journal of Spacecraft and Rockets

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A generalized set of conservative equations for simulating the flowfield in a hypersonic weakly ionized gas flows is presented. Additional numerical and physical complexities associated with the plasma state are identified and discussed, including the influence of external and space charge fields and the nonequilibrium coupling of reactive and nonreactive collisions. A restricted set of equations is then employed to simulate and analyze the flowfield of an air plasma generated by associative ionization. With use of a seven-species air model, details of the plasma flowfields are presented and compared with available experiments. Refined estimates of dissociation products, which are the precursors to the ionization reaction, are obtained. Specific attention is given to limiting forms of the electron diffusion coefficient and the influence of vibration-dissociation coupling. Details of the chemical reactions in the flowfield influencing the elastic and inelastic collisional energy transfer are reported to highlight the more important species and reaction mechanisms. Nomenclaturefunction of space and time, V/m E e = translational energy of electrons per unit volume, J/m 3 e = total energy per unit mass, J/kg F ela,s = force per unit volume due to elastic collisions, N/m 3 F ele,s = force per unit volume due to electric field, N/m 3 F inela,s = force per unit volume due to inelastic collisions, N/m 3 h 0 = enthalpy of formation, J/kg k = Boltzmann constant, 1.3807 × 10 −23 J/K L = characteristic length, m M = Mach number M = molecular weight, kg/mole M e = electron mass, 9.1094 × 10 −31 kg m = mass, kg N = number density, number/m 3 N = Avogadro's number, 6.02252 × 10 23 /mole p = pressure, N/m 2 Q = energy exchange between modes, J/m 3 s Q rad = radiation heat loss term, J/m 3 s q = charge, C q j = heat flux vector, W/m 2 T = translational temperature, K T eff = effective temperature at which dissociation or ionization reaction is considered, K T v = vibrational temperature, K u j = mass-averaged velocity component of mixture fluid in three dimensions, where j is 1-3 u j s = average or mean velocity of species s in three dimensions, where j is 1-3 m/s V = random or peculiar velocity or diffusion velocity, m/s v j s = velocity of species s in three dimensions, where j is 1-3 m/s X = mole fraction x j = position vector in three dimensions, where j is 1-3 m Z s = ionic valency, −1 for electrons, 1 for single-ionized positive ions = electron or ion flux density, number/m 2 · s ε = elementary electronic charge, 1.6022 × 10 −19 C 0 = permittivity of free space, 8.8542 × 10 −12 F/m η = thermal conductivity coefficient, W/mK d = characteristic temperature of dissociation, K v = characteristic temperature of vibration, K ν = collision frequency, Hz ν * er = effective collision frequency of electrons with diatomic molecules (heavy particles), Hz ρ = total density, kg/m 3 ρ n = state density in the nth vibrational level, kg/m 3 σ = collision cross section, m 2 τ = relaxation time, s τ i j = viscous shear stress, N/m 2 ω pe = el...

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Section: Flight-test Data From the Ram-c IImentioning

confidence: 99%

Section: Transport Effectsmentioning

confidence: 99%

Section: Vibrational Population Depletion Effects and Diffusion Studiesmentioning

confidence: 99%

See 1 more Smart Citation

Governing Equations for Weakly Ionized Plasma Flowfields of Aerospace Vehicles

Josyula¹,

Bailey²

2003

Journal of Spacecraft and Rockets

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“…The direct interaction between a dense plasma and a solid body is treated to some degree in studies related to the atmospheric reentry of space vehicles [1][2][3][4][5]*. Description of the heat transfer in these cases is effected by dimensionless heat transfer parameters [6].…”

Section: The Effect Of Ionization On Heat Transfer To Wires Immersed mentioning

confidence: 99%

The effect of ionization on heat transfer to wires immersed in a highly thermallyionized plasma

Pétrie

Pfender

1972

Wärme- und Stoffübertragung

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Results obtained with a previously developed technique for measuring local heat transfer to bare and ceramic coated metal wires from a dense, highly thermallyionized plasma are presented and compared with theoretical predictions. A free-burning arc in argon at atmospheric pressure provides a plasma in local thermodynamic equilibrium. Wire probes are swept through this plasma in planes parallel to the anode. The wires do not draw a net current from the plasma. Experimental evidence indicates that the layer between the undisturbed plasma and the probe surface is not in chemical equilibrium. The data show that heat transfer . to the wire in this situation is dominated by the energy transport associated with electron and ion partial currents to the probe surface as determined by the potential of the probe with respect to the plasma. The data obtained using this technique provide an experimentally verified model for the heat transfer to wires immersed in a plasma over a wide range of plasma conditions including a 100 percent variation in the degree of ionization.

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“…The test gas was air. The shock tube data are by Rose and Stark, 10 Rose and Stankevics, 11 and Horton and Babineaux. 12 Rose and Stankevicscarried out a speci c analysis to determine both the thermochemical state of air and the effects of catalycity of the surface of the calorimeter.…”

Section: Analysis Of Resultsmentioning

confidence: 99%