Calculation of convective heat flux in the vicinity of the stagnation point for partially ionized gas flow past a body

1972 ◽  
Vol 4 (4) ◽  
pp. 45-51
Author(s):  
O. N. Suslov
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
Convective Heat ◽  
Gas Flow ◽  
Ionized Gas ◽  
Convective Heat Flux ◽  
Flow Past ◽  
Partially Ionized

Schmidt-Boelter Heat Flux Gage Sensitivity Coefficients in Radiative and Convective Environments

2011 ◽  
Author(s):  
James T. Nakos ◽  
Alexander L. Brown
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat ◽  
Radiative Heat ◽  
Sensitivity Coefficient ◽  
Calibration Standard ◽  
Convective Heat Flux ◽  
Sensitivity Coefficients ◽  
Theoretical Sensitivity ◽  
Flux Calibration

Commercial Schmidt-Boelter heat flux gages are always calibrated by using a radiative heat flux source where convection is minimized. This is because one can establish a reliable link to a National Institute of Standards and Technology (NIST) calibration standard. To the authors’ knowledge, no NIST traceable link exists for convective heat flux calibration. When heat flux gages are used in typical applications, convection is often not negligible. It has been common practice to assume that the sensitivity coefficient supplied by the manufacturer also applies for convective environments. This assumption is believed to be incorrect. If incorrect, this would result in uncertainties larger than typically reported (e.g., ±3%). This paper analyzes the heat transfer from an idealized Schmidt-Boelter heat flux gage. The analysis shows that the theoretical sensitivity coefficients in purely radiative and convective environments are not the same and, in fact, differ by the emissivity of the gage surface. The implication of this difference is that the accuracy specification supplied by the manufacturer (typically ± 3%) is not correct for measurement applications where convection is not negligible.

scholarly journals Numerical Study of Rotating Thermal Convection on a Hemisphere

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 185
Author(s):  
Patrick Fischer ◽  
Charles-Henri Bruneau ◽  
Hamid Kellay
Keyword(s):  
Heat Flux ◽  
Shear Layer ◽  
Convective Heat ◽  
Thermal Convection ◽  
Soap Bubble ◽  
Convective Heat Flux ◽  
Benard Convection ◽  
Velocity Equation ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Numerical simulations of rotating two-dimensional turbulent thermal convection on a hemisphere are presented in this paper. Previous experiments on a half soap bubble located on a heated plate have been used for studying thermal convection as well as the effects of rotation on a curved surface. Here, two different methods have been used to produce the rotation of the hemisphere: the classical rotation term added to the velocity equation, and a non-zero azimuthal velocity boundary condition. This latter method is more adapted to the soap bubble experiments. These two methods of forcing the rotation of the hemisphere induce different fluid dynamics. While the first method is classically used for describing rotating Rayleigh–Bénard convection experiments, the second method seems to be more adapted for describing rotating flows where a shear layer may be dominant. This is particularly the case where the fluid is not contained in a closed container and the rotation is imposed on only one side of it. Four different diagnostics have been used to compare the two methods: the Nusselt number, the effective computation of the convective heat flux, the velocity and temperature fluctuations root mean square (RMS) generation of vertically aligned vortex tubes (to evaluate the boundary layers) and the energy/enstrophy/temperature spectra/fluxes. We observe that the dynamics of the convective heat flux is strongly inhibited by high rotations for the two different forcing methods. Also, and contrary to classical three-dimensional rotating Rayleigh–Bénard convection experiments, almost no significant improvement of the convective heat flux has been observed when adding a rotation term in the velocity equation. However, moderate rotations induced by non-zero velocity boundary conditions induce a significant enhancement of the convective heat flux. This enhancement is closely related to the presence of a shear layer and to the thermal boundary layer just above the equator.

scholarly journals Quantifying pyroconvective injection heights using observations of fire energy: sensitivity of spaceborne observations of carbon monoxide

2015 ◽  
Vol 15 (8) ◽  
pp. 4339-4355 ◽  
Author(s):  
S. Gonzi ◽  
P. I. Palmer ◽  
R. Paugam ◽  
M. Wooster ◽  
M. N. Deeter
Keyword(s):  
Heat Flux ◽  
Carbon Monoxide ◽  
Convective Heat ◽  
Biomass Burning ◽  
Environmental Conditions ◽  
Heat Fluxes ◽  
Plume Rise ◽  
Convective Heat Flux ◽  
Active Fire ◽  
Fire Area

Abstract. We use observations of active fire area and fire radiative power (FRP) from the NASA Moderate Resolution Imaging Spectroradiometers (MODIS), together with a parameterized plume rise model, to estimate biomass burning injection heights during 2006. We use these injection heights in the GEOS-Chem (Goddard Earth Observing System Chemistry) atmospheric chemistry transport model to vertically distribute biomass burning emissions of carbon monoxide (CO) and to study the resulting atmospheric distribution. For 2006, we use over half a million FRP and fire area observations as input to the plume rise model. We find that convective heat fluxes and active fire area typically lie in the range of 1–100 kW m−2 and 0.001–100 ha, respectively, although in rare circumstances the convective heat flux can exceed 500 kW m−2. The resulting injection heights have a skewed probability distribution with approximately 80% of the injections remaining within the local boundary layer (BL), with occasional injection height exceeding 8 km. We do not find a strong correlation between the FRP-inferred surface convective heat flux and the resulting injection height, with environmental conditions often acting as a barrier to rapid vertical mixing even where the convective heat flux and active fire area are large. We also do not find a robust relationship between the underlying burnt vegetation type and the injection height. We find that CO columns calculated using the MODIS-inferred injection height (MODIS-INJ) are typically −9 to +6% different to the control calculation in which emissions are emitted into the BL, with differences typically largest over the point of emission. After applying MOPITT (Measurement of Pollution in the Troposphere) v5 scene-dependent averaging kernels we find that we are much less sensitive to our choice of injection height profile. The differences between the MOPITT and the model CO columns (max bias ~ 50%), due largely to uncertainties in emission inventories, are much larger than those introduced by the injection heights. We show that including a realistic diurnal variation in FRP (peaking in the afternoon) or accounting for subgrid-scale emission errors does not alter our main conclusions. Finally, we use a Bayesian maximum a posteriori approach constrained by MOPITT CO profiles to estimate the CO emissions but because of the inherent bias between model and MOPITT we find little impact on the resulting emission estimates. Studying the role of pyroconvection in the distribution of gases and particles in the atmosphere using global MOPITT CO observations (or any current spaceborne measurement of the atmosphere) is still associated with large errors, with the exception of a small subset of large fires and favourable environmental conditions, which will consequently lead to a bias in any analysis on a global scale.

Subsonic electrically quasi-neutralweakly-ionized gas flow past a spherical probe

2006 ◽  
Vol 41 (1) ◽  
pp. 63-70 ◽  
Author(s):  
A. B. Vatazhin ◽  
K. E. Ulybyshev
Keyword(s):  
Gas Flow ◽  
Ionized Gas ◽  
Spherical Probe ◽  
Flow Past
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