Multiscale Part-Spectrum k-Distribution Database for Atomic Radiation in Hypersonic Nonequilibrium Flows

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Ankit Bansal ◽  
Michael Modest
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Gauss Quadrature ◽  
Distribution Data ◽  
Data Generation ◽  
Full Spectrum ◽  
Stagnation Line ◽  
Cpu Time ◽  
Quadrature Scheme ◽  
Nonequilibrium Flows

An accurate and compact part-spectrum k-distribution database has been developed for the two most important radiating species N and O encountered in hypersonic nonequilibrium flows. The database allows users to calculate the desired full-spectrum k-distributions through look-up and interpolation, providing an efficient means to perform radiative transfer calculations. A detailed methodology of the k-distribution data generation is presented. An optimized Gauss quadrature scheme is implemented for reducing the size of the database. The accuracy of the database is determined by comparing part-spectrum emissivities with those obtained from line-by-line calculations. The application of the database to construct full-spectrum k-distributions at arbitrary gas states is discussed. Heat transfer results for the stagnation line of the Stardust vehicle are discussed and CPU-time studies are presented, demonstrating the accuracy and efficiency of the k-distribution database.

Narrow-Band k-Distribution Database for Atomic Radiation in Hypersonic Nonequilibrium Flows

2009 ◽  
Author(s):  
Ankit Bansal ◽  
Michael F. Modest ◽  
Deborah Levin
Keyword(s):  
Narrow Band ◽  
Distribution Data ◽  
Nonequilibrium Flow ◽  
Data Generation ◽  
Full Spectrum ◽  
Important Species ◽  
Radiative Fluxes ◽  
Cpu Time ◽  
Nonequilibrium Flows ◽  
The Cost

Full-spectrum k-distribution (FSK) and multi-group FSK approaches make it possible to evaluate radiative fluxes at a fraction of the cost needed for line-by-line calculations. However, the required k-distributions need to be assembled from accurate absorption coefficient data for each flow condition, which is computationally expensive. An accurate and compact narrow-band k-distribution database has been developed for the most important species encountered in hypersonic nonequilibrium flow. The database allows users to calculate desired full-spectrum k-distributions through look-up and interpolation. Strategies for k-distribution data generation are outlined. The accuracy of the database is tested by comparing narrow-band mean absorption coefficients and narrow-band emissivities with those obtained from line-by-line calculations. Application of the database to construct full-spectrum k-distributions accurately and efficiently is discussed, and results from a number of heat transfer calculations and cpu-time studies are presented.

Hybrid Full-Spectrum Correlated k-Distribution Method for Radiative Transfer in Nonhomogeneous Gas Mixtures

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Gopalendu Pal ◽  
Michael F. Modest ◽  
Liangyu Wang
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Computational Cost ◽  
Gas Mixtures ◽  
New Method ◽  
Gas Temperature ◽  
Full Spectrum ◽  
Participating Media ◽  
Distribution Method ◽  
Combustion Gases

The full-spectrum k-distribution (FSK) approach is a promising model for radiative transfer calculations in participating media. FSK achieves line-by-line (LBL) accuracy for homogeneous media at a tiny fraction of LBL’s high computational cost. However, inhomogeneities in gas temperature, total pressure, and component-gas mole fractions change the spectral distribution of the absorption coefficient and can cause inaccuracies in the FSK approach. In this paper, a new hybrid FSK method is proposed that combines the advantages of the multigroup FSK (MGFSK) method for temperature inhomogeneities in a single gas species and the multiscale FSK (MSFSCK) method for concentration inhomogeneities in gas mixtures. In this new hybrid method, the absorption coefficients of each gas species in the mixture are divided into M spectral groups depending on their temperature dependence. Accurate MGFSK databases are constructed for combustion gases, such as CO2 and H2O. This paper includes a detailed mathematical development of the new method, method of database construction, and sample heat transfer calculations for 1D inhomogeneous gas mixtures with step changes in temperature and species mole fractions. Performance and accuracy are compared to LBL and plain FSK calculations. The new method achieves high accuracy in radiative heat transfer calculations in participating media containing extreme inhomogeneities in both temperature and mole fractions using as few as M=2 spectral groups for each gas species, accompanied by several orders of magnitude lower computational expense as compared to LBL solutions.

Application of the Cumulative Wavenumber Approach for Modeling Radiative Transfer in H2O Under Non-Isothermal and Non-Homogeneous Conditions

2002 ◽  
Author(s):  
Vladimir P. Solovjov ◽  
Brent W. Webb
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Radiative Transfer ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Local Spectrum ◽  
Full Spectrum ◽  
Model Predictions ◽  
Spectrum Correlation ◽  
Spectral Database

Recently, the cumulative wavenumber approach was formulated and its viability demonstrated in predictions of radiative heat transfer in high temperature CO2. The approach allows for local spectrum correlation, rather than full-spectrum correlation as commonly done previously. This work reports on the generation of cumulative wavenumber data for H2O, and explores solutions using the cumulative wavenumber approach for water vapor (balance nitrogen) in homogeneous/non-isothermal media, and extends the technique to non-homogeneous/non-isothermal scenarios. Model predictions are compared with rigorous line-by-line benchmark integration of the Radiative Transfer Equation, with the same spectral database (HITEMP) used in both model and line-by-line benchmark predictions.

A New Hybrid Full-Spectrum Correlated k-Distribution Method for Radiative Transfer Calculations in Nonhomogeneous Gas Mixtures

2007 ◽  
Author(s):  
Gopalendu Pal ◽  
Michael F. Modest
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Computational Cost ◽  
Gas Mixtures ◽  
New Method ◽  
Gas Temperature ◽  
Full Spectrum ◽  
Participating Media ◽  
Distribution Method ◽  
Combustion Gases

The full-spectrum k-distribution (FSK) approach is a promising model for radiative transfer calculations in participating media. FSK achieves line-by-line (LBL) accuracy for homogeneous media at a tiny fraction of LBL’s high computational cost. However, inhomogeneities in gas temperature, total pressure and component-gas mole fractions change the spectral distribution of the absorption coefficient and can cause inaccuracies in the FSK method. In this paper, a new hybrid FSK method is proposed that combines the advantages of the multi-group FSK (MGFSK) method for temperature inhomogeneities in a single gas specie and the multi-scale FSK (MSFSK) method for concentration inhomogeneities in gas mixtures. In this new hybrid method the absorption coefficients of each gas specie in the mixture are divided into M spectral groups depending on their temperature dependence. New and accurate MGFSK databases are constructed for combustion gases, such as CO2 and H2O. This paper includes a brief mathematical development of the new method, method of database construction and sample heat transfer calculations for 1-D inhomogeneous gas mixtures with step changes in temperature and species mole-fractions. Performance and accuracy are compared to LBL and traditional FSK calculations. The new method achieves high accuracy in radiative heat transfer calculations in participating media containing extreme inhomogeneities in both temperature and mole fractions using as few as M = 2 spectral groups for each gas specie, accompanied by several orders of magnitude lower computational expense as compared to LBL solutions.

Heat Transfer Spectroscopy and “Heat Transfer-Distance” Curves

2008 ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Sheng Shen ◽  
Gang Chen
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Atomic Force Microscope ◽  
Near Field ◽  
Surface Force ◽  
Casimir Forces ◽  
Distance Curve ◽  
Transfer Distance ◽  
Atomic Force ◽  
Order Of Magnitude

Thermal radiative transfer between objects as well as near-field forces such as van der Waals or Casimir forces have their origins in the fluctuations of the electrodynamic field. Near-field radiative transfer between two objects can be enhanced by a few order of magnitude compared to the far-field radiative transfer that can be described by Planck’s theory of blackbody radiation and Kirchoff’s laws. Despite this common origin, experimental techniques of measuring near-field forces (using the surface force apparatus and the atomic force microscope) are more sophisticated than techniques of measuring near-field radiative transfer. In this work, we present an ultra-sensitive experimental technique of measuring near-field using a bi-material atomic force microscope cantilever as the thermal sensor. Just as measurements of near-field forces results in a “force distance curve”, measurement of near-field radiative transfer results in a “heat transfer-distance” curve. Results from the measurement of near-field radiative transfer will be presented.

Computational Study on Radiative Aerothermodynamics of a Reentry Space Vehicle

2021 ◽  
Author(s):  
Qi Li ◽  
Sijun Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Computational Study ◽  
Space Vehicle ◽  
The Body ◽  
Stagnation Region ◽  
Convective Flux ◽  
Transit Times ◽  
Key Issues ◽  
Nonequilibrium Flows

Abstract Under hypersonic flight conditions, a vehicle travelling through the atmosphere could excite the air that flows around the body to very high temperatures as the kinetic energy of the vehicle is dissipated to the gas. Depending on the flight velocity, various chemical reactions will be produced behind a shock wave for stagnation region. These reactions greatly change the properties of air and cause considerable deviation from those of a thermally and calorically perfect gas. A vehicle flying through the higher altitude of the atmosphere at high velocities may also experience thermal non-equilibrium since the lower density reduces the collision frequency and the high velocity results in smaller transit times for the air molecules. Under such extremely thermal circumstances, the heat transfer by convection and radiation around a vehicle has been one of key issues for thermal protection system (TPS). In this paper, the computational aerothermodynamics with fully coupled radiative heat transfer is developed. To validate the proposed approach, it is employed to simulate the thermal and chemical nonequilibrium flows over Stardust. The computed results on the reentry space vehicle reveal both of convective flux and radiative flux are in good agreements with other predicted results.

Wake-Induced Unsteady Stagnation-Region Heat Transfer Measurements

1994 ◽  
Vol 116 (1) ◽  
pp. 29-38 ◽  
Author(s):  
P. J. Magari ◽  
L. E. LaGraff
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Edge Region ◽  
Isentropic Compression ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Wide Range ◽  
Mach Numbers

An experimental investigation of wake-induced unsteady heat transfer in the stagnation region of a cylinder was conducted. The objective of the study was to create a quasi-steady representation of the stator/rotor interaction in a gas turbine using two stationary cylinders in crossflow. In this simulation, a larger cylinder, representing the leading-edge region of a rotor blade, was immersed in the wake of a smaller cylinder, representing the trailing-edge region of a stator vane. Time-averaged and time-resolved heat transfer results were obtained over a wide range of Reynolds number at two Mach numbers: one incompressible and one transonic. The tests were conducted at Reynolds numbers, Mach numbers, and gas-to-wall temperature ratios characteristic of turbine engine conditions in an isentropic compression-heated transient wind tunnel (LICH tube). The augmentation of the heat transfer in the stagnation region due to wake unsteadiness was documented by comparison with isolated cylinder tests. It was found that the time-averaged heat transfer rate at the stagnation line, expressed in terms of the Frossling number (Nu/Re), reached a maximum independent of the Reynolds number. The power spectra and cross-correlation of the heat transfer signals in the stagnation region revealed the importance of large vortical structures shed from the upstream wake generator. These structures caused large positive and negative excursions about the mean heat transfer rate in the stagnation region.

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