Investigation of Chemical Non-equilibrium Hypersonic Flows in Carbon Dioxide–Nitrogen Atmospheres Using a Coupled Euler–Boundary-Layer Method

2017 ◽  
pp. 133-137
Author(s):  
M. Starkloff ◽  
Ch. Mundt
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Hypersonic Flows ◽  
Layer Method ◽  
Boundary Layer Method ◽  
Non Equilibrium

scholarly journals Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method

2018 ◽  
Vol 15 (2) ◽  
pp. 429-445 ◽  
Author(s):  
Kukka-Maaria Erkkilä ◽  
Anne Ojala ◽  
David Bastviken ◽  
Tobias Biermann ◽  
Jouni J. Heiskanen ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Spatial Variation ◽  
Co2 Flux ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Night Time ◽  
Layer Method ◽  
Boundary Layer Method ◽  
Flux Measurements

Abstract. Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, kCC (introduced by Cole and Caraco, 1998), for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer velocities (kTE and kHE), which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model kTE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference between CO2 fluxes from shallower and deeper areas. We highlight that while all flux measurement methods have their pros and cons, it is important to carefully think about the chosen method and measurement interval, as well as their effects on the resulting flux.

scholarly journals Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method

2017 ◽  
Author(s):  
Kukka-Maaria Erkkilä ◽  
Ivan Mammarella ◽  
David Bastviken ◽  
Tobias Biermann ◽  
Jouni J. Heiskanen ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Diurnal Variation ◽  
Spatial Variation ◽  
Eddy Covariance ◽  
Co2 Flux ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Layer Method ◽  
Boundary Layer Method

Abstract. Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind speed based gas transfer coefficient, kCC, for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer coefficients (kTE and kHE), that include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. A clear increase in both CH4 and CO2 fluxes was detected right after turnover started. Results show that kCC model underestimates both CH4 and CO2 fluxes compared to EC measurements and the more recent model kTE gives the best fit with EC fluxes. In the stratified period, kHE and kCC used in BLM calculation have similar diurnal variation for CO2 flux, while kTE gives an opposite diurnal cycle. This is probably due to water friction velocity derived from EC measurements in kTE model instead of direct waterside turbulence measurements in this study. In the mixing period all models agree well with each other on diurnal variation for both CH4 and CO2. We highly recommend using up to date gas transfer models, instead of kCC, for better flux estimates. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes, but a clear difference between CO2 fluxes from shallower and deeper areas. Fluxes measured with FC were systematically higher than EC fluxes, partly due to deficiencies in the EC method.

Boundary layer method in the problem of far propagation of surface SV-waves

2011 ◽  
Vol 175 (6) ◽  
pp. 651-671
Author(s):  
N. Ya. Kirpichnikova ◽  
A. S. Kirpichnikova
Keyword(s):  
Boundary Layer ◽  
Layer Method ◽  
Boundary Layer Method

A Simple and Robust Subsonic Boundary Layer Method to Be Used with the Panel Method for Wing Calculations Using a Wing Strip Approach

2015 ◽  
Vol 798 ◽  
pp. 596-601
Author(s):  
R.F. Francisco Reis ◽  
Guilherme A. Santana ◽  
Paulo Iscold ◽  
Carlos A. Cimini
Keyword(s):  
Boundary Layer ◽  
Lift Coefficient ◽  
Aircraft Design ◽  
Aerodynamic Characteristics ◽  
Viscous Drag ◽  
Layer Method ◽  
Boundary Layer Method ◽  
Dimensional Boundary ◽  
Classical Integral ◽  
Empirical Corrections

This paper will present the development of a simple subsonic boundary layer method suitable to be used coupled with panel methods in order to estimate the aerodynamic characteristics, including viscous drag and maximum lift coefficient, of 3D wings. The proposed method does not require viscous-inviscid iterations and is based on classical integral bi-dimensional boundary layer theory using Thwaites and Head ́s models with bi-dimensional empirical corrections applied to each wing strip being therefor robust and efficient to be used in the early conceptual stage of aircraft design. Presented results are compared to the Modified CS Method in an IBL scheme and experimental data and are shown to provide good results.

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