Wavelet Variable Interval Time Average (WVITA) is introduced as a method incorporating burst event detection in wall turbulence. Wavelet transform is performed to unfold the longitudinal fluctuating velocity time seri...Wavelet Variable Interval Time Average (WVITA) is introduced as a method incorporating burst event detection in wall turbulence. Wavelet transform is performed to unfold the longitudinal fluctuating velocity time series measured in the near wall region of a turbulent boundary layer using hot-film anemometer. This unfolding is both in time and in space simultaneously. The splitted kinetic of the longitudinal fluctuating velocity time series among different scales is obtained by integrating the square of wavelet coefficient modulus over temporal space. The time scale that related to burst events in wall turbulence passing through the fixed probe is ascertained by maximum criterion of the kinetic energy evolution across scales. Wavelet transformed localized variance of the fluctuating velocity time series at the maximum kinetic scale is put forward instead of localized short time average variance in Variable Interval Time Average (VITA) scheme. The burst event detection result shows that WVITA scheme can avoid erroneous judgement and solve the grouping problem more effectively which is caused by VITA scheme itself and can not be avoided by adjusting the threshold level or changing the short time average interval.展开更多
Producing of renewable energy--as well in world as in national context--was necessitated by the synergistic effect of the climate change and the long term, continuous price rise of the fossil energy carriers. Main rea...Producing of renewable energy--as well in world as in national context--was necessitated by the synergistic effect of the climate change and the long term, continuous price rise of the fossil energy carriers. Main reasons for the spread of renewable energy sources are to increase the security of the energy supply or in optimal case, to realize the total energy independence. Furthermore, numerous studies demonstrate that production and also utilization of biofuels--including the organic waste-based fuels--are environmentally sustainable and have positive impact for the security of energy supply. This paper deals with production of biogas （from agricultural organic wastes） for energy. The production of biogas and the other biofuels will help you find the balance in agriculture because they can be generated from biomass, agricultural wastes and non-food plant material. In addition to the objective of saving emissions, EU biofuels policy aims to ensure the necessary energy and to decrease unemployment. So this paper would like to contribute to the EU requirements through the research. The producing system can be expansible by utilization of other organic material, so it is supported the efficient operation.展开更多
基金The project supported by the National Natural Science Foundation of China(19732005)the National Climbing Project of China
文摘Wavelet Variable Interval Time Average (WVITA) is introduced as a method incorporating burst event detection in wall turbulence. Wavelet transform is performed to unfold the longitudinal fluctuating velocity time series measured in the near wall region of a turbulent boundary layer using hot-film anemometer. This unfolding is both in time and in space simultaneously. The splitted kinetic of the longitudinal fluctuating velocity time series among different scales is obtained by integrating the square of wavelet coefficient modulus over temporal space. The time scale that related to burst events in wall turbulence passing through the fixed probe is ascertained by maximum criterion of the kinetic energy evolution across scales. Wavelet transformed localized variance of the fluctuating velocity time series at the maximum kinetic scale is put forward instead of localized short time average variance in Variable Interval Time Average (VITA) scheme. The burst event detection result shows that WVITA scheme can avoid erroneous judgement and solve the grouping problem more effectively which is caused by VITA scheme itself and can not be avoided by adjusting the threshold level or changing the short time average interval.
文摘Producing of renewable energy--as well in world as in national context--was necessitated by the synergistic effect of the climate change and the long term, continuous price rise of the fossil energy carriers. Main reasons for the spread of renewable energy sources are to increase the security of the energy supply or in optimal case, to realize the total energy independence. Furthermore, numerous studies demonstrate that production and also utilization of biofuels--including the organic waste-based fuels--are environmentally sustainable and have positive impact for the security of energy supply. This paper deals with production of biogas （from agricultural organic wastes） for energy. The production of biogas and the other biofuels will help you find the balance in agriculture because they can be generated from biomass, agricultural wastes and non-food plant material. In addition to the objective of saving emissions, EU biofuels policy aims to ensure the necessary energy and to decrease unemployment. So this paper would like to contribute to the EU requirements through the research. The producing system can be expansible by utilization of other organic material, so it is supported the efficient operation.
