Cold flowfleld of pitot SFRJ with three different nozzle throat diameters were simulated at M4.03 and M3.0 by FLUENT software. The flowfield characteristics and engine performances were obtained and analyzed. The results indicate that pressure data obtained by simulation have an overall agreement with those got by experiment. Pitot inlet at design or ideal mode operates with a tiny subcritical position, instead of critical or supercritical position. With the increase of nozzle diameter, nozzle exit total pressure recovery increases and drag coefficient decreases. Compared with the operation at M4.03, SFRJs at M3.0 have lower mass capture ratio, higher nozzle exit total pressure recovery and higher drag coefficient.
Although vertical circulation well (VCW) has been widely applied for aquifer remediation and hydrogeological parameter estimation for three decades, few studies have focused on the hydraulic zone visualization, and the spatial scale of hydraulic zones as functions of VCW parameters.This study provided a numerical method to visualize 3D steady-state flow field induced by VCW in a confined aquifer in presence of an ambient flow.Mathematical model for velocity field is established based on the superposition principle, and the fourth-order Runge-Kutta method is adopted to perform particle tracking.Visualization results illustrate that 3D flow regime can be divided into Recirculation, Capture, and Discharge zones.An integrated dimensionless parameter Q D is introduced to account for the relative strength of VCW flow against ambient flow.Comparison is performed through simulations by different Q D -d D combinations, where d D is the dimensionless distance between injection and extraction screens.Results demonstrate that: (1) a Q D -d D breakthrough line can be established to mark the occurrence of circulatory flow; (2) the effect of Q D on the size of recirculation zone is significant when Q D is smaller than 3.5, while d D becomes more influential if Q D is larger; (3) the extent of capture and discharge zone enlarges as Q D and/or d D increases.
Abstract. We carried out 19 city-circle-around car multi-axis differential optical absorption spectroscopy (MAX-DOAS) experiments on the 6th Ring Road of Beijing in January, September, and October 2014. The tropospheric vertical column densities (VCDs) of NO2 were retrieved from measured spectra by the MAX-DOAS technique and used to estimate the emissions of NOx (≡NO+NO2) from urban Beijing during the experimental periods. The offline LAPS-WRF-CMAQ model system was used to simulate the wind fields by assimilation of observational data and calculate the NO2-to-NOx concentration ratios, both of which are also needed for the estimation of NOx emissions. The NOx emissions in urban Beijing for the different months derived from the car MAX-DOAS measurements in this study were compared to the multi-resolution emission inventory in China for 2012 (MEIC 2012). Our car MAX-DOAS measurements showed higher NO2 VCD in January than in the other two months. The wind field had obvious impacts on the spatial distribution of NO2 VCD, with the mean NO2 VCD along the 6th Ring Road typically being higher under the southerly wind than under the northerly wind. In addition to the seasonal difference, the journey-to-journey variations of estimated NOx emission rates (ENOx) were large even within the same month, mainly due to uncertainties in the calculations of wind speed, the ratio of NO2 and NOx concentration, and the decay rate of NOx from the emission sources to the measured positions under different meteorological conditions. The ranges of ENOx during the heating and non-heating periods were 22.6×1025 to 31.3×1025 and 9.6×1025 to 12.0×1025 molec. s−1, respectively. The average ENOx values in the heating and non-heating periods were 26.9±6.1×1025 molec. s−1 and 11.0±1.2×1025 molec. s−1, respectively. The uncertainty range of ENOx was 20 %–52 %. The monthly emission rates from MEIC 2012 are found to be lower than the estimated ENOx, particularly in January. Our results provide important information and datasets for the validation of satellite products and also show how car MAX-DOAS measurements can be used effectively for dynamic monitoring and updating of the NOx emissions from megacities such as Beijing.
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