The Experts below are selected from a list of 62946 Experts worldwide ranked by ideXlab platform
G H Su - One of the best experts on this subject based on the ideXlab platform.
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model application research for liquid Entrainment through ads 4 pipe in ap1000
Annals of Nuclear Energy, 2017Co-Authors: Zhaoming Meng, Lei Ding, G H Su, Wenxi TianAbstract:Abstract Application research of two new liquid Entrainment models for separately predicting the beginning of Entrainment and branch Entrainment quality is performed which is a continuation of previous experimental and theoretical studies on the Entrainment at T-junction. The new onset Entrainment model and branch quality model are developed on the basis of the scaling experiment for studying ADS-4 Entrainment phenomenon in AP1000 plant, and the two new models along with previously published Entrainment models are compared. The results show that previous models in the background of Entrainment through a small break of primary pipe are not suitable for predicting the Entrainment through a large size branch (e.g. ADS-4 pipe), while the two new models have a larger applicability. Also, the new Entrainment models are written into the RELAP5 code, and then a typical 2-in SBLOCA transient in AP1000 is simulated separately by the modified RELAP5 and the original RELAP5 to further discuss the applicability of new models for the simulation of Entrainment through ADS-4. The results show that the modified RELAP5 can get more reasonable simulation results. In view of original RELAP5 overestimated core coolant inventory, the modified RELAP5 can get a conservative core coolant inventory. Hence we can conclude that the new Entrainment models are more suitable for the simulation of Entrainment through ADS-4.
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models development of liquid drops Entrainment at a t junction with a large vertical up branch
International Journal of Heat and Mass Transfer, 2017Co-Authors: Yong Zhang, G H SuAbstract:Abstract The liquid Entrainment process at the vertical up tee branch is widespread in mass and heat transfer applications. Existing liquid Entrainment models mainly apply to T-junctions with small diameter ratios of branch to main line (d/D), which are unable to predict the liquid Entrainment under large d/D conditions. The models of liquid Entrainment onset and Entrainment rate are developed under reasonable assumptions. The Entrainment onset model was developed based on the wave theory, force analysis and potential flow theory. The Bond number is innovatively introduced into the model to represent the effect of surface tension acting on the Entrainment onset. The model is compared against the relevant experimental data which shows good agreement. In the modeling of the Entrainment rate, the key parameters are obtained by nondimensionalizing the conservation equations governing the liquid Entrainment process, and the constants in the model are determined by genetic algorithm. The model agrees well with existing experimental data.
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experimental simulation of liquid Entrainment in ads 4 depressurization line in ap1000
Progress in Nuclear Energy, 2016Co-Authors: Yan Xiang, P Zhang, Yingwei Wu, W X Tian, G H SuAbstract:Abstract The fourth stage Automatic Depressurization System is an important passive safety feature in Westinghouse AP1000 which enables controlled depressurization of reactor coolant system in small break LOCA. However, large amount of coolant can be carried to the containment via the ADS-4 branch Entrainment and the upper plenum Entrainment during the depressurization process, which poses great threats to core uncovering and melting. The automatic Depressurization and Entrainment TEst Loop (ADETEL) modeled after AP1000 with a scaling ratio of 1:5.6 was constructed to investigate the Entrainment and depressurization behavior after the actuation of ADS-4 valves. The Entrainment and depressurization features were investigated under different initial pressure, mixture liquid level in the pressure vessel and heating power. The Entrainment deposition effect of the reactor internals was also investigated. The test data reveals that large amount of water are entrained through the ADS-4 branch line within a short period of time. The liquid Entrainment rate and the reduced rate of the mixture liquid level in the pressure vessel increase with the initial system pressure. It is notable that the core uncovery was experienced when the initial pressure was set to 0.5 MPa in current experimental conditions. The reactor internals have little effect on the entrained mass and the mixture liquid levels in the pressure vessel.
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comparative study on effect of air water and steam water mediums on liquid Entrainment through ads 4 in ap1000
Experimental Thermal and Fluid Science, 2015Co-Authors: Zhaoming Meng, Lei Ding, Xiaoliang Fu, Wenxi Tian, Yanhua Yang, G H SuAbstract:Abstract For the previous experiments of Entrainment at T-junction, the air–cold water two-phase flow is always selected as working medium, and the theoretical models of liquid Entrainment are established mainly based on the experimental data of air–water Entrainment through a small break. The saturated steam–water Entrainment experiments are gravely insufficient, especially the steam–water experiments of Entrainment through a large size branch are even fewer. Hence, a scale-down experiment of steam–water Entrainment at T-junction has been conducted referring to liquid Entrainment through ADS-4 (Fourth Stage Automatic Depressurization System) in AP1000 nuclear plant. The steam–water experimental results are comprehensively compared with the results of the previous similar air–water experiment: The visualization research shows that the same Entrainment phenomena can be observed including intermittent flow Entrainment, stratified flow Entrainment and annular flow Entrainment; The transition conditions between the two Entrainment phenomena have a little difference but can be negligible; The comparison of experimental data of Entrainment onset and stable Entrainment indicates that the experimental data of steam–water and air–water have the same change tendency, and the air–water correlation can agree well with the steam–water data. Hence, we can make a conclusion that effect of different working mediums on liquid Entrainment is negligible. In addition, based on the analysis of model formation, we suppose that effect of the system pressure on Entrainment can be neglected under 0.22 MPa.
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experimental investigation of liquid Entrainment in ads 4 depressurization line with steam water
Experimental Thermal and Fluid Science, 2015Co-Authors: Yan Xiang, P Zhang, W X Tian, J Zhang, G H SuAbstract:Abstract The fourth stage Automatic Depressurization System (ADS-4) is an important part in Westinghouse AP600/AP100 which enables controlled depressurization of reactor coolant system during small break LOCA. However, the coolant may be entrained into the containment through the ADS-4 branch line simultaneously, which poses great threats to reactor core uncovering and melting. To investigate the Entrainment phenomenon of ADS-4 in AP1000, ADS-4 Depressurization and Entrainment TEst Loop (ADETEL) with a scaling ratio of 1:5.6 was constructed and visualization experiments were conducted with steam–water. The experiment were conducted at atmospheric pressure with the maximum steam flow rate of 700 kg/h. The Entrainment processes were recorded by a high speed camera and analyzed in detail. Onset of Entrainment and Entrainment rate data were obtained and compared with existing test data and correlations. Empirical correlation of ADS-4 branch Entrainment onset has been developed. A clear difference exists between ADETEL Entrainment onset data and available correlations, which may caused by the differences in fluids physical properties, horizontal pipe flow conditions, determination of Entrainment onset and d / D ratios. The Entrainment onset is more likely to be reached in small d / D ratios conditions due to the stronger Bernoulli effect. Besides, AP1000 has a higher branch quality than AP600 at the same liquid level in the hot leg.
Zhaoming Meng - One of the best experts on this subject based on the ideXlab platform.
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development of correlations for liquid Entrainment through a large scale inclined branch pipe connected to the main horizontal pipe
Experimental Thermal and Fluid Science, 2018Co-Authors: Zhaoming Meng, Jinpu Wang, Feifei Nian, Jun Wang, Ming DingAbstract:Abstract Many theoretical and experimental studies have been conducted over the years on liquid Entrainment through a branch pipe connected to the main horizontal pipe (i.e., Entrainment at the T-junction). Several mathematical models have been developed to predict the onset of liquid Entrainment and branch quality during the liquid Entrainment process with reasonable accuracy. Most of these models are developed based on small-scale branch, where the ratio of the branch diameter to the horizontal pipe diameter is less than or equal to 0.2 (d/D ≤ 0.2). Therefore, these models are not suitable to predict the onset of liquid Entrainment through a large-scale branch. In addition, these models are developed for a specific branch angle (typically 0 or 90°) and therefore, are incapable of making good predictions of the onset of liquid Entrainment through a large-scale branch inclined at other angles. In order to address these issues, we conducted experiments to investigate the onset of liquid Entrainment through a large-scale branch pipe (d/D > 0.6) inclined at three angles (32.2, 47.9, and 62.3°) and we assessed the mass flow quality of the branch. By analyzing the mathematical models for liquid Entrainment currently available and by theoretical deduction, we developed new correlations to predict the onset of liquid Entrainment and mass flow quality. We found that the values predicted by these correlations fit well with the experimental data with a maximum error of ±35%. Both of these liquid Entrainment correlations provide good predictions of liquid Entrainment through a large-scale branch inclined at an angle of 32.2, 47.9, and 62.3°. We also obtained some meaningful conclusions based on the experimental data. We found that at the onset of liquid Entrainment, under similar experimental conditions, the critical Froude number Frg decreases with an increase in the branch angle. In addition, the larger the branch angle, the lower the effect of the branch scale on the onset of liquid Entrainment. There are two primary factors that influence the liquid Entrainment process: (1) gas chamber height—the liquid Entrainment process is promoted as the gas chamber height decreases, and (2) vertical component of the inertial force—the liquid Entrainment process is weakened with a decrease in the vertical component of the inertial force. This indicates that the gas chamber height dominates the liquid Entrainment process at relatively large branch angles whereas the vertical component of the inertial force dominates the liquid Entrainment process at small branch angles.
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model application research for liquid Entrainment through ads 4 pipe in ap1000
Annals of Nuclear Energy, 2017Co-Authors: Zhaoming Meng, Lei Ding, G H Su, Wenxi TianAbstract:Abstract Application research of two new liquid Entrainment models for separately predicting the beginning of Entrainment and branch Entrainment quality is performed which is a continuation of previous experimental and theoretical studies on the Entrainment at T-junction. The new onset Entrainment model and branch quality model are developed on the basis of the scaling experiment for studying ADS-4 Entrainment phenomenon in AP1000 plant, and the two new models along with previously published Entrainment models are compared. The results show that previous models in the background of Entrainment through a small break of primary pipe are not suitable for predicting the Entrainment through a large size branch (e.g. ADS-4 pipe), while the two new models have a larger applicability. Also, the new Entrainment models are written into the RELAP5 code, and then a typical 2-in SBLOCA transient in AP1000 is simulated separately by the modified RELAP5 and the original RELAP5 to further discuss the applicability of new models for the simulation of Entrainment through ADS-4. The results show that the modified RELAP5 can get more reasonable simulation results. In view of original RELAP5 overestimated core coolant inventory, the modified RELAP5 can get a conservative core coolant inventory. Hence we can conclude that the new Entrainment models are more suitable for the simulation of Entrainment through ADS-4.
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comparative study on effect of air water and steam water mediums on liquid Entrainment through ads 4 in ap1000
Experimental Thermal and Fluid Science, 2015Co-Authors: Zhaoming Meng, Lei Ding, Xiaoliang Fu, Wenxi Tian, Yanhua Yang, G H SuAbstract:Abstract For the previous experiments of Entrainment at T-junction, the air–cold water two-phase flow is always selected as working medium, and the theoretical models of liquid Entrainment are established mainly based on the experimental data of air–water Entrainment through a small break. The saturated steam–water Entrainment experiments are gravely insufficient, especially the steam–water experiments of Entrainment through a large size branch are even fewer. Hence, a scale-down experiment of steam–water Entrainment at T-junction has been conducted referring to liquid Entrainment through ADS-4 (Fourth Stage Automatic Depressurization System) in AP1000 nuclear plant. The steam–water experimental results are comprehensively compared with the results of the previous similar air–water experiment: The visualization research shows that the same Entrainment phenomena can be observed including intermittent flow Entrainment, stratified flow Entrainment and annular flow Entrainment; The transition conditions between the two Entrainment phenomena have a little difference but can be negligible; The comparison of experimental data of Entrainment onset and stable Entrainment indicates that the experimental data of steam–water and air–water have the same change tendency, and the air–water correlation can agree well with the steam–water data. Hence, we can make a conclusion that effect of different working mediums on liquid Entrainment is negligible. In addition, based on the analysis of model formation, we suppose that effect of the system pressure on Entrainment can be neglected under 0.22 MPa.
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experimental research of liquid Entrainment through ads 4 in ap1000
Annals of Nuclear Energy, 2014Co-Authors: Zhaoming Meng, Laishun Wang, Xiaoliang Fu, Wenxi Tian, Yanhua Yang, Bo Dong, G H SuAbstract:Abstract In this study, based on a T-junction that consists of Automatic Depressurization System Stage Four (ADS-4) and hot leg in an AP1000 plant, a small-scale experimental research on Entrainment at a T-junction was performed. This study mainly focused on the effect of various factors on Entrainment, such as the effect of branch size, branch shape and liquid crossflow. The flow pattern map was plotted from the experimental data, and the visualization research indicated that the Entrainment phenomena through a large size branch were apparently different from that through a small branch. Three Entrainment phenomena were observed in the studies, two Entrainment mechanisms could be found in the stratified flow regime Entrainment area, the existence of branch contributed to generating intermittent flow in the horizontal main pipe, and the backflow region was observable in the vicinity of a large size branch inlet. Also, experimental research showed that downstream of the branch of T-junction had an important effect on the onset Entrainment, and liquid crossflow did not seem to affect the onset Entrainment.
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experimental and theoretical investigation of liquid Entrainment through small scaled ads 4 in ap1000
Experimental Thermal and Fluid Science, 2014Co-Authors: Zhaoming Meng, Lei Ding, Xiaoliang Fu, Wenxi Tian, Yanhua Yang, Bo Dong, G H SuAbstract:Abstract An experimental and theoretical research has been performed for liquid Entrainment at T-junction consisting of hot leg and ADS-4 pipe in view of the insufficiency of existing studies. Based on visualization research, three kinds of Entrainment phenomena including intermittent Entrainment, stratified Entrainment and annular Entrainment are clearly observed, and the feature of each flow regime is summarized and recorded by high-speed camera. Also, the flow pattern map is plotted from the experimental data to indicate the transition conditions of different flow regimes. For the purpose of modeling and expanding previous research, the influence of entrance length on Entrainment is discussed on the basis of two different test sections. The effect of liquid flow on onset Entrainment and stable Entrainment is analyzed, and experiment results show that the effect of liquid flow on Entrainment through ADS-4 pipe can be neglected. Also, onset Entrainment model and branch quality model are established and accord with experimental data well.
J Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of liquid Entrainment in ads 4 depressurization line with steam water
Experimental Thermal and Fluid Science, 2015Co-Authors: Yan Xiang, P Zhang, W X Tian, J Zhang, G H SuAbstract:Abstract The fourth stage Automatic Depressurization System (ADS-4) is an important part in Westinghouse AP600/AP100 which enables controlled depressurization of reactor coolant system during small break LOCA. However, the coolant may be entrained into the containment through the ADS-4 branch line simultaneously, which poses great threats to reactor core uncovering and melting. To investigate the Entrainment phenomenon of ADS-4 in AP1000, ADS-4 Depressurization and Entrainment TEst Loop (ADETEL) with a scaling ratio of 1:5.6 was constructed and visualization experiments were conducted with steam–water. The experiment were conducted at atmospheric pressure with the maximum steam flow rate of 700 kg/h. The Entrainment processes were recorded by a high speed camera and analyzed in detail. Onset of Entrainment and Entrainment rate data were obtained and compared with existing test data and correlations. Empirical correlation of ADS-4 branch Entrainment onset has been developed. A clear difference exists between ADETEL Entrainment onset data and available correlations, which may caused by the differences in fluids physical properties, horizontal pipe flow conditions, determination of Entrainment onset and d / D ratios. The Entrainment onset is more likely to be reached in small d / D ratios conditions due to the stronger Bernoulli effect. Besides, AP1000 has a higher branch quality than AP600 at the same liquid level in the hot leg.
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experimental investigation of liquid Entrainment in vertical up tee branch with double end gas inlets
Annals of Nuclear Energy, 2015Co-Authors: J Zhang, W X Tian, Yan Xiang, P ZhangAbstract:Abstract Tee branches are widely used in nuclear power plants for varying purposes. The tee branch is adopted by the fourth stage Automatic Depressurization System (ADS-4) in Westinghouse AP600/AP1000 to depressurize the primary loop during the small break loss of coolant accident (SBLOCA). However, large amount of coolant will be entrained simultaneously through the ADS-4 branch which poses the threat of core uncovering and melting. Visualization experiments with double-end gas inlets were conducted to investigate the ADS-4 tee branch Entrainment phenomena in AP1000. Entrainment process were recorded by high speed camera and analyzed in detail. The onset of liquid Entrainment and Entrainment rate data were obtained and compared with existing data and correlations, and discrepancies were found in the comparison due to the difference of test section geometric configuration. The gas flow rate has little effect on the branch quality at the same dimensionless gas chamber height in Entrainment rate tests. The Entrainment frequency was also studied. The test data reveal that the Entrainment period decreases rapidly with the increase of Entrainment rate in low range of the Entrainment rate, and gradually stabilizes in high range of the Entrainment rate.
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experimental investigation of liquid Entrainment in ap1000 ads 4 branch line with air water
Experimental Thermal and Fluid Science, 2014Co-Authors: J ZhangAbstract:Abstract ADS-4 branch line provides a controlled depressurization of the Westinghouse AP600/AP1000 primary loop during a small break LOCA. However, the coolant will be entrained to the containment simultaneously which leads to the loss of liquid inventory. ADS-4 Depressurization and Entrainment TEst Loop (ADETEL) scaled after AP1000 was constructed and visualization experiments were conducted to investigate the Entrainment phenomenon at the ADS-4 tee branch line. Entrainment phenomena were recorded by high speed camera and analyzed in detail. The Entrainment onset and stabilized Entrainment rate data were collected and compared with available data. Discrepancies were found between ADETEL experimental data and available data due to the difference of experimental conditions and test section geometric configuration. The test data reveals that the tee branch liquid Entrainment model used in RELAP5 cannot estimate the ADS-4 Entrainment for AP1000 accurately and therefore more practicable model should be developed. The ADETEL data also manifest that AP1000 has a higher degree of safety performance during ADS-4 branch depressurization process than AP600 design.
Yan Xiang - One of the best experts on this subject based on the ideXlab platform.
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experimental simulation of liquid Entrainment in ads 4 depressurization line in ap1000
Progress in Nuclear Energy, 2016Co-Authors: Yan Xiang, P Zhang, Yingwei Wu, W X Tian, G H SuAbstract:Abstract The fourth stage Automatic Depressurization System is an important passive safety feature in Westinghouse AP1000 which enables controlled depressurization of reactor coolant system in small break LOCA. However, large amount of coolant can be carried to the containment via the ADS-4 branch Entrainment and the upper plenum Entrainment during the depressurization process, which poses great threats to core uncovering and melting. The automatic Depressurization and Entrainment TEst Loop (ADETEL) modeled after AP1000 with a scaling ratio of 1:5.6 was constructed to investigate the Entrainment and depressurization behavior after the actuation of ADS-4 valves. The Entrainment and depressurization features were investigated under different initial pressure, mixture liquid level in the pressure vessel and heating power. The Entrainment deposition effect of the reactor internals was also investigated. The test data reveals that large amount of water are entrained through the ADS-4 branch line within a short period of time. The liquid Entrainment rate and the reduced rate of the mixture liquid level in the pressure vessel increase with the initial system pressure. It is notable that the core uncovery was experienced when the initial pressure was set to 0.5 MPa in current experimental conditions. The reactor internals have little effect on the entrained mass and the mixture liquid levels in the pressure vessel.
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experimental investigation of liquid Entrainment in vertical up tee branch with double end gas inlets
Annals of Nuclear Energy, 2015Co-Authors: J Zhang, W X Tian, Yan Xiang, P ZhangAbstract:Abstract Tee branches are widely used in nuclear power plants for varying purposes. The tee branch is adopted by the fourth stage Automatic Depressurization System (ADS-4) in Westinghouse AP600/AP1000 to depressurize the primary loop during the small break loss of coolant accident (SBLOCA). However, large amount of coolant will be entrained simultaneously through the ADS-4 branch which poses the threat of core uncovering and melting. Visualization experiments with double-end gas inlets were conducted to investigate the ADS-4 tee branch Entrainment phenomena in AP1000. Entrainment process were recorded by high speed camera and analyzed in detail. The onset of liquid Entrainment and Entrainment rate data were obtained and compared with existing data and correlations, and discrepancies were found in the comparison due to the difference of test section geometric configuration. The gas flow rate has little effect on the branch quality at the same dimensionless gas chamber height in Entrainment rate tests. The Entrainment frequency was also studied. The test data reveal that the Entrainment period decreases rapidly with the increase of Entrainment rate in low range of the Entrainment rate, and gradually stabilizes in high range of the Entrainment rate.
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experimental investigation of liquid Entrainment in ads 4 depressurization line with steam water
Experimental Thermal and Fluid Science, 2015Co-Authors: Yan Xiang, P Zhang, W X Tian, J Zhang, G H SuAbstract:Abstract The fourth stage Automatic Depressurization System (ADS-4) is an important part in Westinghouse AP600/AP100 which enables controlled depressurization of reactor coolant system during small break LOCA. However, the coolant may be entrained into the containment through the ADS-4 branch line simultaneously, which poses great threats to reactor core uncovering and melting. To investigate the Entrainment phenomenon of ADS-4 in AP1000, ADS-4 Depressurization and Entrainment TEst Loop (ADETEL) with a scaling ratio of 1:5.6 was constructed and visualization experiments were conducted with steam–water. The experiment were conducted at atmospheric pressure with the maximum steam flow rate of 700 kg/h. The Entrainment processes were recorded by a high speed camera and analyzed in detail. Onset of Entrainment and Entrainment rate data were obtained and compared with existing test data and correlations. Empirical correlation of ADS-4 branch Entrainment onset has been developed. A clear difference exists between ADETEL Entrainment onset data and available correlations, which may caused by the differences in fluids physical properties, horizontal pipe flow conditions, determination of Entrainment onset and d / D ratios. The Entrainment onset is more likely to be reached in small d / D ratios conditions due to the stronger Bernoulli effect. Besides, AP1000 has a higher branch quality than AP600 at the same liquid level in the hot leg.
Junya Uchida - One of the best experts on this subject based on the ideXlab platform.
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cloud droplet sedimentation Entrainment efficiency and subtropical stratocumulus albedo
Geophysical Research Letters, 2007Co-Authors: Christopher S Bretherton, Peter N Blossey, Junya UchidaAbstract:[1] The effect of cloud droplet sedimentation on the Entrainment rate and liquid water path of a nocturnal nondrizzling stratocumulus layer is examined using large-eddy simulations (LES) with bulk microphysics. In agreement with a prior study by Ackerman et al. (2004), sedimentation is found to decrease Entrainment rate and thereby increase liquid water path. They suggested this is due to reduction of boundary-layer turbulence. Our simulations suggest otherwise. Instead, sedimentation reduces Entrainment by removing liquid water from the Entrainment zone. This inhibits two mechanisms that promote the sinking of entrained air into the cloud layer–Entrainment-induced evaporative cooling and longwave radiative cooling. A sensitivity study shows that the radiative effect is less important than the reduced evaporation. A possible parameterization of the effect of sedimentation on Entrainment rate in a mixed layer model is proposed and tested. Since the droplet sedimentation rate is inversely related to cloud droplet (and presumably aerosol) concentration and nearly nondrizzling marine stratocumulus are widespread, sedimentation impacts on stratocumulus Entrainment efficiency should be considered in climate model simulations of the aerosol indirect effect.
