In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow...In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe(CPAP).It is found that,for flow conditions with low water holdup,there is a large deviation between the model-predicted interface shape and the experimentally measured one.Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall,the models mentioned above are modified by considering dynamic contact angle.The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.展开更多
In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference ...In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference and 26 mm inner diameter are used. When the superficial liquid velocity or the superficial gas velocity is constant,the pressure fluctuations and the probability distribution of the average velocity of slug flow are clear for all of the five experimental conditions. The results of experiment show that the pressure characteristics of slug flow in curved tubes have periodic fluctuations. With the rise of central angle,the period of pressure fluctuation is more obvious. The system pressure of the slug flow increases with the increasing of superficial liquid/gas velocity. Meanwhile,the probability distribution of pressure signal shows regularity,such as unimodal,bimodal or multimodal.展开更多
To investigate the deformation mechanisms of rock under hydrostatic stress, destructive experiments were conducted on sandstone under different levels of hydrostatic stress and stress Lode angles. The results reveal t...To investigate the deformation mechanisms of rock under hydrostatic stress, destructive experiments were conducted on sandstone under different levels of hydrostatic stress and stress Lode angles. The results reveal that the shape of the strength envelope on the π plane gradually changes from the shape of the Lade criterion to the shape of the Drucker-Prage criterion with an increase in hydrostatic stress.Normally, there exists a deviation between the strain and stress paths for porous rocks on the π plane,and the deviation decreases with an increase in stress Lode angle and hydrostatic stress. A rock failure hypothesis based on the rock porous structure was proposed to investigate the reasons for the abovementioned phenomena. It was found that the shear expansion in the minimum principal stress direction is the dominant factor affecting the Lode angle effect(LAE);the magnitude of the hydrostatic stress induces the variation of the porous structure and influences the shear expansion. Therefore, the hydrostatic stress state affects the LAE. The failure hypothesis proposed in this paper can clarify the hydrostatic stress effect, LAE, and the variation of the rock strength envelope shape.展开更多
目的:研究流量-容积(flow-volume,F-V)曲线下降支夹角在慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者临床表型及病情严重度评估中的临床价值。方法:选取2021年12月—2022年12月在南京医科大学第一附属医院进行肺...目的:研究流量-容积(flow-volume,F-V)曲线下降支夹角在慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者临床表型及病情严重度评估中的临床价值。方法:选取2021年12月—2022年12月在南京医科大学第一附属医院进行肺功能检查的患者共101例,其中,存在F-V曲线下降支夹角的稳定期COPD患者(夹角组)33例,与夹角组第1秒用力呼气容积占预计值百分比(forced expiratory volume in the first second as a percentage of predicted value,FEV1%pred)匹配的无下降支夹角的稳定期COPD患者(无夹角组)38例,既往无心肺疾病,且肺功能检测正常的受试者(对照组)30例。收集并比较各组患者基本资料、临床症状评分[COPD自我评估测试(COPD assessment test,CAT)、改良版英国医学研究委员会呼吸困难问卷(modified medical research council dyspnoea scale,mMRC)]、肺功能参数和运动后指脉氧参数。采用多因素Logistic回归分析F-V曲线下降支夹角的相关因素。采用受试者工作特征(receiver operating characteristic,ROC)曲线分析F-V曲线下降支夹角对COPD随访1年内急性加重的预测价值。结果:夹角组肺功能受损程度严重,第1秒用力呼气容积(forced expiratory volume in the first second,FEV1)和用力肺活量(forced vital capacity,FVC)分别为0.91±0.24、2.11±0.63;夹角组CAT评分、mMRC评分、ΔSpO_(2)高于无夹角组及对照组,步行运动后SpO_(2)L低于无夹角组及对照组,差异有统计学意义(P<0.05);夹角组CAT评分≥12分、m MRC评分≥2分、ΔSpO_(2)≥13%是F-V曲线下降支更易出现夹角的主要相关因素;F-V曲线下降支夹角预测重度稳定期COPD急性加重的曲线下面积为0.777,当角度<129.1°时其预测灵敏度、特异度均为最佳,分别为72.73%、67.35%。结论:F-V曲线呈现下降支夹角的COPD患者其肺功能常严重受损,且更易发生活动后低氧血症和急性加重。因此,COPD肺功能报告中应关注F-V曲线下降支是否存在夹角,以便尽早识别COPD高危人群。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41974139,41504104,11572220,51527805)Natural Science Foundation of Tianjin,China(19JCYBJC18400)。
文摘In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe(CPAP).It is found that,for flow conditions with low water holdup,there is a large deviation between the model-predicted interface shape and the experimentally measured one.Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall,the models mentioned above are modified by considering dynamic contact angle.The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.
基金Supported by the National Natural Science Foundation of China(No.5130416)
文摘In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference and 26 mm inner diameter are used. When the superficial liquid velocity or the superficial gas velocity is constant,the pressure fluctuations and the probability distribution of the average velocity of slug flow are clear for all of the five experimental conditions. The results of experiment show that the pressure characteristics of slug flow in curved tubes have periodic fluctuations. With the rise of central angle,the period of pressure fluctuation is more obvious. The system pressure of the slug flow increases with the increasing of superficial liquid/gas velocity. Meanwhile,the probability distribution of pressure signal shows regularity,such as unimodal,bimodal or multimodal.
文摘To investigate the deformation mechanisms of rock under hydrostatic stress, destructive experiments were conducted on sandstone under different levels of hydrostatic stress and stress Lode angles. The results reveal that the shape of the strength envelope on the π plane gradually changes from the shape of the Lade criterion to the shape of the Drucker-Prage criterion with an increase in hydrostatic stress.Normally, there exists a deviation between the strain and stress paths for porous rocks on the π plane,and the deviation decreases with an increase in stress Lode angle and hydrostatic stress. A rock failure hypothesis based on the rock porous structure was proposed to investigate the reasons for the abovementioned phenomena. It was found that the shear expansion in the minimum principal stress direction is the dominant factor affecting the Lode angle effect(LAE);the magnitude of the hydrostatic stress induces the variation of the porous structure and influences the shear expansion. Therefore, the hydrostatic stress state affects the LAE. The failure hypothesis proposed in this paper can clarify the hydrostatic stress effect, LAE, and the variation of the rock strength envelope shape.
文摘目的:研究流量-容积(flow-volume,F-V)曲线下降支夹角在慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者临床表型及病情严重度评估中的临床价值。方法:选取2021年12月—2022年12月在南京医科大学第一附属医院进行肺功能检查的患者共101例,其中,存在F-V曲线下降支夹角的稳定期COPD患者(夹角组)33例,与夹角组第1秒用力呼气容积占预计值百分比(forced expiratory volume in the first second as a percentage of predicted value,FEV1%pred)匹配的无下降支夹角的稳定期COPD患者(无夹角组)38例,既往无心肺疾病,且肺功能检测正常的受试者(对照组)30例。收集并比较各组患者基本资料、临床症状评分[COPD自我评估测试(COPD assessment test,CAT)、改良版英国医学研究委员会呼吸困难问卷(modified medical research council dyspnoea scale,mMRC)]、肺功能参数和运动后指脉氧参数。采用多因素Logistic回归分析F-V曲线下降支夹角的相关因素。采用受试者工作特征(receiver operating characteristic,ROC)曲线分析F-V曲线下降支夹角对COPD随访1年内急性加重的预测价值。结果:夹角组肺功能受损程度严重,第1秒用力呼气容积(forced expiratory volume in the first second,FEV1)和用力肺活量(forced vital capacity,FVC)分别为0.91±0.24、2.11±0.63;夹角组CAT评分、mMRC评分、ΔSpO_(2)高于无夹角组及对照组,步行运动后SpO_(2)L低于无夹角组及对照组,差异有统计学意义(P<0.05);夹角组CAT评分≥12分、m MRC评分≥2分、ΔSpO_(2)≥13%是F-V曲线下降支更易出现夹角的主要相关因素;F-V曲线下降支夹角预测重度稳定期COPD急性加重的曲线下面积为0.777,当角度<129.1°时其预测灵敏度、特异度均为最佳,分别为72.73%、67.35%。结论:F-V曲线呈现下降支夹角的COPD患者其肺功能常严重受损,且更易发生活动后低氧血症和急性加重。因此,COPD肺功能报告中应关注F-V曲线下降支是否存在夹角,以便尽早识别COPD高危人群。
