The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determine...The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation （LES）. Following this, a hybrid method of combining LES and Lighthill＇s acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction （FSI） code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.展开更多
Objective To evaluate the immediate and follow-up results of percutaneous transluminal septal myocardial ablation (PTSMA) in patients with hypertrophic obstructive cardiomyopathy (HOCM). Methods Fifteen symptomatic...Objective To evaluate the immediate and follow-up results of percutaneous transluminal septal myocardial ablation (PTSMA) in patients with hypertrophic obstructive cardiomyopathy (HOCM). Methods Fifteen symptomatic, drug-refractory patients with HOCM underwent PTSMA procedures with application of a myocardial contrast echocardiography (MCE) intra-procedure. Before and after the procedure, clinical evaluations were obtained in all patients, who were followed up for a mean period of 8.6±3.8 (6-20) months.Results Immediate left ventricular outflow tract gradient (LVOTG) reduction was achieved (77.93±22?mm?Hg vs 14.8±15?mm?Hg, P【0.0001) after the procedure with a mean decrease of 5.75±2.87?mm?Hg of left ventricular end diastolic pressure (P【0.001). Follow up results revealed that ventricular remodelling occurred mainly 1-3 months after the procedure, but without evidence of ventricular dilation and contract dysfunction. Heart function (NYHA) was greatly improved (3.4±0.5 vs 1.1±0.4, P【0.001) and exercise endurance increased. A renewed increase of LVOTG was found in 2 patients during follow-up. Conclusions LVOTG was greatly decreased in HOCM patients undergoing a PTSMA procedure, and their symptoms were greatly improved without cardiac complications during follow-up. Sub-selection and re-opening of target vessels were the causes of renewed increase of LVOTG, and this can be avoided with the accumulation of experience. This is a promising method for the treatment of symptomatic patients with HOCM.展开更多
Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited exp...Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited experimental work which is confined to one aspect- The present work aims to depict theconvective heat transfer inside a tweended inclined tube with East-West symmetric heat input us-ing numerical methods. Based on reasonable assumptions, governing equations of the inside fluid areestabllshed. The corresponding discretizated equations are solved by employing numerical methods.The calculated results are displayed for velocity and temperature profiles on different cross-sectionalplanes, which present the flow pattern characterized by upflow and dowallow along the axial direc-tion and adherent flow along the peripheral direction, and the heat transfer process from the wall tothe center. Furthermore, the transient Nusselt number and average temperature level are shown anddiscussed. Finally, the parametric effects of the tube radius and the heat input on the flow and heattransfer are also given.展开更多
Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of...Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of coolants into account, which are more generalized than those which neglect the conduction. For the same reason, they are suitable particularly for gases-cooled microchannels.With only numerical solution to the equations till today, an approximate analytic solution is derived here. From this solution, a rather simple formula can be introduced bober, by which the differences between considering the conduction and neglecting it are easily found. In addition, the rcasonableness of the classical fin method is also discussed. An experimental example of air-cooled microchannels is illustrated.展开更多
基金Supported by the Independent Innovation Foundation for National Defense of Huazhong University of Science and Technology(No.01-18-140019)
文摘The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation （LES）. Following this, a hybrid method of combining LES and Lighthill＇s acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction （FSI） code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.
文摘Objective To evaluate the immediate and follow-up results of percutaneous transluminal septal myocardial ablation (PTSMA) in patients with hypertrophic obstructive cardiomyopathy (HOCM). Methods Fifteen symptomatic, drug-refractory patients with HOCM underwent PTSMA procedures with application of a myocardial contrast echocardiography (MCE) intra-procedure. Before and after the procedure, clinical evaluations were obtained in all patients, who were followed up for a mean period of 8.6±3.8 (6-20) months.Results Immediate left ventricular outflow tract gradient (LVOTG) reduction was achieved (77.93±22?mm?Hg vs 14.8±15?mm?Hg, P【0.0001) after the procedure with a mean decrease of 5.75±2.87?mm?Hg of left ventricular end diastolic pressure (P【0.001). Follow up results revealed that ventricular remodelling occurred mainly 1-3 months after the procedure, but without evidence of ventricular dilation and contract dysfunction. Heart function (NYHA) was greatly improved (3.4±0.5 vs 1.1±0.4, P【0.001) and exercise endurance increased. A renewed increase of LVOTG was found in 2 patients during follow-up. Conclusions LVOTG was greatly decreased in HOCM patients undergoing a PTSMA procedure, and their symptoms were greatly improved without cardiac complications during follow-up. Sub-selection and re-opening of target vessels were the causes of renewed increase of LVOTG, and this can be avoided with the accumulation of experience. This is a promising method for the treatment of symptomatic patients with HOCM.
文摘Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection prob-lem driven by buoyancy. Because of its complexity, no effective theoretical model is available despiteof limited experimental work which is confined to one aspect- The present work aims to depict theconvective heat transfer inside a tweended inclined tube with East-West symmetric heat input us-ing numerical methods. Based on reasonable assumptions, governing equations of the inside fluid areestabllshed. The corresponding discretizated equations are solved by employing numerical methods.The calculated results are displayed for velocity and temperature profiles on different cross-sectionalplanes, which present the flow pattern characterized by upflow and dowallow along the axial direc-tion and adherent flow along the peripheral direction, and the heat transfer process from the wall tothe center. Furthermore, the transient Nusselt number and average temperature level are shown anddiscussed. Finally, the parametric effects of the tube radius and the heat input on the flow and heattransfer are also given.
文摘Forced convective heat transfer in micro-rectangular channels can be described by a group of twodimensional differential equations. These equations take the conduction in microchannel wb along the direction of flow of coolants into account, which are more generalized than those which neglect the conduction. For the same reason, they are suitable particularly for gases-cooled microchannels.With only numerical solution to the equations till today, an approximate analytic solution is derived here. From this solution, a rather simple formula can be introduced bober, by which the differences between considering the conduction and neglecting it are easily found. In addition, the rcasonableness of the classical fin method is also discussed. An experimental example of air-cooled microchannels is illustrated.
