Detached Eddy Simulation方法模拟不同类型翼型的失速特性

应用DES(DetachedEddySimulation)方法数值模拟了3种不同失速类型的翼型的升力特性。DES方法结合了RANS(ReynoldsaveragedNavierStokes)和LES(LargeEddySimulationapproaches)的优点。基于SpalartAllmaras湍流模型,在近壁面DES体现为RANS模型的特点而在远离物面处又具有LES的亚格子模型的特性。对此模型使用了LUSGS隐式格式求解。通过和实验结果对比,显示这种方法可以有效地预测翼型的失速特性。

E-CONCAVE: Passive Design of Solar Detached House

With current resources shortages and environmental destruction,one of the important methods in building energy saving is to develop passive design and technologies. "E-concave",which is one of the entries in the Solar Decathlon 2013,has the core concepts of"Saving",Comfort","Unitization"and"Technology"and brings passive strategies( layout,insulation,daylighting,ventilation,material,etc.) into the design. This article aims to explore the utilization of passive design in solar detached houses through the studies on E-concave and tries to be an example to the development of sustainable buildings in China.

Detached eddy simulation on the structure of swirling jet flow field

The improved delayed detached eddy simulation method with shear stress transport model was used to analyze the evolution of vortex structure,velocity and pressure fields of swirling jet.The influence of nozzle pressure drop on vortex structure development and turbulence pulsation was investigated.The development of vortex structure could be divided into three stages:Kelvin-Helmholtz(K-H)instability,transition stage and swirling flow instability.Swirling flow could significantly enhance radial turbulence pulsation and increase diffusion angle.At the downstream of the jet flow,turbulence pulsation dissipation was the main reason for jet velocity attenuation.With the increase of pressure drop,the jet velocity,pulsation amplitude and the symmetry of velocity distribution increased correspondingly.Meanwhile the pressure pulsation along with the axis and vortex transport intensity also increased significantly.When the jet distance exceeded about 9 times the dimensionless jet distance,the impact distance of swirling jet could not be improved effectively by increasing the pressure drop.However,it could effectively increase the swirl intensity and jet diffusion angle.The swirling jet is more suitable for radial horizontal drilling with large hole size,coalbed methane horizontal well cavity completion and roadway drilling and pressure relief,etc.

Comparison of Passive Control Methods on Cavity Aeroacoustic Using Delayed Detached Eddy Simulation

Delayed detached eddy simulation(DDES)is performed to investigate an open cavity at Ma0.85.Clean cavity and cavity with leading-edge saw tooth spoiler and flattop spoiler,are modeled.The results obtained from clean cavity prediction are compared with experimental sound pressure level(SPL)data from QinetiQ,UK.DDES results agree well with the experimental data.Furthermore,comparisons are made with the predicted SPL between the three configurations to find out the effect of different passive control methods.Both the spoilers can suppress the over-all SPL up to 8dB.The main focuses of this investigation are to exam the DDES method on cavity aeroacoustic analysis and test the noise suppression effect by saw tooth spoiler and flattop spoiler.

Energy Saving Performance of Detached House with Hydrogen Co-generation System

Energy consumption is increasing every year in building sector, utilization and development of alternative energy sources and technologies to support the requirements of every house. The hydrogen fuel cell is one of the latest technologies for distributed energy systems. This research is aim to grasp the energy saving performance of the hydrogen co-generation system in the detached house. First, it investigated on the demand-side energy consumption including electricity, cooling, heating and hot water. Second, it introduced a distributed energy resources (DER) system and set six cases to analyze the energy utilization. Different options for changing the heating, cooling, electricity and hot water systems were compared for this type of detached house, assuming basiccase as a reference. Changes in the fuel used, energy operation machines and also demand side and supply side were analyzed. Except past case, every case will be operated under the electricitytracking mode and heat-tracking mode. The comparisons and evaluations of the energy consumption between cases can suggest the environmental performance of the hydrogen co-generation system.

The Influence of Inflow Condition on the Generation of Tumbling Flow Using Detached Eddy Simulation

One of the objectives of car manufacturers is to improve engine performance, reduce consumption reduce emissions. To achieve this objective, it is important to understand the phenomena involved in the combustion chambers of engines. These phenomena are numerous and complex in nature such: the aerodynamics, fuel-air mixture, turbulence, combustion and the cycle to cycle instabilities that cause more problems. One of the factors responsible for the phenomenon of cycle to cycle variations is the instability of the characteristics of the vortex flow Tumble. This instability may be due to changes in initial conditions. This study is achieved in order to contribute in a better understanding of engine flow by using a Detached Eddy Simulation Shear-Stress Transport (DES SST) model, which is a hybrid RANS/LES model. These simulations have been performed with the commercial CFD (computational fluid dynamic) code (FLUENT) coupled with our own development based on UDF facilities given by FLUENT. To explore the suitability of the 3D DES STT to simulate the internal flow, the calculation is performed for a model tumbling flow at constant volume. This flow has been measured in an experimental set up and measurements are used to initiate and to validate simulations. For this case study, we consider simplified engine geometry. To generate tumbling motion, we use non-reacting DES with a single cycle (SC) strategy. Also, with this strategy we study the effect of initial conditions on the instabilities that accompany a vortex type tumble.

Detached-eddy simulation of turbulent coherent structures around groynes in a trapezoidal open channel

The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation(DES).A series of short groynes were included on a 1:3 side slope of the channel.This work focuses on the turbulent coherent structures around groynes on an uneven bottom.Flows around groyne fields are characterized by massive separation and highly unsteady vortices.DES can capture a wide spectrum of eddies at a lower computational cost than the large eddy simulation(LES)or direct numerical simulation(DNS).In the present work,a zonal DES model(ZDES)was used to simulate the flow around groynes.The ZDES model is a modified version of the DES designed to overcome the model-stress depletion(MSD)of the RANS/LES hybrid model.The vortex system consists of the horseshoe vortex(HV)formed at the base of the obstructions,the necklace vortex(NV)that wrapped the groyne tips near the free surface,and the shedding vortex(SV)underneath the free surface.The effects of the incident flow and local topography on the vortex evolution were investigated by analyzing the mean flow structures and the instantaneous turbulent flow fields.Some important vortices cannot be captured because of the averaging process,while some flow structures cannot be observed in the instantaneous flow.The mean flow is only a reflection of the averaging process when complex vortices are present.

Delayed Detached Eddy Simulation of Subcritical Flow past Generic Side Mirror

In the present study, the subcritical flow past a generic side mirror on a base plane is investigated at the Reynolds number of 5.2 × 10~5 using delayed detached eddy simulation(DDES) turbulence model. Asides from the capability of capturing main features of the large recirculation vortex in the wake of the side mirror and the front horseshoe vortex, the accuracy of DDES estimation of recirculation length is significantly increased by over20%, compared to the detached eddy simulation(DES) estimation using the same grid. And DDES prediction of pressure coefficient at the trailing edge of the mirror is in good agreement with the experiments, which is more accurate than both DES and large eddy simulation(LES) results. The results verify the capacity of DDES turbulence model to solve the turbulent flow around the side mirror. This is a key foundation for possible future study of full simulation of external flow field of vehicle.

Origin of tradeoff between movement velocity and attachment duration of kinesin motor on a microtubule

Kinesin-1 motor protein is a homodimer containing two identical motor domains connected by a common long coiledcoil stalk via two flexible neck linkers. The motor can step on a microtubule with a velocity of about 1 μm·s-1and an attachment duration of about 1 s under physiological conditions. The available experimental data indicate a tradeoff between velocity and attachment duration under various experimental conditions, such as variation of the solution temperature,variation of the strain between the two motor domains, and so on. However, the underlying mechanism of the tradeoff is unknown. Here, the mechanism is explained by a theoretical study of the dynamics of the motor under various experimental conditions, reproducing quantitatively the available experimental data and providing additional predictions. How the various experimental conditions lead to different decreasing rates of attachment duration versus velocity is also explained.

Pars plana vitrectomy for retinal detachment using perfluoro-n-octane as intraoperative tamponade:a multicenter,randomized,non-inferiority trial

AIM:To evaluate the efficacy and safety of perfluoro-n-octane(PFO)for ophthalmic surgery versus F-Octane as an intraoperative tamponade in pars plana vitrectomy(PPV)in management of retinal detachment.METHODS:This multicenter,prospective,randomized,double-masked,parallel-controlled,non-inferiority trial was conducted in three ophthalmology clinical centers in China.Patients with retinal detachment,who were eligible for PPV were consecutively enrolled.Participants were assigned to PFO for ophthalmic surgery or F-Octane for intraocular tamponade in a 1:1 ratio.Best-corrected visual acuity(BCVA),intraocular pressure(IOP)measurement,and dilated fundus examination were performed preoperatively and at 1,7±1,28±3d postoperatively.The primary outcome was complete retinal reattachment rate at postoperative day one.The non-inferiority margin was set at 9.8%.The secondary outcomes included intraoperative retinal reattachment rate,and mean changes in IOP and BCVA from baseline to 1,7±1,28±3d postoperatively,respectively.Safety analyses were presented for all randomly assigned participates in this study.RESULTS:Totally 124 eligible patients completed the study between Mar.14,2016 and Jun.7,2017.Sixty of them were randomly assigned to the PFO for ophthalmic surgery group,and 64 were assigned to the F-Octane group.Baseline characteristics were comparable between the two groups.Both groups achieved 100%retinal reattachment at postoperative day one(difference 0,95%CI:-6.21%to 5.75%,P=1).The pre-defined noninferiority criterion was met.No significant difference was observed in intraoperative retinal reattachment rate(difference 1.77%,P=0.61),mean changes in IOP(difference 0.36,-0.09,2.22 mm Hg at 1,7±1,28±3d postoperatively,with all P>0.05)and BCVA(difference 0.04,-0.02,0.06 logMAR at 1,7±1,28±3d postoperatively,all P>0.05)between the two groups.No apparent adverse events related to the utilization of PFO were reported.CONCLUSION:In patients with retinal detachment undergoing PPV,PFO for ophthalmic surgery is non-inferior to F-Octane as an intraocular tamponade,and both are safe and well-tolerated.

Detachable string magnetically controlled capsule endoscopy for the noninvasive diagnosis of esophageal diseases:A prospective,blind clinical study

BACKGROUND Traditional esophagogastroduodenoscopy(EGD),an invasive examination method,can cause discomfort and pain in patients.In contrast,magnetically controlled capsule endoscopy(MCE),a noninvasive method,is being applied for the detection of stomach and small intestinal diseases,but its application in treating esophageal diseases is not widespread.AIM To evaluate the safety and efficacy of detachable string MCE(ds-MCE)for the diagnosis of esophageal diseases.METHODS Fifty patients who had been diagnosed with esophageal diseases were pros-pectively recruited for this clinical study and underwent ds-MCE and conven-tional EGD.The primary endpoints included the sensitivity,specificity,positive predictive value,negative predictive value,and diagnostic accuracy of ds-MCE for patients with esophageal diseases.The secondary endpoints consisted of visualizing the esophageal and dentate lines,as well as the subjects'tolerance of the procedure.RESULTS Using EGD as the gold standard,the sensitivity,specificity,positive predictive value,negative predictive value,and diagnostic accuracy of ds-MCE for esophageal disease detection were 85.71%,86.21%,81.82%,89.29%,and 86%,respectively.ds-MCE was more comfortable and convenient than EGD was,with 80%of patients feeling that ds-MCE examination was very comfortable or comfortable and 50%of patients believing that detachable string v examination was very convenient.CONCLUSION This study revealed that ds-MCE has the same diagnostic effects as traditional EGD for esophageal diseases and is more comfortable and convenient than EGD,providing a novel noninvasive method for treating esophageal diseases.

Non-contact wide-field viewing system-assisted scleral buckling surgery for retinal detachment in silicone oilfilled eyes

AIM:To evaluate scleral buckling(SB)surgery using a noncontact wide-field viewing system and 23-gauge intraocular illumination for the treatment of rhegmatogenous retinal detachment in silicone oil(SO)-filled eyes.METHODS:Totally 9 patients(9 eyes)with retinal detachment in SO-filled eyes were retrospectively analyzed.All patients underwent non-contact wide-field viewing system-assisted buckling surgery with 23-gauge intraocular illumination.SO was removed at an appropriate time based on recovery.The patients were followed up for at least 3mo after SO removal.Retinal reattachment,complications,visual acuity and intraocular pressure(IOP)before and after surgery were observed.RESULTS:Patients were followed up for a mean of 8.22mo(3-22mo)after SO removal.All patients had retinal reattachment.At the final follow-up,visual acuity showed improvement for 8 patients,and no change for 1 patient.The IOP was high in 3 patients before surgery,but it stabilized after treatment;it was not affected in the other patients.None of the patients had infections,hemorrhage,anterior ischemia,or any other complication.CONCLUSION:This new non-contact wide-field viewing system-assisted SB surgery with 23-gauge intraocular illumination is effective and safe for retinal detachment in SO-filled eyes.

Outcomes and variables that impact pneumatic retinopexies

●AIM:To evaluate the efficacy of pneumatic retinopexy(PR)in patients undergoing PR as primary treatment for rhegmatogenous retinal detachment(RRD)and analyze the factors associated with success and failure in the studied population.●METHODS:A retrospective chart review was done of patients with RRD treated with PR as primary management method treated at New York Eye and Ear Infirmary of Mount Sinai between January 2017 and December 2021.Primary outcome measured success or failure of PR.Secondary outcome measured best corrected visual acuity(BCVA)after PR.A separate risk analysis was done to identify and stratify risks associated with success and failure of PR.●RESULTS:A total of 179 eyes from 179 patients were included for final analysis.The 83 patients(46.37%)achieved anatomical reattachment of the retina after primary PR with no need for additional surgery.The 96 patients(53.63%)had a failed primary PR and required a PPV and 6 of them required pars plana vitrectomy(PPV)with scleral buckle(SB).In total,19 cases(10.61%)were done as temporizing pneumatics,18(94.74%)underwent PPV,and 1(5.26%)did not require further intervention.The visual acuities at postoperative month 1(POM1)for patients who underwent primary PR successfully and for those that underwent PPV after,were 0.58(20/80)and 1.03(20/200)respectively.Patients who met Pneumatic Retinopexy Versus Vitrectomy for the Management of Primary Rhegmatogenous Retinal Detachment Outcomes Randomized Trial(PIVOT)criteria had a statistically significant decreased risk of primary PR failing(hazard ratio 0.29,P=0.00).Majority of missed or new breaks were found superotemporally.●CONCLUSION:PR is a good treatment option for treating RRDs in patients that meet PIVOT criteria and can be conducted as a temporizing measure.PIVOT criteria and fovea on status decrease the risk of PR failure.

Efficacy of scleral buckling for the treatment of rhegmatogenous retinal detachment using a novel foldable capsular buckle

●AIM:To evaluate the effectiveness and safety of scleral buckling for the treatment of rhegmatogenous retinal detachment(RRD)using a novel foldable capsular buckle(FCB).●METHODS:This was a series of case observation studies.Eighteen patients(18 eyes)who visited our ophthalmology department between August 2020 and August 2022 and were treated for RRD with scleral buckling using FCB were included.The procedure was similar to conventional scleral buckling,while a balloon-like FCB was placed onto the retinal break with balanced salt solution filling for a broad,external indentation instead of the silicone buckle.The retinal reattachment rate,best corrected visual acuity(BCVA),intraocular pressure(IOP),refractive dioptre and astigmatism degree,and complications were evaluated and recorded.●RESULTS:There were 7 males and 11 females aged 19-58y.The average time course of RRD was 12d,ranging from 7-20d.The retinal break was located in the superior quadrants in 8 eyes and in the inferior quadrants in 10 eyes,with macula-off detachments in 12 eyes.The patients were followed-up for at least 6mo.The final retinal reattachment rate was 100%.The BCVA was significantly improved compared with the baseline(P<0.05).There was no significant change in refractive dioptre or astigmatism degree at each follow-up(all P>0.05).Three patients had transiently high IOPs within one week after surgery.Mild diplopia occurred in 5 patients after surgery and then disappeared after the balloon fluid was removed.●CONCLUSION:The success rate of FCB scleral buckling for RRD is satisfactory.This procedure can be expected to be applied in new,uncomplicated cases of RRD.

Rhegmatogenous retinal detachment in highly myopic eyes with implantable collamer lens

AIM:To investigate the clinical characteristics,treatment methods and outcomes of rhegmatogenous retinal detachment(RRD)in highly myopic eyes with implantable collamer lens(ICL).METHODS:High myopia patients who received treatment for nontraumatic RRD after ICL implantation surgery at the Retinal Department of Zhongshan Ophthalmic Center from Jan 2018 to Dec 2022 were reviewed.Comprehensive ophthalmologic examinations including visual acuity measurement and digital fundus photography were performed in each patient.RESULTS:A total of nine RRD eyes from nine patients who received V4c-ICL implantation were included.The mean time from ICL implantation surgery to the diagnosis of RRD was 32.44±22.56mo(range,1-60mo).At the initial visit for RRD,giant retinal tear(GRT),horseshoe tear,simple round hole,and horseshoe tear combined with round hole were detected in 3,3,2,and 1 eye(s),respectively,with maculaoff in eyes.Eight patients received surgical treatment,and one patient was treated by retinal laser photocoagulation alone.The ICL was preserved in 7 eyes.At the last followup,the mean best corrected visual acuity(BCVA)improved significantly from 1.76±1.06 logMAR at presentation to 0.81±1.01 logMAR(P=0.035),and no case of recurrent retinal detachment was found.CONCLUSION:The morphological presentation of retinal breaks is diverse in this study.The ICL can be preserved in most cases during the course of retinal detachment repair surgery in our data,companied with acceptable visual and anatomical outcomes.

Left atrial appendage occluder detachment treated with transthoracic ultrasound combined with digital subtraction angiography guided catcher:A case report

BACKGROUND There are very few cases of cardiac occluder detachment,and it is rare to completely remove the occluder using interventional methods without undergoing thoracotomy surgery after detachment.This case innovatively used ultrasound guidance combined with digital subtraction angiography(DSA)to completely remove the occluder,accumulating some experience.CASE SUMMARY The patient underwent left atrial appendage occlusion surgery in our hospital due to atrial fibrillation.After the surgery,the occluder fell off and became free in the left ventricle,which is very dangerous.We innovatively used ultrasound guidance,combined with DSA,and interventional surgery to successfully capture the free occluder using a catcher,completely remove it,and then re implant a new left atrial appendage occluder.After the surgery,the patient recovered very well.CONCLUSION The size selection of the occluder is slightly conservative,and the shape of the left atrial appendage opening is irregular.

On the vorticity behind 3-D detached bow shock wave

For the general case of a spatial isoenergetic flow of ideal gas,Helmholtz’s theorems are generalized and the speed with which vortex tubes move is found,keeping the intensity.It is shown that along the streamline without stagnation point,vorticity either is equal to zero everywhere,or it is non zero at all.The pattern of vortex lines behind the three-dimensional detached bow shock wave is specified.

Closed thoracic drainage in elderly patients with chronic obstructive pulmonary disease complicated with spontaneous pneumothorax:A retrospective study

BACKGROUND Chronic obstructive pulmonary disease(COPD)combined with spontaneous pneumothorax,is characterized by significant decline in lung function,and even cause cardiopulmonary failure and hypoxia.AIM To evaluate the clinical effectiveness of central venous catheters and indwelling pleural catheters(IPC)in managing closed thoracic drainage in patients diagnosed with COPD with concomitant by spontaneous pneumothorax.METHODS Retrospective analysis was conducted on the clinical information of 60 elderly patients with COPD complicated by spontaneous pneumothorax admitted to the Shexian Branch of the second affiliated hospital of Zhejiang university school of medicine between March 2020 and March 2023.The clinical efficacy,complications,hospitalization duration,and costs were compared between patients with an indwelling thoracic catheter and those with a central venous catheter.Univariate logistic regression was used to analyze the causes of catheter displacement.RESULTS According to our findings,there were significant differences in the IPC group’s clinical efficacy,catheter operation time,and lung recruitment time(P<0.05).Comparing the complications after catheter treatment between the two groups revealed statistically significant variations in the incidence of postoperative analgesics,catheter abscission,catheter blockage,and subcutaneous emphysema in the IPC group(P<0.05).Univariate analysis demonstrated significant differences between patients with and without catheter dislodgement regarding duty nurse’s working years(less than three),Acute Physiology and Chronic Health Evaluation II(APACHE II)scores(less than 15),lack of catheter suture fixation,and the proportion of catheters not fixed twice(P<0.05).CONCLUSION Our results demonstrated that when treating elderly COPD patients with spontaneous pneumothorax,indwelling thoracic catheters are more effective than the central venous catheter group.Patients’catheter shedding is influenced by the primary nurse’s working years,APACHE II scores,and catheter fixation technique.

A novel way for vibration control of FGM fluid-conveying pipes via NiTiNOL-steel wire rope

In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method(GTM)and harmonic balance method(HBM).The harmonic balance solutions and the numerical results are consistent.Also,the linearized stability of the structure is determined.The effects of the structure parameters on the absorption performance are also studied.The results show that the NiTi-ST is an effective means of vibration absorption.Furthermore,in studying the effect of the NiTi-ST,a closed detached response(CDR)is first observed.It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR.This vibration absorption device can be extended to offer more general vibration control in engineering applications.

Hybrid URANS/LES Method of Flow Fields in Axial-flow Compressor Rotor Rotor

Accurate and efficient prediction of the aerodynamic performance and flow details of axial-flow com-pressors is of great engineering application value for the aerodynamic design and flow control of axial-flow compres-sors.In this work,a delayed detached eddy simulation method is developed and applied to numerically simulate the tur-bulent channel flow and the aerodynamic performance of NASA Rotor 35.Several acceleration techniques including parallel implementation are also used to speed up the iteration convergence.The mean velocity distribution and Reyn-olds stress distribution in the boundary layer of turbulent channel flow and the aerodynamic performance curve of NASA Rotor 35 are predicted.The good agreement between the present delayed detached eddy simulation results and the available direct numerical simulation results or experimental data confirms the effectiveness of the developed meth-od in the accurate and efficient prediction of complex flow in turbomachinery.