Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

Design and test of pneumatic artificial muscle driven variable trailing-edge camber wing

A variable camber wing driven by pneumatic artificial muscles is developed in this paper. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed and the relationship between the static output force and the air pressure is investigated. Experimental results show that the static output force of pneumatic artificial muscle decreases nonlinearly with the increase of contraction ratio. Secondly, the model of variable camber wing driven by pneumatic artificial muscles is manufactured to validate the variable camber concept. Finally, wind tunnel tests are conducted in the low speed wind tunnel. It is found that the wing camber increases with the increase of air pressure. When the air pressure of PAMs is 0.4 MPa and 0.5 MPa, the tip displacement of the trailing-edge is 3 mm and 5 mm, respectively. The lift of aerofoil with flexible trailing-edge increases by 87% at AOA of 5°.

Follow-up strategy for early detection of delayed pseudoaneurysms in patients with blunt traumatic spleen injury: A single-center retrospective study

BACKGROUND The spleen is the most commonly injured solid organ in blunt abdominal trauma,and splenic pseudoaneurysm rupture is associated with a high risk of mortality.Nonoperative management has become the standard treatment for hemodynam-ically stable patients with splenic injuries.On the other hand,delayed splenic pseudoaneurysms can develop in any patient,and at present,there are no known risk factors that may reliably predict their occurrence.Furthermore,there is a lack of consensus regarding the most appropriate strategies for monitoring and mana-ging splenic injuries,especially lower-grade(I-III).AIM To determine the predictors of pseudo-aneurysm formation following splenic injury and develop follow-up strategies for early detection of pseudoaneurysms.METHODS We retrospectively analyzed patients who visited the Level I Trauma Center bet-ween January 2013 and December 2022 and were diagnosed with spleen injuries after blunt abdominal trauma.RESULTS Using the American Association for the Surgery of Trauma spleen injury scale,the splenic injuries were categorized into the following order based on severity:Grade I(n=57,17.6%),grade II(n=114,35.3%),grade III(n=89,27.6%),grade IV(n=50,15.5%),and grade V(n=13,4.0%).Of a total of 323 patients,35 underwent splenectomy and 126 underwent angioembolization.19 underwent delayed angioembolization,and 5 under-went both initial and delayed angioem-bolization.In 14 patients who had undergone delayed angioembolization,no extravasation or pseudoaneurysm was observed on the initial computed tomography scan.There are no particular patient-related risk factors for the formation of a delayed splenic pseudoaneurysm,which can occur even in a grade I spleen injury or even 21 days after the injury.The mean detection time for a delayed pseudoaneurysm was 6.26±5.4(1-21,median:6,inter-quartile range:2-9)days.CONCLUSION We recommend regular follow-up computed tomography scans,including an arterial and portal venous phase,at least 1 week and 1 month after injury in any grade of blunt traumatic spleen injury for the timely detection of delayed pseudoaneurysms.

Pelvic fractures in blunt trauma patients:A comparative study

BACKGROUND Pelvic fractures(PF)with concomitant injuries are on the rise due to an increase of high-energy trauma.Increase of the elderly population with age related comorbidities further complicates the management.Abdominal organ injuries are kindred with PF due to the proximity to pelvic bones.Presence of contrast blush(CB)on computed tomography in patients with PF is considered a sign of active bleeding,however,its clinical significance and association with outcomes is debatable.AIM To analyze polytrauma patients with PF with a focus on the geriatric population,co-injuries and the value of contrast blush.METHODS This retrospective cohort study included 558 patients with PF admitted to level 1 trauma center(01/2017-01/2023).Analyzed variables included:Age,sex,mechanism of injury(MOI),injury severity score(ISS),Glasgow coma scale(GCS),abbreviated injury scale(AIS),co-injuries,transfusion requirements,pelvic angiography,embolization,laparotomy,orthopedic pelvic surgery,intensive care unit and hospital lengths of stay,discharge disposition and mortality.The study compared geriatric and non-geriatric patients,patients with and without CB and abdominal co-injuries.Propensity score matching was implemented in comparison groups.RESULTS PF comprised 4%of all trauma admissions.89 patients had CB.286(52%)patients had concomitant injuries including 93(17%)patients with abdominal co-injuries.Geriatric patients compared to non-geriatric had more falls as MOI,lower ISS and AIS pelvis,higher GCS,less abdominal co-injuries,similar CB and angio-embolization rates,less orthopedic pelvic surgeries,shorter lengths of stay and higher mortality.After propensity matching,orthopedic pelvic surgery rates remained lower(8%vs 19%,P<0.001),hospital length of stay shorter,and mortality higher(13%vs 4%,P<0.001)in geriatric patients.Out of 89 patients with CB,45(51%)were embolized.After propensity matching,patients with CB compared to without CB had more pelvic angiography(71%vs 12%,P<0.001),higher embolization rates(64%vs 22%,P=0.02)and comparable mortality.CONCLUSION Half of the patients with PF had concomitant co-injuries,including abdominal co-injuries in 17%.Similarly injured geriatric patients had higher mortality.Half of the patients with CB required an embolization.

Response of a hypersonic blunt cone boundary layer to slow acoustic waves with assessment of various routes of receptivity

The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundarylayer unstable mode. In this paper, two routes of receptivity are investigated in detail.One is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.

Stability analysis and transition prediction of hypersonic boundary layer over a blunt cone with small nose bluntness at zero angle of attack

Stability and transition prediction of hypersonic boundary layer on a blunt cone with small nose bluntness at zero angle of attack was investigated. The nose radius of the cone is 0.5 mm; the cone half-angle is 5°, and the Mach number of the oncoming flow is 6. The base flow of the blunt cone was obtained by direct numerical simulation. The linear stability theory was applied for the analysis of the first mode and the second mode unstable waves under both isothermal and adiabatic wall condition, and e^N method was used for the prediction of transition location. The N factor was tentatively taken as 10, as no experimentally confirmed value was available. It is found that the wall temperature condition has a great effect on the transition location. For adiabatic wall, transition would take place more rearward than those for isothermal wall. And despite that for high Mach number flows, the maximum amplification rate of the second mode wave is far bigger than the maximum amplification rate of the first mode wave, the transition location of the boundary layer with adiabatic wall is controlled by the growth of first mode unstable waves. The methods employed in this paper are expected to be also applicable to the transition prediction for the three dimensional boundary layers on cones with angle of attack.

Instantaneous and time-averaged flow structures around a blunt double-cone with or without supersonic film cooling visualized via nano-tracer planar laser scattering

In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scattering （NPLS）, which has a high spatiotemporal resolution. Three experimental cases with different injection mass flux rates were carried out. Many typical flow structures were clearly shown, such as shock waves, expansion fans, shear layers, mixing layers, and turbulent boundary layers. The analysis of two NPLS images with an interval of 5 us revealed the temporal evolution characteristics of flow structures. With matched pressures, the laminar length of the mixing layer was longer than that in the case with a larger mass flux rate, but the full covered region was shorter. Structures like K-H （Kelvin-Helmholtz） vortices were clearly seen in both flows. Without injection, the flow was similar to the supersonic flow over a backward- facing step, and the structures were relatively simpler, and there was a longer laminar region. Large scale structures such as hairpin vortices were visualized. In addition, the results were compared in part with the schlieren images captured by others under similar conditions.

Spleen preserving distal pancreatectomy in an isolated blunt pancreatic trauma

Blunt isolated pancreatic trauma is uncommon,accounting for 1%-4% of high impact abdominal injuries.In addition,its diagnosis can be difficult;physical signs may be poor and laboratory findings nonspecific,resulting in delayed treatment.Preserving the spleen during distal pancreatectomy (DP) is controversial.One of the spleen's functions regards immunity;complications following splenectomy include leukocytosis,thrombocytosis,overwhelming post splenectomy sepsis and some degree of immunodeficiency.This is why many authors favor its preservation.We describe a case of a young man with an isolated pancreatic trauma due to a blunt abdominal trauma with a delayed presentation who was treated with spleen-preserving DP and we discuss the value of this procedure with reference to the literature.

Effect of disturbances at inlet on hypersonic boundary layer transition on a blunt cone at small angle of attack

To investigate the effect of different disturbances in the upstream, we present numerical simulation of transition for a hypersonic boundary layer on a 5-degree half-angle blunt cone in a freestream with Mach number 6 at 1-degree angle of attack. Evolution of small disturbances is simulated to compare with the linear stability theory （LST）, indicating that LST can provide a good prediction on the growth rate of the disturbance. The effect of different disturbances on transition is investigated. Transition onset distributions along the azimuthal direction are obtained with two groups of disturbances of different frequencies. It shows that transition onset is relevant to frequencies and amplitudes of the disturbances at the inlet, and is decided by the amplitudes of most unstable waves at the inlet. According to the characteristics of environmental disturbances in most wind tunnels, we explain why transition occurs leeside-forward and windside-aft over a circular cone at an angle of attack. Moreover, the indentation phenomenon in the transition curve on the leeward is also revealed.

Thoracic endovascular aortic repair with left subclavian artery reconstruction for blunt traumatic aortic injury in elderly patients

Introduction:Blunt thoracic aortic injury(BTAI)is rare in elderly patients.As the population ages and life expectancy increases,the frequency of this injury will increase,while the treatment and outcomes remain unclear.Methods:We retrospectively analyzed the collected data of patients>60 years old with BTAI to investigate the mechanism of trauma;time interval from injury to diagnosis;type and timing of surgical intervention;aortic arch pattern;choice of left subclavian artery reconstruction;endograft to treat BTAI;length of the endovascular procedure;endoleaks;complications including stroke,paraplegia,and renal failure;length of hospital stay(LOS)and intensive care unit stay(L.ICUS);and 30-day mortality.Results:Five elderly trauma patients were found to have BTAI.Four(80%)were males,the cohort mean age was68 years,the major mechanism of trauma was fall injury,and the associated injury was thoracic trauma.All patients were transferred to our hospital,and emergency computed tomography angiography showed BTAI in each patient.The average time interval from injury to diagnosis was 2.7 days.Two patients suddenly showed signs of instability in their vital signs and underwent immediate endovascular repair,while 3 patients underwent delayed endovascular repair.The injury site was located in the aortic isthmus just distal to the origin of the left subclavian artery;the aortic arch pattern was II(80.0%)in 4 cases and III in 1 case(20.0%).The choice of left subclavian artery reconstruction included chimney,double chimney,prefenestration,and chimney combined with in situ fenestration.Endografts to treat BTAI included the Ankura(Lifetech Scientific,Shenzhen,China)and the C-TAG(W.L.Gore&Associates,Flagstaff,AZ USA).The length of the endovascular procedure was 75.4 min;there were no endoleaks and no complications including stroke,paraplegia,or renal failure.The average LOS was25 days,and the average L.ICUS of 2 patients was 15 days,with no 30-day mortality.Conclusion:Elderly patients with fall injury should promptly exclude BTAI.Thoracic endovascular aortic repair(TEVAR)with a left subclavian artery reconstruction technique provided good results without procedure-related or neurological complications.Because of the low incidence of this type of injury,we are unable to provide any evidence to guide the treatment option for this life-threatening condition.

The impacts of different embolization techniques on splenic artery embolization for blunt splenic injury: a systematic review and meta-analysis

Background: Splenic artery embolization(SAE) has been an effective adjunct to the Non-operative management(NOM) for blunt splenic injury(BSI). However, the optimal embolization techniques are still inconclusive. To further understand the roles of different embolization locations and embolic materials in SAE, we conducted this system review and meta-analyses.Methods: Clinical studies related to SAE for adult patients were researched in electronic databases, included Pub Med, Embase, Science Direct and Google Scholar Search(between October 1991 and March 2013), and relevant information was extracted. To eliminate the heterogeneity, a sensitivity analysis was conducted on two reduced study sets. Then, the pooled outcomes were compared and the quality assessments were performed using Newcastle-Ottawa Scale(NOS). The SAE success rate, incidences of life-threatening complications of different embolization techniques were compared by χ2 test in 1 st study set. Associations between different embolization techniques and clinical outcomes were evaluated by fixed-effects model in 2 nd study set.Results: Twenty-three studies were included in 1 st study set. And then, 13 of them were excluded, because lack of the necessary details of SAE. The remaining 10 studies comprised 2 nd study set, and quality assessments were performed using NOS. In 1 st set, the primary success rate is 90.1% and the incidence of life-threatening complications is 20.4%, though the cases which required surgical intervention are very few(6.4%). For different embolization locations, there was no obvious association between primary success rate and embolization location in both 1 st and 2 nd study sets(P >0.05). But in 2 nd study set, it indicated that proximal embolization reduced severe complications and complications needed surgical management. As for the embolic materials, the success rate between coil and gelfoam is not significant. However, coil is associated with a lower risk of life-threatening complications, as well as less complications requiring surgical management.Conclusion: Different embolization techniques affect the clinical outcomes of SAE. The proximal embolization is the best option due to the less life-threatening complications. For commonly embolic material, coil is superior to gelfoam for fewer severe complications and less further surgery management.

Application of blunt dissection in ESD of a gastric submucosal tumor

We performed endoscopic submucosal dissection of a gastric fundus tumor.It was difficult to strip the tumor completely due to space limitation,and we used blunt dissection to remove the tumor quickly and safely.Firstly,the basal area of the 2.5 cm submucosal tumor located in the gastric fundus was cut open,and the mucosa was dissected.The tumor was difficult to peel,therefore,a snare was used and the tumor was pulled and tightened slightly.Short electronic coagulation was used during the procedure.The tumor was then bluntly dissected.This method ensured rapid and complete removal of the tumor.

Shielding effect and emission criterion of a screw dislocation near an interfacial blunt crack

Shielding effect and emission criterion of a screw dislocation near an interracial blunt crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial blunt crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the blunt crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interfacial blunt crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle. The critical loads at infinity for dislocation emission increases with the increase of emission angle and curvature radius of blunt crack tip, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.

Inflow boundary condition for DNS of turbulent boundary layers on supersonic blunt cones

For direct numerical simulation （DNS） of turbulent boundary layers, generation of an appropriate inflow condition needs to be considered. This paper proposes a method, with which the inflow condition for spatial-mode DNS of turbulent boundary layers on supersonic blunt cones with different Mach numbers, Reynolds numbers and wall temperature conditions can be generated. This is based only on a given instant flow field obtained by a temporal-mode DNS of a turbulent boundary layer on a flat plate. Effectiveness of the method is shown in three typical examples by comparing the results with those obtained by other methods.

Mathematical Model of Combustion in Blunt Annular Ceramic Burner

The computer simulation of the combustion process in blast furnace(BF) stove has been studied by using the k-ε-g turbulent diffusion flame model.The combustion process in blunt annular ceramic burner was calculated by using the software.The profiles of gas and air velocity,temperature of the combustion products,concentration of the components,and the shape and length of the flame during combustion have been researched.Compared with the original annular ceramic burner,the new design of the blunt one improves the mixing of the gas and the air significantly,and shortened the length of the flame.

Central retinal artery occlusion and traumatic optic neuropathy following blunt ocular trauma

Dear Editor,We are writing to present a case report of central retinal artery occlusion（CRAO）and traumatic optic neuropathy（TON）with immediate visual loss caused by blunt facial trauma with a soccer ball.CRAO is an ophthalmic emergency with an estimated incidence of 10 in 1 million.

Blunt diaphragmatic lesions: Imaging findings and pitfalls

Blunt diaphragmatic lesions (BDL) are uncommon in trauma patients, but they should be promptly recognized as a delayed diagnosis increases morbidity and mortality. It is well known that BDL are often overlooked at initial imaging, mainly because of distracting injuries to other organs. Sonography may directly depict BDL only in a minor number of cases. Chest X-ray has low sensitivity in detecting BDL and lesions can be reliably suspected only in case of intra-thoracic herniation of abdominal viscera. Thanks to its wide availability, time-effectiveness and spatial resolution, multi-detector computed tomography (CT) is the imaging modality of choice for diagnosing BDL; several direct and indirect CT signs are associated with BDL. Given its high tissue contrast resolution, magnetic resonance imaging can accurately depict BDL, but its use in an emergency setting is limited because of longer acquisition times and need for patient&#x02019;s collaboration.

Management of computed tomography scan detected hemothorax in blunt chest trauma:What computed tomography scan measurements say?

AIM To investigate the hemothorax size for which tube thoracostomy is necessary.METHODS Over a 5-year period, we included all patients who were admitted with blunt chest trauma to our level 1 trauma center. Focus was placed on identifying the hemothorax size requiring tube thoracostomy.RESULTS A total number of 274 hemothoraces were studied. All patients with hemothoraces measuring above 3 cm received a chest tube. The 50% predicted probability of tube thoracostomy was 2 cm. Pneumothorax was associated with odds of receiving tube thoracostomy for hemothoraces below 2 cm(Odds Ratio:4.967, 95%CI: 2.225-11.097, P < 0.0001).CONCLUSION All patients with a hemothorax size greater than 3% underwent tube thoracostomy. Prospective studies are warranted to elucidate the clinical outcome of patients with smaller hemothoraces.

Diagnosis and management of colonic injuries following blunt trauma

AIM: To retrospectively evaluate the preoperative diagnostic approaches and management of colonic injuries following blunt abdominal trauma. METHODS: A total of 82 patients with colonic injuries caused by blunt trauma between January 1992 and December 2005 were enrolled. Data were collected on clinical presentation, investigations, diagnostic methods, associated injuries, and operative management. Colonic injury-related mortality and abdominal complications were analyzed. RESULTS: Colonic injuries were caused mainly by motor vehicle accidents. Of the 82 patients, 58 (70.3%) had other associated injuries. Laparotomy was performed within 6 h after injury in 69 cases (84.1%), laparoscopy in 3 because of haemodynamic instability. The most commonly injured site was located in the transverse colon. The mean colon injury scale score was 2.8. The degree of faecal contamination was classified as mild in 18 (22.0%), moderate in 42 (51.2%), severe in 14 (17.1%), and unknown in 8 (9.8%) cases. Sixty-seven patients (81.7%) were treated with primary repair or resection and anastomosis. Faecal stream diversion was performed in 15 cases (18.3%). The overall mortality rate was 6.1%. The incidence of colonic injury- related abdominal complications was 20.7%. The only independent predictor of complications was the degree of peritoneal faecal contamination (P = 0.02). CONCLUSION: Colonic injuries following blunt trauma are especially important because of the severity and complexity of associated injuries. A thorough physical examination and a combination of tests can be used to evaluate the indications for laparotomy. One stage management at the time of initial exploration is mostoften used for colonic injuries.

Experimental study of multi-timescale crack blunting in hydraulic fracture

Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.