Impingement Area Research Articles

Conjugate heat transfer simulations of a radially cooled gas turbine blade leading edge using a vortex-based fluidic oscillator for sweeping jet impingement

The turbine blades of aero engines are subjected to extremely high temperatures, particularly at the leading edge, where temperatures can reach approximately 1800–2000 K. Therefore, effective heat load management is crucial. A vortex-based fluidic oscillator for sweeping jet impingement was proposed as an innovative cooling method to enhance heat transfer at leading edge of high-pressure gas turbine blades. This numerical investigation evaluates the cooling performance of a vortex-based sweeping jet compared to steady and conventional sweeping jets in a radially cooled high-pressure turbine blade. In this study, a conjugate heat transfer model based on three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations is employed. The shear stress transport (SST k–ω) model is specifically selected to predict the flow field and heat transfer characteristics of a vortex-based fluidic oscillator applied to the leading edge. To verify the accuracy of numerical calculations, two sets of experimental data were used as benchmark. The results demonstrated strong qualitative and quantitative agreement with experimental data. Various parameters, including coolant mass flow rates (0.171, 0.514, and 0.857 g/s), aspect ratios (0.5, 0.65, and 1), jet-to-wall spacings (H/D = 2, 4, and 6), and pressure drop, were examined to assess overall cooling effectiveness and heat transfer performance. Time-averaged and time-resolved flow field measurements revealed that vortex-based fluidic oscillator significantly enhanced cooling effects and covered a larger impinging area compared to a steady jet. Notably, the vortex-based fluidic oscillator achieved a 24.3% higher heat transfer performance than the steady jet at H/D = 2, with an average temperature decrease in approximately 21 K at leading edge.

Burning behavior of hydrogen jet flame inhibited by a wire mesh screen

Hydrogen is recognized as a promising energy source and the potential risks associated with leakage and jet fire accidents should be considered. The objective of this study is to explore the feasibility of utilizing wire mesh to suppress hydrogen jet flames. The experiments of hydrogen jet fire with ignitors below and above the wire mesh were performed to explore the effect of wire mesh on the burning behaviors at different mesh numbers, mesh-to-nozzle distances, and fuel flow rates. Compared to the free jet flame, the length of jet flame under the action of wire mesh is decreased by 50–90 %. The flame with topside ignition fails to pass through the mire mesh due to the cooling effect of the fuel jet. Experimental results reveal that the state of the flow field in the impingement area plays an important role in determining the upper flame height. Both the upper flame height and the flame extension length beneath the screen decrease with mesh-to-nozzle distance. As the mesh porosity decreases, the flame extension length increases, however, the upper flame height decreases. Based on the classical theory of flow resistance through porous media, a new dimensionless model was developed to predict the characteristic flame lengths of the jet flame inhibited by wire mesh. The findings presented in this paper offer fresh insight into the safeguarding of jet fires.

Morphologic changes in the posterior glenoid rim is independently associated with rotator cuff impingement in baseball players

BackgroundThe morphological changes in the posterior glenoid rim are unknown in relation to the area of rotator cuff tendons pinched within the glenohumeral joint in the throwing shoulders of baseball players. Therefore, this study aimed to clarify whether these changes are associated with the area of impingement in baseball players. MethodsOverall, 25 asymptomatic male college baseball players (average age19.8 years, 11.6 years of competing, and 50 shoulders) participated in this study. The area of impingement (AOI, mm2) and posterior glenohumeral distance (PGHD, mm) were measured using magnetic resonance imaging to quantitatively assess the impingement area of the rotator cuff tendon within the glenohumeral joint and the morphologic change in the posterior glenoid rim. These magnetic resonance imaging assessments were measured at 90° shoulder abduction with 90° and 100° external rotation. Multiple linear regression analysis was performed to determine whether AOI is predicted by PGHD. FindingsMultiple linear regression analysis showed that the PGHD was a predictor of the AOI at external rotation 90° (β-coefficient = 0.738, R2 = 0.77, P < 0.001) and external rotation 100° position (β-coefficient = 0.879, R2 = 0.76, P < 0.001). InterpretationThis study found that the area of impingement was associated with posterior glenohumeral distance. Therefore, these findings may indicate that complex shoulder joint morphologic changes result in a disabled throwing shoulder.

Comparison of range of motion between 2-year clinical outcomes and predictions of a static scapula preoperative planning software for reverse shoulder arthroplasty

BackgroundPreoperative planning has gained popularity in the management of reverse shoulder arthroplasty (RSA). Commercially available software provides 3-dimensional segmentation of scapula and humerus, as well as providing arc of motion for the implanted articulation and identifying potential areas of bony impingement. However, these software algorithms use a fixed scapula model, disregarding the preoperative clinical range of motion (C-ROM) of the patient, be it glenohumeral or scapulothoracic, as well as any soft tissue parameters. This study aims to compare the ROM based on preoperative planning software by using the implant position from postoperative computed tomography (CT) images (predicted ROM using preoperative planning software [P-ROM]), with the C-ROM assessed at minimum of 2 years of follow-up. MethodsPreoperative and postoperative CT scans of 46 patients who underwent primary RSA between 2017 and 2021 were analyzed. At the postoperative 2-year review, each patient was assessed for active ROM. Implant size and position based on operative notes and postoperative CT scans were used to replicate the performed surgery in the planning software. Abduction, flexion, and external rotation motion were simulated and recorded. The relationship between C-ROM and P-ROM was investigated using linear regression analysis, Pearson correlation coefficient, and paired t-test. ResultsP-ROM was significantly lower than C-ROM at 2 years postoperatively (P < .001), with an average discrepancy of 78° in abduction, 47° in flexion, and 37° in external rotation (C-ROM: abduction 155° ± 21° [80°-180°]; flexion 160° ± 17° [90°-180°]; external rotation 52° ± 14° [10°-80°] vs. P-ROM: abduction 77° ± 13° [53°-107°]; flexion 112° ± 25° [67°-180°]; external rotation 15° ± 21° [0°-79°]). The linear regression analysis indicated weak agreement between C-ROM and P-ROM (abduction R2 = 0.03; flexion R2 = 0.01; external rotation R2 = 0.04). Pearson’s correlation coefficients revealed weak correlations of −0.18, 0.03, and 0.21 for abduction, flexion, and external rotation, respectively. ConclusionP-ROM based on preoperative software in its current form does not allow the prediction of the C-ROM at 2 years of follow-up for patients undergoing RSA.

Characterization of near-wall flow and in-cylinder free-stream turbulence during the intake phase of a direct-injection engine: A flow bench study

This study investigates the characteristics of the near-wall flow and pressure-induced wall-influenced turbulence inside a direct-injection engine during the intake phase by utilizing a wall-resolved Large Eddy Simulation. An engine flow bench operating under stationary conditions is used to reduce the complexity of engine flows and to shed light on the in-cylinder flow during the intake phase. The investigation focuses on in-cylinder turbulence on symmetry (SP) and valve planes (VP), particularly emphasizing the flow close to the intake valves and the impingement region on the liner wall. An experimental dataset acquired through 2D high-speed particle image velocimetry (PIV) facilitates validation of the simulation of both time-averaged velocity field and associated turbulence structure. Turbulence anisotropy analysis shows that, in complex wall-bounded flows, the IC engine-related in-cylinder turbulence structure is characterized by the anisotropic states that cope with both axisymmetric expansion and contraction straining events. Due to the strong influence of the intake flow, the turbulence anisotropy level, expressed in terms of the two-componentality parameter F, retains its value of less than 0.85, and no turbulence occurs in accordance with the fully three-component isotropic state, characterized by the F-parameter value of 1. In the vicinity of the intake valve near wall area, the turbulence anisotropy state transitions from that resembling a canonical channel flow characteristic to curvature-induced acceleration after impingement, which aligns with axisymmetric expansion in the anisotropy invariant map. The presence of intake flow sustains turbulence anisotropy. Limitations in applying wall-function treatments for near-wall flow in engine contexts due to simplifications, such as the zero-pressure gradient assumption, are highlighted. In this respect, the interplay of non-equilibrium effects in the near-wall region needed to be further explored. Accordingly, analysis of the viscosity-affected layer near the intake valve and the flow impingement area of the liner wall underscores the importance of the wall-tangential pressure gradient in shaping the near-wall behavior. A budget analysis of the turbulent kinetic energy equation at the intake valve emphasizes the dominance of fluctuating pressure-induced diffusive transport in turbulence generation.

An In-Situ Analysis Method in EAF and BOF Steelmaking

An analysis was conducted to gage the feasibility of using a spectroscopic method to determine the chemical composition of the liquid metal phase in EAF and BOF steelmaking. The hypothesis that certain radiation intensities found in UV- and UV-near regions of an spectrum emitted from the hot-spot in the BOF or the impingement area of oxyfuel burners in EAF steelmaking can be used for analysing the chemical components present in the liquid metal is tested. Significant lab-scale experiment results and the conclusions regarding industrial scale implementation are presented.

Abstract 100: Endovascular treatment of a traumatic near‐miss vessel injury

Introduction Traumatic injuries are a common cause of death, representing nearly 8% of all deaths worldwide(1). Vascular injury can occur in about 3% to 20% of the patients that suffer from a blunt or penetrating craniocervical injury (2). The most commonly injured arteries from penetrating trauma include CCA, ICA, and ECA (73%,22%, and 5% respectively)(3). Embolization is now a well‐established endovascular technique to treat traumatic hemorrhagic injuries(4). We present a case of a patient with a near‐miss injury treated endovascularly. Methods We present the case of a 29‐year‐old male who was found unconscious with a knife embedded in his left face. On arrival at the hospital, the patient was hemodynamically stable with no ongoing hemorrhage or respiratory distress. CTA did not reveal any vascular injury; however, due to the knife's location, the neurointerventional radiology team was consulted and performed an embolization of the proximal third of the internal maxillary artery. The patient was later taken to the operating room for the removal of the knife. Results The non‐serrated end of the knife had resulted in impingement of the distal left ECA just proximal to the bifurcation of the superficial temporal artery and internal maxillary artery and resulting in approximately 80% narrowing of the vessel. Given the extent of impingement of the foreign object on the distal portion of the left ECA, after discussing with the otolaryngology team, a decision was made to proceed with coil embolization of the vessel due to concerns for vessel injury which can result in life‐threatening hemorrhage or pseudoaneurysm during removal of the foreign object in the OR. A total of 4 HydroFrame coils were deployed from the proximal one‐third of the internal maxillary artery into the ECA covering the superficial temporal artery to the origin of the occipital artery. 2 MicroPlex 5mm x 22cm Cosmos 10 bare platinum coils were placed intact to the left ECA extending proximally just distal to the occipital artery. Final AP projection of the left ECA post coil embolization was performed showing complete occlusion of the vessel across the area of impingement at the distal ECA proper. Retrograde filling of the internal maxillary artery was noted. The left middle meningeal artery is occluded and no longer visualized as its origin is being covered by coils. Patient underwent foreign object removal by ENT and had a good functional outcome. Conclusion Endovascular intervention prior to foreign object removal can improve outcomes and decrease the risk of severe vascular injury.

High hemodynamic stresses induce aneurysms at internal carotid artery bends

To investigate the role of hemodynamic stresses in initiating cerebral aneurysms at bends of internal carotid artery (ICA). Sixty-one patients with 68 aneurysms at ICA bends were retrospectively enrolled as the experiment group. Among the 61 patients, 30 normal ICAs without aneurysms were chosen as the control. All patients had 3-dimensional angiography and CFD analysis. The bending angle was significantly (P &lt; .0001) smaller in the experiment than control group (131.2º ± 14.9º vs 150.3º ± 9.5º). The dynamic pressure, shear stress, vorticity magnitude and strain rate were the least at direct flow impinging center where the total pressure was very high. The dynamic stress, shear stress, strain rate and gradients of total pressure except for gradient 1 were significantly (P &lt; .05) greater at the aneurysm site than at all the other sites. The total pressure at the aneurysm site was greater (P &lt; .05) than at 1 lateral location and at the distal area but smaller (P &lt; .05) than at the proximal area. The dynamic pressure, shear stress, strain rate and gradient of total pressure at the aneurysm site were significantly (P &lt; .001) greater than on the aneurysm dome. The hemodynamic stresses were all significantly (P &lt; .01) greater at the aneurysm site in the experiment group than at the site corresponding to the aneurysm in the control group. Aneurysms at the ICA bends are caused by direct flow impingement and increased hemodynamic stresses, and smaller arterial bending angles result in abnormally enhanced hemodynamic stresses to initiate an aneurysm near the flow impingement area.

Posterior Hip Impingement at Maximal Hip Extension in Female Patients With Increased Femoral Version or Increased McKibbin Index and Its Effect on Sports Performance.

The location of posterior hip impingement at maximal extension in patients with posterior femoroacetabular impingement (FAI) is unclear. To investigate the frequency and area of impingement at maximal hip extension and at 10° and 20° of extension in female patients with increased femoral version (FV) and posterior hip pain. Cross-sectional study; Level of evidence, 3. Osseous patient-specific 3-dimensional (3D) models were generated of 50 hips (37 female patients, 3D computed tomography) with a positive posterior impingement test and increased FV (defined as >35°). The McKibbin index (combined version) was calculated as the sum of FV and acetabular version (AV). Subgroups of patients with an increased McKibbin index >70° (24 hips) and FV >50° (20 hips) were analyzed. A control group of female participants (10 hips) had normal FV, normal AV, and no valgus deformity (neck-shaft angle, <139°). Validated 3D collision detection software was used for simulation of osseous impingement-free hip extension (no rotation). The mean impingement-free maximal hip extension was significantly lower in patients with FV >35° compared with the control group (15° ± 15° vs 55° ± 19°; P < .001). At maximal hip extension, 78% of patients with FV >35° had osseous posterior extra-articular ischiofemoral hip impingement. At 20° of extension, the frequency of posterior extra-articular ischiofemoral impingement was significantly higher for patients with a McKibbin index >70° (83%) and for patients with FV >35° (76%) than for controls (0%) (P < .001 for both). There was a significant correlation between maximal extension (no rotation) and FV (r = 0.46; P < .001) as well as between impingement area at 20° of extension (external rotation [ER], 0°) and McKibbin index (0.61; P < .001). Impingement area at 20° of extension (ER, 0°) was significantly larger for patients with McKibbin index >70° versus <70° (251 vs 44 mm2; P = .001). The limited hip extension found in our study could theoretically affect the performance of sports activities such as running, ballet dancing, or lunges. Therefore, although not examined directly in this study, these activities are not advisable for these patients. Preoperative evaluation of FV and the McKibbin index is important in female patients with posterior hip pain before hip preservation surgery (eg, hip arthroscopy).

Experimental investigation of jet impingement during accidental release of liquid CO2

Jet impingement and low-temperature damage are potential risks of accidental release during the transportation and storage of liquid CO2. An experimental system was built to investigate the characteristics of jet impingement of liquid CO2. The effects of orifice size and impinging distance on the impinging force of the jet and temperature of the target surface were investigated at 2.3 MPa and 5 MPa, with orifice sizes from 2 to 4.84 mm and impinging distances from 0.25 to 1.5 m. A jet impingement model was established considering the initial pressure, orifice size, impinging distance and impingement area. The experimental results indicated that dry-ice attached on the plate surface, reducing the surface temperature to −90 °C and improving the impinging force to 44.54 N with decreasing impingement distance. The variation in initial pressure had a more pronounced effect on the impinging force than on the impinging temperature, while the impingement distance had more influence on the impinging temperature than the orifice size and initial pressure. The results calculated with the model agreed well with the experimental results with an error of nearly less than 20%. The model was also used to analyse the effects of the initial pressure, liquid mass fraction, orifice size, impingement distance and impingement area on the release rate and impingement force.

MRI 3D simulation of hip motion in female patients with and without ischiofemoral impingement.

To utilize hip MRI 3D models for demonstration of location and frequency of impingement during simulated range-of-motion in ischiofemoral impingement (IFI) compared to non-IFI hips. Sixteen hips (N = 7 IFI, 9 non-IFI) from 8 females were examined with high-resolution MRI. We performed image segmentation and generated 3D bone models and simulated hip range-of-motion and impingement. We examined the frequency and location of bone contact in early external rotation and early extension (0-20°), isolated maximum external rotation, and isolated maximum extension. Frequency and location of impingement at varied combinations of external rotation and extension and areas of simulated bone impingement at early external rotation and extension were compared between IFI and non-IFI. Higher frequency of bony impingement occurred more often in IFI hips at each simulated range-of-motion combination (P < 0.05). Impingement involved the lesser trochanter more often in IFI hips (P < 0.001) and occurred at early degrees of external rotation and extension. In isolated maximum external rotation, only the greater trochanter, intertrochanteric area, or both combined were involved, in 14%, 57%, and 29% in IFI hips. In isolated maximum extension, the lesser trochanter, intertrochanteric area, or both combined were involved in 71%, 14%, and 14% in IFI hips. The simulated area of bone impingement was significantly higher in IFI hips (P = 0.02). Hip MRI 3D models are feasible for simulated range-of-motion and show a higher frequency of extra-articular impingement at early stages of external rotation and extension in IFI compared to non-IFI hips.

A Study on the Sensitivities of an Ice Protection System Combining Thermoelectric and Superhydrophobic Coating to Icing Environment Parameters

The hybrid Ice Protection System combining thermoelectric and superhydrophobic coating is efficient and benefits from low-energy consumption. In order to explore the application details of superhydrophobic coating, this paper investigated the sensitivities of the Ice Protection System parameters including the range of the superhydrophobic coating, heating range and power to icing environmental parameters. In this paper, an icing wind tunnel test was adopted to study the performance of this Ice Protection System under different icing conditions, as well as the influence of the superhydrophobic coating range, heating range and power variation on ice protection. The results showed that the superhydrophobic coating is effective only when it covers the droplet impingement area, with the heating power requirement emerging as a critical design consideration that is extremely sensitive to environmental temperature changes. Additionally, median volumetric diameter determines the protection area to be protected, while liquid water content variation has little effect on the designed Ice Protection System in contrast.

Flame extension length of inclined hydrogen jet fire impinging on a water curtain

The use of a water curtain system to prevent fire spread has been extensively investigated, but the case of an inclined jet fire inhibited with a water curtain is not involved. A series of experiments were conducted on inclined hydrogen jet fires with various fuel flow rates, nozzle diameters and inclination angles under the influence of a vertical water curtain. This study aims to explore the burning behaviors of inclined jet flames at the impingement area, specifically the flame extension lengths. The experimental results show that an increase in fuel flow rates or nozzle diameter leads to a larger flame extension length. With the increase of flame inclination angle, the flame extension length decreases and the influence of nozzle diameter on the flame extension length is attenuated. A new dimensionless heat release rate is proposed to correlate with the dimensionless flame extension length by incorporating an air entrainment coefficient. The model built in this study can be used to predict the flame extension length of jet flames with different diameters, fuel flows and inclinations under the influence of a water curtain, and is validated by data in the previous study.

Limited External Rotation and Hip Extension Due to Posterior Extra-articular Ischiofemoral Hip Impingement in Female Patients With Increased Femoral Anteversion: Implications for Sports, Sexual, and Daily Activities

Background: Posterior femoroacetabular impingement (FAI) is poorly understood. Patients with increased femoral anteversion (FV) exhibit posterior hip pain. Purpose: To correlate hip impingement area with FV and with combined version and to investigate frequency of limited external rotation (ER) and hip extension (<40°, <20°, and <0°) due to posterior extra-articular ischiofemoral impingement. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Osseous patient-specific three-dimensional (3D) models based on 3D computed tomography scans were generated of 37 female patients (50 hips) with positive posterior impingement test (100%) and increased FV >35° (Murphy method). Surgery was performed in 50% of patients (mean age, 30 years; 100% female). FV and acetabular version (AV) were added to calculate combined version. Subgroups of patients (24 hips) with increased combined version >70° and patients (9 valgus hips) with increased combined version >50° were analyzed. The control group (20 hips) had normal FV, normal AV, and no valgus. Bone segmentation was performed to generate 3D models of every patient. Validated 3D collision detection software was used for simulation of impingement-free hip motion (equidistant method). Impingement area was evaluated in combined 20° of ER and 20° of extension. Results: Posterior extra-articular ischiofemoral impingement occurred between the ischium and the lesser trochanter in 92% of patients with FV >35° in combined 20° of ER and 20° of extension. Impingement area in combined 20° of ER and 20° of extension was larger with increasing FV and with higher combined version; correlation was significant (P < .001, r = 0.57, and r = 0.65). Impingement area was significantly (P = .001) larger (681 vs 296 mm2) for patients with combined version >70° (vs <70°, respectively) in combined 20° of ER and 20° of extension. All symptomatic patients with increased FV >35° (100%) had limited ER <40°, and most (88%) had limited extension <40°. The frequency of posterior intra- and extra-articular hip impingement of symptomatic patients (100% and 88%, respectively) was significantly (P < .001) higher compared with the control group (10% and 10%, respectively). The frequency of patients with increased FV >35° with limited extension <20° (70%) and patients with limited ER <20° (54%) was significantly (P < .001) higher compared with the control group (0% and 0%, respectively). The frequency of completely limited extension <0° (no extension) and ER <0° (no ER in extension) was significantly (P < .001) higher for valgus hips (44%) with combined version >50° compared with patients with FV >35° (0%). Conclusion: All patients with increased FV >35° had limited ER <40°, and most of them had limited extension <20° due to posterior intra- or extra-articular hip impingement. This is important for patient counselling, for physical therapy, and for planning of hip-preservation surgery (eg, hip arthroscopy). This finding has implications and could limit daily activities (long-stride walking), sexual activity, ballet dancing, and sports (eg, yoga or skiing), although not studied directly. Good correlation between impingement area and combined version supports evaluation of combined version in female patients with positive posterior impingement test or posterior hip pain.

Can a Computational Model Predict the Effect of Lesion Location on Cam-type Hip Impingement?

The Warwick consensus defined femoroacetabular impingement syndrome as a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs, and imaging findings representing symptomatic premature contact between the proximal femur and acetabulum. Several factors appear to cause labral and cartilage damage, including joint shape and orientation and patient activities. There is a lack of tools to predict impingement patterns in a patient across activities. Current computational modeling tools either measure pure ROM of the joint or include complexity that reduces reliability and increases time to achieve a solution. The purpose of this study was to examine the efficacy of a low computational cost approach to combining cam-type hip shape and multiple hip motions for predicting impingement. Specifically, we sought to determine (1) the potential to distinguish impingement in individual hip shapes by analyzing the difference between a cam lesion at the anterior femoral neck and one located at the superior femoral neck; (2) sensitivity to three aspects of hip alignment, namely femoral neck-shaft angle, femoral version angle, and pelvic tilt; and (3) the difference in impingement measures between the individual activities in our hip motion dataset. A model of the shape and alignment of a cam-type impinging hip was created and used to describe two locations of a cam lesion on the femoral head-neck junction (superior and anterior) based on joint shape information available in prior studies. Sensitivity to hip alignment was assessed by varying three aspects from a baseline (typical alignment described in prior studies), namely, femoral neck-shaft angle, femoral version, and pelvic tilt. Hip movements were selected from an existing database of 18 volunteers performing 13 activities (10 male, eight female; mean age 44 ± 19 years). A subset was selected to maximize variation in the range of joint angles and maintain a consistent number of people performing each activity, which resulted in nine people per activity, including at least three of each sex. Activities included pivoting during walking, squatting, and golf swing. All selected hip motion cases were applied to each hip shape model. For the first part of the study, the number of motion cases in which impingement was predicted was recorded. Quantitative analyses of the depth of penetration of the cam lesion into the acetabular socket and qualitative observations of impingement location were made for each lesion location (anterior and superior). In the second part of the study, in which we aimed to test the sensitivity of the findings to hip joint orientation, full analysis of both cam lesion locations was repeated for three modified joint orientations. Finally, the results from the first part of the analysis were divided by activity to understand how the composition of the activity dataset affected the results. The two locations of cam lesion generated impingement in a different percentage of motion cases (anterior cam: 56% of motion cases; superior cam: 13% of motion cases) and different areas of impingement in the acetabulum, but there were qualitatively similar penetration depths (anterior cam: 6.8° ± 5.4°; superior cam: 7.9° ± 5.8°). The most substantial effects of changing the joint orientation were a lower femoral version angle for the anterior cam, which increased the percentage of motion cases generating impingement to 67%, and lower neck-shaft angle for the superior cam, which increased the percentage of motion cases generating impingement to 37%. Flexion-dominated activities (for example, squatting) only generated impingement with the anterior cam. The superior cam generated impingement during activities with high internal-external rotation of the joint (for example, the golf swing). This work demonstrated the capability of a simple, rapid computational tool to assess impingement of a specific cam-type hip shape (under 5 minutes for more than 100 motion cases). To our knowledge, this study is the first to do so for a large set of motion cases representing a range of activities affecting the hip, and could be used in planning surgical bone removal. The results of this study imply that patients with femoroacetabular impingement syndrome with cam lesions on the superior femoral head-neck junction may experience impinging during motions that are not strongly represented by current physical diagnostic tests. The use of this tool for surgical planning will require streamlined patient-specific hip shape extraction from imaging, model sensitivity testing, evaluation of the hip activity database, and validation of impingement predictions at an individual patient level.

Large Hip Impingement Area and Subspine Hip Impingement in Patients With Absolute Femoral Retroversion or Decreased Combined Version.

It remains unclear if femoral retroversion is a contraindication for hip arthroscopy in patients with femoroacetabular impingement (FAI). To compare the area and location of hip impingement at maximal flexion and during the FADIR test (flexion, adduction, internal rotation) in FAI hips with femoral retroversion, hips with decreased combined version, and asymptomatic controls. Cross-sectional study; Level of evidence, 3. Twenty-four symptomatic patients (37 hips) with anterior FAI were evaluated. All patients had femoral version (FV) <5° according to the Murphy method. Two subgroups were analyzed: 13 hips with absolute femoral retroversion (FV <0°) and 29 hips with decreased combined version (McKibbin index <20°). All patients were symptomatic and had anterior groin pain and a positive anterior impingement test ; all had undergone pelvic computed tomography (CT) scans to measure FV. The asymptomatic control group consisted of 26 hips. Dynamic impingement simulation of maximal flexion and FADIR test at 90° of flexion was performed with patient-specific CT-based 3-dimensional models. Extra- or intra-articular hip impingement area and location were compared between the subgroups and with control hips using nonparametric tests. Impingement area was significantly larger for hips with decreased combined version (<20°) versus combined version (≥20°) (mean ± SD; 171 ± 140 vs 78 ± 55 mm2; P = .012) and was significantly larger for hips with FV <0° (absolute femoral retroversion) vs FV >0° (P = .025). Hips with absolute femoral retroversion had a significantly higher frequency of extra-articular subspine impingement versus controls (92% vs 0%; P < .001), compared to 84% of patients with decreased combined version. Intra-articular femoral impingement location was most often (95%) anterosuperior and anterior (2-3 o'clock). Anteroinferior femoral impingement location was significantly different at maximal flexion (anteroinferior [4-5 o'clock]) versus the FADIR test (anterosuperior and anterior [2-3 o'clock]) (P < .001). Patients with absolute femoral retroversion (FV <0°) had a larger hip impingement area, and most exhibited extra-articular subspine impingement. Preoperative FV assessment with advanced imaging (CT/magnetic resonance imaging) could help to identify these patients (without 3-dimensional modeling). Femoral impingement was located anteroinferiorly at maximal flexion and anterosuperiorly and anteriorly during the FADIR test.

Flame characteristics and heat flux profile of a tank surface caused by horizontal gas leak jet fire impingement

Jet fire accidents caused by leaks in gas pipelines or gas tanks often occur, which may trigger a domino effect. The present work experimentally investigated the characteristics and heat flux profile of flames on a tank surface, with different leak hole-tank spacing and fuel initial velocity. The results show that, for any given leak hole diameter, the height and width of the impingement flame increase with an increasing heat release rate, whereas they decrease with an increase in the leak hole-tank spacing. The impingement flame height correlated well with the characteristic length Lm, which was used in free jet fires. Based on the balance of the momentum flux to the buoyancy flux of the horizontal jet fire, a new characteristic length scale and a dimensionless heat release rate was proposed. Meanwhile, some of the numerical results were also analyzed and the non-dimensional functional correlation for the flame width of the impinging area was proposed with the fire heat release rate and flame Froude number Frf. Finally, considering the effect of the unburned portion of the fuel with jet fire impinging the tank, a new correlation was proposed to describe the heat flux and temperature profile of the tank surface.

Recent Progress in Flow Control and Heat Transfer Enhancement of Impinging Sweeping Jets Using Double Feedback Fluidic Oscillators: A Review

Abstract Jet impingement finds an important role in several industrial applications which require high thermal-hydraulic performance of heat exchange systems. The self-exciting sweeping jets produced by fluidic oscillators provide superior thermal and hydraulic performance as compared to plain jets. The fluidic oscillator increases the jet impingement area on the target surface by maintaining a steady and controlled oscillatory flow. The continuous advancements in the design improvement of fluidic oscillators have led to further enhancements of heat and fluid flow characteristics. In this context, double feedback fluidic oscillators have shown promising jet flow control features and jet impingement cooling characteristics. Therefore, the current study has been devoted to analyzing and assessing the recent research progress in design improvements of double feedback fluid oscillators and the augmentation of thermal-hydraulic characteristics of impinging sweeping. Moreover, the variations in the heat transfer and hydraulic performance of impinging jets for different shapes of target surfaces have been comprehensively examined. In the end, research gaps for future work have been highlighted.

Comparative study on flow and heat transfer characteristics of swirling impingement jet issuing from different nozzles

The flow and heat transfer characteristics of spiral rod (SR), twisted tape (TT), guide vane (GV) and thread grooves (TG) nozzles are compared by numerically and experimentally for swirl angle (θ) = 15°-60° and Reynolds number (Re) = 6000–12000. An experimental system is built to investigate the heat transfer characteristics of the impingement target. The experimental results show that the TG nozzle has the highest Nusselt number (Nu) in the stagnation region, 19.19%−55.98% higher than that of the other three nozzles for Re = 6000, and SR nozzle has the highest Nu except in the central area. In addition, it is shown that the gas chamber pressure of TG nozzle is much smaller than that of the other three nozzles. The numerical method studies the streamlines, turbulent kinetic energy and vortex distribution in the jet space, and the Nu under different θ and Re of the four types of nozzles, which is verified with the experimental results. The numerical results show that SR nozzle has the largest impingement velocity, the best heat transfer effect, and uniformity, and is obviously influenced by θ. With the increase of the impingement spacing of the four types of nozzles, the impingement area enlarges and cooling effect weakens simultaneously. By studying the flow and heat transfer characteristics, a new swirl nozzle design method based on heat transfer, heat uniformity and pressure loss is established.

Numerical Simulation of Pulverized Coal Injection in the Dome Zone of a COREX Melter Gasifier

The dome zone is the freeboard at the top of the COREX melter gasifier (MG), and the secondary injection systems are installed in the dome zone to recycle dust and oxygen. Pulverized coal injection (PCI) in the dome zone of the COREX MG is used to transform the oxygen burners (OBs) into oxygen–coal burners (OCBs) and cooperates with the dust burners (DBs) to realize the function of gasification. In this work, a three-dimensional (3-D) steady-state mathematical model was developed to simulate the transport phenomenon in the dome zone with and without PCI. The results show that when 150 kg/t of pulverized coal is injected into the dome zone, the impinging stream area expands and the average temperature in the dome zone increases by about 40 K. The proportion of CO2 in the reduction gas decreases by 7.8 pct, while the proportion of H2 increases by 7.4 pct at the outlet of the MG with the PCI in the dome zone. The total effective volume fraction of reducing gas at the outlet of MG can reach 83.3 pct, which is a benefit to improving the reduction processes in the shaft furnace. Due to the intensification of circulation and the complexity of particle behavior, the residence time of particles increases by about 10 seconds in the case of PCI and the burnout rate of recycling dust and pulverized coal can reach above 99 pct.Graphical abstract