Internal Impingement Research Articles

Relationship Between Pain, Muscle Strength, Function, and Quality of Life in Overhead Players With Chronic Internal Shoulder Impingement

Background and Objectives: This study aims to determine the relationship between pain, muscle strength, function, and quality of life (QoL) in overhead players with chronic shoulder internal impingement syndrome. Methods: Forty-seven overhead players consisting of 15 men, 32 and women (mean age 32.45±7.2) with chronic shoulder internal impingement were enrolled. The pain was measured by a visual analogue scale (VAS). Disabilities of the arm, shoulder, and hand (DASH) and shoulder pain and disability index (SPADI) questionnaires were used to measure pain and function, and a short form (SF)-36 questionnaire to measure QoL. Muscle strengths were evaluated in both hands with a hand-held dynamometer and players were asked to hold the maximal voluntary isometric contraction (MVIC) in the middle range for 3 s and rest for 30 s between each test and each contraction was repeated three times on both affected and healthy side and the average of contractions was considered for each side. Results: The study showed a significant relationship between pain, the strength of shoulder muscle groups (-0.354), function (-0.935), and QoL (-0.861) in overhead throwers with chronic shoulder internal impingement syndrome and the strength of internal rotators of the affected shoulder decreased more than others. (P<0.05) Conclusions: This correlational study showed a significant relationship between pain and strength of shoulder muscles and function and QoL in overhead throwers with this syndrome.

Conjugate Heat Transfer Validation of an Optimized Film Cooling Configuration for a Turbine Vane Endwall

Abstract In this study, to improve overall cooling performance for a turbine endwall that incorporated internal jet impingement and external purge flow and discrete injection cooling, the external film cooling was re-designed based on the knowledge of film coverage patterns from a baseline design. Experimental conjugate heat transfer validation of the newly-designed cooling geometry was conducted by measuring overall cooling effectiveness over the endwall through an Infrared thermography technique and detecting aero-thermal fields at the cascade exit with five-hole and thermocouple probes. For a given total coolant flow rate, the influence of coolant split among different cooling sources was examined. Parallel computational simulations were undertaken to elaborate the experimentally-observed results by offering in-passage flow physics. Comparisons with the baseline design proved that the newly-designed cooling scheme improved the endwall overall cooling performance in terms of both effectiveness levels and coverage area. In addition to optimizing the cooling geometry, more efficient usage of the coolant was found to be linked with the proper coolant split, which helped the re-designed cooling geometry to achieve an improvement of cooling effectiveness by approximately 20%. The computational simulations produced satisfactory overall cooling effectiveness, but failed to capture mixing of coolant with mainstream flow. The flow interactions visualized by the simulations provided evidence that the coolant jets from the optimized cooling scheme increased mixing flow loss but those from the pressure side suppressed the inherent vortex flow, resulting in no aerodynamic penalty as compared with the baseline cooling design.

Prevalence of Abnormal Findings in the Posterosuperior Humeral Head of Asymptomatic Collegiate Baseball Pitchers Using Ultrasonography

BackgroundThe posterosuperior humeral head contacts the glenoid during pitching. While magnetic resonance imaging (MRI) often detects abnormalities in the posterosuperior humeral head of baseball pitchers, ultrasonography may also be effective in identifying these abnormalities. However, studies on such abnormalities in asymptomatic players are limited. Thus, this study aimed to determine the prevalence of abnormal findings in the humeral head using ultrasonography in asymptomatic collegiate baseball pitchers. MethodsWe utilized ultrasonography to assess abnormal findings in the humeral head, defined as a break in continuity or an irregular surface around the infraspinatus insertion, in 33 college baseball pitchers (pitcher group) and 30 college students without experience in overhead sports (control group). For 11 of the 33 pitchers, computed tomography (CT)-like images were used to locate the abnormalities. The location was quantitatively identified in the axial plane using a clock system, with the bicipital groove designated as 12 o’clock, and qualitatively assessed in the sagittal plane. Shoulder internal and external rotation ranges of motion (IR and ER ROMs) and humeral retroversion were measured using an inclinometer. The prevalence of abnormalities among the four subgroups (throwing and non-throwing shoulders of the pitcher group and dominant and non-dominant shoulders of the control group) was compared using the Fisher’s exact test. A paired t-test was also performed to compare the IR and ER ROMs, as well as the humeral retroversion between each group’s throwing (dominant) and non-throwing (non-dominant) sides. ResultsThe prevalence of abnormalities was significantly higher (76%) in the throwing shoulder of the pitcher group than in the other shoulder groups (< .001). The mean position of the humeral head abnormalities in the axial plane was 8:32 ± 0:21 in the clock system, with all abnormalities located at the infraspinatus insertion on the greater tuberosity in the sagittal plane according to CT-like image analysis. While ER ROM and humeral retroversion were greater in the throwing shoulder, IR ROM was less than that in the non-throwing shoulder in the pitcher group (< .001). ConclusionUltrasonographic assessments revealed a higher prevalence of abnormalities in humeral head for asymptomatic collegiate baseball pitchers. Repetitive throwing motions may lead not only to adaptations in the ROM of the shoulder joint but also to abnormalities in the humeral head. Thus, ultrasonography may help identify asymptomatic baseball players with physiological internal impingement.

Relationship between glenohumeral horizontal abduction angle and scapular internal rotation angle at maximum shoulder external rotation during baseball pitching

BackgroundIncreased scapulothoracic (ST) internal rotation at maximum external rotation (MER) during baseball pitching can decrease glenohumeral (GH) horizontal adduction, leading to excessive GH horizontal abduction. However, few studies have examined this direct relationship, and none have investigated the ST internal rotation angle at stride foot contact (FC) and MER. This study investigated the relationships between GH horizontal adduction and ST internal rotation angles at MER and between ST internal rotation angles at FC and MER. MethodsWe recruited 15 asymptomatic collegiate baseball pitchers and assessed the ST internal rotation angle at FC and MER and GH horizontal adduction angle at MER during pitching using an optical motion tracking system. Pearson’s correlation coefficients determined the relationships between GH horizontal adduction and ST internal rotation angles at MER and between ST internal rotation angles at FC and MER. ResultsThe GH horizontal adduction angle at MER was significantly related to the ST internal rotation angle at MER (r = -0.58, p = 0.022). The ST internal rotation angle at FC was significantly related to the ST internal rotation angle at MER (r = 0.53, p = 0.045). ConclusionsThe GH horizontal adduction angle at MER is associated with the ST internal rotation angle at MER in asymptomatic collegiate baseball pitchers and the ST internal rotation angle at FC is related to the ST internal rotation angle at MER. Thus, the scapula and humerus should be controlled from FC to MER during pitching to reduce internal impingement risk in asymptomatic baseball pitchers.

Effect of different internal impingement structures and cratered film cooling holes on overall cooling effectiveness

Effect of different internal impingement structures and cratered film cooling holes on overall cooling effectiveness

Effects of film hole spanwise angle and diameter on flow and heat transfer of impingement/effusion cooling with crossflow diverters

This paper studies the blade cooling under the co-effect of external film extraction and internal impingement cooling with crossflow diverters. The influence of spanwise angle (α) and diameter (Df) of film hole on flow and cooling performance are analyzed when the impingement jet Reynolds number ranges (Rei) from 15,000 to 45,000. From the results, if a row of film holes is set on the target surface of an impingement cooling with crossflow diverters, the overall cooling effectiveness will be greatly improved, especially the pressure side. When the α ranges from 35° to 115°, no matter pressure side or suction side, the film jet injection towards blade hub is more beneficial to cooling, and the smaller the α, the more beneficial. When the Df ranges from 0.25 mm to 1.00 mm, at suction side, as Df increases, overall cooling effectiveness gradually increases; at pressure side, when the Df ranges from 0.25 mm to 0.75 mm, overall cooling effectiveness increases, but if the Df continues to increase, it will decrease, which means the Df of 0.75 mm can obtain the most excellent cooling performance. This study provides a theoretical basis for the comprehensive application of film extraction, impingement cooling, and crossflow diverters in blade cooling design.

Effects of Scapular Angular Deviations on Potential for Rotator Cuff Tendon Mechanical Compression.

One proposed mechanism of rotator cuff disease is scapular motion impairments contributing to rotator cuff compression and subsequent degeneration. To model the effects of scapular angular deviations on rotator cuff tendon proximity for subacromial and internal mechanical impingement risk during scapular plane abduction. Descriptive laboratory study. Three-dimensional bone models were reconstructed from computed tomography scans obtained from 10 asymptomatic subjects and 9 symptomatic subjects with a clinical presentation of impingement syndrome. Models were rotated to average scapular orientations from a healthy dataset at higher (120°) and lower (subject-specific) humeral elevation angles to investigate internal and subacromial impingement risks, respectively. Incremental deviations in scapular upward/downward rotation, internal/external rotation, and anterior/posterior tilt were imposed on the models to simulate scapular movement impairments. The minimum distance between the rotator cuff insertions and potential impinging structures (eg, glenoid, acromion) was calculated. Two-way mixed-model analyses of variance assessed for effects of scapular deviation and group. At 120° of humerothoracic elevation, minimum distances from the supraspinatus and infraspinatus insertions to the glenoid increased with ≥5° changes in upward rotation (1.6-9.8 mm, P < .001) or external rotation (0.9-5.0 mm, P≤ .048), or with ≥10° changes in anterior tilt (1.1-3.2 mm, P < .001). At lower angles, ≥20° changes in most scapular orientations significantly increased the distance between the supraspinatus and infraspinatus insertions and the acromion or coracoacromial ligament. A reduction in scapular upward rotation decreases the distance between the rotator cuff tendon insertions and glenoid at 120° humerothoracic elevation. Interpretation is complicated for lower angles because the humeral elevation angle was defined by the minimum distance. These results may assist clinical decision making regarding the effects of scapular movement deviations in patients with rotator cuff pathology and scapular dyskinesia and may help inform the selection of clinical interventions.

Spectrum and patterns of shoulder pathology on MRI in symptomatic elite wheelchair basketball athletes.

Wheelchair basketball (WCB) is a popular para-sport adapted for athletes with physical disabilities. Shoulder injuries are commonly reported among WCB athletes. However, the understanding of the specific patterns and characteristics of shoulder injuries in WCB players is currently limited, and there is a lack of comprehensive literature available on this subject. To investigate the spectrum of pathologies observed in elite wheelchair basketball (WCB) athletes referred for MRI evaluation of symptomatic injuries of the shoulder. Retrospective review of consecutive elite WCB athletes referred for MRI evaluation of symptomatic shoulder injury. Demographic, clinical, and functional data including international wheelchair basketball federation (IWBF) classification of each athlete were collected. A total of 28 MRI studies were reviewed. Excluding MRI examinations of the same shoulder, 18 study cases were assessed for pathology of the rotator cuff (RC), labrum, long-head of biceps tendon, glenohumeral and acromioclavicular joints, and osseous lesions of the humerus or glenoid. Correlations between clinical-demographic features and MRI findings were statistically evaluated. Supraspinatus tears were observed in 72.2%, infraspinatus tears in 50%, and subscapularis tears in 38.9% shoulders. Articular-sided partial tears frequently involved posterior supraspinatus (88.9%) and anterior infraspinatus (100%). Labral tears were seen in 38.9%, with involvement of the posterosuperior labrum in all tears. Hill-Sachs and osseous Bankart lesions (5.6%), and anterior-inferior labral tears (11.1%), were uncommon findings. Statistically significant correlations were observed of low IWBF point class and non-ambulatory athletes with subscapularis tendinosis (p = 0.015, p = 0.001) and tearing (p = 0.050, p = 0.013), and athletes with limited trunk control with subscapularis tendinosis (p = 0.013). RC tears are common in elite WCB athletes with pattern of RC and labral tearing suggesting internal (superior-posterior) impingement as a contributory pathoetiologic mechanism. Non-ambulatory, low IWBF point class athletes, as well as those with limited trunk control have a statistically significant increase in subscapularis tendon pathology on MRI.

Internal impingement of the shoulder in sports activity: common overuse injury

Internal impingement of the shoulder in sports activity: common overuse injury

Experimental investigations on flow characteristics of impingement/swirl cooling structures inside a blade leading edge

Experimental investigations were conducted to study the flow characteristics of impingement/swirl cooling structures inside a turbine-blade leading edge (LE) using particle image velocimetry. The Reynolds number (Re) was maintained at either 10 000 or 20 000. The effects of Re and the ratio of the impingement-cooling (IC) hole offset distance to the IC hole diameter (e/d) on the flow phenomena and the characteristics of the impingement/swirl cooling structures inside the blade LE were analyzed. The effects of the coolant-outflow mode were also taken into consideration. The results show that when e/d = 0, the diffusion flow of the impingement jet moves more to the side of the LE with a larger rounded corner, and this phenomenon is particularly obvious at Re = 20 000. Regardless of the e/d value, both the impingement-jet velocity and vorticity increase significantly at a higher Re value. The velocity of the impingement jet reaching the internal impingement target surface of the LE decreases significantly as e/d is changed from 1.5 to −1.5 with Re = 20 000. Generally speaking, regardless of the e/d value, the impingement jet can form a swirling vortex on the side with the larger rounded corner. Under the conditions of Re = 20 000 and e/d = 1.5, regardless of the coolant-outflow mode, the flow velocity of the impingement jet decreases monotonically along the flow direction, and this is more obvious inside the LE model without film-cooling holes.

Numerical analysis and experimental validation of the jet impingement cooling of a turbine-blade leading edge at different rotation speeds

A detailed experimental and numerical validation studies are conducted on internal channel jet impingement cooling where seven jets impinging inside a rotating semi-cylindrical channel. The study objective is to mimic the cooling flow structure in gas turbine leading edge by using the rotating the semi-circular channel. These studies are conducted by considering a jet Reynolds number of 7500 at five different rotation speeds (ranging from 0 to 200 rpm). Numerical analysis is performed using the shear stress transport (SST) k−ω turbulence model with a properly analyzed fine mesh containing around eight million nodes. A test setup with required instrumentation is developed inhouse for this study. Two temperature measurement techniques, namely thermochromic liquid crystals (TLCs) and thermocouples, are adopted. Further, the target surface temperature contours are precisely analyzed by comparing the TLC temperature measurements with the numerical temperature results. The captured temperature contours indicated points of minimum-temperature regions, which corresponded to the jet impingement regions. By examining the temperature distribution along the axial centerline, a good agreement has been established between the numerical results and the experimental measurements. For a jet Reynolds number of 7500, increasing channel rotation speed from 0 to 250 rpm has reduced the variation in temperature between different jets. The size of inlet port used to guide flow to the feeding duct has a strong impact on jet formation and flow structure, and it has led to different mass flow rate across jets. Furthermore, a small deviation between numerical and experimental data can be observed near the end side of the channel owing to the radial and lateral heat transfer losses and outlet flow restriction.

Is Workload Associated With Internal Impingement in Professional Baseball Pitchers? An Analysis of Days of Rest, Innings Pitched, and Batters Faced.

Internal impingement is a common cause of shoulder pain and dysfunction in baseball pitchers. The purpose of this study was to determine if the amount of rest days between outings, the number of innings pitched in each outing, and the number of batters faced in each outing are risk factors for internal impingement in professional baseball pitchers. It was hypothesized that a higher workload would significantly increase a pitcher's risk of developing internal impingement. Case-control study; Level of evidence, 3. All professional (Major and Minor League) baseball pitchers who were diagnosed with internal impingement between 2011 and 2017 were identified using the Major League Baseball's Health and Injury Tracking System. A separate player usage data set was used to determine workload. The authors compared workload variables (days of rest, innings pitched, and batters faced per game) between each of 4 injury-exposure groups (pitchers with documented internal impingement <2, <6, <12, and >12 weeks after a game) and a control group of pitchers with no internal impingement using Student t tests or Mann-Whitney U tests. In a within-pitcher paired analysis of the injury groups, the workload variables during 3 acute periods (<2, <6, and <12 weeks preinjury) were compared with the baseline values (>12 weeks preinjury). Overall, there were 624 professional baseball pitchers diagnosed with internal impingement during the study period. Compared with pitcher games (n = 213,964), pitchers in all 4 injury-exposure groups had significantly more innings pitched per game (P ≤ .003 for all) and faced significantly more batters per game (P < .001 for all). There were significantly more starting pitchers in each of the injury-exposure groups when compared with the controls (P < .001 for all). However, when comparing acute and baseline workloads in the pitchers diagnosed with internal impingement, there were no significant differences in the number of innings pitched, batters faced, or days of rest. This analysis revealed significantly greater pitcher workload and percentage of starting pitchers in professional baseball players diagnosed with internal impingement when compared with healthy controls. However, this injury did not seem to be associated with an acute increase in workload.

Experimental and numerical investigation of thermo-hydraulic behavior in a rotating wedge-shaped trailing edge channel with internal jet impingement

Cooling the trailing edge of turbine blade presents a significant challenge due to its slender and aerodynamic shape. This paper carries out an experimental and numerical investigation of the thermo-hydraulic behavior within a wedge-shaped trailing edge cooling channel under both stationary and rotating conditions. The studied model incorporates rib-roughened supply channel, internal jet impingement and slots. The examined inlet Reynolds number, rotation number, and temperature ratio were varied within the ranges of 10,000 to 61,000, 0 to 0.16, and 0.08 to 0.16, respectively. Under stationary condition, changing the target surface from trailing to leading surface improves thermal performance within the impingement channel by 15–30%. After rotation is introduced, a portion of fluid is directed towards the low-radius region, resulting in a 10% increase in the heat transfer coefficient at low-radius region, while heat transfer in the high-radius region is diminished. Increasing temperature ratio reduces the effect of rotation, though its influence remains secondary. Moreover, the friction factor and performance evaluation coefficient of two structures with opposite impingement target surfaces were also investigated.

Lateral Decubitus Positioning For Shoulder Arthroscopy

Background: Lateral decubitus positioning is a frequently employed technique to perform shoulder arthroscopy. Proper patient positioning and equipment setup is crucial to ensure a safe and efficient surgery. Indications: The common indications for performing a shoulder arthroscopy in the lateral decubitus position include anterior shoulder stabilization, posterior shoulder stabilization, superior labrum anterior to posterior (SLAP) repair, diagnostic arthroscopy for internal impingement, and arthroscopic capsular release for adhesive capsulitis. Technique Description: After undergoing general endotracheal anesthesia in the supine position on a standard operating room table, the patient is rotated into the lateral decubitus position with the operative arm facing upward. The patient’s head is supported with a pillow to ensure a neutral position. The nonoperative arm is flexed forward and rests on a padded arm board. The sides of a bean bag are applied to the patient’s torso to maintain the lateral decubitus position, and the bean bag is deflated to remain rigid. An axillary roll is placed under the axilla, and foam pads are placed below the “down leg” and between both legs. A commercial arm jack is positioned on the anterior, proximal side of the operating room table to allow for 20° of shoulder abduction, which maximizes the glenohumeral joint space. Results: Advantages of the lateral decubitus position over the beach chair position include improved access to the anterior, inferior, and posterior glenoid; more ergonomic positioning for the operating surgeon; lower risk for patient cerebral hypoperfusion; and reduced rates of recurrent instability following arthroscopic stabilization in comparison to procedures performed in the beach chair position. Disadvantages of the lateral decubitus position include risk of traction-related neurovascular injury, requirement of an arm suspension device, and increased difficulty in rotating the shoulder intraoperatively. Discussion/Conclusion: Lateral decubitus positioning is commonly used to achieve a circumferential view of the glenohumeral joint in shoulder arthroscopy. This surgical position yields several advantages for the operating surgeon and has been shown to be associated with improved clinical outcomes after shoulder instability surgery. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Comparison of rotator cuff to glenoid proximity based on scapulothoracic upward rotation classification

BackgroundRecent evidence suggests that internal impingement, or rotator cuff tendon deformation against the glenoid, occurs during overhead motions and may therefore be a mechanism of pathology even in non-athletes. Clinically, knowing how movement impacts potential injury mechanisms would be useful to guide movement-based treatment strategies. ObjectiveTo compare the distance between the glenoid and rotator cuff footprint between two groups classified based on scapulothoracic upward rotation (UR) magnitude (i.e., low, high) at 90° humerothoracic elevation. MethodsShoulder kinematics were quantified during scapular plane abduction in 60 participants using single-plane fluoroscopy. Of these, 40 were subsequently classified as having high or low scapulothoracic UR based on the sample's distribution. The minimum distance between the glenoid and rotator cuff footprint was calculated along with the locations of closest proximity (i.e., proximity centers). Minimum distances and proximity center locations were compared between groups using 2-factor mixed-model ANOVAs. The prevalence of glenoid-to-footprint contact was also compared. ResultsGlenoid-to-footprint distances consistently decreased as humerothoracic elevation angle increased, and the anterior aspect of the footprint was closest to the posterosuperior glenoid. Minimum distances were not significantly different between UR groups (p≥0.16). However, group differences existed in proximity center locations (p<0.01). Glenoid-to-footprint contact was identified in 75.0% of participants at an average (SD) of 133.6° (3.2°) humerothoracic elevation. ConclusionThe results of this study suggest that decreased UR as classified and assessed in this study does not significantly impact glenoid-to-footprint distances but does alter the location of the contact, which occurred in most participants.

Proximal to distal sequencing impacts on maximum shoulder joint angles and the risk of impingement in baseball pitching involving a scapular independent thoracohumeral model.

Hyperangulation of the scapulohumeral joint due to poor coordination of the scapula during throwing motion is claimed to be a major cause of internal impingement in baseball pitchers. However, evidence of injurious scapular kinematics is lacking, particularly regarding how hyperangularion actually occurs in full-effort pitching. The purpose of this study was to describe sequential scapular motions involved in attaining maximum joint angles during pitching and the implications for internal impingement in elite baseball pitchers. An electromagnetic goniometer system computed kinematics for pelvis, thorax, scapulae, arms, and forearms during baseball pitching in 72 pitchers. Internal impingement risk was assessed based on kinematic characteristics of internal impingement quantified in a cadaveric study. The pelvis, thorax, and scapula rotated in the proximal-to-distal sequence. Large forearm layback observed near the end of the cocking phase (182 ± 27°) was achieved with a submaximal scapulohumeral external rotation (98 ± 14°). In the next 0.027 ± 0.007 s, forward thoracic rotation and then scapular rotation caused increased scapulohumeral external rotation to a maximum of 113 ± 14°. Here, humeral horizontal adduction and scapula protraction occurred simultaneously preventing the humerus from lagging further behind the scapula. Only one participant reached critical hyperangulation beyond which internal impingement was reported to occur. Most elite pitchers safely attained the fully cocked position, yet off-timed recoiling of scapular protraction caused hyperangulation in full-effort pitching. Therefore, proximal-distal sequencing between the scapula and humerus should be evaluated to lessen the risk of internal impingement in baseball pitchers.

Arthroscopic findings of the glenohumeral joint in symptomatic anterior instabilities: comparison between overhead throwing disorders and traumatic shoulder dislocation.

The term shoulder instability refers to a variety of mechanisms and clinical presentations. One of the common pathologies of throwing disorders is internal impingement with anterior instability. Most throwing athletes with symptomatic internal impingement with anterior instability exhibit positive apprehension and relocation test results, whereas those with recurrent anterior shoulder instability display positive apprehension test results. While the glenoid labrum-inferior glenohumeral ligament complex is a significant critical stabilizer for the prevention of anterior shoulder dislocation, the characteristics of the essential lesion in internal impingement with anterior instability have not been determined yet. This study aimed to compare the intra-articular lesion of athletes with internal impingement related to the overhead throwing motion in athletes with a traumatic shoulder dislocation. Sixty-one athletes (all men; mean age, 25.2±12.6yr) who underwent an arthroscopic procedure were divided into 2 groups: 25 in the throwing group and 36 in the dislocation group. All shoulders had subtle glenohumeral instability defined by a positive anterior apprehension test and a relocation test. Those with voluntary and multidirectional instability and large glenoid bone loss (more than 25%) were excluded from the current study. All shoulders were evaluated for the following evidence: rotator cuff injury, superior labrum tear anterior and posterior lesions, labral pathologies including Bankart lesions, osteochondral lesions to the humeral head, biceps tendon fraying or rupture, and inferior glenohumeral ligament and middle glenohumeral ligament (MGHL) conditions. Arthroscopic findings of the throwing group showed more supraspinatus injuries (92% and 25%, P<.001), type II superior labrum tear anterior and posterior lesions (60% and 3%, P<.001), posterosuperior labral lesions (92% and 39%, P<.001), and hypoplastic MGHLs (56% and 6%, P<.001) and lesser Bankart lesions (8% and 92%, P<.05) than those of the dislocation group. These results indicate that the characteristic lesions of internal impingement with anterior instability in throwing athletes include partial thickness rotator cuff tears, superior labrum tear anterior and posterior lesions, posterosuperior labral tears, and hypoplastic MGHLs. As expected, the physiopathology of internal impingement with anterior instability in throwing athletes may be related to the dysfunction of the anterosuperior glenohumeral capsular ligament, including the MGHL, rather than the inferior glenohumeral ligament as in traumatic anterior shoulder dislocations. These findings would be useful for defining treatment strategies for internal impingement with anterior instability in overhead throwing athletes.

Experimental and numerical studies on enhanced effusion cooling with shallowly dimpled film holes on double-wall structure surface

This paper presents a flow and heat transfer investigation on multi-row dimpled film cooling in the double-wall configuration, considering important flow and geometrical characteristics including internal narrow jet impingement channel and outer film cooling with shallowly dimpled holes. The film cooling hole has dimpled exit, with the dimple depth to diameter ratio of 0.2. The inclined angle of the film hole is 30 degree and film hole length to diameter ratio is 3.0. The adiabatic film cooling effectiveness and heat transfer characteristics on the external surface are obtained by using transient infrared thermography measurement technique, which is based on the Impulse Response Method. And steady-state numerical computations using the Shear Stress Transport (SST) k-ω turbulence model were carried out respectively with the experimentally related adiabatic wall boundary conditions and with the fluid–solid conjugated boundary conditions, which provides the turbulent flow structure and overall cooling performance of the double-wall structure. The experimental results indicate that compared to the counterpart cylindrical film holes, the dimpled film holes can expand the spanwise coverage of coolant film, and the adiabatic film cooling effectiveness was improved by 66 %, 82 % and 180 % respectively at BR = 0.3, 0.6 and 1.0. Therefore, the dimpled holes can improve the film cooling effectiveness significantly. The numerical simulations indicated that the dimpled film holes influence the jet-in-crossflow structure and film cooling effectiveness significantly through complex interactions of the coolant jets, mainstream flow and dimpled wall. The overall cooling effectiveness of the double-wall structure with dimpled film holes on the thermal barrier coating can be distinctively improved by about 12.8 % over the case with conventional cylindrical film holes, which was indicated in the conjugated simulations under the blowing ratio of 1.0 and the mainstream-coolant temperature ratio of 2.0.

Experimental decoupled-analysis of overall cooling effectiveness for a turbine endwall with internal and external cooling configurations

High-efficient composite cooling structures that are comprised of external and internal cooling techniques, are one of the key technologies to guarantee the aerothermal performance and reliability of a turbine vane, especially the endwall region due to unique complex flow structures. It is thereby critical to understand the flow mechanism and conjugate heat transfer characteristics in this region for further optimal design. In this paper, a representative endwall model which matches non-dimensional parameters to real turbine operating conditions is investigated. Thermal protection for the endwall is provided by internal jet impingement and external purge flow and discrete hole injection cooling. Comprehensive measurements of overall cooling effectiveness over the endwall, total pressure loss coefficient, and non-dimensional temperature at the cascade exit are performed by using an infrared (IR) thermography technique, a five-hole probe, and a temperature probe. Through decoupled analysis, heat transfer and flow characteristics of film cooling only, both jet impingement and film cooling, upstream purge cooling only, and combined cooling are analyzed, respectively, and their optimal ranges of cooling air are obtained. The measurements reveal that with film cooling only, only the regions around the film holes are covered. Using both film and jet impingement cooling, cooling coverage is expanded, and cooling effectiveness is much higher with a more uniform distribution pattern. Purge flow achieves thermal protection for upstream regions of endwalls, and the combined cooling scheme that involves all cooling sources provides the best cooling performance. Globally, those cooling schemes have no obvious effects on overall cascade aerodynamic performance but affect the development and distribution of secondary flows.

Simulation on the effect of impinging distance for the aerodynamic and heat transfer characteristics of sweeping jet and film composite cooling

The influence of different impinging distances for sweeping jet cooling is investigated by employing the conjugate heat transfer method in a blade leading edge model with film holes. Three impinging distances (P/D = 3, 4, 5) are discussed and compared with the blowing ratio varying from 1.05 to 4.11. In addition, the SST k-ω turbulence model is validated by comparing the sweeping frequency and spanwise-averaged Nusselt number. Results indicate that the three impinging distance schemes obtain similar flow structures under identical blowing ratios. The total pressure loss coefficient is insensitive to the impinging distance and increases with the increasing blowing ratio. The Nusselt number and overall cooling effectiveness (OCE) are enhanced in response to the increased blowing ratio for all cooling schemes. A smaller impinging distance obtains a more considerable internal impingement cooling effectiveness, but the overall cooling effectiveness under each impinging distance is basically the same. Therefore, the results show that the sweeping jet and film composite cooling (SJF) can be applied to actual blades without considering the impinging distance.