Abstract The experiments was studied on a rotating ribbed square duct from two different impingement position of air jets (termed as Type A and B) and at rotational speeds of 0,300 and 600 rpm¡CThe jet impinged on two different geometric types of rib (square and semi-circular ribs). The study covered jet Reynolds number 5000 to 9000 and the jet rotation number was varied from 0 to 0.0053. Results are presented and focused on the effect of two of circular jet arrangements and different geometric of ribs. Significant heat transfer enhancement was found for Type A configuration and square ribs within the ranges of operating parameters considered in the study. However, rotation induced Coriolis and centrifuged forces decreased the Nusselt number values (up to 20%) which is quitely conincided with those of previous studies.

Ulm, Univ., Diss., 2008.

Subacromial impingement syndrome is among the most frequent cases of shoulder pain and dysfunction in adults. It's reffered to as shoulder pain is third only to headache and back pain in freqency seen in the practitioner's office. It's known, SIS is a heterogenous entity, which can be caused by a lot of ethiological factors. These factors can have bad influence of architecture of the subacromial space. The tendons of the rotator cuff are passing trough this space and so that structures are most often affected by degenerative disorders. Clinical history and physical examination play a key role in diagnostics. Provocative manoeuvres (Neer's sign, Hawkin's test, Yocum manoeuvre) seem to be useful for identifying impingement syndrome. If there is a reasonable doubt in diagnostics we can use imaging methods. We should start with the minimally invasive and the most economic method. Commonly used course of action include x-ray, ultrasound and MRI. Well-timed and the most accurate diagnostics enable us to start suitable treatment. The treatment commonly starts with pain-relief drugs (NSAID, subacromial injection of mixture of corticosteroid and local anestethic). The combination of physiotherapy and manual therapy seems to be an effective treatment method. This therapeutic combination is good for improving function...

The effect of superhydrophobicity on liquid water impingement on a flat horizontal surface was explored. The surfaces combined a hydrophobic surface chemistry with a patterned microstucture in order to produce high contact angles with water. Three sets of experiments were performed, one for jet impingement and two for droplet impingement, which advance previous work in characterizing the interaction of water and superhydrophobic surfaces.Jet impingement experiments were performed to characterize a transitional regime between an unsubmerged and a completely submerged superhydrophobic surface by varying an imposed downstream depth. For low downstream depths, the surface remained unsubmerged and displayed only break up of the thin film, while at high downstream depths, the surface was completely submerged and only a hydraulic jump occurred. Within the transition, the surface was partially submerged and both thin film breakup and a hydraulic jump were observed. Experiments were performed for three Reynolds numbers, Re, ranging from 1.9 x 104 to 2.2 x 104 (based on the volume flow rate). For all Re, the transition was characterized by a reduction in the hydraulic jump radius as downstream depth increased. Also, as Re increased, the downstream depths over which the transition occurred was greater. When a droplet impinges on a surface covered with a liquid film, a thin liquid wall, or crown, forms and propagates outward. Here a comparison of this crown dynamic was made for smooth hydrophilic surfaces and superhydrophobic (SH) surfaces patterned with post or rib microfeatures. Due to the high contact angle of the SH surfaces, a relatively thick film (h ≈ 5 mm) of water was required to maintain a film. This resulted in negligible differences between the surfaces utilized. Droplet train impingement on the same post and rib SH surfaces was also investigated. When each individual droplet impinged on the surface, a crown formed which spread out radially until reaching a semi-stable or regularly oscillating breakup diameter. At this point, the water would either build up or breakup into droplets or filaments and then continue radially outward. In some cases the crown would break up, causing splashing. A comparison to previous experiments on hydrophilic surfaces shows a distinct difference in splashing at low frequency. The breakup diameter was measured over a Weber number range of 72-2800. The data was collapsed as a function of a combination of the Reynolds number (Re), Capillary number (Ca), and Strouhal number (St), resulting in Re0.7CaSt. The rib SH surface displayed an elongated breakup due to the anisotropic surface features. The breakup diameter for the droplet train was compared to the breakup diameter which has been shown to occur with a jet impinging on a SH surface.

Das Ziel der Arbeit war eine quantitative Analyse des Subakromial- und Subkorakoidalraums anhand von berechneten Minimaldistanzen an 3D-Schulter-Modellen in verschiedenen Abduktionspositionen sowie in klinisch relevanten Impingement-Test-Positionen. Von 14 Patienten mit einseitigem Impingement-Syndrom der Schulter und 14 schultergesunden Probanden wurden im offenen MRT-System Aufnahmen beider Schultern in 0°, 45°, 90° und 135° Abduktion und den Impingement-Positionen nach Neer und Hawkins angefertigt. An der kranken Schulter wurden sowohl prä- als auch postoperative Serien aufgenommen. Bei der MRT-Bilddatenbearbeitung erfolgte eine manuelle Segmentierung der MR-Bilddaten, die Bildung eines 3D-Oberflächenmodells der knöchernen Strukturen der Schulter und anschließend die Berechnung verschiedener Minimaldistanzen (akromiohumeral, klavikulohumeral, korakohumeral, korakotuberkulär). Die symptomatische Schulter der Patienten zeigte keine signifikant unterschiedliche Akromiohumeraldistanz unter Abduktion im Vergleich zur gesunden Seite. Gegenüber der schultergesunden Gruppe ergab sich eine signifikante Reduktion des akromiohumeralen Intervalls in 90° und 135°. Das subkorakoidale Intervall stellte sich an der Impingement-Schulter sowohl unter Abduktion als auch in den Impingement-Manövern signifikant kleiner als bei den Probanden dar. Die kranke Schulter war in Neer-Einstellung durch eine signifikant kleinere Akromiohumeraldistanz gegenüber der asymptomatischen Schulter sowie den Probanden charakterisiert. Die Hawkins-Position wies dagegen signifikant verminderte subkorakoidale Distanzen an der kranken Schulter auf. Die Akromiohumeraldistanz an der gesunden Schulter der Patienten war nur in 135°-Position signifikant kleiner im Vergleich zu den Probanden. Die korakotuberkuläre Strecke war ähnlich der kranken Schulter auch auf der asymptomatischen Patientenschulter in allen Abduktionspositionen signifikant kleiner als an der Probandenschulter. Postoperativ präsentierte sich der Akromiohumeralraum bei Abduktion bis 90° signifikant erweitert zum präoperativen Befund. Im Vergleich zur gesunden Schulter und den Probanden war die Erweiterung nur noch in 45° und 90° signifikant. Die Klavikulohumeraldistanz zeigte zwischen den einzelnen Gruppen kaum signifikante Unterschiede. Es lässt sich schlussfolgern, dass ein einseitiges Impingement-Syndrom der Schulter nicht mit einer signifikanten Reduktion der Akromiohumeraldistanz unter Abduktion im Vergleich zur gesunden Gegenseite einhergeht. Verglichen mit einem gesunden Normalkollektiv imponiert das Impingement-Syndrom mit einer signifikanten Reduktion der Akromiohumeraldistanz in den hohen Abduktionsgraden. Die arthroskopische subakromiale Dekompression als Therapieoption beim subakromialen Impingement-Syndrom erzeugt subakromiale Verhältnisse, die unter Abduktion bis 90° signifikant erweitert gegenüber dem präoperativen Bild und gesunden Schultern sind. Der klavikulohumerale Raum scheint nur geringen Einfluss auf die Pathogenese eines Impingement-Syndroms zu besitzen und sollte deshalb nicht als morphologischer Parameter in der Bilddiagnostik herangezogen werden. Es konnte außerdem herausgefunden werden, dass das morphologische Korrelat eines positiven Impingement-Tests nach Neer eine signifikant verminderte Akromiohumeraldistanz gegenüber gesunden Schultern darstellt. Ein positives Hawkins-Manöver geht mit einer signifikant reduzierten Korakohumeral- und Korakotuberkulärdistanz einher. Abschliessend kann festgestellt werden, dass mit der vorgestellten Methode eine Quantifizierung der Subakromialraumweite bei Probanden und bei Patienten mit subakromialem Impingement-Syndrom der Schulter in klinisch relevanten Gelenkpositionen durchgeführt werden kann. Auf Grund des erheblichen Zeitaufwandes der 3D-Bilddatenanalyse wird die Methode voraussichtlich ausschließlich wissenschaftlichen Fragestellungen vorbehalten bleiben.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.

Femoroacetabular impingement (FAI) is a hip joint deformity that causes joint pain, decreases joint range of motion and results in abnormal kinematic and kinetic characteristics. It is not known whether these biomechanical variations are caused by the actual mechanical impingement aspect of hip deformity or neuromuscular adaptations and soft tissue damage associated with pain. The purpose of this study was to investigate the effects of femoroacetabular cam deformity (FAD) during daily functional tasks. This was accomplished by measuring and comparing the hip joint biomechanics of symptomatic FAI (sFAI), asymptomatic FAD, and control (CON) subjects. Fifty one subjects volunteered to the study (n = 51; CON = 17, FAD = 18, sFAI = 16) and they performed 6 simulated activities of daily living: stair ascent and descent, sit-to-stand and stand-to-sit, dynamic range of motion, maximum depth squats and level walking tasks while motion ground reaction force and muscle activity were recorded. However, only the squat and level walking tasks were analyzed for this thesis. For each task, three-dimensional kinematics and kinetics were recorded and analyzed. Qualitative questionnaires (HOOS and WOMAC) and physical exams were also part of the testing protocol, and maximum voluntary isometric contractions (MVIC) were collected as part of a separate EMG protocol. The EMG results were not analyzed but the MVIC results were and the moments of force were determined. The sFAI group had significantly reduced scores for all HOOS and WOMAC metrics compared to FAD and CON. The sFAI group had significantly reduced external rotation, internal rotation, and a trend indicating reduced hip flexion compared to FAD and CON groups. The FAD group had a trend indicating reduced internal rotation compared to CON. There were no differences in the moments of force between groups for the MVICs. No statistically significant differences were observed between groups for the squat trials, however, the sFAI group showed biomechanical variations. Both the CON and FAD groups were able to squat deeper, had greater pelvic range of motion and a larger maximum hip and knee flexion angle compared to sFAI. Similarly, the walking tasks did not elucidate any between group differences in biomechanical characteristics. Yet, there was a noticeable trend of decreased peak hip abduction angle in the sFAI group compared to CON. This result may be indicative of a gait adaptation based on the pain that sFAI subjects endure over a long period of time. Interestingly, the FAD group did not have obvious gait patterns similar to either the CON or sFAI, making it unclear if the asymptomatic cam deformity has any gait adaptation effects. Since no differences were observed between FAD and CON in squatting and walking, the actual bone deformity may not be the cause of restricted motion during daily activities as previously thought. Internal rotation physical examination appears to indicate potential restrictions in the FAD compared to CON, and may be the best parameter to assess differences between groups and predict the presence of cam deformity. It is suggested that the presence of pain, caused by soft tissue damage over time, may be confounding factors leading to the biomechanical and neuromuscular discrepancies observed in sFAI, and should be the next avenue of study.

No description available.

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Despite this, no known study has used motion analysis and ground reaction forces to quantify the outcome of surgery for FAI. The goal of this study was to compare the preoperative and postoperative lower-extremity joint kinematic and kinetic measurements of cam FAI patients during activities of daily living with use of a high-speed motion capture system and force platforms. We hypothesized that the lower-extremity joint mechanics of FAI patients during level walking and maximal squatting would resemble more those of healthy control subjects, after surgery. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, performed walking and maximal depth squatting trials preoperatively and postoperatively. Thirteen healthy control subjects, matched for age, sex and body mass index, provided normative data. Results showed that postoperatively, FAI patients had reduced hip ROM in the frontal and sagittal planes, produced smaller peak hip abduction and external rotation moments, and generated less peak hip power compared to the control group during level walking. During maximal squatting, postoperative FAI patients squatted to a greater depth, and had larger knee flexion and ankle dorsiflexion angles, as well as the sum of all joint angles of the affected limb at maximal depth compared to the preoperative values. The lower-extremity joint and pelvic mechanics of FAI patients did not fully return to normal after surgery. Although surgery seemed to reduce hip pain and restore a normal femoral head-neck offset, it further impaired muscle function as a result of muscle incisions. More research is needed to determine the effects of muscle incisions, which could help improve surgical techniques and develop better rehabilitation programs for FAI patients.

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Despite this, no known study has used motion analysis and ground reaction forces to quantify the outcome of surgery for FAI. The goal of this study was to compare the preoperative and postoperative lower-extremity joint kinematic and kinetic measurements of cam FAI patients during activities of daily living with use of a high-speed motion capture system and force platforms. We hypothesized that the lower-extremity joint mechanics of FAI patients during level walking and maximal squatting would resemble more those of healthy control subjects, after surgery. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, performed walking and maximal depth squatting trials preoperatively and postoperatively. Thirteen healthy control subjects, matched for age, sex and body mass index, provided normative data. Results showed that postoperatively, FAI patients had reduced hip ROM in the frontal and sagittal planes, produced smaller peak hip abduction and external rotation moments, and generated less peak hip power compared to the control group during level walking. During maximal squatting, postoperative FAI patients squatted to a greater depth, and had larger knee flexion and ankle dorsiflexion angles, as well as the sum of all joint angles of the affected limb at maximal depth compared to the preoperative values. The lower-extremity joint and pelvic mechanics of FAI patients did not fully return to normal after surgery. Although surgery seemed to reduce hip pain and restore a normal femoral head-neck offset, it further impaired muscle function as a result of muscle incisions. More research is needed to determine the effects of muscle incisions, which could help improve surgical techniques and develop better rehabilitation programs for FAI patients.