A parametric analysis and optimization of double-jet film-cooling holes was performed using three-dimensional Reynolds averaged Navier-Stokes equations with the shear stress transport turbulence model. The numerical results for film-cooling effectiveness were validated in comparison with experimental data. The lateral and streamwise distances between the centers of the holes, along with two lateral ejection angles, were chosen as the design variables. The effects of these four variables on the film-cooling effectiveness were evaluated. For optimization of double-jet filmcooling holes, film-cooling effectiveness was considered as the objective function. Latin hypercube sampling was used to determine the design points. A weighted average surrogate model was constructed using the objective function values calculated at the design points. Sequential quadratic programming was used to search for the optimal point from the constructed surrogate. The cooling performance of double-jet film-cooling holes was improved considerably by optimization in comparison with the reference geometry.
A giant cell tumor (GCT) of the bone is characteristically found in skeletally mature patients. The tumor is rare in pediatric patients, and incidence reported in literature varies from 1.8% to 10.6%. We performed a retrospective study addressing symptoms, treatment, and outcome in pediatric patients who were diagnosed with GCT between March 1997 and January 2015 at our hospital. Fourteen (11.1%) of 126 surgically treated patients with histologically proven GCT were <19 years of age. We confirmed skeletal maturity using magnetic resonance imaging (MRI). Fourteen patients from 8 to 19 years old were identified. Sixteen lesions (76.2%) were found in long bones and 5 lesions (23.8%) in short bones. The most common site was around the knee in 8 patients (38%). GCTs mostly occur at the epi-metaphysis in 11 patients (52.3%). Regardless of the openness of epiphyseal plate, we observed GCT of bone in the epiphysis. Further study will be needed to prove the association between the presence of epiphyseal plate and location of tumor. Three patients (21.4%) had multicentric lesions, and four patients (28.5%) had local recurrence. Multicentric giant cell tumor and local recurrence occur more often in pediatric patients. The characteristics of GCT in pediatric patients do not differ from what is reported for GCT in adults.
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