A Numerical Study on Fluid Flow and Acoustic Characteristics of a Supersonic Impinging Jet Using Vorticity Confinement

The objective of this work is to numerically study the fluid flow and acoustic field of a supersonic impinging jet by applying the vorticity confinement (VC) method. For this aim, the three-dimensional compressible Navier-Stokes equations with the incorporation of the VC method are considered and the resulting system of equations is solved by using the sixth-order compact finite-difference scheme. To eliminate the numerical instability, a low-pass high-order filter is used. The nonreflective boundary conditions are applied for all the free boundaries and the radiated sound field is obtained by the Kirchhoff surface integration. Comparisons of the present results with the experimental data and other numerical simulations show that the solution methodology adopted based on the application of the VC method with the high-order compact finite-difference scheme provides a good prediction of the fluid flow and the acoustic field of the impingement region on coarser grids than that usually required in the LESs, and thus, the calculations of coarse grid LESs are improved.

Prediction of fluid flow and acoustic field of a supersonic jet using vorticity confinement

In this study, the numerical simulation of the fluid flow and acoustic field of a supersonic jet is performed by using high-order discretization and the vorticity confinement (VC) method on coarse grids. The three-dimensional Navier-Stokes equations are considered in the generalized curvilinear coordinate system and the high-order compact finite-difference scheme is applied for the space discretization, and the time integration is performed by the fourth-order Runge-Kutta scheme. A low-pass high-order filter is applied to stabilize the numerical solution. The non-reflecting boundary conditions are adopted for all the free boundaries, and the Kirchhoff surface integration is utilized to obtain the far-field sound pressure levels in a number of observer locations. Comparisons of the jet mean flow and jet aeroacoustics results with the other numerical and experimental data at similar flow conditions are made and show a reasonable agreement. The study shows that the proposed solution methodology based on the high-order compact finite-difference scheme in conjunction with the VC method can reasonably predict the near-field flow and the far-field noise of high Reynolds number jets with a fairly coarser grid than that used in the large eddy simulations and, thus, the computational cost can be significantly decreased.

Association analysis of -416 G>C polymorphism of T-cell immunoglobulin and mucin domain-1 gene with asthma in Iran

TIM (T-cell immunoglobulin (Ig) and mucin domain)-1, one of the members of TIM family, expresses on Th2 cells and promotes the production of Th2 signature cytokines. This can increase a series of responses in these cells which could be one of the causes of asthma or asthma-related phenotypes. The aim of this study was to investigate whether a TIM-1 promoter single nucleotide polymorphism (SNP), -416 G>C, is associated with asthma in Iranian population. In this case-control study, existence of the -416 G>C polymorphism was assessed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) in 300 patients with asthma (97 atopic, 203 nonatopic) and 309 healthy volunteers. Additionally, the relationship between these polymorphism genotypes and total serum IgE levels in this Iranian population was evaluated. We discovered a significant association between the -416 G>C polymorphism and atopic asthma susceptibility in the population, but this SNP showed no connection with nonatopic asthma (P < 0.05). However, our results showed significant relation between this polymorphism and serum IgE level (P < 0.05). Our results suggest that -416 G>C polymorphism in TIM-1 gene could be a predisposing factor for atopic asthma in Iranian population, and CC genotype of this SNP can be associated with increased level of IgE in patients with asthma in the same population.

A completed audit cycle on post-tonsillectomy haemorrhage rate: coblation versus standard tonsillectomy

CONCLUSION

A significant reduction in post-tonsillectomy secondary haemorrhage rate was observed after coblation tonsillectomy was abandoned in our department.

OBJECTIVE

Comparison of the postoperative haemorrhage rate following coblation tonsillectomy and routine dissection tonsillectomy.

PATIENTS AND METHODS

This was a retrospective study. In the first audit period, 441 sequential tonsillectomies between January and September 2002 were reviewed. Coblation was compared with cold steel and diathermy dissection with either ties and/or diathermy used for haemostasis. Coblation tonsillectomy was subsequently abandoned in our unit and, in the second audit period, all tonsillectomies (n=416) between July 2003 and August 2004 were included. Statistical analysis was performed using the chi2 test.

RESULTS

The overall primary haemorrhage rate in the first audit cycle was 1.8% (8/441). In the second cycle with no coblation procedures, 1.4% of patients (6/416) suffered from primary haemorrhage (c.f. 8/441 (1.8%) in the first cycle, p=0.666). Secondary haemorrhage, was seen among 15.4% of patients (68/441) in the first audit cycle. In the second cycle, after coblation was discontinued, the secondary haemorrhage rate fell significantly (p<0.001) to 5.8% (24/416). A breakdown of the results of cold steel/diathermy and coblation techniques in both adults and children is also presented.

How many clinic visits does it take to treat distal radial fractures?

The purpose of this study was to evaluate the changes in alignment during the course of treatment for extra-articular distal radius fracture and the relationship of initial and intermediate radiographs, with the final radiograph taken at fracture union. A cohort of 96 consecutive patients who were conservatively managed for extra-articular distal radius fracture in an 18-month period was undertaken. The radiographs analysed were taken at prereduction, postreduction, a week later and at fracture union. The radiological parameters analysed were radial tilt, radial length, radial inclination, dorsal comminution and ulnar styloid fracture. There was a significant change in radiographic alignment between initial and immediate postreduction radiographs, and between postreduction 1 week later radiographs (p < 0.05), but the number of patients in the 1 week later and fracture union groups remained similar (p > 0.05). All patients with poor radiological outcome had ulnar styloid fractures. This was also associated with dorsal comminution in 86% of patients. Patients with satisfactory radiological outcome had ulnar styloid fracture and comminution in 34% and 43% of patients respectively. The final radiological outcome was not found to be influenced by initial unsatisfactory alignment of radial tilt, radial length and radial inclination individually or in combination. We suggest that two clinic visits after initial reduction of the fracture should be sufficient to manage such injuries; the first visit 1 week after manipulation to detect unacceptable displacement and if found satisfactory, the last visit at fracture union for final review, advice and referral to physiotherapy.