High resolution numerical simulation of triple point collision and origin of unburned gas pockets in turbulent detonations

A key issue in pulse detonation engine development is better understanding of the detonation structure and its propagation mechanism. Thus, in the present work the turbulent structure of an irregular detonation is studied through very high resolution numerical simulations of 600 points per half reaction length. The aim is to explore the nature of the transverse waves during the collision and reflection processes of the triple point with the channel walls. Consequently the formation and consumption mechanism of unreacted gas pockets is studied. Results show that the triple point and the transverse wave collide simultaneously with the wall. The strong transverse wave switches from a primary triple point before collision to a new one after reflection. Due to simultaneous interaction of the triple point and the transverse wave with the wall in the second half of the detonation cell, a larger high-pressurised region appears on the wall. During the reflection the reaction zone detaches from the shock front and produces a pocket of unburned gas. Three mechanisms found to be of significance in the re-initiation mechanism of detonation at the end of the detonation cell; i: energy resealed via consumption of unburned pockets by turbulent mixing ii: compression waves arise due to collision of the triple point on the wall which helps the shock to jump abruptly to an overdriven detonation iii: drastic growth of the Richtmyer–Meshkov instability causing a part of the front to accelerate with respect to the neighbouring portions.

Mobile Phones and Contact Arrangements for Children Living in Care

This article reports the findings from the first UK study to examine the use of mobile phones by looked after children. Contact with family and friends is important, but it has sometimes to be carefully managed to avoid unintended consequences such as placement instability. The study examined the ways in which mobile phone technology impacts on contact, drawing on the experiences of children and young people in foster-care and residential care, and of policy makers, social workers, foster parents and residential care staff. No guidance was available that addressed the issue of mobile phone contact arrangements for looked after children and young people. Three years on from the start of the study, this remains the case in the area where the study was conducted, resulting in variation in the way mobile phone use for contact is managed; the issue appears only to be specifically addressed when identified as a problem. The position of mobile phone facilitated contact as a recognised form of contact requires review. The evidence suggests it should routinely form part of children’s care plans, and that residential staff and foster parents need to be adequately prepared and supported for the dynamics of mobile phone facilitated contact.