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Ureteral peristalsis can be considered as a series of waves on the ureteral wall, which transfers the urine along the ureter toward the bladder. The stones that form in the kidney and migrate to the ureter can create a substantial health problem due to the pain caused by interaction of the ureteral walls and stones during the peristaltic motion. Three-dimensional (3D) computational fluid dynamics (CFD) simulations were carried out using the commercial code ansys fluent to solve for the peristaltic movement of the ureter, with and without stones. The effect of stone size was considered through the investigation of varying obstructions of 5%, 15%, and 35% for fixed spherical stone shape. Also, an understanding of the effect of stone shape was obtained through separate CFD calculations of the peristaltic ureter with three different types of stones, a sphere, a cube, and a star, all at a fixed obstruction percentage of 15%. Velocity vectors, mass flow rates, pressure gradients, and wall shear stresses were analyzed along one bolus of urine during peristalsis of the ureteral wall to study the various effects. It was found that the increase in obstruction increased the backflow, pressure gradients, and wall shear stresses proximal to the stone. On the other hand, with regard to the stone shape study, while the cube-shaped stones resulted in the largest backflow, the star-shaped stone showed highest pressure gradient magnitudes. Interestingly, the change in stone shape did not have a significant effect on the wall shear stress at the obstruction level studied here.

Jet propellant 10 [(JP-10) or exotetrahydrodicyclopentadiene]is one of the leading candidate fuels for use in pulse detonation engine applications.As such, its ignition delay characteristics have been studied previously in very dilute mixtures at pressures from 1 to 9 atm and temperatures from 1300 to 1670 K. The ignition delay times are studied of JP-10/air and JP-10 blended with methylated PCU alkene dimer, nitronorbornane, dinitronorbornane, and ethylhexyl nitrate in air at pressures from 10 to 25 atm and temperatures from 1200 to 2500 K using a shock tube. Ignition delays were primarily measured using CH emission and secondarily using OH emission. Ignition delays were essentially insensitive to all of the additives tested. Additionally, ignition delays for dicyclopentadiene (a suspected intermediate in the combustion of JP-10) were also tested. Above 1500 K, multiple peaks in the CH emission were found. Further tests using OH emission indicate that the main peak in CH emission at these higher temperatures is probably due to reactions involved in the approach to equilibrium and give spuriously long ignition delay times.

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