Usage of extruded diamond multi-injectors for improvement of fuel mixing inside the supersonic combustion chamber.

The main attention of this work is to investigate the usage of diamond multi extruded injectors on the fuel distribution in combustor of scramjet. This study applied the computational technique to simulate the transverse fuel jets released from extruded nozzles. The main focus is to evaluate the role of induced shock waves on the penetration and distribution of fuel jets. The effects of jet space and usage of annular nozzle for the fuel injection system are revealed. Results of this work shows that the gap of jet would be more efficient for mixing when the inner air jet is also used. Also, injection of the air from the core of annular nozzle significantly increase the fuel mixing.

Reduction of rupture risk in ICA aneurysms by endovascular techniques of coiling and stent: numerical study.

The initiation, growth, and rupture of cerebral aneurysms are directly associated with Hemodynamic factors. This report tries to disclose effects of endovascular technique (coiling and stenting) on the quantitative intra-aneurysmal hemodynamic and the rupture of cerebral aneurysms. In this paper, Computational Fluid Dynamic are done to investigate and compare blood hemodynamic inside aneurysm under effects of deformation (due to stent) and coiling of aneurysm. The blood stream inside the sac of aneurysm as well as pressure and OSI distribution on the aneurysm wall are compared in nine cases and results of two distinctive cases are compared and reported. Obtained results specifies that the mean WSS is reduced up to 20% via coiling of the aneurysm while the deformation of the aneurysm (applying stent) could reduce the mean WSS up to 71%. In addition, comparison of the blood hemodynamic shows that the blood bifurcation occurs in the dome of aneurysm when endovascular technique for the treatment is not applied. It is found that the bifurcation occurs at ostium section when ICA aneurysm is deformed by the application of stent. The impacts of coiling are mainly limited since the blood flow entrance is not limited in this technique and WSS is not reduced substantial. However, usage of stent deforms the aneurysm angle with the orientation of parent vessel and this reduces blood velocity at entrance of the ostium and consequently, WSS is decreased when deformation of the aneurysm fully occurs. These qualitative procedures provide a preliminary idea for more profound quantitative examination intended for assigning aneurysm risk of upcoming rupture.

Computational study of the blood hemodynamic inside the cerebral double dome aneurysm filling with endovascular coiling.

The rupture of the aneurysm wall is highly associated with the hemodynamic feature of bloodstream as well as the geometrical feature of the aneurysm. Coiling is known as the most conventional technique for the treatment of intracranial cerebral aneurysms (ICA) in which blood stream is obstructed from entering the sac of the aneurysm. In this study, comprehensive efforts are done to disclose the impacts of the coiling technique on the aneurysm progress and risk of rupture. The computational fluid dynamic method is used for the analysis of the blood hemodynamics in the specific ICA. The impacts of the pulsatile blood stream on the high-risk region are also explained. Wall shear Stress (WSS) and Oscillatory shear index (OSI) factors are also compared in different blood viscosities and coiling conditions. According to our study, the hematocrit test (Hct) effect is evident (25% reduction in maximum WSS) in the two first stages (maximum acceleration and peak systolic). Our findings present that reduction of porosity from 0.89 to 0.79 would decrease maximum WSS by about 8% in both HCT conditions.