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.

Numerical study of lateral coolant jet on heat reduction over nose cone with double-aerodome at hypersonic flow.

One of the main challenges in designing a supersonic forebody is thermal protection. The application of the mechanical spike mounted at the nose considerably decreases the heat load on the main body. In this investigation, the hybrid technique of mechanical spike and coolant injection are examined to reduce the thermal load on the nose cone in the supersonic air stream. A three-dimensional model of a double aerodisked spike with different cooling systems is provided to find the efficient cooling injection system for reducing the heat load on the nose cone. Computational studies have been done on investigating a cooling mechanism in the proposed injection systems. This study has tried to present valuable information on flow features and shock interaction nearby the nose. The influence of different coolant gas on the thermal performance of the proposed configurations is comprehensively explained. Our results indicate that the cooling performance of single carbon dioxide is 85% more than helium jet in lateral injection. According to our findings, the cooling performance of lateral multi-jets is 90% more than opposing ones.

Influence of coolant multi-jets on heat reduction of nose cone with blunt spike at hypersonic flow.

The importance of the cooling system for the design of the forebody of high-speed vehicles is significant due to severe aerodynamic heating at hypersonic flight. In the present study, injection of multi and single-coolant jets on the thermal performance of forebody design of nose cone with the cut spike is thoroughly investigated at hypersonic flow. A three-dimensional model of the blunt cone is presented for computational investigations of proposed jet and spike configurations. Injection of two coolant gasses (Helium and carbon dioxide) into the cooling system of the nose cone with a blunt spike is investigated. Three locations for both opposing and lateral jets are compared to find the efficient jet location. Our results indicate that a single lateral jet injected from the tip of the spike is more efficient for heat reduction. A comparison of the multiple injection system also shows that the heat reduction of the helium gas is about 15% more than CO2 jets.