• Special care must be taken so that highly skewed and negative volume elements are not generated. Unstructured Grid: The unstructured grid can be made of any type of elements ranging from triangle, quadrilateral to tetrahedral, prism, pyramids and hexahedral.Advantages: • The density of the grid can be controlled in any region without worrying too much about increasing density in another region • Easy to use with complex geometries. Can be calculated in an hour• You don't have to worry much about skew or poor quality since the grid generation algorithm takes care of that most of the time. Disadvantages: • Each cell can be indexed based on a single variable which causes that variable to be very large and thus increases the computational load • Causes a larger numerical spread than a structured gridChapter 3The scramjet model3.1 Configurations of the scramjet engineThe Scramjet engines can be used as a propulsion system for cruise missiles, military aerospace aircraft and space launch vehicles. The Scramjet-powered aerospace aircraft can propel small payloads using hydrocarbons as fuel during SSTO (Single Stage to Orbit) horizontal takeoff and propel large payloads when using hydrocarbons as fuel and when is likely to succeed on the second stage of the TSTO (two From stage to orbit). Different types of Scramjet engines have been developed during the research on this one to overcome the drawbacks or disadvantages of others. The types are classified based on the inlet shape, combustion chamber shape and fuel injection system.3.2 The New ModelThe model of scramjet engines used to perform the analysis consists of three parts as follows :i) The inlet ramp ii) The combustion chamber iii) The outlet3.2.1 The isometric views of the engine model (CATIA V5)The ...... middle of paper ......interested in the capturing the physics of the internal flow of the configuration, we created a structured mesh inside the engine and unstructured otherwise.Fig. 5.2: Structured mesh in the internal domain near the wall of the ramp. To capture the physics of flow near the wall of the engine, we need to increase the density of cells near the wall. A grid was generated in the computational domain of the simulations using the ICEM cfd grid generator package (Ansys 14.5). The first layer of grid near the motor wall measured nearly 20 microns and so the grid is finer at the motor walls and relatively coarser away from the motor walls. Fig. 5.3: Finer grid closer to the wall and further away from it (Combustion chamber) In addition to the internal section of the configuration the external domain was created with the unstructured grid. So overall the simulations were carried out using a hybrid network.