# Space Launcher Case Study

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Numerical Simulation of A Space Launcher Flow in the Subsonic Regime of the Ascent Introduction For a Space Launcher it is critical to gain an accurate estimate of the drag on the launcher. This is because it is one of the characteristics which determines how much fuel is needed to be carried on board, which in turn adds towards the total weight hence the cost of the launcher. Base drag is due to the afterbody of a space launcher which can account for up to 30% of the total drag (3) making the afterbody an important asset of the launcher to analyse for drag. When the propulsive jet stream exits the nozzle it mixes with the external stream creating a mixing layer due to a phenomenon known as jet entrainment. The larger the mixing layer the…show more content…
4 assertively expresses the need to align the grid lines with dominant flow features in order for the grid blocks to deform as the streamlines do. This is reinforced in 2 which states the blocks need to deform so they can follow the shape of the streamlines dividing the internal and external streams within the jet mixing layer. This makes it possible to capture the flow features around the streamlines better. Another common adaptation which can be made is stated in 5,4,2 where they decided to cluster the cells close to the walls to capture the boundary layer along with clustering the cells near flow regions of interest like eddies or wake mixing regions, where there may be high flow gradients due to expansion, to capture flow fields sharply 6. 4 expands on this expressing "It is crucial the grid density is high within the turbulent shear layers, as it is the shear stress that primarily drive the recirculation flow, and, hence determine the base pressure. 4 touches on an interesting point which is that a much refined computational grid is necessary in the regions of jet entrainment to capture it's physical effect on the flowfield. Figure #2 is a good visualisation of how a mesh can change through