Elliptical fin shape rocket free#
Design of Aerodynamically Stabilized Free Rockets. Since the elliptical nose shape gives the lowest drag force at 0.8 Mach, this shape was selected for further development of the rocket-target.
As for the conical nose shape, the drag coefficient varies from 0.286 to 0.466 in the same Mach number range. The drag coefficient of the rocket with the ogive, conical and elliptical nose shapes is very close and, in the range of 0.3…0.6 Mach number, it varies from approximately 0.272 (ogive) to 0.353 (0.5 power). Accordingly, these tendencies reflect on the drag coefficient. In the range of 0.6…0.8 Mach number, the lowest drag force is with the elliptical nose, then follow the ogive nose and the 0.5 power nose. In the range of 0.3…0.6 Mach number, the lowest drag force is with the ogive nose, then follow the 0.5 power nose and the elliptical nose. It is seen, that the drag force of the rocket with the ogive, conical and elliptical nose shapes is very similar. The simulation showed that the highest drag force was for the rocket with the conical nose in all velocity ranges. The analysis was carried out considering the compressible formulation of the Navier-Stokes equation system.Ī simulation of the airflow around rockets with different nose shapes is carried out and pressure contours, airflow streamlines, drag force and drag coefficient dependencies on the rocket’s velocity are obtained. The outside walls of the computational domain (the lateral boundaries) were defined as free slip walls. The surface of the rocket was defined as a non-slippery smooth wall. The standard atmosphere values of all the other thermodynamic variables at sea level were used as input flow conditions in the computations, that is a freestream static temperature of 15 ☌ and a freestream static pressure of 101327 Pa. The assigned range of velocity was between 0.3 and 0.8 Mach number. The grid contains an overall size of ~7.18 million elements including ~3.5 million prism elements (Fig. 2). On the surface of the rocket the grid was made distinctly denser, the size of prism elements was set to 3.75 mm. 20 layers of prism elements were created on the surface of the rocket with the maximum thickness of 15 mm and the growth rate 1.2. After a mesh sensitivity analysis, the maximum size of tetrahedral elements in the grid was set to 13.5 m and the minimum size was 7.5 mm. made up of prismatic elements in the viscous region located in close proximity of the body, whereas tetrahedral elements were used to fill the remaining fluid volume. The main objective of this paper is to identify an optimal configuration of a nose shape by a CFD simulation.Īn unstructured computational grid was generated inside this fluid volume. Therefore, CFD methods are widely used in order to predict aerodynamic characteristics of rockets during various development stages. CFD is suitable to use at conceptual design stage of the aerodynamic configurations as it is able to get aerodynamic characteristics from more configurations than wind tunnel testing. It is known that various aerodynamic characteristics have a great influence on the exterior ballistics of the rocket, however, the drag force and drag coefficient are the most important parameters necessary for the investigation of exterior ballistics.Ĭomputational fluid dynamic (CFD) techniques to calculate the aerodynamic coefficients of many complex geometry and complex flow phenomena were recently demonstrated. Several possible nose shapes are suitable in this case, such as various ogive, conical or elliptical shapes. The present design required developing a rocket-target for the system “Stinger” which is 5 meters in length and 0.4 meters in diameter, at a velocity range below 250 m/s. The range of rocket’s velocities can be rather wide. The geometrical and design parameters and the exterior ballistics characteristics of a rocket are usually estimated for a particular rocket design.
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