An experimental study of the influence of spike in supersonic and transonic flows past a hemispheric body

The air intake should be operated at design conditions to achieve a high total pressure recovery and optimum mass capture ratio. The current research focuses on the numerical simulation of the supersonic and hypersonic air inlet and its starting and unstarting characteristics. 2D RANS equation for supersonic and hypersonic intake has been solved using the k-oSST turbulence model. The in-house code and the algorithm based on the RANS equation have also been validated in due process and used for subsequent simulations. The sudden drop in mass capture ratio indicates the unstart condition of the intake. The presence of a bleed section has a commendable effect on the performance parameter of the air intake. A separation bubble was observed at the intake's entrance during the off-design conditions, resulting in performance losses. Four different bleed sections ranging in size from 1.6mm to 8.6mm were used, and simulations with bleed were run for different Mach numbers ranging from 3 to 8. The optimum bleed size of 3mm has been found quite effective in modifying Total pressure recovery within the optimum mass flow rate over the wide range of Mach numbers.

Section: Geometry and Gridmentioning

confidence: 84%

Passive flow modification over the supersonic and the hypersonic air-intake system using bleed

Sinha,

Singh,

Prakash

et al. 2023

“…Step 4: The above equation was raised to the power n = 1 and p = 1.253343 as shown in equation (15); Solver reported n = 1.491785 and p = 0.712427. In Fig.…”

Section: Construction Of the Empirical Equationmentioning

confidence: 99%

“…It should be noted that for ideal flows, quasi-onedimensional models have applications in wind tunnels, nozzles, and diffusers, among others [2][3][4]. Reference is made to some wind tunnel tests, such as the experi-mental study on the influence of the length of the spike on the aerodynamic characteristics of blunt bodies for various angles of attack and Mach and Reynolds numbers [15]. Study of experimental tests on the calibration of a wind tunnel, where a calibration model is used that represents a generic configuration of a winged missile [16.17] presents comparative results for the standard AGARD-B model in the transonic speed range tested in six wind tunnels.…”

Section: Introductionmentioning

confidence: 99%

Empirical equation of the Mach number as a function of the stagnation pressure ratio for a quasi-one-dimensional compressible flow

Tolentino¹

2023

In the present work for a quasi-one-dimensional isentropic compressible flow model, an empirical equation of the Mach number is constructed as a function of the stagnation pressure ratio for an analytical equation that algebraic procedures cannot invert. The Excel 2019 Solver tool was applied to calibrate the coefficients and exponents of the empirical equation during its construction for the Mach number range from 1 to 10 and 1 to 5. A specific heat ratio from 1.1 to 1.67 and the generalized reduced gradient iterative method were used to minimize the sum of squared error, which was set as the objective function. The results show that for Mach 1 to 10, an error of less than 0.063% is obtained, and for Mach 1 to 5, an error of less than 0.00988% is obtained. It is concluded that the empirical equation obtained is a mathematical model that reproduces the trajectories of the inverted curves of the analytical equation studied.

Aerodynamic analysis of an AK-47 bullet moving at mach 2.0 in close proximity to the ground

Gholap¹,

Salokhe²,

Ghadage³

et al. 2022

The bullet is shot near the wall or the ground during urban warfare. This nearness leads to a pressure distribution on the bullet's entire body, which is asymmetric. For every case of difference in the height of the ground/wall proximity, the shock reflection angle changes, and a particular shock wave's effect on the bullet varies. In the present study, the flowfield around a 7.82-mm bullet of an AK-47 Rifle moving at a supersonic speed of Mach 2 near the ground is studied using Computational Fluid Dynamics. Computational simulations have been carried out for the bullet moving at different heights from the nearby wall. The level of impact on the projectile is illustrated from the region of nearest influence to a ground distance which is five times the bullet's diameter. Ground effects from height to diameter ratios (h/D) of 0.25 to 5 are showcased, describing the influence on overall flowfield, pressure coefficient distributions, lift drag, and moment coefficients. The wake region flow field is also analyzed. It has been observed that a detached bow shock wave is generated at the tip of the bullet, which increases the drag coefficient experienced by the bullet. Generation of lift is the maximum for certain h/D cases like 1.0, 1.5, and 2.0 as the shock reflections from the ground hit the bullet. Further increasing the altitude from the near-wall reduces the lift and drag forces acting on the bullet due to the lesser ground effect. From the present investigation, the heights above the h/D ratio of 2.0 are suitable for firing the shot.