Open Access

CFD Study of Base Drag of the Grot Rocket

Nezar Sahbon
Nezar Sahbon
, 
Maciej Michałów
Maciej Michałów
, 
Siddharth Murpani
Siddharth Murpani
, 
Paulina Żurawka
Paulina Żurawka
 and 
Kacper Kaczmarek
Kacper Kaczmarek
   | Jun 12, 2023
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Article Category: research article
Published Online: Jun 12, 2023
Page range: 1 - 16
Received: Apr 24, 2022
Accepted: Mar 02, 2023
DOI: https://doi.org/10.2478/tar-2023-0007
Keywords
© 2023 Nezar Sahbon et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1.

Visualisation of the Grot sounding rocket.
Visualisation of the Grot sounding rocket.

Figure 2.

Conical rocket nozzle [7].
Conical rocket nozzle [7].

Figure 3.

From left to right: (A) under-expanded nozzle, (B) ideally expanded nozzle and (C) over-expanded nozzle; based on http://www.braeunig.us/space/sup1.htm.
From left to right: (A) under-expanded nozzle, (B) ideally expanded nozzle and (C) over-expanded nozzle; based on http://www.braeunig.us/space/sup1.htm.

Figure 4.

Axial forces acting on the Grot rocket.
Axial forces acting on the Grot rocket.

Figure 5.

Technical drawing of Grot’s nozzle.
Technical drawing of Grot’s nozzle.

Figure 6.

Grot’s shape outlines and domain regions in Ansys® DesignModeler.
Grot’s shape outlines and domain regions in Ansys® DesignModeler.

Figure 7.

Fluid domain dimensions. L denotes the total length of the Grot sounding rocket.
Fluid domain dimensions. L denotes the total length of the Grot sounding rocket.

Figure 8.

Fluid domain regions.
Fluid domain regions.

Figure 9.

Near-nozzle mesh.
Near-nozzle mesh.

Figure 10.

Global view of the mesh.
Global view of the mesh.

Figure 11.

Contour plot of the local Mach number—active propulsion system, Mach 1.2.
Contour plot of the local Mach number—active propulsion system, Mach 1.2.

Figure 12.

Contour plot of the local Mach number— inactive propulsion system, Mach 1.2.
Contour plot of the local Mach number— inactive propulsion system, Mach 1.2.

Figure 13.

Contour plot of the local static pressure—active propulsion system, Mach 1.2.
Contour plot of the local static pressure—active propulsion system, Mach 1.2.

Figure 14.

Contour plot of the local static pressure—inactive propulsion system, Mach 1.2.
Contour plot of the local static pressure—inactive propulsion system, Mach 1.2.

Figure 15.

Contour plot of the local static pressure in the nozzle area—active propulsion system, Mach 1.2.
Contour plot of the local static pressure in the nozzle area—active propulsion system, Mach 1.2.

Figure 16.

Contour plot of the local static pressure in the nozzle area—inactive propulsion system, Mach 1.2.
Contour plot of the local static pressure in the nozzle area—inactive propulsion system, Mach 1.2.

Figure 17.

Areas of interest in the rear of the rocket. Black denotes the nozzle exit area, while red denotes the aft end.
Areas of interest in the rear of the rocket. Black denotes the nozzle exit area, while red denotes the aft end.

Figure 18.

Total drag coefficient as a function of Mach number.
Total drag coefficient as a function of Mach number.

Figure 19.

Comparison of base drag coefficients obtained by CFD and the analytical model found in [4].
Comparison of base drag coefficients obtained by CFD and the analytical model found in [4].

Figure 20.

Difference in the total drag coefficient between active and inactive propulsion systems. Interpolation performed by the modified Akima method.
Difference in the total drag coefficient between active and inactive propulsion systems. Interpolation performed by the modified Akima method.

Figure 21.

ΔCD compared to the sum of engine-off nozzle exit pressure drag Coff and pressure change in the aft end due to engine operation.
ΔCD compared to the sum of engine-off nozzle exit pressure drag Coff and pressure change in the aft end due to engine operation.

Figure 22.

ΔCD for altitudes of 0 km and 5 km.
ΔCD for altitudes of 0 km and 5 km.

Computed drag coefficients.

M [-] CDon[−]$C_D^{on}[ - ]$ CDoff[−]$C_D^{off}[ - ]$ ΔCD[–]
0.3 0.460 0.453 -0.007
0.6 0.378 0.457 0.079
0.8 0.359 0.462 0.100
1.0 0.494 0.668 0.170
1.2 0.628 0.744 0.120
1.6 0.577 0.659 0.080
2.0 0.506 0.576 0.070
2.5 0.435 0.495 0.060
3.0 0.383 0.429 0.046

Grot main dimensional parameters.

Parameter Value [m]
Total rocket length 2.000
First stage length 0.983
Second stage length 1.017
First stage diameter 0.135
Second stage diameter 0.045
Reference diameter 0.135
Pre-flight distance of centre of mass from the rocket’s base 0.979
Nozzle exit diameter 0.084
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