Simulation in the aerospace industry is very commonly used, but in the emerging drone technology there is still a lot to investigate to create much more efficient and secure devices. The focus of this study will be around obtaining the real thrust of each propeller for the motors installed instead, in comparison with the theorical data given by the datasheets of the manufacturers. Computer fluid dynamics (CFD) simulation will be used for this purpose.
Figure 1 – Drone CFD SIMULATION
CFD enables the performance of different kind of simulations in relatively short times and with a clear cost saving, compared to the testing facilities. We will start from the theoretical thrust at maximum motor speed (rpm) given by the manufacturer, to get obtain the real graph of the thrust vs. rpm.
The first CFD simulation was run to obtain the real maximum thrust for maximum rpm supported by one propeller and engine. Obtaining:
W (rpm) THRUST (N)
If we compare with the thrust given in the below datasheet, we can see clear correlation between simulation and the nominal values.
Figure 2 – Nominal thrust given by the datasheet
The following table summarizes the accuracy of the simulation, which is below 1%.
Figure 3 – Comparison table
The next step is to investigate the real drone behavior at the different rpms. Drone behavior cannot be known with the nominal motor characteristics, so typically it is assumed a linear behavior, which is far from being accurate.
In this sense, the thrust was calculated using simulation for rpm in the same way as done before. In order to stay within a reasonable calculation time Intervals of 200-300 rpm were assumed. In this way, we obtained a real data sheet polynomic curve, that has been extracted by a curve fitting method.
From here, the following graph was built comparing both theoretical and a real thrust at different rpms
Figure 4 – Nominal and simulated thrust comparison
We can see the difference between the thrust obtained with CFD simulation and the thrust given by manufacturers. The theorical equation assumes linear behavior, while the real behavior follows a polynomic equation. Allowing a more accurate prediction of the efficiency at each rpm.
The calculation time is a very important topic in this kind of simulations, and the size and quality of the mesh plays a major role. If you want to know more about these topics pelase get in touch with us.
I would like to thank the support of the team of IBTICAE SL which is a firm focused on high end engineering solutions in different areas of the product Design cycle, with specific expertise in drones. The present study has been developed in the frame of a collaboration with a Research institution. The company experience in studying complex FE Analysis and CFD studies with drones has enabled the good cooperation to perform this work.
If you find this post interesting and useful for you or your company please contact me on my Linkedin to know more.
Pablo Hidalgo Gómez