چكيده به لاتين
With the advancement of aerodynamic science in the field of aviation industry, every year we see dramatic changes in the emergence of drones from powerful countries. Unfortunately, due to security issues, these countries do not provide almost any information in different parts of this field, especially about aerodynamics, to the researchers of other countries. Effective control of drones at high angles of attack is one of the important issues of these planes.
The current research focuses on the structure of unsteady flow in a delta wing, where the behavior of stalling and flow separation is different according to the changes in the angle of attack between 10 and 35 degrees and the angle of roll between 20 and 40 degrees.
The results show that by increasing the angle of attack in conditions where there is no roll angle, the power of separation and destruction of the flow on the wing increases. By excessively increasing the angle of attack (angle of attack 35 degrees), the phenomenon of stalling will occur, which in turn has a negative effect on the control and stability of the flying vehicle. The obtained results show that by increasing the angle of attack, when the flow passes from the tip of the wing towards the trailing edge, it is observed that the separation is qualitatively larger and its area on the surface of the wing increases.
In the second stage, the results related to the effect of changes in roll angles on the size and strength of separation on the wing are presented experimentally and with the help of thread detection and numerical results. At a roll angle of -35 degrees, the threads near the root of the wing are separated from the surface. At the -40 degree roll angle, the direction of the threads is reversed, this is the region where the separation has occurred and the current has lifted from the surface.
In the third stage, when the angle of attack and roll are applied simultaneously, the data shows that at an angle of attack of 15 degrees and a roll of -30 degrees, the speed line has the greatest decrease, and this means that applying these two angles simultaneously for the drone It is not suitable because the speed reduction is significant in these two angles.
In the numerical analysis section, the results showed that at the angle of attack of 35 degrees, we see flow separation in all sections of the wing. In fact, at this angle, the flow is completely destroyed on the wing, and this confirms the results of the experimental test and the detection by the thread. According to experimental observations and numerical analysis, at attack angles of 20, 30, and 35 degrees, the separation of the flow and The pressure gradient is reversed.
