## 1 Introduction
Another benefit of hydrodynamic tunnels is that the model required for testing is smaller, resulting in cost savings. In the case of quantitative research, the obtained results converge for both types of tunnels. In paper [11], comparative studies were presented, conducted in both hydrodynamic and aerodynamic tunnels, which showed minor discrepancies between the results obtained using these methods. However, hydrodynamic tunnels allow for simultaneous load measurements and high-quality flow visualization above the model surface, enabling a direct correlation between loads and flow images. Additionally, a hydrodynamic tunnel enables testing the aerodynamic properties of an aircraft during dynamic changes in spatial position. A wide range of applications of hydrodynamic tunnels is described in [11; 12; 13; 14; 15; 16]. The research team in [11; 12; 13; 14] focuses on the comparative analysis of aircraft streamlining and stability characteristics of a known aircraft, while NASA teams [15; 16] focus on designing numerical models and verifying their results using experiments in wind and hydrodynamic tunnels. Furthermore, the work [17] shows the results of a hydrodynamic tunnel test of a micro aerial vehicle. During this study, the aerodynamic coefficients were measured and then used to obtain the aerodynamic derivatives using computational software. Additionally, [18] presents the results of static characteristic identification using the hydrodynamic tunnel. Some of the current literature contains references to research results that compare CFD simulation and data obtained with the use of a wind tunnel [19]. In that work, aerodynamic coefficients were estimated using CFD computation and the wind tunnel test. A comparison of the results shows a considerable difference between the data obtained with these two methods, which can be attributed to the challenges in accurately modeling turbulence, particularly in transitional flow. For this reason, this paper proposes to verify the calculations made using the CFD method through test results in a hydrodynamic tunnel. Research performed in a hydrodynamic tunnel enabled visualization and recording of the aerodynamic properties of the aircraft in the event of substantial dynamic changes in flow, e.g., related to flow detachment, stall and spin recovery, wind shear, and steep landing approach. The reliability of the presented work consists of a comparative analysis of the results obtained using the CFD method and hydrodynamic tunnel tests of the flow on the same scale. Both cases considered an aircraft model on a 1:50 scale generated using the same CAD model. The content of this paper is organized as follows: In the first section, the test model geometry based on the General Dynamics F-111 \"Aardvark\" aircraft is introduced and its reference parameters are defined, as well as the coordinate systems. Next, the simplifications and assumptions used in CFD computation and hydrodynamic tunnel tests are presented. The third section shows the results of the performed studies. Further discussion of the results obtained with both methods is presented. Finally, concluding remarks based on the achieved results are described.