## 4 Discussion  
The experimental tests carried out in the wind tunnel allowed for the comparison of the obtained results with the literature data(see Figures 23 and 24). Figure 22: Comparison of the force coefficients \(\text{C}_{\text{X}}\) and \(\text{C}_{\text{Y}}\) for the experimental and numerical results as a function of angle of wind attack \(\beta\) in the jib truss model with turbulent flow. Figure 23: Comparison of the selected aerodynamic coefficients \(C_{X}\) in function of the solidity ratio \(\varphi\) of the tower truss model with the available literature and standards data (According to Institute of Aviation [53], [PERSON] [54], Cohen & Perrin [55] and English [56] standards). Figure 24: Comparison of the selected aerodynamic coefficients \(C_{X}\) in function of the solidity ratio \(\varphi\) of the jib model with the available literature and standards data (According to [PERSON] [54] and English [56] standards). Figure 23 shows the research results of the Institute of Aviation [53] for spatial trusses with a square base made of steel sections (black curve) and pipes (red curve). The equation of the curve for the steel section \(\mathrm{C_{x0}}(\varphi)\)[53] is as follows:  
\[C_{x0}|^{steel\ sections}=4.1\varphi^{2}-\left(6.0-\frac{0.67}{k}\right)\varphi- \frac{0.13}{k}+4.1\, \tag{9}\]  
and the equation of curve for the tube \(\mathrm{C_{x0}}(\varphi)\) is as follows:  
\[C_{x0}|^{tube}=2.42-\frac{0.16}{k}-2.5\varphi\to C_{x0}\geq 1.4. \tag{10}\]  
In the studied case, according to the ISO-4302 standard [5], the solidity ratio \(\varphi\) of the tower model is given as:  
\[\varphi=\frac{A_{ref}}{A_{e}}=\frac{0.021438}{0.098532}\cong 0.22 \tag{11}\]  
where \(A_{e}\) is the enclosed area. \[k=\frac{b}{a}=1 \tag{12}\]  
where \(k\) is the spacing ratio (relative distance between the walls of the truss structure of the tower model), and \(a\) (breadth of section across wind front) and \(b\) (depth of section parallel to window flow) are the lengths of the side walls. Based on the above data, \(\mathrm{C_{x0}}\) is written as [53]  
\[C_{x0}|^{steel\ sections}=4.1\cdot 0.22^{2}-0.22\bigg{(}6.0-\frac{0.67}{1}\bigg{)}- \frac{0.13}{1}+4.1=2.99 \tag{13}\]  
\[C_{x0}|^{tube}=2.42-\frac{0.16}{1}-2.5\cdot 0.22=1.71 \tag{14}\]  
The findings for the truss model are as follows:  
* For \"quasi-laminar\" flow, the value of the drag coefficient \(\mathrm{C_{X0}}\) obtained from the tests was 2.54 (Figure 23), and its value is between the curves given by [PERSON] [53]. Note that the value of \(\mathrm{C_{X45}}\), which is equal to 3.22, fits the curve given by [PERSON] and [PERSON] [55]. This value is almost equal to \(\mathrm{C_{X0}}^{t}\), which is equal to 3.27. * For turbulent flow, the drag coefficient \(\mathrm{C_{X0}}^{t}\) obtained from the tests was 3.27, and \(\mathrm{C_{X45}}^{t}\) was 4.11 (Figure 23). This proves the high impact of turbulence on the tested object. The \(\mathrm{C_{X0}}^{t}\) coefficient is in line with the curve given by [PERSON] and [PERSON] [55] for a wind angle of attack of \(\beta=45^{\circ}\). Similarly, the selected aerodynamic coefficients \(\mathrm{C_{X}}\) for the jib truss model were calculated. Figure 24 shows the dependency \(\mathrm{C_{X}}=\mathrm{f}(\varphi)\) for spatial trusses on the triangular base made of steel structural sections and tube, as recommended by French [54] and English [56] standards, and the results of the wind tunnel tests. According to the ISO-4302 standard [5], the solidity ratio of the tested model of the jib is given by  
\[\varphi=\frac{A_{ref}}{A_{e}}=\frac{0.017304}{0.104244}\cong 0.17 \tag{15}\]  
The findings for the jib model are as follows:  
* For \"quasi-laminar\" flow, the resistance coefficient \(\mathrm{C_{X90}}\) obtained from the tests was 2.16 (Figure 24) and is close to the value from the curve given by the French standard for steel sections.