**2.2 Processing**

At this stage, the preprocessed settings are evaluated or computed using the solver which is tailored to our specific requirements with the options selected earlier. The processing depends on the stopping criteria for resolution of different number of iterations. Once the correct models and settings are chosen for physics


#### **Table 2.**

*Continua meshing parameters for STAR-CCM+.*


#### **Table 3.**

*Specific mesh optimization for aircraft body region parameters.*

*Development of the Flight Dynamic Model (FDM) Using Computational Fluid Dynamic (CFD)… DOI: http://dx.doi.org/10.5772/intechopen.91895*

conditions, then the simulations are processed for examination of the applied conditions. Here, the air properties, other physical conditions, result extraction for aerodynamic coefficients, and graphical depiction of iterated data were selected. Physical condition and fluid dynamics models implemented are listed below:


properties, and growth rate with the smallest practical mesh even for exceptionally intricate geometries. STAR-CCM+ also employs a face-based solver technology

For meshing user-specified parameters that were assigned are shown in **Table 2**,

**Tables 2** and **3** values were evaluated after repetitive attempts to achieve a welldefined and fine mesh at zero angle of attack steady flight. After running meshing method, software generated approximately 12 million cells in the mesh. The process of meshing was repeated with mild tweaks in values for every case of angle of attack and control surface deflections. For each case of flight profile, the number of cells in a mesh increases with changes in angle of attack, sideslip, and various configura-

At this stage, the preprocessed settings are evaluated or computed using the solver which is tailored to our specific requirements with the options selected earlier. The processing depends on the stopping criteria for resolution of different number of iterations. Once the correct models and settings are chosen for physics

Base size 1.0 m Number of prism layers 12 Size type Relative to base Percentage of base 33.33% Absolute size 0.3333 m #Pts/circle 40.0 Curvature deviation distance 0.01 m Thickness of near-wall prism layer 0.008 m

Number of prism layers 15 Size type Relative to base Percentage of base 25% Absolute size 0.25 m #Pts/circle 42.0 Curvature deviation distance 0.01 m Relative minimum size: percentage of base 5% Relative minimum size: absolute size 0.05 m Relative target size: percentage of base 6.0% Relative target size: absolute size 0.08 m Thickness of near-wall prism layer 0.006 m

uniquely designed to recognize arbitrary polyhedral cell topology [9]."

tions of control surfaces.

*Computational Fluid Dynamics Simulations*

**Continua meshing parameters**

*Continua meshing parameters for STAR-CCM+.*

*Specific mesh optimization for aircraft body region parameters.*

**Aircraft body region parameters**

**2.2 Processing**

**Table 2.**

**Table 3.**

**150**

these were values adopted for a four-engine turboprop transporter aircraft.


The aerodynamic coefficients generated in the final report were as follows:

*Cl* ¼ roll moment coefficient *Cm* ¼ pitch moment coefficient *Cn* ¼ yaw moment coefficient *CL* ¼ lift coeffeicient *CD* ¼ drag coefficient *CY* ¼ side force coeffeceint

These parameters were set up, and each case of simulation had certain control surface deflection and angle of attack. For a four-engine turboprop transporter aircraft, 372 cases were chosen. These cases proved to be sufficient for attaining high-fidelity flight dynamic model for aircraft simulator. The air speed was kept constant at 220 knots and at an altitude of 5000 feet. Air density and viscosity were set up accordingly. After all these steps, the CFD software is ready for analysis. By simply clicking on run button on the top pane, STAR-CCM+ starts running iteration and plots the results simultaneously.

The CFD software as mentioned earlier requires sufficient computer hardware to function properly. The elapsed time for analysis was almost 6 hours for a highend desktop configuration machine in year 2017. Compared to this, same analysis was done within 3 h on a high-end machine in year 2018 with new specifications. For better and faster results, cluster computers and supercomputers are used to run CFD simulations for acquiring tremendous amount of data sets.

#### **2.3 Post-processing**

The results attained for aircraft aerodynamics from the CFD simulations are then used by the FDM's aerodynamic module. Results obtained are of forces and moment coefficients for six different axes, i.e., drag, lift, side force, roll, pitch, and yaw axes, with deflected surfaces at different angles.
