**1. Introduction**

Stable flight dynamic modeling and designing of an aircraft is a crucial phase faced by the aviation industry. From these perspective, when it comes to on-ground training of pilots, simulative training is required before they can face actual dynamics of real flight. Smooth and stable flight is a necessary fact as the concerned pilot is not always alone, and also high risks are involved if the pilot is untrained with regard to aircraft dynamics. Therefore, ground training on flight simulators is given to pilots for a particular aircraft. However, for the particular aircraft to run on flight simulators, initially its flight dynamic model (FDM) is designed.

#### **1.1 Why one should design FDM?**

It's a question of interest, why one should design FDM?, because the FDM is a heart for flight simulator [1]. The current dire need of flight simulators is captured from the high rate of hiring of new pilots and indulgence of the airlines whether it is in Pakistan or international forum. As the hiring and training of new pilots is expensive, for this reason internationally, ground training with respect to particular aircraft is being catered by flight simulators. For this reason, high-fidelity FDM is a concerning aspect. In line with the above, it is significantly necessary to train new pilots from a realistic approach, keeping in mind the existing piloting reviews from old fellows of that aircraft to adopt for a dynamically changing environment whether that be in terms of standard operating procedures (SOPs) of flight, systems, or navigation [2]. Moreover, the need of designing a realistic FDM for flight simulators can also reduce the amount of actual flight time pilots put on aircrafts by which fuel and CO2 emission can be saved. This effort will inline flight organizations to act according to the ICAO Programme of Action on International Aviation and Climate Change, which enforces the ways to save material cost, i.e., fuel economy, and protect the environment which are the key concerns [1] that can be a driving factor for designing flight simulators.

external side of the body. The aerodynamics concerned in this chapter is related to the external flow over an unknown aircraft body. CFD helps to simulate actual size of computer-aided design (CAD) model, in an enclosed control volume. Any property in the control volume is controlled using Reynolds transport theorem as shown in Eq. (1), and further this approach is applied on velocities over three-dimensional

*Development of the Flight Dynamic Model (FDM) Using Computational Fluid Dynamic (CFD)…*

*ρbdV* þ

Partial differential equations are used for describing system of fluids (i.e., gasses

The principle of mass balance is used in light of law of conservation of mass for

*dt* with derivation of density with time change and ∇ � ð Þ *ρ* � *v* is time rate

The momentum equations in the *x*-, *y*-, and *z*-axes, respectively, are expressed in

*∂x* þ *∂τxx ∂x* þ *∂τyx ∂y* þ *∂τzx ∂z*

*∂y* þ *∂τxy ∂x* þ *∂τyy ∂y* þ *∂τzy ∂z*

*∂z* þ *∂τxz ∂x* þ *∂τyz ∂y* þ *∂τzz ∂z*

þ ∇ � *ρ e* þ

k *∂T ∂y* � �

> *<sup>∂</sup>*ð Þ *<sup>u</sup>τxx ∂x*

þ

The energy equations used were derived from Navier-Stokes which depends upon the first law of thermodynamics [6]. The derivation for conservation of energy on a finite fluid element consists of a single equation which is expressed in Eq. (5).

> þ *∂ ∂z*

þ

þ

*∂ vτzy* � � *∂z*

*V*2 2 � �*<sup>V</sup>* � �

> *∂ uτyx* � � *∂y*

k *∂T ∂z* � �

*<sup>∂</sup>*ð Þ *<sup>w</sup>τxz ∂x*

þ

¼ *ρq*\_

� *<sup>∂</sup>*ð Þ *up ∂x*

*<sup>∂</sup>*ð Þ *<sup>u</sup>τzx ∂z*

> *∂ wτyz* � � *∂y*

þ

ð

*ρb***V** � **n**^*dA* (1)

þ *ρfx*

þ *ρfy*

(4)

(5)

þ *ρfz*

*dt* <sup>þ</sup> <sup>∇</sup> � ð Þ¼ *<sup>ρ</sup>* � *<sup>v</sup>* <sup>0</sup> (3)

*<sup>∂</sup><sup>t</sup>* (2)

*cs*

space and time using Eulerian technique as shown in Eq. (2):

*cv*

*∂u ∂x* þ *v ∂u ∂y* þ *w ∂u ∂z* þ *∂u*

*∂ρ*

<sup>þ</sup> <sup>∇</sup> � ð Þ¼� *<sup>ρ</sup>uV <sup>∂</sup><sup>p</sup>*

<sup>þ</sup> <sup>∇</sup> � ð Þ¼� *<sup>ρ</sup>vV <sup>∂</sup><sup>p</sup>*

<sup>þ</sup> <sup>∇</sup> � ð Þ¼� *<sup>ρ</sup>wV <sup>∂</sup><sup>p</sup>*

and liquids) that are represented by the general laws of conservation of mass,

*DBsys Dt* <sup>¼</sup> *<sup>∂</sup> ∂t* ð

*DOI: http://dx.doi.org/10.5772/intechopen.91895*

*Du Dt* <sup>¼</sup> *<sup>u</sup>*

momentum, and energy [4].

where *<sup>∂</sup><sup>ρ</sup>*

Eq. (4).

fluid element, and it is written in Eq. (3) [5].

of change of volume of moving fluid.

*<sup>∂</sup>*ð Þ *<sup>ρ</sup><sup>u</sup> ∂t*

*<sup>∂</sup>*ð Þ *<sup>ρ</sup><sup>v</sup> ∂t*

*<sup>∂</sup>*ð Þ *<sup>ρ</sup><sup>w</sup> ∂t*

*∂*

þ *∂ ∂x*

þ

þ

**147**

*<sup>∂</sup><sup>t</sup> <sup>ρ</sup> <sup>e</sup>* <sup>þ</sup>

� *<sup>∂</sup>*ð Þ *vp*

*∂ vτxy* � � *∂x*

*<sup>∂</sup>*ð Þ *<sup>w</sup>τzz ∂z*

*V*2 2 � � � �

> þ *∂ ∂y*

*∂ vτyy* � � *∂y*

þ *ρf* � *V*

k *∂T ∂x* � �

*<sup>∂</sup><sup>y</sup>* � *<sup>∂</sup>*ð Þ *wp ∂z* þ

þ
