**Fluid Dynamics Analysis of a Space Vehicle Entering the Mars Atmosphere**

Antonio Viviani1 and Giuseppe Pezzella2 *1Seconda Università degli Studi di Napoli, Aversa 2Centro Italiano Ricerche Aerospaziali, Capua Italy* 

### **1. Introduction**

62 Applied Computational Fluid Dynamics

Vera, S.; Fazio, P. & Rao, J. (2010a). Interzonal air and moisture transport through large

Vera, S.; Fazio, P. & Rao, J. (2010b). Interzonal air and moisture transport through large

*and Environment* No. 45, pp. 622–631.

*Building and Environment*, No. 45, pp. 1192–1201.

horizontal openings in a full-scale two-story test-hut: part 2 – CFD study. *Building* 

horizontal openings in a full-scale two-story test-hut: part 1 – experimental study.

This paper reports the results of design analyses of two Manned Braking Systems (MBS) entering the Mars atmosphere, with the aim of supporting design studies of a planetary entry system. Two lifting body configurations with rounded edge delta-like cross section have been analyzed. The preliminary aerodynamic and aerothermodynamic analyses have considered flight conditions compatible with a manned mission entering the Mars atmosphere. However, neither the mission architecture needed to reach Mars from Earth or neighbour Earth space, nor surface exploration have been addressed.

All the design analyses have been performed at several levels. Indeed, vehicle aerodynamic assessment has been extensively addressed through simplified design approach as, e.g., hypersonic panel methods (HPM); then, a number of fully three-dimensional computational fluid dynamics (CFD) simulations, both with Euler and Navier-Stokes approximations, of the hypersonic flowfield past the entry vehicle have been performed.

The results herein provided have been obtained for a Mars entry scenario compliant with an approach to the red planet both by direct planetary entry and entry after aerobraking (Polishchuk et al., 2006) (Viviani and Pezzella, 2009). These results may be used to provide numerical data for understanding requirements for the human exploration of Mars.

### **2. Computational flowfield analysis**

CFD analyses have been performed to assess the aerothermal environment that the MBS experiments during descent, thus evaluating several surface loading distributions (e.g., pressure and heat flux). To this aim, several fully three-dimensional numerical computations, both for perfect and chemically reacting gas approximation, have been performed.

The vehicle configurations, under investigation in this work, are shown in Fig. 1 These lifting bodies feature an aerodynamic configuration with a compact body about 8 [m] long with a rounded edge delta-like cross section (Hanley et al., 1964). A very preliminary internal layout for a crew of four astronauts is also reported in Fig. 1.

Fluid Dynamics Analysis of a Space Vehicle Entering the Mars Atmosphere 65

different angles of attack () have been investigated and compared each other. The Fluent code together with user defined functions (UDFs), developed in order to simulate mixtures of gas in thermo-chemical non-equilibrium, have been used for CFD computations with a non-equilibrium chemical model suitable for Martian atmosphere (Gupta et al., 1996) (Mack

For the reacting gas computations, the Martian atmosphere has been considered as a mixture of 95.7% carbon-dioxide, 1.6% Argon and 2.7% nitrogen. The flow has been modelled as a reacting gas mixture of 9 species (Ar, CO2, N2, O2, CO, NO, N, O, C) involved in the chemical reactions of Table 2 (Park et al., 1994) (Anderson, 1989). The reaction mechanism and the related chemical kinetics, taken into account in the present work, are summarized in Table 2, where M is the reacting partner (third body) that can be any of the

Non-equilibrium computations have been performed since one of the most challenging problem facing the design of atmospheric entry vehicle is the phenomenon of "real gas behaviour". At hypersonic speeds, the shock wave produced ahead of the vehicle suddenly elevates the gas temperature in the shock layer. So the gas thermal energy may be comparable with the energy associated with a whole range of gas chemical processes such as: molecular vibrational excitation; dissociation of atmospheric molecules into their atomic forms; formation of other chemical species through recombination reactions; and ionisation

et al., 2008) (Kustova et al., 2009).

nine reacting species of the gas mixture.

*C2+M* 

*NCO+M* 

of both molecular and atomic species (Park et al., 1994).

Reaction Third Body

Table 2. Reactions mechanism and rate parameters (Park et al., 1994).

M

*CO M CO O M* <sup>2</sup> *CO2,CO,N2,O2,NO* **6.9x1021 -1.5 63275**

*CO M C O M CO2,CO,N2,O2,NO* **2.3x1020 -1.0 129000**

*N M NNM* <sup>2</sup> *CO2,CO,N2,O2,NO* **7.0x1021 -1.6 113200**

*O M OOM* <sup>2</sup> *CO2,CO,N2,O2,NO* **2.0x1021 -1.5 59750**

*NO M N O M CO2,C,N,O,NO* **1.1x1017 0.0 75500**

*Ar* **6.9x1020**  *C,N,O* **1.4x1022**

*Ar* **2.3x1019**  *C,N,O* **3.4x1020** 

*Ar* **7.0x1021**  *C,N,O* **3.0x1022** 

*Ar* **3.0x1021**  *C,N,O* **3.0x1022** 

*Ar* **5.0x1015**  *CO,N2,O2* **5.0x1015** 

 *C+C+M All* **2.0x1021 -1.5 59750**

 *CO+N+M All* **6.3x1016 -0.5 24000** *NO O N O* <sup>2</sup> **8.4x1012 0.0 19450** *N O NO N* <sup>2</sup> **6.4x1017 -1.0 38370** *CO O C O* <sup>2</sup> **3.9x1013 -0.18 69200** *CO O CO O* 2 2 **2.1x1013 0.00 27800**

**Ar** *[cm3 mol-1s -1]* **<sup>r</sup>** *Td* **[K]**

Fig. 1. Vehicle configurations with quotes.

### **2.1 Freestream conditions**

The flight scenario considered so far is summarized in Table 1. They refer to entry conditions compatible with a vehicle entering the Mars atmosphere both from a hyperbolic orbit (HO), e.g., direct planetary entry, and an elliptic orbit (EO) e.g., planetary entry after aerobraking (Gupta et al., 1996).


EO PH (Elliptic Orbit Peak Heating) HO PH (Hyperbolic Orbit Peak Heating) NCW (Non-Catalytic Wall) FCW (Fully Catalytic Wall)

Table 1. CFD freestream conditions

Therefore, thirteen CFD numerical simulations have been performed. As one can see, CFD computations (both Euler and Navier-Stokes) have been performed, both in trajectory-based and space-based design approaches (Hanley et al., 1964). Several Mach numbers and

The flight scenario considered so far is summarized in Table 1. They refer to entry conditions compatible with a vehicle entering the Mars atmosphere both from a hyperbolic orbit (HO), e.g., direct planetary entry, and an elliptic orbit (EO) e.g., planetary entry after

> Mach AoA Altitude [-] [deg] [km] 10 10 10.0 15 40 60.0 22 40 60.0

10 10 10.0 10 20 10.0 10 30 10.0 10 40 10.0

EO PH 22 40 44.2 HO PH 26 40 52.1

NCW 22 40 44.2 FCW 22 40 44.2 NCW 26 40 52.1 FCW 26 40 52.1

Therefore, thirteen CFD numerical simulations have been performed. As one can see, CFD computations (both Euler and Navier-Stokes) have been performed, both in trajectory-based and space-based design approaches (Hanley et al., 1964). Several Mach numbers and

EO PH (Elliptic Orbit Peak Heating) HO PH (Hyperbolic Orbit Peak Heating)

NCW (Non-Catalytic Wall) FCW (Fully Catalytic Wall)

HO PH

EO PH

Perfect Gas

Reacting Gas

Fig. 1. Vehicle configurations with quotes.

**2.1 Freestream conditions** 

aerobraking (Gupta et al., 1996).

Table 1. CFD freestream conditions

different angles of attack () have been investigated and compared each other. The Fluent code together with user defined functions (UDFs), developed in order to simulate mixtures of gas in thermo-chemical non-equilibrium, have been used for CFD computations with a non-equilibrium chemical model suitable for Martian atmosphere (Gupta et al., 1996) (Mack et al., 2008) (Kustova et al., 2009).

For the reacting gas computations, the Martian atmosphere has been considered as a mixture of 95.7% carbon-dioxide, 1.6% Argon and 2.7% nitrogen. The flow has been modelled as a reacting gas mixture of 9 species (Ar, CO2, N2, O2, CO, NO, N, O, C) involved in the chemical reactions of Table 2 (Park et al., 1994) (Anderson, 1989). The reaction mechanism and the related chemical kinetics, taken into account in the present work, are summarized in Table 2, where M is the reacting partner (third body) that can be any of the nine reacting species of the gas mixture.

Non-equilibrium computations have been performed since one of the most challenging problem facing the design of atmospheric entry vehicle is the phenomenon of "real gas behaviour". At hypersonic speeds, the shock wave produced ahead of the vehicle suddenly elevates the gas temperature in the shock layer. So the gas thermal energy may be comparable with the energy associated with a whole range of gas chemical processes such as: molecular vibrational excitation; dissociation of atmospheric molecules into their atomic forms; formation of other chemical species through recombination reactions; and ionisation of both molecular and atomic species (Park et al., 1994).


Table 2. Reactions mechanism and rate parameters (Park et al., 1994).

Fluid Dynamics Analysis of a Space Vehicle Entering the Mars Atmosphere 67

the vehicle surface and pitch plane. Grid refinement in strong gradient regions of flowfield

The preliminary results of CFD simulations performed so far are summarized hereinafter. For example, Fig. 6 shows the static temperature contours on the vehicle symmetry plane and static pressure contours on vehicle surface at M=20 and =20 deg, considering the Mars atmosphere as a reacting gas mixture. As shown, the MBS bow shock structure around

 Fig. 4. Results for M=20 and =20 deg. (Left) static temperature field on vehicle symmetry plane; (right) static pressure contour on vehicle surface for non-equilibrium reacting gas

At the same flight conditions, Fig. 5 reports on chemical dissociation of the flow in the shock layer considering the contours of CO2 mass fraction on MBS pitch plane. As a consequence, flow dissociation determines a large density ratio across the strong bow shock compared with a flow of the same gas where no dissociation takes place (Viviani and Pezzella, 2009) (Anderson, 1989). This results in a thinner shock layer around the entry vehicle (e.g., lower

Fig. 3. Example of computational mesh domains for Euler CFD simulations

has been made through a solution adaptive approach.

the descent vehicle can be appreciated as well.

stand-off distance).

Therefore, the gas mixture has to be considered in thermal and chemical non-equilibrium. Finally, the CFD analysis of the MBS have been preceded by a code validation phase performed considering the available numerical and experimental data for the Mars Pathfinder probe at entry peak heating conditions, as summarized in (Viviani et al., 2010) (Gnoffo et al., 1998) (Gnoffo et al., 1996) (Mitcheltree et al., 1995).

#### **2.2 Numerical results**

The aerodynamic analysis of MBS is shown in term of lift (CL), drag (CD) and pitching moment (CMy) coefficients which are calculated according to Eq. (1) and Eq. (2), respectively.

$$\mathbf{C}\_{i} = \frac{F\_{i}}{\frac{1}{2}\rho\_{\alpha}v\_{\alpha}^{2}} \quad \text{i} = L\_{\text{\textdegree}}D \tag{1}$$

$$C\_{Mj} = \frac{M\_j}{\frac{1}{2}\rho\_\alpha v\_\alpha^2 L\_{\text{ref}} S\_{\text{ref}}} \quad j = Y \tag{2}$$

The reference parameters Lref (e.g., longitudinal reference length) and Sref (e.g., reference surface) are the vehicle length (e.g., 8 m) and planform area (e.g., 32 m2). The pitching moment is computed from the vehicle nose (i.e. 0, 0, 0). Engineering based aerodynamic analysis has been extensively performed by using a 3D Panel Methods code developed by CIRA, namely HPM (Viviani and Pezzella, 2009). This tool, at high supersonic and hypersonic speeds, is able to accomplish the aerodynamic and aerothermodynamic analyses of a complex re-entry vehicle configuration by using simplified approaches as local surface inclination methods and approximate boundary-layer methods, respectively. The SIM typical of hypersonics are based on Newtonian, Modified Newtonian, and Prandtl-Mayer theories (Anderson, 1989). Typical surface meshes of the MBS, used for the engineering level computations, are shown in Fig. 2.

Fig. 2. Example of panel mesh for engineering-based aerodynamic analysis.

MBS aerodynamic results, provided by engineering-based analysis, cover ranging from 0 to 50 deg. Present CFD computations for the MBS have been carried out on a 3-D multiblock structured grid close to that shown in Fig. 3. The grid consists of about 20 blocks and 900.000 cells (half body). Both computational domains are tailored for the free-stream conditions of Table 1. The distribution of surface grid points has been dictated by the level of resolution desired in various areas of the vehicle such as the stagnation region and the base fillet one, according to the computational scopes. Fig. 3 shows also a close-up view of the 3-D mesh on

Therefore, the gas mixture has to be considered in thermal and chemical non-equilibrium. Finally, the CFD analysis of the MBS have been preceded by a code validation phase performed considering the available numerical and experimental data for the Mars Pathfinder probe at entry peak heating conditions, as summarized in (Viviani et al., 2010)

The aerodynamic analysis of MBS is shown in term of lift (CL), drag (CD) and pitching moment (CMy) coefficients which are calculated according to Eq. (1) and Eq. (2), respectively.

> 2 , <sup>1</sup>

*ref <sup>F</sup> <sup>C</sup> i LD*

*j*

The reference parameters Lref (e.g., longitudinal reference length) and Sref (e.g., reference surface) are the vehicle length (e.g., 8 m) and planform area (e.g., 32 m2). The pitching moment is computed from the vehicle nose (i.e. 0, 0, 0). Engineering based aerodynamic analysis has been extensively performed by using a 3D Panel Methods code developed by CIRA, namely HPM (Viviani and Pezzella, 2009). This tool, at high supersonic and hypersonic speeds, is able to accomplish the aerodynamic and aerothermodynamic analyses of a complex re-entry vehicle configuration by using simplified approaches as local surface inclination methods and approximate boundary-layer methods, respectively. The SIM typical of hypersonics are based on Newtonian, Modified Newtonian, and Prandtl-Mayer theories (Anderson, 1989). Typical surface meshes of the MBS, used for the engineering level

*M C j Y*

*ref ref*

(1)

(2)

*i*

2

*v S*

1 <sup>2</sup> 2

*vL S*

Fig. 2. Example of panel mesh for engineering-based aerodynamic analysis.

MBS aerodynamic results, provided by engineering-based analysis, cover ranging from 0 to 50 deg. Present CFD computations for the MBS have been carried out on a 3-D multiblock structured grid close to that shown in Fig. 3. The grid consists of about 20 blocks and 900.000 cells (half body). Both computational domains are tailored for the free-stream conditions of Table 1. The distribution of surface grid points has been dictated by the level of resolution desired in various areas of the vehicle such as the stagnation region and the base fillet one, according to the computational scopes. Fig. 3 shows also a close-up view of the 3-D mesh on

*i*

*M j*

(Gnoffo et al., 1998) (Gnoffo et al., 1996) (Mitcheltree et al., 1995).

**2.2 Numerical results** 

computations, are shown in Fig. 2.

the vehicle surface and pitch plane. Grid refinement in strong gradient regions of flowfield has been made through a solution adaptive approach.

Fig. 3. Example of computational mesh domains for Euler CFD simulations

The preliminary results of CFD simulations performed so far are summarized hereinafter. For example, Fig. 6 shows the static temperature contours on the vehicle symmetry plane and static pressure contours on vehicle surface at M=20 and =20 deg, considering the Mars atmosphere as a reacting gas mixture. As shown, the MBS bow shock structure around the descent vehicle can be appreciated as well.

Fig. 4. Results for M=20 and =20 deg. (Left) static temperature field on vehicle symmetry plane; (right) static pressure contour on vehicle surface for non-equilibrium reacting gas

At the same flight conditions, Fig. 5 reports on chemical dissociation of the flow in the shock layer considering the contours of CO2 mass fraction on MBS pitch plane. As a consequence, flow dissociation determines a large density ratio across the strong bow shock compared with a flow of the same gas where no dissociation takes place (Viviani and Pezzella, 2009) (Anderson, 1989). This results in a thinner shock layer around the entry vehicle (e.g., lower stand-off distance).

Fluid Dynamics Analysis of a Space Vehicle Entering the Mars Atmosphere 69

Fig. 7. CL and CD versus . Comparison between panel methods and CFD results for perfect

As one can see, engineering and numerical data compare very well, thus confirming that engineering-based estimations represent reliable preliminary aerodynamics of a Mars entry vehicle. Moreover, real gas effects increase the aerodynamic drag coefficient whereas the lift

As far as CFD results for the second configuration are concerned, Fig. 8 shows the Mach number contour field that takes place around the vehicle when it is flying at the peak

In particular, the left side of Fig. 8 shows the Mach contour field on the vehicle pitch plane while at the right side of Fig. 8 gives an idea of the bow shock shape that envelopes the

As shown, a thin shock layer envelopes the entry vehicle windside with a strong expansion

Fig. 8. Mach contours on the vehicle pitch plane and three flowfield cross sections at the

heating conditions of entry by EO (e.g., M=22, =40 deg, and H=44.20 km).

that characterizes the flow at the end of the vehicle.

vehicle since the Mach field is reported on three different flowfield cross sections.

and reacting gas approximations.

is only slightly influenced.

EOPH conditions.

Under conditions where dissociation exists, the aerodynamics of vehicle depends primarily on shock density ratio. In fact, the change of aerodynamic characteristics is the result of change in surface pressure acting on the vehicle forebody (Gnoffo et al., 1998) (Viviani et al., 2010).

Fig. 5. Results for M=20 and =20 deg. Contours of CO2 mass fraction

Moreover, Fig. 6 shows CFD results for M=21 and =40 deg. The left side reports pressure coefficient contours (Cp) on vehicle surface and on two cross sections; whereas on the right Cp contours on vehicle surface and Mach number contours on three cross sections have been shown.

Fig. 6. Results for M=21 and =40 deg. (Left) pressure coefficient contours (Cp) on vehicle surface and on two cross sections; (right) Cp contours on vehicle surface and Mach number contours on three cross sections

The curves of lift and drag coefficients are shown in Fig. 7. Those curves collect MBS aerodynamic coefficients compared with available numerical data both for perfect gas and reacting gas approximations, reported in order to highlight accuracy of both numerical and engineering-based results (Viviani et al., 2010).

Under conditions where dissociation exists, the aerodynamics of vehicle depends primarily on shock density ratio. In fact, the change of aerodynamic characteristics is the result of change in surface pressure acting on the vehicle forebody (Gnoffo et al., 1998)

Moreover, Fig. 6 shows CFD results for M=21 and =40 deg. The left side reports pressure coefficient contours (Cp) on vehicle surface and on two cross sections; whereas on the right Cp contours on vehicle surface and Mach number contours on three cross sections have been

Fig. 6. Results for M=21 and =40 deg. (Left) pressure coefficient contours (Cp) on vehicle surface and on two cross sections; (right) Cp contours on vehicle surface and Mach number

The curves of lift and drag coefficients are shown in Fig. 7. Those curves collect MBS aerodynamic coefficients compared with available numerical data both for perfect gas and reacting gas approximations, reported in order to highlight accuracy of both numerical and

Fig. 5. Results for M=20 and =20 deg. Contours of CO2 mass fraction

(Viviani et al., 2010).

shown.

contours on three cross sections

engineering-based results (Viviani et al., 2010).

Fig. 7. CL and CD versus . Comparison between panel methods and CFD results for perfect and reacting gas approximations.

As one can see, engineering and numerical data compare very well, thus confirming that engineering-based estimations represent reliable preliminary aerodynamics of a Mars entry vehicle. Moreover, real gas effects increase the aerodynamic drag coefficient whereas the lift is only slightly influenced.

As far as CFD results for the second configuration are concerned, Fig. 8 shows the Mach number contour field that takes place around the vehicle when it is flying at the peak heating conditions of entry by EO (e.g., M=22, =40 deg, and H=44.20 km).

In particular, the left side of Fig. 8 shows the Mach contour field on the vehicle pitch plane while at the right side of Fig. 8 gives an idea of the bow shock shape that envelopes the vehicle since the Mach field is reported on three different flowfield cross sections.

As shown, a thin shock layer envelopes the entry vehicle windside with a strong expansion that characterizes the flow at the end of the vehicle.

Fig. 8. Mach contours on the vehicle pitch plane and three flowfield cross sections at the EOPH conditions.

Fluid Dynamics Analysis of a Space Vehicle Entering the Mars Atmosphere 71

Finally, the curves of lift, drag, and pitching moment coefficients are shown in Fig. 11. Real gas effects increase both drag and pitching moment coefficients, whereas the lift is only

slightly influenced. Vehicle aerodynamics is also summarized in the table of Fig. 11.

Fig. 11. Lift, Drag and pitching moment coefficients versus . Comparison between panel

The paper deals with the flowfield analysis of two braking systems for manned exploration

A number of fully 3D Navier-Stokes and Euler CFD computations of the hypersonic flowfield past two lifting body vehicles have been performed for several freestream conditions of a proposed Mars entry loading environment. These evaluations have been aimed at carrying out only a preliminary design of the MBS configuration, in compliance

The range between Mach 2 and Mach 26 has been analyzed, to provide both aerodynamic databases according to both the space-based and trajectory-based design approaches. Numerical results show that real gas effects increase both the aerodynamic drag and

methods and CFD results for perfect and non-equilibrium gas computations.

pitching moment coefficient, whereas the lift is only slightly influenced.

**3. Conclusion** 

mission to Mars.

with the Phase-A design level.

The CO mass fraction field around the vehicle for the same freestream conditions is shown in Fig. 9 where some streamtraces colored by Mach number are also reported.

Fig. 9. CO mass fraction at the EOPH conditions on three cross sections with streamtraces colored by Mach number

As shown the CO concentration reaches its maximum value close to the body. Fig. 10 shows the temperature comparison among non-equilibrium flow (right side of pilot) and perfect gas computation, evaluated at three flowfield cross sections (x=1.5 [m], 5.5 [m] and 9.5 [m]). It is clearly evident how real gas phenomena affect the vehicle shock layer, thus confirming all the conclusions highlighted before.

Fig. 10. Temperature comparison between non-equilibrium flow (right side of pilot) and perfect gas computation at x=1.5 [m], 5.5 [m] and 9.5 [m] flowfield cross sections

Finally, the curves of lift, drag, and pitching moment coefficients are shown in Fig. 11. Real gas effects increase both drag and pitching moment coefficients, whereas the lift is only slightly influenced. Vehicle aerodynamics is also summarized in the table of Fig. 11.

Fig. 11. Lift, Drag and pitching moment coefficients versus . Comparison between panel methods and CFD results for perfect and non-equilibrium gas computations.

### **3. Conclusion**

70 Applied Computational Fluid Dynamics

The CO mass fraction field around the vehicle for the same freestream conditions is shown

Fig. 9. CO mass fraction at the EOPH conditions on three cross sections with streamtraces

Fig. 10. Temperature comparison between non-equilibrium flow (right side of pilot) and

perfect gas computation at x=1.5 [m], 5.5 [m] and 9.5 [m] flowfield cross sections

1

2

As shown the CO concentration reaches its maximum value close to the body. Fig. 10 shows the temperature comparison among non-equilibrium flow (right side of pilot) and perfect gas computation, evaluated at three flowfield cross sections (x=1.5 [m], 5.5 [m] and 9.5 [m]). It is clearly evident how real gas phenomena affect the vehicle shock layer, thus confirming

colored by Mach number

all the conclusions highlighted before.

in Fig. 9 where some streamtraces colored by Mach number are also reported.

The paper deals with the flowfield analysis of two braking systems for manned exploration mission to Mars.

A number of fully 3D Navier-Stokes and Euler CFD computations of the hypersonic flowfield past two lifting body vehicles have been performed for several freestream conditions of a proposed Mars entry loading environment. These evaluations have been aimed at carrying out only a preliminary design of the MBS configuration, in compliance with the Phase-A design level.

The range between Mach 2 and Mach 26 has been analyzed, to provide both aerodynamic databases according to both the space-based and trajectory-based design approaches. Numerical results show that real gas effects increase both the aerodynamic drag and pitching moment coefficient, whereas the lift is only slightly influenced.

**5**

**Air Movement Within Enclosed Road-Objects** 

Accidents in closed-space traffic object do force for further investigation of a flow phenomena – that might be a consequence of such large-scale events. Benefit that almost directly would be coming out of this investigative approach is an optimal method for artificial ventilation, that must find mirroring in a annual statistics on covered roads[1, 2]. For such an investigative task, Computational Fluid Dynamics, the CFD offers ever stronger growing engineering tool. Once[3] passing through it´s first sophisticated developments[4], the zone-model approach was not capable for solving the problems like those were treated by the field models for CFD-research. Generally, field-models are based on the full solution of the fundamental physical laws of energy-conservation, where the computational domain of explored large-scale phenomenon is divided in thousands of smaller control volumes; where mathematical mechanism after it´s discretization are "translated" into programmesteps for computer handling. Today[5, 6], the CFD-society enjoys this software-development that started in 1960-ies and was certainly followed by the hardware development between mid ´80-s and mid ´90-s. Together, this computational mechanism [7-11] both hardware and software, can cope with computational domains with few thousands cells offering very satisfying results [1, 12] were accomplished attempts are done in both validating and exploring area of CFD. Modern field-model codes engaged in CFD-research, supported by today´s powerful hardware, can cope with domains made out of several hundred thousands cells. Some computational codes[13] applied for tunnel-fires, are taking in account simple one-step chemistry for combustion modelling, and the reaction rate is won from a the eddy break-up mixing model[14]. This approach is suitable for turbulent diffusion flames as well – one of a characteristic of large-scale fires, where the rate of reaction is controlled by a mixing of fuel with oxidant (air). In such a step, solved would be (the time-averaged[15]), turbulence-modelled conservation-equations for mass, momentum, energy and species of combustion. The *k-ε* turbulence model with extra source terms accounting for the effect of

**1. Introduction** 

**with Contra-Traffica CFD-Investigation** 

M. Muhasilovic1,2, A. Mededovic1,

*<sup>1</sup>IPSA-Institute Sarajevo, Sarajevo* 

*1Bosnia and Herzegovina* 

*2Germany 3Czech Republic*

E. Gacanin1, K. Ciahotny3 and V. Koza3

*<sup>3</sup>The VSCHT – Institute for Chemical Technology, Prague* 

*<sup>2</sup>The CIM-Collaboration Program of the GiZ German International Technology Agency* 

#### **4. References**

