# Air Flow Study around Isolated Cubical Building in the City of Athens under Various Climate Conditions

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Configuration and Pollutant Dispersion Modelling

#### 2.1. Problem Configuration

^{6}, based on the height of the cube and the free stream velocity. The specified flow field at the inlet of the computational domain is in the form of a logarithmic profile with the no-slip condition at the ground. A passive source of pollutants is located on the floor of the computational domain at a distance H from the rear surface of the building, using as a pollutant methane (CH

_{4}) gas with a concentration and release of 600 ppm and 18.5 L/h, respectively. The dimensionless concentration coefficient K of the passive pollutant is defined as [48,49]:

^{11}and 7.68 × 10

^{11}, respectively. Thus, the buoyancy forces are intensive and the boundary layers close to the heated surfaces are highly turbulent.

#### 2.2. Governing Equations

#### 2.3. Urban Surface Model (USM) of the PALM Model System

## 3. Initial and Boundary Conditions

## 4. Nested Computational Grid

## 5. Numerical Details

^{−4}value for each computed variable based on the error. The time step is automatically adjusted for the CFL constant value of 0.9.

_{x}/u

_{∞}, u

_{y}/u

_{∞}, u

_{z}/u

_{∞}), at the point with Cartesian coordinates of X: 10 H, Y: 5.5 H, and Z: 0.5 H and for the period from 600 to 1400 s for Scenario A.

## 6. Results and Discussion

**X**,

_{f}**X**, and

_{b}**X**are defined for the frontal, rear, and roof recirculation of the building, respectively.

_{r}**X**in front of the upstream surface of the building for Scenario A is 41% higher than the corresponding for Scenario B and 8.14% lower than Scenario C. In addition, the recirculation zone on the roof

_{f}**X**for Scenario A is 20.81% lower than the recirculation zone of Scenario B and 27.44% lower than for Scenario C. The recirculation zone in the wake region

_{r}**X**of the building for Scenario A is 13% lower than the corresponding recirculation zone of Scenario B and 23.28% lower than the recirculation zone for Scenario C.

_{b}## 7. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 6.**GCI error bars estimated from the fine to medium grids for Scenario A: (

**a**) for the normalized velocities u

_{x}/u

_{∞}and (

**b**) for the normalized concentration of the pollutant at the axial position of 0.5 H from the rear surface of the building.

**Figure 7.**Velocity fluctuations of u

_{x}/u

_{∞}, u

_{y}/u

_{∞}, u

_{z}/u

_{∞}at point X: 10 H, Y: 5.5 H, Z: 0.5 H from 600 up to 1400 (s) for Scenario A.

**Figure 8.**Concentration of the pollutant for Scenarios A and C at the position with coordinates of X: 7.5 H, Y: 5.5 H and Z: 0.5 H for the time period of 200 to 1000 (s).

**Figure 10.**Velocity streamlines of the mean flow field on the symmetry plane of the computational domain for Scenario A.

**Figure 11.**Normalized temperature profiles at the wake region of the flow for Scenario C, at X = 7 H and Y = 5.5 H, where $T$ is the mean temperature, ${T}_{a}$ is the ambient temperature, and ${T}_{f}$ is the temperature at the floor of the computational domain [41].

**Figure 12.**Temperature distribution on the vertical and horizontal surfaces of the building for the Scenario C along three different streamwise paths.

**Figure 13.**Vertical concentration profiles with the pollutant source at X = 7 H for Scenarios A and C at positions (

**a**) (X: 7 H, Y: 5.5 H), (

**b**) (X: 7.2 H, Y: 5.5 H), and (

**c**) (X: 7.4 H, Y: 5.5 H).

**Figure 14.**Concentration flux profiles that are due to the x−velocity component on the symmetry plane for Scenarios A and C at positions (

**a**) (X: 7 H, Y: 5.5 H), (

**b**) (X: 7.2 H, Y: 5.5 H), and (

**c**) (X: 7.4 H, Y: 5.5 H) for heights Z that extend from 0 to 2 H.

**Figure 15.**Distribution of the non-dimensional flux concentration at the z−component of the velocity on the symmetry plane for Scenarios A and C at positions (

**a**) (X: 7 H, Y: 5.5 H), (

**b**) (X: 7.2 H, Y: 5.5 H), and (

**c**) (X: 7.4 H, Y: 5.5 H) for height Z that extends from 0 to 2 H.

Averaging Period (s) | Mean Value | Variance | Autocovariance |
---|---|---|---|

600–800 | 1.0806 | 0.0473 | 0.3426 |

800–1000 | 1.0851 | 0.0538 | 0.3738 |

1000–1200 | 1.0879 | 0.0530 | 0.4316 |

1200–1400 | 1.0889 | 0.0524 | 0.4443 |

Averaging Period (s) | Mean Value | Variance | Autocovariance |
---|---|---|---|

200–400 | 0.2449 | 0.0186 | 0.9584 |

400–600 | 0.2445 | 0.0198 | 0.9532 |

600–800 | 0.2480 | 0.0193 | 0.9548 |

800–1000 | 0.2463 | 0.0195 | 0.9524 |

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**MDPI and ACS Style**

Pavlidis, C.L.; Palampigik, A.V.; Vasilopoulos, K.; Lekakis, I.C.; Sarris, I.E. Air Flow Study around Isolated Cubical Building in the City of Athens under Various Climate Conditions. *Appl. Sci.* **2022**, *12*, 3410.
https://doi.org/10.3390/app12073410

**AMA Style**

Pavlidis CL, Palampigik AV, Vasilopoulos K, Lekakis IC, Sarris IE. Air Flow Study around Isolated Cubical Building in the City of Athens under Various Climate Conditions. *Applied Sciences*. 2022; 12(7):3410.
https://doi.org/10.3390/app12073410

**Chicago/Turabian Style**

Pavlidis, Chariton L., Anargyros V. Palampigik, Konstantinos Vasilopoulos, Ioannis C. Lekakis, and Ioannis E. Sarris. 2022. "Air Flow Study around Isolated Cubical Building in the City of Athens under Various Climate Conditions" *Applied Sciences* 12, no. 7: 3410.
https://doi.org/10.3390/app12073410