# New Aerodynamic Studies of an Adaptive Winglet Application on the Regional Jet CRJ700

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

_{2}) emissions into the atmosphere over the past several years [1,2], the aerospace sector has to limit its figures in the near future [3,4]. For that, some solutions are available, such as working on trajectories optimization [5,6,7,8,9,10] or improving aircraft models to design reliable flight simulators [11,12,13,14]. It has been shown that trajectory optimization can save up to 2% of the cost of flights. Moreover, the use of reliable flight simulators could replace real flights related to pilot training or aircraft launch (certification, optimizations, etc.) and, consequently, could also help to reduce CO

_{2}emissions. To complement these efforts, solutions involving the optimization of aircraft geometry could also be interesting.

#### 1.1. Literature Review: Aircraft Geometry Improvement

#### 1.2. Paper Objectives

## 2. Methodology: Adaptive Winglet Analysis

#### 2.1. Adaptive Winglet Design

^{2}, its length is 1.372 m, and its maximum diameter is 0.173 m. It was designed to allow enough space inside of the pod to install a gear mechanism or a similar actuation device, as in the case of the Boeing 777X winglet motion. Given that this study is targeted at aerodynamic analysis and, further, performance benefits, the hypothesis that this pod could accommodate an adequate mechanism using current technology was made.

#### 2.2. Presentation of the Aerodynamic Model

#### 2.2.1. Mesh Design

^{3}(1 × 1 × 1 m). Then, the snappyHexMesh (SHM) tool was used to produce the aircraft integration (i.e., the aircraft shape defined using the STL file) in the “background mesh”. In order to perfectly smooth the wall of the plane, SHM use an algorithm that made refinement, smoothing, and re-alignment treatments using several techniques, such as chimera technics and curvilinear mesh [53,54]. The SHM algorithm performs mesh re-arrangement until the mesh quality criteria have been reached. In this study, the maximum non-orthogonality was set to 65, and the maximum skewness was set to 5. The refinement near wall was set using three layers measuring a maximum of 8.5 mm in total. The first layer, the closest to the wall, did not exceed 1.55 mm.

^{6}cells, and they showed a y+ value between 100 and 200, which has been considered as a “medium” mesh.

#### 2.2.2. Simulation Settings

#### 2.2.3. Validation of the CRJ700 Aerodynamic Model

#### 2.3. Comparison of the Original and the Adaptive Winglet Designs of the CRJ700

#### 2.3.1. Geometric Comparison

#### 2.3.2. Aerodynamic Comparison

^{6}cells for validations cases and using approximatively 11.12 × 10

^{6}cells for adaptive cases (equipped with the pod). Therefore, it seems that the “pod” designed in order to integrate the adaptive winglet was not linked to a degradation of the mesh qualities, which is very favorable to pursue the study.

#### 2.4. Aerodynamic Simulations

#### 2.4.1. Aerodynamic Simulations for Specific Winglet Deflection Angles

#### 2.4.2. Continuity Study

^{2}to 1 (R

^{2}> 0.96) were polynomial surfaces corresponding to a fourth order for the Mach number inputs and to a third order for the winglet deflection angle inputs. As a reminder, R is the correlation factor usually used in identification methods, such as linear regression [56].

## 3. Results

#### 3.1. Aerodynamic Benefits of an Adaptive Winglet

#### 3.2. Comparison of the Characteristics of the CRJ700 Equipped with Fixed versus Adaptive Winglets in Terms of Aerodynamic Polar and Pitching Moment

#### 3.3. Drag Improvement Summary

#### 3.4. Evolution of the Winglet Position during a Generic Cruise Profile

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 4.**Statistical analysis of errors obtained between the reference (VRESIM) and the validated aerodynamic model of the CRJ700 using OpenFoam. Residual errors are presented in terms of lift (

**a**), drag (

**b**), and pitching moment (

**c**) coefficients.

**Figure 5.**Superposition of the Computer-Aided-Design (CAD) of the original model and the new adaptive model of the CRJ700 aircraft.

**Figure 6.**Comparison of aerodynamic coefficients obtained using the aerodynamic model for the original and the adaptive winglet design of the CRJ700 Aircraft.

**Figure 7.**Lift and drag coefficients variations with the winglet deflection angle and Mach number for an angle of attack of 0 deg.

**Figure 8.**Pitching moment coefficient variation versus the winglet deflection angle and Mach number for an angle of attack of 0 deg.

**Figure 9.**Maximum and averaged lift benefits observed for different winglet deflection angles and different flight conditions.

**Figure 10.**Maximum and averaged drag benefits (reduction) observed for different winglet deflection angles and different flight conditions.

**Figure 11.**Maximum and averaged benefits observed on the lift-to-drag ratio for different winglet deflection angles and different flight conditions.

**Figure 12.**Aerodynamic polar (

**a**) and pitching moment coefficient (

**b**) comparison between a CRJ700 equipped with fixed and adaptive winglets at Mach number 0.31.

**Figure 13.**Aerodynamic polar (

**a**) and pitching moment coefficient (

**b**) comparison between a CRJ700 equipped with fixed and adaptive winglets at Mach number 0.45.

**Figure 14.**Aerodynamic polar (

**a**) and pitching moment coefficient (

**b**) comparison between a CRJ700 equipped with fixed and adaptive winglets at Mach number 0.54.

**Figure 15.**Aerodynamic polar (

**a**) and pitching moment coefficient (

**b**) comparison between a CRJ700 equipped with fixed and adaptive winglets at Mach number 0.66.

**Figure 16.**Aerodynamic polar (

**a**) and pitching moment coefficient (

**b**) comparison between a CRJ700 equipped with fixed and adaptive winglets at Mach number 0.79.

**Figure 17.**Drag benefits observed between the new aerodynamic polar (adaptive winglet) and the reference polar (fixed winglet).

**Figure 18.**Aerodynamic characteristics variation during a generic cruise mission at Mach number 0.5 (angle of attack variation from 4 deg to 1 deg).

**Figure 19.**Aerodynamic characteristics variations during a generic cruise mission at Mach number 0.75 (angle of attack variation from 1 deg to −1 deg).

Mesh Quality Parameters | Validated Model (no Pod) | New Model (with Pod) |
---|---|---|

Max. non-orthogonality (deg) | 65.060 | 65.020 |

Max. skewness | 5.0006 | 4.9925 |

Number of cells (×10^{6}) | 11.14 | 11.12 |

Altitude | Mach Number | Angle of Attack |
---|---|---|

5000 ft | M0.31 | −2 deg to +2 deg |

10,000 ft | M0.45 | −2 deg to +2 deg |

20,000 ft | M0.54 | −2 deg to +2 deg |

25,000 ft | M0.66 | −2 deg to +2 deg |

30,000 ft | M0.79 | −2 deg to +2 deg |

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**MDPI and ACS Style**

Segui, M.; Abel, F.R.; Botez, R.M.; Ceruti, A.
New Aerodynamic Studies of an Adaptive Winglet Application on the Regional Jet CRJ700. *Biomimetics* **2021**, *6*, 54.
https://doi.org/10.3390/biomimetics6040054

**AMA Style**

Segui M, Abel FR, Botez RM, Ceruti A.
New Aerodynamic Studies of an Adaptive Winglet Application on the Regional Jet CRJ700. *Biomimetics*. 2021; 6(4):54.
https://doi.org/10.3390/biomimetics6040054

**Chicago/Turabian Style**

Segui, Marine, Federico R. Abel, Ruxandra M. Botez, and Alessandro Ceruti.
2021. "New Aerodynamic Studies of an Adaptive Winglet Application on the Regional Jet CRJ700" *Biomimetics* 6, no. 4: 54.
https://doi.org/10.3390/biomimetics6040054