# A Novel Reverse Hinge Spoiler for Flight Loads Control

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## Abstract

**:**

## 1. Introduction

## 2. The Reverse Spoiler Concept

## 3. Computational Fluid Dynamics

#### 3.1. The Mathematical Model

_{𝑖}and 𝑢

_{𝑗}are the time-averaged velocity components, respectively; 𝜌 is the density of the fluid; and $P=p+\left(2/3\right)\rho k$, where $p$ is the time-averaged pressure, $k$ is the turbulent kinetic energy, 𝜇 is the dynamic viscosity of the fluid, and ${\mu}_{t}$is the turbulent or eddy viscosity of the fluid. The equations describing the turbulence kinetic energy$k$ and its specific rate of dissipation $\omega $ for the k-omega SST turbulence model are as follows [23]:

#### 3.2. Spoiler Variables

- Non-Dimensional Spoiler Length, L/C;
- Non-Dimensional Hinge Location of the Spoiler, X/C;
- Spoiler Deflection, θ (relative to a tangent drawn on the airfoil surface).

**13, 14, and 15 degrees**). The angles of attack highlighted in bold are the region where stall occurs; hence, convergence in these areas was of greater difficulty. It should be noted that the operating range for the spoilers is usually below these angles.

#### 3.3. Geometry

#### 3.4. Mesh Generation and Boundary Conditions

#### 3.5. Grid Independence and Verification Analysis

#### Grid Uncertainty Analysis

#### 3.6. Validation

#### 3.6.1. Clean NACA0012 CFD Results Validation with XFOIL

#### 3.6.2. NACA 2412 with a Conventional Spoiler CFD Validation by Experiment

## 4. Conventional vs. Reverse Hinge Spoilers—Performance Analysis

#### 4.1. Effect of Spoiler Hinge Location

#### Flow-Field Analysis

#### 4.2. Effect of Spoiler Deflection

#### 4.3. Effect of Spoiler Length

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 7.**Final mesh of the NACA2412 airfoil–spoiler used in this validation study, with a refinement region around the spoiler and wake.

**Figure 8.**Comparison of pressure coefficients of NACA 2412 (with conventional spoiler) with experimental data [16] at different angles of attack.

**Figure 9.**Effect of spoiler hinge location on the lift coefficient for a conventional and reverse spoiler at a 60-degree spoiler deflection and spoiler length of 0.15C.

**Figure 10.**Effect of spoiler hinge location on the drag coefficient for a conventional and reverse spoiler at a 60-degree spoiler deflection and spoiler length of 0.15C.

**Figure 11.**Pressure coefficients for the conventional and reverse spoilers at locations 0.6C and 0.7C for 0- and 12-degrees angle of attacks, and a deflection angle of 60 degrees.

**Figure 12.**Static pressure contours of the reverse spoiler at hinge positions 0.6C and 0.7C, for a 60-degree deflection angle and 0- and 12-degree angles of attack.

**Figure 13.**Velocity magnitude contour of the reverse spoiler at hinge positions 0.6C and 0.7C, for a 60-degree deflection angle and 0- and 12-degree angles of attack.

**Figure 14.**Velocity vectors around a reverse spoiler at hinge positions 0.6C and 0.7C, for a 60-degree deflection angle and 0- and 12-degree angle of attacks.

**Figure 15.**Pressure distribution comparison between the conventional and the reverse spoiler at a hinge position of 0.6C, a 60-degree deflection angle, and a 6-degree angle of attack.

**Figure 16.**Static pressure contours for the conventional and reverse spoilers at a 0.6C hinge position, 60-degree deflection angle, and 6-degree angle of attack.

**Figure 17.**Effect of spoiler hinge location on the lift coefficient for a conventional and reverse spoiler at a 25-degree spoiler deflection and spoiler length of 0.15C.

**Figure 18.**Effect of spoiler hinge location on the drag coefficient for a conventional and reverse spoiler at a 25-degree spoiler deflection and spoiler length of 0.15C.

**Figure 19.**Lift/drag polar for a representative spoiler configuration, showing the effect of spoiler deflection for the conventional (

**top**) and reverse (

**bottom**) spoiler.

**Figure 20.**Difference in lift and drag coefficients compared to a clean airfoil for both spoiler types varying with spoiler deflection (0-degree AOA).

**Figure 21.**Change in lift and drag coefficients compared to a clean airfoil varying with spoiler deflection at a 6-degree AOA (

**top**) and 12-degree AOA (

**bottom**).

**Figure 22.**Pressure distributions upon varying spoiler deflection for the conventional spoiler at a 0-degree AOA.

**Figure 23.**Pressure Distributions upon varying spoiler deflection for the reverse spoiler at a 0-degree AOA.

**Figure 24.**Pressure distribution comparison at moderate spoiler angles (15° and 25°) for both spoiler types (conventional and reverse) (

**top**) and the static pressure contour plots for conventional and reverse spoilers (

**middle**&

**bottom**ones) at a 15-degree spoiler angle and AOA = 0 degrees, respectively.

**Figure 25.**Pressure distributions of both spoiler types with a 15-degree spoiler deflection at a 6-degree AOA (

**top**) and 12-degree AOA (

**bottom**).

**Figure 26.**Effect of spoiler length on the conventional and reverse spoilers at a 25-degree spoiler deflection angle.

**Figure 27.**Pressure distribution comparing the effect of spoiler length on the conventional and reverse spoiler.

Variable | Values |
---|---|

Spoiler deflection ($\theta )$ | 0, 5, 15, 25, 60, and 90 |

Length of spoiler | 0.1 and 0.15 |

Hinge location (X/C) | 0.6 and 0.7 |

Cell Count | CL Percentage | CD Percentage | Difference in CL % | Difference in CD % |
---|---|---|---|---|

282,992 291,743 298,834 312,457 328,078 | 0.3702 0.3661 0.3620 0.3597 0.3596 | 0.1155 0.1170 0.1184 0.1191 0.1192 | 1.14 1.12 0.63 0.019 | 1.27 1.13 0.62 0.059 |

Validation Case | Re | # of Cells | Average y+ |
---|---|---|---|

NACA0012 NACA2412 with Conventional spoiler | 166023 783761 | 272014 296104 | 1.2 0.8 |

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**MDPI and ACS Style**

Ajaj, R.M.; Djidjeli, K.
A Novel Reverse Hinge Spoiler for Flight Loads Control. *Designs* **2022**, *6*, 92.
https://doi.org/10.3390/designs6050092

**AMA Style**

Ajaj RM, Djidjeli K.
A Novel Reverse Hinge Spoiler for Flight Loads Control. *Designs*. 2022; 6(5):92.
https://doi.org/10.3390/designs6050092

**Chicago/Turabian Style**

Ajaj, Rafic M., and Kamal Djidjeli.
2022. "A Novel Reverse Hinge Spoiler for Flight Loads Control" *Designs* 6, no. 5: 92.
https://doi.org/10.3390/designs6050092