Evaluation of Assumed-Transition-Point Criterion in Context of Reynolds-Averaged Simulations Around Lighter-Than-Air Vehicles

et al. 2016

Journal of Aircraft

This paper presents an aerodynamic study of bodies related to lighter than air vehicles, using Computational Fluid Dynamics. The work begins with the validation of the CFD method using a 6:1 prolate spheroid. The validated method is then employed for the study of the flow around a shape similar to the Airlander aircraft of Hybrid Air Vehicles Ltd. An overview of the flow around is presented, supported by pressure survey, flow visualisation and transitional flow effects. The sensitivity of the transition location to the Reynolds number is also demonstrated, and the role of each component of the vehicle is analysed in terms of its effect on the flow-field, the lift and drag, and stability in pitch. It was found that the fins contributed the most to increase the lift and drag coefficients.

Section: Role Of the Components On The Loads And Pitch Stabilitymentioning

confidence: 99%

“…10 In addition, since the 'AL' is not axisymmetric, at zero pitch angle the pitching moment is not zero, which differs from more traditional airship configurations. 11,12,24,27 …”

Section: Role Of the Components On The Loads And Pitch Stabilitymentioning

confidence: 99%

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Analysis of Hybrid Air Vehicles Using Computational Fluid Dynamics

Carrion

Steijl

et al. 2016

Journal of Aircraft

“…Similar behavior was observed in other works in the literature that did not account for buoyancy e¨ects. This is the case of the experiments on the AKRON [40], YEZ-2A [41], and ZHIYUAN-1 [42,43] airships that also presented positive C Mα . Nevertheless, the presence of the aerodynamic components has a stabilizing e¨ect, since there is a reduction in the pitch derivative.…”

Section: Study Of the Role Of The Components On A Complete Hybrid Airmentioning

confidence: 80%

Computational fluid dynamics challenges for hybrid air vehicle applications

Biava

Steijl

Progress in Flight Physics

et al. 2017

This paper begins by comparing turbulence models for the prediction of hybrid air vehicle (HAV) §ows. A 6 : 1 prolate spheroid is employed for validation of the computational §uid dynamics (CFD) method. An analysis of turbulent quantities is presented and the Shear Stress Transport (SST) kω model is compared against a kω Explicit Algebraic Stress model (EASM) within the unsteady Reynolds-Averaged NavierStokes (RANS) framework. Further comparisons involve Scale Adaptative Simulation models and a local transition transport model. The results show that the §ow around the vehicle at low pitch angles is sensitive to transition e¨ects. At high pitch angles, the vortices generated on the suction side provide substantial lift augmentation and are better resolved by EASMs. The validated CFD method is employed for the §ow around a shape similar to the Airlander aircraft of Hybrid Air Vehicles Ltd. The sensitivity of the transition location to the Reynolds number is demonstrated and the role of each vehicle£s component is analyzed. It was found that the ¦ns contributed the most to increase the lift and drag.

“…This is due to the fact that substantial parts of the aerodynamic lift are generated at the forward part of the hull. Wind tunnel experiments on the AKRON [2], YEZ-2A [3] and ZHIYUAN-1 [4,5] airships are available in the literature. All of them presented static unstable behaviour, as the rigid models were employed and buoyancy was not accounted for.…”

mentioning

confidence: 99%

Study of Hybrid Air Vehicle Stability Using Computational Fluid Dynamics

Carrion

Biava

et al. 2017

Journal of Aircraft

This paper uses Computational Fluid Dynamics to predict aerodynamic damping of airships or hybrid air vehicles. This class of aircraft is characterised by large lifting bodies combining buoyancy and circulatory lift. Damping is investigated via forced oscillations of the vehicle in pitch and yaw. The employed method is verified using data for lighter than air vehicles. The use of fins and stabilisers was found to be beneficial. The rear part of the body was dominated by separated flow that contained more frequencies than the forcing frequency imposed on the body. The final design is seen to be dynamically stable across a range of conditions for small pitch angles.Nomenclaturė