In this study, a computational fluid dynamics approach based on solving the Reynolds-averaged Navier-Stokes equation and shear stress transport (SST) (Menter) k-ω turbulence model is used to solve ...

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2021.1917454

The influence of the blade tip shape on brownout by an approach based on computational fluid dynamics

Effect of tracks on the flow and heat transfer of supersonic evacuated tube maglev transportation

Analysis of the expanding process of turbulent separation bubble on an iced airfoil under stall conditions

Stall characteristics analyses and stall lift robustness inverse design for high-lift devices of a wide-body commercial aircraft

\n Geared contra-rotating open rotors have the potential to further reduce fuel consumption relative to geared turbofans, but require a more-complex speed-reducing transmission system to drive the propellers. Hitherto, the preliminary design for such transmission systems has been reported independently of the overall engine modeling or has been limited by many predetermined engine constraints. This has restricted the feasible design space of the transmission systems. A simple transmissions preliminary design approach is needed that does not involve complicated mechanical assessments and can be integrated with engine preliminary design studies. This paper presents a novel design framework for sizing a double-helical differential planetary gearbox for a contra-rotating open rotor. An up-to-date methodology is proposed for the design of maximum load capacity gears for this application based on the power-transmitted, durability, and space envelope requirements. The methodology was validated with published data, demonstrating only very minor differences in geometry dimensions. Parametric analyses have been made to assess the impact of the design assumptions on gearbox dimensions. The framework also enables the identification of feasible torque ratios between the output shafts of the speed-reducer and the contra-rotating propellers driven by them. The impact of the torque ratio on the size of the gearbox has been analyzed for equal propeller rotational speeds and different speed ratios between the output shafts. This study shows that potential torque ratios lie between 1.1 and 1.33, with the higher ratios enabling more compact gearboxes having four or five planet gears.

Preliminary design framework for the power gearbox in a contra-rotating open rotor

Numerical investigations on drag reduction of a civil light helicopter fuselage

High efficiency and low fuel consumption make the contrarotating open rotor (CROR) system a viable economic and environmentally friendly powerplant for future aircraft. While the potential benefits are well accepted, concerns still exist with respect to the vibrations and noise caused by the aerodynamic interactions of CROR systems. In this paper, emphasis is placed on the detailed analysis of the aerodynamic interactions between the front and aft propellers of a puller CROR configuration. For the first step, unsteady Reynolds-averaged Navier-Stokes (URANS) simulations coupled with dynamic patched grid technology are implemented on the isolated single-rotating propeller (SRP) configuration in various operating conditions in order to test the accuracy and feasibility of the numerical approach. The numerical results are verified by a wind tunnel test, showing good agreements with the experimental data. Subsequently, the URANS approach is applied to the CROR configuration. The numerical results obtained through the URANS approach help to improve the understanding of the complex flow field generated by the CROR configuration, and the comparison of SRP flow field and CROR flow field allows for a detailed analysis of the aerodynamic interactions of the front propeller blade wakes and tip vortices with the aft propeller. The main reason of the aerodynamic interactions is the mutual effects of the blade tip vortices, and the aft propeller reduces the strength of the blade tip vortices of the front propeller. Aerodynamic interactions will lead to the periodic oscillations of the aerodynamic forces, and the frequency of the oscillations is linked to the blade numbers. In addition, a CROR has a larger thrust and power coefficient than that of the SRP configuration in the same operating conditions. The URANS approach coupled with a dynamic patched grid method is tested to be an efficient and accurate tool in the analysis of propeller aerodynamic interactions.

/pdf/cfd-analysis-of-contrarotating-open-rotor-aerodynamic-26990aiiwi.pdf

CFD Analysis of Contrarotating Open Rotor Aerodynamic Interactions

In order to simplify the manufacturing process or because of the limitation of the propulsion system, business jet, small civil airplane, and turboprop aircraft are always designed without leading-edge slats, which poses a great challenge to the flight safety during takeoff and landing. Focusing on the low-speed stall and poststall conditions, we investigated the aerodynamic characteristics and flow mechanism of high-lift configuration without slats using an improved delayed detached eddy simulation (IDDES) model which is validated by numerical simulations of the Common Research Model (CRM). Based on the analysis of the calculated results, conclusion can be made that the stall behavior of the configurations is directly related to the onset and evaluation of flow separation on the suction side. And through further research, an efficient evaluation method that is capable of qualitatively predicting the stall performance of two-element high-lift configuration by stall angle distribution of wing sections is proposed. By using the evaluation method, together with design rules summarized from the present study, high-lift configuration with mild-stall characteristic can be obtained in the preliminary stage of design.

/pdf/investigation-and-improvement-of-stall-characteristic-of-j9aw2brp5b.pdf

Investigation and Improvement of Stall Characteristic of High-Lift Configuration without Slats

The coupled problem of aerodynamic heating and structural heat transfer occupies a very important position in the field of aerospace engineering applications because it directly affects the...

Behaviors of Hypersonic Wing under Aerodynamic Heating

Aeroelastic deformation of the high-aspect-ratio wing from a solar-powered UAV will definitely lead to the difference of its performance between design and actual flight. In the present study, the numerical fluid-structural coupling analysis of a wing with skin flexibility is performed by a loosely coupled partitioned approach. The bidirectional coupling framework is established by combining an in-house developed computational fluid dynamics (CFD) code with a computational structural dynamics (CSD) analysis solver and a time-adaptive coupling strategy is integrated in it to improve the computational stability and efficiency of the process. With the proposed method, the fluid-structure interactions between the wing and fluid are simulated, and the results are compared between the deformed wing and its rigid counterpart regarding the aerodynamic coefficients, transition location, and flow structures at large angles of attack. It can be observed that after deformation, the laminar transition on the upper surface is triggered earlier at small angles of attack and the stall characteristic becomes worse. The calculated difference in aerodynamic performance between the deformed and the designed rigid wing can help designers better understand the wing’s real performance in the preliminary stage of design.

/pdf/numerical-aeroelastic-analysis-of-a-high-aspect-ratio-wing-3qggacfz.pdf

Zhao Yang

Papers

Numerical investigations on drag reduction of a civil light helicopter fuselage

CFD Analysis of Contrarotating Open Rotor Aerodynamic Interactions

Investigation and Improvement of Stall Characteristic of High-Lift Configuration without Slats

Behaviors of Hypersonic Wing under Aerodynamic Heating

Numerical Aeroelastic Analysis of a High-Aspect-Ratio Wing Considering Skin Flexibility