Sea-unammned aerial vehicle takeoff characteristics analysis method based on approximate equilibrium hypothesis

2018 ◽  
Vol 233 (3) ◽  
pp. 916-927 ◽  
Author(s):  
Dongli Ma ◽  
Zhi Li ◽  
Muqing Yang ◽  
Yang Guo ◽  
Haode Hu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Unmanned Aerial Vehicle ◽  
Interpolation Method ◽  
Design Stage ◽  
Approximate Equilibrium ◽  
Characteristics Analysis ◽  
Aerial Vehicle ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

In this paper, transient multiphase flow computational fluid dynamics simulations based on volume of fluid model are conducted for a sea-unmanned aerial vehicle. The approximate equilibrium hypothesis is implemented after estimating the acceleration in the vertical direction. The complete configuration model and hull model are employed in simulation to predict the aerodynamic and hydrodynamic forces separately for different demands of aerodynamic and hydrodynamic computational fluid dynamics predictions and computing efficiency. In takeoff characteristics analysis, the computational fluid dynamics simulations are conducted as inputs for piecewise interpolation method. The calculated results show that the sea-unmanned aerial vehicle takeoff characteristics are totally different from a conventional aircraft. The drag-peak at hump speed is the obvious feature of the sea-unmanned aerial vehicle/seaplane. In most cases, if a sea-unmanned aerial vehicle will takeoff successfully as long as it can pass the drag peak. The takeoff distance and time calculated by piecewise interpolation method match the experimental data within 7% deviation. The accuracy is acceptable for conceptual design stage of a sea-unmanned aerial vehicle/seaplane. The results are applicable to consultation in choosing takeoff field or choosing powerplant.

A computational fluid dynamics investigation of subsonic wing designs for unmanned aerial vehicle application

2019 ◽  
Vol 233 (15) ◽  
pp. 5543-5552
Author(s):  
Z Siddiqi ◽  
JW Lee
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Aspect Ratio ◽  
Unmanned Aerial Vehicle ◽  
Wing Design ◽  
Ansys Fluent ◽  
High Lift ◽  
Aerial Vehicle ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The wing of an unmanned aerial vehicle, RQ-7 Shadow, is modified to study the changes in the aerodynamics of the wing. The main focus is to investigate the effects of changing the components of wing design when the aircraft climbs and accelerates. These component modifications included changing the airfoil, planform, aspect ratio, and adding a winglet. Another objective is to study the efficacy of employing high-lift airfoils like the EPPLER 559 for subsonic unmanned aerial vehicle applications. For this, five wing designs are considered in this paper. Computational fluid dynamics simulations using ANSYS FLUENT® are conducted for each wing design. The C L /C D ratios for all the wings are calculated at increasing angles of attack (simulating Climbing) and increasing speed (simulating Acceleration). Compared to the NACA 4415 airfoil, which is utilized by the RQ-7 Shadow, the EPPLER 559 provides an increase in lift at the low angles of attack, but yields less of these benefits as the angle of attack increases. The tapered planform significantly reduces the high drag associated with the EPPLER 559 airfoil. The generation of higher lift forces with lower drag is further achieved by increasing the aspect ratio and through the addition of a winglet. When compared to the NACA 4415 airfoil, it is concluded that the EPPLER 559 airfoil is a viable candidate for subsonic unmanned aerial vehicle applications only when the components of wing design are altered. The performance of the wings that employ the EPPLER 559 airfoil improves when the planform is changed from rectangular to tapered, when the aspect ratio is increased and when a winglet is added.

A computational fluid dynamics study on the solid mineral particles-laden flow in a novel offshore agitated vessel

2018 ◽  
Vol 233 (2) ◽  
pp. 622-631
Author(s):  
D Yang ◽  
XQ Lv ◽  
YL Xiong
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Scale ◽  
Design Stage ◽  
Technical Equipment ◽  
Multiphase Model ◽  
Agitated Vessel ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Offshore Mining

Most seabeds are unexplored and rich in mineral deposits, making offshore mining a promising activity. However, offshore operation brings in great challenges from technical equipment to physical space. For instance, an offshore agitated vessel is supposed to stabilize the solids concentration from the underwater mining and make little impact on the stability of the platform or ship. For this reason, we proposed a novel offshore agitated vessel. The whole system based on the arrangement of the mineral processing platform and the slurry mix flow rate is obtained from the previous design stage. Large-scale unsteady computational fluid dynamics simulations are performed to calculate its effectiveness. The simulation model equipped with two pitched blade turbines and inlets/outlets is investigated. A classical Eulerian multiphase model and a modification of the standard k-ε eddy-viscosity turbulence model are adopted to simulate the dense solid–liquid suspension dynamics. Computational fluid dynamics results were found to be in satisfactory agreement with the theoretical predictions. The agitated system obtained was found to be effective to stabilize the solid particle concentration. In order to achieve a higher concentration at outlets and lower power consumption, further improvement was made and validated by computational fluid dynamics simulations. The proposed offshore mechanical agitated vessel could be equipped on offshore mining.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

scholarly journals Evaluation of Active Heat Sinks Design under Forced Convection—Effect of Geometric and Boundary Parameters

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2041
Author(s):  
Eva C. Silva ◽  
Álvaro M. Sampaio ◽  
António J. Pontes
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Additive Manufacturing ◽  
Pressure Drop ◽  
Forced Convection ◽  
Thermal Performance ◽  
Heat Sinks ◽  
Trapezoidal Shape ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

This study shows the performance of heat sinks (HS) with different designs under forced convection, varying geometric and boundary parameters, via computational fluid dynamics simulations. Initially, a complete and detailed analysis of the thermal performance of various conventional HS designs was taken. Afterwards, HS designs were modified following some additive manufacturing approaches. The HS performance was compared by measuring their temperatures and pressure drop after 15 s. Smaller diameters/thicknesses and larger fins/pins spacing provided better results. For fins HS, the use of radial fins, with an inverted trapezoidal shape and with larger holes was advantageous. Regarding pins HS, the best option contemplated circular pins in combination with frontal holes in their structure. Additionally, lattice HS, only possible to be produced by additive manufacturing, was also studied. Lower temperatures were obtained with a hexagon unit cell. Lastly, a comparison between the best HS in each category showed a lower thermal resistance for lattice HS. Despite the increase of at least 38% in pressure drop, a consequence of its frontal area, the temperature was 26% and 56% lower when compared to conventional pins and fins HS, respectively, and 9% and 28% lower when compared to the best pins and best fins of this study.

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