Numerical exploration on drag and heat reduction mechanism of a spike-tipped supersonic blunt nose

2020 ◽  
Vol 34 (32) ◽  
pp. 2050370
Author(s):  
Yu-Shan Meng ◽  
Li Yan ◽  
Shi-Bin Li ◽  
Wei Huang
Keyword(s):  
Heat Flux ◽  
Drag Force ◽  
Stokes Equations ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Viscous Force ◽  
Reduction Mechanism ◽  
Complex Flow ◽  
Drag Ratio ◽  
Lift To Drag Ratio

In this study, the drag force and heat flux reduction mechanism induced by the aerodisk (with disks on its nose) with the freestream Mach number being 4.937 has been numerically investigated, and the simulations have been carried out by the three-dimensional Reynolds-averaged Navier–Stokes equations coupled with the SST [Formula: see text] turbulence model. The influence of the angle of attack on the drag and heat flux reduction has been analyzed comprehensively. The obtained results show that the drag force of the spiked blunt body can be reduced by the aerodisk, and the drag force decreases by 24.63%. The flow mechanism of the complex flow is drastically modified by the angle of attack, and this results in a strong flow asymmetry. This asymmetry becomes more and more obvious as the angle of attack increases. Both the pressure force and viscous force increase with the increase of the angle of attack. Moreover, both the lift and drag coefficients increase as the angle of attack increases, and the lift-to-drag ratio increases first and then decreases with the increase of the angle of attack. When the angle of attack is [Formula: see text], the maximum lift-to-drag ratio is close to 0.36.

Taper stacking for the aerodynamic performance of wings

2020 ◽  
Vol 92 (7) ◽  
pp. 1101-1110
Author(s):  
Mustafa Kaya ◽  
Munir Ali Elfarra
Keyword(s):  
Mach Number ◽  
Drag Force ◽  
Angle Of Attack ◽  
Total Drag ◽  
Content Type ◽  
Critical Mach Number ◽  
Wing Sweep ◽  
Drag Ratio ◽  
First Time ◽  
Lift To Drag Ratio

Purpose The critical Mach number, lift-to-drag ratio and drag force play important role in the performance of the wings. This paper aims to investigate the effect of taper stacking, which has been used to generalize wing sweeping, on those parameters. Design/methodology/approach The results obtained are based on steady-state turbulent flowfields computations. The baseline wing is ONERA M6. Various wing planforms are generated by linearly or parabolically varying the spanwise stacking location. The critical Mach number is determined by changing the freestream Mach number for a fixed angle of attack. On the other hand, the analysis of the drag force is carried out by changing the angle of attack to keep the lift force constant. Findings By changing the stacking location, the critical Mach number and the corresponding lift-to-drag ratio have increased by around 7 and 3%, respectively. A reduction of 12.8% in total drag force has been observed in one of the analyzed cases. Moreover, there exist some cases in which the values of drag reduce significantly while the lift is the same. Practical implications The results of this new stacking approach have implied that the drag force can be decreased without decreasing the lift. This outcome is valuable for increasing the range and endurance of an aircraft. Originality/value This work generalizes wing sweeping by modifying the taper stacking along the span. In literature, wing sweep is enhanced using segmented stacking of taper distribution. The present study is further enhancing this concept by introducing continuous stacking (infinite number of stacking segments) for the first time.

scholarly journals THE EFFECTS OF ANGLE OF ATTACK, REYNOLD NUMBERS AND WINGLET STRUCTURE ON THE PERFORMANCE OF CESSNA 172 SKYHAWK

2018 ◽  
Vol 10 (1) ◽  
pp. 61
Author(s):  
Henny Pratiwi
Keyword(s):  
Wind Tunnel ◽  
Drag Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Balsa Wood ◽  
Wingtip Vortex ◽  
The One ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This research aims to investigate the effects of angle of attack, Reynold numbers and winglet structure on the performance of Cessna 172 Skyhawk aircraft with winglets variation design. Winglets improve efficiency by diffusing the shed wingtip vortex, which reducing the drag due to lift and improving the wing’s lift over drag ratio. In this research, the specimens are the duplicated of Cesnna 172 Skyhawk wing with 1:40 ratio made of balsa wood. There are three different winglet designs that are compared with the one without winglet. The experiments are conducted in an open wind tunnel to measure the lift and drag force with Reynold numbers of 25,000 and 33,000. It can be concluded that the wings with winglets have higher lift coefficient than wing without winglet for both Reynold numbers. It was also found that all wings with winglets have higher lift-to-drag ratio than wings without winglet where the blended 45o cant angle has the highest value.

scholarly journals Optimal design of nose and tail of an autonomous underwater vehicle hull to reduce drag force using numerical simulation

2019 ◽  
Vol 234 (1) ◽  
pp. 76-88 ◽  
Author(s):  
Mohammad Saghafi ◽  
Roham Lavimi
Keyword(s):  
Energy Consumption ◽  
Drag Force ◽  
Autonomous Underwater Vehicle ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Autonomous Underwater Vehicles ◽  
Three Dimensional ◽  
Underwater Vehicle ◽  
Underwater Vehicles ◽  
Navier Stokes

In this research, the flow around the autonomous underwater vehicles with symmetrical bodies is numerically investigated. Increasing the drag force in autonomous underwater vehicles increases the energy consumption and decreases the duration of underwater exploration and operations. Therefore, the main objective of this research is to decrease drag force with the change in geometry to reduce energy consumption. In this study, the decreasing or increasing trends of the drag force of axisymmetric bare hulls have been studied by making alterations in the curve equations and creating the optimal geometric shapes in terms of hydrodynamics for the noses and tails of autonomous underwater vehicles. The incompressible, three-dimensional, and steady Navier–Stokes equations have been used to simulate the flow. Also, k-ε Realizable with enhanced wall treatment was used for turbulence modeling. Validation results were acceptable with respect to the 3.6% and 1.4% difference with numerical and experimental results. The results showed that all the autonomous underwater vehicle hulls designed in this study, at an attack angle of 0°, had a lower drag force than the autonomous underwater vehicle hull used for validation except geometry no. 1. In addition, nose no. 3 has been selected as the best nose according to the lowest value of stagnation pressure, and also tail no. 3 has been chosen as the best tail due to the production of the lowest vortex. Therefore, geometry no. 5 has been designed using nose and tail no. 3. The comparison made here showed that the maximum drag reduction in geometry no. 5 was equal to 26%, and therefore, it has been selected as the best bare hull in terms of hydrodynamics.

scholarly journals Aerodynamic and Vibration Characteristics of the Micro-Octocopter at Low Reynolds Number

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xiaohua Zou ◽  
Mingsheng Ling ◽  
Wenzheng Zhai
Keyword(s):  
Reynolds Number ◽  
Load Capacity ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Vibration Characteristics ◽  
Low Reynolds ◽  
Vibration Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

With the development of flight technology, the need for stable aerodynamic and vibration performance of the aircraft in the civil and military fields has gradually increased. In this case, the requirements for aerodynamic and vibration characteristics of the aircraft have also been strengthened. The existing four-rotor aircraft carries limited airborne equipment and payload, while the current eight-rotor aircraft adopts a plane layout. The size of the propeller is generally fixed, including the load capacity. The upper and lower tower layout analyzed in this paper can effectively solve the problems of insufficient four-axis load and unstable aerodynamic and vibration performance of the existing eight-axis aircraft. This paper takes the miniature octorotor as the research object and studies the aerodynamic characteristics of the miniature octorotor at different low Reynolds numbers, different air pressures and thicknesses, and the lift coefficient and lift-to-drag ratio, as well as the vibration under different elastic moduli and air pressure characteristics. The research algorithm adopted in this paper is the numerical method of fluid-solid cohesion and the control equation of flow field analysis. The research results show that, with the increase in the Reynolds number within a certain range, the aerodynamic characteristics of the miniature octorotor gradually become better. When the elastic modulus is 2.5 E, the aircraft’s specific performance is that the lift increases, the critical angle of attack increases, the drag decreases, the lift-to-drag ratio increases significantly, and the angle of attack decreases. However, the transition position of the flow around the airfoil surface is getting closer to the leading edge, and its state is more likely to transition from laminar flow to turbulent flow. When the unidirectional carbon fiber-reinforced thickness is 0.2 mm and the thin arc-shaped airfoil with the convex structure has a uniform thickness of 2.5% and a uniform curvature of 4.5%, the aerodynamic and vibration characteristics of the octorotor aircraft are most beneficial to flight.

Kinematics of diving Atlantic puffins (Fratercula arctica L.):evidence for an active upstroke

2002 ◽  
Vol 205 (3) ◽  
pp. 371-378
Author(s):  
L. Christoffer Johansson ◽  
Björn S. Wetterholm Aldrin
Keyword(s):  
Three Dimensional ◽  
Fratercula Arctica ◽  
Induced Drag ◽  
Video Images ◽  
Hand Bones ◽  
On Line ◽  
Oscillating Motion ◽  
Drag Ratio ◽  
Wing Tip ◽  
Lift To Drag Ratio

SUMMARY To examine the propulsion mechanism of diving Atlantic puffins (Fratercula arctica), their three-dimensional kinematics was investigated by digital analysis of sequential video images of dorsal and lateral views. During the dives of this wing-propelled bird, the wings are partly folded, with the handwings directed backwards. The wings go through an oscillating motion in which the joint between the radius-ulna and the hand bones leads the motion, with the wing tip following. There is a large rotary motion of the wings during the stroke, with the wings being pronated at the beginning of the downstroke and supinated at the end of the downstroke/beginning of the upstroke. Calculated instantaneous velocities and accelerations of the bodies of the birds show that, during the downstroke, the birds accelerate upwards and forwards. During the upstroke, the birds accelerate downwards and, in some sequences analysed, also forwards, but in most cases the birds decelerate. In all the upstrokes analysed, the forward/backward acceleration shows the same pattern, with a reduced deceleration or even a forward acceleration during ‘mid’ upstroke indicating the production of a forward force, thrust. Our results show that the Atlantic puffin can use an active upstroke during diving, in contradiction to previous data. Furthermore, we suggest that the partly folded wings of diving puffins might act as efficient aft-swept wingtips, reducing the induced drag and increasing the lift-to-drag ratio. A movie is available on-line.

scholarly journals A Multi-GPU Parallel Algorithm in Hypersonic Flow Computations

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jianqi Lai ◽  
Hua Li ◽  
Zhengyu Tian ◽  
Ye Zhang
Keyword(s):  
Parallel Algorithm ◽  
Hypersonic Flow ◽  
Stokes Equations ◽  
Programming Model ◽  
Graphics Processing Unit ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Time Discretization ◽  
Processing Unit ◽  
Complex Flow

Computational fluid dynamics (CFD) plays an important role in the optimal design of aircraft and the analysis of complex flow mechanisms in the aerospace domain. The graphics processing unit (GPU) has a strong floating-point operation capability and a high memory bandwidth in data parallelism, which brings great opportunities for CFD. A cell-centred finite volume method is applied to solve three-dimensional compressible Navier–Stokes equations on structured meshes with an upwind AUSM+UP numerical scheme for space discretization, and four-stage Runge–Kutta method is used for time discretization. Compute unified device architecture (CUDA) is used as a parallel computing platform and programming model for GPUs, which reduces the complexity of programming. The main purpose of this paper is to design an extremely efficient multi-GPU parallel algorithm based on MPI+CUDA to study the hypersonic flow characteristics. Solutions of hypersonic flow over an aerospace plane model are provided at different Mach numbers. The agreement between numerical computations and experimental measurements is favourable. Acceleration performance of the parallel platform is studied with single GPU, two GPUs, and four GPUs. For single GPU implementation, the speedup reaches 63 for the coarser mesh and 78 for the finest mesh. GPUs are better suited for compute-intensive tasks than traditional CPUs. For multi-GPU parallelization, the speedup of four GPUs reaches 77 for the coarser mesh and 147 for the finest mesh; this is far greater than the acceleration achieved by single GPU and two GPUs. It is prospective to apply the multi-GPU parallel algorithm to hypersonic flow computations.

scholarly journals Study of board bending degree on hydrodynamic performances of a single-layer cambered otter-board

2019 ◽  
Vol 131 ◽  
pp. 01120
Author(s):  
Lei Wang ◽  
Lu Min Wang ◽  
Yong Li Liu ◽  
Wen Wen Yu ◽  
Guang Rui Qi ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Single Layer ◽  
Moment Coefficient ◽  
Pitch Moment ◽  
Engineering Models ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The effect of board bending degree on hydrodynamic performances of a single-layer cambered otter-board was investigated using engineering models in a wind tunnel. Three different bending degree boards were evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp , over a range of angle of attack (0° to 70°). These coefficients were used in analyzing the differences in the performance among the three otter-board models. Results showed that the bending of the board(No. 2, No. 3) increased the water resistance of the otter-board, and improved the lift coefficient of the otter-board in the small angle of attack (0°<α≤20 °) ; the maximum lift coefficients Cy of otter-board model (No. 1) was higher (1.680, α = 25°). the maximum lift–drag ratios of models (No. 1, No. 2 and No. 3) are 6.822 (α = 7.5 °), 6.533 (α = 2.5 °) and 6.384 (α = 5.0°), which showed that the board bending reduces the lift-to-drag ratio of the otter-board.The stability of the No. 3 model was better than those two models (No. 1, No. 2) in most range of attack angle, but No. 1 otter-board model had a better stability in roll of otter-board. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling.

Drag force on a liquid domain moving inside a membrane sheet surrounded by aqueous medium

2015 ◽  
Vol 779 ◽  
pp. 468-482 ◽  
Author(s):  
V. Laxminarsimha Rao ◽  
Sovan Lal Das
Keyword(s):  
Drag Force ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Domain Size ◽  
Bilayer Membrane ◽  
Fredholm Integral Equations ◽  
Two Dimensional ◽  
Liquid Domain ◽  
Viscosity Contrast ◽  
Surrounding Membrane

We compute the drag on a circular and liquid microdomain diffusing in a two-dimensional fluid lipid bilayer membrane surrounded by a fluid above and below. Under the assumptions that the liquids are incompressible and the flow is of low Reynolds number, Stokes’ equations describe the flow in the two-dimensional membrane as well as in the surrounding three-dimensional fluid. The expression for the drag force on the liquid domain involves Fredholm integral equations of the second kind, which we numerically solve using discrete collocation method based on Chebyshev polynomials. We observe that when the domain is more viscous than the surrounding membrane (including the rigid domain case), the drag force is almost independent of the viscosity contrast between the domain and the surrounding membrane, as also observed earlier in experiments by other researchers. The mobility also varies logarithmically with Boussinesq number${\it\beta}$for large${\it\beta}$. On the other hand, for a less viscous domain the dimensionless drag force reduces with increasing viscosity contrast, and a significant change in the drag force, from that when there is no viscosity contrast or when the domain is rigid, has been observed. Further, the logarithmic behaviour of the mobility no longer holds for less viscous domains. Our method of computing the drag force and diffusion coefficient is valid for arbitrary viscosity contrast between the domain and membrane and any domain size (subject to${\it\beta}\geqslant 5$).

Control of shock-induced vortex breakdown on a delta-wing-body configuration in the transonic regime

2021 ◽  
pp. 1-25
Author(s):  
Rajan B. Kurade ◽  
L. Venkatakrishnan ◽  
G. Jagadeesh
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Pressure Fluctuations ◽  
Angle Of Attack ◽  
Aerodynamic Coefficients ◽  
Delta Wings ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Sudden Jump ◽  
Modest Level

Abstract Shock-induced vortex breakdown, which occurs on the delta wings at transonic speed, causes a sudden and significant change in the aerodynamic coefficients at a moderate angle-of-attack. Wind-tunnel tests show a sudden jump in the aerodynamic coefficients such as lift force, pitching moment and centre of pressure which affect the longitudinal stability and controllability of the vehicle. A pneumatic jet operated at sonic condition blown spanwise and along the vortex core over a 60° swept delta-wing-body configuration is found to be effective in postponing this phenomenon by energising the vortical structure, pushing the vortex breakdown location downstream. The study reports that a modest level of spanwise blowing enhances the lift by about 6 to 9% and lift-to-drag ratio by about 4 to 9%, depending on the free-stream transonic Mach number, and extends the usable angle-of-attack range by 2°. The blowing is found to reduce the magnitude of unsteady pressure fluctuations by 8% to 20% in the aft portion of the wing, depending upon the method of blowing. Detailed investigations carried out on the location of blowing reveal that the blowing close to the apex of the wing maximises the benefits.

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