Effect of aspect ratio variation on subsonic aerodynamics of cascade type grid fin at different gap-to-chord ratios

2019 ◽  
Vol 124 (1274) ◽  
pp. 472-498
Author(s):  
M. Tripathi ◽  
M.M. Sucheendran ◽  
A. Misra
Keyword(s):  
Aspect Ratio ◽  
Performance Enhancement ◽  
Aerodynamic Performance ◽  
Aerodynamic Efficiency ◽  
Grid Fin ◽  
Stall Angle ◽  
Control Surfaces ◽  
Cascade Type ◽  
Limiting Value ◽  
Selection Of

ABSTRACTThis paper dwells upon investigating the effect of aspect ratio (AR) variation on the aerodynamic performance of unconventional control surfaces called grid fins by virtue of a series of subsonic experiments on a simplified grid fin variant called the cascade fin. Wind tunnel tests were performed for different AR (variable span) grid fins. The same had been investigated for different gap-to-chord ratio (g/c) variants. Results demonstrated a tangible increase in the aerodynamic efficiency as well as stall angle reduction for higher AR. Moreover, higher AR leads to increased pitching moment, which emphasizes elevated hinge moment requirements. The study ensued the presence of higher deviation between the low AR fins, that is $AR<2$ compared to the pertinent deviations between the high AR fins, that is $AR\geq2$ . The effect associated with these variations was termed as span effect in this paper. It was established that, the deviations arising due to this phenomena were lesser for higher g/c and higher AR. The analysis of AR variation for different g/c presented a limiting value of AR reduction for stall performance enhancement. Thus, optimised selection of the g/c and AR values can lead to enhanced aerodynamic efficiency alongside an improved stalling characteristic.

Experimental analysis of cell pattern on grid fin aerodynamics in subsonic flow

2019 ◽  
Vol 234 (3) ◽  
pp. 537-562
Author(s):  
Manish Tripathi ◽  
Mahesh M Sucheendran ◽  
Ajay Misra
Keyword(s):  
Subsonic Flow ◽  
Lift Coefficient ◽  
Aerodynamic Performance ◽  
Aerodynamic Efficiency ◽  
Grid Fin ◽  
Stall Angle ◽  
The Individual ◽  
The Impact ◽  
Control Surfaces

Grid fins consisting of a lattice of high aspect ratio planar members encompassed by an outer frame are unconventional control surfaces used on numerous missiles and bombs due to their enhanced lifting characteristics at high angles of attack and across wider Mach number regimes. The current paper accomplishes and compares the effect of different grid fin patterns on subsonic flow aerodynamics of grid fins by virtue of the determination of their respective aerodynamic forces. Furthermore, this study deliberates the impact of gap variation on aerodynamics of different patterns. Results enunciate enhanced aerodynamic efficiency, and lift slope for web-fin cells and single diamond patterns compared to the baseline model. Moreover, the study indicates improved aerodynamic performance for diamond patterns with higher gaps by providing elevated maximum lift coefficient, delayed stall angle, and comparable drag at lower angles. The study established the presence of an additional effect termed as the inclination effect alongside the cascade effect leading to deviations with respect to lift, stall, and aerodynamic efficiency amongst different gap variants of the individual patterns. Thus, optimization based on the aerodynamic efficiency, stall angle requirements, and construction cost by optimum pattern and gap selection can be carried out through this analysis, which can lead to elevated aerodynamic performance for grid fins.

Flow Field Characterization and Visualization of Grid Fin Subsonic Flow

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Manish Tripathi ◽  
Mahesh M. Sucheendran ◽  
Ajay Misra
Keyword(s):  
Flow Field ◽  
Pressure Coefficient ◽  
Aerospace Applications ◽  
Planar Surfaces ◽  
Coefficient Distribution ◽  
Grid Fin ◽  
Layer Velocity ◽  
Stall Angle ◽  
High Mach ◽  
Control Surfaces

Grid fins are unconventional control surfaces consisting of an outer frame supporting an inner grid of intersecting planar surfaces. Although afflicted with higher drag, these have been credited for their enhanced lifting characteristics at high angles of attack and high Mach numbers, alongside reduced hinge moments accounting for the recent upsurge in their usage on numerous aerospace applications. Present investigations carry out elaborate flow field visualization and characterization underlining the rudimentary physics through a sequence of subsonic numerical simulations performed at different angles of attack and different gap (between the members) to chord ratios on a simplified grid fin variant called cascade fin. The study makes use of a new nondimensionalization technique called cumulative nondimensionalization to decipher the effect of cascading on individual members of the fin. Hence, after a comprehensive examination of the aerodynamic coefficients, pressure coefficient distribution, pressure gradient, velocity gradient, boundary layer velocity profile, and flow field visualization, the study elucidates physics associated with hastened stall angle, augmented lift-drag, and bounded efficiency accretion for gap increment.

On the aerodynamics of moult gaps in birds

1999 ◽  
Vol 202 (1) ◽  
pp. 67-76 ◽  
Author(s):  
A. Hedenström ◽  
S. Sunada
Keyword(s):  
Aspect Ratio ◽  
Detrimental Effect ◽  
Vortex Lattice ◽  
Aerodynamic Performance ◽  
Gap Size ◽  
Elliptical Distribution ◽  
Aerodynamic Efficiency ◽  
Lift Curve ◽  
Wing Moult ◽  
Wing Tip

During the moult, birds sequentially replace their flight feathers and thus temporarily have gaps in their wings. These gaps will vary in size and position(s) during the course of the moult. We investigated the aerodynamic effects of having moult gaps in a rectangular wing by using a vortex-lattice (panel) approach, and we modelled the effect of moult gap size at the wing moult initiation position, of gap position in the primary tract and of two simultaneous gaps (as occurs during secondary feather moulting in many birds). Both gap size and gap position had a detrimental effect on aerodynamic performance as measured by lift curve slope, effective aspect ratio and the aerodynamic efficiency of the wing. The effect was largest when the moult gap was well inside the wing, because the circulation declines close to the wing tip. In fact, when the gap was at the wing tip, the performance was slightly increased because the lift distribution then became closer to the optimal elliptical distribution. The detrimental effect of moult gaps increased with increasing aspect ratio, which could help to explain why large birds have relatively slow rates of moult associated with small gaps.

Comparative Evaluation of MoS2 and WS2 as Powder Lubricants in High Speed, Multi-Pad Journal Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 625-630 ◽  
Author(s):  
C. Fred Higgs ◽  
Crystal A. Heshmat ◽  
Hooshang Heshmat
Keyword(s):  
Comparative Evaluation ◽  
High Speed ◽  
Solid Lubricants ◽  
Extreme Environment ◽  
Journal Bearings ◽  
Lubricating Film ◽  
Constant Friction ◽  
Traction Coefficient ◽  
Limiting Value ◽  
Selection Of

As part of a program to develop solid/powder-lubricated journal bearings, a comparative evaluation has been performed to aid in determining whether MoS2 and WS2 powder are suitable lubricants for high-speed, extreme-environment multi-pad journal bearings. Plots of traction coefficients, friction, frictional power loss, and bearing pad temperature are presented as a means for comparing various powder lubricants. This paper primarily focuses on experiments carried out on a three-pad journal bearing and a disk-on-disk tribometer. Results showed that MoS2 traction curves resemble that of SAE 10 synthetic oil. Unlike liquid lubricants, powder films have a limiting shear strength property. Once the powder reaches this limiting value, the maximum traction coefficient is limited and the powder essentially shears along sliding walls. Experimental traction data shows evidence of this property in various powders. The thermal performance of the bearing was evaluated at speeds up to 30,000 rpm and loads up to 236 N. Although WS2 displayed constant friction coefficient and low temperature with increasing dimensionless load, MoS2 exhibited frictional behavior resembling that of a hydrodynamic lubricating film. In this paper, an attempt has been made to provide a criterion for the selection of solid lubricants for use in those tribosystems that may be operated in a high speed/load regime (i.e., high strain rates) as an alternative yard stick to conventional comparative approaches.

Analysis of Wind Field Fan Based on Performance Enhancement Method

2014 ◽  
Vol 986-987 ◽  
pp. 235-238
Author(s):  
Xiao Long Tan ◽  
Jia Zhou ◽  
Wen Bin Wang
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Performance Enhancement ◽  
Aerodynamic Performance ◽  
Wind Load ◽  
Wind Speeds ◽  
Enhancement Method ◽  
Changes Over Time ◽  
Load Simulation ◽  
Single Constant

For the simulation of wind turbine, the wind speed is extremely important parameters and indicators to measure the output power of the unit is the wind load. Therefore, in the airflow dynamics and simulation of wind loads before establishing an accurate wind speed model is crucial. At present, the application for wind turbines COMSOL fan, fan blades and wind load simulation field, the extremely important wind speed model is not perfect, most of the research is confined to a single constant wind speed, wind speed virtually ignored the magnitude and direction of change, on changes over time and space at the same time is one of the few studies of wind, so find a way to accurately describe the range of wind speeds, and can be combined well with COMSOL method can greatly improve the aerodynamic performance of wind turbines the overall level of .

scholarly journals Experimental Investigation of Lift Enhancement and Drag Reduction of Discrete Co-Flow Jet Rotor Airfoil

2021 ◽  
Vol 11 (20) ◽  
pp. 9561
Author(s):  
Shunlei Zhang ◽  
Xudong Yang ◽  
Bifeng Song ◽  
Zhuoyuan Li ◽  
Bo Wang
Keyword(s):  
Drag Reduction ◽  
High Performance ◽  
Performance Enhancement ◽  
Fundamental Problem ◽  
Unit Length ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Relative Unit ◽  
Lift Enhancement ◽  
Stall Angle

Rotor airfoil design involves multi-point and multi-objective complex constraints. How to significantly improve the maximum lift coefficient and lift-to-drag ratio of rotor airfoil is a fundamental problem, which should be solved urgently in the development of high-performance helicopter rotor blades. To address this, discrete co-flow jet (DCFJ) technology is one methods with the most potential that can be harnessed to improve the performance of the rotor airfoil. In this study, wind tunnel experiments are conducted to study the effect of DCFJ technology on lift enhancement and drag reduction of OA312 airfoil. Furthermore, the performance improvement effects of the open co-flow jet (CFJ) and DCFJ technologies are studied. In addition, the influence of fundamental parameters, such as the obstruction factor and relative unit length, are analyzed. Results demonstrate that DCFJ technology is better than CFJ technology on the performance enhancement of the OA312 airfoil. Moreover, the DCFJ rotor airfoil can significantly reduce the drag coefficient and increase the maximum lift coefficient and the stall angle of attack. The maximum lift coefficient can be increased by nearly 67.3%, and the stall angle of attack can be delayed by about 12°. The DCFJ rotor airfoil can achieve the optimal performance when the obstruction factor is 1/2 and the relative unit length is 0.025.

scholarly journals Biomechanics of the unique pterosaur pteroid

2009 ◽  
Vol 277 (1684) ◽  
pp. 1121-1127 ◽  
Author(s):  
Colin Palmer ◽  
Gareth J. Dyke
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Biomechanical Analysis ◽  
Aerodynamic Efficiency ◽  
Fourth Finger ◽  
Forward Part ◽  
The Way

Pterosaurs, flying reptiles from the Mesozoic, had wing membranes that were supported by their arm bones and a super-elongate fourth finger. Associated with the wing, pterosaurs also possessed a unique wrist bone—the pteroid—that functioned to support the forward part of the membrane in front of the leading edge, the propatagium. Pteroid shape varies across pterosaurs and reconstructions of its orientation vary (projecting anteriorly to the wing leading edge or medially, lying alongside it) and imply differences in the way that pterosaurs controlled their wings. Here we show, using biomechanical analysis and considerations of aerodynamic efficiency of a representative ornithocheirid pterosaur, that an anteriorly orientated pteroid is highly unlikely. Unless these pterosaurs only flew steadily and had very low body masses, their pteroids would have been likely to break if orientated anteriorly; the degree of movement required for a forward orientation would have introduced extreme membrane strains and required impractical tensioning in the propatagium membrane. This result can be generalized for other pterodactyloid pterosaurs because the resultant geometry of an anteriorly orientated pteroid would have reduced the aerodynamic performance of all wings and required the same impractical properties in the propatagium membrane. We demonstrate quantitatively that the more traditional reconstruction of a medially orientated pteroid was much more stable both structurally and aerodynamically, reflecting likely life position.

Aerodynamic Investigation of Double Surface Airfoil

2021 ◽  
Vol 1 (2) ◽  
pp. 41-46
Author(s):  
Siva J ◽  
Suresh C ◽  
Paramaguru V
Keyword(s):  
Experimental Investigation ◽  
Flow Separation ◽  
Research Work ◽  
Aerodynamic Performance ◽  
Aircraft Industry ◽  
Aerodynamic Efficiency ◽  
Flight Vehicles ◽  
Double Surface ◽  
Naca 0012 ◽  
Aerodynamic Investigation

Aircraft industry has been deeply concerned about reduction of drag by reducing flow separation and improving the aerodynamic efficiency of flight vehicles, particularly in commercial and military market by adopting various methods. Reduction of flow separation is a concept by which we can increase aerodynamic efficiency. The purpose of the project is to perform an experimental investigation on aerodynamic performance of NACA 0012 airfoil model with and without splits. It is evident from this research work that the airfoil model with split possesses greater aerodynamic performance by producing lesser overall drag. This is due to the delay in flow separation from the surface.

Sign in / Sign up

Export Citation Format

Share Document