Watch some of the magnet fishing videos on YouTube. One guys channel is dedicated to it. He finds quite a few guns and explains the various laws of turning them in depending on where he is.
He gets to keep some of them and restores them if he can.
He gets to keep some of them and restores them if he can.
No AeroSpaceCadet (Pro)- but wonder what dimpled rollers would do for a leading edge? The Golf ball dimples might work...some....how....mebbe?
No need to wonder.
http://www.journals.theired.org/assets/pdf/20151019_064614.pdf
Excerpt;
Bhadri Rajasai, Ravi Tej, Sindhu Srinath
Abstract— This paper is concerned with analysis of the turbulent flow over dimpled aerofoil profiles. Dimples of varying aspect ratio are used to study the effects on the skin-friction drag and lift. An external flow study was performed using ANSYS FLUENT. Simulations for external flow configuration with and without dimples were carried out and analyzed in detail. The resulting pressure drop and drag were observed. The objective was to clarify whether or not dimples cause reduction of the skin- friction drag and if it would provide better lift.
Keywords—Aerofoil, Aspect ratio, Drag, Dimple, Pressure- drop
I. INTRODUCTION
Dimples on golf balls have been inspiring engineers in the field of vehicle aerodynamics considering its effect in reducing drag on spinning bodies. A golf ball with a dimpled surface can travel higher and further than a smooth surfaced golf ball when subjected to identical force. The dimples on golf balls induce turbulence at lower Reynolds number, providing extra momentum or energy to the boundary layer and causing delay in flow separation. This phenomenon causes smaller wake areas or swirling flow regions behind the ball, thus reducing the total drag.
Till now these have been ignored because dimples help in reduction of pressure drag. In case of aerodynamic bodies pressure drag is very little compared to bluff bodies. An airfoil is an aerodynamic body so dimples do not affect to its drag much at zero angle of attack, but as soon as airfoil attains some angle of attack, wake formation starts due to boundary layer separation. Application dimples on aircraft wing model works in same manner as vortex generators. Past studies observed that dimples on an airfoil created extra turbulence to delay the boundary layer separation. Adding a dimple on a streamlined body might help delay the flow separation and reduce the size of the wake but it might also increase the friction drag as a trade-off. Hence, it is necessary to optimize the position and dimensions of the dimple relative to the size of the whole body.
Bhadri Rajasai
R.V.College of Engineering India
Ravi Tej. G
R.V.College of engineering India
Sindhu Srinath
R.V.College of Engineering India
In order to verify the effect of dimples, the following computational study has been made on 3-D inward dimpled wing sections extruded from NACA aerofoils. In order to have a comparative study, slices of the aerofoils with and without dimples of different aspect ratios were simulated.
II. MODELS
In order to carry out the study on the proposed idea, standard Aerofoil profiles have been selected on which the whole study was conducted. Simulations were carried out on the aerofoil – NACA 2412. The study assumes the use of incompressible and isothermal flow.
Fig. 1. Two dimensional NACA 2412 profile
The 3D model for the various cases used in the simulation were developed on Solidworks 2014, while the simulations
were carried out in ANSYS 15.0 (FLUENT).
The 3D model was debossed with dimples of various aspect
ratios and positions along the chord of the section.
Fig. 2. Plain extruded NACA 2412 section
Fig. 3. Extruded NACA 2412 section with dimple at mid-chord with an aspect ratio of 0.7
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