Drag and lift measurements of solid sports balls in still air

2017 ◽  
Vol 232 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Jeff R Kensrud ◽  
Lloyd V Smith
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Rough Surface ◽  
Lift Coefficient ◽  
Laboratory Setting ◽  
Air Drag ◽  
High Speeds ◽  
Drag And Lift ◽  
Lift And Drag

The following article considers lift and drag measurements of solid sports balls propelled through still air in a laboratory setting. The balls traveled at speeds ranging from 26 to 134 m/s with spin rates up to 3900 r/min. Light gates measured the speed and location of the balls at two locations from which lift and drag values were determined. Ball roughness varied from polished to rough surface protrusions, that is, seams as high as 1.5 mm. Lift and drag were observed to depend on speed, spin rate, surface roughness, and seam orientation. A drag crisis was observed on smooth balls as well as non-rotating seamed balls with seam heights less than 0.9 mm. The drag coefficient of approximately 0.42 was nearly constant with speed for spinning seamed balls with seam height greater than 0.9 mm. The still air drag coefficient of smooth balls was comparable to wind tunnel drag at low speeds ( Re < 2 × 105) and higher than wind tunnel results at high speeds ( Re > 2 × 105). The lift and drag coefficients of spinning balls increased with increasing spin rate. The lift coefficient of baseballs was not sensitive to ball orientation or seam height.

Alula-Inspired Leading Edge Device for Low Reynolds Number Flight

2016 ◽  
Author(s):  
Boris A. Mandadzhiev ◽  
Michael K. Lynch ◽  
Leonardo P. Chamorro ◽  
Aimy A. Wissa
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Tip Vortex ◽  
Relative Angle ◽  
Lift And Drag

Robust and predictable aerodynamic performance of unmanned aerial vehicles at the limits of their design envelope is critical for safety and mission adaptability. In order for a fixed wing aircraft to maintain the lift necessary for sustained flight at very low speeds and large angles of attack (AoA), the wing shape has to change. This is often achieved by using deployable aerodynamic surfaces, such as flaps or slats, from the wing leading or trailing edges. In nature, one such device is a feathered structure on birds’ wings called the alula. The span of the alula is 5% to 20% of the wing and is attached to the first digit of the wing. The goal of the current study is to understand the aerodynamic effects of the alula on wing performance. A series of wind tunnel experiments are performed to quantify the effect of various alula deployment parameters on the aerodynamic performance of a cambered airfoil (S1223). A full wind tunnel span wing, with a single alula located at the wing mid-span is tested under uniform low-turbulence flow at three Reynolds numbers, Re = 85,000, 106,00 and 146,000. An experimental matrix is developed to find the range of effectiveness of an alula-type device. The alula relative angle of attack measured measured from the mean chord of the airfoil is varied to modulate tip-vortex strength, while the alula deflection is varied to modulate the distance of the tip vortex to the wing surface. Lift and drag forces were measured using a six axis force transducer. The lift and drag coefficients showed the greatest sensitivity to the the alula relative angle of attack, increasing the normalized lift coefficient by as much as 80%. Improvements in lift are strongly correlated to higher alula angle, with β = 0° – 5°, while reduction in the drag coefficient is observed with higher alula tip deflection ratios and lower β angles. Results show that, as the wing angle of attack and Reynolds number are increased, the overall lift co-efficient improvement is diminished while the reduction in drag coefficient is higher.

scholarly journals Investigations of Lift and Drag Performances on Neo-Ptero Micro UAV Models

2021 ◽  
Vol 84 (2) ◽  
pp. 50-62
Author(s):  
Noor Iswadi Ismail ◽  
Mahamad Hisyam Mahamad Basri ◽  
Hazim Sharudin ◽  
Zurriati Mohd Ali ◽  
Ahmad Aliff Ahmad Shariffuddin ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Successful Development ◽  
Aerodynamic Efficiency ◽  
Trade Off ◽  
Flight Stability ◽  
Stall Angle ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

This paper presents the investigation and improvement of lift and drag characteristics of Neo-Ptero micro-UAV models based on the virtual wind tunnel method. Despite its successful development and flight stability, the lift and drag coefficients characteristics of the current Mark 1 Neo-Ptero remain unknown. To improve the Mark 1 Neo-Ptero performances, Mark 2 Neo-Ptero model has given a new unsymmetrical airfoil wing configuration. The computational aerodynamic analysis was executed and focused on certain lift and drag coefficient characteristics. Lift coefficient results showed that Mark 2 improved in overall lift characteristics such as zero-lift angle, maximum lift magnitude and stall angle magnitude. Conversely, Mark 2 model suffered a slightly higher drag coefficient magnitude and more significant drag increment percentage than Mark 1. However, the trade-off between superior lift magnitude and minor drag generation induced by Mark 2 boosts the model’s aerodynamic efficiency performances but is only limited at early angle stages.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

Gliding Flight of the Dog-Faced Bat Rousettus Aegyptiacus Observed in a Wind Tunnel

1971 ◽  
Vol 55 (3) ◽  
pp. 833-845 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Trailing Edge ◽  
Number Range ◽  
High Speeds ◽  
Gliding Flight ◽  
Speed Range ◽  
Simple Regression Analysis ◽  
Drag Analysis ◽  
Very High

1. A bat was trained to fly in a tilting wind tunnel. Stereoscopic photographs were taken, both by reflected and by transmitted light, and measurements of best gliding angle were made. 2. Variation of wing span and area at different speeds was much less than in birds. This is attributed to the construction of the wing, which prevents the bat from folding back the manus in flight, because this would lead to collapse of the plagiopatagium. 3. The trailing edge of the wing is normally deflected upwards in flight, at least in the distal parts. This is interpreted as providing longitudinal stability. The plagiopatagialis proprii muscles appear to act as an elevator, by deflecting the trailing edge of the plagiopatagium upwards. 4. The speed range over which the bat could glide was 5·3-11·0 m/s. Its maximum lift coefficient was 1·5, and its best glide ratio 6·8:1. The Reynolds number range, based on mean chord, was 3·26 x 104 to 6·79 x 104. 5. A simple regression analysis of the glide polar indicated a very high span efficiency factor (k) and low wing profile drag coefficient (Cdp). On the other hand, a drag analysis on the assumption that k = 1 leads to an improbably large increase in the estimated Cdp at low speeds. It is suggested that the correct interpretation probably lies between these extremes, with k ≊ 1·5; Cdp would then be about 0·02 at high speeds, rising to somewhat over 0·1 at the minimum speed. 6. It would appear that the bat is not so good as a pigeon at fast gliding, but better at low-speed manoeuvring. On most points of performance, however, the two are remarkably similar.

Analysis of Vortex-Induced Vibration of Riser using Spalart-Almaras Model

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Jaswar Koto ◽  
Abdul Khair Junaidi
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Offshore Structures ◽  
The Other ◽  
Main Concern ◽  
Vortex Induced Vibration ◽  
Simulation Results ◽  
Lift And Drag

Vortex-induced vibration is natural phenomena where an object is exposed to moving fluid caused vibration of the object. Vortex-induced vibration occurred due to vortex shedding behind the object. One of the offshore structures that experience this vortex-induced vibration is riser. The riser experience vortex-induced vibration due to vortex shedding caused by external load which is sea current. The effect of this vortex shedding to the riser is fatigue damage. Vortex-induced vibration of riser becomes the main concern in oil and gas industry since there will be a lots of money to be invested for the installation and maintenance of the riser. The previous studies of this vortex-induced vibration have been conducted by experimental method and Computational Fluid Dynamics (CFD) method in order to predict the vortex shedding behaviour behind the riser body for the determination of way to improve the riser design. This thesis represented the analysis of vortex induced vibration of rigid riser in two-dimensional. The analysis is conducted using Computational Fluid Dynamic (CFD) simulations at Reynolds number at 40, 200, 1000, and 1500. The simulations were performed using Spalart-Allmaras turbulent model to solve the transport equation of turbulent viscosity. The simulations results at Reynolds number 40 and 200 is compared with the other studies for the validation of the simulation, then further simulations were conducted at Reynolds number of 1000 and 1500. The coefficient of lift and drag were obtained from the simulations. The comparison of lift and drag coefficient between the simulation results in this study and experiment results from the other studies showed good agreement. Besides that, the in-line vibration and cross-flow vibration at different Reynolds number were also investigated. The drag coefficient obtained from the simulation results remain unchanged as the Reynolds number increased from 200 to 1500. The lift coefficient obtained from the simulations increased as the Reynolds number increased from 40 to 1500.

scholarly journals The effect of wind tunnel interference on the characteristics of an aerofoil

1930 ◽  
Vol 129 (809) ◽  
pp. 135-145 ◽  
Keyword(s):  
Wind Tunnel ◽  
Uniform Distribution ◽  
Infinite Series ◽  
Rectangular Channel ◽  
Approximate Expression ◽  
Point Of View ◽  
Approximate Methods ◽  
Free Jet ◽  
Drag And Lift ◽  
Lift And Drag

The effect of the walls of the enclosure on the measured values of the lift and drag experienced by an aerofoil is quite appreciable and it has been known for a considerable time that correction must be applied to wind tunnel result before they can be applied to free air conditions. Prandtl* investigated the effect on an aerofoil in a free jet or circular tube both in the case where there is a uniform lift distribution, and in the case where there is an elliptic distribution of circulation. The elliptic distribution is of importance because it gives the minimum drag for a given lift. Glauert by means of an approximate method found the induced drag and lift in a rectangular channel when there is a uniform distribution of lift. Terazawa modified Glauert’s method and obtained the exact solution for an aerofoil with uniform distribution of circulation in a rectangular channel. It is The object of this note to extend these results and to obtain the induces drag and lift in a rectangular channel when there is an elliptic distribution of lift. In addition, the discussion of Prandtl is briefly gone through because Prandtl’s results are usually given as the first few terms of an infinite series, and it has not been noticed that the result can be obtained exactly. Glauert’s work on the effect of plane barries is briefly re-examined because, in his analysis, approximate expression were summed over an infinite series of points, and at first glance it appeared that this would introduce some error of the same order as the result. In this note the summation is carried out rigorously and the approximations to the actual values. The small divergences from Glauert’s result obtained by Terazawa in two numerical cases are, in effect, the result of a slightly more accurate approximation. From the practical point of view the results of this paper add little to what is known already, for the major corrections are given by the results of the approximate methods, but this note should fill in some small gaps in the theory of wind tunnel interference.

An Experimental Investigation Assessing the Validity of Quasi-Static Calculations for an Oscillating Hydrofoil

2011 ◽  
Author(s):  
Rajan Fernandez ◽  
Keith Alexander
Keyword(s):  
Steady Flow ◽  
Strouhal Number ◽  
Strong Dependence ◽  
Lift Coefficient ◽  
Experimental Program ◽  
Design Data ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Lift And Drag ◽  
Human Powered

Inspired by animals, flapping wing propulsion has been of interest since the early 1900s. Flapping hydrofoil propulsion has been attempted by designers of human powered watercraft because of the novelty and the apparent high theoretical efficiency, but with limited success. The earliest human powered hydrofoil, the Wasserlaufer, was invented by Julius Schuck in 1953. The first really successful human powered hydrofoil, the Trampofoil, was invented by Alexander Sahlin in 1998. While these craft function adequately the design data for flapping hydrofoils is inadequate or not available. This paper describes an experimental program and initial results for the required data. To design a vehicle with a lifting and thrusting oscillating hydrofoil the force that the hydrofoil will exert on the vehicle through its entire oscillating cycle must ideally be known. The force profiles could be estimated via quasi-static calculations based on steady flow lift and drag coefficients, but these often do not cover the full 360 degree range that can be required and there is doubt that the steady flow coefficients properly represent the dynamic situation of an oscillating hydrofoil. Hence a valuable process would be one that could determine dynamic drag and lift coefficient loops as function of the Strouhal number, heaving and pitching profiles. To work toward the collection of this information, experimental data is being recorded in a towing tank with an oscillating NACA4415 hydrofoil over a range of Strouhal numbers and types of oscillating profiles. While there are still some limitations to the experimental equipment preliminary experimental results show the limitations of using quasi-static calculations and go some way to providing the design data for the hydrofoil section tested. We conclude that quasi-static calculations based on the gliding coefficient curve for for an oscillating hydrofoil are only valid for very small Strouhal numbers (St≪0.05). We have shown that as the Strouhal number increases, the error in such calculations increases very rapidly. We also note that the lift coefficient of the hydrofoil has a strong dependence on the angle of attack and is not affected by the gliding stall.

scholarly journals Drag and lift forces on clean spherical and ellipsoidal bubbles in a solid-body rotating flow

2011 ◽  
Vol 682 ◽  
pp. 434-459 ◽  
Author(s):  
MARIE RASTELLO ◽  
JEAN-LOUIS MARIÉ ◽  
MICHEL LANCE
Keyword(s):  
Aspect Ratio ◽  
Drag Coefficient ◽  
Solid Body ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Rotating Flow ◽  
Wide Range ◽  
Spherical Bubbles ◽  
Drag And Lift

A single bubble is placed in a solid-body rotating flow of silicon oil. From the measurement of its equilibrium position, lift and drag forces are determined. Five different silicon oils have been used, providing five different viscosities and Morton numbers. Experiments have been performed over a wide range of bubble Reynolds numbers (0.7 ≤ Re ≤ 380), Rossby numbers (0.58 ≤ Ro ≤ 26) and bubble aspect ratios (1 ≤ χ ≤ 3). For spherical bubbles, the drag coefficient at the first order is the same as that of clean spherical bubbles in a uniform flow. It noticeably increases with the local shear S = Ro−1, following a Ro−5/2 power law. The lift coefficient tends to 0.5 for large Re numbers and rapidly decreases as Re tends to zero, in agreement with existing simulations. It becomes hardly measurable for Re approaching unity. When bubbles start to shrink with Re numbers decreasing slowly, drag and lift coefficients instantaneously follow their stationary curves versus Re. In the standard Eötvös–Reynolds diagram, the transitions from spherical to deformed shapes slightly differ from the uniform flow case, with asymmetric shapes appearing. The aspect ratio χ for deformed bubbles increases with the Weber number following a law which lies in between the two expressions derived from the potential flow theory by Moore (J. Fluid Mech., vol. 6, 1959, pp. 113–130) and Moore (J. Fluid Mech., vol. 23, 1965, pp. 749–766) at low- and moderate We, and the bubble orients with an angle between its minor axis and the direction of the flow that increases for low Ro. The drag coefficient increases with χ, to an extent which is well predicted by the Moore (1965) drag law at high Re and Ro. The lift coefficient is a function of both χ and Re. It increases linearly with (χ − 1) at high Re, in line with the inviscid theory, while in the intermediate range of Reynolds numbers, a decrease of lift with aspect ratio is observed. However, the deformation is not sufficient for a reversal of lift to occur.

Analysis of lift and drag coefficients of a GT2 racing car at various speeds with movable wheels and ground

2015 ◽  
Vol 12 (3) ◽  
pp. 261-270
Author(s):  
Albert Boretti
Keyword(s):  
Wind Tunnel ◽  
Drag Force ◽  
Computational Fluid Dynamic ◽  
Lift Force ◽  
Fluid Dynamic ◽  
Time Simulation ◽  
Rear Wing ◽  
Speed Range ◽  
Drag And Lift ◽  
Lift And Drag

The paper proposes a study of a GT2 racing car with a computational fluid dynamic (CFD) tool. Results of STAR-CCM+ simulations of the flow around the car in a wind tunnel with movable ground and wheels are presented for different air speeds to assess the different contributions of pressure and shear to lift and drag over the speed range. The rear wing contributes more than 85% of the lift force and 7-8% of the drag force for this particular class of racing cars. When reference is made to the low speed drag and lift coefficients, increasing the speed from 25 to 100 m/s produces an increase of CD of more than 3% and a reduction of CL of more than 2%. The resultsuggests modifying the constant CD and CL values used in lap time simulation toolsintroducing the tabulated values to interpolate vs. the speed of the car.

Effects of surface flow visualisation on aerodynamic loads at low Reynolds number

2015 ◽  
Vol 119 (1215) ◽  
pp. 663-672
Author(s):  
L. W. Traub ◽  
R. Waghela ◽  
E. M. Botero
Keyword(s):  
Drag Coefficient ◽  
Lift Coefficient ◽  
Time History ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Distribution Method ◽  
History Of ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

AbstractIn this article, the effect of on-surface flow visualisation (SVF) techniques on measured loads over an airfoil are explored. Titanium dioxide based mixture effects on the lift and drag coefficient are experimentally quantified at low Reynolds numbers by recording the time history as the patterns evolve and freeze. With statistical comparison based on Student’s t-distribution method, it was determined that the effect on the drag coefficient was minimal but the lift coefficient was slightly attenuated. Additionally, it was observed that at high angles-of-attack the temporal history of the flow as the wind tunnel ramps up may alter the steady-state flow field in the presence of a SFV mixture.

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