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.

Numerical Investigation of the Drag and Lift Forces Acting on Impenetrable Rotating Spherical Nano-Particle

2008 ◽  
Author(s):  
M. R. Meigounpoory ◽  
A. Rahi ◽  
A. Mirbozorgi
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Slip Condition ◽  
Nano Particle ◽  
Slip Coefficient ◽  
Slip Boundary ◽  
Lift Forces ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

The drag and lift forces acting on a rotating impenetrable spherical suspended nano-particle in a homogeneous uniform flow are numerically studied by means of a three-dimensional numerical simulation with slip boundary condition. The effects of both the slip coefficient and rotational speed of the nanosphere on the drag and lift forces are investigated for Reynolds numbers in the range of 0.1 < Re < 100. Increase of rotation increases the drag and lift force exerted by flow at the surface of nano-sphere. By increasing slip coefficient the values of drag and lift coefficients decreases. At full slip condition, rotation of the nano-sphere has not significant effects on the drag and lift coefficient values moreover the lift coefficient of flow around the rotating spherical particle will be vanished. Present numerical results at no-slip condition are in good agreements with certain results of flow around of rotating sphere.

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.

scholarly journals Aerodynamics of aero-engine installation

2016 ◽  
Vol 230 (14) ◽  
pp. 2673-2692 ◽  
Author(s):  
Tomasz P Stańkowski ◽  
David G MacManus ◽  
Christopher TJ Sheaf ◽  
Robert Christie
Keyword(s):  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Installation Effects ◽  
Through Flow ◽  
Aero Engine ◽  
Flow Capture ◽  
Research Programmes ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Aircraft Aerodynamics

This paper describes current progress in the development of methods to assess aero-engine airframe installation effects. The aerodynamic characteristics of isolated intakes, a typical transonic transport aircraft as well as a combination of a through-flow nacelle and aircraft configuration have been evaluated. The validation task for an isolated engine nacelle is carried out with concern for the accuracy in the assessment of intake performance descriptors such as mass flow capture ratio and drag rise Mach number. The necessary mesh and modelling requirements to simulate the nacelle aerodynamics are determined. Furthermore, the validation of the numerical model for the aircraft is performed as an extension of work that has been carried out under previous drag prediction research programmes. The validation of the aircraft model has been extended to include the geometry with through flow nacelles. Finally, the assessment of the mutual impact of the through flow nacelle and aircraft aerodynamics was performed. The drag and lift coefficient breakdown has been presented in order to identify the component sources of the drag associated with the engine installation. The paper concludes with an assessment of installation drag for through-flow nacelles and the determination of aerodynamic interference between the nacelle and the aircraft.

Impulsively Started Steady Flow About Rectangular Prisms: Experiments and Discrete Vortex Analysis

1986 ◽  
Vol 108 (1) ◽  
pp. 47-54 ◽  
Author(s):  
T. Sarpkaya ◽  
C. J. Ihrig
Keyword(s):  
Reynolds Number ◽  
Steady Flow ◽  
Strouhal Number ◽  
Relative Displacement ◽  
Shear Layers ◽  
Discrete Vortex ◽  
Vortex Model ◽  
Vorticity Distribution ◽  
Initial Rise ◽  
Lift And Drag

Impulsively started steady flow about sharp-edged rectangular prisms has been investigated experimentally and numerically. The forces acting on the bodies have been determined at a Reynolds number of about 20,000 for various angles of incidence as a function of the relative displacement of the fluid. The results have shown that the shedding of the first few vortices has profound effects on both the lift and drag coefficients, often resulting in a large initial rise in drag. The surface-vorticity-distribution version of the discrete vortex model has shown that the strength of the vortex clusters varies from 80 to 90 percent of the vorticity generated in the shear layers. The Strouhal number is correctly predicted but the calculated forces are somewhat larger than those measured experimentally.

Influence of incidence angle on the aerodynamic characteristics of square cylinders with rounded corners

2016 ◽  
Vol 26 (1) ◽  
pp. 269-283 ◽  
Author(s):  
Sajjad Miran ◽  
Chang Hyun Sohn
Keyword(s):  
Incidence Angle ◽  
Lift Coefficient ◽  
Square Cylinder ◽  
Aerodynamic Forces ◽  
Content Type ◽  
Minimum Drag ◽  
Rounded Corner ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Critical Incidence

Purpose – The purpose of this paper is to focus on the variation of wake structures and aerodynamic forces with changes in the cylinder corner radius and orientation. Design/methodology/approach – Numerical simulations were performed for flow past a square cylinder with different corner radii placed at an angle to the incoming flow. In the present study, the rounded corner ratio R/D=0 (square cylinder), 0.1, 0.2, 0.3, and 0.4 (where R is the corner radius and D is the characteristic dimension of the body) and the angle of incidence α in the range of 0°-45° were considered. Findings – The numerical model was validated by comparing the present results with results in the available literature, and they were found to be in good agreement. The critical incidence angle for the rounded corner cylinder – corresponding to the minimum mean drag coefficient (C D ), the minimum root mean square value of the lift coefficient C L,RMS), and the maximum Strouhal number – shifted to a lower incidence angle compared with the sharp corner square cylinder. The minimum drag and lift coefficient at R/D=0 were observed for the critical incidence angle αcri=12°, whereas for R/D=0.1-0.4, the minimum drag and lift coefficient were found to be within the range of 5°-10° for α. Originality/value – The presented results shows the importance of the incidence angle and rounded corners of the square cylinder for reduction of aerodynamic forces. The two parameters support the shear layer flow reattachment on the lateral surface of the cylinder, have a strong correlation with the reduction of the wake width, and hence reduced the values of C D and C L .

scholarly journals ANALYSIS OF THE USE OF SPOILER ONE LEVEL AND TWO LEVELS IN CONDITIONS OF STEADY AGAINST THE DRAG AND LIFT COEFFICIENTS ON A SEDAN TYPE CAR BY USING CFD (COMPUTATIONAL FLUID DYNAMIC)

2019 ◽  
Vol 1 (2) ◽  
pp. 58
Author(s):  
Fajar Frihdianto ◽  
Nyeyep Sri Wardani ◽  
Indah Widiastuti
Keyword(s):  
Drag Coefficient ◽  
Steady Flow ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Lift Coefficient ◽  
Color Difference ◽  
Lower Surface ◽  
Significant Difference ◽  
The Difference ◽  
Drag And Lift

<p><em>This research was simulation analyzing the condition of steady flow in around of body car made and analized computly using CFD program (Computational Fluid Dynamic). The model used was Sedan car designed with different rear end body by adding spoiler. Analyzing in this research was done by using Software 18.2–CFD Student Version. Design of the three models were compared to find out the difference in magnitude of Coefficient of Drag, Coefficient of Lift, pressure distribution, velocity distribution, and behavioral character of flow around the rear end of car in the condition of steady flow. Model was made in appropriate scale with model of Honda city 2008 sedan car</em><em>. </em><em>Observation was made to look at the behavior of fluida flows both in front and back the car in different fluid speed ranges in steady condition.</em></p><p><em>The simulation results obtained from packet CFD on each condition were; model without spoiler, model with 1 level spoiler, and model with 2 level spoiler. Where this simulation showed that CD and CL were decrease</em><em>. </em><em>One of the example was at speed 40km/hour obtained the coefficient of drag (CD) of 0.31061, 0.28603, and 0.2054, it proved that 1 level spoiler could reduce the value of drag coefficient about 7.9135% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of drag coefficient about 33.8592% without spoiler. For the coefficient of lift (CL) on each model was -0.38487, -0.54624, and -0.62097 proved that spoiler 1 level could reduce the value of lift coeffient about 41.92845% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of lift coefficient about 61.35984% without spoiler. On the result of pressure distrubution and relative velocity give little affect to the upper and lower surface where this was indicated by almost no color difference contours. Then, if it was indicated from streamline and the formation of vortex, there was a significant difference so that it was very influential on the size of CD and CL occoured. By changing geometric proved that the spoiler car 1 and 2 level were more aerodynamic than the car without spoiler.</em></p>

INVESTIGASI NUMERIK VIV (VORTEX INDUCED VIBRATION) PADA DIAMETER KABEL HYDROPHONE 0.04 M SISTEM AKUSTIK BAWAH AIR

ROTOR ◽  
2017 ◽  
Vol 10 (2) ◽  
pp. 47
Author(s):  
Maria Margareta Zau Beu ◽  
I Putu Andhi Indira Kusuma
Keyword(s):  
Flow Pattern ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Acoustic System ◽  
Vortex Induced Vibration ◽  
Maximum Value ◽  
2D Numerical Simulation ◽  
Simulation Results ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

The 2D numerical simulation of an underwater acoustic system undergoing VIV (Vortex Induced Vibration) which is in position parallel to 5 m distance with variation of hydrophone cable position. The diameter of the hydrophone cable in use is 0.04 m, with Reynold numbers (Re) variations of 13000, 15000, 17000, 19000, 21000, 23000, 25000, 27000 and 30000. Position variations are used to determine the flow pattern characteristics that occur behind the cylinder as well the maximum value of drag coefficient (CD) and lift coefficient (CL). The simulation results show that the characteristic flow pattern around a cylinder at each Re value indicates the release of the vortex behind the cylinder with different drag and lift coefficient values.  Keywords: Vortex Shedding, Hydrophone, Acoustic System

Experimental Study on the Dynamics of Four Flexible Cylinders in Square Arrangement Subjected to Uniform Cross-Flow

2012 ◽  
Author(s):  
Bijan Sanaati ◽  
Naomi Kato
Keyword(s):  
Amplitude Ratio ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Mass Ratio ◽  
Drag Forces ◽  
Low Mass ◽  
Drag And Lift ◽  
Low Mass Ratio ◽  
Lift And Drag ◽  
Four Cylinders

Groups of cylinders can be found in many engineering fields such as marine and civil applications. The behaviors of the group cylinders can be very complex because it undergoes the mutual effects of adjacent cylinders arranged in different positions. In this paper, we present the results of a study on the dynamics of a group of flexible cylinders in square arrangements along with a single (isolated) cylinder subjected to uniform cross-flow (CF). Four cylinders of the same size, properties, and pretensions were tested in two configurations with different centre-to-centre separations. Horizontal and vertical separations were 2.75D & 2.75D and 5.50D & 2.75D for the first and second configurations, respectively. The tandem (horizontal) separations between the downstream and upstream cylinders, i.e., 2.75D and 5.5D, correspond to the reattachment and co-shedding regimes, respectively. Vertical separation, i.e., 2.75 was chosen in a range where the side-by-side cylinders can have proximity interference. Reynolds number ranged from 1400 to 20000 (subcritical regime). The parameter of reduced velocity reached up to 19. The aspect ratio of all the cylinders was 162 (length/diameter). Mass ratio (cylinders mass/displaced water) is 1.17, a low mass ratio. The amplitude ratio of the CF vibration of the downstream cylinders, hydrodynamic force coefficients including mean and fluctuating components of the drag and lift forces, and frequency responses for both CF and inline (IL) directions were analyzed. All the cylinders excited up to the second and fourth mode of vibrations for CF and IL directions, respectively. Mean drag coefficient of the upstream cylinders are almost twice those of the downstream cylinders at high reduced velocities. The mean lift coefficient is much higher for the upstream cylinders than the downstream cylinders with a negative value. Obvious IL and CF lock-in regions exist for all four cylinders at low reduced velocities. Among the four cylinders, the upper downstream cylinder shows the least and the most fluctuating lift and drag forces, respectively. The IL and CF frequencies of the downstream cylinders are much lower than those of the upstream ones and the single cylinder.

CFD Analysis of Drag Reduction Using External Devices on Pickup Trucks

2010 ◽  
Author(s):  
Feysal A. Adem ◽  
Dongmei Zhou ◽  
Pramod Krishnani
Keyword(s):  
Numerical Simulations ◽  
Inclination Angle ◽  
Cfd Simulation ◽  
Aerodynamic Drag ◽  
Lift Coefficient ◽  
Aerodynamic Drag Coefficient ◽  
Zero Degree ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Yaw Angle

The flows over a pickup truck with add-on devises were studied using computational fluid dynamics (CFD) with the objective of investigating the effect of these add-no devices on the flow structures around the vehicle, aerodynamic drag, and lift coefficient. All numerical simulations were performed using commercial CFD software Fluent [8]. A generic pickup model with extended cab was used as the base model and all the flow simulations were performed at zero degree yaw angle. The pickup configurations used in the present CFD simulation include Aerocap with different rear inclination angle α, Tonneau cover, Rear Roof Garnish, and Tail-plates. Results from numerical simulations indicated that Aerocap with inclination angle α = 12° and a reduced rear width has produced the minimum aerodynamic drag coefficient. It was also shown that the wake region decrease when the rear inclination angle increases.

Sign in / Sign up

Export Citation Format

Share Document