scholarly journals Influence of yaw on propeller aerodynamic characteristics

2018 ◽  
Vol 180 ◽  
pp. 02074
Author(s):  
Van Bang Nguyen ◽  
Dalibor Rozehnal ◽  
Jakub Hnidka ◽  
Vu Uy Pham
Keyword(s):  
Free Stream ◽  
Aerodynamic Characteristics ◽  
Yaw Angle ◽  
Thrust And Torque ◽  
Stream Direction ◽  
Propeller Thrust

Between the propeller axis and free stream direction, it can still be a non-zero yaw angle. This paper introduces some propeller experiments, in which the propeller aerodynamic characteristics have been determined in various yaw angle and different rotational speeds. The experimental aerodynamic characteristics are acquired dynamic values, from which the influence of yaw conditions on the frequency and the amplitude of propeller thrust and torque can be obtained.

scholarly journals Bearing friction effect on cup anemometer performance modelling

2021 ◽  
Vol 2090 (1) ◽  
pp. 012101
Author(s):  
D Alfonso-Corcuera ◽  
S. Pindado ◽  
M Ogueta-Gutiérrez ◽  
A Sanz-Andrés
Keyword(s):  
Rotation Rate ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Friction Torque ◽  
Performance Modelling ◽  
Friction Forces ◽  
Aerodynamic Drag Coefficient ◽  
Yaw Angle ◽  
Cup Anemometer ◽  
Bearing Friction

Abstract In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

scholarly journals Numerical studies on aerodynamics of high-speed railway train subjected to strong crosswind

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988727
Author(s):  
Xu Wang ◽  
Yuanhao Qian ◽  
Zengshun Chen ◽  
Xiao Zhou ◽  
Huaqiang Li ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Width Ratio ◽  
Force Coefficient ◽  
Rolling Moment ◽  
Side Force ◽  
Train Speed ◽  
Yaw Angle

Under the action of strong crosswind, the aerodynamic behavior of a rail vehicle at high speed will be changed significantly, which could directly affect the safe operation of the vehicle. With the help of the shape of train used in China, the aerodynamic characteristics of trains with scale of 1:1 is investigated using computational fluid dynamics numerical simulation method, which consists of the variation of aerodynamics force and moment with wind yaw angle, wind speed, train speed, and nose shape. After an initial validation against Baker’s results from wind tunnel test, the numerical model is then used to investigate the aerodynamic characteristics of the trains. The numerical results indicate that lift coefficient of the M train is slightly higher than TMC1 and TMC2 trains. Regardless of aerodynamics force coefficients, TMC1 reaches the maximum at a yaw angle of 75°. Aerodynamics force coefficient increases with both wind speed and train speed, but the change of which is not linear. Comparing aerodynamic force with different geometric dimensions of train nose, it is shown that height–width ratio is insensitive to side force and rolling moment, but sensitive to lift force from the yaw angle 0°–90°. The side force coefficient, as we most concern, is less than other results, when the length–width ratio is 1 and height–width is 0.87.

Transverse motion of an elastic sphere in a shear field

1973 ◽  
Vol 59 (1) ◽  
pp. 177-185 ◽  
Author(s):  
Christopher K. W. Tam ◽  
William A. Hyman
Keyword(s):  
Free Stream ◽  
Spherical Shape ◽  
Transverse Motion ◽  
Elastic Sphere ◽  
Shear Field ◽  
Elastic Particle ◽  
Small Deformations ◽  
Viscous Stresses ◽  
Stream Direction

The forces acting on an elastic particle suspended in a shear field, and moving relative to it, are found for the case in which there are small deformations from an initially spherical shape. The deformation is the result of the viscous stresses acting on the particle. Of principal interest is that there is a component of the force perpendicular to the free-stream direction, so that the particle will migrate across the undisturbed streamlines.

scholarly journals Aerodynamics of a cycling wheel in crosswind by coaxial volumetric velocimetry

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Constantin Jux ◽  
Andrea Sciacchitano ◽  
Fulvio Scarano
Keyword(s):  
Surface Texture ◽  
Rotational Velocity ◽  
Aerodynamic Resistance ◽  
Aerodynamic Characteristics ◽  
Force Measurements ◽  
Road Cycling ◽  
Stall Angle ◽  
Yaw Angle

The aerodynamic characteristics of a modern road cycling wheel in crosswind are studied through force measurements and 3D velocimetry in TU Delft’s Open Jet Facility. The performance of the 62 mm deep rim is evaluated for two tire profiles, and yaw angles up to 20◦ . All measurements are executed at 12.5 m/s (45 km/h) freestream- and wheel-rotational velocity. The wheel’s rim-tire section in crosswind is found to behave similar to an airfoil at incidence, ultimately resulting in a reduction of the wheel’s aerodynamic resistance with increasing yaw angle magnitude. This trend, also referred to as the sail-effect, is limited by the stall angle of the tire-rim profile. The stall angle is found to be dependent on the tire surface texture and varies between 14◦ and 20◦.

scholarly journals Investigations on the Unsteady Aerodynamic Characteristics of a Horizontal-Axis Wind Turbine during Dynamic Yaw Processes

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3124 ◽  
Author(s):  
Xiaodong Wang ◽  
Zhaoliang Ye ◽  
Shun Kang ◽  
Hui Hu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Azimuth Angle ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Structured Grid ◽  
Unsteady Aerodynamic ◽  
Yaw Angle

Wind turbines inevitably experience yawed flows, resulting in fluctuations of the angle of attack (AOA) of airfoils, which can considerably impact the aerodynamic characteristics of the turbine blades. In this paper, a horizontal-axis wind turbine (HAWT) was modeled using a structured grid with multiple blocks. Then, the aerodynamic characteristics of the wind turbine were investigated under static and dynamic yawed conditions using the Unsteady Reynolds Averaged Navier-Stokes (URANS) method. In addition, start-stop yawing rotations at two different velocities were studied. The results suggest that AOA fluctuation under yawing conditions is caused by two separate effects: blade advancing & retreating and upwind & downwind yawing. At a positive yaw angle, the blade advancing & retreating effect causes a maximum AOA at an azimuth angle of 0°. Moreover, the effect is more dominant in inboard airfoils compared to outboard airfoils. The upwind & downwind yawing effect occurs when the wind turbine experiences dynamic yawing motion. The effect increases the AOA when the blade is yawing upwind and vice versa. The phenomena become more dominant with the increase of yawing rate. The torque of the blade in the forward yawing condition is much higher than in backward yawing, owing to the reversal of the yaw velocity.

The Lift of Twisted and Cambered Wings in Supersonic Flow

1955 ◽  
Vol 6 (2) ◽  
pp. 149-163 ◽  
Author(s):  
G. N. Lance
Keyword(s):  
Integral Equation ◽  
Velocity Potential ◽  
Free Stream ◽  
Delta Wing ◽  
Complete Solution ◽  
Symmetric Potential ◽  
Leading Edges ◽  
Limiting Case ◽  
The Given ◽  
Stream Direction

SummaryA generalised conical flow theory is used to deduce an integral equation relating the velocity potential on a delta wing (with subsonic leading edges) to the given downwash distribution over the wing. The complete solution of this integral equation is derived. This complete solution is composed of two parts, one being symmetric and the other anti-symmetric with respect to the span wise co-ordinate; each part represents a velocity potential. For example, if y is the spanwise co-ordinate and x is measured in the free stream direction, then a downwash of the form w= - α11 Ux|y| is symmetric and will give rise to a symmetric potential, whereas w= - α11 Ux|y| sgn y is anti-symmetric and gives rise to an anti-symmetric potential. The velocity potentials of such flows are given in the form of Tables for all downwashes up to and including homogenous cubics in the spanwise and streamwise co-ordinates. Table III gives similar formulae in the limiting case when the leading edges become transonic; these are compared with results given elsewhere and serve as a check on the results of Tables I and II.

A Propeller Thrust and Torque Dynamometer for Wind Tunnel Models

Strain ◽  
2002 ◽  
Vol 38 (1) ◽  
pp. 3-10 ◽  
Author(s):  
A. F. Molland ◽  
S. R. Turnock
Keyword(s):  
Wind Tunnel ◽  
Thrust And Torque ◽  
Propeller Thrust

Investigation of Wedge Probe Wall Proximity Effects: Part 1—Experimental Study

1997 ◽  
Vol 119 (3) ◽  
pp. 598-604 ◽  
Author(s):  
P. D. Smout ◽  
P. C. Ivey
Keyword(s):  
Large Scale ◽  
Free Stream ◽  
Wedge Angle ◽  
Outer Wall ◽  
Proximity Effects ◽  
Stem Design ◽  
Local Flow ◽  
Dynamic Head ◽  
Yaw Angle ◽  
Wall Proximity

Conventional three-hole wedge probes fail to measure the correct static pressure when operating in close proximity to a wall or boundary through which the probe is inserted. The free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. This paper reports a series of experiments aimed at quantifying this so-called “wall proximity effect.” It is shown from a factorial experiment that probe wedge angle, stem design, and free-stream Mach number all have a significant influence. The yaw angle sensitivity of wedge probes is also found to depend on the proximity of the probe to the wall of introduction. Flow visualization studies on large-scale probe models are described, and a qualitative model of the probe local flow structures is developed. This model is used to explain the near-wall characteristics of the actual size wedge probes. In Part 2 of this paper, the experimental data are used to validate CFD calculations of the flow field around a wedge probe. A simple analytical model of the probe/flow interaction is developed from the CFD solutions.

scholarly journals On Fast-Response Probes: Part 2 — Aerodynamic Probe Design Studies

1994 ◽  
Author(s):  
Hans J. Humm ◽  
Christoph R. Gossweiler ◽  
George Gyarmathy
Keyword(s):  
Measurement Errors ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Fast Response ◽  
Circular Cylinders ◽  
Probe Design ◽  
Transient Nature ◽  
Reduced Frequency ◽  
Probe Size ◽  
Yaw Angle

The influence of the probe size and geometry on the quality of fast-response measurements in turbomachines has been experimentally investigated. For investigations in the static domain (time independent flows) probes were calibrated in two continuously operating wind tunnels in the range 0.2< Ma < 1.2. For dynamic calibrations in time variant flows model experiments in water (0.025 < k < 0.4, reduced frequency) were performed. Aerodynamic characteristics were determined for a great number of probe geometries such as circular cylinders and wedge-type probes with varied apex angles, locations of the sensing holes and leading edge shapes. The experiments comprised investigations in tolerance ranges for prismatic total pressure probes, yaw angle sensitivity, yaw angle and Mach number effects on calibration and influence of dynamic yaw angle fluctuation on probe characteristics. As a result of the experiments errors due to static and dynamic aerodynamic effects could be quantified. The majority of the errors arising during measurements in turbomachines can be directly related to the probe size. An important number of these errors are systematic and can be analytically modelled and hence their influence corrected. In fluctuating flows the most severe measurement errors, which often may exceed the quantity of interest, are due to dynamic stall effects. This phenomenon, which is of transient nature and cannot be corrected, is typical for sharp wedge probes but is not present with circular cylinders or the effects being much smaller with very blunt wedges.

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