Streamwise Fluidelastic Instability in a Deformed Rotated Triangular Tube Array With Pitch-to-Diameter Ratio of 1.375

2015 ◽  
Author(s):  
Daniel B. Keogh ◽  
Craig Meskell
Keyword(s):  
Surface Pressure ◽  
Diameter Ratio ◽  
Streamwise Direction ◽  
Pressure Data ◽  
Steam Generators ◽  
Drag Forces ◽  
Surface Pressure Distribution ◽  
Pressure Distributions ◽  
Fluidelastic Instability ◽  
Stable Flow

A study of the surface pressure distribution of a cylinder in a deformed rotated triangular tube array with pitch-to-diameter ratio of 1.375 has been performed. This work was motivated by the failure of steam generators in San Onofre Nuclear Generating Station (SONGS) in Southern California, which occurred as a result of fluidelastic instability in the streamwise direction. This particular failure occurred in the U-bend region of the steam generators. The presence of anti-vibration bars (AVB) in this region prevent the tubes from experiencing fluidelastic insatiably (FEI) in the transverse direction but offer little support in the streamwise direction. This study analyses the streamwise direction vibration of the tubes in the U-bend region using experimental data and a simplified quasi-steady model. Surface pressure data was gathered in a draw down wind tunnel for a range of flow velocities using an instrumented cylinder with 36 pressure taps around the circumference of the cylinder at midplane. The instrumented cylinder was mounted in the 4th and 6th rows of the tube array. The effect of streamwise displacement of up to ±10% of the instrumented tube and its neighbours was investigated. Although bi-stable flow was detected, only the forces in the lift direction were substantially affected. The displacement dependent drag forces acting on the instrumented cylinder were determined by integrating the pressure distributions with respect to angle. Hence the coupled fluid stiffness matrix could be assembled for each flow velocity studied. The effect of Reynolds number was also investigated for a number of scenarios.

Surface Pressure Distribution on a Blade of a 10 m Diameter HAWT (Field Measurements versus Wind Tunnel Measurements)

2005 ◽  
Vol 127 (2) ◽  
pp. 185-191 ◽  
Author(s):  
T. Maeda ◽  
E. Ismaili ◽  
H. Kawabuchi ◽  
Y. Kamada
Keyword(s):  
Wind Tunnel ◽  
Surface Pressure ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Blade Surface ◽  
Pressure Data ◽  
Surface Pressure Distribution ◽  
Pressure Distributions ◽  
Wind Tunnel Data ◽  
Local Angle

This paper exploits blade surface pressure data acquired by testing a three-bladed upwind turbine operating in the field. Data were collected for a rotor blade at spanwise 0.7R with the rotor disc at zero yaw. Then, for the same blade, surface pressure data were acquired by testing in a wind tunnel. Analyses compared aerodynamic forces and surface pressure distributions under field conditions against analogous baseline data acquired from the wind tunnel data. The results show that aerodynamic performance of the section 70%, for local angle of attack below static stall, is similar for free stream and wind tunnel conditions and resemblances those commonly observed on two-dimensional aerofoils near stall. For post-stall flow, it is presumed that the exhibited differences are attributes of the differences on the Reynolds numbers at which the experiments were conducted.

Bi-Stable Flow in Parallel Triangular Tube Arrays With a Pitch-to-Diameter Ratio of 1.375

2014 ◽  
Author(s):  
Daniel B. Keogh ◽  
Craig Meskell
Keyword(s):  
Test Section ◽  
Diameter Ratio ◽  
Pressure Data ◽  
Cross Sectional ◽  
Pressure Distributions ◽  
Tube Arrays ◽  
Highly Correlated ◽  
Image Pairs ◽  
Stable Flow ◽  
Circumferential Pressure

A study of the bi-stable flow in parallel triangular tube arrays with a pitch to diameter ratio of 1.375 has been performed. Using surface pressure data from two instrumented cylinders (one cylinder with 36 circumferential pressure taps, one cylinder with 27 axial pressure taps) and particle image velocimetry (PIV) data, the bi-stable phenomenon has been investigated. Mode-averaged PIV was performed in a draw down wind tunnel with a test section cross-sectional area of 125mm2 using a tube array of 28 clear perspex tubes with a diameter of 13mm. The mode of each set of image pairs was determined by simultaneously capturing the images and gathering pressure data from the surface of the test section wall. Further tests were then conducted using two instrumented cylinders mounted in a test section with a cross section of 300×272mm using 28 tubes with a diameter of 38mm. It was found that at certain flow velocities, the pressure signals from each of the instrument cylinders were highly correlated. Using this data, the circumferential pressure distributions across the span of an instrumented cylinder were determined for each mode using pseudo modal decomposition (PMD).

A Study on the Inner Surface Pressure Distribution of Fluid in Ninety Degree Elbow Pipe

2015 ◽  
Vol 713-715 ◽  
pp. 34-38 ◽  
Author(s):  
Xiao Yang Lu ◽  
Hong Liang Zhu ◽  
Xiao Li Lu ◽  
Jin Ming Liu ◽  
Yong Zhou ◽  
...  
Keyword(s):  
High Pressure ◽  
Surface Pressure ◽  
Maximum Relative Error ◽  
Pressure Data ◽  
Simulation Data ◽  
Outlet Pressure ◽  
Axial Angle ◽  
Surface Pressure Distribution ◽  
Inner Surface ◽  
Fluent Software

On the premise of the simulation data for the inner fuild passing the elbow pipe by means of software named FLUENT and dimensional analysis, the formula modle of inner surface pressure for elbow pipes came up by analyzing the relationships among the inner surface pressure P ,the fluid outlet pressure P0 ,axial angle α, circular angle β and the degree of curvature k; Depending on the inner surface pressure data simulated under 150 kinds of conditions, the pressure formula was fitted by means of 1stOpt software; The verification results show that the calculated value by the formula matched with the value of simulation by FLUENT software very well, the maximum relative error was 0.004%, and the research conclusion layed the theoretical groundwork for the design of the high pressure and high velocity elbow.

Structures and Interactions Underlying Rotational Augmentation of Blade Aerodynamic Response

2003 ◽  
Author(s):  
S. Schreck ◽  
M. Robinson
Keyword(s):  
Surface Pressure ◽  
Normal Force ◽  
Unsteady Aerodynamics ◽  
Boundary Layer Separation ◽  
Time Dependent ◽  
Blade Surface ◽  
Pressure Data ◽  
Pressure Distributions ◽  
Standard Deviations ◽  
Tunnel Time

Blade rotation routinely and significantly augments aerodynamic forces during zero yaw HAWT operation. To better understand the flow physics underlying this phenomenon, time dependent blade surface pressure data were acquired from the NREL Unsteady Aerodynamics Experiment, a full-scale HAWT tested in the NASA Ames 80 ft × 120 Ft wind tunnel. Time records of surface pressures and normal force were processed to obtain means and standard deviations. Surface pressure means and standard deviations were analyzed to identify boundary layer separation and reattachment locations. Separation and reattachment kinematics were then correlated with normal force behavior. Results showed that rotational augmentation was linked to specific separation and reattachment behaviors, and to associated three-dimensionality in surface pressure distributions.

Rotational Augmentation of Horizontal Axis Wind Turbine Blade Aerodynamic Response

2002 ◽  
Author(s):  
S. Schreck ◽  
M. Robinson
Keyword(s):  
Wind Turbine ◽  
Surface Pressure ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Pressure Data ◽  
Aerodynamic Forces ◽  
Horizontal Axis Wind Turbine ◽  
Pressure Distributions ◽  
Rotating Blade ◽  
Wind Tunnel Data

Surface pressure data were acquired using the NREL Unsteady Aerodynamics Experiment, a full-scale horizontal axis wind turbine, which was erected in the NASA Ames 80 ft × 120 ft wind tunnel. Data were collected first for a stationary blade, and then for a rotating blade with the turbine disk at zero yaw. Analyses compared aerodynamic forces and surface pressure distributions under rotating conditions against analogous baseline data acquired from the stationary blade. This comparison allowed rotational modifications to blade aerodynamics to be characterized in detail. Rotating conditions were seen to dramatically amplify aerodynamic forces, and radically alter surface pressure distributions. These and subsequent findings will more fully reveal the structures and interactions responsible for these flow field enhancements, and help establish the basis for formalizing comprehension in physics based models.

Surface Pressures Developed on an Airfoil Undergoing Heaving and Pitching Motion

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
T. Lee ◽  
Y. Y. Su
Keyword(s):  
Phase Shift ◽  
Pressure Distribution ◽  
Surface Pressure ◽  
Cfd Validation ◽  
Surface Pressure Distribution ◽  
Pressure Distributions ◽  
Torsional Damping ◽  
Layer Flow ◽  
Open Archives ◽  
Naca 0012

The surface pressure distributions and flow patterns developed on and around a NACA 0012 airfoil undergoing heaving and pitching were investigated at Re = 3.6 × 104. Despite extensive investigations conducted by researchers elsewhere, the surface pressure measurements are, however, not readily available in the open archives, which are of importance not only in understanding the unsteady-airfoil boundary-layer flow but also for computational fluid dynamics (CFD) validation. Nevertheless, the results show that the behavior of the surface pressure distribution and the flow pattern of pure heaving closely resembled those of pure pitching. For combined heaving and pitching, the critical aerodynamic values (such as dynamic Cl,max, peak negative Cm, Cl-hysteresis and torsional damping) always exhibited a maximum value at phase shift ϕ = 0 deg. More interestingly, the ϕ = 180 deg phase shift produced a virtually unchanged surface pressure distribution over an entire combined motion cycle.

Static Pressure Characteristics in a Pin-Fin Channel With Shaped Cylindrical Pins

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
H. J. Pretorius ◽  
G. I. Mahmood ◽  
J. P. Meyer
Keyword(s):  
Thermal Performance ◽  
Static Pressure ◽  
Rectangular Channel ◽  
Diameter Ratio ◽  
Streamwise Direction ◽  
Array Configuration ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Pin Fins ◽  
Transfer Channels

Standard pin-fins in the heat transfer channels are shaped to reduce the pressure penalty and increase the thermal performance. The paper presents experimental results of the wall-static pressure distributions in an array of modified cylindrical short pin-fins in a channel. Standard cylindrical pin-fins with a smooth surface and a similar array configuration are also evaluated as a baseline for comparisons. The pin-fins with a height to diameter ratio of 1.28 are arranged in a staggered array consisting of 13 rows in a rectangular channel of aspect ratio 1:7.8. The cylindrical pins are modified by the machined slots at the tips. The slots in the pins are aligned in the streamwise direction. The static pressure distributions are measured on the endwall between the pin-rows and on the pin surface. The Reynolds number based on the channel hydraulic diameter ranges from 10,000 to 50,000. The slots in the pins reduce the friction factor and wall-static pressure drop between the pin-rows by up to 50%. The objectives of the investigation are to reduce the pressure penalty in the cylindrical pin-fin channel to provide increased thermal performance.

Boundary Layer State and Flow Field Structure Underlying Rotational Augmentation of Blade Aerodynamic Response

2003 ◽  
Vol 125 (4) ◽  
pp. 448-456 ◽  
Author(s):  
S. Schreck ◽  
M. Robinson
Keyword(s):  
Boundary Layer ◽  
Surface Pressure ◽  
Normal Force ◽  
Unsteady Aerodynamics ◽  
Boundary Layer Separation ◽  
Pressure Data ◽  
Horizontal Axis Wind Turbine ◽  
Pressure Distributions ◽  
Standard Deviations ◽  
Tunnel Time

Blade rotation routinely and significantly augments aerodynamic forces during zero yaw horizontal axis wind turbine (HAWT) operation. To better understand the flow physics underlying this phenomenon, time dependent blade surface pressure data were acquired from the National Renewable Energy Laboratory (NREL). Unsteady Aerodynamics Experiment (UAE), a full-scale HAWT tested in the NASA Ames 80-by-120-foot wind tunnel. Time records of surface pressures and normal force were processed to obtain means and standard deviations. Surface pressure means and standard deviations were analyzed to identify boundary layer separation and shear layer impingement locations. Separation and impingement kinematics were then correlated with normal force behavior. Results showed that rotational augmentation was linked to specific separation and impingement behaviors, and to associated three-dimensionality in surface pressure distributions.

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