Effects of Turbulence on the Pressure Distribution Around a Square Cylinder and Possibility of Reduction

1983 ◽  
Vol 105 (2) ◽  
pp. 140-145 ◽  
Author(s):  
K. C. S. Kwok
Keyword(s):  
Pressure Distribution ◽  
Turbulent Mixing ◽  
Peak Pressure ◽  
Shear Layers ◽  
Transverse Force ◽  
Force Characteristic ◽  
Square Cylinder ◽  
Pressure Coefficients ◽  
Prismatic Structure ◽  
Scale Turbulence

When a prismatic structure is subjected to air flow, especially at small angle of wind incidence, the separated shear layers may reattach onto the streamwise surface. The turbulent mixing in the shear layers and the extrainment of fluid results in highly fluctuating and strongly negative pressures under the reattaching shear layers. Wind tunnel tests were carried out to determine the pressure distribution around a square cylinder. It was found that an increase in turbulence, in particular fine scale turbulence, significantly altered the pressure distribution, the transverse force characteristic, and hence the galloping behavior of the square cylinder. When small vanes were fitted to the corners of the cylinder, and by maintaining a vent between the vane and the corner, the magnitude of the negative mean and peak pressure coefficients under the shear layer were substantially reduced.

Predictions of turbulent mixing in axisymmetric compressible shear layers

AIAA Journal ◽  
1992 ◽  
Vol 30 (6) ◽  
pp. 1529-1536 ◽  
Author(s):  
K. Viswanathan ◽  
P. J. Morris
Keyword(s):  
Turbulent Mixing ◽  
Shear Layers

Wind tunnel test on mean wind forces and peak pressure acting on ellipsoidal nacelles of wind turbine

2021 ◽  
pp. 0309524X2110445
Author(s):  
Hiroshi Noda ◽  
Takeshi Ishihara
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Peak Pressure ◽  
Wind Tunnel Test ◽  
Load Case ◽  
Wind Force ◽  
Pressure Coefficients ◽  
Force Coefficients ◽  
Design Load ◽  
Mean Pressure

Mean wind forces and peak pressures acting on ellipsoidal nacelles are investigated by wind tunnel tests. The wind force coefficients of the ellipsoidal nacelles for the wind turbine design and the peak pressure coefficients for the nacelle cover design are proposed based on the experimental data. The wind force coefficients are expressed as functions of yaw angles. The proposed formulas are compared with Eurocode, Germanischer Lloyd and ASCE7-16. It is found that the mean wind force coefficients for the wind turbine nacelles are slightly underestimated in Eurocode. The equivalent maximum and minimum mean pressure coefficients are proposed for use in Design Load Case 6.1 and Design Load Case 6.2 of IEC 61400-1. The peak pressure coefficients are derived using a quasi-steady theory. The proposed equivalent maximum and minimum mean pressure coefficients are much larger than those specified in Germanischer Lloyd.

Free Turbulent Shear Layers on Plug Nozzles

1977 ◽  
Vol 99 (2) ◽  
pp. 301-308
Author(s):  
C. J. Scott ◽  
D. R. Rask
Keyword(s):  
Turbulent Mixing ◽  
Schmidt Number ◽  
Error Function ◽  
Mixing Layer ◽  
Shear Layers ◽  
Turbulent Shear ◽  
Gas Chromatograph ◽  
Plug Nozzle ◽  
Turbulent Schmidt Number ◽  
Plug Nozzles

Two-dimensional, free, turbulent mixing between a uniform stream and a cavity flow is investigated experimentally in a plug nozzle, a geometry that generates idealized mixing layer conditions. Upstream viscous layer effects are minimized through the use of a sharp-expansion plug nozzle. Experimental velocity profiles exhibit close agreement with both similarity analyses and with error function predictions. Refrigerant-12 was injected into the cavity and concentration profiles were obtained using a gas chromatograph. Spreading factors for momentum and mass were determined. Two methods are presented to determine the average turbulent Schmidt number. The relation Sct = Sc is suggested by the data for Sc < 2.0.

Fluctuating lift and drag on a long cylinder of square cross-section in a smooth and in a turbulent stream

1966 ◽  
Vol 25 (3) ◽  
pp. 481-494 ◽  
Author(s):  
B. J. Vickery
Keyword(s):  
Cross Section ◽  
Large Scale ◽  
Circular Cross Section ◽  
Square Cylinder ◽  
Marked Influence ◽  
Fluctuating Pressure ◽  
Scale Turbulence ◽  
Lift And Drag ◽  
Long Cylinder

The paper presents the results of measurements of fluctuating lift and drag on a long square cylinder. The measurements include the correlation of lift along the cylinder and the distribution of fluctuating pressure on a cross-section. The magnitude of the fluctuating lift was found to be considerably greater than that for a circular cross-section and the spanwise correlation much stronger.It was found that the presence of large-scale turbulence in the stream had a marked influence on both the steady and the fluctuating forces. The most significant changes were at small angles of attack (%alpha; < 10°) and included a reduction in base suction and a decrease in fluctuating lift of about 50%.

WIND PRESSURE DISTRIBUTION ON LOW-RISE BUILDINGS WITH CYLINDRICAL ROOFS

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Astha Verma ◽  
Ashok Kumar Ahuja
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Open Circuit ◽  
Wind Pressure ◽  
Wind Loads ◽  
Wind Loading ◽  
Pressure Coefficients ◽  
Available Information

Wind is one of the important loads to be considered while designing the roofs of low-rise buildings. The structural designers refer to relevant code of practices of various countries dealing with wind loads while designing building roofs. However, available information regarding wind pressure coefficients on cylindrical roofs is limited to single span only. Information about wind pressure coefficients on multi-span cylindrical roofs is not available in standards on wind loads. Present paper describes the details of the experimental study carried out on the models of low-rise buildings with multi-span cylindrical roofs in an open circuit boundary layer wind tunnel. Wind pressure values are measured at many pressure points made on roof surface of the rigid models under varying wind incidence angles. Two cases namely, single-span and two-span are considered. The experimental results are presented in the form of contours of mean wind pressure coefficients. Results presented in the paper are of great use for the structural designers while designing buildings with cylindrical roofs. These values can also be used by the experts responsible for revising wind loading codes from time to time.

Experimental Investigation of the Wind Pressure Distribution and Wind Interference Effects on a Typical Tall Building

2013 ◽  
Vol 639-640 ◽  
pp. 444-451 ◽  
Author(s):  
Yi Li ◽  
Q.S. Li ◽  
K.L Ju
Keyword(s):  
Pressure Distribution ◽  
Wind Tunnel Test ◽  
Side Wall ◽  
Tall Buildings ◽  
Tall Building ◽  
Wind Pressure ◽  
Shielding Effect ◽  
Interference Effects ◽  
Large Cities ◽  
Pressure Coefficients

Most tall buildings are constructed in the prosperous center of large cities, where is inevitable to be surrounded by many interfering buildings. Wind interference effects among buildings should not be neglected. Therefore, it is necessary to investigate wind interference effects on such tall buildings. Based on the wind tunnel test of rigid model of a tall building, the wind pressure distribution on the building with interfering buildings around it has been researched, the contours of the mean and fluctuate wind pressure coefficients have also been presented. It has been found that shielding effect and channeling effect are significant in the wind interference effects on building. Wind pressure coefficients on side wall and leeward wall of a upstream building may be dramatically changed in case the wake boundary of the upstream building is interfered. The conclusions might be used as reference to structural design and plan.

The effect of initial conditions on the development of a free shear layer

1966 ◽  
Vol 26 (2) ◽  
pp. 225-236 ◽  
Author(s):  
P. Bradshaw
Keyword(s):  
Turbulent Mixing ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Initial Boundary ◽  
Shear Layers ◽  
Free Shear Layer ◽  
Turbulent Mixing Layer ◽  
Free Shear Layers ◽  
Final Approach ◽  
Reynolds Number Effects

The distance between the separation point and the final approach to a fully developed turbulent mixing layer is found to be of the order of a thousand times the momentum-deficit thickness of the initial boundary layer, whether the latter be laminar or turbulent. There are correspondingly large shifts in the virtual origin of the mixing layer, resulting in spurious Reynolds-number effects which cause considerable difficulties in tests of model jets or blunt-based bodies, and which are probably responsible for the disagreements over the influence of Mach number on the development of free shear layers. These effects are explained.

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