Observations of the wind tunnel blockage effects on the mean pressure distributions around rectangular prisms in smooth and grid turbulent flows (original) (raw)
Related papers
The effects of turbulence on the pressure distribution around a rectangular prism
Journal of Wind Engineering and Industrial Aerodynamics, 1998
Pressure fields around a rectangular prism were studied using a new turbulence-generation technique. Employing jets blowing laterally to the main flow and stationary obstacles, the technique generates turbulent flows of varying scales. Results reported here constitute the first stage in a study of the effects of turbulence on the aeroelastic stability of long-span bridges. Past research in bridge stability has shown inconclusive results with respect to the scales of turbulence. Measurements were thus conducted in a host of flows holding the turbulence intensity constant while varying the integral scale. The integral scales of the incident flow had significant effects on the flow structure resulting in changes in the mean, rms, and negative peak pressure distributions.
Predicting extreme values of wall-pressure on a tall building is a crucial step in the design process of the building but can prove to be very challenging. This paper describes wind tunnel study with a well-defined mean velocity gradient and turbulent characteristics. The experiments were performed in the NSA wind tunnel at CSTB, Nantes, France, at a 1:300 scale. The tower building was modeled by a wall-mounted prism of square crosssection (dimensions: 10 cm 10 cm 49 cm) equipped with 265 pressure taps used to measure the unsteady pressure distribution on the model walls. Comparisons between different measurement methods of the global wind load are presented. Differences between lateral and longitudinal loads are discussed in link with the physics of the flow.
Journal of Wind Engineering and Industrial Aerodynamics, 2000
Roughness elements are usually added in boundary layer wind tunnels to enhance the energy of certain turbulence scales and their range. In this work, flow characteristics in three different configurations of roughness elements are examined. Orthonormal wavelets are applied to velocity records in order to quantify the percentage of energy contribution of each scale to the total energy and the intermittency of high-energy events. The effects of such variations in turbulence scale characteristics on variations of peak and mean negative pressure coefficients at different locations on a 1 : 50 scale model of the Wind Engineering Research Field Laboratory (WERFL) of Texas Tech are also determined. The results show that enhancing the energy of the smaller turbulence scales relative to that of the larger scales and in particular the energy of the intermittent events have significant effects on mean and peak pressures observed on the top surface of a prism. #
The e/ects of turbulence on the pressure distribution around a rectangular prism
1998
Pressure fields around a rectangular prism were studied using a new turbulence-generation technique. Employing jets blowing laterally to the main flow and stationary obstacles, the technique generates turbulent flows of varying scales. Results reported here constitute the first stage in a study of the effects of turbulence on the aeroelastic stability of long-span bridges. Past research in bridge stability has shown inconclusive results with respect to the scales of turbulence. Measurements were thus conducted in a host of flows holding the turbulence intensity constant while varying the integral scale. The integral scales of the incident flow had significant effects on the flow structure resulting in changes in the mean, rms, and negative peak pressure distributions.
Archives of Civil and Mechanical Engineering, 2011
The results of measurements of 2-D flow around rectangular prisms of square and rectangle crosssections in wind tunnel are presented in this paper. The results include pressure and standard deviation distributions over the model walls, components of velocity vectors and statistical moments for fluctuations of the velocity in the wind tunnel measuring space. The arrangements of models and the range of measurements have been matched in order to the results could be used to the calibration of the numerical turbulence model and to the verification of computer calculations for the civil engineering problems. The values of parameters have been presented in graphs and subsequently used in a comparative analysis of the flows around both models.
The Interference Effect of Surrounding Roughness on Wind Pressures of Rectangular Prism
2000
Systematic experiments were conducted in a wind tun nel in order to find the effect of typical building arrangements on the wind-induce d pressures, the primary goal is to better understand and quantify the effect of surrounding b locks on wind pressures of central rectangular prism, especially for those magnified s ituations of peak pressures which is most important for
Pressures on a surface-mounted rectangular prism under varying incident turbulence
Journal of Wind Engineering and Industrial Aerodynamics, 2003
The pressure and load coefficients obtained from two groups of eight pressure taps on the upper surface of a surface-mounted prism are characterized in terms of their mean, rms, peak, probability distribution, peak correlations and durations. The prism is a 1:50 scale model of the WERFL experimental building at Texas Tech University. Results obtained with flows generated over seven different wind tunnel floor-roughness configurations in the boundary layer wind tunnel at Clemson University cover a wide range of turbulence intensities. The results presented include the spatial variation of the peak pressure and peak load coefficients, and their variations with incident turbulence. The stochastic characteristics of the peak coefficients are also addressed here. The results reveal that the distribution of the peak coefficients is in general well established by the Extreme Value Type I (Gumbel) distribution. Conditional sampling is employed to study the duration as well as the space and space-time correlations of the peaks. Analysis of the peaks reveals that those with the larger magnitudes are generally of longer duration. r
Journal of Fluids and Structures, 2009
The results are described of measurements of the mean and fluctuating forces acting on low aspect-ratio triangular prisms placed vertically on a plane, having isosceles triangular cross-section with 60∘60∘ or 90∘90∘ apex angles and aspect ratios ranging from 1.01.0 to 3.03.0. The tests are carried out in a wind-tunnel by varying the wind direction, θθ, between 0∘0∘ and 180∘180∘, at a Reynolds number Re ≃1.2×105≃1.2×105. Furthermore, for the model with apex angle of 60∘60∘ and aspect ratio 3.03.0, flow visualizations with tufts and hot-wire measurements are performed, which permit to characterize the wake morphology as a function of wind direction and to assess that an alternate vortex shedding always exists, with a frequency that is roughly inversely proportional to the wake width. The force measurements show that large variations in the mean values of the drag and cross-flow forces occur by varying θθ, in strict correspondence with changes in wake flow features. The intensity of the fluctuating cross-flow forces, directly connected with vortex shedding, is found to vary significantly with flow orientation and aspect ratio, and to be approximately proportional to the streamwise projection of the body surface immersed in the separated wake. Finally, an increase in vortex shedding frequency is generally found with decreasing aspect ratio.
The Steady Wake of a Wall-Mounted Rectangular Prism with a Large-Depth-Ratio at Low Reynolds Numbers
Energies, 2021
The wakes of wall-mounted small (square) and large (long) depth-ratio rectangular prisms are numerically studied at Reynolds numbers of 50–250. The large depth-ratio significantly alters the dominance of lateral secondary flow (upwash and downwash) in the wake due to the reattachment of leading-edge separated flow on the surfaces of the prism. This changes the wake topology by varying the entrained flow in the wake region and changing the distribution of vorticity. Thus, the magnitude of vorticity significantly decreases by increasing the prism depth-ratio. Furthermore, the length of the recirculation region and the orientation of near wake flow structures are altered for the larger depth-ratio prism compared to the square prism. Drag and lift coefficients are also affected due to the change of pressure distributions on the rear face of the prism and surface friction force. This behavior is consistently observed for the entire range of Reynolds numbers considered here. The wake size...