Mean pressure coefficient distributions over hyperbolic paraboloid roof and canopy structures with different shape parameters in a uniform flow with very small turbulence

2020 ◽  
Vol 205 ◽  
pp. 110043 ◽  
Author(s):  
Jimmy Colliers ◽  
Joris Degroote ◽  
Marijke Mollaert ◽  
Lars De Laet
Keyword(s):  
Pressure Coefficient ◽  
Uniform Flow ◽  
Shape Parameters ◽  
Hyperbolic Paraboloid ◽  
Mean Pressure

Pressure modes for hyperbolic paraboloid roofs

2020 ◽  
Vol 7 (1) ◽  
pp. 226-246
Author(s):  
Fabio Rizzo ◽  
Cristoforo Demartino
Keyword(s):  
Pressure Coefficient ◽  
Measured Signal ◽  
Hyperbolic Paraboloid ◽  
Pressure Coefficients ◽  
Truncated Svd ◽  
Mean Pressure ◽  
Vertical Displacements ◽  
Value Decomposition ◽  
Experimental Pressure ◽  
Polynomial Surface

AbstractThis paper presents a study on Singular Value Decomposition (SVD) of pressure coefficients hyperbolic parabolic roofs. The main goal of this study is to obtain pressure coefficient maps taking into account spatial non-uniform distribution and time-depending fluctuations of the pressure field. To this aim, pressure fields are described through pressure modes estimated by using the SVD technique. Wind tunnel experimental results on eight different geometries of buildings with hyperbolic paraboloid roofs are used to derive these pressure modes. The truncated SVD approach was applied to select a sufficient number of pressure modes necessary to reconstruct the measured signal given an acceptable difference. The truncated pressure modes are fitted through a polynomial surface to obtain a parametric form expressed as a function of the hyperbolic paraboloid roof geometry. The superpositions of pressure (envelopes) for all eight geometry were provided and used to modify mean pressure coefficients, to define design load combinations. Both symmetrical and asymmetrical pressure coefficient modes are used to estimate the wind action and to calculate the vertical displacements of a cable net by FEM analyses. Results clearly indicate that these load combinations allow for capturing large downward and upward displacements not properly predicted using mean experimental pressure coefficients.

scholarly journals Mode Pressure Coefficient Maps as an Alternative to Mean Pressure Coefficient Maps for Non-Gaussian Processes: Hyperbolic Paraboloid Roofs as Cases of Study

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 64 ◽  
Author(s):  
Alberto Viskovic
Keyword(s):  
Gaussian Processes ◽  
Pressure Coefficient ◽  
Wind Tunnels ◽  
Wind Tunnel Experiments ◽  
Hyperbolic Paraboloid ◽  
Mean Values ◽  
Parabolic Shape ◽  
Mean Pressure ◽  
The Mean ◽  
Non Gaussian

Wind tunnel experiments are necessary for geometries that are not investigated by codes or that are not generally and parametrically investigated by literature. One example is the hyperbolic parabolic shape mostly used for cable net roofs, for which codes do not provide pressure coefficients and literature only gives mean, maxima, and minima pressure coefficient maps. However, most of pressure series acquired in wind tunnels on the roof are not Gaussian processes and, for this reason, the mean values are not precisely representative of the process. The paper investigates the ratio between mean and mode of pressure coefficient series acquired in wind tunnels on buildings covered with hyperbolic paraboloid roofs with square plans. Mode pressure coefficient maps are given as an addition to traditional pressure coefficient maps.

Vortex shedding from bluff bodies in a shear flow

1973 ◽  
Vol 60 (2) ◽  
pp. 401-409 ◽  
Author(s):  
D. J. Maull ◽  
R. A. Young
Keyword(s):  
Shear Flow ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Uniform Flow ◽  
Base Pressure ◽  
Longitudinal Vortex ◽  
Bluff Bodies ◽  
Stream Direction

Experiments are described in which the vortex shedding from a bluff body and the base pressure coefficient have been measured in a shear flow. It is shown that the shedding breaks down into a number of spanwise cells in each of which the frequency is constant. The division between the cells is thought to be marked by a longitudinal vortex in the stream direction and this is supported by evidence from experiments where a longitudinal vortex was generated in an otherwise uniform flow.

Flow Characteristics of a Bluff Body Cut From a Circular Cylinder

1997 ◽  
Vol 119 (2) ◽  
pp. 453-454 ◽  
Author(s):  
S. Aiba ◽  
H. Watanabe
Keyword(s):  
Circular Cylinder ◽  
Drag Coefficient ◽  
Flow Velocity ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Angular Position ◽  
Flow Characteristics ◽  
Uniform Flow ◽  
Base Pressure ◽  
Singular Flow

This is a report on an investigation of the flow characteristics of a bluff body cut from a circular cylinder. The volume removed from the cylinder is equal to d/2(1 − cos θs), where d and θs are the diameter and the angular position (in the case of a circular cylinder, θs, = 0 deg), respectively. θs, ranged from 0 deg to 72.5 deg and Re (based on d and the upstream uniform flow velocity U∞) from 2.0 × 104 to 3.5 × 104. It is found that a singular flow around the cylinder occurs at around θs = 53 deg when Re > 2.5 × 104, and the base pressure coefficient (−Cpb,) and the drag coefficient CD take small values compared with those for otherθs.

Near-Bed Flow Mechanisms Around a Circular Marine Pipeline Close to a Flat Seabed in the Subcritical Flow Regime Using a k-ɛ Model

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Muk Chen Ong ◽  
Torbjørn Utnes ◽  
Lars Erik ◽  
Dag Myrhaug ◽  
Bjørnar Pettersen
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Flow Regime ◽  
Boundary Layer Thickness ◽  
Friction Velocity ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Mean Pressure ◽  
Flow Mechanisms ◽  
The Mean

Flow mechanisms around a two-dimensional (2D) circular marine pipeline close to a flat seabed have been investigated using the 2D unsteady Reynolds-averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k-ɛ model. The Reynolds number (based on the free stream velocity and cylinder diameter) ranges from 1 × 104 to 4.8 × 104 in the subcritical flow regime. The objective of the present study is to show a thorough documentation of the applicability of the k-ɛ model for engineering design within this flow regime by means of a careful comparison with available experimental data. The inflow boundary layer thickness and the Reynolds numbers in the present simulations are set according to published experimental data, with which the simulations are compared. Detailed comparisons with the experimental data for small gap ratios are provided and discussed. The effects of the gap to diameter ratio and the inflow boundary layer thickness have been studied. Although under-predictions of the essential hydrodynamic quantities (e.g., time-averaged drag coefficient, time-averaged lift coefficient, root-mean-square fluctuating lift coefficient, and mean pressure coefficient at the back of the pipeline) are observed due to the limitation of the turbulence model, the present approach is capable of providing good qualitative agreement with the published experimental data. The vortex shedding mechanisms have been investigated, and satisfactory predictions are obtained. The mean pressure coefficient and the mean friction velocity along the flat seabed are predicted reasonably well as compared with published experimental and numerical results. The mean seabed friction velocity at the gap is much larger for small gaps than for large gaps; thus, the bedload sediment transport is much larger for small gaps than for large gaps.

Gene-expression programming for the assessment of surface mean pressure coefficient on building surfaces

2020 ◽  
Vol 13 (2) ◽  
pp. 401-418 ◽  
Author(s):  
Monalisa Mallick ◽  
Abinash Mohanta ◽  
Awadhesh Kumar ◽  
Kanhu Charan Patra
Keyword(s):  
Gene Expression ◽  
Gene Expression Programming ◽  
Pressure Coefficient ◽  
Mean Pressure ◽  
Building Surfaces

scholarly journals Experimental evidence dynamic pressures reduction on plunge pool floors downstream flip bucket for increasing downstream face slopes

2020 ◽  
Vol 20 (5) ◽  
pp. 1834-1846 ◽  
Author(s):  
Mehdi Karami Moghadam ◽  
Ata Amini ◽  
Hasan Hosseini
Keyword(s):  
Extreme Values ◽  
International Association ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Laboratory Data ◽  
Bottom Wall ◽  
Downstream Face ◽  
Maximum Value ◽  
Mean Pressure

Abstract In this research, the ejecting jet from a flip bucket downstream of a chute spillway was simulated using physical modeling. The effects of influencing parameters upon fluctuations and extreme values of dynamic pressure were investigated. The angles of 0°, 30°, 45°, and 60° were adopted for the mobile bottom wall. The discharges were set as 67, 86, 161, and 184 litre/s and the depths of water cushion on the mobile bottom wall were set as 0, 15, 30, and 45 cm. The method suggested by Castillo for computation of fluctuating coefficient of dynamic pressure (see Castillo (2007) Pressure characterization of undeveloped and developed jets in shallow and deep pool. Proceedings of the Congress-International Association for Hydraulic Research32 (2), 645) was validated via the laboratory data. The results showed that the increase in water cushion depth downstream has led to a decrease in mean pressure and in pressure fluctuations. The analyses showed that the fluctuating pressure coefficient was a function of water cushion depth, and its maximum value was taken when there was a water cushion on the mobile bottom wall. With an increase in discharge and mobile bottom wall angle, the maximum value of the fluctuating coefficient occurred in less water cushion depth. Moreover, with the growth of discharge, the maximum positive and negative fluctuations of the pressure increased first and then decreased.

scholarly journals Wind structure influence on pressure coefficient distribution on the surface of circular cylinder of the diameter 20 cm

2012 ◽  
Vol 10 (1) ◽  
pp. 081-092
Author(s):  
Tomasz Lipecki ◽  
Jarosław Bęc ◽  
Ewa Błazik-Borowa
Keyword(s):  
Circular Cylinder ◽  
Vertical Profile ◽  
Pressure Coefficient ◽  
Coefficient Distribution ◽  
Wind Structure ◽  
Power Spectral ◽  
Mean Pressure ◽  
Mean Wind Speed ◽  
Spectral Density Functions ◽  
D 20

The paper deals with results and analyses of the model investigations which were performed in wind tunnel and were focused on the flow around single circular cylinder. Presented results are related to variations in the distribution of the normalized mean pressure coefficient on the surface of the model as well as its standard deviation. Sic cases of the approaching flow were taken into consideration. The flow was described by vertical profile of the mean wind speed, vertical profile of the intensity of turbulence, and power spectral density functions. The height and dimension of the model were respectively equal: H = 100 cm, D = 20 cm. Selected results of measurements have been shown in the paper as the effect of these experiments.

scholarly journals Effects of Side Ratio on Wind-Induced Pressure Distribution on Rectangular Buildings

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
J. A. Amin ◽  
A. K. Ahuja
Keyword(s):  
Pressure Distribution ◽  
Incidence Angle ◽  
Pressure Coefficient ◽  
Side Wall ◽  
Wind Pressure ◽  
Surface Pressure Distribution ◽  
Side Ratio ◽  
Building Models ◽  
Mean Pressure ◽  
Wind Pressures

This paper presents the results of wind tunnel studies on 1 : 300 scaled-down models of rectangular buildings having the same plan area and height but different side ratios ranging from 0.25 to 4. Fluctuating values of wind pressures are measured at pressure points on all surfaces of models and mean, maximum, minimum, and r.m.s. values of pressure coefficients are evaluated. Effectiveness of the side ratios of models in changing the surface pressure distribution is assessed at wind incidence angle of 0° to 90° at an interval of 15°. Side ratio of models has considerable effects on the magnitude and distribution of wind pressure on leeward and sidewalls but it has very limited effect on windward walls at wind incidence angle of 0°. For building models with constant cross section, change in side ratio does not significantly affect the general magnitude of peak pressures and peak suctions, but rather the wind angle at which they occur. The regression equation is also proposed to predict the mean pressure coefficient on leeward wall and side wall of rectangular models having different side ratios at 0° wind incidence angle.

Interference effects of three consecutive wall-mounted cubes placed in deep turbulent boundary layer

2014 ◽  
Vol 756 ◽  
pp. 165-190
Author(s):  
Hee Chang Lim ◽  
Masaaki Ohba
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Coefficient ◽  
Azimuth Angle ◽  
Pressure Variation ◽  
Interference Effects ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Mean Pressure ◽  
The Mean

AbstractIn this study we undertook various calculations of the turbulent flow around a building in close proximity to neighbouring obstacles, with the aim of gaining an understanding of the velocity and the surface-pressure variations with respect to the azimuth angle of wind direction and the gap distance between the obstacles. This paper presents the effects of flow interference among consecutive cubes for azimuth angles of $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\theta = 0$, 15, 30, and $45^{\circ }$ and gap distances of $G = 0.5{h}, 1.0{h}, 1.5{h}$, and $\infty $ (i.e. a single cube), where $h$ is the cube height, placed in a turbulent boundary layer. A transient detached eddy simulation (DES) was carried out to calculate the highly complicated flow domain around the three wall-mounted cubes to observe the fluctuating pressure, which substantially contributes to the suction pressure when there is separation and reattachment around the leading and trailing edges of the cubes. In addition, the results indicate that an increasing azimuth angle increases the pressure variation on the centre cube of the three parallel-aligned cubes. The mean pressure variation can even change from negative to positive on the side face. Owing to interference effects, the mean pressure coefficient of the centre cube of the three parallel-aligned cubes was generally lower than the coefficient of the single cube and tended to increase depending on the gap distance. Furthermore, when the three consecutive cubes are in a tandem arrangement, the gap distance has little influence on the first cube but results in significant interference effects on the second and third cubes.

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