Investigations on simulated near-surface atmospheric boundary layer (ABL) in an open-jet facility are carried out by conducting experimental tests on small-scale models of low-rise buildings. The objectives of the current study are: (1) to determine the optimal location of test buildings from the exit of the open-jet facility, and (2) to investigate the scale effect on the aerodynamic pressure characteristics. Based on the results, the newly built open-jet facility is well capable of producing mean wind speed and turbulence profiles representing open-terrain conditions. The results show that the proximity of the test model to the open-jet governs the length of the separation bubble as well as the peak roof pressures. However, test models placed at a horizontal distance of 2.5H (H is height of the wind field) from the exit of the open-jet, with a width that is half the width of the wind field and a length of 1H, have consistent mean and peak pressure coefficients when compared with available results from wind tunnel testing. In addition, testing models with as large as 16% blockage ratio is feasible within the open-jet facility. This reveals the importance of open-jet facilities as a robust tool to alleviate the scale restrictions involved in physical investigations of flow pattern around civil engineering structures. The results and findings of this study are useful for putting forward recommendations and guidelines for testing protocols at open-jet facilities, eventually helping the progress of enhanced standard provisions on the design of low-rise buildings for wind.
more »
« less
Exploring the impact of vertically separated flows on wind loads of multi-level structures
The complex dynamics of vertically separated flows pose a significant challenge when it comes to assessing the wind loads on multi-level structures, demanding a nuanced understanding of the intricate interplay between atmospheric conditions and architectural designs. Previous studies and wind loading standards provide insufficient guidance for designing wind pressures on multi-level buildings. The behavior of wind around perpendicularly attached surfaces is not quite similar to that of individual flat roofs or walls. When a body is composed of several surfaces with right or oblique angles, the separated flow from surfaces and their interactions will cause complex flow patterns around each surface. A wind tunnel experimental study was carried out on bluff bodies with attached flat plates and other adjacent bluff bodies with different heights to examine the wind-induced pressures on such complex shapes. Mean and peak pressure coefficients were measured to determine the flow interaction patterns and location of localized peak pressures. The results were compared to the Tokyo Polytechnic University Aerodynamic Database of isolated low-rise buildings without eaves. The research findings indicated that there was a noteworthy disparity between the minimum and maximum values and locations of peak pressures on both the wall and roof surfaces of the models used in this study, as compared to the results obtained by the Tokyo Polytechnic University. Moreover, the study conceivably pointed to the difference between the peak negative and positive pressure coefficient locations with the ASCE 7-22 wind loading zones. The peak suction zones were affected by the combined flows at perpendicular faces, and as a result, different wind load zones were obtained dissimilar to those introduced by ASCE 7-22. Wind loading standards may need to be modified to account for the wind pressures on complex building structures with an emphasis on the location of the peak negative pressure zones.
more » « less- Award ID(s):
- 1841503
- NSF-PAR ID:
- 10486061
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Physics
- Volume:
- 11
- ISSN:
- 2296-424X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract. Research often neglects historic and ageing infrastructure when investigating the impact of extreme wind loading and structural strengthening. This is exemplified by the ASCE 7-22 standard in the US that prescribes design loads for tornado hazard, which currently does not apply to Risk Categories (RC) 1 and 2, comprising a significant proportion of historic structures. After a disaster, analyzing these structures numerically can be difficult due to their complex geometries, use of multiple construction materials, and alterations to the original structure. This study aimed to digitally document and evaluate the damage caused by the Midwest Tornado in Kentucky in December 2021, specifically focusing on the historic downtown of Mayfield, KY. Building data was gathered using various devices, such as Unmanned Aerial Vehicle’s, LiDARs, and cameras, and converted into finite element meshes using the open-source software Cloud2FEM. Multiple meshes for the historic post office building in Mayfield, KY, was generated using varied rules within Cloud2FEM. These meshes were then simulated using Abaqus to qualitatively assess the stress concentrations observed under tornadic loading calculated using the ASCE7-22.
-
One of the key factors in simulating realistic wall-bounded flows at high Reynolds numbers is the selection of an appropriate turbulence model for the steady Reynolds Averaged Navier–Stokes equations (RANS) equations. In this investigation, the performance of several turbulence models was explored for the simulation of steady, compressible, turbulent flow on complex geometries (concave and convex surface curvatures) and unstructured grids. The turbulence models considered were the Spalart–Allmaras model, the Wilcox k- ω model and the Menter shear stress transport (SST) model. The FLITE3D flow solver was employed, which utilizes a stabilized finite volume method with discontinuity capturing. A numerical benchmarking of the different models was performed for classical Computational Fluid Dynamic (CFD) cases, such as supersonic flow over an isothermal flat plate, transonic flow over the RAE2822 airfoil, the ONERA M6 wing and a generic F15 aircraft configuration. Validation was performed by means of available experimental data from the literature as well as high spatial/temporal resolution Direct Numerical Simulation (DNS). For attached or mildly separated flows, the performance of all turbulence models was consistent. However, the contrary was observed in separated flows with recirculation zones. Particularly, the Menter SST model showed the best compromise between accurately describing the physics of the flow and numerical stability.more » « less
-
ABSTRACT Magnetic fields provide an important probe of the thermal, material, and structural history of planetary and sub-planetary bodies. Core dynamos are a potential source of magnetic fields for differentiated bodies, but evidence of magnetization in undifferentiated bodies requires a different mechanism. Here, we study the amplified field provided by the stellar wind to an initially unmagnetized body using analytic theory and numerical simulations, employing the resistive magnetohydrodynamic AstroBEAR adaptive mesh refinement multiphysics code. We obtain a broadly applicable scaling relation for the peak magnetization achieved once a wind advects, piles-up, and drapes a body with magnetic field, reaching a quasi-steady state. We find that the dayside magnetic field for a sufficiently conductive body saturates when it balances the sum of incoming solar wind ram, magnetic, and thermal pressures. Stronger amplification results from pile-up by denser and faster winds. Careful quantification of numerical diffusivity is required for accurately interpreting the peak magnetic field strength from simulations, and corroborating with theory. As specifically applied to the Solar system, we find that early solar wind-induced field amplification is a viable source of magnetization for observed paleointensities in meteorites from some undifferentiated bodies. This mechanism may also be applicable to other Solar system bodies, including metal-rich bodies to be visited in future space missions such as the asteroid (16) Psyche.more » « less
-
The interaction between upstream flow disturbance generators and downstream aeroelastic structures has been the focus of several recent studies at North Carolina State University. Building on this work, which observed the modulation of limit cycle oscillations (LCOs) in the presence of vortex wakes, this study examines the design and validation of a novel disturbance generator consisting of an oscillating cylinder with an attached splitter plate. Analytical design of the bluff body was performed based on specific flow conditions which produced LCO annihilation in previous studies. Computational fluid dynamics simulations and experimental wind tunnel tests were used to validate the ability of the new disturbance generator to produce the desired wake region. Future work will see the implementation of this novel design in conjunction with aeroelastic structures in an effort to modulate and control LCOs, including the excitation and annihilation thereof.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fphy.2023.1225817
