Conventional Boundary Layer Research Articles

Sensitivity of simulated wind power under diverse spatial scales and multiple terrains using the weather research and forecasting model

During the process of grid refinement and downscaling in the Weather Research and Forecasting (WRF) model, the horizontal grid resolution inevitably enters the realm of uncertainty known as the Terra Incognita. Within this region, conventional mesoscale Planetary Boundary Layer schemes fail to achieve the desired optimized outcomes following grid refinement. This study conducted a series of sensitivity analyses to explore the performance of the WRF model in simulating wind speed and direction at different spatial scales under various conditions. By comparing 10 min mean values for flat and complex terrains and then evaluating the performance of the model using statistical scoring. The results indicate that for wind resource assessment, the mesoscale boundary exceeds the height of the atmospheric boundary layer during the simulation period. For flat terrains, nesting is not recommended. Instead, nesting into Terra Incognita and microscale is preferred for complex terrains. The model demonstrates overall accuracy in wind direction estimation but tends to underestimate wind speed. Notably, the accuracy of simulations at 70 m above ground is higher than that at 10 m. The assessment of wind speed and direction exhibits distinct patterns across various wind speed ranges, wind direction, and atmospheric stabilities.

Influence of heterogeneous catalysis on aerothermodynamics at hypersonic speeds based on gas-interface-solid coupling simulation

Heterogeneous catalysis plays an important role in causing the aerodynamic heating surge in the hypersonic nonequilibrium flow/thermal protection material interactions for high-speed aircrafts. To model the flow/material interaction problem, a gas-interface-solid coupling method for heterogeneous catalysis was established by introducing interface balance relation into the coupling framework of nonequilibrium Navier-Stokes equations and thermal conduction equation. The influence of coating heterogeneous catalysis on heat transfer into the heat shield of a blunt body was then numerically investigated to reveal the catalysis-induced aerothermodynamics. The coupling simulation results reveal that the codominant role of material mediated catalysis and gaseous reactions on boundary layer and their induced near-wall evolutions are the main features of the chemically reacting boundary layer that differ from the conventional boundary layer theory. It was found that catalytically inert coatings can weaken the local aerodynamic heating due to the low activity of local catalysis and enhance the downstream catalytic heating through driving atomic species to the downstream region. Appropriate layouts of thermal protection coatings can make full use of the nature of catalytic exothermicity to effectively manage hypersonic flow and catalysis-induced heat-transfer characteristics for the lightweight and low-redundancy thermal protection designs of future spacecraft.

Sound radiated by three-dimensional discontinuities immersed in a turbulent boundary layer

Measurements of the far-field sound from two types of three-dimensional discontinuities – swept forward-facing steps and a circular embossment – immersed in a low Mach number (M<0.18) turbulent boundary layer were made. The discontinuity height in each case was smaller than the height of the approaching, undisturbed boundary layer and the Reynolds number based on the discontinuity height ranged between 8300–92,000. The swept forward-facing steps were immersed in a wall-jet boundary layer, whereas the embossment was placed in a conventional boundary layer. For the embossment, measurements of surface pressure fluctuations were also performed beneath the separated flow on the vertical and the downstream surfaces. The wall-jet measurements show that the far-field sound from swept forward-facing step scales on the step-normal component of the boundary-layer edge velocity. The far-field sound from the circular embossment is qualitatively similar to that from a forward-facing step of the same height, a fact which is also reflected in the surface pressure fluctuation measurements. The step-normal velocity scaling obtained for the swept forward-facing steps was combined with an existing prediction formula for the sound radiated by a forward-facing step to yield a straight-forward prediction formula for the embossment noise. The prediction formula shows good agreement with the measured sound spectra if it is assumed that the dominant source for the embossment is the separation/reattachment region concentrated in the forward arc of the embossment. This assumption is supported by oil flow visualization which shows that the separated flow region is concentrated between approximately ±45°on either side of the spanwise center.

A new analytical model for wind flow in canopies

Analytical modeling of canopy layer wind flow is commonly used to study local air transport around plant or building canopies. The models also help in the estimation of canopy boundary drag contribution for the atmospheric scale flow. Existing canopy layer airflow models exhibit limitations, especially for low packing density scenarios. In the current study, a new canopy layer airflow model is derived using analytical procedures for flow obstacles with different canopy roughness densities. The derivation procedure considers an assumed arbitrary relationship between the turbulent stress and canopy layer mean velocity profile, that has subsequently been verified using known boundary conditions. In addition, first-principles are combined with turbulence mixing and eddy diffusivity assumptions to obtain the analytical model for flow near obstacles of various packing densities. The new analytical model better predicts the velocity profile for a wider density range. The model also gives near ground velocity up to the accuracy of the conventional atmospheric boundary layer (ABL) model and matches the ABL conditions in the absence of canopies. The analytical model is validated through comparative assessments with experimental data extracted from literature. The analytical model is expected to help better understand flow through and/or over urban and vegetative canopies.

Effect of Scale-Aware Planetary Boundary Layer Schemes on Tropical Cyclone Intensification and Structural Changes in the Gray Zone

AbstractHorizontal grid spacings of numerical weather prediction models are rapidly approaching O (1 km) and have become comparable with the dominant length scales of flows in the boundary layer; within such “gray-zone”, conventional planetary boundary layer (PBL) parameterization schemes start to violate basic design assumptions. Scale-aware PBL schemes have been developed recently to address the gray-zone issue. By performing WRF simulations of Hurricane Earl (2010) at sub-kilometer grid spacings, this study investigates the effect of the scale-aware Shin-Hong (SH) scheme on the tropical cyclone (TC) intensification and structural changes in comparison to the non-scale-aware YSU scheme it is built upon. Results indicate that SH tends to produce a stronger TC with a more compact inner core than YSU. At early stages, the scale-aware coefficients in SH gradually decrease as the diagnosed boundary layer height exceeds the horizontal grid spacing. This scale-aware effect is most prominent for the nonlocal subgrid-scale vertical turbulent fluxes, in the non-precipitation regions radially outside of the convective rainband, and from the early stage through the middle of rapid intensification (RI) phase. Both the scale awareness and different parameterization of the nonlocal turbulent heat flux in SH reduce the parameterized vertical turbulent mixing, which further induces stronger radial inflows and helps retain more water vapor in the boundary layer. The resulting stronger moisture convergence and diabatic heating near the TC center account for the faster inner-core contraction before RI onset and the higher intensification rate during the RI period. Potential issues of applying these two PBL schemes in TC simulations and suggestions for improvements are discussed.

A comparative study of heat transfer characteristics of wall jet with boundary layer transition using six low-Reynolds number k–ε models

A Low-Reynolds Number (LRN) k–ε model can well simulate the transition characteristics of the momentum boundary layer, but so far, there are few studies on the influence of boundary layer transition on heat transfer characteristics by using the LRN k–ε model. Due to the larger degree of flexibility and controllability of flow parameters than the conventional boundary layer, a wall jet is an ideal flow configuration to research the transition of the boundary layer. To investigate the performance of the LRN k–ε model in simulating the heat transfer characteristics of the wall jet with boundary layer transition, six versions of LRN k–ε models are used to simulate a three-dimensional wall jet with boundary layer transition and the computational results were compared with experimental data. It is found that the Abe–Kondoh–Nagano (AKN) and Yang–Shih (YS) models can accurately simulate the flow field and heat transfer of the laminar boundary layer due to the use of the Kolmogorov scale in the developing region. Compared with the YS model, the AKN model is capable of predicting the influence of boundary layer transition on the heat transfer process in good agreement with experimental results over the whole domain. From the calculation results, it is found that Abid and Change and Hsieh and Chen models are more appropriate for simulating the heat transfer in the fully turbulent region of the wall jet. The damping function fµ of the Lam–Bremhorst and Launder–Sharma models approaches a constant value near the wall, which does not meet the wall limiting conditions and leads to a negative impact on the simulation of heat transfer near the wall.

Hydrodynamics of two-dimensional compressible fluid with broken parity: Variational principle and free surface dynamics in the absence of dissipation

We consider an isotropic compressible non-dissipative fluid with broken parity subject to free surface boundary conditions in two spatial dimensions. The hydrodynamic equations describing the bulk dynamics of the fluid as well as the free surface boundary conditions depend explicitly on the parity breaking non-dissipative odd viscosity term. We construct a variational principle in the form of an effective action which gives both bulk hydrodynamic equations and free surface boundary conditions. The free surface boundary conditions require an additional boundary term in the action which resembles a $1+1D$ chiral boson field coupled to the background geometry. We solve the linearized hydrodynamic equations for the deep water case and derive the dispersion of chiral surface waves. We show that in the long wavelength limit the flow profile exhibits an oscillating vortical boundary layer near the free surface. The thickness of the layer is controlled by the length scale given by the ratio of odd viscosity to the sound velocity $\delta \sim \nu_o/c_s$. In the incompressible limit, $c_s\to \infty$ the vortical boundary layer becomes singular with the vorticity within the layer diverging as $\omega \sim c_s$. The boundary layer is formed by odd viscosity coupling the divergence of velocity $\boldsymbol\nabla \cdot \boldsymbol{v}$ to vorticity $\boldsymbol\nabla \times \boldsymbol{v}$. It results in non-trivial chiral free surface dynamics even in the absence of external forces. The structure of the odd viscosity induced boundary layer is very different from the conventional free surface boundary layer associated with dissipative shear viscosity.

Anisotropy of Langmuir turbulence and the Langmuir-enhanced mixed layer entrainment

Surface waves in the ocean surface boundary layer can create Langmuir turbulence which has structure distinct from shear turbulence in a conventional boundary layer. We show that the distinctive structure of Langmuir turbulence is quickly lost away from the surface, so that near the boundary layer base it becomes indistinguishable from turbulence in the absence of surface waves. This has important implications for modeling the effect of ocean surface waves on the boundary layer entrainment and improving ocean surface boundary layer parameterizations in Earth system models.

Towards codification of thunderstorm/downburst using gust front factor: Model-based and data-driven perspectives

Winds associated with gust fronts originating from a thunderstorm/downburst exhibit rapid changes during a short time period which may be accompanied by changes in direction. For several decades, a number of studies have been focused on identifying the characteristics of such nonstationary gust front winds in a variety of manners such as experimental/numerical methods and full-scale measurements. Yet, beginning the dialogue on any guidelines for design practice has thus far not evolved, in part due to a limited consensus on such characteristics among studies in conjunction with paucity of available data needed for vetting and corroborating, which is further impacted by the presence of nonstationarity. In an effort to establishing a new design procedure for this type of wind load effect on structures, the gust front factor (GFF) framework has been proposed by authors that encapsulates both the kinematic and dynamic features of gust front induced wind effects on structures, which distinguish themselves from those experienced in conventional boundary layer flows. This study revisits the gust front factor framework seeking to take the next step toward a possible initial framework for codification of gust front winds from model-based and data-driven perspectives. A modular and extensible web-enabled framework to estimate gust front related wind load effects is envisaged to rationally and holistically quantify design loads. This would promote design practice to enhance disaster resilience of the built environment. In this context, a closed-form expression concerning nonstationary fluctuations for a case of a long pulse duration is derived to facilitate rapid evaluation of nonstationary turbulence effects. A preliminary uncertainty analysis is also carried out to assess the influence of uncertainties associated with the load effects of gust front winds and the reliability of GFF. In addition, a comparison of the model-based gust front factor with a recently introduced thunderstorm response spectrum technique to assess their relative performance is carried out. In view of the lessons learned from the history of the gust loading factor on codes and standards, a possible living codification concept through a learning and updating invoking the emerging “Design Thinking” approach is discussed.

ANALYSIS OF CONTACT LOADS CONCENTRATION IN PRESSURE COUPLINGS OF THIN-WALL COMPONENTS

A number of aviation assemblies are made as pressure couplings of thin-wall components, e.g., shafts and hubs, durability of which is related to fitting contact load concentrations under cyclic and dynamic loadings. This article discusses a numeric solution to the contact problem. The solution is introducing into the calculations a conventional boundary layer, any shift of which is equivalent to a roughness deformation of fitting surfaces. The mathematical model of a pressure coupling is founded on a division of deformations into general (axisymmetric bending of components) and local deformations (microroughness compression) that are determined independently. To simplify the solution, the dependence of the contact convergence of the surfaces on the pressure is subjected to linearization in the form of a model of a rigid plastic body with linear strengthening. Convergence values in section are only determined by the pressure and do not depend on the stress-and-strain behaviors of areas adjacent to the rough interfacial space. The Green’s functions method is used to find radial shifts of components, while the solution is expressed by the Fredholm integral equation. That is reduced to a finite system of linear algebraic equations when the contact is made discrete. This approach provides solution stability through strengthening of the main diagonal of the resolving system, while the evaluation accuracy of the concentration coefficient depends on the subinterval value. It has been found that any disclosure of a coupling beneath the faces of an enveloping body is practically impossible for that model. The comprehensive approach provides a generalized solution for orthotropic and stepwise shells, as well as for components with specific design features and various strengths of areas adjacent to fitting sites. Deviations of the shape of the contact surfaces from the straightness are taken into account by its respective pressure coupling function. The analysis of the findings suggests that the concentration coefficient value slumps as the contact compliance coefficient of the borderline layer increases. Any shape deviations of the fitting surfaces, including their coning and concavity, increase the contact load concentration, while their convexity causes a reverse effect. We recommend using strengthening treatment methods, e.g., application of regular micropattern in the shape of helical flute at a certain pitch while applying a constant or a variable force on the diamond indenter, or vibration smoothing in order to control the shaft surface finishing to improve the stressand-strain behavior of the seam and to impart an artificial barrel shape of a preset value to the shaft. These technologies compensate contact load concentrations, and, together with the strengthening factor, enhance the fatigue limit of such assemblies.

Stefan flow induced natural convection suppression on high-flux evaporators

High-flux evaporators are important for various fundamental research and industrial applications. Understanding the heat loss mechanisms, especially the contribution of natural convection during evaporation is thus a ubiquitous process to predict and optimize the performance of evaporators. However, a comprehensive analysis on natural convection heat transfer, where the vertical Stefan flow due to evaporation couples with buoyancy driven convective flow has not been carefully considered. In this work, we developed a theoretical framework to elucidate the effect of Stefan flow on natural convection during evaporation. This theory incorporates the vertical Stefan flow into the conventional boundary layer theory. We found that a significant suppression of natural convection can be induced by a weak Stefan flow owing to the increase of boundary layer thickness. To understand this phenomenon, we discuss the governing mechanisms at different Stefan flow regimes. We provide a theoretical correlation to the overall heat transfer which includes both effects of the Stefan flow velocity and the buoyancy force. We finally predict the effect of natural convection on an evaporator at different operating temperatures. The heat loss from natural convection no longer monotonically increases with the superheat temperature due to the effect of Stefan flow suppression. As a result, there is an approximately 40% overestimation of the natural convection contribution at saturation temperature using conventional theory. This work improves the fundamental understanding of the natural convection during evaporation and can help guide future high-performance evaporator designs.

Downburst related damages in Brazilian buildings: Are they avoidable?

Brazil's territory has shown an enormous potential to generate severe weather and intensive downbursts cases gained attention as a result of the severe destructive patterns not frequently seen before. However, several of the downburst damages on Brazilian buildings and structures follow a similar pattern than those caused by synoptic winds. The significant amount of accidents due to extreme winds in the recent years suggests the need for a review of the Brazilian Wind Code as well as the necessity to reinforce its use in common day buildings design. The new version of the code should incorporate an update of climate data and implement a thunderstorm wind model. This paper brings an overview of the downburst areas with major risk of occurrences, as well as presents an analysis of the damage patterns caused by the downbursts, with special focus on the effects on buildings and structures. It is concluded that, although the flow characteristics of downburst winds and conventional boundary layer simulations of synoptic winds may differ, the use of current conventional wind tunnel simulations and conventional code values are still a valuable tool in the prevention of wind related damages, at least in low and medium-rise buildings.

A terrain-following model of wave boundary layers

Over a variable seabed, conventional boundary layer approximations are rendered to be inadequate because of the large variations in bed elevation in the direction of wave propagation. Applying the method of conformal transformation to map the flow domain with a corrugated boundary onto a uniform strip, we put forward a terrain-following modeling approach for Stokes boundary layer flows, accompanying the recent development of the exact Floquet theory of water waves over a generally periodic seabed. For a non-steep seabed profile, but not necessarily small undulation height compared with the water depth, we solve the vorticity equation to obtain the analytical solutions for the boundary layer velocities, bed shear stress and rate of viscous dissipation, explicitly showing the variations both across the boundary layer and along the bed. For a relatively steep bed profile, a remedy is proposed that allows the velocity profiles to be locally determined across the boundary layer avoiding solving the 2-D differential equation for the vorticity. The modeling methodology is presented here for a constant viscosity, including the case of constant eddy viscosity, but can be extended to the case of variable eddy viscosity to improve turbulence modeling.

Partial turbulence simulation method for predicting peak wind loads on small structures and building appurtenances

Large-scale wind tunnel testing is preferred for small structures and building appurtenances for maintaining modeling accuracy and minimizing Reynolds number effects. In these circumstances the ability to obtain a large enough turbulence integral scale is usually compromised by the limited dimensions of the wind tunnel. So, it is not normally possible to fully simulate the low frequency end of the turbulence spectrum. In this paper the approach is taken of dividing the turbulence into two distinct statistical processes, one at high frequencies which can be simulated in the wind tunnel, and one at low frequencies which can be treated in post-test analysis using the assumptions of quasi-steady theory. In this Partial Turbulence Simulation (PTS) method the contribution of both the high and low frequency turbulence on the wind loads on structures is included by using the probability of load from each of the two processes, with one part coming from the wind tunnel data representing the high frequency component and the remainder from the assumed probability distribution (taken in this paper as Gaussian for generic boundary layer flow) of the missing low frequency component. The two processes are approximated as independent of each other. The efficacy and validity of the method and its various assumptions are assessed by comparing predicted local peak pressure coefficients from tests on large scale models of the Silsoe cube and Texas Tech University (TTU) building in the Wall of Wind facility at Florida International University (FIU) with the corresponding full-scale data. Generally good agreement was found between the model results and full scale, particularly when comparing the highest overall peak pressure coefficients. These results, although limited to peak local pressures on the two test buildings for which good full scale data are available, are encouraging and invite further experiments to explore the range of applicability of the PTS method. This method, although developed in the Wall of Wind facility at FIU, can be equally used in conventional boundary layer wind tunnels and has the potential to enhance the ability of existing boundary layer wind tunnel facilities to predict full scale wind loads.

An experimental investigation on the characteristics of fluid–structure interactions of a wind turbine model sited in microburst-like winds

An experimental investigation is performed to assess the characteristics of the fluid–structure interactions and microburst-induced wind loads acting on a wind turbine model sited in microburst-liked winds. The experiment study was conducted with a scaled wind turbine model placed in microburst-like winds generated by using an impinging-jet-typed microburst simulator. In addition to quantifying complex flow features of microburst-like winds, the resultant wind loads acting on the turbine model were measured by using a high-sensitive force–moment sensor as the turbine model was mounted at different radial locations and with different orientation angles with respect to the oncoming microburst-like winds. The measurement results reveal clearly that, the microburst-induced wind loads acting on the turbine model were distinctly different from those in a conventional atmospheric boundary layer (ABL) wind. With the scales of the wind turbine model and the microburst-like wind used in the present study, the dynamic wind loadings acting on the turbine model were found to be significantly higher (i.e., up to 4 times higher for the mean loads, and up to 10 times higher for the fluctuation amplitudes) than those with the same turbine model sited in ABL winds. Both the mean values and fluctuation amplitudes of the microburst-induced wind loads were found to vary significantly with the changes of the mounted site of the turbine model, the operating status (i.e., with the turbine blades stationary or freely rotating), and the orientation angle of the turbine model with respect to the oncoming microburst-like wind. The dynamic wind load measurements were correlated to the flow characteristics of the microburst-like winds to elucidate underlying physics. The findings of the present study are helpful to gain further insight into the potential damage caused by the violent microbursts to wind turbines to ensure safer and more efficient operation of the wind turbines in thunderstorm-prone areas.

An experimental study on wind loads acting on a high-rise building model induced by microburst-like winds

In the present study, an experimental investigation is conducted to quantify the characteristics of the microburst-induced wind loads (i.e., both static and dynamic wind loads) acting on a high-rise building model, compared to those with the test model placed in conventional atmospheric boundary layer (ABL) winds. The experimental study is performed by using an impinging-jet-based microburst simulator available at Iowa State University. In additional to conducting flow field measurements to quantify the flow characteristics of the microburst-like wind, both mean and dynamic wind loads acting on the test model induced by the microburst-like wind are assessed in detail based on the quantitative measurements of the surface pressure distributions around the test model and the resultant aerodynamic forces. It is found that the microburst-induced wind loads acting on high-rise buildings would be significantly different from their counterparts in conventional ABL winds. Both the static and dynamic wind loads acting on the high-rise building model were found to change significantly depending on the radial locations and the orientation angles of the test model in respect to the oncoming microburst-like wind. The dynamic wind loads acting on the test model were found to be mainly influenced by the periodical shedding of the primary vortices and the high turbulence levels in the microburst-like wind. The findings derived from the present study are believed to be useful to gain further insight into the underlying physics of the flow–structure interactions of high-rise buildings in violent microburst winds for a better understanding of the damage potential of microburst winds to high-rise buildings.

Seamless Stratocumulus Simulation across the Turbulent Gray Zone

Abstract A pragmatic approach for representing partially resolved turbulence in numerical weather prediction models is introduced and tested. The method blends a conventional boundary layer parameterization, suitable for large grid lengths, with a subgrid turbulence scheme suitable for large-eddy simulation. The key parameter for blending the schemes is the ratio of grid length to boundary layer depth. The new parameterization is combined with a scale-aware microphysical parameterization and tested on a case study forecast of stratocumulus evolution. Simulations at a range of model grid lengths between 1 km and 100 m are compared to aircraft observations. The improved microphysical representation removes the correlation between precipitation rate and model grid length, while the new turbulence parameterization improves the transition from unresolved to resolved turbulence as grid length is reduced.

Turbulent plane wall jets over smooth and rough surfaces

Large-eddy simulations were carried out to study the effects of surface roughness on a plane wall-jet using the Lagrangian dynamic eddy-viscosity subgrid-scale model, at Re = 7500 (based on the jet bulk velocity and height). Results over both smooth and rough surfaces were validated by experimental data at the same Reynolds number. As the jet is injected into the still environment, large-scale rollers are generated in the shear layer between the high-momentum fluid of the jet and the surrounding and are convected downstream with the flow. To understand the extent to which the outer-layer structures modify the flow in the inner layer and the extent to which the effect of roughness spreads away from the wall, both instantaneous and mean flow fields were investigated. The results revealed that, for the Reynolds number and roughness height considered in this study, the effect of roughness is mostly confined to the near-wall region of the wall jet. There is no structural difference between the outer layer of the wall jet over the smooth and rough surfaces. Roughness does not affect the size of the outer-layer structures or the scaling of the profiles of Reynolds stresses in the outer layer. However, in the inner layer, roughness redistributes stresses from streamwise to wall-normal and spanwise directions toward isotropy. Contours of joint probability-density function of the streamwise and wall-normal velocity fluctuations at the bottom of the logarithmic region match those of the turbulent boundary layer at the same height; while the traces of the outer-layer structure were detected at the top of the logarithmic region, indicating that they do not affect the flow very close to the wall, but still modify a major portion of the inner layer. This modification must be taken into consideration when the inner layer of a wall jet is compared with the conventional turbulent boundary layer.

Finless Heat Sinks, High Performance and Low Cost for Low Profile Cooling Applications

The need for low profile, sustainable thermal management solutions is becoming critical in information and communications technology applications ranging from consumer products to server cabinets. This work presents a finless thermal management solution that utilizes fluidic structures generated within an empty cavity to enhance the heat transfer coefficient. The finless thermal management solution can be manufactured to have a height of less than 5 mm when using low profile motors. Particle image velocimetry (PIV) combined with infrared (IR) imaging techniques are used to explain the underlying flow physics that results in increased heat transfer rates compared to typical laminar flows. It is found that the local heat transfer coefficients in the finless design are up to 500% greater than those achieved at the same Reynolds number using conventional boundary layer theory. The design is compared to an existing commercial solution and is found to provide benefits in terms of cost, reliability, weight, acoustics, and fan power consumption. These advancements over current state of the art lead to a more sustainable solution for low cost, low profile cooling applications.

An experimental study of flow fields and wind loads on gable-roof building models in microburst-like wind

An experimental study was conducted to quantify the flow characteristics of microburst-like wind and to assess the resultant wind loads acting on low-rise, gable-roof buildings induced by violent microburst-like winds compared with those in conventional atmospheric boundary layer winds. The experimental work was conducted by using an impinging-jet-based microburst simulator in the Department of Aerospace Engineering, Iowa State University. Two gable-roof building models with the same base plan and mean roof height, but different roof angle, were mounted over a homogenous flat surface for a comparative study. In addition to measuring the surface pressure distributions to determine the resultant wind loads acting on the building models, a digital particle image velocimetry system was used to conduct flow field measurements to reveal the wake vortex and turbulence flow structures around the building models placed in the microburst-like wind. The effects of important parameters, such as the distance of the building from the center of the microburst, the roof angle of the building, and the orientation of the building with respect to radial outflow of the oncoming microburst-like wind, on the flow features such as the vortex structures and the surface pressure distributions around the building models as well as the resultant wind loads acting on the test models were assessed quantitatively. The measurement results reveal clearly that when the building models were mounted within the core region of the microburst-like wind, the surface pressure distributions on the building models were significantly higher than those predicted by ASCE 7-05 standard, thereby induced considerably greater downward aerodynamic forces acting on the building models. When the building models were mounted in the outflow region of the microburst-like wind, the measured pressure distributions around the building models were found to reach a good correlation with ASCE 7-05 standard gradually as the test models were moved far away from the center of the microburst-like wind. It was also found that both the radial and vertical components of the aerodynamic forces acting on the building models would reach their maximum values when the models were mounted approximately one jet diameter away from the center of the microburst-like wind, while the maximum pressure fluctuations on the test models were found to occur at further downstream locations. Roof angles of the building models were found to play an important role in determining the flow features around the building models and resultant wind loads acting on the test models. The flow field measurements were found to correlate with the measured surface pressure distributions and the resultant wind loads (i.e., aerodynamic forces) acting on the building models well to elucidate the underlying physics of flow-structure interactions between the microburst-like winds and the gable-roof buildings in order to provide more accurate prediction of the damage potentials of the microburst wind.