The research, led by Pedro Fernández-Cabán, assistant professor of civil engineering at the FAMU-FSU College of Engineering, together with associate professor Qian Zhang, doctoral student Arezoo Bakhshizadeh and alumnus Peter Tsouroukdissian, set out to answer a question that has long intrigued wind engineers: can macro-scale corrugation of a building envelope meaningfully disrupt the aerodynamic mechanisms that tear roofs off houses and peel cladding from walls? The answer, according to their wind tunnel experiments, is a resounding yes. Models with the deepest wave patterns tested reduced peak wind pressures by 40 to 60 percent near roof and wall corners—the very zones where destructive forces concentrate—across multiple wind directions.

“Changing a building’s shape can significantly reduce the intensity of wind forces it has to withstand,” said Fernández-Cabán. “These nonconventional building shapes reduce the damage from worst-case severe weather scenarios. It’s another tool for engineers and designers to protect against wind damage.” That statement captures a shift in thinking that has been gathering momentum in structural engineering for years. Rather than simply building thicker walls or specifying stronger materials to resist wind loads, engineers can instead reshape the building so that the loads never fully develop in the first place.

To test the concept, the team fabricated 3D-printed scale models of low-rise buildings equipped with wave-shaped exterior roof and wall systems in place of traditional flat surfaces. Three-dimensional printing allowed the researchers to produce precise, repeatable geometries that would have been difficult or impossible to construct by hand. They then systematically varied the depth of the waves, evaluating amplitudes between 5 and 10 percent of the building height, and compared each configuration against a conventional flat-walled control model. Pressure taps embedded in the model surfaces recorded the fluctuating wind pressures at high resolution as the models were subjected to controlled airflow in the college’s wind tunnel.

The physics behind the improvement lies in the behavior of vortices—rotating masses of air that form when wind flows over sharp edges and corners. When wind sweeps smoothly across a flat wall or a pitched roof, the flow separates abruptly at the leading edge, curling back on itself and creating powerful conical vortices that cling to roof corners and wall edges. These vortices generate regions of intense suction, where the local air pressure drops far below the ambient atmospheric pressure. The higher pressure inside the building then pushes outward on the roof or wall surface toward that low-pressure zone, and it is this differential—often acting suddenly and in gusts—that lifts roofing membranes, rips off shingles and tears siding loose. The strongest forces reliably develop at the corners and edges of the roof, where the vortices congregate and pose the greatest threat to structural integrity.

Wave-shaped surfaces attack this mechanism at its root. Instead of presenting a sharp, straight edge where flow can separate cleanly and organize into a coherent vortex, the undulating envelope presents a series of rounded hills and valleys that continuously disrupt the airflow. The wind skips across these contours like a stone bouncing across the surface of a lake, unable to settle into the steady separation patterns that produce concentrated suction loads. Each successive crest and trough breaks up the pressure zones and redirects the flow away from the building envelope, preventing the pockets of high suction from forming in the first place. In effect, the geometry converts one large, coherent, destructive aerodynamic structure into many small, weak, rapidly mixing ones.

The wind tunnel data confirmed this picture quantitatively. Among the configurations tested, the model with the greatest wave depth proved the most effective at alleviating wind load effects, delivering peak pressure reductions of 40 to 60 percent near roof and wall corners across multiple wind directions. That range matters enormously in practice, because hurricanes do not arrive from a single predictable heading, and a mitigation strategy that only works when the wind blows from one quarter would be of limited value. The consistency of the benefit across directions suggests that corrugated envelopes could provide robust, all-around protection rather than a narrow, orientation-dependent advantage.

The economic logic of the approach is equally compelling. Battling wind pressure has long been an ongoing challenge in structural design, and the conventional toolkit reflects that struggle. Exterior architectural features such as rounded corners, sloped walls and stepped setbacks are known to alleviate wind loads, and another common strategy is to make walls thicker or sturdier by adding more or tougher material. These techniques can be effective, but they are expensive. Design and site constraints rule out some features entirely, and retrofitting them onto existing structures can be impractical or prohibitively costly. A corrugated facade, by contrast, modifies the geometry of the envelope itself, potentially adding aerodynamic resilience without demanding dramatic increases in material quantity or fundamentally altering the building’s footprint. The research demonstrates the possibility of adopting building facades with nontraditional shapes as a practical route to wind protection.

The implications of the work extend well beyond the structural engineering community. The underlying fluid dynamics—the behavior of turbulent boundary layers, flow separation and vortex shedding over curved and corrugated surfaces—carry broad relevance for any field that investigates how fluids move around obstacles. “We’re dealing with air, and other engineers and scientists might be dealing with waves and water, but the understanding of fluid dynamics can inform design and engineering across fields,” Fernández-Cabán said. “Aerodynamic optimization requires a multidisciplinary approach that balances structural safety, resilience, material efficiency and performance.” Researchers in aeronautics, environmental science and fundamental physics all grapple with versions of the same problem: how geometry shapes the turbulent flows that determine forces, heat transfer and mixing. Insights from building aerodynamics could inform everything from the design of more efficient aircraft components to models of how wind transports particles and pollutants over rough terrain.

Much work remains before wave-shaped envelopes appear on real construction sites. The current study measured the wind pressures acting on the surfaces of the models, which is the critical first step, but the research team is already conducting additional experiments to better understand the detailed wind flows around these envelope systems—how the air actually moves, separates and reattaches as it travels over the corrugations. The researchers also plan to deploy computational fluid dynamics modeling to further optimize the wave patterns and to explore other surface geometries that were not physically tested in the wind tunnel. Together, these efforts could yield design guidelines that architects and engineers can apply directly, turning an elegant laboratory result into a standard strategy for hurricane resilience. For communities on the front lines of increasingly severe storms, the message from Tallahassee is striking: sometimes the best defense against the wind is not more material, but a better shape.

Subject of Research: Aerodynamic mitigation of hurricane wind loads on low-rise buildings using wave-shaped corrugated wall and roof surfaces

Article Title: FAMU-FSU College of Engineering researchers develop wave-shaped wall and roof designs that protect against hurricane-force winds

Article References: FAMU-FSU College of Engineering researchers develop wave-shaped wall and roof designs that protect against hurricane-force winds. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: wind engineering, hurricane resilience, building aerodynamics, wind tunnel testing, vortex dynamics, low-rise buildings, corrugated envelopes, structural engineering, fluid dynamics, wind loads, 3D-printed models, Engineering Structures

The team, led by Kagan Ucak, Coskun Bilgi, and Niema M. Pahlevan, focused on diastole, the relaxation phase of the cardiac cycle when the left ventricle fills with blood returning from the lungs. Filling happens in two waves: an early passive rush of blood called the E-wave, driven by the ventricle’s own relaxation, and a later surge called the A-wave, produced when the atrium contracts. Between the two lies diastasis, a quiet interval in which little blood moves at all. Cardiologists have long used the ratio of the peak velocities of these two waves, the E/A ratio, to classify diastolic function into normal filling, impaired relaxation, and restrictive filling, the latter marking the most severe stage of dysfunction. What has remained murky is precisely how these different inflow patterns reshape the fluid dynamics inside the chamber and what that reshaping costs the heart in mechanical efficiency.

To find out, the researchers constructed a physiologically accurate left ventricle simulator: a compliant, transparent silicone sac submerged in a pressurized acrylic tank and driven by a programmable piston pump. The sac was fitted with artificial mitral and aortic valves and connected to a hydraulic circuit with adjustable resistance and compliance, allowing the team to tune afterload and preload independently. A blood-analog fluid, mixed from water, glycerol, and urea to match the viscosity and density of real blood, was seeded with tiny fluorescent microspheres. By illuminating a thin laser sheet through the ventricle’s mid-plane and capturing images with a 12.6-megapixel high-speed camera, the researchers performed phase-locked particle image velocimetry, or PIV, resolving velocity fields with a spatial resolution of roughly 0.4 millimeters across 29 repeated cardiac cycles for each experimental condition.

The elegance of the setup lies in its control. In patients, it is nearly impossible to isolate the effect of a single parameter, because heart rate, stroke volume, filling pressure, and ventricular geometry all change together as disease progresses. In the simulator, the team could dial in an E/A ratio below 0.8 to mimic impaired relaxation, above 2.0 to mimic restrictive filling, or an intermediate value for normal filling, while independently varying the duration of diastasis from zero to twenty percent of the cardiac cycle, the heart rate from 60 to 90 beats per minute, and the cardiac output from 2.0 to 3.3 liters per minute. Crucially, the resulting inflow velocities of 0.5 to 0.9 meters per second fell squarely within the range measured clinically by Doppler echocardiography, and the calculated vortex formation times matched values previously reported in patients.

What the camera revealed was striking. Under normal filling, the E-wave generates a pair of counter-rotating vortices that sweep toward the ventricular apex, settle near the walls, and gently fade as the A-wave delivers its own vortex pair into the center of the chamber. The two vortex systems coexist in an orderly, energy-efficient sequence. Under restrictive filling, by contrast, the E-wave arrives with far greater force, producing larger, more intense vortices that dominate the chamber, while the weakened A-wave enters without forming any coherent vortex structure at all. The result is a burst of intense dissipation early in diastole followed by an almost stagnant ventricle, with the velocity field nearly motionless by the time systole begins.

The quantitative consequences were dramatic. Restrictive filling patterns produced a peak viscous energy dissipation fifty percent higher than normal filling, along with a 38 percent increase in peak turbulent kinetic energy and a 21 percent higher peak shear rate. Impaired relaxation patterns told a different story: because the weak E-wave vortices linger in the chamber, the arriving A-wave vortices catch up and merge with them, creating a single, larger, tilted vortex structure that persists into early systole. This merging event drove the highest peak turbulent kinetic energy of all, 57 percent above normal, and pushed peak energy dissipation 46 percent above the healthy baseline. Elevated shear rates and turbulent kinetic energy are clinically meaningful because both have been linked to damage of blood cells and platelets, suggesting that severely diseased filling patterns may impose additional hemodynamic stress on the blood itself.

Perhaps the most surprising discovery concerned diastasis, the quiet pause between the filling waves, which had never been systematically studied before. The researchers found that a moderate diastasis duration, around ten percent of the cardiac cycle, minimized viscous energy dissipation across all E/A ratios, revealing a local energetic optimum that corresponds precisely to the normal filling pattern with an E/A ratio near 1.5. Too little diastasis forces the filling waves to collide and interact chaotically; too much allows the E-wave vortices to dissipate completely before the A-wave arrives, forfeiting any beneficial interaction. Intriguingly, this optimum vanished under low-cardiac-output conditions, hinting that the energetic landscape of the ventricle shifts with the heart’s overall workload.

The team also uncovered distinct scaling laws for the impaired relaxation pattern. When stroke volume was varied from 27 to 53 milliliters at a fixed heart rate, diastole-averaged energy dissipation rose nonlinearly, following a second-order polynomial trend. When heart rate was varied from 60 to 90 beats per minute at constant cardiac output, dissipation per cycle stayed essentially constant, meaning total wasted energy scaled linearly with heart rate. The authors note an intriguing parallel with exercise physiology: stroke volume and heart rate both rise linearly with exercise intensity up to a threshold, beyond which stroke volume plateaus and falls while heart rate keeps climbing. The nonlinear energy penalty associated with increasing stroke volume may help explain why the heart sheds stroke volume at high exertion, particularly in patients whose ventricles are already filling inefficiently.

More than 6.7 million adults in the United States live with heart failure, and elevated left ventricular filling pressure is a central driver of the disease. Current diagnosis of diastolic dysfunction relies on Doppler indices such as the E/A ratio, mitral annular velocities, and estimates of filling pressure, but these provide only indirect glimpses of what the blood is actually doing inside the chamber. The USC team’s results suggest that flow-based energetic metrics, such as viscous energy dissipation, turbulent kinetic energy, and the presence of vortex merging, could serve as complementary markers of disease severity, potentially measurable at the bedside with echocardiographic particle image velocimetry, a technique already being explored in clinical settings.

The researchers are careful to note the limitations of their model. The simulator cannot replicate the full complexity of living myocardium, including fiber architecture, ventricular twist, and aortic root recoil, and its two-dimensional imaging cannot capture out-of-plane velocities in an inherently three-dimensional flow. The reported turbulent kinetic energy values, computed from 29 phase-locked cycles, should be read as comparative measures of flow fluctuation rather than direct measurements of fully developed turbulence. Still, as a controlled mechanistic study, the work delivers something clinical imaging cannot: a clean, parameter-by-parameter demonstration that the balance between early and late filling is not merely a diagnostic curiosity but a genuine determinant of the heart’s hydraulic efficiency. If future clinical studies confirm that these vortex signatures track with disease progression, the humble whirlpool inside the beating heart could become a powerful new window into heart failure, one that physicians could watch swirl, merge, and dissipate in real time.

Subject of Research: In vitro analysis of left ventricular vortex dynamics and energy dissipation across diastolic function filling patterns

Article Title: Vortex Dynamics and Energy Dissipation in Left Ventricular Diastolic Filling Across Diastolic Function Inflow Patterns: An In Vitro Quantitative Flow Analysis

Article References: Ucak, K., Bilgi, C., & Pahlevan, N. M. (2026). Vortex Dynamics and Energy Dissipation in Left Ventricular Diastolic Filling Across Diastolic Function Inflow Patterns: An In Vitro Quantitative Flow Analysis. Annals of Biomedical Engineering. https://doi.org/10.1007/s10439-026-04369-2

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04369-2

Keywords: diastolic dysfunction, left ventricle, vortex dynamics, particle image velocimetry, energy dissipation, turbulent kinetic energy, heart failure, E/A ratio, diastasis, hemodynamics, in vitro model, cardiac fluid mechanics