Is blood flow laminar or turbulent?

We’ve all been taught that blood flows smoothly through our arteries, gliding like a steady river on a calm day. For decades, the prevailing assumption was that normal, healthy blood flow is laminar—neatly layered, free from disruption. But what if that’s not the whole story? A growing body of research, based on the study by Khalid M. Saqr and his colleagues from Tohoku University, Japan, suggests something very different: blood flow is far more chaotic than previously thought.

In their 2020 study, published in Scientific Reports, Saqr et al. tackle a long-held belief in vascular biology—that turbulent blood flow is a sign of pathology, an indicator of trouble, often linked to conditions like atherosclerosis or aneurysms. But the reality appears to be more nuanced, and perhaps, more chaotic.

Blood Flow Is Naturally Turbulent

Saqr and his team take us on a journey deep into the physics of blood flow. Using cutting-edge techniques, they show that even under normal, healthy conditions, blood doesn’t always behave like a calm river. Instead, it exhibits turbulence—not the wild, swirling turbulence of a storm at sea, but a unique, more structured form of disorder. This turbulence, they found, is not the usual type we associate with turbulent flows in nature. It’s something called non-Kolmogorov turbulence, and it defies many of the classical models of fluid dynamics.

This finding challenges a fundamental assumption in cardiovascular science: that laminar flow is the default in healthy arteries. If Saqr and his team are correct, turbulence is not a harbinger of disease, but rather a natural feature of blood flow. This new perspective forces us to rethink how we understand cardiovascular and neurovascular diseases.

The Science Behind the Discovery

The team’s research draws on decades of advancements in fluid dynamics. They began by using the Womersley Flow Model (WFM), a mathematical model of blood flow that’s been a cornerstone of vascular research for over half a century. The WFM, however, typically assumes blood flow is laminar under normal conditions. Saqr’s team wanted to test whether this assumption still holds up.

By studying flow patterns in the carotid arteries of healthy volunteers, using both in vitro and in silico methods, they identified three key characteristics of turbulent blood flow: sensitivity to initial conditions, global instability, and a cascade of kinetic energy. They observed how energy transfers from larger to smaller vortex structures in the bloodstream, a hallmark of turbulence, but one that behaves differently in the human body than in typical fluid flows, like air or water.

These findings suggest that the body’s arterial system might be predisposed to turbulence from the start, and that this turbulence might play a role in how blood interacts with the walls of arteries, especially in areas where diseases tend to form, such as near bifurcations or bends in major vessels.

Implications for Cardiovascular and Neurovascular Health

So, why does this matter? It could dramatically alter how we think about diseases like atherosclerosis or brain aneurysms. Historically, these conditions have been linked to turbulent blood flow, with the assumption that turbulence causes damage to the vessel walls, leading to inflammation, plaque buildup, or even rupture.

But what if the turbulence itself isn’t the problem? What if it’s the nature of the turbulence—its chaotic energy cascade—that changes in diseased vessels? This would shift the focus of therapies from trying to eliminate turbulence to managing how energy is distributed in the blood flow.

For instance, in the case of brain aneurysms, where weak spots in blood vessels balloon out under pressure, this new understanding could lead to therapies that aim to stabilize the flow, rather than simply reducing blood pressure. Similarly, treatments for atherosclerosis could focus on the turbulent characteristics of blood flow in arterial bends and bifurcations, rather than just treating the symptoms after plaque has already built up.

A New Frontier in Therapeutics

What makes this research particularly exciting is its potential for innovation in cardiovascular therapeutics. Imagine a drug delivery system designed to exploit the natural turbulence of blood flow, using it to carry medications directly to areas of the artery where they’re most needed. Or consider intravascular devices designed to gently stabilize turbulent flow in problem areas, preventing plaque buildup before it begins.

This new way of thinking also raises questions about how we approach blood flow in medical devices, like stents or artificial heart valves. If turbulence is a natural part of healthy blood flow, we may need to reconsider how we design these devices to work with the body’s chaotic systems, rather than against them.

The Big Picture

At its core, this research challenges us to rethink long-held assumptions about how our bodies work. The idea that blood flow is naturally turbulent—even in health—invites us to reconsider what we know about the cardiovascular system. It opens new doors to understanding disease and promises innovative therapeutic approaches that could transform how we prevent and treat some of the most common vascular conditions.

As we move forward, it’s crucial to remember that in biology, as in life, chaos doesn’t always mean disorder—it might just be part of the design. And in the case of blood flow, embracing this chaos could be the key to unlocking new, life-saving treatments.