Fluid moving through microchip

Unlocking Fluid Dynamics: How Minor Losses Impact Your Everyday Tech

Mira Elwood in Science & Nature September 2025 • 4 min read.

"From blood flow to solar panels, understanding pulsatile laminar flow could revolutionize engineering and medicine."

In recent years, there's been an explosion of interest in how fluids move in tiny channels with non-circular shapes. This isn't just a niche academic problem; it turns out to be super important for tons of real-world applications. Think about solar panels efficiently transferring heat, advanced heat exchangers keeping electronics cool, and even fuel cells powering the future. The way fluids pulse and flow in these systems makes a huge difference in their performance.

But it doesn't stop there. Unsteady fluid dynamics are also critical in areas you might not immediately connect to engineering. For example, understanding how blood flows through our veins and arteries, or how air moves in our lungs, relies on the same principles. These biological systems face similar challenges in managing pulsatile flow within complex geometries.

The problem? We don't have a complete picture of what happens to fluids as they navigate these tiny, intricate pathways. While there's information out there about losses in turbulent flow, the data is sparse when it comes to laminar flow. This article explores how researchers are working to nail down these 'minor losses'—the energy dissipated as fluids move through bends and constrictions—so engineers can design better, more efficient systems.

Decoding Minor Losses: A New Method for Pulsatile Laminar Flow

Researchers at CTU in Prague have developed a method to evaluate the size of minor losses in pulsatile laminar flow. This method focuses on the phase delay between pressure and flow waveforms to determine these losses. The team used a 90-degree bend in a channel with a square cross-section as an example to test and illustrate their method with an incompressible Newtonian fluid.

The team divided the flow into steady and oscillating components to study the sinusoidal pulsatile flow. They considered that the loss is constituted by the sum of the local loss of steady flow and a friction loss of steady flow, local loss of oscillating flow, friction loss and influence of inertia forces of the oscillating flow. This approach allowed them to look at both constant and changing aspects of the flow separately, making the analysis more precise.

Steady Flow Impedance: The steady component of the flow is expressed by impedance (Zst), which is further divided into impedance caused by friction losses (Zst) and local losses (Z'st).
Oscillating Flow Impedance: The oscillating component is described using a complex impedance (Zosc), accounting for inertia forces and friction losses.
Local Loss Impedance: Calculated as the difference between the total impedance of the channel with the bend and the analytical impedance of a straight section.

To validate their approach, the team used numerical simulations with ANSYS Fluent v13. They created a detailed geometric model of the channel and ran simulations to compare their calculated impedance values with the simulation results. The team then compared the calculated pressure loss with pressure recorded during numerical simulation, with the largest error being 4.8%.

The Future of Fluid Dynamics: Better Designs, Better Tech

By quantifying these minor losses, engineers can create more accurate models and simulations, leading to optimized designs. This could mean more efficient solar panels, better performing medical devices, and even advancements in aerospace engineering. As our technology becomes increasingly reliant on microfluidic systems, understanding these fundamental principles will be key to innovation.

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Everything You Need To Know

What is pulsatile laminar flow and why is it important in various applications?

Pulsatile laminar flow refers to the rhythmic, non-turbulent movement of fluids within channels. This type of flow is crucial in numerous applications, including the design of efficient solar panels, advanced heat exchangers for electronics, and fuel cells. Furthermore, understanding pulsatile laminar flow is critical in biomedical applications, such as analyzing blood flow through veins and arteries and studying air movement within the lungs. The efficient management of this flow in complex geometries is a key factor in the performance and functionality of these systems.

What are 'minor losses' in pulsatile laminar flow, and why are they difficult to quantify?

Minor losses in pulsatile laminar flow are the energy dissipations that occur as fluids navigate bends and constrictions within channels. These losses are challenging to quantify because the data available is sparse, especially when compared to the information on turbulent flow. Researchers face the complexity of unsteady fluid dynamics in non-circular channels, making it difficult to create accurate models and simulations. Overcoming this challenge is essential for designing more efficient systems in various engineering and biomedical fields.

How did researchers at CTU in Prague evaluate minor losses in pulsatile laminar flow?

Researchers at CTU in Prague developed a method focusing on the phase delay between pressure and flow waveforms to determine minor losses in pulsatile laminar flow. They used a 90-degree bend in a channel with a square cross-section to test and illustrate their method. The team divided the flow into steady and oscillating components, considering the loss as a sum of steady flow impedance (Zst), oscillating flow impedance (Zosc), and local loss impedance. They validated their approach through numerical simulations using ANSYS Fluent v13, comparing calculated impedance values with simulation results.

What is the significance of Steady Flow Impedance (Zst) and Oscillating Flow Impedance (Zosc) in this context?

Steady Flow Impedance (Zst) represents the steady component of the flow and is further divided into impedance caused by friction losses (Z'st) and local losses. Oscillating Flow Impedance (Zosc) describes the oscillating component of the flow, accounting for inertia forces and friction losses. These impedance calculations are crucial because they allow researchers to analyze the flow's constant and changing aspects separately. This method enhances the precision of understanding how energy is lost within the system and facilitates accurate modeling and simulation of fluid dynamics.

What are the potential benefits of understanding and quantifying minor losses in pulsatile laminar flow for the future?

By quantifying minor losses, engineers can create more accurate models and simulations, leading to optimized designs. This can result in more efficient solar panels, better-performing medical devices, and advancements in aerospace engineering. As technology increasingly relies on microfluidic systems, understanding these fundamental principles will be key to innovation. This knowledge will contribute to significant improvements in various fields by enabling the development of more efficient, reliable, and innovative technologies, which in turn drives progress in engineering and medicine.