Wind turbines spinning in opposite directions create a “traffic jam” in the air that engineers are only now learning to untangle
In a wind tunnel in Oldenburg, two model turbines stand just centimeters apart — one spinning clockwise, the other counterclockwise. Their invisible wakes collide somewhere in the space between them, and what happens next depends almost entirely on a single choice: which rotor sits on which side.
The wind industry has spent decades chasing scale, pushing rotor diameters past 200 meters and turbine ratings toward 15 megawatts and beyond. A quieter shift is now underway — pairing two rotors on a single tower and learning to control how their wakes interact. New experiments suggest that the direction each rotor spins shapes that interaction far more than researchers had anticipated.
The rise of dual-rotor turbines
The industry’s default answer to getting more power has always been straightforward: build bigger. But there’s a ceiling — physical, logistical, and economic — to how large a single rotor can grow. Dual-rotor turbines offer a different path, placing two smaller rotors on one tower and sharing infrastructure while multiplying output.
Simulations suggest they improve wake recovery too, meaning air behind them regains speed faster and leaves more energy available for turbines further downwind.
Research and industry interest has grown steadily. Companies like EnBW and Aerodyn deployed scaled prototypes in the German Baltic Sea. In 2024, Chinese manufacturer Ming Yang Smart Energy launched a 16.6 MW floating dual-rotor — the world’s largest floating wind turbine — and by late 2025 had announced plans for an even more ambitious 50 MW dual-rotor concept.
Multi-rotor designs may also cut maintenance and construction costs. Simulations suggest they improve wake recovery too, meaning air behind them regains speed faster and leaves more energy available for turbines further downwind.
Building the experiment: two rotors, one wind tunnel
To study that interaction directly, researchers at the University of Oldenburg used two MoWiTO 0.6 model turbines, each 0.58 meters in diameter, placed just 1.07 rotor diameters apart in a Göttingen-type wind tunnel. One rotor spun clockwise; the other, counterclockwise.
Nineteen hot-wire sensors measured wake velocities from 0.75 to 10 diameters downstream, capturing average wind speeds and turbulent fluctuations alike. Two configurations were tested: “counter-right” (CR), with the counterclockwise rotor on the right, and “counter-left” (CL), with it on the left. For each, turbines were yawed symmetrically across nine settings ranging from 20 degrees inward to 20 degrees outward.
How spin direction rewrites the wake
Before running dual-rotor tests, the researchers measured each turbine’s wake individually — and rotational direction alone shapes where a wake goes, even before yaw enters the picture.
A clockwise-spinning rotor deflects its wake more readily to the right; a counterclockwise rotor deflects more readily to the left. The asymmetry traces back to the turbine tower, where wake rotation pulls the tower’s shadow into the measurement plane on one side and creates elevated turbulence. When yaw pushes the wake toward that turbulent side, mixing accelerates and deflection strengthens.
At zero yaw, CR and CL configurations already produce dramatically different wake widths at 10 diameters downstream. CR stays narrow. CL spreads to roughly 1.25 diameters on each side. Spin direction is the starting condition that determines everything else.
Two strategies for faster wake recovery
The yaw experiments revealed two distinct paths to better wake recovery — and which path works depends entirely on which rotor sits where.
The first is wake centroid deflection. Yawing CR turbines 20 degrees inward drives both wakes toward the centerline, merging them into a narrow band less than one rotor diameter wide by 6 diameters downstream. Relative wind speed at 10 diameters exceeds 0.8, a strong recovery by any measure.
The second is induced wake collision. Yawing CL turbines 20 degrees outward pushes the wakes apart; undisturbed air rushes toward the centerline and tip vortices break down rapidly. The CL outward case reaches relative wind speeds above 0.75 at 10 diameters, with recovery beginning within just 1 diameter of the rotor plane. Nearly all yawed configurations outperformed the zero-yaw baseline.
What this means for wind farms — and what comes next
That breadth matters practically. If only a narrow yaw setting produced gains, real-world implementation would demand precise, continuous control. The data suggest something more forgiving — yaw control of dual rotors appears viable across a meaningful range of angles.
There is a cost. Yawing turbines 20 degrees reduces the dual rotor’s own power output by roughly 12.6 percent compared to the unyawed case, the same trade-off wind farm operators already accept with single-rotor yaw steering. Whether it pays off depends on farm layout, turbine spacing, and how many rows sit downstream.
Real-world conditions may improve the picture further. The wind tunnel used laminar inflow, which slows tip-vortex breakdown; more turbulent inflow — the norm offshore — would likely accelerate that breakdown and amplify both strategies at full scale. As Ming Yang’s 50 MW concept moves from announcement toward reality, the answers won’t stay academic for long.
Reference: Maus, J., Peinke, J., and Hölling, M.: Exploring wake interactions in a counter-rotating dual-rotor system for different yaw configurations: an experimental study, Wind Energ. Sci., 11, 4111–4123, https://doi.org/10.5194/wes-11-4111-2026, 2026.
Daniel García is an Editor-in-Chief with strong expertise in structural work and engineering principles. He combines this technical foundation with deep knowledge of energy, spatial design, and emerging technologies, bringing a forward-thinking and analytical approach to editorial leadership.
