Climate change and the energy transition are often discussed separately, but many of the processes governing both are rooted in fluid dynamics. In the atmosphere, clouds and turbulence transport heat and moisture; in the ocean, differences in temperature and salinity, together with winds and meltwater, shape major currents such as the Atlantic Meridional Overturning Circulation (AMOC). Fluid dynamics is equally important for energy technologies. In wind energy, clouds, turbulence, and daily heating and cooling influence how much energy reaches the turbines and how quickly the slower air behind them recovers. The safe transport of LNG, a major energy carrier, requires understanding how the liquid moves inside ship tanks. Across five presentations, we show how computer simulations and laboratory experiments uncover the physics of these processes at scales ranging from millimeters to thousands of kilometers. Together, the talks connect climate science with the development of safer, more reliable, and more efficient energy systems.
Davide Selvatici: Clouds and Offshore Wind Farms
Clouds cover about two-thirds of the planet, and low clouds over the oceans are among Earth’s most effective coolers. They reflect sunlight back into space and emit infrared radiation from their upper layers, cooling the air there. This cooling sets the air below in motion. Cooler air sinks and warmer air rises, mixing the atmosphere beneath the clouds and drawing warmer, drier air down from above. This circulation extends down to the height of offshore wind turbines. Using high-resolution computer simulations, we study how clouds and wind farms influence each other. Turbines extract energy from the wind and create wakes of slower-moving air, which can reduce the output of turbines farther downstream. Cloud-driven mixing carries faster-moving air down toward the turbines, helping the wakes recover sooner and making more wind energy available to downstream turbines and neighboring wind farms. Wind farms also influence the atmosphere and clouds. A large wind farm slows the incoming air and pushes some of it upward, generating broad waves in the layered atmosphere known as gravity waves. When these waves reach the clouds, they raise and lower the cloud layer and change the amount of water it contains. This affects how much sunlight the clouds reflect. The resulting cloud patterns can stretch for tens of kilometers and are visible in satellite images. Most wind farm models miss this two-way connection because they assume a dry, cloud-free atmosphere. These findings show why clouds must be considered when predicting both the performance and wider atmospheric effects of future offshore wind farms.
Manideep Pasupula: Wind Farms Through Day and Night
The same wind farm can produce very different amounts of power at noon and midnight. During the day, sunlight warms the surface, air rises, and the lower atmosphere mixes. After sunset, the surface cools, mixing weakens, and a fast band of wind called a low-level jet can form near turbine height. The jet boosts the front rows, but weak mixing cannot replace the energy they remove, so long trails of slower air cut output farther downstream. The difference is large. Around noon and in the evening, the wind behind the 49-turbine wind farm returns close to its incoming speed within about six kilometers. At night and in the early morning, the slowdown can persist beyond 20 kilometers. When the jet fades after sunrise, production reaches its daily minimum. As the surface warms, stronger mixing brings faster air down and helps downstream output recover. Our simulations show how the seasons reshape this cycle. Stronger summer heating promotes mixing and lets the farm use the wind more efficiently. In winter, weaker heating leaves a shallower mixed layer beneath stronger atmospheric layering. Under these conditions, the farm’s influence extends farther upwind. It slows the wind before it reaches the first turbines and generates atmospheric gravity waves, ripples in layered air whose pressure changes extend beyond the farm. The wind resource is not a fixed input. It changes with the hour and the season, while the farm itself reshapes the flow. Capturing this interaction is essential for predicting production and integrating more wind power into a reliable energy system.
Giuseppe Vacca: Ice Melting Effects on Thermohaline Circulation
Ocean currents carry heat, salt, and nutrients around the Earth, making them central to Earth’s climate. One of the most important is the Atlantic Meridional Overturning Circulation (AMOC), which transports warm surface water northward through the Atlantic and returns colder water southward at depth. Both winds and density differences driven by temperature and salinity shape this circulation. Heat diffuses through water much faster than salt. When their effects on density oppose each other, this mismatch can drive a flow known as double-diffusive convection. We study this physics in a simplified “AMOC in a box,” where temperature and salinity vary from one side to the other. Simulations reveal four circulation patterns. Temperature controls one extreme and salinity the other. Between them, one state separates the water into layers that suppress the transport of both heat and salt. Another produces narrow, oscillating salt fingers that enhance salt transport while leaving heat transport almost unchanged. In this idealized system, the AMOC most closely resembles the temperature-driven regime. The simulations suggest that additional glacial meltwater could shift the balance toward a different regime, changing how heat and salt are transported. This highly simplified box cannot predict the future of the real AMOC, which also depends on winds, geography, and many other processes. Instead, it isolates physical mechanisms that larger climate models need to represent.
Simen Bootsma: Melting Ice at Larger Scales
How fast an iceberg melts depends on currents created by its own meltwater. Melting cools and freshens the water beside the ice, changing its density and motion. Under the conditions studied, increasing salinity first slows melting and then speeds it up again. At low salinity, cold water sinks along the ice. At intermediate salinity, buoyant meltwater rises along it while colder, saltier water sinks farther out. Because these currents oppose each other, the overall flow weakens and melting slows. The shear between them also carves scalloped patterns into the ice. At high salinity, the rising meltwater dominates and melting accelerates again. Salinity therefore does more than alter the melt rate. It determines which circulation pattern develops. These findings come from cylinders 30 centimeters high and 5 centimeters across. A taller ice face gives the flow more room to develop and possibly change character. To test whether the same regimes persist, we are now melting cylinders up to two meters high in a large silo containing fresh or salt water, an almost sevenfold increase in height. Underwater cameras track the changing shape, including whether scallops still form, while tiny particles reveal the surrounding currents. Moving from 30 centimeters to two meters will help connect controlled laboratory studies to natural icebergs and improve estimates of their lifetimes and the rate at which they release freshwater into the ocean.
Devaraj van der Meer: Impact of a Boiling Liquid
When engineers design ships to carry cryogenic fuels, such as liquid natural gas (LNG) or liquid hydrogen (LH₂), they need to deal with the violent motion of the fuel inside the tank, which causes a relentless succession of wave impacts on its walls when the ship travels through rough seas. To do so, engineers rely on the vast body of existing research on water-wave impacts in air, which they apply to the situation of interest. There is, however, one big problem: during transport, cryogenic fuels are in thermal equilibrium with their own vapor, a situation that is fundamentally different from that of water and air. Unlike an inert gas such as air, the vapor may condense during impact. The open question is whether, and how, this affects the forces and pressures exerted on the wall. In this talk, we will review the basic concepts that govern the impact of a liquid wave on a solid wall and discuss the influence of the gaseous medium (air or vapor) in which the impact takes place. We will then turn to the influence of phase change (condensation), which we investigate in three well-controlled experimental settings. Our results show that the pressures experienced by the wall may become up to one hundred times larger than those in a comparable water–air impact. We will shed light on the physical mechanisms behind this dramatic increase and show how the resulting insights can be generalized to cryogenic fuels such as LNG and LH
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