Computational Fluid Dynamics

The background image on the cover is the result of a computational fluid dynamics (CFD) analysis of wind flows around the MIT campus. The image views the campus from above with wind coming from the southwest. The color, size, and orientation of the arrows show the direction and speed of winds.

Computational fluid dynamics is a method of simulating fluid flows in a well-defined region—for example, an engine, a city block, an estuary, or the earth's atmosphere. Starting from initial conditions within and around the region, a CFD model numerically solves the mathematical equations of motion to produce velocities, pressures, temperatures, and other characteristics at points throughout the region.

Professor Qingyan Chen and his colleagues in the Building Technology Program performed the analysis as part of their examination of the environmental impacts of MIT's new Ray and Maria Stata Center (Building 32).

Inset Cover Photos (top to bottom)

Graduate student Zhiqiang Zhai works with CFD images of airflows around the MIT campus.

Professors Qingyan Chen (left) and Leon Glicksman and graduate student Meredith Elbaum examine models of buildings they are designing for Shanghai and Shenzhen, in collaboration with researchers from Chinese universities and development companies. CFD airflow studies show that using larger numbers of lower-rise buildings carefully designed and laid out can provide as many living units and use less energy than fewer, widely spaced high-rise buildings.

The current construction boom in China is yielding many tall towers similar to Western buildings both in style and in high energy consumption. Using heat-transfer models and CFD analysis of airflow among and within buildings, MIT researchers have shown that energy use can be dramatically reduced if buildings are designed to maximize natural ventilation during the hot summer months and solar heat gain during the cold winter months.

Top two inset photos by Stephen Connors, LFEE; bottom photo by Getty Images.

Computational Fluid Dynamics

The image on the front cover was created using a technique called laser-induced fluorescence. At the Sloan Automotive Laboratory, seeing how lubricating oil moves inside an engine cylinder helps researchers understand how engines consume oil and identify design changes that will give better lubrication, reducing friction and increasing fuel economy. Benoist Thirouard, PhD 2001, took this split-second image through a 1 cm by 2 cm sapphire window in the side of an engine cylinder. The image shows the thickness of the oil layer on the side of the piston. The horizontal blue lines indicate thin (~1 micron) layers where rings mounted on the piston slide along the window. Between the rings are red areas where oil occurs in thick clumps rather than being spread smoothly.

The images on the back cover are the result of a CFD analysis of swirling flows of fuel and air within the combustion chamber of a gas turbine engine. Pproduced by graduate student Jean-Claude Saghbini in Professor Ahmed Ghoniem's research group, the images show a sequence of three time-steps. Each time-step contains six cross sections along the cylindrical combustor, and the colors indicate the degree of swirling at a given location. Blue regions are swirling fastest, then green, yellow, and red. Accordingly, the light blue crescent in the fifth cross section rotates significantly from one time step to the next. Understanding and controlling fuel-air mixing is one key to achieving optimal conditions for self-ignition and efficient, clean combustion.

Inset Photos (Top to Bottom)

To produce images such as that on the front cover, graduate student Adam Vokac shines a laser through a sapphire window in a test engine. The laser causes a doping chemical in the lubricating oil to fluoresce at an intensity correlated with film thickness. The equipment was designed and built by Dr. Thirouard under the direction of Professor Douglas Hart.

Graduate student Jeremy Llaniguez uses a diesel test engine in a research program targeting clean transportation fuels. Tests include measuring nitrogen oxide and particulate emissions while burning low-sulfur diesel fuel and sulfur-free synthetic fuel, with and without a postcombustion cleanup system.

Devising sustainable transportation systems is a key part of the multidisciplinary research program mounted by the Laboratory for Energy and the Environment (LFEE) to understand and control air pollution in Mexico City.

Top two inset photos by Thane DeWitt, LFEE; bottom photo by Stephen Connors, LFEE.