16Division ofNonlinear MechanicsMechanics of Fluids andThermo-uidsThermal Engineering and Science Group■Prof.：Genta KAWAHARA■Assoc.Prof.：Susumu GOTO■Assis.Prof.：Hideshi ISHIDA, Masaki SHIMIZUThis group performs fundamental researches on thermo-uid phenomena and their application to engineering problems. Research topics include eluci-dation and control of structures, dynamics and statis-tical properties of fully developed turbulent ows, prediction and control of subcritical transition to tur-bulence, elucidation of transfer mechanisms of heat and momentum in turbulent ows and its application to heat transfer enhancement and drag reduction, description and control of turbulence dynamics using unstable periodic motion, and chaotic behavior in natural convection elds.Fluid Mechanics Group■Prof.：Nobumasa SUGIMOTO■Assoc.Prof.：Takao YOSHINAGA■Assis.Prof.：Yosuke WATANABE, Dai SHIMIZUThis group studies nonlinear waves and vibrations in uids and in uid-structure systems in view of con-tributions to energy, environmental problems and micro-processing. The specic topics include: (1) non-linear acoustic problems such as generation of acous-tic soliton, novel methods for suppression of shocks and thermoacoustic eects with applications to heat engines; (2) nonlinear capillary waves involving free surface or interface such as break-up of liquid sheet or liquid bridge and Marangoni eect for surface ten-sion due to temperature or concentration variations; (3) nonlinear waves and vibrations in uid-structure systems such as localization and delocalization in a spatially discrete and periodic structure. All of the above are studied analytically and numerically by combining asymptotic and computational methods such as the level-set method and the discrete vortex method.Mechanics of Solid MaterialsStrength of Structure and Materials Group■Prof.：Hidetoshi KOBAYASHI■Assoc.Prof.：Keitaro HORIKAWA■Assis.Prof.：Kenichi TANIGAKIThis group studies mechanical behavior of structure and structural materials focusing on the eects of impact loading and hydrogen. Specic topics are me-chanical behavior of materials and light structure such as metal and polymaer foams under impact loading, biomimetics for plant structure and materi-als, hydrogen embrittlment in aluminum alloys for high pressure hydrogen gas tank, elucidation of hydrogen diusion in metallic materials by means of hydrogen microprint technique, development of hydrogen permeation membranes, electromagnetic phenomena of rocks during impact deformation and phenomena induced by high-speed penetration into granular and geological media.Solid Mechanics Group■Prof.：Masahiko HIRAO■Assoc.Prof.：Hirotsugu OGI■Assis.Prof.：Nobutomo NAKAMURAResonance of sound and ultrasound is studied to evaluate functional materials, develop elastic-wave devices, detect the remaining life of aging structural materials, and apply the sonoluminescence-photocatalyst interaction to decompose organic com-pounds. In particular, the electromagnetic-acoustic resonance (EMAR) has been invented, which for the rst time makes it possible to measure the elastic and inelastic properties of composites, electric mate-rials, thin lms, superconductors, metal glasses, etc. These acoustic measurements incorporate with the micromechanics theoretical models to elucidate the physical acoustic phenomena from the mechanical viewpoint.Research and education in the Division of Nonlinear Mechanics aim at establishing new elds of nonlinear mechanics from various mechanical phenomena and problems arising from man-made objects and/or nature, to create novel functions and machines, and at fostering students with such capabilities. Nonlinear mechanics uncover laws and principles underlying apparently complicated phenomena to describe the real world more precisely than the "linear mechanics." Specic examples range over chaos in turbulence, solitons in nonlinear waves, mesoscopic mechanics from micro- to nano-scales, localization of deformation, crack, fracture and so on. The Division consists of four groups specializing thermal engineering and science, uid mechanics, fracture mechanics and solid mechanics with contributions to energy and environmental problems, new materials, and security against failure of mechanical systems.