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## Graduate School of Science and Engineering

Mechanical Engineering

### Physics Laboratory

From questions to creativity

#### Staff

#### Research Topics

- Self-organized structure and statistical theory of macroscopically disordered systems

#### Research Contents

The Physics Laboratory aims to educate students to apply logical thought processes based on scientific knowledge to analyze familiar complex phenomena and to be able to think creatively. Therefore, the students’ research topics are diverse, with each student conducting projects to clarify the physics of phenomena that interest them.

Fluid phenomena such as waves and vortices that we experience in everyday life follow deterministic equations and exhibit complex and diverse motions due to non-linearity and high degrees of freedom.

As we can note from Da Vinci sketches, physics has a long history of attracting researchers from diverse fields who have developed a magnificent body of theory. However, uncharted areas of research still remain and the new concepts of soliton and chaos have appeared. Finding solutions to difficult problems that have remained historically unresolved requires a new integrated approach through multidisciplinary joint research that fully exploits the features of today’s information age.

Our current topics of interest include the following.

Fluid phenomena such as waves and vortices that we experience in everyday life follow deterministic equations and exhibit complex and diverse motions due to non-linearity and high degrees of freedom.

As we can note from Da Vinci sketches, physics has a long history of attracting researchers from diverse fields who have developed a magnificent body of theory. However, uncharted areas of research still remain and the new concepts of soliton and chaos have appeared. Finding solutions to difficult problems that have remained historically unresolved requires a new integrated approach through multidisciplinary joint research that fully exploits the features of today’s information age.

Our current topics of interest include the following.

1. Self-organized structure and cooperative phenomena in disordered systems

Despite the overall disorder of the system, structures can appear spontaneously. The elements can also accumulate into an organization with a single function. We are attempting to physically elucidate why systems or nature shows a preference for such structures and why each element plays a role.

2. Statistical theory of macroscopically disordered systems

Statistical theories supporting the solution of the complex fluctuations and the population of solutions are effective in multi-dimensional chaos, mixing, and turbulence. It is important to pursue these statistical laws, to clarify their dependence on macroscopic conditions, and to what degree they are independent.

3. Stability and pattern dynamics

When control parameters are changed, the regular patterns (solutions) can become unstable and branch to new solutions, making a transition to a more complex (disordered) state.

4. Nonlinear wave phenomena

The linear phenomena of reflection, refraction, interference, diffraction, and scattering are known for waves such as light, ripples and sound. However, the consideration of nonlinear effects leads us to an extensive range of phenomena from regular waves like solitons to complex waves such as the wind-driven turbulent waves typical in the ocean.

5. Interaction between flow and objects

The movement of an object through a fluid, such as a curving and flying ball, and movement of a fluid through an object, such as flow through a pipe or the flow of water in a bay, is of industrial importance as well as academic interest.

6. Geophysical fluid dynamics and environmental problems

The movement of a fluid within the atmosphere and ocean are well known as theconvection, ocean currents and waves. Noise and the dispersion of pollutants are known as environmental problems. These are important issues that are closely related to our everyday lives.

7. Singularities and the existence of solutions in nonlinear partial differential equations

Knowledge of the mathematical properties of governing equations, such as the Navier-Stokes equations, is extremely important for a physical understanding. For example, see “millennium prize problems."

8. Emergent functions of organisms and cooperating groups

As represented by organisms, the properties and functions of an organization depend on the arrangement and combination of the components. We investigate the mechanism and applications of such emergent function.

9. Mechanism of environmental adaptation

Organisms change and evolve through interactions with the environment. They have become optimized by accumulated learning. We undertake numerical evaluations of the mechanisms of environmental adaptation.

Despite the overall disorder of the system, structures can appear spontaneously. The elements can also accumulate into an organization with a single function. We are attempting to physically elucidate why systems or nature shows a preference for such structures and why each element plays a role.

2. Statistical theory of macroscopically disordered systems

Statistical theories supporting the solution of the complex fluctuations and the population of solutions are effective in multi-dimensional chaos, mixing, and turbulence. It is important to pursue these statistical laws, to clarify their dependence on macroscopic conditions, and to what degree they are independent.

3. Stability and pattern dynamics

When control parameters are changed, the regular patterns (solutions) can become unstable and branch to new solutions, making a transition to a more complex (disordered) state.

4. Nonlinear wave phenomena

The linear phenomena of reflection, refraction, interference, diffraction, and scattering are known for waves such as light, ripples and sound. However, the consideration of nonlinear effects leads us to an extensive range of phenomena from regular waves like solitons to complex waves such as the wind-driven turbulent waves typical in the ocean.

5. Interaction between flow and objects

The movement of an object through a fluid, such as a curving and flying ball, and movement of a fluid through an object, such as flow through a pipe or the flow of water in a bay, is of industrial importance as well as academic interest.

6. Geophysical fluid dynamics and environmental problems

The movement of a fluid within the atmosphere and ocean are well known as theconvection, ocean currents and waves. Noise and the dispersion of pollutants are known as environmental problems. These are important issues that are closely related to our everyday lives.

7. Singularities and the existence of solutions in nonlinear partial differential equations

Knowledge of the mathematical properties of governing equations, such as the Navier-Stokes equations, is extremely important for a physical understanding. For example, see “millennium prize problems."

8. Emergent functions of organisms and cooperating groups

As represented by organisms, the properties and functions of an organization depend on the arrangement and combination of the components. We investigate the mechanism and applications of such emergent function.

9. Mechanism of environmental adaptation

Organisms change and evolve through interactions with the environment. They have become optimized by accumulated learning. We undertake numerical evaluations of the mechanisms of environmental adaptation.

#### Keywords

- Fluid phenomena
- Macroscopically disordered system
- Statistical theory
- Self-organization
- Cooperative phenomena

- Stability
- Pattern dynamics
- Non-linear wave
- Vortex dynamics