宇宙惑星科学特論IV

粉粒体物理の基礎，衝突抵抗力や変形力学などについて学ぶ．粉粒体は地球惑星の表層において砂，石，雪，レゴリス，ダスト凝集体などの様々な形で普遍的に存在する．これらの粉粒体はしばしば直感に反した複雑な挙動を示し，その理解は簡単ではなく統合的理解に向けて未だ道半ばの状態である．本講義では，粉粒体の物理的理解の基礎から最近の展開までを学ぶ．まずは連続体力学の基本を必要最低限復習し，続いて地球惑星スケールの現象を理解するために重要となるスケーリングと次元解析の手法を学ぶ．その後，粉粒体が関わる衝突や変形，緩和などの現象について主にスケーリングの手法に則して理解し，その地球惑星科学適応用の議論を行う．
In this course, fundamentals on granular physics and its application to geophysical phenomana including impact drag and deformation will be provided. Granular matter is ubiquitous on earth and planetary surfaces. Examples include sand, pebbles, snow, regolith, dust aggregates, etc. The simple but nonlinear characteristics of such granular materials yield various counter-intuitive phenomena. The state of the art of granular physics to understand varisou natural phenomena will be lectured although the granular physics is still far from complete understanding. First, continuum mechanics is briefly reviewed. Then, scaling and dimensional analysis that are crucial concepts to consider planetary-scale phenomena will be introduced. Then, fundamental aspects and some advanced topics on granular physics will be introduced mainly based on the scaling method. Particularly, granular impact drag and mechanics on deformation and relaxation of granular matter will be focussed.