3.2 Basic Physical Laws of Fluid Mechanics All the laws of mechanics are written for a system, which state what happens when there is an interaction between the system and it's surroundings If m is the mass of the system Conservation of ma5质量守→ m= const or dm=0 Newtons second aw →F=m=mm= Angular dH momentum →M H=∑(×1)·m dt First law of do dw dE thermodynamic3.2 Basic Physical Laws of Fluid Mechanics All the laws of mechanics are written for a system, which state what happens when there is an interaction between the system and it’s surroundings. If m is the mass of the system Conservation of mass(质量守恒)  0 dm m const or dt = = Newton’s second law  F ma = dV m dt = ( ) d mV dt = Angular momentum  dH M dt = H r V m =   ( ) First law of thermodynamic  dQ dW dE dt dt dt − =