Comparison with Fluid Dynamics: Fluid dynamics assumes constant density (incompressible), while gas dynamics involves changing density (compressible flow).
Compressibility
Definition: Related to the density gradient; measures how density of a gas changes under various conditions like pressure and temperature.
Processes Affecting Density:
Change in pressure (compress/expand gas).
Change in temperature (heat/cool gas).
Relationship:
Specific volume (v) as a function of temperature (T) and pressure (P).
Differential change represented as dv/v, involving derivatives w.r.t. T and P.
Isothermal Compressibility: Expansion at constant pressure.
Coefficient: High coefficient indicates highly compressible gas.
Density: Simplifies calculations by using density rather than specific volume.
Definitions and Concepts
Mach Number (M): Ratio of flow speed to speed of sound in the medium.
M << 1: Incompressible flow.
M ≥ 1: Compressible flow.
Speed of Sound:
Determined by how fast compression and expansion waves travel through a medium.
Varies between mediums: e.g., 340 m/s in air vs. 5000-6000 m/s in steel.
Thermodynamic Systems and Properties
System: The portion of the universe under study.
Closed System: No mass exchange, only energy exchange.
Open System: Mass and energy exchange allowed.
Isolated System: No mass or energy exchange.
State: Defined by measurable properties like pressure, temperature, and volume.
Intensive Properties: Independent of mass (e.g., pressure, temperature).
Extensive Properties: Dependent on mass or size (e.g., volume, mass).
Thermodynamic Processes
Process: Change from one state to another.
Path: Sequence of states during a process.
Laws of Thermodynamics
Zeroth Law: If system A is in equilibrium with system B, and system B is in equilibrium with system C, then system A is in equilibrium with system C.
Basis for defining temperature and equilibrium.
First Law: Energy conservation; energy cannot be created or destroyed.
Second Law: Entropy increase; spontaneous processes increase the entropy of the universe.
Entropy: Measures disorder or randomness.
Practical Considerations
Mathematical and Physical Intuition: Emphasis on deriving equations and understanding physical implications.
Course Scope: Starting from basics, build up to graduate-level analysis.
Upcoming Topics
Review of thermodynamic variables.
Definition of gases and perfect gases.
Study of thermodynamic processes and laws of mechanics.