1 / 20

HIGH SPEED FLOW

HIGH SPEED FLOW. 1 st Semester 2007 Pawarej CHOMDEJ fengpac@ku.ac.th 081 832 7854. Course Outline. Introduction to compressible flows Normal Shock Waves Oblique Shock Waves Prandtl - Mayer Flow Application Involving Shocks and Expansion Fans Flow with Friction Flow with Heat Transfer

talon-pena
Download Presentation

HIGH SPEED FLOW

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HIGH SPEED FLOW 1st Semester2007 Pawarej CHOMDEJ fengpac@ku.ac.th 081 832 7854

  2. Course Outline • Introduction to compressible flows • Normal Shock Waves • Oblique Shock Waves • Prandtl - Mayer Flow • Application Involving Shocks and Expansion Fans • Flow with Friction • Flow with Heat Transfer ------------------------ Midterm Examination ------------------------ • Linearized Compressible Flow • Airfoils in Compressible Flows

  3. Course Outline • Wings and Wing-Fuselage Combinations in Compressible Flows • Method of Characteristics • Computational Gas Dynamics • Hypersonic Flows

  4. Course assessment • Attendance, Presentation, Quiz and Homework 40 points • Attendance 10 points • Presentation 10 points • Homework 20 points • Midterm examination 30 points • Finalexamination 30 points

  5. Introduction to compressible flows • Compressible flow • Review of thermodynamics • Total (Stagnation) conditions • Isentropic flow • Supersonic flow • Shock waves • Definition • Characteristics

  6. Introduction to compressible flows • Review of thermodynamics • The first law of thermodynamics q + w = de • For a reversible process q - pd = de • InternalEnergy and Enthalpy • Internal energy e = CυT • Enthalpy h = e + P υ = CpT • Specificheat

  7. Introduction to compressible flows • Entropy • Theory of work laws in closed system • 2 Forms of energy transfer : Work and Heat • Area under Pressure-Volume diagram = Work (W) • Reversible expansion or compression P P dV V

  8. Introduction to compressible flows • Entropy • Area under T-s diagram = Heat Transfer (Q) • Reversible process • Specific entropy s , J/(kg K) T T ds s OR

  9. Introduction to compressible flows • The second law of thermodynamic (Irreversible process) • From the first law Tds = dh - dP = de +pd • Entropy change of a calorically perfect gas between two states or

  10. Introduction to compressible flows • Isentropic Processes • Isentropic → Constant Entropy • Reversible and Adiabatic process • No heat transfer to or from fluid dQ = 0 • Application in steady systems for gasses and vapors T ds = 0 s

  11. Introduction to compressible flows • Exercise • 1) A perfect gas is expanded adiabatically from 5 to 1 bar by the law PV1.2 = Constant. The initial temperature is 200°C. Calculate the change in specific entropy. R = 287.15 J/kgK,  =1.4

  12. Introduction to compressible flows • Isentropic Flow • Adiabatic and Reversible • No energy added, No energy losses • Small an gradual change in flow variables • ds = 0 h0 T0 P0 h0 T0 P0

  13. Introduction to compressible flows • Isentropic relation • For and adiabatic, reversible process with so

  14. Introduction to compressible flows • Total (Stagnation) conditions : • A point (or points) in the flow where V = 0. • Fluid element adiabatically slow down • A flow impinges on a solid object V1 V2 = 0

  15. Introduction to compressible flows • From Energy Equation and the first law of thermodynamics • Total enthalpy = Static enthalpy + Kinetic energy (per unit mass) • Steady and adiabatic flow h0 = const (h01 = h02) • Steady, inviscid, adiabatic flow T0 = const • Isentropic flow P0 = const and ρ0 = const (Slow down adiabatically and reversibly) • For a calorically perfect gas , h0 = CPT0or h = CP T h01 h02 h1 h2

  16. Introduction to compressible flows • Question • 2) Consider a point in a flow where the velocity and temperature are 230m/s and 375K respectively. Calculate the total enthalpy at this point. • 3) An airfoil is in a freestream where P∞ = 0.75 atm, ρ∞ = 0.942 kg/m3and V∞ = 325 m/s. At a point on the airfoil surface, the pressure is 0.62 atm. Assuming isentropic flow, calculate the velocity at the point.

  17. Introduction to compressible flows • Compressible flow • Density changes FLUIDS Incompressible Compressible ρ constant ρ varies

  18. Introduction to compressible flows • Compressibility • Measure of the relative volume change with pressure P+dp P υ υ+dυ

  19. Introduction to compressible flows • Compressibility Incompressible Flow P P P+ dp υ υ υ Compressible Flow P+dp υ

  20. Introduction to compressible flows • Entropy • Isentropic Relations • Compressibility • M < 0.3 : Incompressible flow • M > 0.3 : Compressible flow

More Related