isentropic flow

Isentropic flow

Compressible flow in which entropy remains constant throughout the flowfield. A slight distinction is sometimes made, especially in Europe, as follows. If the entropy of a fluid element moving along a streamline in a flow remains constant, the flow is isentropic along a streamline. However, the value of the entropy may be different along different streamlines, thus allowing entropy changes normal to the streamlines. An example is the flowfield behind a curved shock wave; here, streamlines that pass through different locations along the curved shock wave experience different increases in entropy. Hence, downstream from this shock, the entropy can be constant along a given streamline but differs from one streamline to another. This type of flow, with entropy constant along streamlines, is sometimes defined as isentropic. Flow with entropy constant everywhere is then called homentropic. See Compressible flow, Entropy, Isentropic process

Because of the second law of thermodynamics, an isentropic flow does not strictly exist. From the definition of entropy, an isentropic flow is both adiabatic and reversible. However, all real flows experience to some extent the irreversible phenomena of friction, thermal conduction, and diffusion. Any nonequilibrium, chemically reacting flow is also irreversible. However, there are a large number of gas dynamic problems with entropy increase negligibly slight, which for the purpose of analysis are assumed to be isentropic. Examples are flow through subsonic and supersonic nozzles, as in wind tunnels and rocket engines; and shock-free flow over a wing, fuselage, or other aerodynamic shape. For these flows, except for the thin boundary-layer region adjacent to the surface where friction and thermal conduction effects can be strong, the outer inviscid flow can be considered isentropic. If shock waves exist in the flow, the entropy increase across these shocks destroys the assumption of isentropic flow, although the flow along streamlines between shocks may be isentropic. See Adiabatic process, Boundary-layer flow, Shock wave, Thermodynamic principles, Thermodynamic processes

isentropic flow

[¦īs·ən′träp·ik ′flō]
(thermodynamics)
Fluid flow in which the entropy of any part of the fluid does not change as that part is carried along with the fluid.
References in periodicals archive ?
The model design parameters are found by solving analytically using governing isentropic flow relations (1) (2) (3), oblique shock wave relations (4) (5) by following the shock-on-lip condition.
Bearing the above assumptions in mind, at isentropic flow in an adiabatic shield, using the mass balance we can notate the following:
Az-Zo'bi, An approximate analytic solution for isentropic flow by an inviscid gas model.
The choked flow condition for an ideal gas or vapor based on isentropic flow is given by
th] that would occur for an isentropic flow condition of an ideal gas:
First, since the integration corresponds to one-dimensional isentropic flow, the calculated value of C* does not account for secondary effects such as the influence that real gas behavior has on the boundary layer development or on the curvature of the sonic line.
In the single hose constant acceleration system, the physics of isentropic flow have been enhanced by state-of-the art aerodynamic theory and design practice to produce media delivery systems (hose, applicator and nozzle) which provide maximum acceleration and velocity to the particles with minimum shock or turbulence at the nozzle exit.
In order to evaluate the flow of individual injectors (the dosage regularity), a mathematical model was developed, where, upon assuming the simplifications, the flow was based on an isentropic flow in an adiabatic shield.
Pressure at the throat was calculated by initially assuming that the isentropic flow in the converging section for each run crossed either the saturated liquid line or the saturated vapor line.
Finally the solution of flow conditions for a compressible fluid through a variable area duct without friction and heat transfer has a solution known as Isentropic flow [51, Ch.
The types of flow are classified as either isentropic flow of compressible ideal gas, laminar viscous flow, or mixed plane Couette and Poiseuille flow.
For isentropic flow, users select from four input parameters.