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

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

isentropic flow

[¦īs·ən′träp·ik ′flō]
Fluid flow in which the entropy of any part of the fluid does not change as that part is carried along with the fluid.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Isentropic flow is assumed from measured inlet conditions (assumed to be stagnation conditions) to impeller inlet conditions (section 1 from Figure 8).
In each time range, using the method of characteristics for planar isentropic flow, (16) can be converted to ordinary differential equation.
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.
Valve flow is considered as one-dimensional isentropic flow [18, 19].
Yang, "Delta shock waves as limits of vanishing viscosity for 2-D steady pressure less isentropic flow," Acta Applicandae Mathematicae, vol.113, no.3, pp.323-348, 2011.
The choked flow condition for an ideal gas or vapor based on isentropic flow is given by
The mass flow rate through the valve [??] is usually expressed with reference to the theoretical mass flow rate [[??]] 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.
At the end of the hose, the spray nozzle gun actually consists of a convergent-divergent (isentropic flow) nozzle which exchanges pressure differential across the nozzle for a huge increase in air and particle velocity.
It should be pointed that as the valve lift increases the discharge coefficient (Cd) related to the curtain area decreases [39].So, at a higher lift, the relation between the actual flow rate and the isentropic flow rate is smaller than that of lower valve lifts.