On unsteady flow in a two-dimensional cascade with in-passage shocks

1987 ◽  
pp. 391-402
Author(s):  
Kewal K. Puri
Keyword(s):  
Unsteady Flow ◽  
Two Dimensional

Two-dimensional leaps in near-critical flow over isolated orography

2005 ◽  
Vol 461 (2064) ◽  
pp. 3747-3763 ◽  
Author(s):  
E.R Johnson ◽  
G.G Vilenski
Keyword(s):  
Unsteady Flow ◽  
Equations Of Motion ◽  
Fold Increase ◽  
Flow Speed ◽  
Two Dimensional ◽  
Subcritical Flow ◽  
One Dimensional ◽  
Petviashvili Equation ◽  
Lee Wave ◽  
Supercritical Flows

This paper describes steady two-dimensional disturbances forced on the interface of a two-layer fluid by flow over an isolated obstacle. The oncoming flow speed is close to the linear longwave speed and the layer densities, layer depths and obstacle height are chosen so that the equations of motion reduce to the forced two-dimensional Korteweg–de Vries equation with cubic nonlinearity, i.e. the forced extended Kadomtsev–Petviashvili equation. The distinctive feature noted here is the appearance in the far lee-wave wake behind obstacles in subcritical flow of a ‘table-top’ wave extending almost one-dimensionally for many obstacles widths across the flow. Numerical integrations show that the most important parameter determining whether this wave appears is the departure from criticality, with the wave appearing in slightly subcritical flows but being destroyed by two-dimensional effects behind even quite long ridges in even moderately subcritical flow. The wave appears after the flow has passed through a transition from subcritical to supercritical over the obstacle and its leading and trailing edges resemble dissipationless leaps standing in supercritical flow. Two-dimensional steady supercritical flows are related to one-dimensional unsteady flows with time in the unsteady flow associated with a slow cross-stream variable in the two-dimensional flows. Thus the wide cross-stream extent of the table-top wave appears to derive from the combination of its occurrence in a supercritical region embedded in the subcritical flow and the propagation without change of form of table-top waves in one-dimensional unsteady flow. The table-top wave here is associated with a resonant steepening of the transition above the obstacle and a consequent twelve-fold increase in drag. Remarkably, the table-top wave is generated equally strongly and extends laterally equally as far behind an axisymmetric obstacle as behind a ridge and so leads to subcritical flows differing significantly from linear predictions.

Calculation of two-dimensional dispersion in a gas in unsteady flow in a porous medium

1983 ◽  
Vol 17 (5) ◽  
pp. 704-710
Author(s):  
E. G. Basanskii ◽  
V. M. Kolobashkin ◽  
N. A. Kudryashov
Keyword(s):  
Porous Medium ◽  
Unsteady Flow ◽  
Two Dimensional

A Lagrangian criterion of unsteady flow separation for two-dimensional periodic flows

2018 ◽  
Vol 39 (7) ◽  
pp. 1007-1018 ◽  
Author(s):  
Shuaibin Han ◽  
Shuhai Zhang ◽  
Hanxin Zhang
Keyword(s):  
Unsteady Flow ◽  
Flow Separation ◽  
Two Dimensional ◽  
Periodic Flows

A Note on the Estimation of Average Pressures from Instantaneous Velocities in Unsteady Flow

1967 ◽  
Vol 71 (678) ◽  
pp. 440-440
Author(s):  
C. J. Wood
Keyword(s):  
Unsteady Flow ◽  
Boundary Layers ◽  
Data Reduction ◽  
Bluff Body ◽  
Wake Vortex ◽  
Two Dimensional ◽  
Experimental Check ◽  
Velocity Measurements ◽  
Periodic Disturbance ◽  
Oncoming Stream

In a recent paper, the author described some experiments in which the average base pressure on a two-dimensional bluff body was estimated from a random sample of instantaneous velocity measurements taken in the irrotational flow outside the separating boundary layers at the trailing edge. Although the oncoming stream was steady, the flow near the model was subject to a periodic disturbance emanating from the wake vortex street. An experimental check showed that the pressure estimates obtained by using the steady Bernouilli equation were reasonably accurate. This note points out that the method of data reduction used in ref. 1 is not an approximation; it is exact.

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