A numerical study of vortex shedding from flat plates with square leading and trailing edges

Abstract

This paper describes a numerical study of the flow around flat plates with square leading and trailing edges on the basis of a finite-difference analysis of the two-dimensional Navier—Stokes equations. The chord-to-thickness ratio of a plate, d/h, ranges from 3 to 9 and the value of the Reynolds number based on the plate's thickness is constant and equal to 103. The numerical computation confirms the finding obtained in our previous experiments that vortex shedding from flat plates with square leading and trailing edges is caused by the impinging-shear-layer instability. In particular, the Strouhal number based on the plate's chord increases stepwise with increasing d/h in agreement with the experiment. Numerical analyses also provide some crucial information on the complicated vortical flow occurring near the trailing edge in conjunction with the vortex shedding mechanism. Finally, the mechanism of the impinging-shear-layer instability is discussed in the light of the experimental and numerical findings.

APPLICATION OF A MODIFIED k–ε MODEL TO THE PREDICTION OF AERODYNAMIC CHARACTERISTICS OF RECTANGULAR CROSS-SECTION CYLINDERS

“…One thing common to all the above methods is that their results are meaningful only when a su$cient spatial resolution is employed; therefore, these methods are memory intensive and require a lot of processing time. Ohya et al (1992) demonstrated that using a 2-D analysis it was possible to simulate the discontinuity of Strouhal number for 6)06B/D68)0 at Re"10. Nozu & Tamura (1997) pointed out the variation of #ow mechanisms around a square cylinder using 3-D computation, showing that 3-D structures begin to appear already as early as Re"2;10, and clusters of small-scale eddies which are a manifestation of three-dimensionality exist in the vortex structure of the wake at Re"10.…”

Self-Sustained Oscillations in Flows Around Long Blunt Plates

“…The #ow around rectangular plates in the absence of any external forcing has been studied previously both experimentally and numerically (Nakamura et al 1991;Ohya et al 1992). The vortex shedding from the leading edge of the plate generally locked to a single frequency at low Reynolds numbers [up to Re&3000, Nakamura et al (1991)].…”

“…In the case of Ohya et al (1992) where it was observed, the trailing-edge shedding was not considered to be part of the feedback loop but merely led to contamination of the downstream wake. The present study approaches the problem of natural shedding modes from a di!erent perspective in order to establish the importance of trailing-edge shedding to the self-sustained oscillations.…”

PIV measurement of separated flow over a blunt plate with different chord-to-thickness ratios

“…However, elongating the plate in the streamwise direction weakens the interaction and introduces considerable complexity into the features of the separated shear layers, which are highly related to those of the impinging shear layer and the vortices that are shed from the leading edge. The characteristics of the shedding vortices superimposed in the separated shear layer above the plate play a significant role in flow-induced structural vibration and acoustics (Ohya et al, 1992). Understanding the characteristics of vortex shedding from an elongated blunt body and the influence of vortex shedding on the separated shear layer is highly desirable.…”