Interaction Between Vortex Rings and a Separated Shear Layer: Towards Active Control of Separation Zones

The formation process of a vortex ring generated by a pulsating jet flow, which is called the cyclic vortex ring, is investigated experimentally with PIV measurement. The waveform of the jet flow is conducted using sine curves by changing the amplitude of Reynolds' numbers Re 0 of 1200～5040 and Womersley numbers α of 12.5～24.4. The results indicate that the formation process of the cyclic vortex ring is different from the laminar vortex ring. Another vortex ring which is formed from separated wall boundary layers in the nozzle during the suction period, which is called the separation vortex ring, is transported toward the nozzle exit during the discharge period. This separation vortex ring interferes with the formation process of the cyclic vortex ring at the nozzle exit plane. The circulation of the separation vortex ring depends on the pulsating conditions of the jet flow. Distribution of the vorticity around the core center of the cyclic vortex ring is in good agreement with the Oseen vortex model. The formation process of the cyclic vortex ring is classified into three categories, depending on Strouhal number.

show abstract

Steady and Pulsating Flow Past a Heated Rectangular Cylinder(s) in a Channel

Saxena

2018

Journal of Thermophysics and Heat Transfer

View full text Add to dashboard Cite

In the present study, the effect of laminar steady (Re=100, Pr=0.74) and pulsating flow (4 Hz and amplitude 0.4) is numerically studied over a centrally located heated rectangular cylinder of varying aspect ratio (W/H=1 to 8) in a confined channel using finite volume method. To study the influence of channel walls at a fix distance, eccentric placement of the highest aspect ratio cylinder(s) with two gap ratios (B/H) of 5 and 0.5 is done. Isotherms and streamlines of the flow are presented along with lift and drag coefficients. Further, FFT spectral analysis is performed to evaluate the vortex shedding frequency of the flow upon interaction with the cylinder(s). For single cylinder at the center position in the channel, natural vortex shedding and "lock-on" shedding occurs for lower aspect ratio cylinder under steady and pulsating flow, respectively. An increase in aspect ratio has a suppressi ng effect on the vortex shedding with a substantial decrease in the heat transfer over the cylinder. Placing two cylinders (W/H=8) at a geometrically symmetrical eccentric location of B/H=5shows an extra peak at half of the flow inlet frequency in FFT spectral curve that possibly confirms the "lock-on" shedding with increased heat transfer over the cylinder.

show abstract

Interaction Between Vortex Rings and a Separated Shear Layer: Towards Active Control of Separation Zones

Cited by 4 publications

References 19 publications

A Framework to Design Controllers for Engineering Applications of Transverse Jets

A Framework to Design Controllers for Engineering Applications of Transverse Jets

Formation Process of Vortex Ring Generated by a Pulsating Jet Flow

Steady and Pulsating Flow Past a Heated Rectangular Cylinder(s) in a Channel

Contact Info

Product

Resources

About