Force- and Loss-Free Transitions Between Vortex Flow States

Keller, Jakob J.; Egli, Walter Alfredo; Exley, J.

doi:10.1007/978-1-4612-4678-7_5

Cited by 2 publications

(3 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The swirl ratio of the near-solid-body rotation at this section is also the swirl number of the inlet flow . Using the works of Rusak et al [22] and Keller et al [29], the critical swirl levels for these two vortex flow profiles can be computed. A summary of the results is given in Table 1.…”

Section: B Theoretical Prediction Of Vortex Breakdownmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Computational Study of Nonreacting Vortex Breakdown in a Swirl-Stabilized Combustor

et al. 2010

View full text Add to dashboard Cite

Nonreacting flow experiments are conducted in a swirl-stabilized combustor with several configurations of a triple annular research swirler fuel injector. Particle imaging velocimetry is used to measure mean axial, radial, and tangential distribution of the velocity field, from which the swirl ratio and the position of vortex breakdown are calculated for each injector configuration. Numerical simulations based on the Reynolds-averaged Navier-Stokes model equations of nonreacting flows provide insight into the characteristics of the axisymmetric vortex breakdown phenomenon in a circular, finite-length pipe with a sudden expansion downstream of a concentric, circular inlet pipe. Results show that flow states with vortex breakdown can be simulated numerically. Good agreement is found between the results of the simulations and available theoretical predictions for the first appearance of breakdown downstream of the pipe expansion plane, as well as its first appearance in the inlet pipe section as the inlet swirl level is increased. Good agreement is also shown between the measured experimental data, simulations, and theoretical predictions. It is demonstrated that the theoretical criteria and numerical simulations can be used to predict the appearance and location of vortex breakdown for several different nozzles of varying swirl numbers relevant to the stability of lean, premixed combustion.

show abstract

Section: B Theoretical Prediction Of Vortex Breakdownmentioning

confidence: 99%

“…Comparison of analytical VB criteria by Rusak et al[22] and Keller et al[29] with numerical results.…”

mentioning

confidence: 98%

Experimental and Computational Study of Nonreacting Vortex Breakdown in a Swirl-Stabilized Combustor

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The trend of the data corresponds to the velocity variation one would expect for stagnation flows. Keller et al 25 have calculated the streamlines corresponding to the transition (breakdown) of a Rankine vortex for the case of steady flow. Their patterns clearly show the nature of the stagnation flow and the fact that rapid deceleration of the core occurs over a very short streamwise distance of the order of the radius of the vortex core.…”

Section: E Velocity Of Vortex Corementioning

confidence: 99%

Leading-edge vortices due to low Reynolds number flow past a pitching delta wing

Atta

Rockwell

1990

AIAA Journal

View full text Add to dashboard Cite

Flow past a pitching delta wing is examined in a water channel for a range of mean angle of attack. The wing is perturbed sinusoidally over a tenfold range of reduced frequency, in order to determine the nature of the vortex development and breakdown. There occur two basic types of vortex development: at low frequencies, the vortex core develops in the upstream direction towards the apex; at high frequencies, there is ejection of the leading edge of the vortex core from the apex in the downstream direction. Correspondingly, the direction of the dynamic hysteresis loop of vortex breakdown location vs angle of attack is determined by the type of vortex development. During unsteady development of the vortex core, the axial velocity on the centerline of the vortex is essentially constant with distance along the core. At the onset of vortex breakdown, there is abrupt deceleration; the velocity variations in this region exhibit a similar form for a range of angle of attack and reduced frequency.Nomenclature C =chord f e -excitation frequency K = reduced frequency = irf e C/ UL x > -streamwise extent of deceleration along centerline of vortex core P = pitch of helical streamline Re = Reynolds number =U 00 C/v r = radius of helical streamline C/oo = freestream velocity u = axial velocity of leading-edge vortex u c -axial velocity on centerline of vortex ( w c)max = maximum value of axial velocity on centerline of vortex v e = swirl velocity of vortex x -distance from apex of wing along centerline of vortex core x b = distance of vortex breakdown from apex along centerline of core x' -distance along centerline of vortex core from onset of deceleration Xp = distance from apex along leading edge of wing to location of wire probe X R = reference location along leading edge of wing for evaluating parameters of vortex a = angle of attack a.= mean angle of attack \ e = effective wavelength = U w /f e = swirl angle = tan ~l V e /û max = maximum value of swirl angle 0 = angular deflection of helical streamline pattern v = kinematic viscosity

show abstract

Force- and Loss-Free Transitions Between Vortex Flow States

Cited by 2 publications

References 5 publications

Experimental and Computational Study of Nonreacting Vortex Breakdown in a Swirl-Stabilized Combustor

Experimental and Computational Study of Nonreacting Vortex Breakdown in a Swirl-Stabilized Combustor

Leading-edge vortices due to low Reynolds number flow past a pitching delta wing

Contact Info

Product

Resources

About