Vortical structure in the wake of a transverse jet

Fric, T. F.; Roshko, A.

doi:10.1017/s0022112094003800

Cited by 1,084 publications

(624 citation statements)

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“…The wake-like tail behind a jet in a cross flow contains a "vortex bubble." 37 Fig. 19 that significantly negative values of the tangential mean velocity occur between r / d = 0.5 and 2.5 in the near-field region at x / d ഛ 6.…”

Section: Conditional Phase-averaged Statistics Of the Precessing Jmentioning

confidence: 82%

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Statistical analysis of the velocity field in a mechanical precessing jet flow

Nathan

2004

Physics of Fluids

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An experimental investigation of a precessing jet issuing from a mechanically rotating nozzle directed at an angle of ␣ = 45°relative to the axis of rotation is reported. Both conventional and conditional statistics of the velocity field of the jet were measured using a combined hot-wire and cold-wire (to identify any reverse flow) probe. Three distinct values (Ϸ0.005, 0.01, and 0.02) of the precession Strouhal number St p (ϵ rotation frequency ϫ nozzle diameter / jet exit bulk velocity) were used to assess the effect of varying St p . The measurements reveal that the Strouhal number in general has significant influence on the entire mixing field generated by a precessing jet. The occurrence of precession at all the Strouhal numbers of investigation produces a central recirculation zone at x ഛ 7d, where x is a distance measured from the rotating nozzle exit. A critical Strouhal number, i.e., St p,cr Ϸ 0.008 for the present case, is identified: at St p ജ St p,cr the core jet converges to the axis of rotation while at St p ജ St p,cr it does not. The characteristics of the turbulent flow in the near and intermediate regions are quite different and depend upon the magnitude of St p . The near-field region, x / d ഛ 10-15, is dominated by a regime of global precession of the entire jet. As a result, the large-scale entrainment of the ambient fluid is substantially enhanced while the fine-scale turbulent mixing is suppressed. Under the supercritical regime (i.e., St p ജ St p,cr ), the jet in the far field resembles some features of the nonprecessing counterpart. Nevertheless, significant differences still retain in the statistical properties.

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Section: Conditional Phase-averaged Statistics Of the Precessing Jmentioning

confidence: 82%

“…37), even though aspects of the underlying mechanisms may be different. The wake-like tail behind a jet in a cross flow contains a "vortex bubble."…”

Section: Conditional Phase-averaged Statistics Of the Precessing Jmentioning

confidence: 99%

Statistical analysis of the velocity field in a mechanical precessing jet flow

Nathan

2004

Physics of Fluids

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“…[42][43][44] However, the RANS simulations did not capture the flow unsteadiness also when running the full three-dimensional ͑3D͒ domain and perturbing the inlet conditions. Therefore, it seemed appropriate to assume a steadystate flow field and make use of a symmetry boundary condition along the domain center line.…”

Section: -3mentioning

confidence: 99%

Detailed flow physics of the supersonic jet interaction flow field

2009

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The supersonic jet interaction flow field generated by a sonic circular jet with a pressure ratio of 532 exhausting into a turbulent MACH 4.0 cross flow over a flat plate was investigated using numerical simulations. The simulations made use of the three-dimensional Reynolds-averaged Navier-Stokes ͑RANS͒ equations coupled with Wilcox's 1998 k-turbulence model. The numerical solution was validated with experimental data that include the pressure distribution on the flat plate, with an empirical formula for the height of the barrel shock, and with the Schlieren pictures showing the location and shape of the main shock formations. The simulations correctly captured the location and shape of the main flow features and compared favorably with the experimental pressure distribution on the flat plate. The validated numerical simulation was used to investigate in detail the flow physics. The flow field was found to be dominated by the shock formations and their coupling with the strong vortical structures. Three primary shock formations were observed: a barrel shock, a bow shock, and a separation-induced shock wave. While the general structure of the barrel shock was found to be similar to that of the underexpanded jet exhausting into a quiescent medium, two unique features distinguished the flow field: the concave indentation in the leeside of the recompression ͑barrel͒ shock and the folding of the windward side of the barrel shock due to an inner reflection line. The presence of the steep pressure gradients associated with the shocks creates strong vortical motions in the fluid. Six primary vortices were identified: ͑i͒ the well-known horseshoe vortex, ͑ii͒ an upper trailing vortex, ͑iii͒ two trailing vortices formed in the separation region and, aft of the bow shock wave, ͑iv͒ two more trailing vortices that eventually merge together into one single rotational motion. The low-pressure region aft of the injector was found to be generated by the combined effect of the concave indentation in the leeside of the barrel shock and the lower trailing vortices. The trailing vortices were found to be the main mechanism responsible for the mixing of the injectant with the freestream fluid.

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“…Basically there are four types of interrelated vortex structures (shown in Fig. 1), as pointed out by Fric,3,4 including the Horseshoe Vortices (HV), the Shear-Layer Vortices (SLV), the Wake Vortices (WV) and the Counter Rotating Vortices Pairs (CRVP), among which the CRVP behaves dominantly in the flow field. However, the creation of the CRVP has not been reached by researchers.…”

Section: Introductionmentioning

confidence: 99%

An experimental study of plasma aerodynamic actuation on a round jet in cross flow

Dai

Yang

et al. 2015

AIP Advances

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The present paper is performed on the effect of plasma aerodynamic actuation on a round jet in cross flow field with a low Reynolds number by using smoke visualization. The actuator is constituted by an electrode pair separated by a dielectric Al2O3 sheet. Several AC supply conditions are utilized. The experimental result shows a closing-in tendency of the jet flow toward the wall after being induced by plasma aerodynamic actuation, and such tendency is increasingly intensified as the actuation voltage increases. Numerical simulation is also performed. The simulation results show that an induced vortex pair is generated by plasma aerodynamic actuation near the wall flow field. The rotation direction of the induced vortex pair reverses against the counter-rotating vortex pair generated by a round jet in a cross flow without plasma aerodynamic actuation. Then the strength and structural size of the counter-rotating vortex pair are significantly reduced, resulting in the intensified near-wall effect of the jet flow. Three electrode-typed actuators (straight, 150°-elliptic arc and 180°-elliptic arc with the same streamwise extent) are placed at the exit of round jet to research the influence of electrode structure on jet in cross flow. The result shows that the longer the arc electrode surrounding the hole, the stronger the induced jet that flow near the wall is.

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Vortical structure in the wake of a transverse jet

Cited by 1,084 publications

References 9 publications

Statistical analysis of the velocity field in a mechanical precessing jet flow

Statistical analysis of the velocity field in a mechanical precessing jet flow

Detailed flow physics of the supersonic jet interaction flow field

An experimental study of plasma aerodynamic actuation on a round jet in cross flow

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