On the flow structure of an inclined jet in crossflow at low velocity ratios

Dai, Chong; Jia, Lichao; Zhang, J.; Shu, Zheng; Mi, Jianchun

doi:10.1016/j.ijheatfluidflow.2015.12.001

Cited by 42 publications

(17 citation statements)

References 25 publications

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“…This new rescaling rule enables all the trajectories to collapse onto a typical profile, independent of the current speed parameter u r F, leading to an empirical closed-form expression as depicted in Equation (15). By proposing empirical expressions of x i , x t and z t , the new scaling approach become very practical and easily applicable to predict the trajectory of any dense jet, of u r F ranging between 0.2 and 1.1, vertically discharged into a flowing current.…”

Section: Discussionmentioning

confidence: 99%

“…Since all components of aquatic ecosystems are very sensitive to any water quality changes, a rapid and maximum dilution of the jet discharge within the ambient flow is a key solution to keep the ecosystem healthy and sustainable. Mixing of turbulent jets within surrounding environment was the topic of numerous experimental, analytical and numerical studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Turbulence Measurement of Vertical Dense Jets in Crossflow

Meftah

Mossa

2018

Water

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Turbulence measurement of a dense jet perpendicularly issued into a crossflow is investigated experimentally. The flow-velocity components were extensively measured with a high frequency Acoustic Doppler Velocimeter (ADV) system, whereas, a Micro Scale Conductivity Temperature instrument was used to measure the jet salinity. Special attention is given to understand the jet flow-structures in the flow symmetry plane. The flow velocity-fields, the jet trajectory, the turbulence intensities, the turbulent kinetic energy, the turbulent length scales, and the dispersion coefficients have been analyzed. The flow velocity-fields show that the dense jet is characterized by two distinct regions: an ascending region, of jet-like mixing, and a descending region of plume-like mixing. In this study, a new scaling approach of the jet trajectories, based on the jet characteristic length scales, is proposed, leading to an empirical closed-form expression to predict the jet trajectory. The turbulence analysis shows that the jet is accompanied by high levels of flow-turbulence intensities and large kinetic energy production. The results of the turbulent length scales indicate that the ambient flow-field, without jet effect, is an isotropic process. However, in the jet flow-field, a significant spatial-variation of the turbulent length scales was observed, indicating an anisotropic process. The trends of the dispersion coefficients follow those of the turbulent length scales. In comparison with the ambient flow, the jet flow-field shows a decrease of the longitudinal dispersion coefficient and an increase of the vertical one, leading to the increase of the jet width.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Turbulence Measurement of Vertical Dense Jets in Crossflow

Meftah

Mossa

2018

Water

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“…A transition to detached jet structure was noticed with occurrence of ring vortices as blowing ratio was increased. Dai et al 23 demonstrated appearance of inverse hairpins, which were genesis of coherent structures within the port. Furthermore, hole shapes and its boundary layer vorticity have an immense influence to the kidney vortices developed downstream affecting the jet liftoff.…”

Section: Introductionmentioning

confidence: 99%

Flow structures and thermal field with modulated jet near the semi-circular leading edge

Sarkar

2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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Influence of external modulation on unsteady flow and heat transfer near the leading edge of a constant thickness aerofoil has been described through large eddy simulation. This is a simplified approach to study film cooling activities near the leading edge of a turbine blade. Discrete jets, which are forced at a Strouhal number (St) of 0.37 with an averaged blowing ratio of unity, are ejected normally from a series of film cooling holes to a separated boundary layer. The results are compared against the corresponding steady injection. Larger coherent structures appear for a forced jet with an augmented vortex dynamics resulting in high jet lift-off, earlier break down, enhanced mixing with the cross flow and dilution of coolant layer. Resolved hairpins, which are the signature of coherent structures, illustrate that the vorticity and thermal field are highly correlated. Furthermore, evolution of hairpins and their advection control scalar transport and mixing. In brief, the modulation of coolant jet near the leading edge appears not beneficial for the combination of blowing ratio and frequency considered here.

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“…However, a majority of the prior research on synthetic jets in cross flow has been made on the synthetic jets on a planar surface (for instance, Dai et al 2016, Wen et al 2018. To our best knowledge, very few reports discuss the behavior of a synthetic jet mounted on a curved torpedo-like surface particularly at high velocity ratios, which may be of great interest for its potential utility in naval or other applications.…”

Section: Introductionmentioning

confidence: 99%

Implications of Velocity Ratio on the Characteristics of a Circular Synthetic Jet Flush Mounted on a Torpedo Model in Quiescent and Cross-Flow Conditions

Kumar

Saha

Panigrahi

et al. 2020

JAFM

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A high velocity ratio synthetic jet on an arched surface is of great interest for its potential applications in navy, including torpedo. However, in spite of detailed research on synthetic jets over a flat surface in cross-flow, very few observations have been made on synthetic jets over a surface which is shaped like a torpedo. This study experimentally explores a synthetic jet mounted on a torpedo shaped model in quiescent and cross-flow conditions. Initially, the synthetic jet is characterized for two different diaphragm displacements and at four distinct actuation frequencies in the range of 1 Hz-6 Hz in a quiescent flow environment. Subsequently, in cross flow, similar study is conducted for three cross-flow velocities ranging from 7.2-32 cm/s, at a fixed amplitude of diaphragm oscillations. The measurements are carried out using Laser Induced Fluorescence (LIF) and Laser Doppler Velocimetry (LDV) and the qualitative LIF visualizations are corroborated by the quantitative LDV data. These results indicate that the synthetic jet vortex rings can be grouped as stretched vortex rings and distorted tilted vortex rings. The flow structures primarily depend on the velocity ratio, which is function of cross-flow velocity and frequency of actuation. The flow physics in case of a curved torpedo surface is slightly different as compared to the synthetic jet on a flat surface.

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On the flow structure of an inclined jet in crossflow at low velocity ratios

Cited by 42 publications

References 25 publications

Turbulence Measurement of Vertical Dense Jets in Crossflow

Turbulence Measurement of Vertical Dense Jets in Crossflow

Flow structures and thermal field with modulated jet near the semi-circular leading edge

Implications of Velocity Ratio on the Characteristics of a Circular Synthetic Jet Flush Mounted on a Torpedo Model in Quiescent and Cross-Flow Conditions

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