Circular turbulent wall jets in quiescent and coflowing surroundings

Kazemi, Mohammad; Khorsandi, Babak; Mydlarski, Laurent

doi:10.1063/5.0079921

Cited by 4 publications

(1 citation statement)

References 36 publications

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“…To ensure high signal-to-noise ratios of the measurements, it is necessary to mix suspended particles in the water. Typical particles used in previous studies, e.g., hollow glass spheres and talcum powder (Khorsandi et al, 2012;Moeini et al, 2020;Kazemi et al, 2022), may endanger the health of fish. Therefore, in the present study, low concentrations of chickpea flour were mixed with water, which did not remarkably influence…”

Section: Methodsmentioning

confidence: 99%

Effects of abundance, water temperature and light on the turbulence and mixing generated by fish schools of different sizes in quiescent water in a laboratory

Ahani

Khorsandi

2022

Front. Mar. Sci.

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The turbulence and mixing generated by schools of three fish species, namely koi, pangasius, and goldfish, were quantified in a series of controlled laboratory experiments. The effects of fish abundance, light, and water temperature on the turbulence parameters of the flow produced by the three fish species in a quiescent background were investigated by measuring the velocity field using acoustic Doppler velocimetry. It was observed that the turbulent flow was approximately homogeneous and isotropic and had low-mean velocities. The results show that increasing fish abundance and body size, dimming the ambient light, and increasing the water temperature increase the root-mean-square velocity, the integral time scale, and the rate of dissipation of turbulent kinetic energy. Consequently, fish abundance and body size, as well as environmental parameters, can influence fish-generated turbulence. To further quantify turbulent mixing, the dissipation rate, the mixing efficiency, and the vertical eddy diffusivity were extrapolated for the three fish species at their natural abundances. The dissipation rate of O(10-7-10-6) W/kg, the mixing efficiency of O(10-2-10-1), and the vertical eddy diffusivity of O(10-4) m2/s were estimated. These values are within the range of those of the physical sources. This demonstrates that the contribution of aquatic animals to the turbulent mixing of water environments may be significant, at least locally" to the end of the sentence so that it reads: "mixing of water environments may be significant, at least locally. Furthermore, the dissipation rate and eddy diffusivity are found to increase with the Reynolds numbers of aquatic species.

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Section: Methodsmentioning

confidence: 99%

Effects of abundance, water temperature and light on the turbulence and mixing generated by fish schools of different sizes in quiescent water in a laboratory

Ahani

Khorsandi

2022

Front. Mar. Sci.

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Evaluating acoustic Doppler velocimetry pulse-pair spacing/velocity range setting for turbulent flow measurements

Homayounfar

Khorsandi

2022

Physics of Fluids

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The velocity range, which is inversely proportional to acoustic pulse-pair spacing, is one of the most important user-set parameters of acoustic Doppler velocimeters (ADVs) and is expected to influence their flow measurements. An experimental study of the effect of the ADV velocity range on the mean and turbulence statistics measured in stagnant water, a turbulent channel flow, and a turbulent jet was undertaken. The results show that as long as the instantaneous velocities are within the user-set velocity range, increasing the velocity range does not noticeably influence the mean velocities, whereas it increases the velocity variances due to the increased noise variance. If the instantaneous velocities exceed the velocity range, phase wrapping occurs, resulting in underestimated mean velocities and overestimated velocity variances. The rate of increase in noise variance with the velocity range increases drastically as the turbulence level rises. From this, it can be inferred that in turbulence measurements, the contribution to the total noise made by Doppler noise is much more substantial than that of the sampling error. Furthermore, it is observed that for highly turbulent flows the ADV correlation significantly drops and signal quality reduces. Increasing the velocity range solves this problem at the expense of higher Doppler noise. Post-processing of the data effectively improves the statistics, even when the velocity range was set to overly high values. Finally, Doppler noise is found to be linearly related to velocity variances (at a constant velocity range), while it is nonlinearly proportional to the velocity range in measurements of turbulent flows.

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Effect of turbulent coflows on the dynamics of turbulent twin jets

Homayounfar,

Khorsandi,

Gaskin

2024

Physics of Fluids

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The impact of turbulent coflows on the dynamics of turbulent twin round jets is investigated experimentally. Parallel twin jets, at three jet spacing values and two Reynolds number/jet-to-coflow velocity ratios, were released into turbulent coflows with two distinct levels of turbulence intensity. Velocity measurements were made using acoustic Doppler velocimetry. An increase in the coflow turbulence intensity leads to an earlier merging and combining of the jets and also accelerates the rate of decay with downstream distance of the mean centerline excess velocity of the jets. The mean velocity on the symmetry line, for different values of jet spacing, ratios of jet exit velocity to coflow mean velocity, and coflow turbulence intensity, is self-similar when scaled by the maximum mean velocity on the symmetry line and the corresponding streamwise distance. Moreover, as the turbulence level of the coflow intensifies, the turbulence intensity along the symmetry line of the jets increases. The longitudinal integral length scale on the symmetry line of the twin jets decreases as the coflow turbulence intensity increases. The energy spectra of the coflowing twin jets show that the turbulence in the coflow transfers the energy contained by the larger scales to the smaller scales at a greater rate than that which occurs for jets in a quiescent background. However, as the jet spacing increases, less energy is transferred to the smaller scales.

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Circular turbulent wall jets in quiescent and coflowing surroundings

Cited by 4 publications

References 36 publications

Effects of abundance, water temperature and light on the turbulence and mixing generated by fish schools of different sizes in quiescent water in a laboratory

Effects of abundance, water temperature and light on the turbulence and mixing generated by fish schools of different sizes in quiescent water in a laboratory

Evaluating acoustic Doppler velocimetry pulse-pair spacing/velocity range setting for turbulent flow measurements

Effect of turbulent coflows on the dynamics of turbulent twin jets

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