Concentration field of multiple circular turbulent jets

Hodgson, John; Moawad, Ahmed K.; Rajaratnam, N.

doi:10.1080/00221689909498309

Cited by 23 publications

(20 citation statements)

References 4 publications

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“…Scalar fields have been measured in multiple plane jets (Grandmaison & Zettler 1989) and multiple round jets (Hodgson, Moawad & Rajaratnam 1999;Wang & Davidson 2003). Stapountzis et al (1992) studied the reaction product of two scalars emitted from parallel jets, but did not quantify the reactant fields themselves.…”

Section: Probability Distributionsmentioning

confidence: 99%

Joint probabilities and mixing of isolated scalars emitted from parallel jets

Soltys

Crimaldi

2015

J. Fluid Mech.

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Mixing and reaction between two scalars initially separated by scalar-free ambient fluid is important in problems ranging from ecology to engineering. Using a two-channel planar laser-induced fluorescence (PLIF) system the instantaneous spatial structure of two independent scalars emitted from parallel jets into a slow coflow is quantified. Of particular interest is the scalar covariance used to define the correlation coefficient. Joint probability distribution functions (JPDFs) and instantaneous images of the scalar fields demonstrate that initially the flow mainly consists of incursions of fluid from one jet into the other, and vice versa, before scalars have time to assemble in attracting regions of the flow and coalesce due to diffusive flux. Decomposing the joint probability distribution exhibits the effect these events have on scaler overlap and scalar covariance. Along the centreline near where the mean profiles of the jets meet, the scalar covariance is negative; however, the covariance becomes positive as the scalars converge in shared structure and diffusive flux bridges a reduced barrier of ambient fluid. The mixing path between scalar filaments can be probabilistically observed through the conditional diffusion of the two scalars at various points in the flow.

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Section: Probability Distributionsmentioning

confidence: 99%

Joint probabilities and mixing of isolated scalars emitted from parallel jets

Soltys

Crimaldi

2015

J. Fluid Mech.

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“…This result shows that the centreline dilution of a long diffuser obtained Fig. 8 AIM prediction of the centreline variation of the mean concentration of three interacting vertical round jets in series compared to SM prediction and experimental data [6] at large axial distances remains 11.4% less than the corresponding dilution of an equivalent plane jet. This result justification is again attributed to the 6.4% entrainment reduction of a round jet compared to the plane jet entrainment.…”

Section: Comparisons With Data and Discussionmentioning

confidence: 59%

“…Data show that AIM predicts very well the ratios Lw m N and Lc m N for short linear diffusers with a small number of nozzles, since the values of the correlation coefficient approach to unity, indicating the existence of a strong linear correlation among the data predicted and the data measured. AIM verification can also be made for jets using the concentration measurements by Hodgson et al [6], concerning three round turbulent jets (N = 3) with Reynolds number 4,900. Water was used as the jet and ambient fluid, while a dye solution as tracer.…”

Section: Comparisons With Data and Discussionmentioning

confidence: 99%

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Advanced integral model for groups of interacting round turbulent buoyant jets

Yannopoulos

2010

Environ Fluid Mech

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An integral model that combines all advantages of Superposition Method (SM), Entrainment Restriction Approach (ERA) and Second Order Approach (SOA) is proposed to predict the mean axial velocity and concentration fields of a group of N interacting vertical round turbulent buoyant jets. SM is successful in predicting the fields of mean axial velocity and mean concentration for a group of N interacting jets or plumes and ERA is advantageous in predicting the above fields for either two or large number (N → ∞) of interacting buoyant jets in the whole range of buoyancy. SOA takes into consideration in a dynamic way the turbulent contribution to the momentum and buoyancy fluxes and provides better accuracy than the usual procedures. A novelty of the proposed model is the production and utilisation of advanced profile distributions, convenient for the mean axial velocities and concentrations in a cross-section of the entire group of buoyant jets. These profiles are developed on the basis of flux conservation of momentum, buoyancy and kinetic energy for the mean motion. They enhance dynamic adaptation of the individual buoyant jet axes to the group centreline. Due to these profile distributions, the present model owns generality of application and better accuracy of predictions compared to usual integral models using simple Gaussian or top-hat profiles; thus it conferred the name Advanced Integral Model (AIM). AIM is herein applied to predict the mean flow properties of two different arrangement types of any number of buoyant jets: (a) linear diffusers and (b) rosette-type risers. Present results are compared to available experimental data and traditional solutions based on Gaussian profiles. Findings may be useful for design purposes and environmental impact assessment.

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“…However, the variations of the proportional relationship are minimal when the primary air velocity is in a certain extent. According to the literature [21,22], for the jet flow blown from the nozzle, when the primary air flow rate achieves a certain amount defined as the characteristic primary air flow rate in this paper, the induction ratio will remain constant. To achieve the stable induction ratio, we utilized the relatively high airflow rate.…”

Section: Resultsmentioning

confidence: 99%

Experimental and Numerical Study of the Radiant Induction-Unit and the Induction Radiant Air-Conditioning System

Zhang

2016

Energies

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Abstract:In this paper we proposed the novel air-conditioning system which combined induction ventilation and radiant air-conditioning. The indoor terminal device is the radiant induction-unit (RIDU). The RIDU is the induction unit combined with the pore radiant panel on which the copper pipes with rigid aluminum diffusion fins are installed. The two-stage evaporator chiller with the non-azeotropic mixture refrigerant is utilized in the system to reduce the initial investment in equipment. With the performance test and the steady state heat transfer model based on the theory of radiative heat transfer, the relationship between the induction ratio of the RIDU and the characteristic of the air supply was studied. Based on this, it is verified that the RIDU has a lower dew-point temperature and better anti-condensation performance than a traditional plate-type radiant panel. The characteristics of the radiation and convection heat transfer of the RIDU were studied. The total heat exchange of the RIDU can be 16.5% greater than that of the traditional plate-type radiant terminal.

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Concentration field of multiple circular turbulent jets

Cited by 23 publications

References 4 publications

Joint probabilities and mixing of isolated scalars emitted from parallel jets

Joint probabilities and mixing of isolated scalars emitted from parallel jets

Advanced integral model for groups of interacting round turbulent buoyant jets

Experimental and Numerical Study of the Radiant Induction-Unit and the Induction Radiant Air-Conditioning System

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